ABSTRACT
Cyclin-dependent kinase 7 (CDK7) is a central regulator of the cell cycle and gene transcription. However, little is known about its impact on genomic instability and cancer immunity. Using a selective CDK7 inhibitor, YKL-5-124, we demonstrated that CDK7 inhibition predominately disrupts cell-cycle progression and induces DNA replication stress and genome instability in small cell lung cancer (SCLC) while simultaneously triggering immune-response signaling. These tumor-intrinsic events provoke a robust immune surveillance program elicited by T cells, which is further enhanced by the addition of immune-checkpoint blockade. Combining YKL-5-124 with anti-PD-1 offers significant survival benefit in multiple highly aggressive murine models of SCLC, providing a rationale for new combination regimens consisting of CDK7 inhibitors and immunotherapies.
Subject(s)
Cyclin-Dependent Kinases/antagonists & inhibitors , Cyclin-Dependent Kinases/genetics , Genomic Instability , Lung Neoplasms/genetics , Small Cell Lung Carcinoma/genetics , Animals , Antineoplastic Agents/pharmacology , CD4-Positive T-Lymphocytes/cytology , CD8-Positive T-Lymphocytes/cytology , Chemokine CXCL9/metabolism , DNA Damage , Female , Humans , Immune System , Inflammation , Interferon-gamma/metabolism , Lung Neoplasms/drug therapy , Lung Neoplasms/immunology , Male , Mice , Micronucleus Tests , Programmed Cell Death 1 Receptor/antagonists & inhibitors , Pyrazoles/pharmacology , Pyrroles/pharmacology , Signal Transduction , Small Cell Lung Carcinoma/drug therapy , Small Cell Lung Carcinoma/immunology , Tumor Necrosis Factor-alpha/metabolism , Cyclin-Dependent Kinase-Activating KinaseABSTRACT
Despite substantial progress in lung cancer immunotherapy, the overall response rate in patients with KRAS-mutant lung adenocarcinoma (LUAD) remains low. Combining standard immunotherapy with adjuvant approaches that enhance adaptive immune responses-such as epigenetic modulation of antitumor immunity-is therefore an attractive strategy. To identify epigenetic regulators of tumor immunity, we constructed an epigenetic-focused single guide RNA library and performed an in vivo CRISPR screen in a Kras G12D/Trp53 -/- LUAD model. Our data showed that loss of the histone chaperone Asf1a in tumor cells sensitizes tumors to anti-PD-1 treatment. Mechanistic studies revealed that tumor cell-intrinsic Asf1a deficiency induced immunogenic macrophage differentiation in the tumor microenvironment by upregulating GM-CSF expression and potentiated T-cell activation in combination with anti-PD-1. Our results provide a rationale for a novel combination therapy consisting of ASF1A inhibition and anti-PD-1 immunotherapy. SIGNIFICANCE: Using an in vivo epigenetic CRISPR screen, we identified Asf1a as a critical regulator of LUAD sensitivity to anti-PD-1 therapy. Asf1a deficiency synergized with anti-PD-1 immunotherapy by promoting M1-like macrophage polarization and T-cell activation. Thus, we provide a new immunotherapeutic strategy for this subtype of patients with LUAD.See related commentary by Menzel and Black, p. 179.This article is highlighted in the In This Issue feature, p. 161.
Subject(s)
Adenocarcinoma of Lung/drug therapy , Cell Cycle Proteins/metabolism , Drug Resistance, Neoplasm/genetics , Immune Checkpoint Inhibitors/pharmacology , Lung Neoplasms/drug therapy , Molecular Chaperones/metabolism , Adenocarcinoma of Lung/genetics , Adenocarcinoma of Lung/immunology , Adenocarcinoma of Lung/pathology , Animals , CRISPR-Cas Systems/genetics , Cell Cycle Proteins/genetics , Cell Differentiation/drug effects , Cell Differentiation/genetics , Cell Line, Tumor , Disease Models, Animal , Epigenesis, Genetic/immunology , Gene Expression Regulation, Neoplastic/immunology , Gene Knockout Techniques , HEK293 Cells , Humans , Immune Checkpoint Inhibitors/therapeutic use , Lung/pathology , Lung Neoplasms/genetics , Lung Neoplasms/immunology , Lung Neoplasms/pathology , Macrophages/drug effects , Macrophages/immunology , Macrophages/metabolism , Male , Mice , Molecular Chaperones/genetics , Programmed Cell Death 1 Receptor/antagonists & inhibitors , Programmed Cell Death 1 Receptor/immunology , Proto-Oncogene Proteins p21(ras)/genetics , RNA, Guide, Kinetoplastida/genetics , RNA, Small Interfering/metabolism , RNA-Seq , Tumor Microenvironment/drug effects , Tumor Microenvironment/immunology , Tumor Suppressor Protein p53/geneticsABSTRACT
Small cell lung cancer (SCLC) patient-derived xenografts (PDX) can be generated from biopsies or circulating tumor cells (CTC), though scarcity of tissue and low efficiency of tumor growth have previously limited these approaches. Applying an established clinical-translational pipeline for tissue collection and an automated microfluidic platform for CTC enrichment, we generated 17 biopsy-derived PDXs and 17 CTC-derived PDXs in a 2-year timeframe, at 89% and 38% efficiency, respectively. Whole-exome sequencing showed that somatic alterations are stably maintained between patient tumors and PDXs. Early-passage PDXs maintain the genomic and transcriptional profiles of the founder PDX. In vivo treatment with etoposide and platinum (EP) in 30 PDX models demonstrated greater sensitivity in PDXs from EP-naïve patients, and resistance to EP corresponded to increased expression of a MYC gene signature. Finally, serial CTC-derived PDXs generated from an individual patient at multiple time points accurately recapitulated the evolving drug sensitivities of that patient's disease. Collectively, this work highlights the translational potential of this strategy.Significance: Effective translational research utilizing SCLC PDX models requires both efficient generation of models from patients and fidelity of those models in representing patient tumor characteristics. We present approaches for efficient generation of PDXs from both biopsies and CTCs, and demonstrate that these models capture the mutational landscape and functional features of the donor tumors. Cancer Discov; 8(5); 600-15. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 517.
