Cancer Biomarker Discovery: The Entropic Hallmark

Background: It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods. Methodology/Principal Findings: Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer. Conclusions/Significance: We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-throughput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases

Will focal therapy become a standard of care for men with localized prostate cancer?

The current treatment choice for men with localized prostate cancer lies between active surveillance and radical therapy. The difference between these two extremes of care is 5% in terms of cancer-related absolute mortality at 8 years. It is generally accepted that this small difference will decrease for men diagnosed in the prostate-specific-antigen era. Radical therapy is associated with considerable adverse effects (e.g. incontinence, impotence, rectal problems) because it treats the whole gland, and damages surrounding structures in up to half of men. Men are being diagnosed at a younger age with lower-risk disease, and many have unifocal or unilateral disease. We propose a new concept whereby only the tumor focus and a margin of normal tissue are treated. This paradigm might decrease adverse effects whilst, at the same time, retaining effective cancer control. The arguments for and against active surveillance and radical therapy are reviewed in this article, with focal therapy presented as a means for bridging these two approaches