Faculty Bibliography

Non-small cell lung cancers (NSCLC) that have developed resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI), including gefitinib and erlotinib, are clinically linked to an epithelial-to-mesenchymal transition (EMT) phenotype. Here, we examined whether modulating EMT maintains the responsiveness of EGFR-mutated NSCLCs to EGFR TKI therapy. Using human NSCLC cell lines harboring mutated EGFR and a transgenic mouse model of lung cancer driven by mutant EGFR (EGFR-Del19-T790M), we demonstrate that EGFR inhibition induces TGFbeta secretion followed by SMAD pathway activation, an event that promotes EMT. Chronic exposure of EGFR-mutated NSCLC cells to TGFbeta was sufficient to induce EMT and resistance to EGFR TKI treatment. Furthermore, NSCLC HCC4006 cells with acquired resistance to gefitinib were characterized by a mesenchymal phenotype and displayed a higher prevalence of the EGFR T790M mutated allele. Notably, combined inhibition of EGFR and the TGFbeta receptor in HCC4006 cells prevented EMT but was not sufficient to prevent acquired gefitinib resistance because of an increased emergence of the EGFR T790M allele compared with cells treated with gefitinib alone. Conversely, another independent NSCLC cell line, PC9, reproducibly developed EGFR T790M mutations as the primary mechanism underlying EGFR TKI resistance, even though the prevalence of the mutant allele was lower than that in HCC4006 cells. Thus, our findings underscore heterogeneity within NSCLC cells lines harboring EGFR kinase domain mutations that give rise to divergent resistance mechanisms in response to treatment and anticipate the complexity of EMT suppression as a therapeutic strategy.

Genetically engineered mouse models of lung cancer have demonstrated an important role in understanding the function of novel lung cancer oncogenes and tumor-suppressor genes identified in genomic studies of human lung cancer. Furthermore, these models are important platforms for preclinical therapeutic studies. Here, we generated a mouse model of lung adenocarcinoma driven by mutation of the discoidin domain receptor 2 (DDR2) gene combined with loss of TP53. DDR2(L63V);TP53(L/L) mice developed poorly differentiated lung adenocarcinomas in all transgenic animals analyzed with a latency of 40 to 50 weeks and a median survival of 67.5 weeks. Mice expressing wild-type DDR2 with combined TP53 loss did not form lung cancers. DDR2(L63V);TP53(L/L) tumors displayed robust expression of DDR2 and immunohistochemical markers of lung adenocarcinoma comparable with previously generated models, though also displayed concomitant expression of the squamous cell markers p63 and SOX2. Tumor-derived cell lines were not solely DDR2 dependent and displayed upregulation of and partial dependence on MYCN. Combined treatment with the multitargeted DDR2 inhibitor dasatinib and BET inhibitor JQ1 inhibited tumor growth in vitro and in vivo. Together, these results suggest that DDR2 mutation can drive lung cancer initiation in vivo and provide a novel mouse model for lung cancer therapeutics studies.

Irreversible pyrimidine-based EGFR inhibitors, including WZ4002, selectively inhibit both EGFR-activating and EGFR inhibitor-resistant T790M mutations more potently than wild-type EGFR. Although this class of mutant-selective EGFR inhibitors is effective clinically in lung cancer patients harboring EGFR(T790M), prior preclinical studies demonstrate that acquired resistance can occur through genomic alterations that activate ERK1/2 signaling. Here, we find that ERK1/2 reactivation occurs rapidly following WZ4002 treatment. Concomitant inhibition of ERK1/2 by the MEK inhibitor trametinib prevents ERK1/2 reactivation, enhances WZ4002-induced apoptosis, and inhibits the emergence of resistance in WZ4002-sensitive models known to acquire resistance via both T790M-dependent and T790M-independent mechanisms. Resistance to WZ4002 in combination with trametinib eventually emerges due to AKT/mTOR reactivation. These data suggest that initial cotargeting of EGFR and MEK could significantly impede the development of acquired resistance in EGFR-mutant lung cancer. SIGNIFICANCE: Patients with EGFR-mutant lung cancer develop acquired resistance to EGFR and mutant-selective EGFR tyrosine kinase inhibitors. Here, we show that cotargeting EGFR and MEK can prevent the emergence of a broad variety of drug resistance mechanisms in vitro and in vivo and may be a superior therapeutic regimen for these patients.

