Breakthroughs In Cancer?

Coco Chanel, the icon of 20th century fashion once said, “Only those with no memory insist on their originality.” I am reminded of this quote as I review recent discoveries in cancer, among them, the recognition that cancer represents a dysregulation of cellular metabolism.

The field of metabolomics (the systematic study of cellular energy production), explored by investigators over the last decade is little more than the rediscovery of enzymology (a branch of biochemistry that deals with the properties, activity, and significance of enzymes), biochemistry (the science dealing with the chemistry of living matter) and stoichiometry (the part of chemistry that studies amounts of substances that are involved in reactions), pioneered by investigators like Albert Lehninger, Hans Krebs, Otto Warburg, and Albert Szent-Gyorgyi. These innovators used crude tools to explore the basis of human metabolism as they crafted an understanding of bioenergetics (the study of the transformation of energy in living organisms) and oxidative phosphorylation (processes occurring in the cell’s mitochondrion that produce energy through the synthesis of ATP (energy carrier of the body).

More recently, scientists wedded to genomics have slowly come to recognize the limitations of their approach and have returned to the field of phenotypic (the observable physical or biochemical characteristics of an organism analysis.

While newcomers to the field claim to be the first to recognize the role of cellular biology in tumor biology, a cadre of dedicated investigators had already charted these waters decades earlier. Beginning with the earliest studies by Siminovitch, McCulloch and Till, subsequent investigations by Sydney Salmon and Anne Hamburger, developed the earliest iteration of cellular studies for the examination of cancer biology in primary culture.

Ovarian Cancer

The work of Black and Spear, published in the 1950s similarly explored the study of human cellular behavior for the study of cancer research. While Larry Weisenthal, Andrew Bosanquet and others established useful predictive methodologies to study cellular phenotype, their seminal contributions have gone largely unrecognized.

Today, start-up companies are examining cellular biology to predict cancer outcomes, each claiming to be the first to recognize the importance of cell death events in primary culture. The most recent and widely touted in the literature is the use of mouse avatars. Implanting biopsied explants of tissue from patients into nude mice, they grow the cancers to desired size and then inject the drugs of interest to show tumor shrinkage. To the discerning eye however, it obvious that this represents little more than an expensive, inefficient, and extremely slow way to achieve that, which can be done more easily, inexpensively, and quickly in a tissue culture environment.

When I read the promotional material of some of the new entrants to this field, I am reminded of another quote, that of Marie Antoinette, who said, “There is nothing new except what has been forgotten.”

New Diagnostic Test for the Early Detection of Lung Cancer

I was invited to discuss a new diagnostic test for the early detection of lung cancer by Gerri Willis of Fox Business News’ Willis Report.

An Italian clinical study presented at the September 2014 European Respiratory Society described 82 patients with abnormal chest x-rays. Patients breathed into a machine that measured the temperature of the exhaled air. Forty of the patients ultimately proved to have cancer and 42 did not, as confirmed by subsequent biopsy. They found a correlation between the temperature of the exhaled breath and presence of lung cancer. They also found that long term smokers had higher breath temperatures, as did those with higher stage disease.

For a variety of reasons, a test as simple as breath temperature seems unlikely to be highly specific. After all, the temperature of the exhaled breath could reflect infection, inflammation, or even activity level, as vigorous exercise can raise the body’s core temperature. Nonetheless, the fact that there is any correlation at all is of interest.

What might underlie these findings? Accepting the shortfalls of this small study, it is an interesting point of discussion. First, cancer is a hyper metabolic state. Cancers consume increased quantities of glucose, proteins, and lipids. PET scans measure these phenomena every day. Second, cancer is associated with hyper vascularity. Up-regulation of VEGF could cause hyperemia (increased capillary blood flow) in the airways of lung cancer patients, resulting in the finding. Finally, cancer, in and of itself, is an inflammatory state. Inflammation reflects increased metabolic activity that could manifest as a whole body change in basal temperature.

Lung cancer is the leading cause of cancer death in the US, constituting 27% of all cancer deaths. Despite the over 224,000 new diagnoses and 160,000 deaths, the five-year survival for lung cancer today at 17% has not changed in several decades. Nonetheless patients who are detected early (Stage I) have a greater than 50% five-year survival.

We know from the National Lung Cancer Screening Trial published in 2010, that early detection by CT scans can reduce mortality from this disease by 20%. In the cancer literature, that is huge. The problem is that screening CTs are comparatively expensive, inconvenient, expose patients to radiation and are themselves fraught with false positives and false negatives. Furthermore, it is estimated that that broad application of spiral CT’s could cost over $9 billion a year. Thus, simple, non-invasive screening techniques are sorely needed.

