Activation of the PI3K/mTOR Pathway following PARP Inhibition in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive malignancy with limited treatment options. We previously found that PARP is overexpressed in SCLC and that targeting PARP reduces cell line and tumor growth in preclinical models. However, SCLC cell lines with PI3K/mTOR pathway activation were relatively less sensitive to PARP inhibition. In this study, we investigated the proteomic changes in PI3K/mTOR and other pathways that occur following PAPR inhibition and/or knockdown in vitro and in vivo. Using reverse-phase protein array, we found the proteins most significantly upregulated following treatment with the PARP inhibitors olaparib and rucaparib were in the PI3K/mTOR pathway (p-mTOR, p-AKT, and pS6) (p≤0.02). Furthermore, amongst the most significantly down-regulated proteins were LKB1 and its targets AMPK and TSC, which negatively regulate the PI3K pathway (p≤0.042). Following PARP knockdown in cell lines, phosphorylated mTOR, AKT and S6 were elevated and LKB1 signaling was diminished. Global ATP concentrations increased following PARP inhibition (p≤0.02) leading us to hypothesize that the observed increased PI3K/mTOR pathway activation following PARP inhibition results from decreased ATP usage and a subsequent decrease in stress response signaling via LKB1. Based on these results, we then investigated whether co-targeting with a PARP and PI3K inhibitor (BKM-120) would work better than either single agent alone. A majority of SCLC cell lines were sensitive to BKM-120 at clinically achievable doses, and cMYC expression was the strongest biomarker of response. At clinically achievable doses of talazoparib (the most potent PARP inhibitor in SCLC clinical testing) and BKM-120, an additive effect was observed in vitro. When tested in two SCLC animal models, a greater than additive interaction was seen (p≤0.008). The data presented here suggest that combining PARP and PI3K inhibitors enhances the effect of either agent alone in preclinical models of SCLC, warranting further investigation of such combinations in SCLC patients.

[1]  G. Mills,et al.  Abstract CT324: Phase I of oral BKM120 or BYL719 and olaparib for high-grade serous ovarian cancer or triple-negative breast cancer: Final results of the BKM120 plus olaparib cohort , 2015 .

[2]  Martin Vingron,et al.  Comprehensive genomic profiles of small cell lung cancer , 2015, Nature.

[3]  T. Owonikoko,et al.  A phase 1 safety study of veliparib combined with cisplatin and etoposide in extensive stage small cell lung cancer: A trial of the ECOG-ACRIN Cancer Research Group (E2511). , 2015, Lung cancer.

[4]  B. Wang,et al.  Trapping Poly(ADP-Ribose) Polymerase , 2015, The Journal of Pharmacology and Experimental Therapeutics.

[5]  Pan Tong,et al.  drexplorer: A tool to explore dose-response relationships and drug-drug interactions , 2015, Bioinform..

[6]  G. Mills,et al.  An Integrated Molecular Analysis of Lung Adenocarcinomas Identifies Potential Therapeutic Targets among TTF1-Negative Tumors, Including DNA Repair Proteins and Nrf2 , 2015, Clinical Cancer Research.

[7]  Xiao-dong Zhu,et al.  PARP-1 promotes autophagy via the AMPK/mTOR pathway in CNE-2 human nasopharyngeal carcinoma cells following ionizing radiation, while inhibition of autophagy contributes to the radiation sensitization of CNE-2 cells , 2015, Molecular medicine reports.

[8]  C. Rudin,et al.  Small cell lung cancer: Where do we go from here? , 2015, Cancer.

[9]  G. Mills,et al.  A Comprehensive Evaluation of Biomarkers Predictive of Response to PI3K Inhibitors and of Resistance Mechanisms in Head and Neck Squamous Cell Carcinoma , 2014, Molecular Cancer Therapeutics.

[10]  S. Dan,et al.  In vitro multifaceted activities of a specific group of novel phosphatidylinositol 3-kinase inhibitors on hotspot mutant PIK3CA , 2014, Investigational New Drugs.

[11]  Hironobu Ohmatsu,et al.  Therapeutic Priority of the PI3K/AKT/mTOR Pathway in Small Cell Lung Cancers as Revealed by a Comprehensive Genomic Analysis , 2014, Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer.

[12]  D. Hardie.  AMP-activated protein kinase: maintaining energy homeostasis at the cellular and whole-body levels. , 2014, Annual review of nutrition.

[13]  D. Matei,et al.  Safety and antitumor activity of the PARP inhibitor BMN673 in a phase 1 trial recruiting metastatic small-cell lung cancer (SCLC) and germline BRCA-mutation carrier cancer patients. , 2014 .

[14]  G. Mills,et al.  Phase I study of oral BKM120 and oral olaparib for high-grade serous ovarian cancer (HGSC) or triple-negative breast cancer (TNBC). , 2014 .

[15]  Carlotta Costa,et al.  PI3K regulates MEK/ERK signaling in breast cancer via the Rac-GEF, P-Rex1 , 2013, Proceedings of the National Academy of Sciences.

[16]  J. Jonkers,et al.  Molecular Pathways Molecular Pathways : How Can BRCA-Mutated Tumors Become Resistant to PARP Inhibitors ? , 2014 .

[17]  K. Liu,et al.  Targeting Small Cell Lung Cancer Harboring PIK3CA Mutation with a Selective Oral PI3K Inhibitor PF-4989216 , 2013, Clinical Cancer Research.

[18]  Ying Feng,et al.  Proteomic Markers of DNA Repair and PI3K Pathway Activation Predict Response to the PARP Inhibitor BMN 673 in Small Cell Lung Cancer , 2013, Clinical Cancer Research.

