Thursday, 21 November 2013

The F1000 Scientific Community

It is a great thing that so much amazing scientific research is being done right now in the world. Those elegant studies that have developed into interesting stories that expand our knowledge of science are a joy to read. These often feature in the "top" journals and may make headlines (hopefully written up within a useful context). There are other hidden gems that may not immediately jump out, but on further reading reveal a crucial piece of information that helps with your own research puzzle, or provides a protocol that allows you to do something you didn't realize was possible. Basically there is a lot of science written and published by an ever increasing number of journals, the trouble is prioritizing what to read!

How to keep abreast of the most exciting research in your field? RSS feeds and pub med/Google scholar searches are fine if you are very specific about what you search for but you still need to make a decision about what terms to look for or which journals to follow. On the first day of my PhD I was given the group's "Journal Watch" list, a many times photocopied sheet of paper with 20 or so journal TOCs and AOPs to check regularly. Email alerts for these journals can be useful but you still have to trawl through the table of contents, that is if the email doesn't get inadvertently junked or skipped over. Review articles and perspectives are brilliant for guiding you towards excellent primary articles, but only if you are looking for at a specific gene, pathway, disease etc.

During my PhD I was very lucky to be able to write with my supervisor as an associate faculty member of the Faculty of 1000 (F1000). For this we wrote short pieces highlighting exciting developments in the field of Leukocyte Activation. This F1000 Prime service is an excellent way to be alerted to articles that are not just published in high impact journals, but those that are having a real impact on researchers post peer-review. Articles are selected by faculty members and rated for their contribution to the field (with a metric value to match), this ensures you can see the best recommended papers easily. A personalised homepage and email alerts can be tailored to your key words. I found this service immensely useful during my PhD and enjoyed writing for F1000 so much that I started this blog, albeit with a focus on open access articles and better explanations for non-scientists.

So I was excited when I saw a netoworking event in London organised by the F1000 to meet with staff and users of the service. There was a lively discussion about reaearch, open access publishing, scientific communication and data metrics. It was during this event that I discovered I could continue my passion for F1000 as a specialist, explaining and promoting their services including F1000 prime, which I was familiar with from use during my PhD, as well as F1000 Posters, F1000 Trials and F1000 Research. So I have once again joined the F1000 community (see the great new badge on the left of my blog), and I am keener than ever to help F1000 grow and to communicate the exciting advances in disseminating research where it matters! I am currently trialling a new Journal club feature of the F1000 website, so expect more about how this goes very soon!

Monday, 14 October 2013

Resistance to the leukemia treatment Imatinib can lay dormant and affect future treatment options

Normal cells that form the tissues of our body can be transformed into cancer by mutations within multiple genes that tell the cells how to behave. Mutations can come about in a number of different ways. Small changes in how a gene codes for just one of the amino acids that make up a protein can completely alter the activity of a protein. For example, KRas is a signalling protein with normally undergoes cyclical turning on and off when the cell needs it to help with growth, however a mutated active form a KRas cannot be turned off and goes on to allow cells to grow almost uncontrolled. Larger changes to genes may also occur with whole genes lost or moved around in the DNA. In fact in cancer cells DNA can become very messy!

A very important and well known mutation that was discovered in a leukaemia called chronic myelogenous leukemia (CML) is called the "Philadelphia Chromosome". This occurs when two large structures of DNA called chromosomes (humans have 23 pairs of chromosomes in each cell) swap small pieces; part of chromosome 9 is swapped with part of chromosome 22 making the former longer and the latter shorter. This new chromosome 22 is what is known as the "Philadelphia Chromosome". As a consequence, two genes BCR and ABL, which are not normally associated at the DNA level, become fused together to form the oncogene BCR-ABL. As an oncogene, BCR-ABL is crucial in driving cancer, it is most commonly associated with CML and other leukemias.

Many drugs for treating and managing cancer involve targeting a gene in cancer cells which is either found at a higher level or only slightly modified; because BCR-ABL is a completely different gene that is only found in cancer cells it was an attractive target for drug development. Indeed, an inhibitor of BCR-ABL called Imatinib/Gleevec has been immensely successful in treating CML. A number of patients respond well at first, but their cancer cells acquire a resistance to Imatinib; this occurs because the BCR-ABL protein becomes further mutated. Doctors can switch to using other BCR-ABL inhibitors such as Nilotinib/Tasigna, however some mutations in BCR-ABL also confer resistance to Nilotinib as well. 

A recent study in the British Cancer Journal found that mutations in BCR-ABL that become undetectable following treatment with Imatinib, can reemerge years later after treatment is changed to Nilotinib. This occurs in part due to a process called clonal expansion. A mutation which gives a cancer cell a growth or survival advantage compared to other cells within a tumour can be expanded, as these cells take over to form the bulk of the tumour.

It is therefore even more important for doctors to check which mutations of BCR-ABL are present in cancer cells when choosing treatment options, to prevent reemergence of mutations that will make cancer cells resistant.

Mentioned Articles

Parker WT, Yeoman AL, Jamison BA, Yeung DT, Scott HS, Hughes TP, Branford S.
Br J Cancer. 2013 Sep 17;109(6):1593-8. doi: 10.1038/bjc.2013.318

Cancer Research UK: Imatinib (Glivec)

Cancer Research UK: Nilotinib (Tasigna)

Sunday, 13 October 2013

Claudin 1 is a driver of EMT in primary liver cancer

Cancer of liver cells (hepatocellular carcinoma) is often diagnosed late as it may grow slowly and for unnoticed for years; consequently most patients present with advanced disease, the outlook for which is currently very poor. The process of epithelial to mesenchymal transition (EMT), which is required for many cancers to undergo metastasis and set up secondary tumours in other organs and tissues, occurs in advanced disease and in the case of liver cancer very little is known about EMT.

