The targeted inhibition of Hsp90 by a synthetic small molecule, DPide offers an effective treatment strategy against TNBCs

Abstract

Triple-negative breast cancers (TNBCs) are the most aggressive and metastatic subtype of breast cancers and exhibit poor clinical outcome due to the lack of drug target receptors such as estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (Her2). The limited effectiveness of therapeutic options and the poor prognosis of TNBC patients emphasize the urgent need for identifying new therapeutic agents. In this regard, heat shock protein 90 (Hsp90) has emerged as a promising therapeutic target for the treatment of TNBCs. Hsp90 is a molecular chaperone that regulates the folding, stability, and function of many oncogenic proteins. Hence, the inhibition of Hsp90 chaperone function leads to a simultaneous blockage of multiple signaling pathways in the proliferation and survival of cancers. In the present study, we performed the design, synthesis, and biological evaluation of Hsp90 inhibitors and found that a synthetic small molecule, DPide exerted a potent anticancer activity against TNBC cell line, MDA-MB-231 and non-small cell lung cancer (NSCLC) cell line, H1975 with GI50 values of 0.478 and 1.67 μM, respectively. Soft-Agar colony formation assay also revealed that DPide suppressed the anchorage-independent growth of MDA-MB-231 cells. Western blot analysis indicated that the treatment of MDA-MB-231 cells with DPide induced the proteasomal degradation of EGFR, Her2, Met, Akt, c-Raf, and Cdk4 and the consequent cleavage of PARP, leading to apoptotic cell death. DPide also inhibited the migration and MMP9 activity of MDA-MB-231 cells, suggesting that the metastatic potential of TNBCs could be suppressed by DPide. Collectively, DPide offers an effective therapeutic option for the treatment TNBCs.