Nuclear chromatin patterns in 3 glucocorticoid-resistant RPMI 8226 human myeloma cell sub-lines: Correlations with cell growth and immunological phenotype

Nuclear morphological alterations associated with glucocorticoid resistance in human myeloma were evaluated by image cytometry in three human myeloma RPMI 8226 cell sub-lines. Resistance was induced by drug selection using prednisone (8226p), methyl-prednisolone (8226m) and dexamethasone (8226d), respectively. All these three cell sublines displayed significant glucocorticoid-resistance without cross-resistance to doxorubicin. Nuclear geometry and texture were analyzed on G₀/G₁-selected cell nuclei and data compared with cell growth characteristics and membrane expression of CD23, CD38, CD44, and CD58 antigens. When compared to the parental RPMI 8226 cell line, glucocorticoid-resistant cells display a progressive chromatin condensation with heterogeneously distributed large chromatin clumps, a phenomenon not observed in the multidrug-resistant CEM-VLB cells. These alterations were correlated to the resistance index against glucocorticoids and to the expressions of CD38, and of CD44 variant forms CD44v5 and CD44v7-8 antigens. These data suggest that glucocorticoid resistance in RPMI 8226 cells could be associated with sub-visual specific higher-order chromatin organization changes. Furthermore, these alterations are correlated to the expression of membrane markers associated with tumors aggressiveness.