Prolonged Sulforaphane Treatment Activates Survival Signaling in Nontumorigenic NCM460 Colon Cells but Apoptotic Signaling in Tumorigenic HCT116 Colon Cells

Abstract

Sulforaphane (SFN) is a naturally occurring chemopreventive agent; the induction of cell cycle arrest and apoptosis is a key mechanism by which SFN exerts its colon cancer prevention. However, little is known about the differential effects of SFN on colon cancer and normal cells. In this study, we demonstrated that SFN (15 μmol/L) exposure (72 h) inhibited cell proliferation by up to 95% in colon cancer cells (HCT116) and by 52% in normal colon mucosa-derived (NCM460) cells. Our data also showed that SFN exposure (5 and 10 μmol/L) led to the reduction of G1 phase cell distribution and an induction of apoptosis in HCT116 cells, but to a much lesser extent in NCM460 cells. Furthermore, the examination of mitogen-activated protein kinase (MAPK) signaling status revealed that SFN upregulated the phosphorylation of extracellular-regulated kinase 1/2 (ERK1/2) in NCM460 cells but not in HCT116 cells. In contrast, SFN enhanced the phosphorylation of stress-activated protein kinase (SAPK) and decreased cellular myelocytomatosis oncogene (c-Myc) expression in HCT116 cells but not NCM460 cells. Taken together, the activation of survival signaling in NCM460 cells and apoptotic signaling in HCT116 cells may play a critical role in SFN's stronger potential of inhibiting cell proliferation in colon cancer cells than in normal colon cells.

ACKNOWLEDGMENTS

The U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area, is an equal opportunity/affirmative action employer and all agency services are available without discrimination. This work was supported by the intramural fund from the U.S. Department of Agriculture. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.

We are grateful to Drs. James McClung and Eric Uthus for critical review of the manuscript. The technical support given by Karen LoneFight, Mary BriskeAnderson, Brenda Skinner, and LuAnn Johnson is greatly appreciated.