Fig. 7: SAM promotes gastric cancer cell proliferation at low concentrations, and miR-22 overexpression and MTHFD2, MTHFR knockdown rescues low SAM concentration-induced proliferation in GC cells.

a PCA score plots derived from 10 paired clinical sample metabolomics assay data (positive ion mode, QC is short for quality control). b Volcano plot showing the metabolite variation trend in GC compared with normal samples. c SAM quantitative results for all samples. d SAM peak area for the paired clinical samples. e MTT (top) and colony formation (bottom) assays were performed to examine AGS and MKN45 cell proliferation after treatment with different concentrations of SAM. f P16, PTEN, P21, and RASSF1A mRNA levels in AGS and MKN45 cells treated with two concentrations of SAM (0.04 mM and 0.008 mM). g MTT assays was performed to measure the growth of MKN45 cells after treatment with low concentrations of SAM and miR-22, MTHFD2 siRNA or MTHFR siRNA transfection. h colony formation assays were performed to measure the growth of MKN45 cells after treatment with low concentrations of SAM and miR-22, MTHFD2 siRNA or MTHFR siRNA transfection. i PTEN, P21, and P16 protein expression was analyzed after treatment with low concentrations of SAM and miR-22. j Proposed model for the effect of MeCP2 on miR-22 transcription, and miR-22 suppressed GC cell proliferation by inducing an endogenous SAM deficit. The results are shown as mean±SD. n = 3, *p < 0.05, **p < 0.01, Student’s t test.