Subsequently, some studies have reported that HMGN2 is essential for prolactin-induced CISH (cytokine-inducible SH2 containing protein) expression by promoting histone H1 loss and STAT5 (signal transducer and activator of transcription 5) binding in breast cancer.13, 14, 15 In gastric cancer, HMGN2 is significantly associated with recurrence-free survival. This evidence concerns the gene STAT5A and breast cancer.