In vitro and in vivo antitumor effect of 2‐methoxyestradiol on human melanoma

Abstract

2-methoxyestradiol (2ME 2 ) is an endogenous metabolite of estradiol with estrogen-receptor-independent antitumor and antiangiogenic activity. We examined the effects of 2ME 2 on the cellular proliferation of 8 human melanoma cell lines. We show that 2ME 2 inhibited cell proliferation by inducing apoptosis and an arrest in the G 2 /M phase, and the mechanism of action involved microtubules, mitochondrial damage and caspase activation. In male SCID mice, 2ME 2 was effective in reducing primary tumor weight and the number of liver metastases after intrasplenic injection of human melanoma cells. In the metastases, we found a significantly higher rate of apoptotic cells after 2ME 2 treatment. These findings on the antitumor effect of 2ME 2 in cell culture as well as in an animal model may have implications for designing alternative treatment options for patients with advanced malignant melanoma. © 2004 Wiley-Liss, Inc. Key words: 2-methoxyestradiol; melanoma; apoptosis; metastasisThe possibility that endocrine factors may influence the clinical course of human malignant melanoma is suggested by the higher survival rate in premenopausal vs. postmenopausal women or men of any ages. 1,2 The epidemiological data were supported by studies using melanoma cell lines grown in experimental animals. 3,4 Our previous experiments showed that intrasplenic injection of human melanoma cells resulted in a significantly higher number of liver metastases in male than in female SCID mice. 5 On the other hand, investigations on the sex hormone receptor status of human cutaneous melanomas yielded conflicting results; while earlier studies applying biochemical methods for the detection of estrogen receptors (ER) gave positive results in some cases, other approaches using monoclonal anti-ER antibodies generally failed to demonstrate the presence of type I receptors in melanoma tissues. 1,6 It has been suggested that low-affinity type II ERs may be responsible for the observed hormone binding. Nevertheless, most investigators have shown the lack of an effect of estrogens on the proliferative activity of human melanoma cells. 7,8 There are less data available on the presence of other sex hormone receptors (progesterone and androgens) and their effect on the biological behavior of melanoma cells. 1,9 One possible mechanism behind the observed female superiority in survival of melanoma patients is the tumor growth inhibitory effect of 2-methoxyestradiol (2ME 2 ), an endogenous metabolite of estradiol exerting its activities independently of the ERs. 2ME 2 is formed by the sequential hydroxylation and methylation at the 2-position; it is produced during the normal route of detoxification, especially in the liver, and excreted through the urinary system. 10 -12 This is the only estradiol metabolite devoid of estrogenic activity in vivo and has no known physiological function. Its affinity to ER␣ and to ER␤ is 500-fold and 3,200-fold lower than that of estradiol, respectively, and its activity is independent of the presence of estrogen receptor...

2-Methoxyestradiol: New perspectives in colon carcinoma treatment

“…The comparison between other cancer cell lines characterized by a different p53 behaviour will allow a better definition of the p53-independent role of p21. The effects of 2-ME on cell cycle we observed are in M a n u s c r i p t 13 agreement with previous reports on other cancer cell lines (Kumar et al 2001;Lin et al 2001;Dobos et al 2004;Li et al 2004;Kar et al 2008;Maran et al 2008). The above observations prompted us to investigate the possible pro-apoptotic effect of 2-ME.…”

“…We did not observe a marked effect of 2-ME on cell viability (data not shown), in line with the original observation by Seegers et al (1997), who demonstrated that normal human skin fibroblasts are not affected by 2-ME. Accordingly, the comparison between normal human fibroblasts and melanoma cell lines revealed that the former cells were not sensitive to the treatment (Dobos et al 2004). The loss of effect of 2-ME on normal cells was also supported by the report by Van Zijl et al (2008), showing that breast cancer MCF-7 cells are sensitive to 2-ME while their normal counterpart (i.e.…”

NQO1-activated phenothiazinium redox cyclers for the targeted bioreductive induction of cancer cell apoptosis

“…2A and B, it was demonstrated that TB-induced melanoma cell death (I) depends on caspase activation as evidenced by cell protection by pretreatment with the pan-caspase inhibitor Z-VAD(OMe)-fmk (Fig. 3C) [38], (II) does not depend on caspase 8-activation as evidenced by the lack of protective effects of pretreatment with the cell-permeable caspase 8 inhibitor peptide Ac-AAVALLPAVLLALLAP-IETD-CHO (Fig. 3C) [38], and (III) occurs dose dependently with activation of caspase-3 as evidenced by flow cytometric detection of cleaved procaspase-3 (Fig.…”

Association of microvessel density with infiltrating cells in human cutaneous malignant melanoma

“…57 On the other hand, the endogenous estrogen metabolite, 2-methoxyestradiol has been reported to inhibit endothelial cell proliferation, as well as angiogenesis, tumor growth and metastasis in several tumor types, including melanoma. 16,20,52 Medroxyprogesterone also inhibited growth and vascularization of melanoma in the rabbit cornea. 23 Androgens may stimulate angiogenesis through regulation of VEGF levels via the activation of HIF, 39 or through suppressing the secretion of thrombospondin-1, an angiogenesis inhibitor.…”