Increased expression of TERT associated to promoter region mutations in patients with mantle cell lymphomas

RAQUEL M. ALVES-PAIVA; JULIETA PANERO; ALEJANDRO ROISMAN; BARBARA A. SANTANA-LEMOS; CARMEN STANGANELLI; IRMA SLAVUTSKY; RODRIGO CALADO

San Pablo

Congreso; Congreso Brasileiro de Hematología, Hemoterapia e Terapia Celular 2015; 2015

Sociedad Brasileira de Hematología

Lymphoid malignancies constitute a heterogeneous group of lymphoproliferative disorders with specific clinical, morphological, immunophenotypic, and genetic features (Swerdlow et al, 2008). Mantle celllymphoma (MCL)is an aggressive lymphoid neoplasm associated with poor prognosis, geneticallycharacterized by the translocation t(11;14) and cyclin D1 overexpression(Sander et al, 2011). Telomeres areribonucleoprotein structures at the end of linear chromosomes that serve toprotect chromosomes from end-to-end fusion and recombination (Blackburn). Short telomeres promote chromosomal instability by aberrant chromosomal segregationduring cell division, chromosomal translocation, eventually causing aneuploidy (Calado,Young 2008; Paiva, Calado 2014). The shelterin complex (TRF1, TRF2, TIN2, RAP1,TPP1, and POT1) protects telomeres against degradation and fusion, andregulates telomere length (TL) by modulating telomerase activity (de Lange etal, 2005). Telomerase is a reverse transcriptase enzyme composed by a catalyticsubunit (TERT), a genomic subunit (TERC) and stabilzing proteins (such as DKC1). Telomerase catalytically adds TTAGGG hexameric nucleotide repeats to the 3-hydroxyl end of the telomeric leading strand, using a specific sequencein the RNA component as the template. Normal somatic cells express nodetectable levels of TERT, however 90% of human tumoral cells over express this gene. Recently, somatic mutations of TERT promoter region (TERTp) have been described in different solid tumors. Nonetheless, there is no knowledge of these mutations on lymphoids neoplasias. Thiswork aimed to evaluate the prevalecy of mutations on TERTp in patients with MCL and correlate the results with expression of genes that are associated totelomeres (TRF1, TRF2, TIN2, RAP1,TPP1, POT1, TERT, DKC1), TL and prognostic factors such as SOX11 expression and IGHV (immunoglobulin heavy chain variable region) mutational status. Twenty four MCL patients samples were analyzed (7 females; median age: 66.4 years old, range: 49-88 years). Quantitative PCR was performed to TL measurement and gene expression analysis and Sanger sequencing was performed for TERT promoter analysis. The study was approved by Local Ethical Commitee. The promoter region probed in this study contained the two commonly described mutations (C228T and C250T) located 124 and 146 bp upstream of the ATG start site, respectively. Eight cases (33,3%) presented TERTp mutations: six heterozygous (C228T) and two homozygous (C228T and C250T). Mutated patients evidenced overexpression of TERT (2.63±0.68) compared to patients with no mutations (0.94±0.29) (p=0.004), and an increased expression of genes associated to telomeres was observed (TRF1, TRF2, POT1 y DKC1). Furthermore, TERTp mutated patients presented overexpression of SOX11 (0.338±0.2) and a minimum mutational status of IGHV, both considered as bad prognostic in MCL. No significant association between TERTp mutations and TL was observed. In addition, we did not find association between TL and IGHV mutational status. In conclusion, we describe for the first time that acquired TERTp mutations were associated with higher TERT transcription levels in hematologic malignancies and higher shelterin expression in cancer. The increased TERT expression is associated to molecular parameters matching to more aggressive lymphoma.