TERT promoter regulating melittin expression induces apoptosis and G(0)/G(1) cell cycle arrest in esophageal carcinoma cells

Esophageal squamous cell carcinoma accounts for a large proportion of cancer-associated mortalities in both men and women. Melittin is the major active component of bee venom, which has been reported to possess anti-inflammatory, antibacterial and anti-cancer properties. The aim of the present study was to construct a tumor targeted recombinant plasmid [pc-telomerase reverse transcriptase (TERT)-melittin] containing a human TERT promoter followed by a melittin coding sequence and to explore the effects of this plasmid in esophageal cell carcinoma and investigate preliminarily the underlying mechanisms of this effect. TE1 cells were transfected with pcTERT-melittin and the resulting apoptosis was subsequently examined. The viability of TE1 cells transfected with pcTERT-melittin was measured using a Cell Counting Kit-8 assay, which indicated inhibited proliferation. The disruption of mitochondrial membranes and the concomitant production of reactive oxygen species demonstrated an inducible apoptotic effect of melittin in TE1 cells. Apoptotic cells were also counted using an Annexin V-FITC and PI double-staining assay. The upregulation of cleaved caspase-9, cleaved caspase-3, Bax and poly(ADP-ribose) polymerase 1 in pcTERT-melittin transfected TE1 cells, suggested that pcTERT-melittin-induced apoptosis was associated with the mitochondrial pathway. TE1 cells were also arrested in the G(0)/G(1) phase when transfected with pcTERT-melittin, followed by the decline of CDK4, CDK6 and cyclin D1 expression levels. As cell invasion and metastasis are common in patients with esophageal cancer, a cell migration assay was conducted and it was found that pcTERT-melittin transfection reduced the migratory and invasive abilities of TE1 cells. The findings of the present study demonstrated that pcTERT-melittin may induce apoptosis of esophageal carcinoma cells and inhibit tumor metastasis.