Expression of TERT (AS) alternative splicing variants and TERF2 in osteosarcoma

Background: Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents. Mechanisms of telomere maintenance (TMM) are central features of the tumor cells to maintaining their proliferative capacity. Aim: In this study, we investigated the expression of TERT (telomerase reverse transcriptase) alternative splicing (AS) variants, TERC (telomerase RNA component), TERF1 (telomeric repeat binding factor 1) and TERF2 (telomeric repeat binding factor 2) and quantified telomerase enzyme activity in samples of OS, correlating with clinical and pathological aspects. Methods: A total of 70 fragments of OS tumor samples and 10 normal bone samples (NB) were used for the analysis of gene expression by nested RT-PCR (reverse transcriptase-polymerase chain reaction) and qPCR (quantitative real time PCR). For the quantification of telomerase by TRAP assay we used 20 OS samples and two NB samples. Results: We observed the expression of TERT in 44% of the tumors and full length (FL) isoform in only 4%. TERF2 expression levels were higher in PRECH (pre-chemotherapy) samples than in POSTCH (post-chemotherapy) (p= 0.0468). POSTCH samples from patients without relapse showed lower levels of expression of TERF2 (p= 0.0167). Conclusions: Despite the high expression of TERC , the low prevalence of isoform FL suggested that telomerase may not be the main TMM in OS. Recent studies have correlated TERF2 overexpression to different mechanisms of resistance to chemotherapeutic drugs. Low levels of TERF2 gene expression, in POSTCH samples from patients with no relapse of disease suggest a correlation with a better response to treatment.