An optimized NGS sample preparation protocol for in vitro CRISPR screens

Optimized protocol to generate genome-wide inactivated Cas9-expressing murine T cells

In vivo genome-wide CRISPR screens in primary T cells allow the systematic and unbiased identification of non-redundant regulatory mechanisms shaping immune responses. Here, we present an optimized protocol for efficient generation of a pool of genome-wide inactivated Cas9-expressing T cells using a retroviral library of sgRNA. We detail the process of large-scale viral production and library integration in activated murine T cells as well as the two-step PCR approach for sgRNA recovery and abundance evaluation. For complete details on the use and execution of this protocol, please refer to Sutra Del Galy et al. (2020).

Inhibition of XPO1 Sensitizes Small Cell Lung Cancer to First- and Second-Line Chemotherapy

Small cell lung cancer (SCLC) is an aggressive malignancy characterized by early metastasis and extreme lethality. The backbone of SCLC treatment over the past several decades has been platinum-based doublet chemotherapy, with the recent addition of immunotherapy providing modest benefits in a subset of patients. However, nearly all patients treated with systemic therapy quickly develop resistant disease, and there is an absence of effective therapies for recurrent and progressive disease. Here we conducted CRISPR-Cas9 screens using a druggable genome library in multiple SCLC cell lines representing distinct molecular subtypes. This screen nominated exportin-1, encoded by XPO1, as a therapeutic target. XPO1 was highly and ubiquitously expressed in SCLC relative to other lung cancer histologies and other tumor types. XPO1 knockout enhanced chemosensitivity, and exportin-1 inhibition demonstrated synergy with both first- and second-line chemotherapy. The small molecule exportin-1 inhibitor selinexor in combination with cisplatin or irinotecan dramatically inhibited tumor growth in chemonaïve and chemorelapsed SCLC patient-derived xenografts, respectively. Together these data identify exportin-1 as a promising therapeutic target in SCLC, with the potential to markedly augment the efficacy of cytotoxic agents commonly used in treating this disease. SIGNIFICANCE: CRISPR-Cas9 screening nominates exportin-1 as a therapeutic target in SCLC, and exportin-1 inhibition enhances chemotherapy efficacy in patient-derived xenografts, providing a novel therapeutic opportunity in this disease.