A recent study published in the journal Oncogene shows that a molecule that is normally involved in holding epithelial cells together in tissues, Claudin 1, can in fact promote EMT and allow cancer cells to become more invasive. Increased levels of Claudin 1 in liver cancer cells causes promotion of genes involved in EMT through up-regulation of key transcription factors ZEB1 and SLUG. Another important EMT transcription factor, SNAIL, was shown to not be involved, but interestingly a protein called c-Abl was found to be very important for this process.

c-Abl, is best known for being part of a mutation that occurs commonly in a form of leukaemia called CML and a number of drugs targeting c-Abl have been developed to treat CML. For example, Imatinib (Glivec) is an inhibitor that blocks the BCR-Abl fusion oncogene product which has been very useful for doctors  treating CML. In this present study, the group showed that by silencing the protein c-Abl in cells that have Claudin 1 over-expressed, they could reverse the up-regulation of ZEB1 and SLUG and prevent the invasiveness conveyed by EMT. This study demonstrates that in the future when doctors look at hepatocellular carcinoma they could look for increased levels of Claudin 1 as a possible indicator of the invasiveness of the cancer. With more work, this marker could be validated and possibly even exploited as a druggable target for the treatment of liver cancer.

Mentioned Articles

Suh Y, Yoon CH, Kim RK, Lim EJ, Oh YS, Hwang SG, An S, Yoon G, Gye MC, Yi JM, Kim MJ, Lee SJ.

Oncogene. 2013 Oct 10;32(41):4873-4882. doi: 10.1038/onc.2012.505.

Tuesday, 18 June 2013

Brief: A test for potentially harmful human induced pluripotent stem cells

Yamashita et al. have produced a method for determining if human induced pluripotent stem cells (iPSC) are likely to form tumours and published their results in Scientific Reports.

Taking a patient's cells, engineering them to gain stem cell properties, such as being able to self-renew and develop into multiple different cell types, and re-injecting them into that patient's tissue is an emerging new therapeutic field. However there are concerns that these cells, once transplanted into a patient, may become cancerous. The methods used to make human iPSCs often involves making normal cells express stem cell factors (which in themselves can be oncogenic - cancer forming) and the oncogene c-myc.

By making these iPSCs into cartilage and monitoring for the formation of tumours, the group could see which iPSCs were potentially harmful. This test could prove crucial in validating iPSCs for regenerative medicine.

Mentioned Articles

Yamashita A, Liu S, Woltjen K, Thomas B, Meng G, Hotta A, Takahashi K, Ellis J, Yamanaka S, Rancourt DE.
Sci Rep. 2013 Jun 13;3:1978. doi: 10.1038/srep01978.

Sunday, 16 June 2013

Micro-RNAs and Retinoic Acid take their Toll on prostate and breast cancer

One of the first lines of defence against infection is the innate immune system. This mounts a non-specific response to infectious agents including bacteria and viruses. Recognition of bacterial and viral components is accomplished by a family of receptors called Toll Like Receptors (TLRs) found on the surface of innate immune cells. TLRs can also be expressed by other cells such as cancer cells.

Previous studies have shown that activation of TLRs can affect the levels of micro RNAs (miRNAs) in cells and therefore regulate which proteins are expressed (I have mentioned the role of miRNAs in cancer in previous posts). In this present study, Galli et al. found that activation of TLR3 in prostate and breast cancer cells caused an increase in four miRNAs. These miRNAs target a class of proteins called DNA methyltransferases, resulting in the loss these proteins from the cancer cells. Without these DNA methyltransferases a protein called retinoic acid receptor beta (RARβ) is produced by the cancer cells.

In a breakthrough, the group showed that drugging tumours first with an activator of TLR3 followed by retinoic acid (an activator of RARβ), caused tumours to be smaller compared to control treated tumours. This study therefore presents promising pre-clinical data for the treatment of breast and prostate cancer with this exciting combination therapy.

Mentioned Articles

Galli R, Paone A, Fabbri M, Zanesi N, Calore F, Cascione L, Acunzo M, Stoppacciaro A, Tubaro A, Lovat F, Gasparini P, Fadda P, Alder H, Volinia S, Filippini A, Ziparo E, Riccioli A, Croce CM.
Proc Natl Acad Sci U S A. 2013 Jun 11;110(24):9812-7. doi: 10.1073/pnas.1304610110. Epub 2013 May 28.

Chen R, Alvero AB, Silasi DA, Steffensen KD, Mor G.

Oncogene. 2008 Jan 7;27(2):225-33. doi: 10.1038/sj.onc.1210907.

Friday, 14 June 2013

Researchers hot on the TRAIL of new combination therapy for glioblastoma

Some cancers are particularly difficult to treat, particularly brain tumours. Glioblastoma is an aggressive form of cancer in the brain which, although responds initially to treatment, is refractory and often always fatal. Treating cancerous cells with a protein called TRAIL is a specific treatment which causes cancer cell death in around 50% of cancer cell lines. Bagci-Onder et al. employ some interesting molecular techniques to studying the effect of TRAIL on glioblastoma cell viability.

