Thermal stress involved in TRPV2 promotes tumorigenesis through the pathway of PI3K/Akt/mTOR in esophageal squamous cell carcinoma

Abstract

BackgroundEsophageal squamous cell carcinoma (ESCC) is a leading cause of cancer death worldwide. Although the exposure of esophageal mucosa to heat stimuli has long been recognized as an important risk for the initiation and development of ESCC, its underlying mechanisms remain uncharacterized. MethodsWestern blotting and immunofluorescence were used to detect the expression and localization of transient receptor potential vanilloid receptor 2 (TRPV2) in the ESCC cells. The cancerous behaviors of the ESCC cells were evaluated by a single-cell culturing assay, a wound healing assay, a 3D culturing assay and a tube formation assay respectively. In vivo tumorigenicity and metastasis of the ESCC cells were examined via xenograft nude mouse models. Western blotting and IHC were performed to determine the expression profiles of TRPV2 in the ESCC patient tissues. TRPV2 knocked-out ESCC cell line was established using CRISPR-Cas9 gene editing technique.ResultsHere, we found that the expression of TRPV2, one of the thermally sensitive TRP family members, was upregulated in both ESCC cells and clinical samples. We further showed that activation of TRPV2 by recurrent acute thermal stress (54°C, a temperature unexpectedly much lower than those in many dietary modalities) or O1821 (20 μM), a TRPV2 agonist, promoted cancerous behaviors in ESCC cells. The proangiogenic capacity of the heat-challenged ESCC cells was also found to be enhanced profoundly in the tube formation assay; both tumor formation and metastasis that originated from the cells were substantially promoted in nude mouse models upon the activation of TRPV2. These effects were inhibited significantly by tranilast (120 μM), a TRPV2 inhibitor, and abolished by TRPV2 knock-out using CRISPR-Cas9 gene editing. Conversely, overexpression of TRPV2 by transfection of TRPV2 DNA into NE2 cells, could switch the cells to tumorigenesis upon activation of TRPV2. Mechanistically, the driving role of TRPV2 in the progression of ESCC is mainly regulated by the PI3K/Akt/mTOR signaling pathway. Application of a pan-PI3K/mTOR inhibitor and/or a PTEN activator resulted in markedly reduced ESCC cell proliferation. ConclusionsOur study first proved that TRPV2 plays an important role in the tumorigenesis of ESCC upon thermal stress. We revealed that TRPV2-PI3K/Akt/mTOR is a novel and promising target for the prevention and treatment of ESCC.