Twist1 and Y-box-binding protein-1 promote malignant potential in bladder cancer cells.

OBJECTIVE: To investigate the roles of Twist1 and Y-box binding protein-1 (YB-1) and their potential as therapeutic targets in bladder cancer (BC), as both have been suggested to play important roles in tumour growth, invasion and drug resistance. MATERIALS AND METHODS: Bladder cancer cell lines (TCCsup, UMUC3, T24 and KK47 cells) were used. Twist1 and YB-1 expression levels were assessed by luciferase reporter assay, quantitative real-time polymerase chain reaction (PCR) and western blot analysis. Tumour growth and cell cycle were analysed by cell proliferation assay and flow cytometry, respectively. Invasive and motile abilities were investigated by scratch-wound test and migration assay, respectively. Cytotoxicity assay was performed to determine drug sensitivity. RESULTS: The findings showed that Twist1 regulated YB-1 expression in BC cells. Both Twist1 and YB-1 were involved in cell growth, invasion, motility and resistance to cisplatin and doxorubicin, but not to 5-fluorouracil (5-FU). CONCLUSION: The present study showed that Twist1 regulates YB-1 expression and that both Twist1 and YB-1 promote malignant potentials, including tumour growth, invasion and anti-cancer-drug resistance, indicating that both Twist1 and YB-1 are novel molecular targets in BC.

Tip60 promotes prostate cancer cell proliferation by translocation of androgen receptor into the nucleus.

BACKGROUND: There are currently few effective therapies for castration-resistant prostate cancer (CRPCa). CRPC which is resistant to castration is thought to result from increased activation of the androgen/androgen receptor (AR) signaling pathway, which may be augmented by AR coactivators. METHODS: Luciferase reporter assay, Western blotting, quantitative real-time polymerase chain reaction, fluorescence microscopy, cell proliferation assay, and flow cytometry for cell-cycle analysis were used to resolve a role of Tip60 regulating AR in PCa cells. RESULTS: Tip60 regulated transcriptions of AR target genes androgen independently. Tip60 knockdown induced translocation of AR into the cytoplasm. Acetylation-mimicking mutations in the nuclear localization signal sequence caused AR protein to mainly localize in the nucleus despite androgen starvation, whereas non-acetylation-mimicking mutations caused AR to mainly localize in the cytoplasm despite androgen stimulation. Tip60 overexpression in castration-resistant LNCaP derivative CxR cells resulted in increases in the acetylated form of AR and AR localization in the nucleus even without androgen. Consequently, Tip60 silencing suppressed the growth of AR-expressing PCa cells by inducing cell-cycle arrest at the G1 phase, similar to inhibition of androgen/AR signaling. Furthermore, Tip60 knockdown suppressed the cell growth of CxR cells. CONCLUSIONS: Tip60 is involved in the proliferation of PCa cells as an AR coactivator. Modulation of Tip60 expression or function may be a useful strategy for developing novel therapeutics for PCa, even CRPC, which remain dependent on AR signaling, by overexpressing AR and its coactivators.

Sorafenib with doxorubicin augments cytotoxicity to renal cell cancer through PERK inhibition.

Although cytokine therapy involving interleukin-2 or interferon-alpha has been employed for metastatic renal cell cancer (RCC) treatment, these therapies yielded limited response and benefit. Recently, several molecular-targeted agents have become available, and one newly developed anti-RCC agent, sorafenib (BAY 43-9006), is known to target multiple kinases. In this study, sorafenib was found to inhibit phosphorylation of the eukaryotic initiation factor-2alpha (eIF2alpha) and induce cell cycle arrest at G2/M phase and increase cell death. One of eIF2alpha kinases, PERK was responsible for eIF2alpha phosphorylation in RCC cells and PERK knockdown induced cell death similar to sorafenib treatment. The efficiency of sorafenib treatment correlated with phosphorylation level of eIF2alpha and nuclear Nrf2 expression level in eight RCC cell lines. Furthermore, sorafenib made Caki-1 and 786-O cells, but not ACHN cells sensitive to oxidative stress exerted by both hydrogen peroxide and doxorubicin. In addition, PERK knockdown sensitized Caki-1 and 786-O cells, but not ACHN cells to oxidative stress. In conclusion, levels of phospho-eIF2alpha and nuclear Nrf2 expression level in RCC might be a predictor of outcome in sorafenib treatment. In addition, PERK inhibition as well as sorafenib plus doxorubicin might be a promising therapeutic approach for RCC characterized by high levels of phosphorylated-eIF2alpha and nuclear Nrf2.

Programmed cell death protein 4 down-regulates Y-box binding protein-1 expression via a direct interaction with Twist1 to suppress cancer cell growth.

Programmed cell death protein 4 (PDCD4) has recently been shown to be involved in both transcription and translation, and to regulate cell growth. However, the mechanisms underlying PDCD4 function are not well understood. In this study, we show that PDCD4 interacts directly with the transcription factor Twist1 and leads to reduced cell growth through the down-regulation of the Twist1 target gene Y-box binding protein-1 (YB-1). PDCD4 interacts with the DNA binding domain of Twist1, inhibiting its DNA binding ability and YB-1 expression. Immunohistochemical analysis showed that an inverse correlation between nuclear PDCD4 and YB-1 expression levels was observed in 37 clinical prostate cancer specimens. Growth suppression by PDCD4 expression was completely recovered by either Twist1 or YB-1 expression. Moreover, PDCD4-overexpressing cells are sensitive to cisplatin and paclitaxel but not to etoposide or 5-fluorouracil. In summary, PDCD4 negatively regulates YB-1 expression via its interaction with Twist1 and is involved in cancer cell growth and chemoresistance.