Neuronal stem cells were used to deliver soluble TRAIL protein to glioblastoma cells and the way in which this happens was modelled by artificially colouring both cell types and watching their interactions when grown together. Two out of three glioblastoma cell lines tested were sensitive to TRAIL treatment and underwent a form of highly controlled cell death called apoptosis.

The killing of these cells by TRAIL treatment was dependent on the levels of two proteins on the cell surface called death receptors; death receptor 4 (DR4) and death receptor (DR5). The group observed that the higher the levels of these receptors, the more receptive to TRAIL treatment the cells were. This led the group to postulate that increasing death receptor expression could enhance the effectiveness of TRAIL in treating glioblastoma.

To see how they could increase death receptor expression in cancerous cells, the group used a panel of different drugs known to affect the way cells function. They found that targeting histone deacetylases (HDACs) [see previous post] with a drug called MS-275 caused an increase in death receptor levels at the surface of cells. As expected, this also led to an increased sensitivity to TRAIL treatment. Importantly, the one glioblastoma cell line which was initially resistant to TRAIL treatment became sensitive to the killing power of TRAIL if cells were also treated with MS-275. This study highlights a potential new combination treatment for glioblastoma.

Mentioned Articles

Bagci-Onder T, Agarwal A, Flusberg D, Wanningen S, Sorger P, Shah K.

Oncogene. 2013 Jun 6;32(23):2818-27. doi: 10.1038/onc.2012.304. Epub 2012 Jul 23.

"Types of primary brain tumours : Cancer Research UK : CancerHelp UK." Cancer Research UK: the UK's leading cancer charity : Cancer Research UK . N.p., n.d. Web. 13 June 2013. 

Friday, 19 April 2013

Integral role for Pyk2 in breast tumour outgrowth and metastasis to the lung

There exist a number of well-defined markers of the epithelial to mesenchymal transition (EMT), a process crucial for the outgrowth of tumours to new areas of the body (metastasis), and now a signalling protein Pyk2 has been welcomed into the fold.

Focal Adhesion Kinase (FAK) is an established regulator of EMT in response to the pro-EMT signalling protein Tumour Growth Factor Beta (TGFβ), a recent study has revealed that some of FAK’s functions also require Pyk2 and suggests important roles for Pyk2 in tumour metastasis. A previous study by Sun et al. from The University of Hong Kong has also described a role for Pyk2 in driving EMT in liver cancer (hepatocellular carcinoma).

Normal human breast cells transformed to be cancer-like and cells from patients with aggressive (invasive ductal cell carcinoma, with reaccurance after 5 years) show high levels of Pyk2 protein. One breast cancer cell line is a mixture of less aggressive and more aggressive cancer cells, within these different cell populations the group observed vastly different levels of Pyk2 protein.

This increased Pyk2 expression was associated with increased growth of cells in a three dimensional tumour-like environment. In fact, growth of cells in this 3D model can enhance Pyk2 expression in breast cancer cell lines in a manner that is independent of the pro-EMT factor TGFβ. When growing two dimensionally (i.e. on a plastic culture surface) breast cancer cells show low levels of Pyk2, however treatment TGFβ could increase Pyk2 levels, but not to the same extent as observed in the 3D model. The group suggest that the 3D model exhibits autocrine TGFβ signalling (where TGFβ released by one cell acts directly upon the same cell). Importantly, not only do the cells make more Pyk2, but there are higher levels of the active form of Pyk2 (phosphorylated Pyk2). The signalling mechanism which links TGFβ to the increased Py2k levels observed was shown to involve the actions of a transcription factor called Smad4, this pathway was observed clearest in aggressive breast cancer cells.

Metastasis requires a dramatic change in the shape of cells (a novel mechanism of this was previously described in a past post); the classical EMT shape change is induced by TGFβ, however this was independent of Pyk2. It appears that FAK is the key protein involved here.

The group went on to show that whilst up-regulation of Pyk2 in breast cancer cells is required along with FAK for acquisition of an EMT signature, Pyk2 alone is indispensable for their ability to outgrow their initial “primary” tumour site and metastasise to the lung. Pyk2 could therefore present a therapeutic target for the treatment of invasive, pre-metastatic breast cancer.

Mentioned Articles

Wendt MK, Schiemann BJ, Parvani JG, Lee YH, Kang Y, Schiemann WP.
Oncogene. 2012 Jun 18. doi: 10.1038/onc.2012.230. [Epub ahead of print]

Sun CK, Ng KT, Lim ZX, Cheng Q, Lo CM, Poon RT, Man K, Wong N, Fan ST.
PLoS One. 2011 Apr 20;6(4):e18878. doi: 10.1371/journal.pone.0018878.

Wednesday, 17 April 2013

A novel protein, UCH-L1, regulates the balance of two mTOR protein complexes; potential implications for neurological diseases and cancer

The signaling protein mTOR was first identified as the target of a natural chemical called Rapamycin and so named mammalian Target Of Rapamycin. mTOR can form two distinct complexes called mTORC1 and mTORC2; the two main mTOR binding proteins in these complexes are Raptor (mTORC1) and Rictor (mTORC2). In addition, several other proteins have been shown to associate with these complexes, for a review see this paper.


