Anoikis-resistant OS cells demonstrate distinct patterns of altered gene expression. A: mRNA expression of the target genes Oct4, Axin2, and Sox2 in AI-grown OS cells after the second passage (p2) was determined using qrt-PCR normalized to adherent cells. Asterisks indicate statistical significance (**p < 0.01). B: Principal component analysis of gene expression using microarray. Gene expression differences resulted in clustering of the adherent cells (squares) compared to the AI cells (triangles). This was more apparent for the patient-derived OS cells than the established OS cell lines. Blue color indicates established OS cell line, green color indicates pre-chemotherapy patient-derived OS cell line, red color indicates post-chemotherapy patient-derived OS cell line, black color indicates pulmonary metastasis patient-derived OS cell line, dotted lines connect paired AI/adherent samples. C: Shortest pathway analysis of the top 300 differentially expressed genes identifies class I HDACs, Runx2, and Akt as central contributors.