Stimulation of colorectal cancer cell line growth by ET-1 and its inhibition by ET(A) antagonists

Abstract

Background - The vasoactive peptide endothelin 1 (ET-1) acts via two receptors, endothelin receptors A (ET(A)) and B (ET(B)). ET-1 is overexpressed by human cancers in vivo and in vitro and may be mitogenic for cancer cells. Method - To elucidate if ET-1 is a growth regulator the following were investigated in human colorectal cancer cell lines (LIM1215 and HT29): ET-1 production by ELISA; ET receptor expression using radioligand autoradiographic techniques; and responsiveness to ET-1, and to ET(A) and ET(B) antagonism by growth measurements. Results - ET-1 was produced by LIM1215 and HT29 cells (21.3 and 41.7 fmol/ml/106 cells (24 hours); 22.6 and 71.7 fmol/ml/106 cells (48 hours), respectively). ET(A) and ET(B) receptors were expressed by both cell lines. Addition of ET-1 resulted in a dose dependent increase in cell numbers which was significant at 10-8-10-9 M for LIM1215, with the greatest increase at 10-8 M (32.7% and 28.4% increase above controls at 48 hours and 72 hours; p<0.05) and at 10-8-10-9 M for HT29, with the greatest increase at 10-9 M (13.4% and 15.7% increase above controls at 48 hours and 72 hours; p<0.05). ET(A) antagonists BQ123 and BQ610, but not the ET(B) antagonist BQ788, inhibited ET-1 induced proliferation of both LIM1215 and HT29 (p<0.05). Conclusion - ET-1 can stimulate the proliferation of colorectal cancer cell lines via the ET(A), but not the ET(B), receptor.