Characterization of FAK-p53 relationship in Chronic Lymphocytic Leukemia cells

Despite the many advances made in recent decades in the treatment of chronic lymphocytic leukemia (CLL), this still represents an incurable disease. Consequently, the need to find new therapeutic targets is of primary importance. Recent literature suggests that focal adhesion kinase (FAK), a protein with a key role in several solid tumors but understudied in hematological malignancies, could be involved in CLL pathogenesis and evolution. Therefore, investigating FAK in CLL may lead to the development of new therapies. In this scenario, considering the prognostic value of TP53 aberrations in CLL and the evidence of a reciprocal regulation between FAK and p53 in solid tumors, this PhD project aimed to determine whether a functional relationship between these two proteins exists also in CLL. Western-blot (WB) analysis revealed significant overexpression of wild type p53 protein (p<0.01) and higher activation of FAK (in terms of phosphorylation at Y397 residue – pFAK-Y397, p<0.001) in basal conditions in CLL than in normal B cells, with a significant correlation between their expression levels in CLL cells (p<0.05, r=0.41). WB and immunofluorescence (IF) demonstrated FAK and p53 presence in both cytoplasm and nucleus of CLL cells, with higher nuclear localization of p53 (p<0.0001) and pFAK-Y397 (p<0.001). Accordingly, preliminary results from IF revealed that FAK and p53 co-localize in both compartments of CLL cells. Coherently, preliminary immunoprecipitation assay revealed physical interaction between FAK and p53 also in CLL cells. Finally, adopting a loss-of-function approach, we further demonstrated that FAK kinase inhibition reduced p53 protein expression by about 20% in CLL cells (p<0.05). Overall, this study provides insights supporting a possible reciprocal regulation between FAK and p53 also in CLL. At the same time, our results suggest a new perspective on p53 role in CLL biology, indicating a more complex function than its classical tumor-suppressive activity. Continuing this research could potentially unveil a novel druggable molecular axis in CLL biology.