Diagnostic and prognostic role of eEF1A in chronic lymphocytic leukaemia

Background. Chronic lymphocytic leukaemia (CLL), the most common form of leukaemia in adults in Western countries, is characterized by the clonal expansion of B cells. Despite major advances in CLL therapy/diagnosis, the medical approach to CLL can be further improved. Here we explore the potential diagnostic/therapeutic role of the elongation factor 1 A (eEF1A) in CLL. Two major isoforms of eEF1A proteins exist: the ubiquitous eEF1A1 and the tissue-specialized eEF1A2. Beside their role in the elongation step of translation, both isoforms are involved in different cellular processes such as cell proliferation and apoptosis. Whereas both eEF1A isoforms play a role in solid and hematologic human tumors, nothing is known in CLL. Methods. eEF1A1/eEF1A2 amounts were quantitated by quantitative real time PCR and western blotting in the lymphocytes of 46 CLL patients vs 26 normal control. eEF1A1 functional role in CLL was investigated in a cellular (MEC-1) and in a subcutaneous xenograft animal model of CLL via its targeting by an aptamer (GT75) or a siRNA (siA1), we previously developed. As control molecules an inactive aptamer (CT75) or siRNA (siGL2) were used. Results. At the mRNA level, eEF1A1 but not eEF1A2 was significantly (p=0,0081) more elevated in CLL lymphocytes compared to control. At the protein level, both eEF1A1 and eEF1A2 were more elevated (p=0,028) in CLL lymphocytes compared to control. Moreover, eEF1A1 but not eEF1A2 protein levels were higher (p=0,0042) in patient which died during the study compared to those surviving. Finally, eEF1A1 targeting by either GT75 or siA1 resulted in MEC-1 viability down regulation (p=0,04) mostly due to autophagy stimulation. In vivo, GT75 or siA1 resulted in tumor growth down-regulation (p=0.014) and extension of animal survival (p=0.014), demonstrating the functional role of eEF1A1 in CLL. Conclusions. The increase of eEF1A1/eEF1A2 protein in lymphocytes of CLL patient cells suggests a role as possible novel CLL markers. The increase of eEF1A1 protein in dead vs surviving patients may confer to eEF1A1 also the role of a novel prognostic marker. This, together with the involvement of eEF1A1 in MEC-1 survival in vitro and in vivo, opens the possibility to consider eEF1A1 also as a novel therapeutic target in CLL.