Tumor necrosis factor-α induced protein 8 (TNFAIP8/TIPE) family is differentially expressed in oral cancer and regulates tumorigenesis through Akt/mTOR/STAT3 signaling cascade

Abstract

Background: Highest incidence of oral cancer is reported in India with reduced survival rate in the advanced stages due to lack of effective biomarkers. Therefore, it is essential to develop novel biomarkers for the better management of this disease. In the current study, TNFAIP8/TIPE protein family comprising of four proteins is explored for its role in oral cancer.

Methods: IHC analysis of oral cancer TMA and Western blot analysis of tobacco treated oral cancer cells were performed to determine the differential expression of TIPE proteins in oral cancer. Further, CRISPR/Cas9-mediated gene editing was done to generate TIPE proteins' knockouts and MTT, colony formation, wound healing, cell cycle and Western blot analysis were performed to determine the effect of gene knockouts on various cancer hallmarks and the associated molecular targets of TIPE proteins.

Results and discussion: IHC results revealed that expression of TIPE, TIPE2 and TIPE3 were upregulated and TIPE1 was downregulated in oral cancer tissues compared to normal tissues. Similar results were observed upon treating oral cancer cells with tobacco carcinogens. Furthermore, knockout of TIPE or TIPE2 or TIPE3 significantly reduced the survival, proliferation, colony formation and migration of oral cancer cells whereas knockout of TIPE1 had an opposite effect. Further, TIPE, TIPE2 and TIPE3 knockout-mediated inhibition of proliferation was associated with inhibition of cell cycle progression at S or G2/M phases, and downregulation of proteins involved in cancer progression. We found that TIPE, TIPE1 and TIPE2 proteins regulate oral cancer progression through modulation of Akt/mTOR signaling cascade, whereas TIPE3 acts through an Akt-independent mTOR/STAT3 pathway.

Conclusion: Collectively, the TIPE proteins were proved to play significant roles in the progression of oral cancer thus warranting research and clinic attention for their therapeutic and prognostic values and raising the importance of specific targeting of TIPE proteins in cancer treatment.

Keywords: Akt; Oral cancer; TIPE; TNFAIP8; Tobacco; mTOR.