A pivotal study in human prostate cancer tissues and cell lines to measure the expression levels of eukaryotic Elongation Factor 1A proteins and the effect of a nucleic acid-based GT75 aptamer

Background: Two major isoforms of the eukaryotic Elongation Factor 1A are recognised: the eEF1A1, ubiquitously expressed, and the eEF1A2 presents in adult heart and skeletal muscle, in the nervous system, and in some other specialized cells. Both proteins are implicated in the development and progression of human cancers with a different role. In prostate cancer, overexpression of eEF1A2 has been proposed to be involved in the onset of the tumour and it was related to a worse outcome. However, the expression level of both proteins in prostate cancer tissue is not well known. We explore the expression level of the two proteins and mRNAs in formalin-fixed paraffin-embedded tissues derived from prostate cancer patients. Moreover, we investigated the effect of the nucleic acid-based GT75 aptamer, targeting eEF1A protein, in human prostate cancer cell lines. Materials and methods: Formalin-fixed, paraffin-embedded samples of hyperplasia (n = 10), of Gleason 4–6 (n = 10) and of Gleason 7–8 (n = 10) were analysed. Protein level of eEF1A1 and eEF1A2 was determined by an IHC method previously described; the mRNA levels were quantified by ddPCR with probes. The tumorigenic PC-3 and the non-tumorigenic PZHPV-7 cell lines were transfected with the GT75 aptamer or CT75 control, the cell growth was evaluated by MTS assay; the expression level of the proteins in cell culture was determined by an immunofluorescent assay. The results were statistically examined by Anova, Mann-Withney and Fisher tests. Results: The expression level of the proteins in tissues was a score 0, 1, 2, 3. With respect to Gleason 4–6, eEF1A1 protein was found to increase in samples with Gleason 7–8 (p = 0.001); whereas a decrease in eEF1A2 levels were found in cancer samples with respect to hyperplasia (Gleason 4–6, p < 0.001; Gleason 7–8 p = 0.005). No significant difference among the groups was found in mRNA levels for both proteins. In cancer PC-3 cells, the transfection of the GT75 aptamer led to 40% of cell growth inhibition with respect to CT75 oligonucleotide control. In agreement, a 60% decrease in eEF1A1 protein level was measured, but only a 20% reduction in eEF1A2. Interestingly, no effects were found in the non-tumorigenic PZHPV-7 cells. Conclusion: eEF1A1 protein could be an interesting molecular target for the control of cell proliferation in more aggressive prostate cancer forms.