p63 expression correlates with sensitivity to the Eg5 inhibitor AZD4877 in bladder cancer cells

Abstract

Antimitotics such as taxanes are being considered as alternatives to conventional cisplatin-based chemotherapy in patients with bladder cancer, but the molecular determinants of sensitivity or resistance to these agents in bladder cancer cells have not been defined. Here we examined the cytotoxic effects of a novel antimitotic, the Eg5 inhibitor AZD4877, in a molecularly diverse panel of human bladder cancer cell lines. The cells displayed heterogeneous responses to the drug that correlated closely with sensitivity to docetaxel but not with sensitivity to cisplatin. Global gene expression profiling identified p63 as the top gene that was differentially expressed between sensitive and resistant cell lines. Stable knockdown of p63 inhibited cell death induced by either AZD4877 or docetaxel and was associated with decreased proliferation and decreased expression of c-myc. Furthermore, c-myc knockdown also rendered cells resistant to AZD4877 or docetaxel. Together, our results implicate p63 and its downstream target c-myc as determinants of sensitivity to anti-mitotics in bladder cancer cells. Our data also suggest that anti-mitotics and cisplatin target different subsets of bladder cancer cells, a conclusion that may have important implications for the therapy of muscle-invasive bladder cancers.

The p63 Protein Isoform ΔNp63α Inhibits Epithelial-Mesenchymal Transition in Human Bladder Cancer Cells

“…Furthermore, we recently reported that p63 and E-cadherin expression correlated closely with one another in human BC lines and primary tumors (19,20). However, other recent work suggests that normal epithelial stem cells and cancer stem cells from epithelial tissues possess features of EMT (28).…”

“…Immunoblotting-Immunoblotting experiments were performed as described previously (20). Primary antibodies used in this study were anti-panp63 (clone 4A4, Santa Cruz Biotechnology, Santa Cruz, CA, catalog no.…”

“…Virus production, virus infection, and infected cell selection were performed in the MD Anderson Vector Core as described in Ref. 20.…”

“…The non-targeting siRNA was from Dharmacon (catalog no. D-001810- [10][11][12][13][14][15][16][17][18][19][20]. siRNAs were transfected into cells using Lipofectamine RNAiMAX (Invitrogen/Life Techonologies, catalog no.…”

“…We noted recently that a close correlation between expression of ⌬Np63 and E-cadherin exists in BC cell lines and primary tumors (19,20). To determine whether a cause-effect relationship exists between the two, we used RNAi and whole genome expression profiling to identify EMT-related targets of ⌬Np63 in human BC cells.…”