X chromosome inactivation pattern in female patients with breast cancer

Excerpt

In females one of the two X chromosomes is inactivated in early embryonic life, thus making females mosaics for two cell lines. Most females have a 50:50 distribution of the two cell lines. A deviation from this distribution is called a skewed X inactivation. Skewed X inactivation may be a result of a chance event, due to genetic factors or a selection mechanism. Older females have an increased frequency of skewed X inactivation in peripheral blood cells. An association between skewed X inactivation and BRCA1 mutation in germline DNA of patients with ovarian cancer was recently reported (Buller et al 1999). A significant increase in skewed X inactivation pattern was also found in patients with invasive cancer compared to patients with borderline cancer and healthy controls, indicating that skewed X inactivation is a predisposing factor for the development of invasive ovarian cancer. …