Mesothelioma and Hypoxia: Modulation of the Inflammation-Related Phenotype and Identification of Prognostic Markers

Objective: Malignant Mesothelioma is an aggressive tumor occurring in the context of chronic inflammation and characterized by hypoxic areas. This study explores how hypoxia impacts on the pro-inflammatory phenotype of MSTO-211H and MPP89 mesothelioma cells and investigates the role of HIF-1 alpha and NF-kB in this process. The prognostic values of two molecules upregulated by oxygen deprivation, HIF-3 alpha and CXCR4, is also analyzed. Methods: Hypoxic condition was obtained in a sealed modular incubator chamber flushed with 1% O2. mRNA and protein levels were evaluated by Real-Time PCR and Western Blot. Silencing of HIF-1 alpha was achieved by specific shRNA and NF-kB inhibition by parthenolide treatment. HIF-3 alpha and CXCR4 expression in tumor tissues from mesothelioma patients was detected by immunohistochemistry. Results: The hypoxic stimulation of mesothelioma cells induced an early activation of HIF-1 alpha and NF-kB and a later increase of HIF-3 alpha expression. In addition, the upregulation of a set of inflammation-related genes was observed. Silencing of HIF-1 alpha and treatment with parthenolide highlighted that the observed increase in gene expression depends on both HIF-1 alpha and NF-kB transcriptional activity. A correlation between high expression of CXCR4 in human mesothelioma samples and poor survival was also observed and HIF-3 alpha was suggested as a potential new prognostic marker. Conclusions: This study evidences a cross-talk between hypoxia adaptation and pro-inflammatory phenotype in mesothelioma accomplished through the combined transactivation activity of HIFs and NFkB. Immunohistochemistry analysis of tissue samples confirms CXCR4 and suggests HIF-3 alpha as potential prognostic markers for mesothelioma.