If Virchow and Ehrlich Had Dreamt Together: What the Future Holds for KRAS-Mutant Lung Cancer

Abstract

Non-small-cell lung cancer (NSCLC) with Kirsten rat sarcoma (KRAS) mutations has notoriously challenged oncologists and researchers for three notable reasons: (1) the historical assumption that KRAS is "undruggable", (2) the disease heterogeneity and (3) the shaping of the tumor microenvironment by KRAS downstream effector functions. Better insights into KRAS structural biochemistry allowed researchers to develop direct KRAS(G12C) inhibitors, which have shown early signs of clinical activity in NSCLC patients and have recently led to an FDA breakthrough designation for AMG-510. Following the approval of immune checkpoint inhibitors for PDL1-positive NSCLC, this could fuel yet another major paradigm shift in the treatment of advanced lung cancer. Here, we review advances in our understanding of the biology of direct KRAS inhibition and project future opportunities and challenges of dual KRAS and immune checkpoint inhibition. This strategy is supported by preclinical models which show that KRAS(G12C) inhibitors can turn some immunologically "cold" tumors into "hot" ones and therefore could benefit patients whose tumors harbor subtype-defining STK11/LKB1 co-mutations. Forty years after the discovery of KRAS as a transforming oncogene, we are on the verge of approval of the first KRAS-targeted drug combinations, thus therapeutically unifying Paul Ehrlich's century-old "magic bullet" vision with Rudolf Virchow's cancer inflammation theory.

Keywords: G12C inhibitor; ICI; KRAS; LKB1; NSCLC; immunotherapy; lung cancer; magic bullet.

Figure 1

Simplified overview of mutant-KRAS-dependent effects on the surrounding tumor microenvironment via direct cell-to-cell interactions and/or paracrine secretion of interleukins, GM-CSF and TGFβ. These paracrine signals induce the accumulation of myeloid-derived suppressor cells (MDSCs), M2-differentiated tumor-associated macrophages (TAMs) and regulatory T cells, which impair antitumor immunity by suppressing T-cell effector functions. References are displayed in brackets.

Figure 2

Overview of therapeutic concepts for patients with KRAS-mutant NSCLC in different stages of clinical development that target mutant KRAS itself or the surrounding tumor immune microenvironment. Future clinical trials are required to decipher the optimal strategy of simultaneously or sequentially combining these treatment strategies. References if applicable are displayed in brackets. Created with biorender.com (accessed on 3 March 2021).