Hypermethylation at DOK7 may serve as a biomarker for tamoxifen resistance among breast cancer patients, a team from the Iran University of Medical Sciences in Tehran reports in the Journal of Human Genetics. Differences in DOK7 expression levels, the researchers note, have recently been tied to differences in cancer prognosis and its repression has also been linked to cancer cell proliferation. They compared DOK7 CpG methylation levels in blood leukocytes of 31 ER+, tamoxifen-resistant disease cancer patients to samples from 29 tamoxifen-sensitive breast cancer patients. Through this, they found much higher levels of methylation at the DOK7 CpG locus, more than 85 percent, in tamoxifen-resistant breast cancer patients, as compared to a lower, 21.9 percent, methylation level among tamoxifen-sensitive patients and moderate, 57 percent, methylation in the normal control group. "There is a significant difference in the methylation ratio of DOK7 between tamoxifen resistant and tamoxifen sensitive groups that may be useful in the early diagnosis of tamoxifen resistance in BC cases and cancer recurrence prevention," the research team writes.