Abstract 2137: The effect of the transcription factor MAZ on kRAS transcription: a role for the G-quadruplex

Abstract

kRAS is a GTPase protein affecting normal cell proliferation, division, and apoptosis. It is mutated in >30% of all cancers, particularly in 60-90% of pancreatic cancers. Mutated kRAS leads to continuous activity and uncontrolled proliferation. To date there have been no successful clinical agents targeting mutant kRAS activity. Modulating kRAS expression has shown anti-proliferative promise as an approach in pancreatic cancer models, but is not a main avenue of pursuit for clinical development due to lack of a molecular target. Our lab is focused on the regulation of kRAS transcription through a variety of G-rich regions of DNA in the promoter capable of forming non-B-DNA structures termed G-quadruplexes (G4s). In the current study, we sought to determine the effect of the transcription factor MAZ on the regulation of kRAS, with a particular focus on the three putative G4-forming regions (herein termed near, mid, and far in reference to their relative proximity to the transcriptional start site). In a study of the kRAS promoter using a series of luciferase plasmids, MAZ expression led to a concentration-dependent decrease in promoter activity. This action was localized to interactions with the mid-G4-forming region. In the context of a more multifaceted intracellular mileu as found in the pancreatic cancer cell lines MiaPaCa-2, Panc-1, and BxPc3, the effects of MAZ were much more complex. In particular, 48 hr post-transfection with MAZ expression plasmids, monitoring of kRAS transcription revealed a cell line-specific modulation with an increase in kRAS expression in Panc-1 cells only, confirming a previous study, and no changes noted in either the MiaPaCa-2 or the Bx-Pc3 cells. Further studies are ongoing evaluating the direct binding of MAZ to the various G-rich regions in those cell lines, as well as determining the DNA structure (single-stranded, double-stranded, or G4-DNA) to which the MAZ protein is binding. Ultimately, an understanding of the regulation of this G-rich region of DNA, by MAZ or any other transcription factors such as Sp1 or p53, is an important part of the larger puzzle leading to a targeted drug discovery program focused on G4-regulation. Ultimately, G4-stabilization-mediated down regulation of kRAS has high potential for anti-cancer efficacy in pancreatic cancers, where there is a dire need for novel therapeutic development. Citation Format: Harshul Batra, Tracy A. Brooks. The effect of the transcription factor MAZ on kRAS transcription: a role for the G-quadruplex. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2137. doi:10.1158/1538-7445.AM2015-2137