A sub-population of chemoresistant cells exhibits biological properties similar to cancer stem cells (CSCs), and these cells are believed to be a main cause for tumor relapse and metastasis. In our study, we explored the role of SOX8 and its molecular mechanism in the regulation of the stemness properties and the epithelial mesenchymal transition (EMT) of cisplatin-resistant tongue squamous cell carcinoma (TSCC) cells. We found that SOX8 was upregulated in cisplatin-resistant TSCC cells, which displayed CSC-like properties and exhibited EMT. SOX8 was also overexpressed in chemoresistant patients with TSCC and was associated with higher lymph node metastasis, advanced tumor stage and shorter overall survival. Stable knockdown of SOX8 in cisplatin-resistant TSCC cells inhibited chemoresistance, tumorsphere formation, and EMT. The Wnt/β-catenin pathway mediated the cancer stem-like properties in cisplatin-resistant TSCC cells. Further studies showed that the transfection of active β-catenin in SOX8 stable-knockdown cells partly rescued the SOX8 silencing-induced repression of stem-like features and chemoresistance. Through chromatin immunoprecipitation and luciferase assays, we observed that SOX8 bound to the promoter region of Frizzled-7 (FZD7) and induced the FZD7-mediated activation of the Wnt/β-catenin pathway. In summary, SOX8 confers chemoresistance and stemness properties and mediates EMT processes in chemoresistant TSCC via the FZD7-mediated Wnt/β-catenin pathway.

Cervical cancer is the most common cause of female cancer‐related mortality worldwide. Decreased expression of long noncoding RNA growth arrest‐specific 5 (GAS5) is found in human cervical cancer tissues and associated with poor prognosis. However, the studies on associations between GAS5 level and malignant phenotypes, as well as sensitivity to chemotherapeutic drug in cervical cancer cells are limited. In this study, overexpression of GAS5 in cervical cancer cells resulted in prohibited cell proliferation and colony formation, which were promoted by siGAS5. Enhanced GAS5 increased cell percentage in the G0/G1 phase and decreased cells percentage in the S phase, whereas reduced expression did not. The malignant behaviors of cervical cancer cells, manifested by cell migration and invasion, could be weakened by the GAS5 overexpression and enhanced by siGAS5. Furthermore, in cisplatin‐induced cell, overexpression of GAS5 reduced cells viability and enhanced apoptosis, whereas in cells transfected with siGAS5, apoptosis eliminated. We have reported the upregulation of microRNA‐21 (miR‐21) and its oncogenetic roles in cervical cancer previously. In this study, we found the negative relationship between the GAS5 and miR‐21. Moreover, the decrease of miR‐21 associated proteins phosphorylated STAT3 and E2F3 was seen in GAS5 overexpressed cells, both of which could be increased by siGAS5. The GAS5 deficiency also reduced miR‐21 target proteins TIMP3 and PDCD4 expressions. Taken together, the GAS5 expression level is inversely associated with malignancy, but positively associated with sensitivity to cisplatin‐induced apoptosis, suggesting that GAS5 could be a biomarker of cisplatin‐resistance in clinical therapy of human cervical cancer.

Galectin-3 (Gal-3) has been found to be involved in the tumor progression and chemoresistance of epithelial ovarian cancer (EOC). Some studies have shown that Gal-3 may interact with nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). However, it is unclear whether the effects of Gal-3 on the metastasis and chemosensitivity of EOC are related to NF-κB. In this study, we aimed to explore whether Gal-3 promoted progression and carboplatin resistance in EOC via NF-κB pathway. Plasmid transfection and RNA interference were used to upregulate or downregulate the expression of Gal-3 in ovarian cancer cell lines. Then, the expression of Gal-3 and the protein expressions of phosphorylation NF-κB pathway molecules were further detected by Western blot. Transwell migration assay was employed to detect the effects of Gal-3 on the migration and invasion of ovarian cancer cell lines. After treatment with carboplatin, flow cytometry (FCM) was employed to detect the effects of Gal-3 on carboplatin-induced apoptosis. Immunofluorescence technique was used to examine the translocation of phosphorylated P65 into the nucleus in ovarian cancer cells after the upregulation of Gal-3. After the knockdown of Gal-3 by small interfering RNA (siRNA), the migration and the invasion of cancer cells were significantly inhibited while the apoptosis and the sensitivities to carboplatin increased. Western blot showed reduction in the phosphorylation components of the NF-κB pathway: inhibitor of kappa B (IκB), IκB kinase (IKK), and P65. However, after the Gal-3 upregulation by plasmid transfection, the capabilities of migration and invasion of cancer cells were significantly promoted while the apoptosis and the sensitivities to carboplatin decreased. Immunofluorescence showed increased nuclear translocation of P65. Inhibitors of the NF-κB pathway did not affect the Gal-3 expression level in ovarian cancer cells. Gal-3 may affect the migratory and invasive capabilities of cancer cells as well as the chemosensitiviy to carboplatin in EOC by acting through the NF-κB pathway.

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