The dietary phytochemical chlorophyllin alters E-cadherin and beta-catenin expression in human colon cancer cells

Abstract

Chlorophyllin (CHL), an anticarcinogenic and antimutagenic water-soluble derivative of chlorophyll, has been reported to induce apoptosis in human colon cancer cells via a pathway involving cell differentiation. Induction of differentiation markers may be important in limiting cancer-cell invasion and metastasis, and there is much interest in understanding the underlying mechanisms, because this might provide insights for cancer chemotherapy. In the present study, human HCT116 colon-cancer cells were treated with CHL, and the expression levels of E-cadherin and beta-catenin were examined using immunocytochemistry and laser scanning confocal microscopy. E-cadherin was detected almost exclusively at the cell periphery of cancer cells treated with or without CHL, but the expression of E-cadherin in the plasma membrane was markedly elevated in the cells treated with CHL. beta-Catenin also was strongly expressed in the plasma membrane, especially after CHL treatment. No change in the expression of beta-catenin mRNA was detected across a broad range of CHL concentrations (10-500 micromol/L), but there was a concentration-dependent decrease in nuclear beta-catenin protein levels without overt changes in the cytosolic pool of beta-catenin. Our interpretation of these findings is that CHL induces E-cadherin expression, and this facilitates trafficking of beta-catenin away from the nucleus and into the plasma membrane, possibly for destruction via the adherins junction remodeling (Hakai) pathway.

FIGURE 1

Comparison of the chemical structures of CHL and chlorophyll a.

FIGURE 2

Confocal microscopy analyses of HCT116 human colon cancer cells treated with CHL at 100 μmol/L, showing enhanced membrane localization of E-cadherin (B) and β-catenin (D) compared with the corresponding controls (A and C, respectively). A color version is available online from the posting of the article at www.nutrition.org.

FIGURE 3

A. RT-PCR analysis of β-catenin in HCT116 cells 24 h after incubation with CHL showed no increased messenger RNA. B. Immunoblot analyses of cellular fractions from HCT116 cells treated with CHL showed a concentration-dependent decrease in nuclear β-catenin. Histone H1, nuclear loading control. Wedge symbol, CHL at 0–250 μmol/L.