PSP94, what is it good for? (third edition)

This monograph reviews the literature linking prostate secretory protein 94 (PSP94) to prostate cancer and benign prostatic hyperplasia (BPH). It reveals four important insights not previously reported in the scientific literature:

• PSP94 is fungicidal within epithelial cells that synthesize it, but it is not fungicidal extracellularly due to inhibition by calcium ions.
• Prostatic epithelial cells of BPH men secrete an incomplete version of PSP94 which is not fungicidal; non-BPH men only secrete the fungicidal version.
• Epidemiological data indicate that a yet-to-be-identified sexually transmissible infection is causing prostate cancer, BPH and non-bacterial prostatitis.
• The gene responsible for the synthesis of PSP94 is expressed in all late onset cancers sites, representing 75% of all cancer cases in developed countries; it is not expressed in any early onset cancer sites of unknown etiology.

The etiologies of prostate cancer and BPH are not known. Prostatic inflammation can be observed in 80% of elderly men. Epidemiologists have been predicting for more than a decade that a yet-to-be-identified sexually transmissible infection is causing prostate cancer. The search for prostatic pathogens has resulted in dozens of studies, yet a disease causing agent still eludes researchers. Research has focused on known sexually transmissible infections and bacteria.

Two 2008 genome wide association studies reported that a single-nucleotide polymorphism near the PSP94 gene was associated with a 1.6x increase in risk of prostate cancer: the risk allele causes reduced synthesis of PSP94 in the prostate.

Taken together, these facts suggest that PSP94's primary purpose is to defend epithelial cells from an intracellular pathogen which is causing prostate cancer and BPH, and possibly other diseases. Though this hypothesis is fully consistent with the current scientific literature, additional studies are necessary. Might this hypothesis be correct or not, understanding the mechanisms behind PSP94's protective properties for prostate cancer and its role in other late onset cancers should be given high priority in cancer research.