Downregulation of HIPK2 increases resistance of bladder cancer cell to cisplatin by regulating Wip1.
Cisplatin-based combination chemotherapy regimen is a reasonable alternative to cystectomy in advanced/metastatic bladder cancer, but acquisition of cisplatin resistance is common in patients with bladder cancer. Previous studies showed that loss of homeodomain-interacting protein kinase-2 (HIPK2) contributes to cell proliferation and tumorigenesis. However, the role of HIPK2 in regulating chemoresistance of cancer cell is not fully understood. In the present study, we found that HIPK2 mRNA and protein levels are significantly decreased in cisplatin-resistant bladder cancer cell in vivo and in vitro. Downregulation of HIPK2 increases the cell viability in a dose- and time-dependent manner during cisplatin treatment, whereas overexpression of HIPK2 reduces the cell viability. HIPK2 overexpression partially overcomes cisplatin resistance in RT4-CisR cell. Furthermore, we showed that Wip1 (wild-type p53-induced phosphatase 1) expression is upregulated in RT4-CisR cell compared with RT4 cell, and HIPK2 negatively regulates Wip1 expression in bladder cancer cell. HIPK2 and Wip1 expression is also negatively correlated after cisplatin-based combination chemotherapy in vivo. Finally, we demonstrated that overexpression of HIPK2 sensitizes chemoresistant bladder cancer cell to cisplatin by regulating Wip1 expression.


CONCLUSIONS
These data suggest that HIPK2/Wip1 signaling represents a novel pathway regulating chemoresistance, thus offering a new target for chemotherapy of bladder cancer.
Department of Urology, Beijing Friendship Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Jun
J
Lin
Department of Urology, Beijing Chao-Yang Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Qiang
Q
Zhang
Department of Urology, Beijing Friendship Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Yi
Y
Lu
Department of Urology, Beijing Chao-Yang Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Wenrui
W
Xue
Department of Urology, Beijing Chao-Yang Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Yue
Y
Xu
Department of Urology, Beijing Friendship Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Yichen
Y
Zhu
Department of Urology, Beijing Chao-Yang Hospital Affiliated to Capital Medical University, Beijing, P.R China.
Xiaopeng
X
Hu
D000368:Aged; D000369:Aged, 80 and over; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival; D002945:Cisplatin / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D008875:Middle Aged; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D000071636:Protein Phosphatase 2C; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*
D002352:Carrier Proteins; C115114:HIPK2 protein, human; D017346:Protein Serine-Threonine Kinases; C000607458:PPM1D protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D002945:Cisplatin