The mTORC1 complex activates S6K-1 and elF4E, two proteins required for the process of translating the messenger RNA of a gene into the protein via the assembly of amino acids specifically recruited by transfer RNA (tRNA). Increased mTORC1 activity can therefore lead to increased protein synthesis, important for bringing about dramatic cellular changes such as transformation from normal to cancerous states.


The mTORC2 complex, on the other hand, is responsible for activating proteins including: Akt, SGK-1 and PKCalpha which are involved in overall activation and proliferation of cells including those of the immune system. Cancerous cells often show increased Akt activation and this can be either through enhancing mutations in Akt itself or increased activity of Akt activating signaling pathways such as the mTOR pathway.
Since the discovery of Rapamycin, there have been a plethora of drugs developed which target either both mTOCR1, mTORC2 or both complexes. Some of these drugs have even been approved for the treatment of cancer, or are currently progressing through the later stages of clinical trials. However, the processes regulating the shift between mTORC1 and mTORC2 signaling are relatively poorly understood. A recent study by a group from Minnesota in the USA reveals a mechanism by which cells can move mTOR signaling from protein synthesis (mTORC1) to proliferation (mTORC2).

The ubiquitin hydrolase, UCH-L1, was the focus of a recent study as it was found that this protein interrupts mTORC1 signaling, high levels of UCH-L1 were associated with low levels of mTORC1 activity. UCH-L1 does this by displacing a novel mTORC1 interaction partner, namely the DDB1-CUL4 complex, identified in a previous study. This finding is very important because mutations of UCH-L1 have been seen in Parkinson’s disease, and UCH-L1 may also be involved in other brain disorders in which therapeutic inhibition of mTOR is already being investigated. Because of the well known role of mTOR in cancer, UCH-L1 also presents an exciting mechanism for cancer researchers.

Mentioned Articles

Ghosh P, Wu M, Zhang H, Sun H.
Cell Cycle. 2008 Feb 1;7(3):373-81. Epub 2007 Nov 2

Hussain S, Feldman AL, Das C, Ziesmer SC, Ansell SM, Galardy PJ.
Mol Cell Biol. 2013 Mar;33(6):1188-97. doi: 10.1128/MCB.01389-12. Epub 2013 Jan 7.

Wander SA, Hennessy BT, Slingerland JM.
Next-generation mTOR inhibitors in clinical oncology: how pathway complexity informs therapeutic strategy.
J Clin Invest. 2011 Apr;121(4):1231-41. doi: 10.1172/JCI44145. Epub 2011 Apr 1.

Weber JD, Gutmann DH.
Cell Cycle. 2012 Jan 15;11(2):236-48. doi: 10.4161/cc.11.2.19022. Epub 2012 Jan 15.

Monday, 1 April 2013

miR-21 is an "oncomir" important for skin cancer progression

An exciting new study shows that a microRNA called miR-21 acts as an oncogene to promote squamous cell carcinoma of the skin, and its up-regulation is dependent on reduced expression of the transcription factor Grhl3.

MicroRNAs were previously introduced here using the Let7 family as an example. Many different microRNAs are down- or up-regulated in tumour cells and can act as tumour suppressors or oncogenes  Oncogenic miRNAs (oncomirs) are attractive targets for therapeutic intervention as therapeutics can be developed to inhibit their function. A group from the University of California in Irvine CA, USA looked at the epidermis of mice which have the transcription factor Grhl3 genetically deleted. They observed a significant change in a number of microRNAs (Table 1), interestingly three of these were up-regulated 2 fold or more. miR-21, up-regulated to the greatest extent (2.5 +/- 0.6 fold increase), was one of the first oncomirs to be discovered and many of the proteins that it targets for degradation are tumour suppressors. Enforced loss of Grhl3 clearly led to a significant increase in miR-21 expression in the mouse model and importantly in isolated normal human epidermal keratinocytes, the main cell types in the human epidermis.

The group then showed that Grhl3 directly binds to the region of DNA that precedes miR-21, this region normally acts to promote the expression of for miR-21, however Grhl3 binding prevents the function of the miR-21 promoter. Therefore, loss of Grhl3 would remove this promoter repression and allow for the increased miR-21 expression as observed in Grhl3 deficient mice.

Short RNA sequences called antagomirs can be used to inhibit miRNAs including miR-21. When mice were treated with an miR-21 antagomir, reduced miR-21 expression was observed. The group next investigated which genes are targeted by miR-21 a cell line representative of human keratinocytes and karatinocyte tumour cells. These included tumour-suppressor genes involved in the cell cycle such as Cdk6 and Cdc25, and a protein responsible for repairing damaged DNA called Msh2 that is frequently mutated in cancer. 

The effect of miR-21 on these genes was more significant when kerantinocytes were transformed into tumourous cells. The group observed that transformation of kerantinocytes also caused down-regulation of a protein called DND1, DND1 it turns out is a negative regulator of the function of miR-21. Artificial over-expression of DND1 in transformed keratinocytes prevents miR-21 induced down-regulation of Msh2. Conversely, an artificial decrease in DND1 expression caused an enhancement of miR-21 induced Msh2 down-regulation.

The importance of Grhl3 and Msh2 in the progression of skin cancer was highlighted when the group investigated the ability of keratinocytes lacking Grhl3 to form tumours in mice. Loss of Grhl3 caused an increase in tumour volume an importantly was associated with loss of Msh2, showing the importance of this new epidermal regulatory pathway in skin cancer.

