RET and breast cancer: Studies have identified 5 AP-2γ binding sites in the RET promoter which mediate AP-2γ induced RET expression.[46] Interestingly, CpG island methylation of the RET promoter and decreased RET expression have been linked to poor prognosis in tumor-node-metastasis (TNM) stage II colorectal cancer patients,[47,48] suggesting that epigenetic modification of CpG islands may also influence RET expression in breast cancer.