The use of exhaled breath to diagnose cancers has been under in development for decades. Recently, investigators from The Cleveland Clinic and others from Israel have reported good results with a microchip that measures the concentration of volatile organic compounds in the breath and provides a colorimetric score. With several hundred patients the receiver-operating curves (ROC, a technique that gauges the sensitivity and specificity of a test) in the range of 0.85 (1.0 is perfect) are quite favorable. Although these techniques have not yet gained broad application, they are extremely interesting from the standpoint of what it is they are actually measuring.

For decades, the principal focus of scientific exploration in cancer has been genomic. Investigators at Boston University and others at MD Anderson in Texas have used genomic and methylation status of oro-and naso-pharyngeal swabs to identify the earliest hallmarks of malignant transformation. To the contrary, the breath tests described above measure phenomena that fall more in the realm of metabolomics. After all, these are measures of cellular biochemical reactions and identify the transformed state at a metabolic level.

Though still in its infancy, metabolomics reflects the most appealing of all cancer analyses. Examining cancer for what it is, rather than how it came to be, uses biochemistry, enzymology and quantitative analyses. These profile the tumor at the level of cellular function. Like the platforms that I utilize (EVA-PCD), these metabolic analyses examine the tumor phenotype.

I applaud these Italian investigators for using a functional approach to cancer biology. This is a highly productive direction and fertile ground for future research. Will breath temperature measurement prove sensitive and specific enough to diagnose cancer at early stage? It is much too early to say, but at least for now, I wouldn’t hold my breath.

Of Prostate Cancer, Glucose, Metabolism and Metformin

A study conducted by Canadian investigators and reported in the September 1, 2013 issue of the Journal of Clinical Oncology examined the impact of Metformin use on mortality in men with diabetes and prostate cancer (Margel D. Urbach DR., Lipscombe LL, Metformin Use and All-Cause and Prostate Cancer-Specific Mortality Among Men with Diabetes, Journal of Clinical Oncology, volume 31, #25, pgs 3069-3075, 2013). The investigators examined 3837 patient with a median age of 75 years. They conducted a retrospective analysis examining the Ontario Province heath care records. The intent was to examine duration of exposure to Metformin as a diabetes management in patients with prostate cancer to assess the impact on all-cause and prostate cancer-specific mortality.

The results are impressive and instructive. There was a significant decrease in the risk of prostate cancer-specific and all-cause mortality, which related to the dose and duration of exposure to Metformin. The adjusted hazard ratio for the study of 0.76 indicates that there is a 24% reduction in mortality for prostate cancer-specific events with the use of Metformin. This study was not perfect, as it was retrospective, there was no randomization and it was impossible to control for all other variables such as exercise, smoking history and clinical parameters of prostate cancer. Nonetheless, there is a clear and important trend toward reduced prostate cancer and even overall mortality. This is but one of a series of clinical studies that have examined the impact of Metformin upon not only prostate cancer but also breast cancer. Much of this work was originally pioneered by Dr. Michael Pollack from McGill University in Montreal.

The biguanide class of antidiabetic drugs, originates from the French lilac or goat’s rue (Galega officinalis). (Wikipedia)

Metformin and the closely related Phenformin are members of the class of drugs known as biguanides. While the exact mode of action of the biguanides is not fully understood, they are known to disrupt mitochondrial respiration at complex I. This upregulates an enzyme known as adenosine monophosphate kinase (AMPK) thereby altering energy metabolism within the cell and down regulating mTOR. In diabetics, this drives down blood glucose to control the disease. However, in cancer patients, a profound effect is observed that suppresses synthetic pathways necessary for energy metabolism, cellular survival and cellular proliferation. These effects appear responsible for the impact upon prostate cancer. Interestingly, these drugs are more effective in controlling already transformed cells and less effective in the prevention of cancer. This is consistent with the observation that malignantly transformed cells change their state of metabolism.

This article is interesting on many levels. The first and most obvious is that this relatively inexpensive and well-tolerated drug can have an impact on prostate cancer.

Secondly, these effects appear to cross the lines of different cancer types, such that breast cancer and other forms of cancer might also be successfully treated.

The third note of interest shows that even patients without diabetes can tolerate Metformin, suggesting this as an adjunct to many different treatments. Finally and most importantly this represents the new and important recognition that cancer is not a genomic disorder, but a metabolic disorder. Cancer may utilize normal genetic elements to its own advantage. AMP kinase, LKB1 and mTOR are not unique to cancer, but instead, are found in every cell. These normal proteins are simply altered in their function in malignantly transformed cells. Metformin is one of what will soon be a large number of metabolomic agents entering the clinical arena as cancer research moves from the nucleus to the mitochondrion.

