Abstract 5085: Inducing multipolarity of acentrosomal mitotic spindles as a novel tumor-specific targeting strategy revealed by the antimitotic effect of mdivi-1

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Traditional antimitotic drugs for cancer chemotherapy often have undesired toxicity to healthy tissue, limiting clinical application. Developing tumor-specific antimitotic strategies is necessary to improve the efficacy of drugs in the selective eradication of tumor cells. In this study, we discovered mdivi-1 (mitochondrial division inhibitor-1), which was originally reported as an inhibitor of mitochondrial fission protein dynamin-related protein 1 (Drp1), specifically disrupts M phase cell cycle progression only in human tumor cells and not in non-transformed fibroblasts and epithelial cells. The antimitotic effect of mdivi-1 is Drp1-independent, as M phase abnormality induced by mdivi-1 was observed in both Drp1 wild-type and Drp1 knockout MEF cells. We also identified that the tumor transformation process required for the antimitotic effect of mdivi-1 is downstream of SV40 large T and small t antigens - but not hTERT-mediated immortalization. Mdivi-1 induces multipolar mitotic spindles in tumor cells regardless of centrosome number. Acentrosomal spindle poles, which do not contain bona-fide centrosome components γ-tubulin and centrin-2, were found to contribute to the spindle multipolarity. The formation of such aberrant mitotic spindles leads to gross genome instability and apoptotic cell death through Bax/Bak-mediated mitochondrial outer membrane permeabilization (MOMP). Gene expression profiling comparing non-transformed and transformed cells revealed that the genes involved in assembly of acentrosomal spindles are highly up-regulated in tumor cells, thus providing the mechanism underlying the preferential formation of acentrosomal multipolar spindles in tumor cells compared to normal cells after mdivi-1 treatment. Taken together, our studies imply that mdivi-1 represents a novel class of quinazolinone compounds that function as acentrosomal spindle inducers (ASI). We suggest that promoting the assembly of multipolar mitotic spindles composed of acentrosomal poles could serve as a novel strategy in achieving a tumor-specific antimitotic effect. (Work was supported by P30CA047904, GM087798, UPCI and PA Dept of Health CURE program) Note: This abstract was not presented at the meeting. Citation Format: Jingnan Wang, Wei Qian, Masahiro Shuda, Jianfeng Li, Lucas Santana-Santos, Robert W. Sobol, Bennett Van Houten. Inducing multipolarity of acentrosomal mitotic spindles as a novel tumor-specific targeting strategy revealed by the antimitotic effect of mdivi-1. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5085. doi:10.1158/1538-7445.AM2014-5085