MFN2 is down‐regulated in human ccRCC and associated with favorable prognosis. (A) Heat map showing differentially expressed genes between normal and tumor tissues in TCGA‐KIRC cohort. (B) Strategy to identify candidate genes involved in tumorigenesis and metastasis of ccRCC. (C) AUC evaluation of the prognostic value of identified candidate genes based on TCGA‐KIRC database. (D) MFN2 mRNA expression levels in normal and tumor tissues from TCGA‐KIRC database. (E) Representative images of MFN2 protein levels in nine pairs of human ccRCC tumor tissues and adjacent normal tissues. Tubulin was used as a loading control. The statistical analysis is shown in the right panel. (F) Representative images of IHC staining (left panels) and IF staining (right panels) for MFN2 (green) and DAPI (blue) in human ccRCC tumor and normal tissues. (G) Quantification of MFN2 protein levels in human ccRCC tumor and normal tissues from IHC staining of Figure 1F (n = 10). (H‐J) MFN2 mRNA expression levels in different grades and stages in TCGA‐KIRC database: clinical stage (H), tumor stage (I) and metastasis status (J) according to the 8th edition of AJCC TNM Staging. (K) Western blotting image (left panel) and statistical analysis (right panel) of MFN2 protein expression detected in immortalized renal epithelial cell line HK‐2 and ccRCC cell lines (786‐O, A‐498, Caki‐1). Tubulin was used as a loading control. (L) Relative MFN2 mRNA expression of HK‐2 and ccRCC cells. Tubulin was used as a loading control. (M) OS of ccRCC patients with high (n = 134) or low (n = 397) expression of MFN2 in TCGA‐KIRC cohort. (N‐O) OS (N) and DFS (O) of ccRCC patients with high (n = 65) or low (n = 85) expression of MFN2 in SYSUCC cohort, determined by MFN2 IHC staining, Data are presented as means ± SD. *P < 0.05, ** P < 0.01, *** P < 0.001, by Student's t test (D, E, G, H, I, J, K) or log‐rank test (M, N, O).
Abbreviations: TCGA‐KIRC, the Cancer Genome Atlas kidney renal clear cell carcinoma; MFN2, mitofusin‐2; AUC, area under curve; N, normal; T, tumor; Pri, primary tumor; Met, metastatic tumor; M, metastasis; TPM, transcripts Per Kilobase of exon model per Million mapped reads; IHC, immunohistochemistry; IF, immunofluorescence; DAPI, 4,6‐diamidino‐2‐phenylindole; Relat., relative; SYSUCC, Sun Yat‐sen University Cancer Center; OS, overall survival; DFS, disease‐free survival.