EGFR mediates docetaxel resistance in human castration-resistant prostate cancer through the Akt-dependent expression of ABCB1 (MDR1).

Recent studies have shown that docetaxel-based chemotherapy confers a survival benefit in patients with castration-resistant prostate cancer (PC). Also epidermal growth factor receptor (EGFR) was found to have multiple roles in prostatic tumorigenesis. However, the EGFR-mediated chemoresistance mechanism in human PC was not well delineated. In this study, we explored the mechanism of EGFR-mediated docetaxel resistance in PC. A series of stable docetaxel-resistant PC/DX sublines were established at our laboratory. The docetaxel IC50s of PC3 and PC/DX25 cells were 0.01 and 1.33 µM, respectively. Cellular resistance to docetaxel was significantly associated with increased EGFR and EGFR activation in PC/DX25. There was a dose-dependent increase in EGFR expression associated with the magnitude of docetaxel resistance. Expression of EGFR in PC/DX25 was higher than that in PC3, RWPE-1 and LNCaP cells. Similar results were also found in human PC tissues by immunohistochemical staining. We showed that docetaxel sensitivity can be stored in PC/DX25 cells by knockdown and inactivation of EGFR expression through EGFR siRNA and specific inhibitors, respectively. Contrarily, overexpression of EGFR or recombinant EGF protein treatment could rescue PC3 cells from docetaxel-mediated cytotoxicity. Gefitninb (ZD1839) significantly inhibited the growth of PC/DX25 cells by MTT in vitro and on xenografted nude mice in vivo. Moreover, EGFR-mediated docetaxel resistance occurred through the Akt-dependent ABCB1 expression in PC cells. These findings demonstrated EGFR played an important role in docetaxel-resistant PC and EGFR inhibition may enhance the therapeutic efficacy of docetaxel-based treatment.

Down-regulation of PKCζ in renal cell carcinoma and its clinicopathological implications.

BACKGROUND: Metastatic renal cell carcinoma (RCC) is highly resistant to systemic chemotherapy. Unfortunately, nearly all patients die of the metastatic and chemoresistant RCC. Recent studies have shown the atypical PKCζ is an important regulator of tumorigenesis. However, the correlation between PKCζ expression and the clinical outcome in RCC patients is unclear. We examined the level of PKCζ expression in human RCC. METHODS: PKCζ mRNA and protein expressions were examined by real-time polymerase chain reaction (PCR) and immunohistochemistry (IHC) respectively in RCC tissues of 144 patients. Cellular cytotoxicity and proliferation were assessed by MTT. RESULTS: PKCζ expression was significantly higher in normal than in cancerous tissues (P<0.0001) by real-time PCR and IHC. Similarly, PKCζ expression was down-regulated in four renal cancer cell lines compared to immortalized benign renal tubular cells. Interestingly, an increase of PKCζ expression was associated with the elevated tumor grade (P=0.04), but no such association was found in TNM stage (P=0.13). Tumors with higher PKCζ expression were associated with tumor size (P=0.048). Expression of higher PKCζ found a poor survival in patients with high tumor grade. Down-regulation of PKCζ showed the significant chemoresistance in RCC cell lines. Inactivation of PKCζ expression enhanced cellular resistance to cisplatin and paclitaxel, and proliferation in HK-2 cells by specific PKCζ siRNA and inhibitor. CONCLUSIONS: PKCζ expression was associated with tumorigenesis and chemoresistance in RCC.

Simvastatin induces the expression of hemeoxygenase-1 against ischemia-reperfusion injury on the testes in rats.

We evaluate the protective role of simvastatin-induced HO-1 in remote preconditioning against testis ischemia-reperfusion (IR) injury in vivo. Simvastatin was intraperitoneally (i.p.) injected 24 h before IR injury. Testis was occluded in the right testis for 40 min and followed by 30 min of reperfusion to induce IR injury. Tin protoporphyrin (Snpp), a competitive inhibitor of hemeoxygenase, was i.p. injected 1 h before the IR injury in separate groups of rats. The rat testes were harvested 24 h later. Induction of HO-1 expression by simvastatin was significantly increased at 24 and 48 h. Rats pre-treated with simvastatin showed higher expression of HO-1 protein by Western blotting and immunohistochemistry (IHC), and presented lower caspases-3 activity by caspase-3 activity assay. TUNEL staining analysis revealed simvastatin pretreatment significantly reduced IR induced cellular apoptosis. Contrarily, the simvastatin-induced cytoprotective effect was entirely abolished by administrations of Snpp. Further, lower caspase-3 activities were also noted in simvastatin plus Snpp (SS) group than the control plus Snpp (CS) group. After IR injury, eNOS immunoreactivity was markedly increased in the germ cell and Leydig cell of testicular tissues. Pretreatment of simvastatin significantly decreased eNOS immunoreactivity in the germ cell of the tubules in the rat testes. In conclusion, we suggest HO-1 plays a protective role in IR-induced injury in the testes of rats.

Overexpression of Rho GDP-dissociation inhibitor alpha predicts poor survival in oral squamous cell carcinoma.

Oral cancer has emerged as one of the fastest growing malignancies in Taiwan. However, biomarkers that reliably predict clinical outcomes have yet to be identified. This study was aimed to identify tumor-associated proteins that could be prognostic biomarkers for oral cancer. We compared the protein expression between oral squamous cell carcinoma (OSCC) tissues and adjacent non-cancerous matched tissues (NCMTs) by proteomics. We found that Rho GDP-dissociation inhibitor alpha (RhoGDIα) was differentially expressed in frozen cancerous samples and OSCC cell lines but not in NCMTs. Furthermore, our results indicated that RhoGDIα was selectively upregulated in 78 OSCC tissue sections (p<0.001), and this high expression was significantly correlated with increased tumor size (p<0.05) and poor overall survival (p<0.01). There was a trend that RhoGDIα expression was localized in the cytoplasm of cancer cells but was localized in the plasma membrane of NCMTs. Finally, expression of RhoGDIα was validated to be an independent prognostic indicator for overall survival (p<0.01). These results have identified a novel biomarker that may be useful for prediction of poor prognosis in OSCC patients.