Different Types of Cell Cycle- and Apoptosis-Related Gene Expressions Alter in Corticosteroid-, Vincristine-, and Melphalan-Resistant U-266 Multiple Myeloma Cell Lines

Objective: Deregulation of the cell cycle and apoptosis mechanisms in normal cells causes many problems, including cancer. In this study, a genome-wide expression analysis of cell cycle- and apoptosis-related genes in corticosteroid-, vincristine-, and melphalan-resistant U-266 multiple myeloma cell lines was conducted. Materials and Methods: Resistant U-266 sublines were induced by application of each drug by stepwise dose increments. Resistance gained by the cells was confirmed with XTT cytotoxicity assay and microarray analyses were carried out. Among the cell cycle- and apoptosis-related gene expressions, alterations of more than 2-fold were considered significant. Results: Cyclin E2 was drastically overexpressed in the vincristine-resistant subline and a general upregulation was observed for various cyclin-dependent kinases. Some of the cyclin-dependent kinase inhibitor encoding genes were downregulated in resistant sublines in general. Tumor necrosis factor receptor genes were generally downregulated in corticosteroid- and melphalan-resistant U-266 sublines. Different types of effector caspases were downregulated in all resistant sublines. Ceramide metabolism genes seemed to be changed in favor of survival, especially in the melphalan-resistant subline. Conclusion: This report shows that different types of chemotherapeutic drugs alter different apoptotic and cell cycle-related gene expressions and, as a result, may cause drug-resistant phenotypes in U-266 multiple myeloma cell lines. Among those gene expressions, the most drastic increase in cyclin E2 could be important for the survival of vincristine-resistant U-266 cell lines, whereas alteration of ceramide metabolism genes could be important in melphalan resistance.