Mentioned Articles

Bhandari A, Gordon W, Dizon D, Hopkin AS, Gordon E, Yu Z, Andersen B. (2013)
Oncogene. 2013 Mar 21;32(12):1497-507. doi: 10.1038/onc.2012.168. Epub 2012 May 21.

Stenvang J, Petri A, Lindow M, Obad S, Kauppinen S.
Silence. 2012 Jan 9;3(1):1. doi: 10.1186/1758-907X-3-1.

Martin SA, Lord CJ, Ashworth A.
Clin Cancer Res. 2010 Nov 1;16(21):5107-13. doi: 10.1158/1078-0432.CCR-10-0821. Epub 2010 Sep 7.

Saturday, 9 February 2013

A new selective inhibitor of Histone Deacetylase 6

Chemotherapy, treatment of cancer with drugs, requires the development of compounds which have the effect of slowing tumour growth, stopping growth all together or even causing death to cancer cells within the tumour. Generally, compounds can either act to positively stimulate a response within cells or to inhibit one or more processes. These compounds will normally be designed to target a single protein or multiple proteins in the same family. There are advantages and disadvantages to targeting more than one protein: on the plus side you may help kill cancer cells by stopping several proteins in the same signalling pathway or prevent more than one pathway, on the downside you can increase the chance that the compound will also target non-cancerous cells and increase side effects for patients. One way to lessen this effect is to try and specifically target the compound to only the tumour thus limiting its effects on surrounding healthy cells, an alternative is to make the compound more specific for its intended target and reduce off-target effects. Compounds that not only show these properties, but also enter the body easily, are absorbed at a desirable rate and are successfully cleared from the body without creating dangerous metabolites, are likely to make suitable drugs. Here is where the fields of drug design, pharmacology and cancer research combine in an attempt make more effective therapeutic agents for the treatment of cancer.

Drug development can take several approaches, firstly there are a number of compounds that exist in nature such as the anti-cancer drug Taxol which was found in the Pacific Yew tree Taxus brevifolia in the late 1960s. Often, but not always, chemists can find ways to make these natural products from reactions between other chemicals, increasing the amount of drug that can be produced from these sometimes rare natural products. Additionally, once the chemical structure of these natural products is known, medicinal chemists can make small changes to a compound's structure and look to see what effect this has on the anti-cancer activity of the resulting compounds, this is called structure activity relationship (SAR). These methods are the usual route of drug discovery by academic groups, however in the pharmaceutical industry vast libraries of compounds which have drug-like properties are screened for interactions with desired target proteins, or their ability to stop cancer cell growth. This effort is called high throughput screening (HTS), it is expensive but often finds compounds which can undergo SAR to finally produce potential drugs.

Kaliszcak and colleagues recently developed an anti-cancer drug based on two natural inhibitors of a class of proteins called histone deacetylases (HDACs). I mentioned in a previous post that DNA is tightly held together in a structure called chromatin, to build chromatin DNA is wound around proteins called histones. These histones can be modified by adding acetyl groups which loosens the chromatin structure making DNA more accessible, HDACs can remove these acetyl groups causing DNA to become more tightly wound and inaccessible. HDACs also target proteins other than histones for deacetylation such as alpha-tubulin, a protein involved in the cell cycle that can be acetylated. The HDAC6 inhibitor prevented the deacetylation of alpha-tubulin by HDAC6 and caused an increase in the levels of the acetylated form. This effect on alpha-tubulin makes inhibiting HDACs, including HDAC6, a potential treatment for cancer. However, many current HDAC inhibitors are very unspecific and have serious side effects. The inhibitor developed by Kaloszcak and colleagues targets HDAC6 but at much lower concentrations of drug than required to target other HDACs such as HDAC1, suggesting it is more selective for HDAC6. This inhibitor had potent anti-cancer effects, causing a reduction in the growth of a wide variety of cancer cell types including: breast, colon, lung, ovarian and prostate cancer. 

The group also showed that their HDAC6 inhibitor caused cancer cells to undergo cell death. They did this by measuring the DNA content of cells after treatment with their HDAC6 inhibitor; DNA content decreased, a sign that cells are undergoing cell death. They noticed that proteins called caspases, important in a specific type of controlled cell death called apoptosis, were increased. Finally, when used in a mouse model of cancer, these inhibitors worked to reduce tumour growth with no general toxicity suggesting this HDAC6 inhibitor may do well if transferred into human clinical trials. 

Mentioned Articles

Kaliszczak M, Trousil S, Aberg O, Perumal M, Nguyen QD, Aboagye EO. (2013)
Br J Cancer. 2013 Feb 5;108(2):342-50. doi: 10.1038/bjc.2012.576. Epub 2013 Jan 15. (2009) Paclitaxel (Taxol) : Cancer Research UK : CancerHelp UK. [online] Available at: [Accessed: 9 Feb 2013].

Aldana-Masangkay GI, Sakamoto KM.(2011)
J Biomed Biotechnol. 2011;2011:875824. doi: 10.1155/2011/875824. Epub 2010 Nov 7.

Gryder BE, Sodji QH, Oyelere AK (2012)
Future Med Chem. 2012 Mar;4(4):505-24. doi: 10.4155/fmc.12.3.

