Telocinobufagin, a PLK1 suppressor that inhibits tumor growth and metastasis by modulating CDC25c and CTCF in HNSCC cells.

BACKGROUND: The high metastasis and mortality rates of head and neck squamous cell carcinoma (HNSCC) urgently require new treatment targets and drugs. A steroidal component of ChanSu, telocinobufagin (TBG), was verified to have anti-cancer effects in various tumors, but its activity and mechanism in anti-HNSCC were still unknown.

PURPOSE: This study tried to demonstrate the anti-tumor effect of TBG on HNSCC and verify its potential mechanism.

METHODS: The effect of TBG on cell proliferation and metastasis were performed and the TBG changed genes were detected by RNA-seq analysis in HNSCC cells. The GSEA and PPI analysis were used to identify the pathways targeted for TBG-regulated genes. Meanwhile, the mechanism of TBG on anti-proliferative and anti-metastasis were investigated in vitro and in vivo.

RESULTS: The in vitro and in vivo experiments confirmed that TBG has favorable anti-tumor effects by induced G2/M phase arrest and suppressed metastasis in HNSCC cells. Further RNA-seq analysis demonstrated the genes regulated by TBG were enriched at the G2/M checkpoint and PLK1 signaling pathway. Then, the bioinformatic analysis of clinical data found that high expressed PLK1 were closely associated with poor overall survival in HNSCC patients. Furthermore, PLK1 directly and indirectly modulated G2/M phase and metastasis (by regulated CTCF) in HNSCC cells, simultaneously. TBG significantly inhibited the protein levels of PLK1 in both phosphorylated and non-phosphorylated forms and then, in one way, inactivated PLK1 failed to activate G2/M phase-related proteins (including CDK1, CDC25c, and cyclin B1). In another way, be inhibited PLK1 unable promote the nuclear translocation of CTCF and thus suppressed HNSC cell metastasis. In contrast, the anti-proliferative and anti-metastasis effects of TBG on HNSCC cell were vanished when cells high-expressed PLK1.

CONCLUSION: The present study verified that PLK1 mediated TBG induced anti-tumor effect by modulated G2/M phase and metastasis in HNSCC cells.