The αPD-L1 antibody-based immune checkpoint blockade therapy is still limited by the poor clinical response rate as it is mainly utilized to block surface PD-L1 on tumor cells while ignoring abundant PD-L1 exosomes secreted in the environment, causing tumor immune evasion. Here, we proposed an exosome biogenesis inhibition strategy to suppress tumor exosomes secretion from the source, reducing the inhibitory effect on T cells and enhancing chemo-immunotherapy efficacy. We developed sulfafurazole homodimers (SAS) with disulfide linkages, effectively releasing the drug in response to glutathione (GSH) and inhibiting 4T1 tumor-derived exosomes secretion. Subsequently, gemcitabine (Gem) was encapsulated to induce immunogenic cell death (ICD). Consequently, Gem@SAS inhibited the secretion of tumor exosomes by more than 70%, increased proliferation and granzyme B secretion ability of T cells by more than 2 times, and showed superior efficacy in breast cancer treatment as well as lung metastasis of breast cancer.

The emergence of SARS-CoV-2 variants of concern and repeated outbreaks of coronavirus epidemics in the past two decades emphasize the need for next-generation pan-coronaviral therapeutics. Drugging the multi-functional papain-like protease (PLpro) domain of the viral nsp3 holds promise. However, none of the known coronavirus PLpro inhibitors has been shown to be in vivo active. Herein, we screened a structurally diverse library of 50,080 compounds for potential coronavirus PLpro inhibitors and identified a noncovalent lead inhibitor F0213 that has broad-spectrum anti-coronaviral activity, including against the Sarbecoviruses (SARS-CoV-1 and SARS-CoV-2), Merbecovirus (MERS-CoV), as well as the Alphacoronavirus (hCoV-229E and hCoV-OC43). Importantly, F0213 confers protection in both SARS-CoV-2-infected hamsters and MERS-CoV-infected human DPP4-knockin mice. F0213 possesses a dual therapeutic functionality that suppresses coronavirus replication via blocking viral polyprotein cleavage, as well as promoting antiviral immunity by antagonizing the PLpro deubiquitinase activity. Despite the significant difference of substrate recognition, mode of inhibition studies suggest that F0213 is a competitive inhibitor against SARS2-PLpro via binding with the 157K amino acid residue, whereas an allosteric inhibitor of MERS-PLpro interacting with its 271E position. Our proof-of-concept findings demonstrated that PLpro is a valid target for the development of broad-spectrum anti-coronavirus agents. The orally administered F0213 may serve as a promising lead compound for combating the ongoing COVID-19 pandemic and future coronavirus outbreaks.
Animals ; Coronavirus Papain-Like Proteases/antagonists & inhibitors* ; Cricetinae ; Humans ; Mice ; Pandemics ; SARS-CoV-2/enzymology* ; COVID-19 Drug Treatment

Aim To investigate the effect and mecha-nism of quercetin combined with cisplatin on prolifera-tion and apoptosis of human osteosarcoma cell line MG-63 . Methods MG-63 cells were treated with quercetin alone or combined with cisplatin. Cellular morphologic changes were observed under inverted phase contrast microscope. The effects of proliferation inhibition were assayed by CCK-8 method. The combination effect was judged through Chou-Talaly analysis. The apoptosis ra-tios of cells were analyzed by flow cytometry. The gene expression of Bcl-2 and caspase-3 was detected by RT-PCR assay. The protein expression of Bcl-2 and caspase-3 was measured by Western blot assay. Re-sults Quercetin alone or combined with cisplatin could inhibit the proliferation, but induce the apoptosis of MG-63 cells. Combination of quercetin and cisplatin revealed a synergistic effect on cell proliferation and apoptosis as it reduced the expression of Bcl-2 but en-hanced that of caspase-3 at both gene and protein lev-els. Conclusion Synergistic effect of quercetin com-bined with cisplatin on cell proliferation and apoptosis of MG-63 cells is possibly due to reduction of Bcl-2 and enhancement of caspase-3 expression.