Immune Checkpoint Inhibitors: Has Cancer Met its Match?

The cover of S. Mukerjee's book, The Emporer of All Maladies: The Biology of Cancer. Used courtesy of Wikimedia and WLU.
The cover of S. Mukerjee’s book, The Emporer of All Maladies: The Biology of Cancer. Used courtesy of Wikimedia and WLU.

Dr. Drew M. Pardoll, Johns Hopkins University School of Medicine in Baltimore, in his 2012 review, “The blockade of immune checkpoints in cancer immunotherapy” published in Nature Reviews Cancer (1) writes:

“The myriad of genetic and epigenetic alterations that are characteristic of all cancers provide a diverse set of antigens that the immune system can use to distinguish tumour cells from their normal counterparts.”

Tumors have antigens, so we should be able to address/attack these antigens with our immune system, right?

Various immune mediators as therapeutic agents against cancer have entered and mostly flopped in clinical trials over the past 30 or more years. As a graduate student in the 1980s I remember IL-2 and interferon raising many hopes. More recently, drugs against chronic myeloid leukemia and CLL have shown early promise. However, so far cancer cells have mostly won against these therapies. Yet recent news points to some exciting new therapeutic agents, that over the past 15 years or so, and in and out of clinical trials, are getting a leg up in the cancer battle. These drugs are immune checkpoint inhibitors.

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Amino Acid Analogs as Possible Cancer Drugs

HeLa cells stained with Hoechst 33258. By TenOfAllTrades (From English wiki 1.) [Public domain], via Wikimedia Commons
Scientists look in unusual places for potential anticancer treatments. I have reviewed papers that investigated the possibility that dandelion root may harbor anticancer treatments, milk fat may moderate cancer metastasis and the effects of chemotherapy, and black raspberry extract may even prevent cancer. Sometimes, research avenues come down to an observation about what a tumor cell needs to grow and exploring the idea that molecular analogs might be a tool to block cancer growth. For the work reported in Drug Design, Development and Therapy, analogs of the amino acid glycine, specifically glyphosate and aminomethylphosphonic acid (AMPA), the degradation product of glyphosate, were used to explore this idea in cancer cell lines. Continue reading “Amino Acid Analogs as Possible Cancer Drugs”

Healthy Lifestyles: Good for You and Your Telomeres Too

DNA in a test tubeWe all know that a healthy lifestyle (diet high in whole foods and low in fat, moderate exercise, managing stress and good social support) is good for us. In fact I will go so far as to say that it isn’t even news that these things help our health and well-being.  What is news, or at least newly published, is that these changes may also have a positive effect on telomerase activity and telomere length (1). Continue reading “Healthy Lifestyles: Good for You and Your Telomeres Too”

Site-specific copy number variations in cancer: A story begins to unfold

Designed by Nick Klein for ISO-form, courtesy of Promega.
Designed by Nick Klein for ISO-form, courtesy of Promega.

Tumor cells are characterized by many features: including uncontrolled proliferation, to loss of contact inhibition, acquired chromosomal instability and gene copy number changes among them. Some of those copy number changes are site-specific, but very little is known about the mechanisms or proteins involved in creating site-specific copy number changes. In a recently published Cell paper, Black and colleagues, propose a mechanism for site-specific copy number variations involving histone methylation proteins and replication complexes.

Previous work from Klang et al. had shown that local amplification of chromosomal regions occurs during S phase and that chromatin structure plays a critical role in this amplification (2), and other work by Black and colleagues (3) implicated KDM4A in changing timing of replication by altering chromatin accessibility in specific regions. Other research also had shown that KDM4A protein levels influence replication initiation and that KDM4A has a role in some DNA damage response pathways (4,5).  Looking at the body of work, Black et al. hypothesized that KDM4A, with its roles in replication, might possibly provide link into the mechanism of site-specific copy number variation in cancer. Continue reading “Site-specific copy number variations in cancer: A story begins to unfold”

Priming an Effective T cell Response to Cancer

Cancer vaccines have been in progress for some time now. But a vaccine that is highly effective against cancer is not currently available.

However, an interesting report from Stanford University School of Medicine researchers, Dr. Irving Weissman, et al. shows some promise in a development of an altered means of stimulating the immune system, that could result in a stronger immune response and ultimately a better cancer vaccine. The paper by Weissman et al. was published electronically ahead of print in PNAS USA, May 20, 2013: “Anti-CD47 antibody-mediated phagocytosis of cancer by macrophages primes an effective antitumor T-cell response.”

