Endothelin-receptor antagonists are proapoptotic and antiproliferative in human colon cancer cells

Abstract

Endothelin (ET)-1 can act as an autocrine/paracrine growth factor or an antiapoptotic factor in human cancers. To study the role of ET-1 in human colon cancer, proliferation and apoptosis of colon carcinoma cells was investigated using human HT-29 and SW480 colon carcinoma cells. ET-1 was secreted by these cells. Treatment of cells with bosentan, a dual ET A/B -receptor antagonist, decreased cell number. Inhibition of DNA synthesis by bosentan was observed only in the presence of serum. Exogenously added ET-1 did not increase DNA synthesis in serum-deprived cells. SW480 cells were sensitive and HT-29 cells were resistant to FasLinduced apoptosis. Bosentan sensitised resistant HT-29 cells to FasL-induced, caspase-mediated apoptosis, but not to TNF-a-induced apoptosis. Bosentan and/or FasLigand (FasL) did not modulate the expression of caspase-8 or FLIP. Bosentan sensitisation to apoptosis was reversed by low concentrations (10 À13 -10 À10 M), but not by high concentrations (10 À9 -10 À7 M) of ET-1. These results suggest that the binding of ET-1 to high-affinity sites inhibits FasL-induced apoptosis, while the binding of either ET-1 or receptor antagonists to low-affinity sites promotes FasL-induced apoptosis. In conclusion, endothelin signalling pathways do not induce human colon cancer cell proliferation, but are survival signals controling resistance to apoptosis.

Expression of Tie‐2 in human peripheral and autonomic nervous system

“…Tie‐2 may also control cell survival involving the PI3K and Akt kinase signalling pathways [15,18]. This function of Tie‐2 and the positive Tie‐2 staining of neural ganglia in the colon mucosa, the epithelial layer in colon and the endothelium of the vasculature is comparable with previous results of our group concerning the distribution and the anti‐apoptotic functions of the ET‐1 peptide in human colon and colon carcinoma vasculature, epitheliun and myenteric plexus [5–7,20]. Indeed, we had previously observed a similar pattern for cellular distribution for Tie‐2 and ET‐1 in the human colon, which we confirm here in the feminine urogenital tract.…”

“…Endogenous peroxidase activity was quenched with 3% hydrogen peroxide in methanol for 10 min. Sections were washed in water, boiled for 5 min in a microwave oven in citric acid and incubated with rabbit polyclonal anti‐Tie‐2 (diluted 1 : 200 in citrate buffer containing 0.1% Tween) (Santa Cruz Biotechnology, Santa Cruz, CA, USA), endothelin‐1 (ET‐1) [20], neurone‐specific enolase (NSE) (dilution 1 : 100) or glial fibrillary acidic protein (GFAP) (dilution 1 : 500) (both from Dako, Hamburg, Germany) primary antibodies. Sections were washed in phosphate‐buffered saline and incubated with biotinylated secondary antibodies (1 : 300 dilution) (Dako).…”

Endothelin Receptors and Pain

“…The ET A receptor mediates ET-1’s effects in prostate, ovarian, breast, renal, bladder, cervical cancer and bone malignancies, 8,40, 88, 100, 182, 202, 223 while both ET A and ET B receptor subtypes are presumably responsible for ET-1’s actions in colon cancer and Kaposi’s sarcoma. 180, 201 Endothelins also modulate the trafficking, differentiation and activation of tumor-infiltrating immune cells. 10, 85…”

The prognostic value of circulating big endothelin‐1 in patients undergoing potentially curative resection for colorectal cancer

“…In vitro , ET‐1 stimulates CRC cell proliferation through ET A R [15], mediated via pertussis toxin‐sensitive G proteins, phosphoinositide 3‐kinase, protein kinase C and transactivation of the epidermal growth factor receptor [16]. Endothelin‐1 may also act as a survival factor, protecting CRC cells against Fas ligand (FasL)‐induced apoptosis [17]. Endothelin‐1 is also a direct target of β‐catenin and can rescue colon cancer cells from growth arrest and apoptosis resulting from inhibition of β‐catenin signalling, suggesting a key role for ET‐1 in the oncogenic function of β‐catenin [18].…”