Cellular mechanisms involved in the melatonin inhibition of HT‐29 human colon cancer cell proliferation in culture

Abstract

The antiproliferative and proapoptotic properties of melatonin in human colon cancer cells in culture were recently reported. To address the mechanisms involved in these actions, HT-29 human colon cancer cells were cultured in RPMI 1640 medium supplemented with fetal bovine serum at 37 degrees C. Cell proliferation was assessed by the incorporation of [(3)H]-thymidine into DNA. Cyclic nucleotide levels, nitrite concentration, glutathione peroxidase and reductase activities, and glutathione levels were assessed after the incubation of these cells with the following drugs: melatonin membrane receptor agonists 2-iodo-melatonin, 2-iodo-N-butanoyl-5-methoxytryptamine, 5-methoxycarbonylamino-N-acetyltryptamine (GR-135,531), and the antagonists luzindole, 4-phenyl-2-propionamidotetralin, and prazosin; the melatonin nuclear receptor agonist CGP 52608, and four synthetic kynurenines analogs to melatonin 2-acetamide-4-(3-methoxyphenyl)-4-oxobutyric acid, 2-acetamide-4-(2-amino-5-methoxyphenyl)-4-oxobutyric acid, 2-butyramide-4-(3-methoxyphenyl)-4-oxobutyric acid and 2-butyramide-4-(2-amino-5-methoxyphenyl)-4-oxobutyric acid. The results show that the membrane receptors are not necessary for the antiproliferative effect of melatonin and the participation of the nuclear receptor in this effect is suggested. Moreover, the antioxidative and anti-inflammatory actions of melatonin, counteracting the oxidative status and reducing the production of nitric oxide by cultured HT-29 cells seem to be directly involved in the oncostatic properties of melatonin. Some of the synthetic kynurenines exert higher antiproliferative effects than melatonin. The results reinforce the clinical interest of melatonin due to the different mechanisms involved in its oncostatic role, and suggest a new synthetic pathway to obtain melatonin agonists with clinical applications to oncology.

Molecular mechanisms of the pro-apoptotic actions of melatonin in cancer: a review

“…However, others were not able to confirm these preliminary results [86,87], even when an inhibitory effect on tumor growth was observed at high melatonin concentrations. No effect of melatonin on apoptosis was documented by Lewinski et al [88] or by Garcìa-Navarro and co-workers [89] in HT-29 colon cancer cells. However, melatonin did promote apoptosis in an in vivo model as reported by Anisimov et al [90].…”

Apoptosis is triggered by melatonin in an in vivo model of ovarian carcinoma

“…Notably, we found a significant overexpression of p53 and BAX in papillary epithelium following either Mel therapy or EtOH intake, but not after their combination. In fact, the cytotoxic effect of Mel in tumor cells is counter-intuitive, since high levels of Mel are related to protection of normal cells and inhibition of cell proliferation (Martín et al 2006, García-Navarro et al 2007. The increase in the levels and activity of p53 was accompanied by activation of other apoptosis-related signaling pathways in liver cancer cells and LNCaP androgen-dependent prostate cancer cells treated with 1 mM Mel (Martín-Renedo et al 2008, Joo & Yoo 2009).…”

Kynurenine promotes the goblet cell differentiation of HT-29 colon carcinoma cells by modulating Wnt, Notch and AhR signals

“…Melatonin, which is synthesized from tryptophan by enzymes N-acetyltransferase and acetylserotonin methyltransferase, is produced in many tissues, including the gastrointestinal tract as well as in the pineal gland (47,48). Melatonin has been shown to inhibit proliferation of many types of cancer cells such as glioblastoma cells, colon cancer cells, and breast cancer cells (49)(50)(51). Melatonin exerts its anti-proliferative activity by inactivating FoxO-1 and NF-κB transcription factors, downregulating myosin light chain kinase expression through cross-talk with p38 MAPK, or by suppressing Notch1 signaling (49,52,53).…”