S-adenosylmethionine synthase-derived GR15 peptide suppresses proliferation of breast cancer cells by upregulating the caspase-mediated apoptotic pathway: In vitro and in silico analyses

GR15 peptide is a potential antioxidant peptide which reduces intercellular ROS levels in zebrafish larvae stressed with H2O2. Cancer is a condition which develops during oxidative stress due to various reasons. Antioxidant molecules promote apoptosis or inhibit cancer cell proliferation by regulating the ROS level in cancer cells. This study identifies the anti-cancer potency of GR15 peptide derived from S-adenosylmethionine synthase of spirulina, Arthrospira platensis. We examined the anti-cancer property of this antioxidant peptide against breast cancer cells, MCF-7. An in-vitro anticancer activity of GR15 peptide was investigated by performing the following assays: MTT, Trypan blue assay, LDH assay and IC50 value calculation. Moreover, we examined the morphology of cancer cells under inverted microscope due to apoptosis staining AO/PI. The inter-cellular cancer level was measured by DCFDA staining, and the mitochondrial membrane potential was determined by Rhodamine 123. Further, the FACS analysis was performed to identify the changes in the cell cycle phases. Altered mRNA expressions of anti-cancer genes including Bcl-2, BAX, Caspase 3 and Caspase 9 were also addressed. The GR15 peptide exhibit dose-dependent activity on MCF-7 cells. The MTT assay revealed that the GR15 peptide treatment at 45 µM showed 57 % inhibition of cancer cell proliferation. Also, the peptide significantly affects the cellular morphology and promotes apoptosis. GR15 treatment reduces the ROS level in a dose-dependent manner. The peptide is also exhibited mitochondrial membrane potential activity. As GR15 significantly upregulated the anti-cancer gene expression, an in-silico analysis was carried out to validate the anti-cancer activity. The molecular docking of GR15 showed good binding scores and significant amino acid interaction with the respective receptors. This study suggested that GR15 potentiates anticancer activity. It reduces ROS and subsequently regulates caspase-mediated apoptosis. Overall, the observations suggested that GR15 could be an anti-cancer peptide; however, further studies on in-vivo mammalian model or clinical trials need to be performed to prove the claims.