Objective      To determine the regulative effect of aryl hydrocarbon receptor (AhR) and its ligand

6-formylindolo [3

2-b] carbazole (FICZ)

in the expression of keratinocyte growth factor receptor (KGFR) and proliferation in colorectal cancer epithelial cells.       Methods      The expression and location of KGFR were detected in the normal tissues and colorectal cancer tissues by immunohistochemical staining and real-time PCR. Immunofluorescence assay was used to observed the location of AhR in LoVo and Caco-2 cell lines. The expression levels of AhR

CYP1A1 and KGFR were detected by Western blotting and real-time PCR in the FICZ treated cells and control cells. Cell proliferation was measured by counting the cell number among the normal

KGF treated

KGF+FICZ treated and FICZ treated cells

respectively.       Results       KGF was highly expressed in the 11 specimens from the 12 cancer cases

and KGFR was strongly expressed in the 8 specimens of 12 cases and was located mainly on the intestinal epithelial cells. In vitro study found that FICZ treatment resulted in 50% and 58.8% respectively decreases in the expression of KGFR at protein and mRNA levels in LoVo cells

and 52.6% and 62.5% respectively in Caco-2 cells. However

AhR inhibitor CH223191 could block this down-regulated expression of KGFR. Furthermore

FICZ could decrease the KGF-induced cell proliferation in LoVo (34%) and Caco-2 cells (37%).       Conclusion       AhR inhibits the proliferation of colon cancer cells induced by KGF through down-regulating the expression of KGFR.