The SH2 domain is essential for SHF binding and inhibition of STAT3 dimerization. A) A schematic diagram of SHF and its deletion mutants. B) IP assay showing a SH2 deletion mutant (dSH2) fails to bind STAT3. 293T cells were transfected with the indicated vectors, followed by IP using Flag antibody. C) IP assay indicating the SH2 construct (SH2) binds STAT3. D) The effect of SH2 deletion mutant on STAT3 dimerization was examined in 293T cells transfected with the indicated vectors using IP assay. E) IP assay detecting the effect of the SH2 construct on STAT3 dimerization. The relative quantification of STAT3/DNMT1 interaction was listed. F) Luciferase assay of STAT3 transcriptional activity in the indicated cells (n = 8, two‐tailed Student's t‐test, **p < 0.01). G) IP assay detecting the effect of the SH2 construct on the interaction between STAT3 and DNMT1 in 293T cells transfected with the indicated vectors. The relative quantification of STAT3/DNMT1 interaction was listed. H) The growth curves of Mock and SH2 expressing xenograft tumors (n = 10, Student's t‐test, **p < 0.01). I) Images of excised tumors (upper) and comparison of tumors sizes (lower) at the final time point (n = 10, Student's t‐test, **p < 0.01). J) Images of EdU labeling of tumor sections (left) and statistical analysis of EdU positive cells (n = 10, Student's t‐test, *p < 0.05 **p < 0.01). K) qRT‐PCR assay measuring the expression of indicated STAT3‐targeted genes in derived tumors (n = 6, Student's t test, **p < 0.01). L) qRT‐PCR assay measuring the expression of indicted methylated genes in derived tumors (n = 6, Student's t test, **p < 0.01).