Non-small-cell lung carcer (NSCLC), the main histological subtype of lung cancer, is responsible for significant morbidity and mortality worldwide. Telocinobufagin, an active compound of the Chinese traditional medicine ChanSu, has antitumor effects, but its mechanism of action remains unknown. Therefore, we investigated the effect of telocinobufagin on NSCLC growth and metastasis and its possible mechanism of action, in vitro and in vivo. Cell proliferation, migration, and apoptosis were measured by methyl thiazol tetrazolium assay, colony formation, 5-ethynyl-2′-deoxyuridine incorporation, Transwell migration, wound healing, and flow cytometry analysis. A mouse xenograft model was used to evaluate tumor formation in vivo. Telocinobufagin was found to suppress proliferation and metastasis and induce apoptosis in human NSCLC cells. Moreover, telocinobufagin was able to significantly inhibit STAT3 phosphorylation at tyrosine 705 (Y 705 ) and its downstream targets. Additionally, telocinobufagin also impaired the IL-6-induced nuclear translocation of STAT3. Consistent with the in vitro experiments, telocinobufagin reduced the A549 xenograft tumor burden and the levels of P-STAT3 Y705 , MCL1, BCL2, and cleaved PARP1 in vivo. These results support telocinobufagin as a promising STAT3 signaling inhibitor candidate for the treatment of NSCLC patients.

Cyclin-dependent kinase (CDK) 9 associates mainly with cyclin T1 and forms the positive transcription elongation factor b (p-TEFb) complex responsible for transcriptional regulation. It has been shown that CDK9 modulates the expression and activity of oncogenes, such as MYC and murine double minute 4 (MDM4), and it also plays an important role in development and/or maintenance of the malignant cell phenotype. Malfunction of CDK9 is frequently observed in numerous cancers. Recent studies have highlighted the function of CDK9 through a variety of mechanisms in cancers, including the formation of new complexes and epigenetic alterations. Due to the importance of CDK9 activation in cancer cells, CDK9 inhibitors have emerged as promising candidates for cancer therapy. Natural product-derived and chemically synthesized CDK9 inhibitors are being examined in preclinical and clinical research. In this review, we summarize the current knowledge on the role of CDK9 in transcriptional regulation, epigenetic regulation, and different cellular factor interactions, focusing on new advances. We show the importance of CDK9 in mediating tumorigenesis and tumor progression. Then, we provide an overview of some CDK9 inhibitors supported by multiple oncologic preclinical and clinical investigations. Finally, we discuss the perspective and challenge of CDK9 modulation in cancer.