TBOPP, a DOCK1 Inhibitor, Potentiates Cisplatin Efficacy in Breast Cancer by Regulating Twist-mediated EMT.

BACKGROUND: DOCK1 has been reported to be involved in tumor progression and resistance. 1-(2-(30-(trifluoromethyl)-[1,10-biphenyl]-4-yl)-2-oxoethyl)-5-pyrrolidinylsulfonyl2(1H)- pyridone (TBOPP) is a selective DOCK1 inhibitor; however, the role and molecular mechanisms of DOCK1 and its inhibition in breast cancer (BC) resistance remain poorly understood. OBJECTIVE: This study aims toinvestigate the underlying mechanisms of DOCK1 in BC resistance. METHODS: DOCK1 or Twist siRNA and Twist plasmid were used to explore the function of DOCK1 in vitro experiments. A mouse xenograft model was used for in vivo experiments. RESULTS: In the present study, we demonstrated that DOCK1 siRNA promoted cisplatin sensitivity in BC cells. Moreover, TBOPP also enhances the therapeutic effect of cisplatin both in vitro and in vivo. Mechanistically, DOCK1 siRNA inhibited EMT. Twist 1 is one of the EMT-inducing transcription factors and is known to induce EMT. To further reveal the effect of DOCK in BC cells, we co-transfected with DOCK1 and Twist1 siRNA to BC cells and found that co-transfection with DOCK1 and Twist siRNA could not further enhance the cisplatin sensitivity of BC cells. Moreover, DOCK1 siRNA failed to reverse the effect of Twist 1 up-regulation. CONCLUSION: Taken together, these results demonstrate that DOCK1 may function as a potential therapeutic target in BC and that combining cisplatin with TBOPP may provide a promising therapeutic strategy for cisplatin-resistant BC patients.

TRAF3 activates STING-mediated suppression of EV-A71 and target of viral evasion.

Innate immunity represents one of the main host responses to viral infection.1-3 STING (Stimulator of interferon genes), a crucial immune adapter functioning in host cells, mediates cGAS (Cyclic GMP-AMP Synthase) sensing of exogenous and endogenous DNA fragments and generates innate immune responses.4 Whether STING activation was involved in infection and replication of enterovirus remains largely unknown. In the present study, we discovered that human enterovirus A71 (EV-A71) infection triggered STING activation in a cGAS dependent manner. EV-A71 infection caused mitochondrial damage and the discharge of mitochondrial DNA into the cytosol of infected cells. However, during EV-A71 infection, cGAS-STING activation was attenuated. EV-A71 proteins were screened and the viral protease 2Apro had the greatest capacity to inhibit cGAS-STING activation. We identified TRAF3 as an important factor during STING activation and as a target of 2Apro. Supplement of TRAF3 rescued cGAS-STING activation suppression by 2Apro. TRAF3 supported STING activation mediated TBK1 phosphorylation. Moreover, we found that 2Apro protease activity was essential for inhibiting STING activation. Furthermore, EV-D68 and CV-A16 infection also triggered STING activation. The viral protease 2Apro from EV-D68 and CV-A16 also had the ability to inhibit STING activation. As STING activation prior to EV-A71 infection generated cellular resistance to EV-A71 replication, blocking EV-A71-mediated STING suppression represents a new anti-viral target.

DNA virus oncoprotein HPV18 E7 selectively antagonizes cGAS-STING-triggered innate immune activation.

Cellular infections by DNA viruses trigger innate immune responses mediated by DNA sensors. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway has been identified as a DNA-sensing pathway that activates interferons in response to viral infection and, thus, mediates host defense against viruses. Previous studies have identified oncogenes E7 and E1A of the DNA tumor viruses, human papillomavirus 18 (HPV18) and adenovirus, respectively, as inhibitors of the cGAS-STING pathway. However, the function of STING in infected cells and the mechanism by which HPV18 E7 antagonizes STING-induced Interferon beta production remain unknown. We report that HPV18 E7 selectively antagonizes STING-triggered nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation but not IRF3 activation. HPV18 E7 binds to STING in a region critical for NF-κB activation and blocks the nuclear accumulation of p65. Moreover, E7 inhibition of STING-triggered NF-κB activation is related to HPV pathogenicity but not E7-Rb binding. HPV18 E7, severe acute respiratory syndrome coronavirus-2 open reading frame 3a, human immunodeficiency virus-2 viral protein X, and Kaposi's sarcoma-associated herpesvirus KSHV viral interferon regulatory factor 1 selectively inhibited STING-triggered NF-κB or IRF3 activation, suggesting a convergent evolution among these viruses toward antagonizing host innate immunity. Collectively, selective suppression of the cGAS-STING pathway by viral proteins is likely to be a key pathogenic determinant, making it a promising target for treating oncogenic virus-induced tumor diseases.

HIV-2/SIV Vpx targets a novel functional domain of STING to selectively inhibit cGAS-STING-mediated NF-κB signalling.

Innate immunity is the first line of host defence against pathogens. Suppression of innate immune responses is essential for the survival of all viruses. However, the interplay between innate immunity and HIV/SIV is only poorly characterized. We have discovered Vpx as a novel inhibitor of innate immune activation that associates with STING signalosomes and interferes with the nuclear translocation of NF-κB and the induction of innate immune genes. This new function of Vpx could be separated from its role in mediating degradation of the antiviral factor SAMHD1, and is conserved among diverse HIV-2/SIV Vpx. Vpx selectively suppressed cGAS-STING-mediated nuclear factor-κB signalling. Furthermore, Vpx and Vpr had complementary activities against cGAS-STING activity. Since SIVMAC lacking both Vpx and Vpr was less pathogenic than SIV deficient for Vpr or Vpx alone, suppression of innate immunity by HIV/SIV is probably a key pathogenic determinant, making it a promising target for intervention.