Faculty Bibliography

Inactivation of SMARCA4/BRG1, the core ATPase subunit of mammalian SWI/SNF complexes, occurs at very high frequencies in non-small cell lung cancers (NSCLC). There are no targeted therapies for this subset of lung cancers, nor is it known how mutations in BRG1 contribute to lung cancer progression. Using a combination of gain- and loss-of-function approaches, we demonstrate that deletion of BRG1 in lung cancer leads to activation of replication stress responses. Single-molecule assessment of replication fork dynamics in BRG1-deficient cells revealed increased origin firing mediated by the prelicensing protein, CDC6. Quantitative mass spectrometry and coimmunoprecipitation assays showed that BRG1-containing SWI/SNF complexes interact with RPA complexes. Finally, BRG1-deficient lung cancers were sensitive to pharmacologic inhibition of ATR. These findings provide novel mechanistic insight into BRG1-mutant lung cancers and suggest that their dependency on ATR can be leveraged therapeutically and potentially expanded to BRG1-mutant cancers in other tissues. SIGNIFICANCE: These findings indicate that inhibition of ATR is a promising therapy for the 10% of non-small cell lung cancer patients harboring mutations in SMARCA4/BRG1. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/18/3841/F1.large.jpg.

Despite advancements in treatment options, the overall cure and survival rates for non-small cell lung cancers (NSCLC) remain low. While small-molecule inhibitors of epigenetic regulators have recently emerged as promising cancer therapeutics, their application in patients with NSCLC is limited. To exploit epigenetic regulators as novel therapeutic targets in NSCLC, we performed pooled epigenome-wide CRISPR knockout screens in vitro and in vivo and identified the histone chaperone nucleophosmin 1 (NPM1) as a potential therapeutic target. Genetic ablation of Npm1 significantly attenuated tumor progression in vitro and in vivo. Furthermore, KRAS-mutant cancer cells were more addicted to NPM1 expression. Genetic ablation of Npm1 rewired the balance of metabolism in cancer cells from predominant aerobic glycolysis to oxidative phosphorylation and reduced the population of tumor-propagating cells. Overall, our results support NPM1 as a therapeutic vulnerability in NSCLC.

PURPOSE/OBJECTIVE:We aimed to investigate the treatment effect of chemotherapy on ground-glass opacity (GGO)-featured lung adenocarcinoma radiologically and pathologically. METHODS:This retrospective study included patients who met the following criteria: (1) presence of lung GGO lesions before chemotherapy for other concurrent malignancies; (2) underwent surgical resection of GGO-featured primary lung adenocarcinoma. The last computed tomography images before chemotherapy (CT1) and the last images before GGO resection (CT2) were reviewed to assess radiologic response. Specimens of the resected tumors were reviewed to evaluate the histopathologic response. Immunohistochemical staining of ki-67, caspase-3 and β-gal was performed and compared between these tumors and a propensity score-matched (1:1) cohort of GGO-featured lung adenocarcinoma without prior chemotherapy. RESULTS:Forty-four patients with 55 GGO lesions were included. There were 20 mixed GGOs and 22 invasive adenocarcinomas. These patients all received at least three cycles of chemotherapy for other concurrent malignancies in breast, lung, cervix, ovary or rectum. Thirty-four (77%) patients received chemotherapy regimens that contained platinum, pemetrexed, paclitaxel, docetaxel or gemcitabine. The median interval between CT1 and CT2 was 10 months. Radiologically, all the GGO lesions either remained unchanged or enlarged. There was no chemotherapy-induced histopathologic response (necrosis, fibrosis or inflammation) in any of these tumors. The protein expression of ki-67, caspase-3 and β-gal was comparable between GGO-featured lung adenocarcinoma with or without prior chemotherapy. CONCLUSION/CONCLUSIONS:GGO-featured lung adenocarcinoma has no response to chemotherapy. For these patients, chemotherapy should not be a treatment option.

