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Background: Small cell lung cancer (SCLC) is characterized by a loss of TP53 and RB1 and by amplification of MYC in about 25% of patients. Our group and others have shown that MYC-driven SCLC cell lines are vulnerable to Aurora Kinase A (AURKA) inhibition. Alisertib, a selective AURKA inhibitor, has also shown clinical efficacy in MYC-positive relapsed SCLC patients in combination with paclitaxel in a phase II trial (NCT02038647). AURKA regulates DNA chromosome alignment during cell division and thus its inhibition results in mitotic stress and subsequently DNA damage. We have previously demonstrated that DNA damage response (DDR) inhibitors synergize with immune checkpoint inhibition in SCLC in vivo models by activating a STING-mediated innate immune response. Based on these findings, we hypothesized that AURKA inhibition may activate the STING pathway and induce PD-L1 expression in SCLC. Methods: We compared AURKA gene expression among a panel of SCLC and NSCLC cell lines and, similarly, in tumor versus normal tissue in SCLC clinical dataset (Sato et al.). In parallel, we explored the landscape of STING and immune genes expression in two SCLC clinical datasets (George et al. and Sato et al.).We tested human and GEMM-derived SCLC cell lines for changes in immune and DDR-related protein expression by Western blot analysis after treatment with the AURKA-i alisertib. Results: AURKA gene expression was higher in SCLC cell lines as compared to NSCLC cell lines (p=0.023) and in SCLC tumors compared to normal tissue (FC=1.6; p0.45, p Citation Format: Carminia M. Della Corte, Liz Lauren Ajpacaja, Robert J Cardnell, Carl M Gay, Lixia Diao, Qi Wang, Kavya Ramkumar, Allison C. Stewart, Rebecca B. Kow, Hannah E Stumpf, You-Hong Fan, Jing Wang, John V Heymach, Lauren A. Byers. The Aurora kinase A-inhibitor, alisertib, is a potential candidate for combination with immunotherapy in small cell lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B064. doi:10.1158/1535-7163.TARG-19-B064

The PI3K/AKT/mTOR pathway is frequently activated in head and neck squamous cell carcinoma (HNSCC), but pathway inhibition has variable efficacy. Identification of predictive biomarkers and mechanisms of resistance would allow selection of patients most likely to respond and novel therapeutic combinations. The purpose of this study was to extend recent discoveries regarding the PI3K/AKT/mTOR pathway in HNSCC by more broadly examining potential biomarkers of response, by examining pathway inhibitors with a diverse range of targets, and by defining mechanisms of resistance and potential combination therapies. We used reverse-phase protein arrays (RPPA) to simultaneously evaluate expression of 195 proteins; SNP array to estimate gene copy number; and mass array to identify mutations. We examined altered signaling at baseline and after pathway inhibition. Likewise, we examined the activation of the PI3K/AKT/mTOR pathway in HNSCC tumors by RPPA. Cell lines with PIK3CA mutations were sensitive to pathway inhibitors, whereas amplification status did not predict sensitivity. While we identified a set of individual candidate biomarkers of response to pathway inhibitors, proteomic pathway scores did not correlate with amplification or mutation and did not predict response. Several receptor tyrosine kinases, including EGFR and ERK, were activated following PI3K inhibition in resistant cells; dual pathway inhibition of PI3K and EGFR or MEK demonstrated synergy. Combined MEK and PI3K inhibition was markedly synergistic in HRAS-mutant cell lines. Our findings indicate that clinical trials of single-agent PI3K/AKT/mTOR pathway inhibitors in selected populations and of PI3K/EGFR or PI3K/MEK inhibitor combinations are warranted; we plan to conduct such trials. Mol Cancer Ther; 13(11); 2738–50. ©2014 AACR.

Background: Small cell lung cancer (SCLC) is the most lethal form of lung cancer, accounting for around 15% of lung cancers in the United States, currently having no targeted therapies with established efficacy. Using a high-throughput proteomic screen, we demonstrated overexpression of checkpoint kinase 1 (Chk1) in SCLC. Chk1 being the master regulator of the cell cycle in absence of p53, we hypothesize that Chk1 targeting may be effective SCLC because of near ubiquitous loss of p53. In the present study, we tested the effect of Chk1 targeting by shRNA-mediated knockdown and pharmacologic inhibition in an extensive panel of SCLC cell lines and in animal models. Experimental procedures: shRNA-mediated knockdown of Chk1 was done in select human SCLC lines and confirmed at the mRNA and protein level. The effect of Chk1 inhibition by LY2606368 alone and in combination with cisplatin or the PARP1/2 inhibitor talazoparib was tested in 39 SCLC cell lines. Proliferation was assessed by cell titer glo analysis and effect on cell cycle was tested by flow cytometry. Drug sensitivity (IC50) was then correlated with baseline expression level of >190 total or phosphorylated proteins measured by reverse phase protein array (RPPA) to identify potential predictive biomarkers. In vivo effect of the Chk1 inhibitor with or without cisplatin or talazoparib was tested in syngeneic and xenograft model of SCLC. Results: shRNA-mediated targeted Chk1 knockdown significantly decreased the proliferation of SCLC lines confirming Chk1 as a viable target (p90% reduction in volume) which was durable (ongoing response >50 days in 7/9 animals). The combination with cisplatin or talazoparib also resulted in tumor regression and was significantly more effective than either cisplatin or talazoparib alone. Tumor regression following LY2606368 treatment was also observed in cis-resistant H69 xenograft model of SCLC. Conclusion: The study established checkpoint kinase 1 (Chk1) targeting as a novel and active therapeutic strategy for SCLC, a disease for which the standard of care has remained unchanged for >30 years. Chk1 knockdown was sufficient to inhibit proliferation in SCLC cell lines and LY2606368, a Chk1 inhibitor in current clinical trials, showed activity as a single agent and in combination with cisplatin and PARP inhibition in vitro and in vivo. TP53-mutant cells (hallmark of SCLC) rely on Chk1 for cell cycle arrest; hence, inhibition of Chk1 in SCLC likely works by driving cells to mitotic catastrophe and apoptosis. These findings support the further investigation of Chk1 targeting and Chk1 predictive biomarkers in SCLC. Citation Format: Triparna Sen, Pan Tong, C. Allison Stewart, You Hong-Fan, Ying Feng, Jing Wang, Lauren A. Byers. Investigation of Chk1 as a novel therapeutic target for small cell lung cancer (SCLC). [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C153.