Immunocytochemical Study of Microtubule Reorganization in Induced Differentiated Leukemia Cells by Retinoic Acid

Microtubules are important components of cell cytoskeleton which participate in mitosis, protein localization and cell signaling. They are also the targets of several anticancer agents which indicating their importance in maintaining cell viability. Capacity of leukemia cells to re-organize their microtubules is considered an integral part of differentiation of these cells to mature granulocytes by all-trans retinoic acid (ATRA), which is an establish drug for treating acute promyelocytic leukemia. In this study we examined alpha-, alpha-acetylated and gamma-tubulin content, their patterns of distribution in the cytoplasm and the potency of centrosomes in reorganizing microtubules in different stages of ATRA-induced differentiation of HL-60 cell line. Results have shown that gamma-tubulin content was increased with a focal centrosomal accumulation of gamma-tubulin following differentiation. Differentiated cells had the ability to re-organize their microtubule network following nocodazole challenge test, whereas undifferentiated cells did not show such ability. Alpha-tubulin was more regularly organized in differentiated cells and acetylated alpha-tubulin generally followed the same organization patterns after differentiation as occurred for alpha-tubulin. Our results is suggestive of a centrosomal, and organized nucleation pattern of microtubules in HL-60 cells following differentiation possibly mediated through upregulation of gamma-tubulin.