# The Role of the Tumor Microenvironment in Resistance to Oncogenic KRAS Inhibition in Lung Cancer

> **NIH NIH R21** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2024 · $218,790

## Abstract

PROJECT SUMMARY
Inhibitors against mutant KRAS—the oncogene once deemed undruggable—are impressively showing tumor
control in preclinical testing, entering the clinic for testing in various malignancies, and in the case of the
KRASG12C inhibitor Sotorasib, gaining FDA approval. MRTX1133, a KRASG12D inhibitor now entering phase 1
clinical testing, represents hope for patients bearing other KRAS mutations, including a significant number of
never smokers with non-small cell lung cancer (NSCLC), 56% of whom have a KRASG12D-mutant cancer.
MTRX1133 will likely result in a paradigm shift for these NSCLC patients. Moreover, NSCLC responds well to
immunotherapy, and thus, the efficacy of combining KRAS inhibition with immune checkpoint immunotherapy
(ICI) is expected to be even greater. However, for many molecularly targeted therapies, resistance, and therefore
relapse, is common. This has been observed in patients treated with Sotorasib, and there is concern that
resistance to MRTX1133 and other KRAS inhibitors will also develop. Resistance is often linked to the
remodeling of the tumor microenvironment (TME), and thus, an imperative need has emerged to understand
this remodeling process during intervention and tumor recurrence to guide development of future therapeutic
treatment paradigms with long-term responses.
Our analysis of the TME in a unique KrasG12D inducible and reversible mouse model of NSCLC using single cell
RNA sequencing data shows KrasG12D-dependent control of the TME. Upon initiating KrasG12D, the expression of
PDL1 decreased in a subset of myeloid cells, potentially indicating that patients with mutant KrasG12D are unlikely
to respond to immune checkpoint therapy using PD1/PDL1 inhibitors. Interestingly, when KrasG12D was turned
OFF, the expression of PDL1 increased, providing strong rationale for co-treatment of KRAS inhibitors with ICI
for these patients. Thus, we hypothesize that a) inactivation of oncogenic KrasG12D in advanced tumors
sensitizes lung cancer to anti-PDL1 antibodies and b) therapeutic interventions targeting KrasG12D will
result in remodeling of the tumor microenvironment. To test our hypothesis, we will determine tumor
regression and survival benefit of KrasG12D inhibition wherein oncogenic KRAS is inhibited either genetically or
by MRTX1133 in combination with anti-PDL1. Importantly, we will also study tumor recurrence in NSCLC due
to therapeutic resistance in our model (Aim 1). To address the urgent needs to devise effective treatments
with long-term responses and understand the interaction between oncogenic KRAS expressing cells and the
surrounding TME during treatment and relapse, we will thoroughly evaluate fibroblasts and immune status in
relapsed KrasG12D-driven lung cancer in these mice. The intricate mechanisms of a KRASG12D-regulated TME,
particularly fibroblast cells, will also be scrutinized in patient derived organoid models using MRTX1133 in
co-cultures with matching fibroblasts (Aim 2). Successful com...

## Key facts

- **NIH application ID:** 10783852
- **Project number:** 1R21CA286372-01
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Stefanie Galban
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $218,790
- **Award type:** 1
- **Project period:** 2023-12-21 → 2025-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10783852

## Citation

> US National Institutes of Health, RePORTER application 10783852, The Role of the Tumor Microenvironment in Resistance to Oncogenic KRAS Inhibition in Lung Cancer (1R21CA286372-01). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10783852. Licensed CC0.

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