The Janus kinases (JAKs) and their downstream effectors, signal transducer and activator of transcription proteins (STATs), form a critical immune cell signaling circuit, which is of fundamental importance in innate immunity, inflammation, and hematopoiesis, and dysregulation is frequently observed in immune disease and cancer. The high degree of structural conservation of the JAK ATP binding pockets has posed a considerable challenge to medicinal chemists seeking to develop highly selective inhibitors as pharmacological probes and as clinical drugs. Here we report the discovery and optimization of 2,4-substituted pyrimidines as covalent JAK3 inhibitors that exploit a unique cysteine (Cys909) residue in JAK3. Investigation of structure-activity relationship (SAR) utilizing biochemical and transformed Ba/F3 cellular assays resulted in identification of potent and selective inhibitors such as compounds 9 and 45. A 2.9 A cocrystal structure of JAK3 in complex with 9 confirms the covalent interaction. Compound 9 exhibited decent pharmacokinetic properties and is suitable for use in vivo. These inhibitors provide a set of useful tools to pharmacologically interrogate JAK3-dependent biology.

The discovery of oncogenic driver mutations and the subsequent developments in targeted therapies have led to improved outcomes for subsets of lung cancer patients. The identification of additional oncogenic and drug-sensitive alterations may similarly lead to new therapeutic approaches for lung cancer. We identify and characterize novel FGFR2 extracellular domain insertion mutations and demonstrate that they are both oncogenic and sensitive to inhibition by FGFR kinase inhibitors. We demonstrate that the mechanism of FGFR2 activation and subsequent transformation is mediated by ligand-independent dimerization and activation of FGFR2 kinase activity. Both FGFR2-mutant forms are predominantly located in the endoplasmic reticulum and Golgi but nevertheless can activate downstream signaling pathways through their interactions with fibroblast growth factor receptor substrate 2 (FRS2). Our findings provide a rationale for therapeutically targeting this unique subset of FGFR2-mutant cancers as well as insight into their oncogenic mechanisms.

The molecular underpinnings that drive the heterogeneity of KRAS-mutant lung adenocarcinoma are poorly characterized. We performed an integrative analysis of genomic, transcriptomic, and proteomic data from early-stage and chemorefractory lung adenocarcinoma and identified three robust subsets of KRAS-mutant lung adenocarcinoma dominated, respectively, by co-occurring genetic events in STK11/LKB1 (the KL subgroup), TP53 (KP), and CDKN2A/B inactivation coupled with low expression of the NKX2-1 (TTF1) transcription factor (KC). We further revealed biologically and therapeutically relevant differences between the subgroups. KC tumors frequently exhibited mucinous histology and suppressed mTORC1 signaling. KL tumors had high rates of KEAP1 mutational inactivation and expressed lower levels of immune markers, including PD-L1. KP tumors demonstrated higher levels of somatic mutations, inflammatory markers, immune checkpoint effector molecules, and improved relapse-free survival. Differences in drug sensitivity patterns were also observed; notably, KL cells showed increased vulnerability to HSP90-inhibitor therapy. This work provides evidence that co-occurring genomic alterations identify subgroups of KRAS-mutant lung adenocarcinoma with distinct biology and therapeutic vulnerabilities. SIGNIFICANCE: Co-occurring genetic alterations in STK11/LKB1, TP53, and CDKN2A/B-the latter coupled with low TTF1 expression-define three major subgroups of KRAS-mutant lung adenocarcinoma with distinct biology, patterns of immune-system engagement, and therapeutic vulnerabilities.

