After each tissue type removal, i.e., tumoral and normal epithelium and stromal tissue (avoiding capturing endothelial and immune cells), total RNA was extracted, amplified and hybridized onto Affymetrix GeneChip

U133 X3P arrays. Genes differentially expressed between groups were identified using Limma algorithm (p < 0.01) of the Bioconductor software suite and further assessed using gene ontology analysis, performed using the GO Tree Machine tool. When compared to epithelial tumoral cells, stromal cells presented enriched categories related to “T cell receptor signaling pathway” (p = 0.004); “protein folding” (p = 0.008); and “chemotaxis” (p = 0.006). The most prominently enriched category

JNK animal study in tumoral versus normal breast epithelium were “inflammatory response” (p = 0.002) and “response to stress” (p = 0.009). The evaluation of components separately resulted in distinct signatures that should help to better understand some of the OSI-906 clinical trial molecular mechanisms involved in the complex heterotypic signaling between epithelial cells and fibroblasts. Supported by FAPESP/CNPq. Poster No. 32 HIF2alpha Overexpression Drastically Reduces HIF1alpha Protein Amounts in Melanoma Cells under Hypoxia Anne-Lise Steunou 1 , Laurence Nieto1, Eric Clottes1 1 Department of “Biologie du Cancer”, Institut de Pharmacologie et de Biologie Structurale-UMR 5089, Toulouse, France Hypoxia inducible transcription factors (HIF) are

key regulators of cellular adaptation to hypoxia in normal FK228 chemical structure but also in pathologic conditions such as cancer development. They are involved in melanocyte transformation, tumour progression and metastasis of melanoma cells. HIF is a heterodimeric protein composed of an alpha subunit regulated by oxygen pressure and a beta subunit constitutively expressed. In melanoma, HIF1a and HIF2a subunits are recovered. Although both HIFa subunits are structurally homologous, they see more exhibit different roles sometimes antagonist in the tumoral development. In order to understand these different behaviours, stable human melanoma cell lines overexpressing HIF2a protein were constructed. Surprisingly, in these cells, a decrease in HIF1a protein expression was monitored under hypoxia. HIF1a protein underexpression was inversely correlated with HIF2a protein amount. To explain this observation, transcript concentrations of HIF1a and aHIF were measured using a qRT-PCR assay. aHIF is a natural antisense of HIF1a transcript complementary to HIF1a mRNA 3′untranslated region, suspected to negatively regulate HIF1a mRNA amounts. Under hypoxia, aHIF RNA quantity was strongly increased in control transfected melanoma cells (empty vector) whereas aHIF induction was totally lost in stable cell lines overexpressing HIF2a.