Annunziato, A. (2008) 
Nature Education 1(1)

Wednesday, 6 February 2013

Let-7 prevents an agressive shift towards EMT in breast cancer cells

I have written previously about examples of transcription factors (Twist) which can bind DNA to help the initiation of transcription, and chromatin re-remodelling factors (FOXA1) which can constrict or release tightly wound DNA. Transcription makes a copy of DNA called messenger RNA, this contains the gene tic information coding for the protein to be made, as well as regions before and after that gene DNA. When the human genome was sequenced a large proportion of our DNA was discovered to not code for specific genes and was termed “junk DNA”. The recent ENCODE project was a massive effort to study the human genome in more detail, interestingly they found that most of this “junk DNA” actually has a function. So what does this DNA do? Some of the DNA codes for microRNAs, these are small pieces of RNA which can negatively regulate the second major step of making protein, translation. These microRNAs contain a “seed” sequence which can share similarity with one or more messenger RNA sequences, microRNAs help guide cellular machinery to messenger RNA that prevents it from being translated into protein. The numbers of different microRNAs present in cells can therefore have a dramatic effect on the levels of many proteins in the cell, including those for processes such as cell growth and cell survival. Cancer cells exhibit changes in microRNA levels which allows them to alter protein expression to increase growth and avoid cell death.

Let-7 was discovered in a species of roundworm called Caenorhabditis elegans and is one of the first observed microRNAs; it is also expressed in mammalian cells such as humans and has been investigated in the context of cancer. Let-7, along with another microRNA miR-200, has been shown to control the epithelial to mesenchymal transition (EMT) in breast cancer cells, a process mentioned here in a previous blog post. A recent study by Guo and colleagues looked at a protein called oncostatin M, which is released by breast cancer cells and can cause them to undergo metastasis through EMT. They first show that oncostatin M is indeed present in breast cancer cells. Next, they take breast cancer cells that show low levels of oncostatin M that are less aggressive and treat them with oncostatin M, this makes them undergo EMT and become more motile and better at invading into a substance called Matrigel which mimics human tissue. When cells were treated with oncostatin M levels of the microRNAs Let-7 and miR-200 were reduced suggesting that they may negatively regulate oncostatin M induced EMT. To test this, the group artificially raised levels of both these microRNAs which as expected reduced the effect of oncostatin M to cause EMT. Additionally, preventing the action of Let-7, but interestingly not miRNA200, resulted in an increase in EMT.

Finally, the group probed the potential pathway of proteins involved in the Let-7  and miR200 dependent repression of oncostatin M induced EMT. They showed that a protein called HMGA2 is the “master regulator” of oncostatin M induced EMT, and is targeted by Let-7 microRNA. To increase HMGA2 protein levels in cancer cells and induce EMT, Let-7 levels are reduced by a protein called Lin28. Oncostatin M increases Lin28 levels through the transcription factor Stat3.This pathway is important for the initiation of EMT in breast cancer cells, whereas miR200 is directly inhibited by Stat3 allowing an increase in the levels of a miR200 target protein ZEB1. ZEB1 is a transcription factor important in initiation and maintenance of EMT. This study has therefore revealed that Let-7 and miR200 microRNAs act as brakes to prevent  cells undergoing EMT. By utilising a Stat3 signalling pathway, cancer cells can overcome this brake and become more aggressive by entering into EMT.

Mentioned Articles

Guo L, Chen C, Shi M, Wang F, Chen X, Diao D, Hu M, Yu M, Qian L, Guo N. (2013)
Stat3-coordinated Lin-28-let-7-HMGA2 and miR-200-ZEB1 circuits initiate and maintain oncostatin M-driven epithelial-mesenchymal transition.
Oncogene. 2013 Jan 14. doi: 10.1038/onc.2012.573. [Epub ahead of print]

Iorio MV, Croce CM.(2012)
Causes and consequences of microRNA dysregulation.
Cancer J. 2012 May-Jun;18(3):215-22. doi: 10.1097/PPO.0b013e318250c001.

Peter ME. (2009)
Let-7 and miR-200 microRNAs: guardians against pluripotency and cancer progression.
Cell Cycle. 2009 Mar 15;8(6):843-52. Epub 2009 Mar 22.

Sunday, 3 February 2013

FOXA1 is a gatekeeper, as well as a marker, for less aggressive breast cancer

Breast cancer is a complex disease, comprising of several recognised subtypes which can be distinguished by factors including the signature of the proteins within the tumour cells. Two such subtypes include luminal and basal breast cancer, the latter is more agressive and has a poorer prognosis for patients. Recent work has suggested that basal breast cancer cells may arise from luminal cells, although the mechanism for this is unclear.

A protein called FOXA1 may be the key to this transformation and Bernardo and colleges explore this in a recent paper in the journal Oncogene. The double helix is the basic structure of DNA (although exciting research from a group in Cambridge has identified four stranded DNA helices in cancer cells). Proteins and modifications to the double helix DNA compact it within the nucleus of the cell into a tightly wound structure known as chromatin. Like transcription factors such as twist, chromatin re-modellers including FOXA1, are capable of altering which genes are turned on and subsequently made into proteins. But chromatin re-modellers do this by altering the structure of chromatin, making the genes in DNA less or more accessible and in turn changing which proteins are made. Changing levels of FOXA1 in cells can therefore have dramatic results on the pattern of proteins, this can lead to changes in the function of those cells.

