KRAS-regulation via DEAD-box helicase DDX54 in pancreatic and lung cancer cells

Abstract

Approximately 20 % of human cancers harbour a mutation in Rat Sarcoma (RAS) genes (NRAS, HRAS and KRAS), making RAS one of the most important human oncogenes. Among the RAS mutant cancers, roughly 80 % carry a mutation in KRAS with especially high prevalence in pancreatic and lung cancers. Despite being significant cancer drivers, therapeutic targeting of RAS proteins has been challenging. Only two direct inhibitors of G12C mutated KRAS have been approved for clinical use, but their effectiveness has been hindered by development of drug resistance. Thus, it becomes crucial to investigate alternative drug targets for RAS-driven cancers to which DEAD-box RNA helicases (DDXs) have emerged as promising candidates. DEAD-box helicase 54 (DDX54) has been identified by the Westermarck lab to have an important role in viability of KRAS-driven cancer cell lines. However, the exact connection between KRAS and DDX54 hasn’t yet been established. Hence this study aimed to elucidate the mechanistical framework of KRAS-action via DDX54 by hypothesizing that KRAS and DDX54 activity synergise in promoting cell survival of KRAS-dependent pancreatic and lung cancer cell lines. Drug and siRNA treatments were used to target KRAS and DDX54 individually and together to assess their effects on cell viability with colony growth assay. Western blot was used to investigate protein expression of DDX54 after the said treatments. No synergy was detected with co-targeting of KRAS and DDX54. Moreover, decrease in DDX54 protein expression was observed after KRAS inhibition. It was concluded that DDX54 is positioned downstream of RAS signalling pathway.