Abstract 4392: Novel combination of Di-indolylmethane (DIM) and dexamethasone induces apoptosis in myeloma cells by modulating the telomerase activity

Abstract

Abstract Background and Objectives Multiple myeloma (MM) is a B-cell malignancy involving excessive proliferation and accumulation of atypical plasma cells specifically in the bone marrow (BM) niche. Multiple primary and secondary genetic alterations play crucial role in deregulating the biology of myeloma cells giving them a malignant phenotype, hence generating a need for novel efficacious and safe therapeutic agents. Increased expression of telomerase and higher telomerase activity (RTA) has been found in majority of cancer but displays very low activity in majority of normal somatic cells. Therefore, this maiden attempt unveils the therapeutic potential of Di-indolylmethane alone or in combination with dexamethasone by targeting telomerase activity in myeloma cells. Methodology In this study, two myeloma cell lines (RPMI8226 & U266) were procured from ATCC (Manassas, VA). Di-indolylmethane (DIM) and dexamethasone (Dexa) were purchased from Sigma Aldrich (St. Louis, MO). In in-vitro study, IC50 concentration of DIM and Dexa on both cells was determined using MTT dye. Cell-cycle and apoptosis assay was performed to determine the anti-proliferative and apoptotic effects of DIM and Dexa alone or in combination. Further, caspase-3/7 activity and mitochondrial membrane potential (MMP) was determined to assessed pathway of apoptosis. Effects of single drug or combination on telomerase activity were also assessed in both myeloma cells. Results Results demonstrated that, DIM showed an IC50 conc. of 40μM in both myeloma cells while these cells were resistant to Dexa even at higher dose. In cell cycle assay, significant increase in sub-G0/G1 phase were observed with increasing dose of DIM while combination of DIM and Dexa significantly increased sub-G0/G1 cell populations in comparison to vehicle control. Similarly annexin-V/PI apoptosis assay also demonstrated increased apoptosis of both myeloma cells. Further, DIM alone or in combination with Dexa demonstrated drastic increased caspase-3/7 activity and significant decrease in MMP in both myeloma cells. Additionally, increasing dose of DIM significantly decreased telomerase activity and combination of DIM and Dexa was much more potent in decreasing telomerase activity in comparison to vehicle treatment and DIM alone. Conclusions In nutshell, this maiden attempt provided initial evidences of therapeutic potential of DIM as novel anticancer agent alone or in combination with standard chemotherapeutic agent Dexa. Further, novel combination of DIM and Dexa was much more potential in inducing apoptosis cell death and chemo-sensitizing myeloma cells than single drug treatment regime. Also intrinsic pathway of apoptosis was followed by DIM in inducing apoptosis in myeloma. Furthermore, decreased TA by DIM emphasized its potential as novel molecular therapeutic target which need further validation. Citation Format: Raman Kumar, Nidhi Gupta, . Himani, Alpana Sharma. Novel combination of Di-indolylmethane (DIM) and dexamethasone induces apoptosis in myeloma cells by modulating the telomerase activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4392.