A new pyrrole based small molecule from Tinospora cordifolia induces apoptosis in MDA-MB-231 breast cancer cells via ROS mediated mitochondrial damage and restoration of p53 activity

Approximately 15% of globally diagnosed breast cancers are designated as triple negative breast cancer (TNBC). In this study, we investigated the effect of the natural compound, Bis(2- ethyl hexyl) 1H-pyrrole-3,4-dicarboxylate (TCCP), purified from Tinospora cordifolia on MDA-MB-231, a TNBC cell line. The pro-apoptotic nature of TCCP on MDA-MB-231 was determined by assessing various apoptotic markers. ROS generation, intracellular calcium, mitochondrial membrane potential (Delta Psi m), MPTP, cardiolipin peroxidation and caspase activity were determined fluorometrically. BAX, BCL-2, cytochrome c, caspases, and p53 protein expressions were determined by immunoblotting. Further, the effect of TCCP on DNA and cell death was determined by DNA fragmentation assay, annexin-V staining, and cell cycle analysis. TCCP treatment caused endogenous ROS generation, increase in intracellular calcium and phosphorylation of p53 in a concentration-dependent manner, which was reverted upon pre-treatment with pifithrin-mu. This led to the downstream altered expression of Bcl-2 and Bax proteins, mitochondrial membrane depolarization, MPTP, and cardiolipin peroxidation. TCCP induced cytochrome c release into the cytosol, caspase activation, ultimately resulting in DNA fragmentation. Further, induction of apoptosis and morphological alterations were evident from the phosphatidylserine externalization and increase in sub G 1 population. The in vivo Ehrlich ascites tumor (EAT) mouse study revealed the effectiveness of TCCP in reducing the tumor burden and resulted in a similar to 2 fold increase in mice survival with minimal hepato-renal toxicity. Overall, TCCP was shown to be efficient in inducing ROS and mitochondrial-mediated apoptosis by restoring p53 activity in MDA-MB-231 cells and also induced EAT cell death in vivo thereby inhibiting tumor proliferation.