Activating mutations in the KRAS oncogene, particularly at Glycine 12, occur in ~ 30% of Non-Small Cell Lung Cancer (NSCLC) patients, with Cysteine substitution (G12C) being most prevalent, followed by Valine and Aspartate (G12V and G12D, respectively). In contrast, in pancreatic ductal adenocarcinoma (PDAC) and colorectal cancer (CRC), which harbour mutations in KRAS in ~ 90% and ~ 35% of cases, respectively, mainly G12D and G12V dominate, with G12C found in only ~ 5%. The FDA recently approved two direct KRAS-G12C inhibitors (KRASi), Sotorasib and Adagrasib, for NSCLC, while G12D-specific and pan-RAS inhibitors are still under clinical development. However, both intrinsic and acquired resistance remain major therapeutic challenges for KRASi. MYC, a transcription factor downstream of KRAS, is deregulated in most cancers and cooperates with KRAS in tumor progression and resistance to treatment. Although MYC was historically considered “undruggable ”, our lab has designed Omomyc, the first clinically viable direct MYC inhibitor, currently in phase Ib/II clinical trials. In this work, we aim to characterize the cooperation between KRAS and MYC in a panel of human cancer cell lines, evaluate the therapeutic potential of combining Omomyc with KRASi, and explore whether MYC inhibition could help overcome resistance to KRAS-targeted therapies.

We started with a panel of NSCLC cell lines and profiled their basal KRAS -related signaling pathways , assessing their response to different KRASi, alone and in combination with Omomyc through proliferation and western blot assays. Cell cycle and apoptosis were evaluated by BrdU/PI and Annexin V/PI staining via flow cytometry, respectively. Finally, the combinatorial treatment was also tested in vivo in a KRAS-G12C NSCLC Patient-Derived Xenograft (PDX) mouse model. The study was then extended also to KRAS-mutant CRC and PDAC cell lines.

Here, we demonstrate for the first time that dual inhibition of KRAS and MYC synergistically reduces cell proliferation and induces apoptosis. Moreover, Omomyc increases the sensitivity and reverts intrinsic resistance to sotorasib (KRAS-G12Ci), independently of the sensitivity to each inhibitor. Interestingly, cells with acquired resistance to sotorasib, which showed increased MYC levels compared to the parental ones, were also re-sensitized after Omomyc treatment. Also, in vivo, the combination reduces tumor growth and increased tumor regression compared to sotorasib alone . This combinational strategy was further validated in KRAS-mutant CRC and PDAC cell lines, supporting its promising potential for broader clinical applicability across multiple tumor types.

These findings support dual MYC and KRAS inhibition in KRAS-mutant cancer, offering a potential strategy to overcome resistance to KRAS inhibitors.