Abstract 5102: In vitro hedgehog signaling pathway alterations after acquired-platinum resistance in small cell lung cancer

Abstract

Abstract Background: The Hedgehog (HH) signaling pathway regulates cell growth and differentiation during embryonic tissue development and may play a role of ‘stem cell’ maintenance in adults. Studies have shown that SCLC platinum resistance and cell death is associated with HH signaling pathway maintenance, potentiating SCLC re-growth after chemotherapy. We hypothesized that acquired-platinum resistance would alter HH pathway signaling. Methods: SCLC cell lines, H69 and H146 along with their acquired cisplatin (H69Cis1) and carboplatin resistant (H69Car1, H146Car1, and H146Car2) versions were used. mRNA expression of genes in HH pathway were measured. Fold changes in mRNA expression in resistant cells (RCs) compared to parent cells were calculated. A two-sided t-test was used to compute the p-values for the fold changes. Proteins from these cells were probed for SHH, SUFU, and GLI1 by immunoblot. Results: The mRNA expression of genes in HH pathway was altered in platinum RCs compared to their parental cells (Table 1). As with mRNA expression, SHH protein is decreased in both H69 cisplatin and carboplatin RCs (by 93% in H69Cis1 and by 76% in H69Car1) and by 62% in H146 carboplatin RCs. SUFU mRNA and protein expression are not significantly different in the platinum RCs compared to their parental cells. GLI1 protein was not expressed in vitro in these cell lines, but there was a significant increase in GLI1 mRNA expression in platinum RCs. Conclusions: Our results indicate that the genes in the HH pathway such as GLI1, GLI2, PTCH1, PTCH2, SHH, and SMO are altered in vitro in cisplatin and carboplatin H69 and H146 acquired RCs compared to respective parent cell lines. Detailed studies with other SCLC cells lines with variable sensitivity to platinum and the impact of HH pathway inhibitors on the platinum resistant cell lines in vivo are worth further exploration.Table 1:Relative Fold Changes in mRNA Expression of HH Pathway Genes in Acquired-Platinum Resistant SCLC Cell Lines GLI1GLI2HHIPPTCH1PTCH2SHHSMOSuFuH6911111111H69Car13.17 (0.29)3.46 (0.51)1.21 (0.14)1.52 (0.048*)1.05 (0.93)88.54 (0.17)2.13 (0.037*)0.9 (0.80)H69Cis113.49 (0.028*)3.71 (<0.001*)2.8 (0.018*)1.37 (0.07)1.34 (0.20)55.26 (0.009*)26.01 (<0.001*)1.16 (0.57)H14611111111H146Car16.62 (0.02*)8.49 (<0.001*)0.71 (0.43)0.24 (0.05)0.17 (0.043*)8.49 (<0.001*)0.11 (0.011*)0.71 (0.15)H146Car23.45 (0.05)11.71 (<0.001*)1.13 (0.62)0.17 (0.045*)0.45 (0.15)11.71 (<0.001*)0.13 (0.001*)1.10 (0.49)The values in the table indicate mean (p-value)*Significant p<0.05Fold changes in mRNA expression in resistant cells (RCs) compared to parent cells were calculated.(Supported by the TGen Foundation and SHC Foundation) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5102.