Hsp90α and β are down-regulated by combined disruption of the IL-6R/STAT3 and the Ras/MAPK pathways in INA-6 and ANBL-6 cells. (A) Hierarchic clustering analysis of gene-expression profiles of INA-6 cells using the Affymetrix GeneChip U133A platform. Combined blockade of the IL-6R/STAT3 and the Ras/MAPK pathways in INA-6 cells caused a pattern of differently expressed genes (lane 5). HSP90α and HSP90β were found among the down-regulated genes. INA-6 cells were cultured in the presence of primary BMSCs and either treated with 50 μg/mL Sant7 (lane 1) or 50 μM PD98059 (lane 2) or a combination of both for 30 hours (lane 5). As control, INA-6 cells were kept either in the presence of BMSCs (lane 3) or only in medium supplemented with 2 ng/mL IL-6 (lane 4) and treated with DMSO. (B) Western blot analysis of Hsp90α, Hsp90β, or total Hsp90 protein expression in INA-6 and ANBL-6 cells after different drug-exposure regimens. INA-6 or ANBL-6 cells were cultured in the presence of primary BMSCs and treated with 50 μg/mL Sant7 (lane 2) or 50 μM PD98059 (lane 3) or a combination of both for 20 hours (lane 4). (C) Western blot analysis of Hsp90α, Hsp90β, or total Hsp90 protein expression in INA-6 cells cultured either without IL-6 or in the presence of BMSCs. Equal loading was assessed through immunostaining of β-actin.