GPT2 and breast carcinoma: In order to investigate the effect of GPT2 on breast cancer metastasis, we first introduced Gpt2 gene knockout C57BL/6 mice, and then mated with MMTV-PyMT mice to generate MMTV-PyMT; Gpt2+/- and MMTV-PyMT; Gpt2-/- mice (Figure 5C).