Met signaling in urothelial carcinoma of the bladder.

Abstract

4551 Background: Mounting evidence of hepatocyte growth factor (HGF)/Met signaling in urothelial carcinoma (UC) suggests that pathway inhibition could have therapeutic benefit in some patients. The effects of two Met inhibitors, cabozantinib (which also targets VEGFR2), and crizotinib (which also targets ALK), on Met-driven UC cell growth, invasion and tumorigenicity were analyzed in biochemical, cell-based and animal models. Methods: The effects of cabozantinib or crizotinib on HGF signaling were assessed in 9 human UC-derived cell lines: RT4, TCC-SUP, T24M2, T24M3, J82, SW780, UMUC3, UMUC5, and 5637. Biochemical assays included total Met protein, phospho-Met (pMet), pAkt, total Akt, pErk and total Erk analysis. Cultured cell assays of invasion, proliferation and anchorage independent growth were performed in all 9 lines. The growth rates of SW780 xenografts in SCID and human HGF knock-in SCID (hHGF/SCID) mice treated daily with cabozantinib or vehicle alone, as well as tumor levels of Met and pMet, were determined. Results: Met content was low in RT4 and higher in T24M2, T24M3, TCC-SUP, J82, SW780 UMUC3, UMUC5, and 5637 cells. Basal pMet content in quiescent cells was universally low and significantly enhanced by added HGF, an effect that was reversed by treatment with cabozantinib or crizotinib. HGF-driven increases in pAkt/Akt and pErK/ErK in all 9 cell lines were also reversed by cabozantinib or crizotinib treatment, as were HGF-enhanced cell invasion, proliferation and anchorage independent growth. SW780 xenograft growth rate in hHGF/SCID mice was significantly higher than in SCID mice and significantly inhibited by cabozantinib treatment, as was tumor pMet content. Conclusions: Cultured UC cell Met content was higher in cell lines derived from higher stage disease. HGF stimulated the activation of Met and known effectors, and enhanced invasion, growth rate and anchorage-independent growth; treatment with cabozantinib or crizotinib effectively reversed these HGF-driven effects. Cabozantinib also significantly inhibited HGF-driven tumor xenograft growth and Met activation in SCID and, more dramatically, in hHGF/SCID mice. These preclinical studies support further investigation of Met inhibitors for the treatment of UC in human clinical trials.