Exploring genetic and epigenetic alterations in hTERT gene in colorectal cancer

Introduction: Colorectal cancer (CRC) is a heterogeneous and multifactorial malignancy driven by a series of genetic and epigenetic alterations. In this field, telomere/telomerase dysfunction contributes to CRC carcinogenesis by impairing genomic stability and cellular replication. Objective: This study aimed to evaluate genetic and epigenetic alterations in CRC by examining mutation rates in the human telomerase reverse transcriptase (hTERT) promoter region, relative telomere length (RTL), hTERT gene expression, and DNA methylation in the TERT hypermethylated oncological region (THOR). Methods: A total of 45 CRC and 34 adjacent normal tissue samples from Moroccan patients were analyzed using molecular approaches, such as Sanger sequencing, quantitative PCR (qPCR), reverse transcription qPCR (RT-qPCR), and methylation-specific PCR (MSP). Results: No mutations in the hTERT promoter region were identified. However, hypermethylation in the THOR region was reported in 82.2% of CRC samples and 79.4% of adjacent normal tissues. High hTERT expression was detected in 50% of CRC patients. In addition, telomere length was significantly shorter (p=0.002) in cancerous tissues (1.41 [1.36 – 1.43]) compared to normal mucosa (1.559 [1.46 – 1.63]), with an RTL ratio less than 1 (0.90 [0.86 – 0.95]). No significant differences were found between clinicopathological features and hTERT expression, THOR methylation, or RTL, except for a significant correlation between THOR hypermethylation and smaller tumor size (p=0.017) and between THOR methylation and RTL in CRC tissues (p=0.034). Conclusion: These results suggest that telomere lengthening is crucial for CRC initiation and progression, and cancer cells tend to shorten telomeres to maintain the chromosomal instability (CIN) required for tumor progression. Further research is needed to elucidate the mechanisms underlying telomere shortening in CRC and understand the role of telomerase/telomere complex in CRC initiation and progression, which could provide new diagnostic, prognostic, and therapeutic targets.