CRISPR Screen of Druggable Targets in Small Cell Lung Cancer Identified ATM Inhibitor (AZD1390) as a Radiosensitizer.

PURPOSE: Small cell lung cancer (SCLC) is an aggressive and lethal form of lung cancer and the overall 5-year survival (OS) for patients is a dismal 7%. Radiation therapy (RT) provides some benefit for selected patients with SCLC but could be improved with radiosensitizing agents. In this study, we identified novel radiosensitizers for SCLC by a CRISPR-Cas9 screen and evaluated the efficacy of ATM inhibitor AZD1390 as a radiosensitizer of SCLC. METHODS AND MATERIALS: We transduced the SCLC cell line SBC5 with a custom CRISPR sgRNA library focused on druggable gene targets and treated cells with RT. Cells collected at multiple timepoints were subjected to next-generation sequencing. We determined radiosensitization both in vitro with cell lines assessed by short-term viability and clonogenic assays, and in vivo mouse models by tumor growth delay. Pharmacodynamic effects of AZD1390 were quantified by ATM-Ser1981 phosphorylation, and RT-induced DNA damage by comet assay. RESULTS: Using a CRISPR dropout screen, we identified multiple radiosensitizing genes for SCLC at various timepoints with ATM as a top determinant gene for radiosensitivity. Validation by ATM knockout (KO) demonstrated increased radiosensitivity by short-term viability assay (dose modification factor [DMF]50 = 3.25-3.73 in SBC5 ATM-KO) and clonogenic assays (DMF37 1.25-1.65 in SBC5 ATM-KO). ATM inhibition by AZD1390 effectively abrogated ATM Ser1981 phosphorylation in SCLC cell lines and increased RT-induced DNA damage. AZD1390 synergistically increased the radiosensitivity of SCLC cell lines (cell viability assay: SBC5 DMF37 = 2.19, SHP77 DMF37 = 1.56, H446 DMF37 = 3.27, KP1 DMF37 = 1.65 at 100nM; clonogenic assay: SBC5 DMF37 = 4.23, H1048 DMF37 = 1.91), and in vivo murine syngeneic, KP1, and patient-derived xenograft (PDX) models, JHU-LX108 and JHU-LX33. CONCLUSIONS: In this study, we demonstrated that genetically and pharmacologically (AZD1390) inhibiting ATM markedly enhanced RT against SCLC, providing a novel pharmacologically tractable radiosensitizing strategy for patients with SCLC.

SARS-CoV-2 impairs interferon production via NSP2-induced repression of mRNA translation.

Viruses evade the innate immune response by suppressing the production or activity of cytokines such as type I interferons (IFNs). Here we report the discovery of a mechanism by which the SARS-CoV-2 virus coopts an intrinsic cellular machinery to suppress the production of the key immunostimulatory cytokine IFN-ß. We reveal that the SARS-CoV-2 encoded nonstructural protein 2 (NSP2) directly interacts with the cellular GIGYF2 protein. This interaction enhances the binding of GIGYF2 to the mRNA cap-binding protein 4EHP, thereby repressing the translation of the Ifnb1 mRNA. Depletion of GIGYF2 or 4EHP significantly enhances IFN-ß production, which inhibits SARS-CoV-2 replication. Our findings reveal a target for rescuing the antiviral innate immune response to SARS-CoV-2 and other RNA viruses.

PARP inhibitors for small cell lung cancer and their potential for integration into current treatment approaches.

Small cell lung cancer (SCLC) is a very aggressive, highly lethal, neuroendocrine tumor that constitutes 15% of all lung cancer cases. It is characterized by its rapid disease progression and high relapse rate leading to poor survival for diagnosed patients. Recently, poly (ADP-ribose) polymerase inhibitors (PARPi) have emerged as a novel therapeutic strategy for SCLC. Preclinical studies have demonstrated that PARPi possesses cytotoxic activity as a single-agent and in combination with other anti-cancer agents. Predictive biomarkers of response to PARPi, such as SLFN11, have also been described in SCLC. This review aims to summarize the recent preclinical investigations and the relevant clinical trials that evaluate PARPi in SCLC. Here, we highlight the potential role of PARPi in a biomarker-selected manner and in combination with chemotherapy, targeted agents, radiotherapy and immunotherapy.

Characterization of the Role of Host Cellular Factor Histone Deacetylase 10 during HIV-1 Replication.

To date, a series of histone deacetylases have been documented to restrict HIV-1 replication at different steps. In this study, we identified histone deacetylase 10 (HDAC10) as an inhibitory factor against HIV-1 replication. Our results showed that endogenous HDAC10 is downregulated at the transcriptional level during HIV-1 replication. By knocking down HDAC10 in CD4+ T cells with specific shRNAs, we observed that the downregulation of HDAC10 significantly facilitates viral replication. Moreover, RQ-PCR analysis revealed that the downregulation of HDAC10 increased viral integrated DNA. Further, we identified that HDAC10 interacts with the HIV-1 integrase (IN) and that the region of residues from 55 to 165 in the catalytic domain of IN is required for HDAC10 binding. Interestingly, we found that the interaction between HDAC10 and IN specifically decreases the interaction between IN and cellular protein lens epithelium-derived growth factor (LEDGF/p75), which consequently leads to the inhibition of viral integration. In addition, we have investigated the role of HDAC10 in the late stage of viral replication by detecting the infectiousness of progeny virus produced from HDAC10 knockdown cells or HDAC10 overexpressing cells and revealed that the progeny virus infectivity is increased in the HDAC10 downregulated cells, but decreased in the HDAC10 overexpressed cells. Overall, these findings provide evidence that HDAC10 acts as a cellular inhibitory factor at the early and late stages of HIV-1 replication.

