Nuclear alpha v beta 3 integrin expression, post translational modifications and regulation in hematological malignancies

alpha v beta 3 integrin, a plasma membrane protein, is amply expressed on an array of tumors. We identified nuclear alpha v beta 3 pool in ovarian cancer cells and were interested to explore this phenomenon in two rare and aggressive types of leukemia, T-cell acute lymphoblastic leukemia (T-ALL) and Mast cell leukemia (MCL) using Jurkat and HMC-1 cell lines, respectively. Moreover, we collected primary cells from patients with chronic lymphocytic leukemia (CLL, n = 11), the most common chronic adult leukemia and used human lymphoblastoid cell lines (LCL) generated from normal B cells. Nuclear alpha v beta 3 integrin was assessed by Western blots, confocal microscopy, and the ImageStream technology which combines flow-cytometry with microscopy. We further examined post translational modifications (phosphorylation/glycosylation), nuclear trafficking regulation using inhibitors for MAPK (U0126) and PI3K (LY294002), as well as nuclear interactions by performing Co-immunoprecipitation (Co-IP). alpha v beta 3 integrin was identified in all cell models within the nucleus and is N-glycosylated. In primary CLL cells the beta 3 integrin monomer is tyrosine Y759 phosphorylated, suggesting an active receptor conformation. MAPK and PI3K inhibition in Jurkat and CLL cells led to alpha v beta 3 enhancement in the nucleus and a reduction in the membrane. The nuclear alpha v beta 3 integrin interacts with ERK, Histone H3 and Lamin B1 in Jurkat, Histone H3 in CLL cells, but not in control LCL cells. To conclude, this observational study provides the identification of nuclear alpha v beta 3 in hematological malignancies and lays the basis for novel cancer-relevant actions, which may be independent from the membrane functions.