Inhibition of Src Reduces Cortactin Phosphorylation and Transendothelial Migration of Acute Lymphoblastic Leukemia B cells

Abstract

B‐cell acute lymphoblastic leukemia (B‐ALL) is the most common leukemia in children and adults. B‐ALL cells have the ability to extravasate and infiltrate bone marrow and organs such as lungs, testis and central nervous system (CNS). Dynamic actin cytoskeletal remodeling is needed to accomplish transendothelial migration. Cortactin is an actin‐binding protein which accumulates in lamellipodia and invadopodia and regulates neutrophil transendothelial migration during inflammation. Recently, we showed that cortactin is overexpressed in B‐cells of B‐ALL patients, and significantly correlates with bone marrow colonization, organ infiltration, drug resistance and disease relapse. Cortactin is a target for several posttranslational modifications such as phosphorylation and acetylation, being first discovered as a substrate of Src kinase and recently as substrate of the histone deacetylases SIRT1 and HDAC6. Phosphorylation of cortactin is thought to lead to lamellipodia and invadopodia protusion, whereas acetylation diminishes the affinity of cortactin to F‐actin, decreases cell migration capability, and may lead to nuclear translocation. However, it remains to be explored whether these modifications are required for the aggressiveness of leukemic B‐ALL cells. Thus, in this study, we analyzed the importance of such modifications for transendothelial migration and bone marrow organoid colonization. A MTT (3‐(4, 5‐dimethylthiazolyl‐2)‐2, 5‐diphenyltetrazolium bromide) assay was performed to determine effects of certain pharmacological inhibitors of posttranslational modifications on cell viability. To this end, REH cells were incubated with the indicated pharmacological compounds for 24 hours at different concentrations (50 to 150 mM). The IC50 value for PP2 (Src inhibitor) was 190.82 mM, for EX‐527 (SIRT1 inhibitor) was 190.94 mM, for Tubacin (HDAC6 inhibitor) was 41.39 mM, and for Tubastatin‐A (HDAC6 inhibitor) was 94.09 mM. Importantly, after 20 min of treatment of only REH cells with PP2 at 20 μM, REH cells transmigrated significantly less across CXCL12‐stimulated HUVEC monolayers, which may be due to a reduction of phosphorylated cortactin that impairs cytoskeletal remodeling needed for migration of the cells. Taken together, these results suggest that cortactin phosphorylation may be needed by leukemic B cells to achieve transmigration and may reveal cortactin as a potential new therapeutic target for high risk B‐ALL patients to prevent disease relapse.Support or Funding InformationCONACyTThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.