American Association of Cancer Research 2012

In my last blog, I described my recent attendance at the American Association of Cancer Research (AACR) meeting held in Chicago. This is the premier cancer research convention for basic and translational research. The AACR was the original cancer research organization that pre-dated its sister organization – the American Society of Clinical Oncology. The focus of the AACR meeting is basic research and the presentations are often geared toward PhD level scientific discovery. I find this meeting the most informative for it provides insights into therapy options that may not arrive in the clinical arena for many years.

Among the presentations was a discussion of NextGen genomic analysis allowing an entire human genome to be sequenced within 24 hours. Mapping genetic elements has enabled investigators at the University of Pennsylvania to explore acute leukemia patients at diagnosis and at the time of recurrence. Based upon mutation analysis, different subsets of patients are observed. Mono and Oligo-clonal populations yield new subpopulations following cytoreductive therapy, wherein a small percentage of tumor cells survive and repopulate as the dominant clone.

The NextGen genomic analysis serves as the basis for new solid tumor studies in which breast biopsies are obtained, before and after therapy with aromatase inhibitors, to examine the clonality of the surviving populations.

William R. Sellers, MD, vice president of Novartis Institutes for BioMedical Research Oncology, described a high throughput robotic technology capable of conducting tens of thousands of combinatorial mixtures to determine drug interactions. What I found most interesting was the observation by this investigator that, “Cell culture remains the most effective means of testing drug combinations.” We agree wholeheartedly.

New classes of lymphoma therapies are in development that target B cell signaling pathways. A prototypic agent being Ibrutinib, the Bruton’s tyrosine kinase inhibitor.

Additional developments are examining SYC as a target for small molecule inhibitors.
Our growing understanding of immune regulation is enabling investigators like James Allison to trigger tumor specific immunity. Agents like ipilumimab (AntiCTLA4), combined with other classes of small molecules and/or antibodies directed toward CD28, PD1, and ICOS regulation have the potential to change the landscape in diseases that extend from melanoma to prostate and breast.

The meeting had innumerable sessions and symposia that were geared toward or touched upon the field of metabolomics. As cells jockey for survival they both up- and down-regulate pathways essential to not only energy production but to the biosynthesis of critical metabolic intermediates. The regulation of PKM2 (pyruvate kinase isoenzyme) is now recognized as a pivotal point in the cell’s determination of catabolism (energy production), over anabolism (biosynthesis), with Serine concentrations playing an important regulatory role.

The PI3K pathway is an area of rapidly growing interest as new compounds target this key regulatory protein complex. Both selective and non-selective (pan PI3K) inhibitors are in clinical testing. Paul Workman’s group was honored for their seminal work in this and related areas of drug development. We reported our findings on the dual PI3K/mTOR inhibitor BEZ235 (Nagourney, RA et al Proc AACR, 2586, 2012).

The double-edged sword of immune response was deftly covered by Dr. Coussens who described the profound tumor stimulatory effects of T-cell, B-cell and Macrophage infiltration into the tumor microenvironment. Small molecules now in development that down-regulate macrophage signaling may soon show promise alone or in combination with other classes of drugs.

The RAS/RAF pathway becomes ever more complex as we begin to unravel the feedback loops that respond to small molecule inhibitors like Erlotinib or Vemurafanib. Investigators like Dr. Neal Rosen from Memorial Sloan-Kettering Cancer Center have long argued that simple inhibition at one node in a cascade of signaling pathways will absolutely change the dynamic and redirect up and down stream signals that ultimately overcome inhibition. Strategies to control these “resistance” mechanisms are being developed. Once again we find that simple genomic analyses underestimate the complexity of human systems.

Among the regulatory topics at this year’s meeting was a special symposium on the development and testing of multiple novel (non-FDA approved) compounds in the clinical trial setting. There will need to be a new level of cooperation and communication forged between academia, regulatory entities and the pharmaceutical industry if we are to move this process forward. I am encouraged by the early evidence that all three are recognizing and responding to that reality.

The themes of this year’s meeting included:
1. A renewed focus on the biochemistry of metabolism
2. Clear progress in field of tumor immunology
3. The growing recognition that human tumors exist as microenvironments and not isolated single cells.

We are particularly gratified by the last point.

Our EVA/PCD focus on human tumor aggregates (microspheroids) isolated directly from patients as the most accurate models for chemotherapy selection and drug discovery appears to be gaining support.

A New Target in Breast Cancer Therapy

In many ways the era of targeted therapy began with the recognition that breast cancers expressed estrogen receptors, the original work identified the presence of estrogen receptors by radioimmunoassay. Tumors positive for ER tended to be less aggressive and appear to favor bone sites when they metastasized. Subsequently, drugs capable of blocking the effects of estrogen at the estrogen receptor were developed.  Tamoxifen competes with estrogen at the level of the receptor. This drug became a mainstay with ER positive tumors and continues to be used today, decades after it was first synthesized.