Schematic of a macrophage engulfing, digesting and presenting parts of a pathogen or foreign cell to the cell surface.
Schematic of a macrophage engulfing, digesting and presenting parts of a pathogen or foreign cell to the cell surface.

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Screening for Inhibitors of CD73 (5´-ectonucleotidase) Using a Metabolite Assay


CD73 also known as 5´-Ectonucleotidase (NT5E) is a membrane-anchored protein that acts at the outer surface of the cell to convert AMP to adenosine and free phosphate. CD73 activity is associated with immunosuppression and prometastatic effects, including angiogenesis. CD73 is highly expressed on the surfaces of many types of cancer cells and other immunosuppressive cells (1). A recent study by Quezada and colleagues showed that the high concentration of adenosine produced by the CD73-catalyzed reaction on glioblastoma multiforme cells, which are characterized by extreme chemoresistance, triggered adenosine signaling and in turn, the multi-drug resistance (MDR) phenotype of these cells (2).

Because of the roles of adenosine in immunosuppression, angiogenesis and MDR phenotypes, CD73 (NT5E) is an attractive therapeutic target. However, the current methods of assaying for the ectonucleotidase activity, HPLC and a malachite green assay, are cumbersome and not suited to high-throughput screening. The HPLC assay is expensive and difficult to automate and miniaturize (3). The malachite green assay is sensitive to phosphate found in media, buffers and other solutions used in the compound-screening environment.

To address the problem of developing a reliable high-throughput screening assay for CD73, Sachsenmeier and colleagues (3) looked to a luminescent ATP-detection reagent.

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Cancer research yields unexpected results

Louis Pasteur once said “Chance favors the prepared mind”. Surely any scientist can attest to this. Discoveries of things  like artificial sweeteners, Teflon, and penicillin were all unintended products of unrelated research. Recently, scientists at the Duke Cancer Institute studying the microevolution of enzymes involved in cancer happened upon a missing enzymatic link in a very unrelated area of research that has less to do with cancer than with the production of carpeting, apparel, and auto parts(1).

Nylon is a critical component in all of those products, any many, many more. Production nylon requires a compound called adipic acid. This intermediary, one of the most widely used chemicals in the world,  is produced from fossil fuels and pollution released from its refinement process is a leading contributor to global warming. To date, there hasn’t been a “green” way of producing adipic acid because there is one critical enzyme in the synthesis pathway that isn’t available: 2-hydroxyadipate dehydrogenase.

Biochemical engineering on its own had not produced a sufficient dehydrogenase to do the job. Enter the cancer researchers.   Cancer involves the microevolution of cells which offer benefits to the cells, sometimes including gain-of-function mutations in metabolic enzymes. Duke researchers identified a  mutation in glioblastomas that alters the function of isocitrate dehydrogenase. The Duke team applied their knowledge of how enzymes change during cancer to lay the blueprints on a new method for producing  clean, green, adipic acid. By using the same mutation framework, the scientist found that they could create enzymes from homoisocitrate dehydrogenase found in yeasts and bacteria that were capable of producing adipic acid from inexpensive sugars. The group still needs to scale up their production, a process that will still require a tremendous amount of work.

1.  Reitman, Z. et al. (2012) Enzyme redesign guided by cancer-derived IDH1 mutations.  Nat. Chem. Biol.  Available online.

Does Your Daily Cup of Coffee Affect Your Risk of Cancer?

Coffee beansIs there an association between coffee consumption and incidence of cancer? The answer seems to depend on whom you ask, the study group involved, how much and what type of coffee the study participants drank and a host of other factors. Many research studies have found no link or only a weak link between the two, but recently a new study that showed a stronger association between coffee consumption and a lower risk of prostate cancer was published in the Journal of the National Cancer Institute (1). Why should we believe this new study when so many other studies have been unable to show a strong link?
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The Link Between Childhood Adversity and Cellular Aging

Neglected childAdversity and stress are known risk factors for psychiatric disorders, cardiovascular and immune disease, cognitive decline and other health problems. The long-term negative effects of adversity seem to be greatest if the traumatic events were experienced during childhood, when the brain and other biological systems are developing and maturing. Researchers are working to identify the mechanisms involved and have identified telomere shortening as one possible mechanism by which adversity increases morbidity and mortality. Continue reading “The Link Between Childhood Adversity and Cellular Aging”