SLPI: a Novel Biomarker of Prostate Cancer

Prostate cancer (PC) is a heterogeneous disease that occurs more frequently in elderly men. Prostate cancer is usually localized and it has a slow progression; thus, the patient may not suffer from any symptom for years. However, a proportion of patients PC develops metastases and may become a clinically relevant disease that can show an aggressive behavior and, eventually, give metastases. In any event, since it is the most common male cancer in the Western countries, it is the second leading cause of cancer deaths in males. For this reason the identification of the molecular alterations determining the different clinical behaviors and of the associated biomarkers would be extremely useful.

The Secretory leukocyte protease inhibitor (SLPI) is a serine protease which best-defined function is to protect host tissues from the excessive damage by proteolytic enzymes released during inflammation. Recently SLPI has been found overexpressed in a variety of cancers (pancreatic, papillary thyroid, uterine cervix, endometrial, and ovarian cancer). In apparent contrast, SLPI has been found reduced in the sera (and tumor tissue) of prostate cancer patients in the respect of healthy subjects and of subjects with benign hyperplasia. However, SLPI has been found upregulated in castration resistant prostate cancer (CRPC) patients and in a subset of CRPC cell lines.

These data suggest that expression of SLPI in prostate cancer could be biphasic: underexpressed during the early stages and overexpressed during progression. This peculiar pattern of SLPI expression suggests that SLPI may play a role in prostate cancer pathogenesis and/or in determining its neoplastic features. In this respect, it is noteworthy that SLPI is located at 20q13.2 (HPC20 locus), a locus harboring prostate cancer susceptibility genes. Based on these data it is possible to hypothesize that prostate cancer progression could be associated, and possibly heralded, by the increase of SLPI.

This is an observational investigation of SLPI levels in blood and tissue samples of patients with prostate disease with the explorative goal to verify whether SLPI could be a potential biomarker of prostate cancer progression.