Chromosomal instability as a driver of non-small cell lung cancer immune evasion and brain metastasis

PROJECT SUMMARY/ABSTRACT Brain metastasis (BM) frequently arises from non-small cell lung cancer (NSCLC) and represents the most common cause of cancer related death in the US, yet our understanding of BM biology is rudimentary. Our group has recently identified excessive chromosomal instability (CIN) as a hallmark of BM19. In in vitro studies, in addition to validation in multiple independent NSCLC patient datasets (TCGA, GENIE, CCLE, and CPTAC) detailed in this proposal, we have identified CIN as a hallmark of NSCLCs harboring mutations in STK11 (encoding LKB1). LKB1-deficient NSCLCs are an aggressive tumor subtype associated with increased risk of BM and immunotherapy resistance, and thus serves as a relevant archetypical disease that may broadly inform the role of CIN in BM biology and cancer immune evasion. CIN arises from failures in correct chromosome segregation during mitosis, leading to perpetual gains and losses of chromosome arms and the creation of rupture-prone micronuclei. Upon rupture, these micronuclei expose DNA to the cytosol, activating cGAS-STING signaling. This would seemingly present a conundrum for CINhigh cancers, as prototypical outputs of cGAS- STING activation promote anti-tumor type I interferon (IFN) responses. However, it has been recently shown that chronic cGAS-STING signaling characteristic of CINhigh tumors promotes metastatic non-canonical NF-kB output, in addition to immune-evasive adenosine generation in the tumor microenvironment, the latter accomplished through adaptive increases in cGAMP export and upregulation of surface ectonucleotidases ENPP1 and NT5E. In addition to its ability to promote immunosuppression, adenosine also permeabilizes the blood brain barrier and thus may potentially mechanistically link BM to CIN. This proposal seeks to understand how cancer cell adaptations to CIN enable BM and immune evasion, namely through investigation of tonic activation of cGAS-STING signaling. In Aim 1, I propose to delineate the respective contributions of CIN and LKB1 loss per se to metastatic behavior and immunotherapy resistance in vivo. In Aim 2, I will perform spatio- temporal resolved in vivo studies to delineate CIN-intrinsic (i.e., STING signaling) and -extrinsic (e.g. adenosine generation) interactions that enable immune evasion and BM. Through generation of genetic perturbations in LKB1-deficient and WT models, I will investigate whether chronic cGAMP-triggered STING recycling is a hallmark of CINhigh, LKB1-deficient NSCLC that favors immune-evasive tumor behavior and establishment of BM. Together, these aims offer unparalleled study of interactions critical for the establishment of the brain metastatic niche and will pave the way for therapeutic development of malignant, treatment-resistant CINhigh tumors. With the guidance from exceptional mentors and collaborators and access to the unparalleled scientific research environment at Columbia University Irving Medical Center, this project will prepare me for a successful career as a physician-scientist in the field of cancer biology.