YY1-mediated PTEN dephosphorylation antagonizes IR-induced DNA repair contributing to tongue squamous cell carcinoma radiosensitization.

Ionizing radiation (IR) confers a survival advantage in tongue squamous cell carcinoma (TSCC), however, IR resistance limits its efficacy. Although Yin Yang 1 (YY1) has been reported to play a role in genotoxic drug resistance by accelerating DNA repair, its role in TSCC radioresistance remains unclear. In this study, we examined YY1 mRNA and protein expression in human tongue cancer samples using qRT-PCR and western blotting, respectively. DNA array data identified YY1 mRNA expression in IR sensitivity or resistance cell lines and tissues. Tongue carcinoma primary cells and CAL27 cells with YY1 stably overexpressed or knocked-down were exposed to IR and evaluated for cell proliferation and apoptosis by CCK8-assay and caspase-3 assay, respectively. We also examined DNA damage- or repair-related indicators, such as YY1, p-H2AX, nuclear PTEN, p-PTEN, and Rad51 through Western blot analysis. Additionally, we explored the mechanism of IR-induced PTEN nuclear translocation by introducing a series of PTEN phosphorylation site mutations and co-IP assay. We observed that YY1 mRNA and protein are highly expressed in TSCC tissues, which was correlated with worse overall survival. Moreover, higher expression of YY1 and Rad51 was observed in radioresistant cells and tissues, overexpression of YY1 led to IR resistance in TSCC cells, whereas YY1 knockdown sensitized TSCC cells to IR. The underlying mechanism showed that the overexpression of YY1 upregulated nuclear PTEN and Rad51 expression, which is essential for DNA repair. IR upregulated YY1, nuclear PTEN, and Rad51; thus, knockdown of YY1 completely blocked IR-induced upregulation of nuclear PTEN/Rad51. IR upregulated PTEN phosphorylation, and mutation of the phosphorylation site of Ser380 nearly completely blocked IR-induced PTEN nuclear translocation. Furthermore, the phosphatase PP2A negatively regulated pS380-PTEN, and knockdown of YY1 completely blocked IR-induced pS380-PTEN through PP2A. In conclusion, knockdown of YY1 enhanced TSCC radiosensitivity through PP2A-mediated dephosphorylation of PTEN Ser380; thus, antagonizing the IR-induced nuclear PTEN/Rad51 axis and targeting YY1 may reverse IR resistance in TSCC.

[Urethral guidance probe applied to surgical urethral realignment].

OBJECTIVE: To search for a safe and convenient surgical method for management of urethral disruption. METHODS: We performed urethral realignment for 18 cases of posterior urethral disruption and 4 cases of ruptured bulbous urethra using the urethral guidance probe following bladder puncture stoma. RESULTS: Urethral realignment was accomplished in 21 of the cases, 18 under epidural and 3 under local anesthesia, with the mean blood loss of 20 ml and the average operation time of 18 minutes. Open surgery was necessitated in 1 case due to the complication of bladder rupture. Routine postoperative urethral dilation extended for 3 months, and all the cases were followed up for 3 to 24 months. The maximum urine flow rate was 15-22 ml/s in 13 cases and 10-14 ml/s in 7. One case received urethral anastomosis 3 months later because of urethrostenosis. CONCLUSIONS: Urethral realignment with the urethral guidance probe is a safe, convenient and effective surgical strategy for the management of urethral disruption.