Hypermethylation of the regulatory regions of genes is an important and prominent feature of cancer biology. Recently, we identified DNA-methylation markers associated with the risk of recurrence in node-negative, hormone receptor-positive breast cancer after adjuvant tamoxifen monotherapy. DNA-methylation of PITX2 was found to be the most informative marker. PITX2 encodes a homeobox containing bicoid-related transcription factor involved in pituitary specific gene regulation, left and right patterning and mutations in the gene cause Axenfeld-Rieger syndrome. In the current study, we have investigated the prognostic value of PITX2 DNA-methylation. For this purpose, PITX2 methylation was measured in tumor samples obtained from 415 node-negative, hormone receptor-positive breast cancer patients who did not receive any adjuvant systemic treatment and who were followed for an average of 93 months. A real-time PCR based assay was used that allows simultaneous quantitative measurement of unmethylated and methylated copies of the gene in genomic DNA. DNA-methylation of PITX2 was significantly associated with the risk of disease recurrence in this cohort of patients. In an univariate Cox model that was built, DNA-methylation of PITX2 significantly predicted patients who will eventually develop distant metastases (P <0.0001). PITX2 methylation distinguished two groups with a large difference in metastasis-free survival. In the group of patients with low levels of PITX2 methylation, 86% were still metastasis-free at 10 years, compared to 67% in the group with high levels of PITX2 methylation. In a multivariate analysis, DNA-methylation of PITX2 contributed significant information to conventional prognostic factors such as age, menopausal status, grade, and tumor size (P < 0.0001). We conclude that DNA-methylation of PITX2 is a strong prognostic marker in untreated hormone receptor-positive node-negative breast cancer patients.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]