RhoA: A therapeutic target for chronic myeloid leukemia

To study expression of GTPases and actin, Western blotting and flow cytometry analysis were done, while spatial expression and colocalization of these proteins were studied by using laser confocal microscopy. To study effect of inhibitors on cell proliferation CCK-8 assay was done. Significance of differences in expression of proteins within the samples and between normal and CML was tested by using Wilcoxon signed rank test and Mann-Whitney test, respectively. Bivariate and partial correlation analyses were done to study relationship between all the parameters.In CML PMNL, actin expression and its architecture were altered and stimulation of actin polymerization was absent. Differences were also observed in expression, organization or stimulation of all the three GTPases in normal and CML PMNL. In normal PMNL, ras was the critical GTPase regulating expression of rhoGTPases and actin and actin polymerization. But in CML PMNL, rhoA took a central place. In accordance with these, treatment with rho/ROCK pathway inhibitors resulted in specific growth inhibition of CML cell lines.RhoA has emerged as the key molecule responsible for functional defects in CML PMNL and therefore can be used as a therapeutic target in CML.Chronic myeloid leukemia (CML) is characterized by the presence of Philadelphia (Ph1) chromosome bearing chimeric bcr-abl gene that translates a protein p210 which has increased and unregulated tyrosine kinase activity [1]. Polymorphonuclear leukocytes (PMNL) are terminally differentiated myeloid cells that play a crucial role in host defence by migrating to the sites of infection and eliminating foreign bodies. This complex process involves a cascade of signalling events that results in sequential stimulation of chemotaxis, phagocytosis, degranulation and oxidative burst. PMNL from CML patients exhibit defects in several actin dependent functions such as motility, chemotaxis, adhesion, aggregation, endocytosis, microbicidal activities and polymerization o