Morpho­functional study of the hypothalamic proline­rich polypeptide apoptotic activity against mouse Ehrlich ascites carcinoma.

A new type of bioactive polypeptides of the neurosecretory hypothalamus called proline­rich peptides (PRPs), which are isolated from bovine neurosecretory granules of the neurohypophysis, are synthesized in the form of a common precursor protein (neurophysin vasopressin­associated glycoprotein). Proline­rich polypetide 1 (PRP­1; also known as galarmin) is comprised of 15 amino acids residues, and has been suggested to possess anti­neurodegenerative, immunoregulatory, hematopoietic, antimicrobial and antitumor properties. The cytostatic, antiproliferative effect of PRP­1 was demonstrated in the human chondrosarcoma JJ012 and triple negative breast carcinoma MDA MB 231 cell lines. PRP­1 action is disease and tissue specific. To further explore the antitumorigenic and possible cytotoxic effects of PRP­1, a morpho­functional study on the effect of PRP­1 on a mouse Ehrlich ascites carcinoma (EAC) model was conducted. The PRP­1­induced morphological features of EAC cells confirmed the apoptotic nature of PRP­1, as manifested by cell shrinkage, membrane blebbing, chromosome condensation (pyknosis) and nuclear fragmentation (karyorrhexis). The effect of PRP­1 on the number of tumor cells incubated for 24 h and their viability in trypan blue­stained samples lead to a 44% reduction in the number of viable cells on day 11 post­inoculation vs. 22% inhibition of viable cells after PRP­1 treatment (0.1 µg/ml) on day 7 post­inoculation. Apoptosis experiments using an Annexin V­cyanine 3 apoptosis detection kit indicated that 24 h incubation with 0.1 µg/ml PRP­1 caused a significant increase in the number of apoptotic cells, reaching 50.33%, compared to 8.33% in the sample control on day 7 post­inoculation.