Increased expression of USP6, USP27x, USP41 and USP43 in OS cell lines. (A) Heatmap of the 56 USP genes in MSCs, osteoblasts (MSCs treated with differentiation medium up to 14 days after proliferation phase) and OS cell lines (KHOS, 143B, HOS, MG63, G292, U2OS, SAOS2). Counts were variance stabilized and transformed to z-scores. (B) Normalized expression levels of USP genes (USP6, USP27x, USP41, USP43) in MSCs, osteoblasts (MSCs treated with differentiation medium up to 14 days after proliferation phase) and OS cell lines (KHOS, 143B, HOS, MG63, G292, U2OS, SAOS2). OS cell lines were gathered together within the OS group and pair-wise gene expression comparison was performed using Wald Test. All of the genes represented here are significantly differentially expressed (|Log2 FC| > 1, **** adj. p value ≤ 0.0001) in comparison OS vs. MSCs and OS vs. OB (MSCs differentiated into osteoblasts). (C) MSCs from healthy volunteers and three OS cell lines (HOS, MG63 and U2OS) were cultured. At 80% confluence, RNAs were extracted and USP6, USP27x, USP41 and USP43 mRNA steady-state levels were quantified by RT-qPCR analysis (bars indicate means ± SD of 3 independent experiments, each performed in triplicate, * p < 0.05).