Immunocytochemical study on microtubule reorganization in HL-60 leukemia cells undergoing apoptosis.

BACKGROUND Microtubules (MT) are important components of cell cytoskeleton and play key roles in cell motility mitosis and meiosis. They are also the targets of several anticancer agents which indicating their importance in maintaining cell viability. Microtubular reorganization contributing to apoptotic morphology occurs in normal and neoplastic cells undergoing apoptosis induced by cytotoxic drugs. The aim of this study was to correlate the changes in the MT with behavior of the gamma-tubulin in apoptotic cell, and to see if apoptitic MT showed biochemical characteristics of stable MT. METHODS Apoptosis was induced in the human leukemia cells (HL-60) by treatment with 1 microM of all-trans retinoic acid over a 5-day period. The time course of changes was assessed using flow cytometry, DNA fragmentation and immunocytochemistry in cells labeled for alpha-tubulins, acetylated alpha-tubulin and gamma-tubulin. RESULTS The results indicated that gamma-tubulin content is increased after cells have gone through the apoptosis with a diffuse cytoplasmic pattern. Alpha-tubulin did not reveal any specific pattern of polymerization in apoptotic cells and acetylated alpha-tubulin content was also decreased in comparison with non-apoptotic cells. CONCLUSION Our results support the idea that microtubule reorganization is an important factor of the mammalian cells response to apoptosis, and the altered properties of the MT did not reflect changes in function as apoptosis progresses.