Lynch syndrome-associated extracolonic tumors are rare in two extended families with the same EPCAM deletion

Abstract

Objectives: The Lynch syndrome (LS) is an inherited cancer syndrome showing a preponderance of colorectal cancer (CRC) in context with endometrial cancer and several other extracolonic cancers, which is due to pathogenic mutations in the mismatch repair (MMR) genes, MLH1, MSH2, MSH6, and PMS2. Some families were found to show a LS phenotype without an identified MMR mutation, although there was microsatellite instability and absence of MSH2 expression by immunohistochemistry. Studies of a subset of these families found a deletion at the 3' end of the epithelial cell adhesion molecule (EPCAM) gene, causing transcription read-through resulting in silencing of MSH2 through hypermethylation of its promoter. The tumor spectrum of such families appears to differ from classical LS.

Methods: Our study of two large families (USA Family R and Dutch Family A) with an EPCAM deletion was carried out using each institution's standard family study protocol. DNA was extracted from peripheral blood and EPCAM deletion analysis was performed.

Results: Both families were found to harbor the same deletion at the 3' end of EPCAM. Analysis showed that the deletion originated from a common ancestor. Family R and Family A members showed segregation of CRC with the presence of this EPCAM mutation. Compared with classic LS, there were almost no extracolonic cancers.

Conclusions: Members of Family R and Family A, all with the same EPCAM deletion, predominantly presented with CRC but no LS-associated endometrial cancer, confirming findings seen in other, smaller, LS families with EPCAM mutations. In these EPCAM mutation carriers, cancer surveillance should be focused on CRC.

Figure 1

Pedigree of Family R. Numbers below the symbols refer to the age in years of last clinical follow-up.

Figure 2

Pedigree of Family A. The clinical data of the relatives that have not been tested are less reliable than those of the tested subjects and the obligate carriers. For pedigree legend see Figure 1. Ca, colorectal adenoma; Cx, cervix; EPCAM; epithelial cell adhesion molecule; Eso, esophagus; Thy, thyroid; Ut, urothelial tract.

Figure 3

EPCAM founder mutation. (a) Schematic representation of the epithelial cell adhesion molecule (EPCAM) founder deletion seen in Families A and R. The deletion encompasses exons 8 and 9 of the EPCAM gene but does not extend into the MSH2 promoter. (b) Representation of Affymetrix SNP6.0 array data of the genomic region around EPCAM in four Dutch Families (including Family A) and three members of USA Family R. Haplotypes of chromosome 2 were derived from homozygous calls of the 75,933 single nucleotide polymorphisms (SNPs) on this chromosome, and positions of discordant homozygous calls (DHCs) were marked. The location of EPCAM is indicated by the box and line. For Family A and Family R, there is a shared region, which includes EPCAM (boxed). Comparing the Dutch family members and one member of Family R (the lane labeled “Merge 5 patients”) there is a stretch of 2,186 SNPs (6.12 Mb) with only five DHCs, strongly indicating a common ancestor. For the Dutch patients, there were two large stretches of 1,341 and 906 SNPs, without DHCs, separated by a single DHC. For Family R, there is a larger stretch of shared SNPs compared with Dutch Family A members. This stretch is 17.22 Mb, 9,850 SNPs long with 81 DHCs. The larger shared haploblock seen in Family R would be consistent with the founding of Family R in the United States by immigration of a single Dutch EPCAM mutation carrier after origination of the deletion in the Netherlands.