1694P - Hedgehog GLI3 Signal Contributes to Anchor-Independent Growth and Tumorigenicity for Colorectal Cancer

Abstract

ABSTRACT Backgrounds Hegehog (Hh) signal is one of the morphologic signals and re-activated in several cancer. Among Gli family proteins, major transcription factors in Hedgehog pathway, Gli3 has two isoforms of activator and suppressor for Gli1 signal, although it generally plays as transcriptional suppressor in normal organ development. However, the role of Gli3 in colorectal cancer remains unclear. In this study, we examined the biological role of Gli3 in colorectal cancer. Materials and methods The expression of Hh signal components was analyzed in four colorectal cancer cell lines (HCT116, HT29, SW480 and DLD-1) by conventional RT-PCR and immunocytochemistory. Colony formation and proliferation assay were performed after transduction or knockdown of Gli3 gene to examine the effect of Gli3 on anchor-independent and -dependent growth. Furthermore, Gli3 or mock transfectant DLD-1 cells were subcutaneously implanted in SCID mice to examine the effect of Gli3 on tumorigenicity. To examine whether Gli and sonic Hh (Shh) are expressed in tumor specimens of colorectal cancer patients, immunohistochemistory was performed. Results Gli3 was detected in HT29 and SW480 cells, but not in HCT116 or DLD-1 cells. Both anchor-independent and -dependent growths were increased in all cell lines of which Gli3 full length (Gli3-FL; activator isoform) was over-expressed, although Gli1 mRNA was not affected. Recombinant Shh up-regulated colony formation and proliferation in HT29 and SW480 cells with endogenous Gli3 expression, but not in Gli3-undetectable HCT116 or DLD-1 cells. Silencing of endogenous Gli3 down-regulated colony formation and proliferation in HT29 and SW480 cells. However, truncated Gli3 (Gli3-R; repressor isoform) transduction had no effect on these phenotypes although Gli1 expression was inhibited. After implantation of Gli3- or mock-transfected DLD-1 cells into immunedeficient SCID mice, tumor formation was observed in only Gli3-transfectant DLD-1 group but not in mock control. In surgically resected colorectal cancer specimen, Gli3 expression was heterogeneously detected and Shh expression was highly observed. Conclusions Gli3-FL and Shh signals induce tumorigenicity in Gli1 independent manner, and Gli3-FL may be molecular targets for refractory colorectal cancer. Disclosure All authors have declared no conflicts of interest.