Evaluation of KRASG12C inhibitor responses in novel murine KRASG12C lung cancer cell line models

by Selleckchem | Aug 30 2023

Introduction: The KRAS(G12C) mutation is the most common genetic mutation in North American lung adenocarcinoma patients. Recently, direct inhibitors of the KRASG12C protein have been developed and demonstrate clinical response rates of 37-43%. Importantly, these agents fail to generate durable therapeutic responses with median progression-free survival of ~6.5 months.

Methods: To provide models for further preclinical improvement of these inhibitors, we generated three novel murine KRASG12C-driven lung cancer cell lines. The co-occurring NRASQ61L mutation in KRASG12C-positive LLC cells was deleted and the KRASG12V allele in CMT167 cells was edited to KRASG12C with CRISPR/Cas9 methods. Also, a novel murine KRASG12C line, mKRC.1, was established from a tumor generated in a genetically-engineered mouse model.

Results: The three lines exhibit similar in vitro sensitivities to KRASG12C inhibitors (MRTX-1257, MRTX-849, AMG-510), but distinct in vivo responses to MRTX-849 ranging from progressive growth with orthotopic LLC-NRAS KO tumors to modest shrinkage with mKRC.1 tumors. All three cell lines exhibited synergistic in vitro growth inhibition with combinations of MRTX-1257 and the SHP2/PTPN11 inhibitor, RMC-4550. Moreover, treatment with a MRTX-849/RMC-4550 combination yielded transient tumor shrinkage in orthotopic LLC-NRAS KO tumors propagated in syngeneic mice and durable shrinkage of mKRC.1 tumors. Notably, single-agent MRTX-849 activity in mKRC.1 tumors and the combination response in LLC-NRAS KO tumors was lost when the experiments were performed in athymic nu/nu mice, supporting a growing literature demonstrating a role for adaptive immunity in the response to this class of drugs.

Discussion: These new models of murine KRASG12C mutant lung cancer should prove valuable for identifying improved therapeutic combination strategies with KRASG12C inhibitors.

Comments:

The introduction provides an overview of the KRAS(G12C) mutation, which is the most common genetic mutation found in lung adenocarcinoma patients in North America. It highlights the development of direct inhibitors targeting the KRASG12C protein and their clinical response rates, which range from 37% to 43%. However, despite these initial responses, the inhibitors do not lead to long-lasting therapeutic effects, with a median progression-free survival of approximately 6.5 months.

The methods section describes the generation of three new murine lung cancer cell lines with the KRASG12C mutation. In these cell lines, the co-occurring NRASQ61L mutation in KRASG12C-positive LLC cells was removed, and the KRASG12V allele in CMT167 cells was modified to KRASG12C using CRISPR/Cas9 techniques. Additionally, a novel murine KRASG12C cell line, mKRC.1, was established from a tumor in a genetically-engineered mouse model.

The results indicate that all three cell lines exhibit similar sensitivities to KRASG12C inhibitors (MRTX-1257, MRTX-849, AMG-510) in in vitro experiments. However, they display distinct responses to MRTX-849 in in vivo studies. The LLC-NRAS KO tumors showed progressive growth, while mKRC.1 tumors demonstrated modest shrinkage. Furthermore, all three cell lines exhibited enhanced growth inhibition when treated with combinations of MRTX-1257 and the SHP2/PTPN11 inhibitor, RMC-4550, in vitro. Treatment with a combination of MRTX-849 and RMC-4550 resulted in transient tumor shrinkage in LLC-NRAS KO tumors and durable shrinkage in mKRC.1 tumors.

The discussion emphasizes the value of these newly generated murine models of KRASG12C mutant lung cancer for further preclinical investigations aiming to improve therapeutic strategies with KRASG12C inhibitors. These models can be utilized to explore potential combination treatments and identify more effective approaches. Additionally, the results suggest the involvement of adaptive immunity in the response to KRASG12C inhibitors, as the efficacy of single-agent MRTX-849 in mKRC.1 tumors and the combination response in LLC-NRAS KO tumors were lost in athymic nu/nu mice, which lack T cells. This finding aligns with previous research indicating the role of adaptive immune responses in the effectiveness of this class of drugs.