A Comparative drug-response analysis of KRAS4A and 4B splicing isoforms in KRAS-mutant Lung Adenocarcinoma.

KRAS mutant Lung adenocarcinoma (LUAD) is responsible of 7% of total cancer-related deaths every year. KRAS G12C is the prominent driver mutation identified in 30% of LAUD patients, representing one of the main challenges in the treatment of lung tumors. The KRAS oncogene was considered undruggable until 2021 when FDA approved the first specific KRAS G12C inhibitors Sotorasib (AMG510) and Adagrasib (MRTX849), opening a new season in the LUAD treatment. However, emerging resistance mechanisms rising in 6 months on average limit the patients response. The complex KRAS biology is also characterized by alternative splicing giving rise to two distinct isoforms, KRAS4A and KRAS4B. Because KRAS4B is highly express in LUAD its role is well established, while the biological role of KRAS4A isoform is still under investigation. This study evaluates the KRAS4A activity in LAUD analyzing the biological differences with KRAS4B variant and the differential responses to specific KRAS inhibitors. A genetically modified model with conditional RAS isoforms knock-out (the RAS-less system) was generated to express exogenous KRAS4A in presence or absence of the endogenous KRAS4B, both in wild-type and mutant conditions. This model enables to compare drug responses between cells carrying different KRAS4A mutations (G12C, G12D) without the interference of the KRAS4B variant. Preliminary results underlined different sensitivity to KRAS inhibitors between the two splicing variants, opening new perspectives in KRAS target therapies development.