PD-1 immune checkpoint blockade occasionally results in durable clinical responses in advanced metastatic cancers. However, mechanism-based predictors of response to this immunotherapy remain incompletely characterized. We performed comprehensive genomic profiling on a tumor and germline sample from a patient with refractory lung adenocarcinoma who achieved marked long-term clinical benefit from anti-PD-L1 therapy. We discovered activating somatic and germline amino acid variants in JAK3 that promoted PD-L1 induction in lung cancer cells and in the tumor immune microenvironment. These findings suggest that genomic alterations that deregulate cytokine receptor signal transduction could contribute to PD-L1 activation and engagement of the PD-1 immune checkpoint in lung cancer.

BACKGROUND: Leukocyte telomere length (LTL) is a marker of cellular turnover and oxidative stress. Studies suggest major depressive disorder (MDD) is associated with oxidative stress, but examinations of MDD and LTL have yielded mixed results, likely because of differences in measurement methods and unmeasured confounding. This study examined LTL and telomerase activity in 166 individuals with MDD compared to 166 age- and gender-matched matched controls free of any psychiatric disorder, using well-validated assays and clinical assessment methods, and controlling for a range of potential confounders. METHODS: Subjects aged 18 to 70 were evaluated by trained raters and provided blood for LTL and telomerase activity measurement. LTL was assayed using Southern blot and replicated with qPCR, and telomerase activity was assayed with a repeat amplification protocol using a commercial kit. RESULTS: There was no significant difference in telomere length for individuals with MDD [mean (SD)=9.1 (3.0)kbp] compared to controls [mean(SD)=8.9(2.5)kbp] measured by Southern blot (p=0.65) or by confirmatory qPCR (p=0.91) assays. Controlling for potential confounders did not alter the results. Telomerase activity did not differ by MDD diagnosis overall (p=0.40), but the effect of MDD was significantly modified by gender (t(299)=2.67, p=0.0079) even after controlling for potential confounders, with telomerase activity significantly greater only in males with MDD versus controls. CONCLUSION: Our well-characterized, well-powered examination of concurrently assessed telomere length and telomerase activity in individuals with clinically significant, chronic MDD and matched controls failed to provide strong evidence of an association of MDD with shorter LTL, while telomerase activity was higher in men with MDD [corrected].

LKB1 regulates both cell growth and energy metabolism. It remains unclear how LKB1 inactivation coordinates tumor progression with metabolic adaptation in non-small cell lung cancer (NSCLC). Here in Kras(G12D);Lkb1(lox/lox) (KL) mouse model, we reveal differential reactive oxygen species (ROS) levels in lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC). ROS can modulate ADC-to-SCC transdifferentiation (AST). Further, pentose phosphate pathway deregulation and impaired fatty acid oxidation collectively contribute to the redox imbalance and functionally affect AST. Similar tumor and redox heterogeneity also exist in human NSCLC with LKB1 inactivation. In preclinical trials toward metabolic stress, certain KL ADC can develop drug resistance through squamous transdifferentiation. This study uncovers critical redox control of tumor plasticity that may affect therapeutic response in NSCLC.

Adenomatous tumors in the middle ear and temporal bone are rare but highly morbid because they are difficult to detect prior to the development of audiovestibular dysfunction. Complete resection is often disfiguring and difficult because of location and the late stage at diagnosis, so identification of molecular targets and effective therapies is needed. Here, we describe a new mouse model of aggressive papillary ear tumor that was serendipitously discovered during the generation of a mouse model for mutant EGFR-driven lung cancer. Although these mice did not develop lung tumors, 43% developed head tilt and circling behavior. Magnetic resonance imaging (MRI) scans showed bilateral ear tumors located in the tympanic cavity. These tumors expressed mutant EGFR as well as active downstream targets such as Akt, mTOR and ERK1/2. EGFR-directed therapies were highly effective in eradicating the tumors and correcting the vestibular defects, suggesting these tumors are addicted to EGFR. EGFR activation was also observed in human ear neoplasms, which provides clinical relevance for this mouse model and rationale to test EGFR-targeted therapies in these rare neoplasms.