Currently, early detection of prostate cancer involves mainly digital rectal examination (DRE) and testing of prostate-specific antigen (PSA) level in blood . However, over the years it became clear that PSA is not a specific biomarker of prostate cancer . Finding out new biomarkers is pivotal for early detection of prostate cancer, increasing the accuracy of diagnosis, and reducing the false positives in PSA testing These biomarkers include many biological compounds such as, microRNAs, small nuclear RNAs (sncRNA), proteins and metabolites .
PIWI-interacting RNAs (piRNAs), a class of sncRNA molecules, are associated with the PIWI proteins. Moreover, MicroRNAs (miRNAs) are conserved small non-coding RNAs (19-22 nucleotide-long) that mediate post-transcriptional regulation of gene expression, affecting mRNA stability and translation by binding complementary sites on target mRNAs\[15\]. Studies have shown that the miRNAs have critical roles in a variety of biological processes such as: cell proliferation, differentiation, apoptosis and carcinogenesis. Regucalcin (RGN) is an inhibitory protein of calcium signaling with calcium-binding properties. It plays a multifunctional role in the regulation of cell functions. Free amino acids, in biological fluids can be a reduced invasive method associated to a high diagnostic potential. It was found that free amino acid profiles vary depending on type of cancer and its stage.