The group first took breast cancer cells which represent either luminal or basal subtypes and measured how much FOXA1 was present. In agreement with previous studies, luminal breast cancer cells had high levels of FOXA1, whereas this protein was almost undetectable in basal breast cancer cells. The researchers then took luminal breast cancer cells, artificially reduced the levels of FOXA1 and measured which genes were being transcribed (the first stage in making proteins of genes). This gives a fingerprint of all the genes turned on or off in a cell, called the "transcriptome". Interestingly, the loss of FOXA1 in luminal cells led to a decrease in luminal genes and an increase in basal genes switched on. This change from a luminal to basal gene signature with loss of FOXA1 expression was accompanied by increased motility and invasiveness of breast cancer cells.

FOXA1, therefore acts to prevent the conversion from a luminal to basal type breast cancer, and therefore limits the agressiveness of the tumour. This study supports the evidence that FOXA1 expression marks a less aggressive form of breast cancer with better prognosis, however it also suggests that efforts to target FOXA1 as a treatment for luminal breast cancers may have serious unwanted consequences such as increasing aggressiveness.

Mentioned Articles
Bernardo GM, Bebek G, Ginther CL, Sizemore ST, Lozada KL, Miedler JD, Anderson LA, Godwin AK, Abdul-Karim FW, Slamon DJ, Keri RA. (2013)
FOXA1 represses the molecular phenotype of basal breast cancer cells.
Oncogene. 2013 Jan 31;32(5):554-63. doi: 10.1038/onc.2012.62. Epub 2012 Mar 5.

Yamaguchi N, Ito E, Azuma S, Honma R, Yanagisawa Y, Nishikawa A, Kawamura M, Imai J, Tatsuta K, Inoue J, Semba K, Watanabe S. (2008)
FoxA1 as a lineage-specific oncogene in luminal type breast cancer.
Biochem Biophys Res Commun. 2008 Jan 25;365(4):711-7. Epub 2007 Nov 26. [Abstract and figures free]

Thorat MA, Marchio C, Morimiya A, Savage K, Nakshatri H, Reis-Filho JS, Badve S. (2008)
Forkhead box A1 expression in breast cancer is associated with luminal subtype and good prognosis.
J Clin Pathol. 2008 Mar;61(3):327-32. Epub 2007 Nov 23. [Abstract only free] (2013) Four-stranded ‘quadruple helix’ DNA structure proven to exist in human cells - Research - University of Cambridge. [online] Available at: [Accessed: 3 Feb 2013].

Phillips, T. & Shaw, K. (2008) Chromatin remodeling in eukaryotes. Nature Education 1(1)

Thursday, 31 January 2013

A subset of T cells provide new insight into the mechanism of Graft Versus Host Disease

The term leukemia covers a range of haematological malignancies (cancers of blood cell origin). Patients can be treated by radiation or multi-drug chemotherapy. Recent research has focused on single agent therapeutics for use alone, or in combination with established treatments. Even difficult to treat leukemias such as chronic lymphocytic leukemia (CLL) have seen advances

However, the treatment of haematological malignancies usually involves high doses of chemo- and radio-therapy, which kills cancerous blood cells but also affects the body's ability to repopulate the blood with healthy white blood cells. To combat this, cancer treatment can be followed up with a replacement of the bone marrow or blood stem cells by transplantation from a donor. One very unfortunate side effect of this transplantation is the response of the transplanted (graft) cells to the host cells, this is known as Graft Versus Host Disease (GVHD). To treat GVHD, patients are given drugs to suppress the graft cell immune response, however these drugs can have severe side effects.

A very interesting research article published in the journal PLoS One, by van der Waart et al from The Netherlands, addresses one mechanism by which GVHD develops in patients treated for haematological malignancies by stem cell transplantation.

A recently discovered subtype of white blood cells, T cells called Th17 cells which produce a small signalling protein called IL-17, have been implicated in GVHD. This present study assessed the white blood cell content of patients with a range of haematological malignancies treated in the manner described above. They found that a subpopulation of Th17 cells which had high levels of the protein CD161 on their surface were resistant to the  effects of immuno suppressive drug treatment. These cells are protected by expression of a transporter on their surface (ABCB1) that removes the drug which would normally prevent their growth.

An interesting observation was that in patients with GVHD the number of CD161 expressing cells in the blood was decreased. The study goes on to show that in fact these cell relocate from the blood to tissue sites where GVHD is visible. These cells are able to respond to a small signalling protein, a chemokine called CCL20, which is enriched in tissue from patients with GVHD and  potentially pulls these cells from the blood into the tissue. An elegant use of an imaging technique known as immuno fluorescence, showed that the cells found in GVHD tissue indeed contains cells which are T cells expressing high levels of CD161 on their surface as well, as the protein which recognises CCL20.

This study provides two observations that could be potentially beneficial for the management of GVHD: a decrease in the number of CD161 expressing white blood cells in the blood of patients following reconstitution by stem cell transplantation may act as a marker for patients likely to develop GVHD. Additionally, further understanding of the role of this subset of T cells in GVHD may give rise to novel treatments for the management of GVHD.

Mentioned Articles

van der Waart AB, van der Velden WJ, van Halteren AG, Leenders MJ, Feuth T, Blijlevens NM, van der Voort R, Dolstra H. (2012)
Decreased levels of circulating IL17-producing CD161+CCR6+ T cells are associated with graft-versus-host disease after allogeneic stem cell transplantation.
PLoS One. 2012;7(12):e50896. doi: 10.1371/journal.pone.0050896. Epub 2012 Dec 4. (2009) About graft versus host disease (GVHD) : Cancer Research UK : CancerHelp UK. [online] Available at: [Accessed: 31 Jan 2013].

