Expression profile of telomere- associated genes in non- small cell lung cancer (NSCLC)

Author(s)

Camila Baldin Storti

• Document type: Master's Dissertation
• Press: Botucatu. 2018-03-29.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
• Defense date: 2018-03-09
• Advisor: Maria Isabel Nogueira Cano; Patrícia Pintor dos Reis

Abstract

According to the World Health Organization, lung cancer has a high mortality rate associated with >1.6 million deaths per year, being Non-small cell lung cancer (NSCLC) the most frequent type (~ 85%) of lung carcinoma. Lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) are the two major histological subtypes of NSCLC. Research efforts have been made to identify molecular biomarkers useful as therapeutic targets in NSCLC and telomere have been considered very promising targets for anticancer therapies due to their crucial role in genome integrity maintenance and stability. Human telomeres consist of repetitive G-rich DNA associated with proteins of the shelterin complex, maintained by the action of telomerase. Recent studies showed that expression of TERT (telomerase reverse transcriptase component) and of some of the shelterin components are altered in lung cancer. However, the mechanisms of telomere deregulation associated with NSCLC development and progression have not been elucidated. Therefore, our aim was to study expression changes affecting telomere-associated genes and ncRNAs associated with telomere regulation and maintenance in NSCLC. Such alterations may represent novel biomarkers associated with NSCLC development and progression. For this purpose, expression analyzes of 50 telomere-associated genes were performed in samples of tumor tissue and normal lung tissue, adjacent to the tumor, from patients with NSCLC. The following techniques were used: 1) RT-qPCR for analysis of expression in samples obtained from 28 patients who underwent surgical treatment at Botucatu Clinical Hospital; 2) Transcriptome analysis using RNA-Seq data from samples obtained from 27 patients treated at AC Camargo Hospital 3) Transcriptome analysis using RNA-Seq data, available in the The Cancer Genome Atlas database (TCGA) and obtained from samples of 85 patients. In addition, the differences between the expression profile of the telomere-associated genes in LUSC and LUAD subtype samples were analyzed. The results revealed that many genes involved in telomeres maintenance are significantly, ≤ 0.05, deregulated in the NSCLC tumors. Genes enconding TERT, RAD51, DNMT3B, DKC1 and BRCA2 were overexpressed in NSCLC tumor cells compared to the normal lung tissue. SUV39H1, RUVBL1 and DNMT3A genes were overexpressed only in LUSC subtype samples. The ncRNAs TERC and TERRA also showed increased expression in NSCLC samples, with emphasis to the high expression level of TERC associated with the LUSC subtype In addition, telomere restriction fragment (TRF) was estimated for tumor tissue (n=11) and normal lung tissue (n=4) samples obtained from patients with NSCLC. TRFs from leukocytes obtained from patients with NSCLC (n= 14) were also compared with TRFs obtained from healthy donors (n = 13). The results showed that telomeres of leukocytes obtained from NSCLC patients were shorter than those of healthy donors (p≤0.05) and it decreases according to patient's age (Spearman's correlation, p= 0.00 and r= -0,644). However, no significant difference was found between the TRF obtained from tumor and normal lung tissues of patients with NSCLC, as no correlation was found when comparing TRFs and the age of these individuals, probably due to the low sample size. The results suggest that genes encoding proteins and ncRNAs involved in the maintenance of telomeres may be involved in the oncogenesis of NSCLC, especially the LUSC subtype, since the increased expression of some genes, SUV39H1, RUVBL1, DNMT3A and TERC, are exclusively associated with tumor samples of this subtype. (AU)

• FAPESP's process: 16/06936-6 - Genes and telomeric proteins as biomarkers in non-small cell lung cancer (NSCLC)
• Grantee: Camila Baldin Storti
• Support Opportunities: Scholarships in Brazil - Master