Abstract 1729: Connecting Gli1 with chemoresistance in small cell lung cancer

Abstract Background. Small-cell lung cancer (SCLC) accounts for ∼15% of all lung cancers, and is the most aggressive form of lung cancer. Drug resistance to chemotherapeutics is particularly crippling in SCLC as there are limited treatment options. We previously examined gene expression in platinum-resistant SCLC cell lines, and reported aberrant expression of a subset of hedgehog pathway related genes, among which Gli1 was particularly significant. Gli1 is a known transcription factor that is involved with regulation of a number of key genes in cell fate determination and proliferation. In recent years, its role in oncogenesis and cancer progression has been studied. Herein, we test the hypothesis that increased Gli1 expression contributes to cisplatin and etoposide resistance in SCLC. Methods. Two SCLC cell lines, H69 and H526, were transduced with a Gli1 over-expressing (o/e) vector (Kasper et al, 2007) to create two lines expressing the gene: H69-Gli1 and H526-Gli1. Gli1 expression was verified by qRT-PCR. Cellular proliferation was measured over 96 hours. To study the drug dose response, Gli1 o/e and parental lines were treated with single-agent or combination dosing of cisplatin and etoposide (standard first-line SCLC therapy), and cell viability was assessed after 72 hours. Relative Gli1 expression was compared with cisplatin response in four additional SCLC cell lines (H146, H187, H345, H1688). To further understand aberrant cellular signaling in Gli1 o/e cells, gene expression analysis was performed on H69-Gli1 and H69 parental cells (2 replicates) using Agilent 44K expression arrays. Data was normalized and analyzed using Genespring software. Changes greater than 2 fold were considered significant. Results. Compared to parental cells, Gli1 expression was 11 fold and 149 fold higher in H69-Gli1 and H526-Gli1, respectively. Proliferation assays showed no significant differences in parental vs. Gli1 o/e cells. Drug dose response experiments showed at least a 1.5 fold shift in cisplatin resistance in H69-Gli1 compared to H69. The same trend was also observed in combination dosing of cisplatin and etoposide. H526-Gli1 showed no significant change in cisplatin resistance compared to H526. In the four additional SCLC lines a positive trend was observed where increased Gli1 expression correlated with increased cisplatin resistance. Gene expression analysis showed that there are over 1200 genes significantly differentially-expressed in H69-Gli1 cells as compared to parental cells. Conclusions. Gli1 over-expression leads to increased platinum resistance in SCLC cells. We are currently in the process of performing pathway analysis on the gene expression data to study the pathways affected by Gli1 over-expression in H69 cells, leading to increased platinum resistance. 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 1729. doi:10.1158/1538-7445.AM2011-1729