Involvement of adrenomedullin induced by hypoxia in angiogenesis in human renal cell carcinoma

Abstract

Background : Adrenomedullin (AM) has pluripotent activities and is involved in the regulation of vasomotor tone, cell differentiation and embryogenesis. However, the expression and pathophysiological role of AM has not been determined in human renal cell carcinoma (RCC). Methods : Twenty-six RCC specimens and three cultured human RCC cell lines (A498, SN12C and KPK-13) were analyzed. Expression of AM was determined by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) analysis. The correlation between AM expression and microvessel count (MVC) in RCC specimens was examined to determine if AM plays a role in tumor angiogenesis. The correlation between the expression of AM and vascular endothelial growth factor (VEGF) was also investigated. Lastly, the effect of hypoxia upon the mRNA expression of AM, VEGF and hypoxia inducible factor-1 (HIF-1) by RCC cell lines was determined. Results : Immunohistochemistry indicated that AM and VEGF were primarily localized in the cytosol of RCC cells. AM and VEGF mRNA were detected in all RCC specimens and cultured RCC cell lines analyzed by RT-PCR. There was a positive correlation between AM mRNA expression and MVC ( r = 0.516, P = 0.0062), and between VEGF mRNA expression and MVC ( r = 0.485, P = 0.0111). We also observed a positive correlation between AM mRNA expression and VEGF mRNA expression ( r = 0.552, P = 0.0029). Hypoxia significantly induced AM and VEGF mRNA expression, although the increase of the AM mRNA level (10.6-26.7 fold) was markedly greater than that of the VEGF mRNA level (1.5-1.9 fold). Conclusion : These results suggest that hypoxia-induced AM plays a part in tumor angiogenesis in conjunction with VEGF and facilitates human RCC growth under hypoxic conditions.

Adrenomedullin antagonist suppresses tumor formation in renal cell carcinoma through inhibitory effects on tumor endothelial cells and endothelial progenitor mobilization

“…HIF-1-inducible genes include angiogenic factors such as vascular endothelial growth factor (VEGF), platelet-derived growth factor, basic fibroblast growth factor, and adrenomedullin (AM) (4,5). Among these angiogenic factors, we have been examining the role of AM in tumor formation by pancreatic cancer cells, and found that the increase in the AM mRNA level under hypoxia was markedly greater than that in the VEGF mRNA level in accordance with a previous report (6). We demonstrated that the intratumoral injection of an adrenomedullin antagonist (AMA) inhibited tumor growth in a pancreatic cancer cell line in a xenograft mouse model (7).…”

Adrenomedullin prevents apoptosis in prostate cancer cells

“…AM also promotes tumor angiogenesis and enhances VEGF [35], and MMP-2 [36] levels, and is highly expressed in hypoxic tumors [37,38]. In renal cell carcinoma cells, hypoxia leads to AM and VEGF expression, which act in a coordinate way to facilitate cell growth [37]. All this could have therapeutical implications in cancer treatment, since it seems clear from different studies that AM provides resistance to stress and induced-cell death.…”

“…In this regard, AM could represent a putative tumor marker to predict response to radio-or chemotherapy, although this possibility has not been yet tested. AM also promotes tumor angiogenesis and enhances VEGF [35], and MMP-2 [36] levels, and is highly expressed in hypoxic tumors [37,38]. In renal cell carcinoma cells, hypoxia leads to AM and VEGF expression, which act in a coordinate way to facilitate cell growth [37].…”

Vinblastine inhibits the angiogenic response induced by adrenomedullin in vitro and in vivo

“…Recently, it has been demonstrated by several groups that ADM is protumorigenic by stimulating carcinoma cell growth and angiogenesis directly (Fujita et al, 2002;Hague et al, 2000;Martinez et al, 2002;Oehler et al, 2002;Ishikawa et al, 2003). As such, ADM is identified as a novel target for antiangiogenic therapy.…”

“…Human breast cancer cell lines overexpressing ADM displayed an increased angiogenic potential both in vitro and in vivo (Martinez et al, 2002). ADM and vascular endothelial growth factor (VEGF) are the most widely expressed angiogenic factors in uterine leiomyomas (Hague et al, 2000), while ADM expressed in human renal cell carcinoma is induced by hypoxia and coexpression of ADM and VEGF, indicating that ADM may increase blood flow by vasodilation in the tumor vessels induced by VEGF and subsequently promote tumor growth (Fujita et al, 2002). Ishikawa et al (2003) demonstrated that ADM antagonist significantly reduced the in vivo growth of a pancreatic cancer cell line indirectly, by suppressing the formation of large functional blood vessels in the tumor tissues, leading to depletion of nutrient and oxygen supply.…”