Ciprofloxacin (CIP) is a potent antimicrobial agent with multiple effects on host cells and tissues. Previous studies have highlighted their proapoptotic effect on human cancer cells. The current study showed that subtoxic doses of CIP effectively sensitized multiple cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Although TRAIL alone mediated the partial proteolytic processing of procaspase-3 in lung cancer cells, co-treatment with CIP and TRAIL efficiently restored the complete activation of caspases. We found that treatment of lung cancer with CIP significantly upregulated the expression and protein stability of death receptor (DR) 5. These effects were mediated through the regulation of transcription factor CCAT enhancer-binding protein homologous protein (CHOP) since the silencing of these signaling molecules abrogated the effect of CIP. Taken together, these results indicated that the upregulation of death receptor expression and protein stability by CIP contributed to the restoration of TRAIL-sensitivity in lung cancer cells.

Tristetraprolin (TTP), a well-characterized AU-rich element (ARE) binding protein, functions as a tumor suppressor gene. The purpose of this study was to investigate whether a bioactive substance derived from a natural medicinal plant affects the induction of TTP and to elucidate its mechanism. We examined the effects of natural bioactive materials including Resveratrol (RSV), thymoquinone (TQ) and curcumin on the expression of TTP in cancer cell. TQ derived from a natural plant Nigella sativa increased the expression levels of TTP mRNA and proteins in a dose-dependent manner in gastric and breast cancer cells. TQ-induced TTP increased the instability of MUC4 mRNA by direct binding of TTP to ARE in the 3′UTR of MUC4 mRNA. The induction of TTP by TQ also reduced the proliferation, migration and invasion of cancer cells. The expression of the epithelial-mesenchymal (EMT)-related genes, which were target genes of TTP, was also decreased by the TQ treatment. In the in vivo experiments using mouse melanoma cells, TQ-induced TTP inhibited metastasis of tumor cells. We have found that TQ-induced TTP might inhibit metastasis by reducing tumor cell migration and invasion through destabilization of MUC4 mRNA, which suggest the MUC4 as a novel target to TTP.

Purpose To investigate the role of neuregulin (NRG) signaling in promoting head and neck squamous cell carcinoma (HNSCC) migration through HER3-dependent pathways and to assess the therapeutic potential of targeting the NRG/HER3 axis in mitigating perineural invasion. Methods NRG-driven migration was studied using DRG co-culture, wound healing assays, and HER3 inhibition (shRNA, AV-203). The biological function and biochemical effects of the HER3/HER2/FAK axis in response to NRG were analyzed via phosphorylation assays, knockdown, western blotting, and cell staining for protein expression. Results NRG promoted directional migration of FaDu and TU138 HNSCC cells through HER3/HER2 and HER3/PI3K interactions. HER3 inhibition (shRNA or AV-203) abolished HER3 phosphorylation, disrupted HER3-HER2 interactions, and suppressed AKT and ERK signaling. Wound healing assays confirmed that NRG enhances migration via HER3 activation. NRG also induced HER3-dependent FAK phosphorylation, and FAK knockdown or inhibition with PF228 significantly reduced NRG-driven migration, highlighting the critical role of HER3-FAK signaling. Conclusion NRG promotes HNSCC cell migration by activating HER3, forming HER3-HER2 and HER3-FAK complexes, and driving downstream AKT, ERK, and FAK signaling. Targeting the NRG/HER3 axis holds potential as a therapeutic strategy to address perineural invasion and associated clinical challenges in HNC.