Recognizing that some patients develop resistance to Tamoxifen, additional classes of drugs were developed that reduced the circulating levels of estrogen by inhibiting the enzyme aromatase, this enzyme found in adipose tissue, converts steroid precursors to estrogen.  Despite the benefits of these classes of drugs known as SERMS (selective receptor modulators), many patients break through hormonal therapies and require cytotoxic chemotherapy.

With the identification of HER-2 amplification, a new subclass of breast cancers driven by a mutation in the growth factor family provided yet a new avenue of therapy – trastuzumab (Herceptin). For HER-2 positive breast cancers Herceptin has dramatically changed the landscape. Providing synergy with chemotherapy this monoclonal antibody has also been applied in the adjuvant setting offering survival advantage in those patients with the targeted mutation.

Reports from the San Antonio breast symposium held in Texas last December, provide two new findings.

The first is a clinical trial testing the efficacy of pertuzumab. This novel monoclonal antibody functions by preventing dimerization of HER-2 (The target of Herceptin) with the other members of the human epidermal growth factor family HER-1, HER-3 and HER-4. In so doing, the cross talk between receptors is abrogated and downstream signaling in squelched.

The second important finding regards the use of everolimus. This small molecule derivative of rapamycin blocks cellular signaling through the mTOR pathway. Combining everolimus with the aromatase inhibitor exemestane, improved time to progression.

While these two classes of drugs are different, the most interesting aspect of both reports reflects the downstream pathways that they target. Pertuzumab inhibits signaling at the PI3K pathway, upstream from mTOR. Everolimus blocks mTOR itself, thus both drugs are influencing cell signaling that channel through metabolic pathways PI3K is the membrane signal from insulin, while mTOR is an intermediate in the same pathway. Thus, these are in truest sense of the word, breakthroughs in metabolomics.

Cancer Survivorship

Some of you may have read the January report from the American Cancer Society (ACS) that described a decline in U.S. cancer death rates by 1.8 percent per year in men and 1.6 percent per year in women during the period between 2004 to 2008.

These encouraging results have been touted as evidence of success in the war on cancer. The war on cancer itself began in December 1971, when then president Richard Nixon established a national priority to conquer this disease. Since that time, we have dedicated more than $200,000,000,000 to this effort and published literally millions of articles on the topic. Despite these efforts and tremendous resource allocations, the focus of this research effort, i.e. treatment of advanced malignancies, has provided limited successes.

If we drill down onto the ACS statistics we find that most of the survival changes reflect earlier detection and the successful application of cancer screening. Mammograms, colonoscopies, the use of PSA and the growing application of screening CT scans for lung cancer detection have, and will continue to have, a favorable impact on cancer statistics.

This is the good news. The bad news is that our success in treating advanced disease is almost non-existent. While there have been slow migrations in a favorable direction for the five-year survival rates in some malignancies, the big killers like lung and GI, have shown extremely limited progress. There are many reasons why cancer cures remain out of reach, but several changes could be implemented immediately to increase our rate of success.

First, we need to incorporate systems biology into cancer research. As opposed to analyte-based approaches like genomics that unravel one finding at a time, the field of biosystematics examines human cancer through the lens of interacting networks.

Second, we need to redouble our efforts in the study of basic metabolism and the growing field of metabolomics.

Third, we need to revamp the clinical trial process. Were investigators incentivized to achieve greater clinical successes, there were be fewer failed Phase II and Phase III trials. Contrary to the business world where success is rewarded, academic physicians today receive the same compensation for every patient treated, whether the intervention is successful or not. This has the unintended consequence of encouraging physicians to accrue patients to clinical trials with no focus on effective therapies. While it may be gratifying to the trialists to have successes, they receive the same compensation for their failures. Clinical investigators need skin in the game.

Finally, the regulatory environment is currently over-restrictive. The process should allow investigator-initiated efforts with more lenient review processes. The current environment that punishes dedicated physicians for stepping out of the established guideline therapies is thwarting progress and frightening dedicated investigators out of the field. Good faith efforts on the part of physicians using new drugs and combinations that document successes and failures, could unleash an army of clever physicians to utilize novel approaches to advance new therapies with little additional cost.

Lethal diseases, like advanced cancer, pose hurdles that require novel trial designs and less stringent controls. Patients confronting these illnesses should be allowed to receive therapies and should be granted the dignity to determine their own risk-benefit ratios when they confront life and death decisions. Simple consent forms could make available effective treatments while pharmaceutical corporations should be encouraged to provide drugs under the auspices of these patient-driven developmental trials.

While we applaud the discoveries of our colleagues in the field of genomics, and their analyte-driven platforms, we forget at our peril that medicine and most of its discoveries have been observational.