thiostrepton and Carcinoma--Non-Small-Cell-Lung

Topics: Animals; Carcinoma, Non-Small-Cell Lung; CASP8 and FADD-Like Apoptosis Regulating Protein; Cell Line, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Forkhead Box Protein M1; Forkhead Transcription Factors; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Mice; Thiostrepton

Programmed death-ligand 1 (PD-L1) is a major target to cancer immunotherapy, and anti-PD-L1 and anti-PD-1 antibody-mediated immunotherapy are being increasingly used. However, immune checkpoint inhibitors (ICIs) are ineffective in treating large tumors and cause various immune-related adverse events in nontarget organs, including life-threatening cardiotoxicity. Therefore, the development of new therapeutic strategies to overcome these limitations is crucial. The focus of this study is the forkhead box protein M1 (FOXM1), which is identified as a potential therapeutic target for cancer immunotherapy and is associated with the modulation of PD-L1 expression. Selective small interfering RNA knockdown of FOXM1 or treatment with thiostrepton (TST) significantly reduces PD-L1 expression in non-small-cell lung cancer (NSCLC) cells and inhibits proliferation. Chromatin immunoprecipitation-PCR reveals that FOXM1 selectively upregulates PD-L1 expression by binding directly to the PD-L1 promoter. In vivo animal studies have shown that TST treatment significantly downregulates PD-L1 expression in human NSCLC tumors, while greatly reducing tumor size without side effects on normal tissues. Combined treatment with TST and anti-4-1BB antibody in the LLC-1 syngeneic tumor model induces synergistic therapeutic outcomes against immune resistant lung tumors as well as 2.72-folds higher CD3

Topics: Animals; B7-H1 Antigen; Carcinoma, Non-Small-Cell Lung; Cell Proliferation; Forkhead Box Protein M1; Humans; Immune Checkpoint Inhibitors; Immunotherapy; Lung Neoplasms; Programmed Cell Death 1 Receptor; RNA, Small Interfering; Thiostrepton; Treatment Outcome

Cancer stem cells (CSCs) play an important role in cancer treatment resistance and disease progression. Identifying an effective anti-CSC agent may lead to improved disease control. We used CSC-associated gene signatures to identify drug candidates that may inhibit CSC growth by reversing the CSC gene signature. Thiostrepton, a natural cyclic oligopeptide antibiotic, was the top-ranked candidate. In non-small-cell lung cancer (NSCLC) cells, thiostrepton inhibited CSC growth in vitro and reduced protein expression of cancer stemness markers, including CD133, Nanog and Oct4A. In addition, metastasis-associated Src tyrosine kinase signalling, cell migration and epithelial-to-mesenchymal transition (EMT) were all inhibited by thiostrepton. Mechanistically, thiostrepton treatment led to elevated levels of tumour suppressor miR-98. Thiostrepton combined with gemcitabine synergistically suppressed NSCLC cell growth and induced apoptosis. The inhibition of NSCLC tumours and CSC growth by thiostrepton was also demonstrated in vivo. Our findings indicate that thiostrepton, an established drug identified in silico, is an inhibitor of CSC growth and a potential enhancer of chemotherapy in NSCLC.

Topics: A549 Cells; Animals; Anti-Bacterial Agents; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Computer Simulation; Epithelial-Mesenchymal Transition; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Mice, Inbred NOD; Mice, SCID; MicroRNAs; Nanog Homeobox Protein; Neoplastic Stem Cells; Signal Transduction; Thiostrepton; Xenograft Model Antitumor Assays