Abstract 2475: Excision repair cross complementing group 1 (ERCC1) predicts the efficacy of chemoradiotherapy for invasive bladder cancer

Abstract

Abstract Purpose: Chemoradiation therapy (CRT) is now widely recognized as bladder-preserving therapy for muscle-invasive bladder cancer (MIBC). However, some patients who fail CRT may miss the chance to be cured by cystectomy. Therefore, it is important to select patients with MIBC who are expected to have a good response to CRT. Several reports indicate that the excision repair cross-complementing group 1 (ERCC1) gene is associated with resistance to cisplatin and radiation therapy. In this study, we examined the correlation between ERCC1 and CRT in vitro and in vivo in bladder cancer. Experimental Design: Bladder cancer cell lines T24, 5637, Cl8-2 (multi-drug-resistant subline of T24), and CDDP10-3 (cisplatin-resistant subline of T24) were used for in vitro assays to measure ERCC1 expression level and growth inhibition with cisplatin or irradiation (IR). To clarify the association between ERCC1 and cisplatin resistance in bladder cancer cells, we knocked down ERCC1 in Cl8-2 and CDDDP10-3 with siRNA (C18-2ΔERCC1 and CDDP10-3ΔERCC1). To further prove the cause of the radiation sensitivity of ERCC1 knockdown cells, we measured the phosphorylated histone variant H2A.X, a marker of DNA damage. In the clinical study, we then examined by immunohistochemistry whether ERCC1 nuclear staining correlates with the efficacy of CRT using cisplatin in 22 patients with MIBC. Results: Cl8-2 cells expressed ERCC1 mRNA 5.96-fold higher than did T24. Cl8-2 and CDDP10-3 were more resistant to cisplatin or IR than was T24. Our ERCC1 knockdown experiments showed that there was statistical difference in the resistance to IR exposure not cisplatin compared with C18-2CTL and CDDP10-3CTL. C18-2ΔERCC1 and CDDP10-3ΔERCC1 recovered more slowly in terms of the number of phospho-H2A.X foci than did C18-2cont and CDDP10-3cont, suggesting continued accumulation or persistence of DSBs. In immunohistochemistry with ERCC1, six of eight positive cases did not have complete response to CRT, whereas 12 of 14 negative cases had complete response. Sensitivity and specificity were 75% and 85.7%, respectively (p = 0.008). Conclusion: Our results suggest that in some bladder cancer cells, ERCC1 expression correlates with IR resistance but not with cisplatin resistance. Moreover, the lack of ERCC1 expression correlated well with the efficacy of CRT, and especially with that of IR, in our clinical study. Although further study is needed, ERCC1 expression level may predict the efficacy of CRT for MIBC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2475. doi:10.1158/1538-7445.AM2011-2475