A mechanistic insight into the anti-metastatic role of the prostate specific antigen

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Prostate specific antigen is the standard circulating biomarker for prostate cancer.

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We provide novel evidence that collagen 1 is an additional substrate for PSA.

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PSA hampers first steps of cancer invasion.

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Tissue-related PSA content/activity is inversely correlated to tumor progression.

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Tissue-related PSA levels improve prediction of prostate cancer specific mortality.

Aim

Since its discovery Prostate Specific Antigen (PSA), also referred to as kallikrein-3 (KLK3), has been used as standard circulating biomarker for prostate cancer (PCa). However, its specificity remains not adequate and its mechanism of action still elusive. Therefore, deciphering PSA role throughout PCa-pathobiology would be relevant in improving both cancer diagnosis and outcome prediction. We investigated the possible role played by PSA on/in the tumor microenvironment and over the first steps of cancer invasion.

Methods

Fresh PCa-specimens and cell lines were used for ex-vivo/in-vitro invasion assays and assessment of prostate tissue-PSA (tPSA), type 1 collagen (COL1A1) and ß1-integrin expression. Tissue Cancer Genome Atlas (TCGA) and Decipher® datasets were considered to estimate tPSA clinical relevance.

Results

A more precise, inverse, correspondence between tPSA and clinical/pathological parameters was found than for circulating PSA. KLK3 combined with Gleason grade and pathologic stage, better predicted cancer-related mortality. Consistently, we demonstrated that PSA inhibits prostate extracellular-matrix (ECM) invasion by PCa cells. As for the mechanism of action, we provided novel information that PSA is able to cleave COL1A1, a main component of the ECM. Finally, ß1-integrin, a crucial COL1A1 transducing-receptor involved in tumor adhesion/invasion, resulted to be downregulated in PCa specimens with higher levels of tPSA.

Conclusions

By interfering with type 1 collagen and its downstream targets, PSA may hamper adhesion and path of the cancer cells through ECM and their migration ability, thus explaining the inverse correlation highlighted between prostate tPSA levels and clinically significant disease.

A Longitudinal Study of the Relationship between Shift Work and Prostate-Specific Antigen in Healthy Male Workers

As shift work has become prevalent globally, it is important to evaluate the health effects of shift work on employees. Several studies have demonstrated a positive association between shift work and prostate cancer. Therefore, we aimed to further examine the relationship between shift work and elevated prostate-specific antigen (PSA). Our study collected data from 66,817 male participants at baseline and followed up for about 6 years. We categorized shift worker status and shift schedule types. To evaluate the risk of elevated PSA on shift workers, we estimated hazard ratios using the Cox proportional hazards regression analyses. During a median follow-up of 4.1 years, 1030 participants developed elevated PSA. The multivariable-adjusted hazard ratio (HR) of elevated PSA for shift workers compared with daytime workers was 1.37 (1.04-1.80). Among shift workers, rotating shift workers (HR = 1.47, 95% CI 1.06-2.03) showed a significantly increased risk of elevated PSA compared with daytime workers. Our longitudinal study provides evidence for an association between shift work, especially rotating shift work, and elevations of PSA.

Natural Products to Fight Cancer: A Focus on Juglans regia

Even if cancer represents a burden for human society, an exhaustive cure has not been discovered yet. Low therapeutic index and resistance to pharmacotherapy are two of the major limits of antitumour treatments. Natural products represent an excellent library of bioactive molecules. Thus, tapping into the natural world may prove useful in identifying new therapeutic options with favourable pharmaco-toxicological profiles. Juglans regia, or common walnut, is a very resilient tree that has inhabited our planet for thousands of years. Many studies correlate walnut consumption to beneficial effects towards several chronic diseases, such as cancer, mainly due to the bioactive molecules stored in different parts of the plant. Among others, polyphenols, quinones, proteins, and essential fatty acids contribute to its pharmacologic activity. The present review aims to offer a comprehensive perspective about the antitumour potential of the most promising compounds stored in this plant, such as juglanin, juglone, and the ellagitannin-metabolites urolithins or deriving from walnut dietary intake. All molecules and a chronic intake of the fruit provide tangible anticancer effects. However, the scarcity of studies on humans does not allow results to be conclusive.

Single-nucleotide polymorphism rs1058205 of KLK3 is associated with the risk of prostate cancer: A case-control study of Han Chinese men in Northeast China

BACKGROUND

Prostate cancer (PCa) is a serious public health concern for men worldwide. However, the risk factors for PCa remain largely unclear. Aim of this study was to investigate statistical associations between the risk of prostate cancer and the rs1058205 single-nucleotide polymorphism (SNP) of the KLK3 gene, which encodes the prostate specific antigen (PSA), in a case-control study of Han Chinese men in Northeast China.

METHODS

Using a high-resolution melting curve genotyping method, we determined the genotype and allele distributions of rs1058205 in 2 groups of Han Chinese men, consisting of 268 PCa patients and 298 healthy control subjects. Logistic regression was used to evaluate associations between rs1058205 genotypes and the risk of PCa. Tumor staging and Gleason score were included in a stratified analysis of PCa risk.

RESULTS

The frequency of the TC genotype of rs1058205 in the PCa group was significantly lower than that in the control group (P = 0.049). The serum PSA level in participants with the TC genotype was significantly lower than that of the TT and CC genotypes in both the PCa and control groups (P < 0.010 for both). The TT genotype was associated with PCa, both with and without adjustment for age (P < 0.010 and P = 0.047, respectively). The TT genotype was also associated with the moderate- and high-risk PCa categories (P = 0.007 and 0.027, respectively).

CONCLUSION

The TT genotype may represent a useful biomarker for identifying high risk of PCa and as a postoperative prognosticator in Chinese PCa patients.

Walnut polyphenol metabolites, urolithins A and B, inhibit the expression of the prostate-specific antigen and the androgen receptor in prostate cancer cells

Walnuts have been gathering attention for their health-promoting properties. They are rich in polyphenols, mainly ellagitannins (ETs) that after consumption are hydrolyzed to release ellagic acid (EA). EA is further metabolized by microbiota to form urolithins, such as A and B, which are absorbed. ETs, EA and urolithins have shown to slow the proliferation and growth of different types of cancer cells but the mechanisms remain unclear. We investigate the role of urolithins in the regulatory mechanisms in prostate cancer, specifically those related to the androgen receptor (AR), which have been linked to the development of this type of cancer. In our study, urolithins down-regulated the mRNA and protein levels of both prostate specific antigen (PSA) and AR in LNCaP cells. The luciferase assay performed with a construct containing three androgen response elements (AREs) showed that urolithins inhibit AR-mediated PSA expression at the transcriptional level. Electrophoretic mobility shift assays revealed that urolithins decreased AR binding to its consensus response element. Additionally, urolithins induced apoptosis in LNCaP cells, and this effect correlated with a decrease in Bcl-2 protein levels. In summary, urolithins attenuate the function of the AR by repressing its expression, causing a down-regulation of PSA levels and inducing apoptosis. Our results suggest that a diet rich in ET-containing foods, such as walnuts, could contribute to the prevention of prostate cancer.