[19]  M. Peppelenbosch,et al.  Targeting LKB1 signaling in cancer. , 2013, Biochimica et biophysica acta.

[20]  C. Britten.  PI3K and MEK inhibitor combinations: examining the evidence in selected tumor types , 2013, Cancer Chemotherapy and Pharmacology.

[21]  Peter Ballard,et al.  Discovery of 4-amino-N-[(1S)-1-(4-chlorophenyl)-3-hydroxypropyl]-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidine-4-carboxamide (AZD5363), an orally bioavailable, potent inhibitor of Akt kinases. , 2013, Journal of medicinal chemistry.

[22]  D. Brautigan,et al.  α–SNAP inhibits AMPK signaling to reduce mitochondrial biogenesis and dephosphorylates Thr172 in AMPKα in vitro , 2013, Nature Communications.

[23]  S. Yao,et al.  AMPK mediates a pro‐survival autophagy downstream of PARP‐1 activation in response to DNA alkylating agents , 2013, FEBS letters.

[24]  H. Rehrauer,et al.  Targeting the Phosphoinositide 3-Kinase p110-α Isoform Impairs Cell Proliferation, Survival, and Tumor Growth in Small Cell Lung Cancer , 2012, Clinical Cancer Research.

[25]  P. Pandolfi,et al.  Combining a PI3K inhibitor with a PARP inhibitor provides an effective therapy for BRCA1-related breast cancer. , 2012, Cancer discovery.

[26]  G. Poirier,et al.  PARP-1 Modulation of mTOR Signaling in Response to a DNA Alkylating Agent , 2012, PloS one.

[27]  Michael Peyton,et al.  An Epithelial–Mesenchymal Transition Gene Signature Predicts Resistance to EGFR and PI3K Inhibitors and Identifies Axl as a Therapeutic Target for Overcoming EGFR Inhibitor Resistance , 2012, Clinical Cancer Research.

[28]  K. Cibulskis,et al.  Integrative genome analyses identify key somatic driver mutations of small-cell lung cancer , 2012, Nature Genetics.

[29]  Michael Peyton,et al.  Proteomic profiling identifies dysregulated pathways in small cell lung cancer and novel therapeutic targets including PARP1. , 2012, Cancer discovery.

[30]  Lei He,et al.  PI3K inhibition impairs BRCA1/2 expression and sensitizes BRCA-proficient triple-negative breast cancer to PARP inhibition. , 2012, Cancer discovery.

[31]  Jordi Rodon,et al.  Phase I, dose-escalation study of BKM120, an oral pan-Class I PI3K inhibitor, in patients with advanced solid tumors. , 2012, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[32]  Keith A. Baggerly,et al.  Surface Adjustment of Reverse Phase Protein Arrays using Positive Control Spots , 2012, Cancer informatics.

[33]  N. Ilić,et al.  PI3K-targeted therapy can be evaded by gene amplification along the MYC-eukaryotic translation initiation factor 4E (eIF4E) axis , 2011, Proceedings of the National Academy of Sciences.

[34]  Simon Ng,et al.  Identification of NVP-BKM120 as a Potent, Selective, Orally Bioavailable Class I PI3 Kinase Inhibitor for Treating Cancer. , 2011, ACS medicinal chemistry letters.

[35]  R. Herbst,et al.  Upregulated stromal EGFR and vascular remodeling in mouse xenograft models of angiogenesis inhibitor-resistant human lung adenocarcinoma. , 2011, The Journal of clinical investigation.

[36]  S. Chandarlapaty,et al.  PI3K inhibition results in enhanced HER signaling and acquired ERK dependency in HER2-overexpressing breast cancer , 2011, Oncogene.

[37]  Juan Chen,et al.  PP2A Mediated AMPK Inhibition Promotes HSP70 Expression in Heat Shock Response , 2010, PloS one.

[38]  A. Sweet-Cordero,et al.  Loss of p130 accelerates tumor development in a mouse model for human small-cell lung carcinoma. , 2010, Cancer research.

[39]  William Pao,et al.  Identifying genotype-dependent efficacy of single and combined PI3K- and MAPK-pathway inhibition in cancer , 2009, Proceedings of the National Academy of Sciences.

[40]  Xuming He,et al.  Non-parametric quantification of protein lysate arrays , 2007, Bioinform..

[41]  Edward L Spitznagel,et al.  Changing epidemiology of small-cell lung cancer in the United States over the last 30 years: analysis of the surveillance, epidemiologic, and end results database. , 2006, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[42]  M. Y. Kim,et al.  Poly(ADP-ribosyl)ation by PARP-1: 'PAR-laying' NAD+ into a nuclear signal. , 2005, Genes & development.

[43]  Alan Ashworth,et al.  Targeting the DNA repair defect in BRCA mutant cells as a therapeutic strategy , 2005, Nature.

[44]  Thomas Helleday,et al.  Specific killing of BRCA2-deficient tumours with inhibitors of poly(ADP-ribose) polymerase , 2005, Nature.

[45]  M. Prichard,et al.  A three-dimensional model to analyze drug-drug interactions. , 1990, Antiviral research.

[46]  C. I. Bliss.  THE TOXICITY OF POISONS APPLIED JOINTLY1 , 1939 .

[47]  C. Hoesley,et al.  University of Alabama School of Medicine. , 2010, Academic medicine : journal of the Association of American Medical Colleges.

[48]  Gerhard Jentzsch,et al.  Working group on , 1991 .

[49]  HighWire Press,et al.  The journal of pharmacology and experimental therapeutics , 1909 .