PURPOSE/OBJECTIVE:Lung squamous cell carcinoma (LSCC) is a deadly disease for which only a subset of patients responds to immune checkpoint blockade (ICB) therapy. Therefore, preclinical mouse models that recapitulate the complex genetic profile found in patients are urgently needed. EXPERIMENTAL DESIGN/METHODS:We used CRISPR genome editing to delete multiple tumor suppressors in lung organoids derived from Cre-dependent SOX2 knock-in mice. We investigated both the therapeutic efficacy and immunological effects accompanying combination PD-1 blockade and WEE1 inhibition in both mouse models and LSCC patient-derived cell lines. RESULTS:We show that multiplex gene editing of mouse lung organoids using the CRISPR-Cas9 system allows for efficient and rapid means to generate LSCCs that closely mimic the human disease at the genomic and phenotypic level. Using this genetically-defined mouse model and three-dimensional tumoroid culture system, we show that WEE1 inhibition induces DNA damage that primes the endogenous type I interferon and antigen presentation system in primary LSCC tumor cells. These events promote cytotoxic T cell-mediated clearance of tumor cells and reduce the accumulation of tumor-infiltrating neutrophils. Beneficial immunological features of WEE1 inhibition are further enhanced by the addition of anti-PD-1 therapy. CONCLUSIONS:We developed a mouse model system to investigate a novel combinatory approach that illuminates a clinical path hypothesis for combining ICB with DNA damage-inducing therapies in the treatment of LSCC.

PURPOSE/OBJECTIVE:system. EXPERIMENTAL DESIGN/METHODS:genetically engineered mouse model (GEMM). RESULTS:was more effective compared to single agent neratinib or trastuzumab and was associated with more robust inhibition of HER2 and downstream signaling. CONCLUSIONS:using PDX tumors. This approach may accelerate the identification and clinical development of therapies for targets with no or few existing models and/or therapies.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Programmed cell death protein 1 (PD-1) ligation delimits immunogenic responses in T cells. However, the consequences of programmed cell death 1 ligand 1 (PD-L1) ligation in T cells are uncertain. We found that T cell expression of PD-L1 in cancer was regulated by tumor antigen and sterile inflammatory cues. PD-L1⁺ T cells exerted tumor-promoting tolerance via three distinct mechanisms: (1) binding of PD-L1 induced STAT3-dependent 'back-signaling' in CD4⁺ T cells, which prevented activation, reduced T_H1-polarization and directed T_H17-differentiation. PD-L1 signaling also induced an anergic T-bet^-IFN-γ^- phenotype in CD8⁺ T cells and was equally suppressive compared to PD-1 signaling; (2) PD-L1⁺ T cells restrained effector T cells via the canonical PD-L1-PD-1 axis and were sufficient to accelerate tumorigenesis, even in the absence of endogenous PD-L1; (3) PD-L1⁺ T cells engaged PD-1⁺ macrophages, inducing an alternative M2-like program, which had crippling effects on adaptive antitumor immunity. Collectively, we demonstrate that PD-L1⁺ T cells have diverse tolerogenic effects on tumor immunity.

Rewiring of metabolic pathways is a hallmark of tumorigenesis as cancer cells acquire novel nutrient dependencies to support oncogenic growth. A major genetic subtype of lung adenocarcinoma with KEAP1/NRF2 mutations, which activates the endogenous oxidative stress response, undergoes significant metabolic rewiring to support enhanced antioxidant production. We demonstrate that cancers with high antioxidant capacity exhibit a general dependency on exogenous non-essential amino acids (NEAAs) that is driven by the Nrf2-dependent secretion of glutamate through system x_c^- (XCT), which limits intracellular glutamate pools that are required for NEAA synthesis. This dependency can be therapeutically targeted by dietary restriction or enzymatic depletion of individual NEAAs. Importantly, limiting endogenous glutamate levels by glutaminase inhibition can sensitize tumors without alterations in the Keap1/Nrf2 pathway to dietary restriction of NEAAs. Our findings identify a metabolic strategy to therapeutically target cancers with genetic or pharmacologic activation of the Nrf2 antioxidant response pathway by restricting exogenous sources of NEAAs.

EGFR-mutated lung adenocarcinoma patients treated with gefitinib and osimertinib show a therapeutic benefit limited by the appearance of secondary mutations, such as EGFRT790M and EGFRC797S. It is generally assumed that these secondary mutations render EGFR completely unresponsive to the inhibitors, but contrary to this, we uncovered here that gefitinib and osimertinib increased STAT3 phosphorylation (p-STAT3) in EGFRT790M and EGFRC797S tumoral cells. Interestingly, we also found that concomitant Notch inhibition with gefitinib or osimertinib treatment induced a p-STAT3-dependent strong reduction in the levels of the transcriptional repressor HES1. Importantly, we showed that tyrosine kinase inhibitor-resistant tumors, with EGFRT790M and EGFRC797S mutations, were highly responsive to the combined treatment of Notch inhibitors with gefitinib or osimertinib, respectively. Finally, in patients with EGFR mutations treated with tyrosine kinase inhibitors, HES1 protein levels increased during relapse and correlated with shorter progression-free survival. Therefore, our results offer a proof of concept for an alternative treatment to chemotherapy in lung adenocarcinoma osimertinib-treated patients after disease progression.