TNFRSF9 and mesothelioma: To confirm whether or not the gene expression pattern observed in mesothelioma cells is specific to these cells, we selected six genes, IL-32, TNFRSF9, AREG, ERBB3, ATP6V0D2, and DMGDH whose expressions were observed to increase more than three-fold at acidic pH using a microarray, and examined their expressions in various cells.