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Theranostics 2020; 10(26):12044-12059. doi:10.7150/thno.47901 This issue Cite

Research Paper

ITGB2-mediated metabolic switch in CAFs promotes OSCC proliferation by oxidation of NADH in mitochondrial oxidative phosphorylation system

Xiaoxin Zhang^1#, Yingchun Dong^2#, Mengxiang Zhao³, Liang Ding¹, Xihu Yang³, Yue Jing¹, Yuxian Song¹, Sheng Chen⁴, Qingang Hu^1,3✉, Yanhong Ni^1✉

1. Central Laboratory, Nanjing Stomatological Hospital, Medical School of Nanjing University, 30 Zhongyang Road, Nanjing 210008, China.
2. Department of Anesthesiology, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing 210008, China.
3. Department of Oral & Maxillofacial Surgery Nanjing Stomatological Hospital, Medical School of Nanjing University, 30 Zhongyang Road, Nanjing 210008, China.
4. Department of Oral Pathology, Nanjing Stomatological hospital, Medical School of Nanjing University, Nanjing, Jiangsu 210008, China.
#These authors contributed equally to this paper.

✉ Corresponding authors: E-mail: niyanhong12com (Y.N); qghuedu.cn (Q.H).

Abstract

Objectives: Integrins, the coordinator of extracellular and intracellular signaling, are often found to be aberrant in tumors and can reshape the tumor microenvironment. Although previous studies showed that integrin beta 2 (ITGB2) is important for host defense, its expression profile and role in tumors, especially in cancer associated fibroblasts (CAFs) are still unknown.

Methods: Immunofluorescence stain and fluorescence activated cell sorting were used to analyze the ITGB2 expression profile in oral squamous cell carcinoma (OSCC). RT-PCR and western blot were used to compare ITGB2 expression in normal fibroblasts (NFs) and cancer associated fibroblasts (CAFs). Clinical data and function-based experiments were used to investigate the promoting tumor growth ability of ITGB2 expressing CAFs. Enhanced glycolysis activity was identified by using bioinformatics analyses and GC/MS assays. MCT1 knockdown OSCC cell lines were constructed to explore the pro-proliferative mechanisms of ITGB2 expressing CAFs in multiple in vitro and in vivo assays.

Results: We found that CAFs exhibited significantly higher ITGB2 expression than the matched NFs. In addition, higher ITGB2 expression in CAFs was correlated with higher TNM stages and more Ki67+ tumor cells, indicating its ability to promote OSCC proliferation. Further, co-culture assay demonstrated that ITGB2-mediated lactate release in CAFs promoted OSCC cell proliferation. Mechanically, ITGB2 regulated PI3K/AKT/mTOR pathways to enhance glycolysis activity in CAFs. Accordingly, lactate derived from ITGB2-expressing CAFs was absorbed and metabolized in OSCC to generate NADH, which was then oxidized in the mitochondrial oxidative phosphorylation system (OXPHOS) to produce ATP. Notably, inhibiting the OXPHOS system with metformin delayed the proliferative capacity of OSCC cells cultured in the ITGB2-expressing CAFs medium.

Conclusions: Our study uncovered the ITGB2^high pro-tumoral CAFs that activated the PI3K/AKT/mTOR axis to promote tumor proliferation in OSCC by NADH oxidation in the mitochondrial oxidative phosphorylation system.

Keywords: oral squamous cell carcinoma, cancer associated fibroblasts, ITGB2, lactate, NADH, oxidative phosphorylation system

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