Transcriptional factor six2 promotes the competitive endogenous RNA network between CYP4Z1 and pseudogene CYP4Z2P responsible for maintaining the stemness of breast cancer cells

Transcription factor Six2 induces a stem cell-like phenotype in renal cell carcinoma cells

Renal cell carcinoma (RCC) accounts for 2-3% of adult malignant tumors, and the incidence of RCC worldwide has increased by about 2% over the past two decades. The homeobox protein Six2 has been shown to promote the stemness of breast cancer cells and play a role in kidney development, but its involvement in RCC progression has not previously been investigated. Here, we found that six2 expression was significantly increased in RCC tissues and negatively correlated with the overall survival of patients with RCC. In addition, six2 expression exhibited a remarkably higher level relative to that in normal renal cells. Functional experiments showed that six2 knockdown attenuated the stemness of RCC cells, which was evident by decreased spheroid formation ability and stemness marker (sox2 and nanog) expression. Mechanistic studies indicated that Six2 directly bound to the enhancer of sox2, promoting sox2 expression and downstream effector expression of nanog. Furthermore, overexpression of sox2 rescued the inhibitory effects of six2 on the stemness of RCC cells. Notably, six2 expression is positively correlated with sox2 and nanog expression in RCC tissues. Collectively, our results point toward a six2/sox2 axis responsible for RCC cell stemness.

Six1 is negatively correlated with poor prognosis and reduces 5-fluorouracil sensitivity via attenuating the stemness of hepatocellular carcinoma cells

The promoting roles of transcriptional factor six1 have been shown in various tumors, such as breast cancer and colorectal Cancer. However, its roles in hepatocellular carcinoma (HCC) cell stemness and chemotherapeutic sensitivity are never been revealed. In the present study, we showed that six1 expression was negatively correlated the overall survival of HCC patients and significantly increased in HCC tissues. Analysis on normal hepatic cells and HCC cells obtained the consistent result. Functional experiments revealed that six1 knockdown enhanced 5-fluorouracil (5-FU) sensitivity and reduced the stemness of HCC cells. Additionally, six1 knockdown partially reversed 5-FU resistance and attenuated the stemness in 5-FU-resistant HCC cells. Furthermore, we demonstrated that six1 directly bound to sox2 (a stemness master regulator) promoter, enhanced its transcription and expression. Overexpression of sox2 rescued the inhibitory effects of six1 knockdown on the stemness and 5-FU sensitivity of HCC cells. Thus, our work identified a novel six1/sox2 axis in regulating the stemness of HCC cells.

Six2 promotes non-small cell lung cancer cell stemness via transcriptionally and epigenetically regulating E-cadherin

OBJECTIVES

The roles and related mechanisms of six2 in regulating non-small cell lung cancer (NSCLC) cells progression are unclear. This work aimed to explore the roles of six2 in NSCLC cell stemness.

MATERIALS AND METHODS

Kaplan-Meier plotter analysis was used to examine the correlation between six2 expression and the survival of NSCLC patients. Quantitative reverse transcription PCR and Western blot were performed to detect six2 expression in clinical samples. Moreover, transwell migration, tumour spheroid formation and in vivo tumour formation assays were used to examine the effects of six2 on NSCLC cell progression. Additionally, methylation analysis was carried out to measure E-cadherin methylation level in different cells. Finally, cell viability assay was performed to explore the effects of six2 on chemotherapeutic sensitivity of NSCLC cells.

RESULTS

Lung cancer patients with a higher six2 expression level displayed a shorter overall survival. Six2 expression was higher in lung cancer tissues than in normal adjacent tissues. Additionally, six2 knockdown suppressed NSCLC cell stemness. Mechanistically, six2 overexpression inhibited epithelial marker E-cadherin expression via stimulating its promoter methylation. And E-cadherin knockdown rescued six2 knockdown-induced decrease of NSCLC cancer cell stemness. Notably, six2 knockdown enhanced cisplatin sensitivity in parental NSCLC cells and attenuated cisplatin resistance in cisplatin-resistant NSCLC cells.

CONCLUSIONS

Our results suggest that six2 facilitates NSCLC cell stemness and attenuates chemotherapeutic sensitivity via suppressing E-cadherin expression.

Sotrastaurin attenuates the stemness of gastric cancer cells by targeting PKCδ

Gastric cancer (GC) is one of the most lethal malignancies. Chemoresistance and metastasis are the main cause of treatment failure. Cancer stem cells (CSCs) have been proven to be essential for cancer metastasis and chemoresistance. PKCδ (protein kinase C-δ), a novel member of PKC family, has been validated as a synthetic lethal target in multiple cancers, and contributes to tyrosine kinase inhibitors (TKI) resistance in EGFR-mutant NSCLC (non-small cell lung cancer) patients. However, its role in GC is unclear. Here, we systematically investigate its role in GC, especially in regulating GC stem cell-like properties. We found that PKCδ positively regulated the metastasis, chemoresistance, and stem cell-like characteristics of GC cells, and its inhibitor sotrastaurin could rescue the above effects mediated by PKCδ. Importantly, sotrastaurin could also weaken metastasis, chemoresistance, and stem cell-like characteristics of adriamycin-resistant GC cells via PKCδ suppression, indicating sotrastaurin is an ideal candidate for combinational therapy to overcome chemoresistance for GC.