Telomerase reverse transcriptase interference synergistically promotes tumor necrosis factor-related apoptosis-inducing ligand-induced oral squamous cell carcinoma apoptosis and suppresses proliferation in vitro and in vivo

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is known to induce cell apoptosis in many types of cancer cells. However, some malignant cells still exhibit anti-apoptosis features induced by TRAIL; thus the underlying mechanisms that regulate sensitivity and resistance of tumor cells to TRAIL-induced apoptosis remain unclear. Human telomerase reverse transcriptase (hTERT) is overexpressed in most types of human tumors and is mostly inactive in somatic cells. The present study aimed to investigate the endogenous effects and mechanisms of hTERT inhibition and TRAIL overexpression on TRAIL-induced apoptosis of human oral squamous cell carcinoma (OSCC) cells. The effects of adeno-associated virus (AAV)-mediated TRAIL and hTERT gene silencing by RNA interference were investigated on the proliferation and apoptosis of human OSCC cells in vitro and in vivo. The present results suggest that knockdown of hTERT expression accelerated TRAIL-resistant OSCC cells to TRAIL-induced apoptosis and impaired OSCC cell proliferation. In addition, this process is accompanied by the upregulation of caspase-3, caspase-8 and caspase-9, and downregulation of B cell lymphoma-2. Additionally, the possible mechanisms underlying the association between TRAIL expression and hTERT silencing were explored. The results demonstrated that TRAIL expression levels were elevated when the hTERT gene was silenced, and notable anti-tumor effects were observed when TRAIL upregulation and hTERT gene silencing were carried out simultaneously. The present findings provide experimental evidence for the combined use of TRAIL and hTERT as a possible gene therapy strategy in oral cancer.