Breast cancer cells TWIST macrophages to aid blood vessel growth

Epithelial to mesenchymal transition (EMT) is a process where epithelial cells, those that form tissues of our major organs such as the lungs, gut, skin and breast can transform into mesenchymal cells. This transition causes the cells to take on a more motile and flexible pattern of behaviour. EMT is a crucial process in the initial development of the human body and also helps to repair damaged tissue following wounds. However, cancer cells are also able to exploit the process of EMT to help them to help them leave the mass of epithelial cells forming the primary tumour and move to distant secondary sites.

The processes that regulate EMT during development are highly regulated, this is achieved in part by small proteins called transcription factors. Transcription factors interact with DNA and recruit machinery that controls when genes are made into the proteins, which ultimately bring about changes within the cell. Three transcription factors particularly important in EMT during development are: Slug, Snail and Twist; recently these proteins have begun to be investigated in the context of cancer. They are often up-regulated in cancer and their presence in tumours may indicate a poor survival rate for patients. They promote cancer mainly through their effects on proteins involved in EMT, and much research is being currently undertaken with this aspect in mind.

However, a study published this month in the journal Cancer Research by Low-Marchelli and colleagues describes a novel function for Twist in the way in which cancer cells recruit blood vessels. This process, termed angiogenesis, is required to give a tumour sufficient blood to continue to grow. Normal breast epithelial cells do not express detectable levels of Twist, but when Twist is artificially added to these cells they are better at encouraging blood vessel growth.

While looking for the mechanism by which Twist increases angiogenesis, the group found that Twist expressing breast cells released more of one particular signalling protein, CCL2, than normal breast cells. This CCL2 was shown to be required for the promotion of blood vessel growth by Twist; interestingly this was independent of Twist’s role in EMT. CCL2 belongs to a group of proteins called chemokines which act to attract other cells to move towards their source, in this case the breast cancer cells. The cells which are attracted to this CCL2 are an immune cell called macrophages, cells which are normally required for the removal of damaged, infected or even cancerous cells. However, the signalling molecules released by macrophages can also promote tumour growth directly as well as promoting stages of blood vessel development.

In conclusion, this study has elegantly revealed a mechanism where Twist in breast cancer cells can cause increased CCL2 levels to attract macrophages and promote blood vessel growth. This is an interesting new facet to Twist biology, adding further complexity to its role in cancer.

Mentioned Articles

Low-Marchelli JM, Ardi VC, Vizcarra EA, van Rooijen N, Quigley JP, Yang J. (2013)
Twist1 Induces CCL2 and Recruits Macrophages to Promote Angiogenesis
Cancer Res. 2013 Jan 15;73(2):662-71. doi: 10.1158/0008-5472.CAN-12-0653.

Shioiri M, Shida T, Koda K, Oda K, Seike K, Nishimura M, Takano S, Miyazaki M. (2006)
Br J Cancer. 2006 Jun 19;94(12):1816-22. doi:10.1038/sj.bjc.6603193

J Exp Clin Cancer Res. 2010 Sep 1;29:119. doi: 10.1186/1756-9966-29-119.

Loss of Fam38 gets SCLC moving

Small cell lung cancer (SCLC) is a very aggressive form of lung cancer; response of patients to the initial chemotherapy is good, however in most cases the cancer reoccurs and progresses. A key step in progression of advanced cancer is the breaking away of a number of cells from the original tumour which move through the body and act as a seed for new tumours in areas such as the lymph nodes. This process, termed metastasis requires cells of the original tumour to take up a more invasive pattern of cell movement. The way in which cells move is a complicated and highly regulated process, cancers hijack this processes to their own end: metastasis. 

The majority of solid tumours rely on a combination of proteins called integrins, which regulate how well one cell sticks to other cells at it moves across them, and a group of enzymes which break up and remodel the environment surrounding the tumour. However, a recent study by McHugh et al. from Edinburgh MRC and Kings College London has shown that SCLC can adopt a vastly different method of cell movement.
Normal lung cells express high levels of a protein called Fam38, this protein is involved in integrin regulation for cellular movement. A key initial observation by the group was that SCLC cells, in contrast, have very low levels of Fam38. In normal lung cells McHugh and colleagues artificially reduced Fam38 levels to a similar degree as seen in SCLC cells and looked to see what changes Fam38 loss caused. These cells showed a remarkable loss of dependence on integrins for their movement and consequently were less able to stick to other cells. 

Cells lacking Fam38 adopted a different method of movement which allowed them to move faster over a two-dimensional area and further through a three-dimensional tissue-like substance. This increased invasiveness following Fam38 loss may explain why, in part, SCLC is so aggressive and difficult to treat.
Drug discovery for treatment of the most common form of lung cancer, non-small cell lung cancer (NSCLC), has advanced quicker than for SCLC. With the discovery of the role of Fam38 in SCLC a potential new therapeutic target has been found. Further research is required, but watch this space!

Mentioned Articles:

McHugh BJ, Murdoch A, Haslett C, Sethi T (2012) Loss of the Integrin-Activating Transmembrane Protein Fam38A (Piezo1) Promotes a Switch to a Reduced Integrin-Dependent Mode of Cell Migration. PLoS ONE 7(7): e40346. doi:10.1371/journal.pone.0040346