Endothelin-1 and Endothelin-3 Promote Invasive Behavior via Hypoxia-Inducible Factor-1α in Human Melanoma Cells

Abstract

Endothelin (ET) B receptor (ET B R), which is overexpressed in human cutaneous melanomas, promotes tumorigenesis upon activation by ET-1 or ET-3, thus representing a potential novel therapeutic target. Hypoxia-inducible factor-1A (HIF-1A) is the transcriptional factor that conveys signaling elicited by hypoxia and growth factor receptors. Here, we investigated the interplay between ET axis and hypoxia in primary and metastatic melanoma cell lines. We report that under normoxic conditions, ET B R activation by ET-1/ET-3 enhances vascular endothelial growth factor (VEGF) up-regulation, cyclooxygenase (COX)-1/COX-2 protein expression and COX-2 promoter activity, prostaglandin E 2 (PGE 2 ) production, and do so to a greater extent under hypoxia. Moreover, COX-1/COX-2 inhibitors block ET-induced PGE 2 and VEGF secretion, matrix metalloproteinase (MMP) activation, and cell invasion, indicating that both enzymes function as downstream mediators of ET-induced invasive properties. The ET B R selective antagonist BQ788 or transfection with ET B R small interfering RNA (siRNA) block the ET-mediated effects. ETs also increase HIF-1A expression under both normoxic and hypoxic conditions and its silencing by siRNA desensitizes COX-2 transcriptional activity, PGE 2 and VEGF production, and MMP activation in response to ET-3, implicating, for the first time, HIF-1A/COX as downstream targets of ET B R signaling leading to invasiveness. In melanoma xenografts, specific ET B R antagonist suppresses tumor growth, neovascularization, and invasiveness-related factors. Collectively, these results identify a new mechanism whereby ET-1/ET-3/ET B R axis can promote and interact with the HIF-1A-dependent machinery to amplify the COX-mediated invasive behavior of melanoma. New therapeutic strategies using specific ET B R antagonist could provide an improved approach to the treatment of melanoma by inhibiting tumor growth and progression. [Cancer Res 2007;67(4):1725-34]

Patterns of GRP78 and MTJ1 expression in primary cutaneous malignant melanoma

“…In its traditional role as a heat shock protein of the HSP 70 family, GRP78 and other related proteins function in response to cellular stress. 53 As melanomas progress and invade into deeper levels, there are concomitant changes in a number of microenvironmental physical conditions, 54,55 of which hypoxia is paramount, which has been shown to trigger a number of molecular cascades in melanoma cell lines. 56,57 In fact, hypoxic stress by itself leads to an increased expression of GRP78 in cultured human fibrosarcoma cells.…”

Endothelins and hypoxia-inducible factor in cancer

“…Inhibition of human ovarian tumour growth in nude mice after treatment with Atrasentan is associated with reduced VEGF and microvessel density (Spinella et al 2004b). In primary and metastatic melanoma cell lines in normoxic conditions, ET-1 or ET-3 binding to ET-RB increases HIF-1a protein and subsequently upregulates VEGF, COX-1/COX-2 (cyclo-oxygenase) protein expression and COX-2 promoter activity, PGE 2 production, and does so to a greater extent under hypoxia (Spinella et al 2007). Silencing HIF-1a by siRNA prevents ET-mediated COX-2 transcriptional activity, PGE 2 and VEGF production, and MMP activation.…”

Inactivation of the HIF-1α/PDK3 Signaling Axis Drives Melanoma toward Mitochondrial Oxidative Metabolism and Potentiates the Therapeutic Activity of Pro-Oxidants

“…For instance, melanoma antigen-11 regulates HIF-1 accumulation by inhibition of prolyl hydroxylase activity (14). Endothelin or the antiapoptotic protein, Bcl-2, induces HIF-1a accumulation (15,16). Genetic alterations, such as Microphthalmia-Associated Transcription Factor (MITF) germline mutation (17) or the oncogenic V600E BRAF mutation (18) overexpress HIF-1a and enhance transcriptional activity of downstream genes.…”