Abstract 266: Relationship between BAG3 expression and the cytotoxicity of laromustine in HL60 cells

Abstract

Abstract Laromustine is an experimental sulfonylhydrazine prodrug with clinical potential against acute myelogenous leukemia and glioblastoma multiforme. Cytotoxicity is largely due to DNA crosslinking activity from an electrophilic subspecies of laromustine generated in situ. However, methylisocyanate, another electrophile cogenerated upon base-catalyzed activation of laromustine, induces acute toxicity in cultured leukemia cells. Isocyanate-mediated cytotoxicity likely involves apoptotic processes revealed in experiments presented herein showing PARP cleavage, caspase 3/7 activation, and annexin-V staining. We demonstrate that compounds that yield methylisocyanate, including laromustine, cause substantial dysregulation of gene transcription patterns that are not observed with a derivative of laromustine that possesses the DNA crosslinking activity but not the methylisocyanate. Purified mRNA from promyelocytic HL60 cells treated with either 100 µM agent or an equivalent volume of DMSO was measured using real-time RT-PCR experiments and GeneChip analyses. Among the nearly 3,000 genes dysregulated upon exposure to both laromustine and its methylisocyanate-bearing analog, BCL2-associated athanogene 3 (BAG3) emerged as a promising candidate for further investigation. This anti-apoptotic gene was significantly upregulated in these conditions. So as to assess the significance its gene product in cell death or survival in cultured cells treated with laromustine, a stable cell line expressing an shRNA construct to knock down BAG3 was engineered from HL60 cells using lentiviruses. Preliminary evidence suggests that these cells are more susceptible to the cytotoxic effects of laromustine. These data suggest that BAG3 may be part of a defensive strategy for promyelocytic leukemia cells to survive treatment with laromustine. Citation Format: Stanley R. Clarke, Allie H. Naccara, Amanda J. Loya, Sam W. Marchant, Xiaoou Wang, Thomas J. LaJoie, Jordyn N. Smith, Kevin P. Rice. Relationship between BAG3 expression and the cytotoxicity of laromustine in HL60 cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 266.