Lynch Syndrome-Associated Breast Cancers Do Not Overexpress Chromosome 11 Encoded Mucins

摘要

Mismatch repair (MMR) deficient breast cancers may be identified in Lynch syndrome mutation carriers, and have clinicopathological features in common with MMR deficient colorectal and endometrial cancers such as tumour infiltrating lymphocytes and poor differentiation. MMR deficient colorectal cancers frequently show mucinous differentiation associated with upregulation of chromosome 11 mucins. The aim of this study was to compare the protein expression of these mucins in MMR deficient and MMR proficient breast cancers.Cases of breast cancer (n = 100) were identified from families where 1) both breast and colon cancer co-occurred, 2) families met either modified Amsterdam criteria, or had at least one early onset (<50 years) colorectal cancer, and 3) biospecimens were available for MMR protein expression, microsatellite instability (MSI) status, and MMR gene mutation testing. Tumour sections were stained for the epithelial mucins MUC2, MUC5AC, MUC5B, and MUC6, and the homeobox protein CDX2, a regulator of MUC2 expression.Sixteen MMR deficient Lynch syndrome breast cancers and 84 non-Lynch breast cancers were assessed for altered mucin expression. No significant difference in the expression of MUC2, MUC5AC or MUC6 was observed between the MMR deficient and MMR proficient breast cancers, however, there was a trend for MMR deficient tumours to express high levels of MUC5B less frequently (p = 0.07, OR = 0.2 [0.0 – 1.0]. Co-expression of two or more gel-forming mucins was common. Ectopic expression of CDX2 was associated with expression of MUC2 (p = 0.035, OR = 8.7 [1.3 – 58.4]).MMR deficient breast cancers do not show differential expression of the mucins genes on chromosome 11 when compared to MMR proficient breast cancers, contrasting with MMR deficient colorectal and endometrial cancers which frequently have increased mucin protein expression when compared to their MMR proficient counterparts. In addition, ectopic CDX2 expression is positively associated with de novo MUC2 expression.