X chromosome inactivation pattern in BRCA gene mutation carriers

Area of Science:

• Genetics
• Oncology
• Epigenetics

Background:

• Preferential X chromosome inactivation (XCI) has been linked to BRCA gene status and cancer risk.
• BRCA1 and BRCA2 mutations significantly increase the risk of breast and ovarian cancers.

Purpose of the Study:

• To evaluate XCI patterns in BRCA mutation carriers versus non-carriers.
• To investigate associations between preferential XCI and age, BRCA gene type, cancer development, and chemotherapy.

Main Methods:

• Human androgen receptor (HUMARA) assay and pyrosequencing were used to analyze XCI.
• Logistic regression analysis compared XCI patterns between 437 BRCA carriers and 445 age-matched controls.
• Univariate and multivariate analyses examined associations between preferential XCI and clinical variables.

Main Results:

• Preferential XCI (⩾90:10) showed no significant association with BRCA mutation carrier status or cancer status in univariate analyses.
• Chemotherapy and age were significantly associated with preferential XCI in univariate analyses.
• In multivariate analysis, only age remained significant (OR, 1.056; 95% CI, 1.016-1.096), indicating increased XCI frequency with aging.

Conclusions:

• XCI analysis is not currently useful for identifying BRCA mutation carriers or assessing cancer risk.
• The association of increasing preferential XCI with age and chemotherapy warrants further investigation in other female cancer patient groups to identify potential X-linked loci involved in cell survival.