Abstract
A new type of bioactive polypeptides of the neurosecretory hypothalamus called proline-rich peptides (PRPs), which are isolated from bovine neurosecretory granules of the neurohypophysis, are synthesized in the form of a common precursor protein (neurophysin vasopressin-associated glycoprotein). Proline-rich polypetide 1 (PRP-1; also known as galarmin) is comprised of 15 amino acids residues, and has been suggested to possess anti-neurodegenerative, immunoregulatory, hematopoietic, antimicrobial and antitumor properties. The cytostatic, antiproliferative effect of PRP-1 was demonstrated in the human chondrosarcoma JJ012 and triple negative breast carcinoma MDA MB 231 cell lines. PRP-1 action is disease and tissue specific. To further explore the antitumorigenic and possible cytotoxic effects of PRP-1, a morpho-functional study on the effect of PRP-1 on a mouse Ehrlich ascites carcinoma (EAC) model was conducted. The PRP-1-induced morphological features of EAC cells confirmed the apoptotic nature of PRP-1, as manifested by cell shrinkage, membrane blebbing, chromosome condensation (pyknosis) and nuclear fragmentation (karyorrhexis). The effect of PRP-1 on the number of tumor cells incubated for 24 h and their viability in trypan blue-stained samples lead to a 44% reduction in the number of viable cells on day 11 post-inoculation vs. 22% inhibition of viable cells after PRP-1 treatment (0.1 µg/ml) on day 7 post-inoculation. Apoptosis experiments using an Annexin V-cyanine 3 apoptosis detection kit indicated that 24 h incubation with 0.1 µg/ml PRP-1 caused a significant increase in the number of apoptotic cells, reaching 50.33%, compared to 8.33% in the sample control on day 7 post-inoculation.
