Increased expression of iNOS and COX-2 has been reported in various other tumors [17], and other studies have demonstrated a correlation between the expression of iNOS and NT and that of COX-2 [18] and their spatial co-localization with TAM infiltration and VEGF expression [19] and [20]. Our data suggest a role for TAMs and COX-2 expression in the up-regulation of expression of iNOS and NT in the tumor stroma. Furthermore, the abundant expression of COX-2 along with iNOS and NT in the tumor stroma may have induced HIF-1 expression in the tumors, and this, in turn, may also

upregulate the expression of VEGF. One of the predominant inflammatory protein markers overexpressed in all of our WTs was COX-2, selleck which was highly selleck inhibitor expressed

in the tumor stroma and, to a lesser degree, in all other tumor components. The COX-2 expression was further confirmed in the mouse model of WT, which has shown a similar expression pattern with the human tumors. This spatial expression is in marked contrast to the findings of previous studies that reported moderate to strong cytoplasmic expression of COX-2 in blastemal and epithelial components of the tumors but no expression in the tumor stroma [8]. Various mechanisms could be responsible, individually or in combination, for the abundant COX-2 expression in WTs. First, the infiltrating immune cells themselves could be overexpressing COX-2. Second, tumor fibroblasts could be generating COX-2 in

response to macrophage infiltration or the inflammatory tumor microenvironment. Third, COX-2 expression in these tumors may be induced by fetal mitogen IGF2 through the Ras/Raf/Mitogen-activated protein kinase kinase also known as MEK/ERK pathway, as has been reported in human keratinocytes [21]. Overexpression of IGF2 has been reported in various cancers [22], [23], [24] and [25], including 70% of WTs [26] and [27]. We have previously reported upregulated p-ERK1/2 expression in mouse WTs engineered to overexpress IGF2 and also in human WTs [9], suggesting a role for ERK signaling in WT development. The robust expression of COX-2 and p-ERK1/2 we observed in the current series of tumors Calpain further suggests that one consequence of IGF2 over expression in WTs is COX-2 up-regulation and promotion of an inflammatory microenvironment and that this effect is mediated by enhanced p-ERK signaling. COX-2 can also activate the expression of HIF-1 through its enzymatic product prostaglandin E2[21] and [28]. The expression of COX-2 and HIF-1 was spatially similar in the tumors we assessed. HIF-1 expression was predominantly nuclear in the tumor stroma, with granular cytoplasmic and membranous expression in blastemal and epithelial regions, which is consistent with a previous report [5]. COX-2 activation of HIF-1 can also occur through hypoxia [5] or hypoxia-independent mechanisms [29], the latter involving p-ERK1/2 [30].