HIV-1 envelope glycoprotein stimulates viral transcription and increases the infectivity of the progeny virus through the manipulation of cellular machinery.

During HIV infection, large amounts of progeny viral particles, including infectious virus and a large proportion of defective viral particles, are produced. Despite of the critical role of the infectious viruses in infection and pathogenesis in vivo, whether and how those defective viral particles, especially the virus-associated envelope glycoprotein (vEnv), would impact viral infection remains elusive. In this study, we investigated the effect of vEnv on HIV-infected T cells and demonstrated that the vEnv was able to stimulate HIV transcription in HIV-infected cells, including peripheral blood mononuclear cells (PBMCs) isolated from HIV patients. This vEnv-mediated HIV transcription activation is mediated primarily through the interaction between vEnv and CD4/coreceptors (CCR5 or CXCR4). Through transcriptome analysis, we found that numerous cellular gene products involved in various signaling pathways were modulated by vEnv. Among them, we have further identified a cellular microRNA miR181A2, which is downregulated upon vEnv treatment, resulting in increased HIV LTR histone H3 acetylation and HIV transcription. Furthermore, we also found a vEnv-modulated cellular histone deacetylase, HDAC10, whose downregulation is associated with the increased infectivity of progeny viruses. Altogether, these findings provide evidence of the important role vEnv plays in modulating cellular environments and facilitating HIV expression and infection.

Apobec3G-Based Strategies to Defeat HIV Infection.

BACKGROUND: To suppress HIV infection, host cells have evolved numerous defenses that generally belong to the innate and adaptive immune responses. Over the last decade, extensive efforts have been focused on understanding HIV restriction factors and mechanisms of evasion. The host protein APOBEC3G (A3G) was identified as a member of cytidine deaminase family in 2002, and it was shown that, in the absence of HIV encoded Vif, A3G can block the replication of HIV-1 by introducing viral hypermutations during reverse transcription, also conferring innate immunity to the virus. Hence, therapeutic exploitation of A3G as an antiviral therapy has received an increasing amount of attention. Recent studies have developed a series of strategies to abolish the interaction between Vif and A3G or facilitate A3G expression, thus enhancing active A3G formation and delivering A3G into virion. CONCLUSION: Here we present a review that discuss the role of A3G as a host innate immunity factor and its application in HIV therapy.

Characterization of the inhibitory effect of an extract of Prunella vulgaris on Ebola virus glycoprotein (GP)-mediated virus entry and infection.

Currently, no approved antiviral therapeutic is available for treatment or prevention of Ebola virus (EBOV) infection. In this study, we characterized an EBOV-glycoprotein (GP) pseudotyped HIV-1-based vector system in different cell cultures, including human umbilical vein endothelial cells (HUVECs) and human macrophages, for the screening of anti-EBOV-GP agent(s). Based on this system, we demonstrated that an aqueous extract (CHPV) from the Chinese herb Prunella vulgaris displayed a potent inhibitory effect on EBOV-GP pseudotyped virus (EBOV-GP-V)-mediated infection in various cell lines, including HUVEC and macrophage. In addition, our results indicated that CHPV was able to block an eGFP-expressing Zaire ebola virus (eGFP-ZEBOV) infection in VeroE6 cells. The anti-EBOV activity of CHPV was exhibited in a dose-dependent manner. At a 12.5 µg/ml concentration, the CHPV showed a greater than 80% inhibition of EBOV-GP-V and eGFP-EBOV infections. Likewise, our studies suggested that the inhibitory effect of CHPV occurred by binding directly to EBOV-GP-Vs and blocking the early viral events. Interestingly, our results have shown that CHPV was able to enhance the anti-EBOV activity of the monoclonal antibody MAb 2G4 against EBOV-GP. Overall, this study provides evidence that CHPV has anti-EBOV activity and may be developed as a novel antiviral approach against EBOV infection.

White spot syndrome virus IE1 and WSV056 modulate the G1/S transition by binding to the host retinoblastoma protein.

DNA viruses often target cellular proteins to modulate host cell cycles and facilitate viral genome replication. However, whether proliferation of white spot syndrome virus (WSSV) requires regulation of the host cell cycle remains unclear. In the present study, we show that two WSSV paralogs, IE1 and WSV056, can interact with Litopenaeus vannamei retinoblastoma (Rb)-like protein (lv-RBL) through the conserved LxCxE motif. Further investigation revealed that IE1 and WSV056 could also bind to Drosophila retinoblastoma family protein 1 (RBF1) in a manner similar to how they bind to lv-RBL. Using the Drosophila RBF-E2F pathway as a model system, we demonstrated that both IE1 and WSV056 could sequester RBF1 from Drosophila E2F transcription factor 1 (E2F1) and subsequently activate E2F1 to stimulate the G1/S transition. Our findings provide the first evidence that WSSV may regulate cell cycle progression by targeting the Rb-E2F pathway.