It was with great interest that we read the recent article by Schrader et al. on the low frequency of CDH1 mutations in early-onset and familial lobular breast cancer (1). As detailed by Schrader et al., the cancer syndrome hereditary diffuse gastric cancer (HDGC), in addition to a high risk of diffuse gastric cancer (DGC), is associated with an increased risk of lobular breast carcinoma, a specific histological subtype of the disease (2,3). Germline mutations in CDH1, encoding E-cadherin have been identified as the underlying cause of HGDC in 30-50% of families (4). We have identified a deletion of exon 16 occurring in an individual with lobular breast cancer with an associated family history of gastric cancer. In addition, several groups have reported infrequent CDH1 inactivating mutations in sporadic and familial cases of lobular breast carcinoma that are not associated with HGDC (5-8).

An increased incidence of breast cancer has also been reported in families with Saethre-Chotzen syndrome (SCS) (9), an autosomal dominant craniosynostosis syndrome, which is characterised by premature fusion of coronal sutures and limb abnormalities. SCS is caused by mutations in the basic helix-loop-helix transcription factor TWIST1. Interestingly, TWIST1 over-expression has been associated with breast cancer progression and metastasis through loss of E-cadherin mediated cell-cell adhesion (10).

As part of our continuing study on factors contributing to the risk of breast cancer, we have recently undertaken a similar study to investigate the contribution of variants in CDH1 and TWIST1 to lobular breast cancer in a familial setting. We selected 104 unrelated individuals with lobular breast cancer, all with a family history of breast cancer fulfilling NICE criteria for BRCA1 and BRCA2 screening (>20% risk of mutation) (11). Sequence analysis and multiplex ligation-dependent probe amplification (MLPA) of BRCA1 and BRCA2 identified no mutations in this group. The age at first presentation of the probands ranged from 28-68 years and 14 patients had bilateral breast cancer. All 104 were screened for germline mutations in the coding regions of CDH1 and TWIST1 and 86 were successfully analysed for large deletions/amplifications in CDH1 using MLPA.

Like Schrader et al., we found no truncating point mutations in CDH1 however, a heterozygous deletion of CDH1 exons 1 and 2 was observed in one patient. Three of her sisters were also affected with lobular disease, two with invasive breast cancer. In one of these, with lobular carcinoma in situ, DNA was available for testing and confirmed the presence of the mutation. The four sisters were aged 50, 49, 51 and 53 years at diagnosis of lobular breast cancer, the proband eventually dying from primary pancreatic cancer aged 60 years. There was no history of gastric cancer in up to third degree relatives in the family. Oliveira et al. previously reported deletion of CDH1 exons 1 and 2 segregating in three families with familial gastric cancer (4), one of which was associated with lobular breast cancer. However, our finding is the first report of a CDH1 deletion in the context of lobular breast cancer without a history of gastric cancer.

A novel non-synonymous change in exon 5 of CDH1, c.670C>T, p.R224C, was identified in one patient. DNA was unavailable from an affected family member to test for segregation. The variant was not identified in a panel of 180 ethnically matched healthy controls. However, in-silico analysis (Polyphen) predicted this missense change to be benign and the residue is not conserved across species. Therefore, it is inconclusive if this variant predisposes to breast cancer in this family.

A novel synonymous change c.2451G>A in CDH1 exon 16 was observed in two patients and four patients had the intronic variant c.532-18C>T which has not been described in SNP databases. There is no evidence to support pathogenicity for these variants.

No mutations were identified in TWIST1.

In agreement with Schrader et al., we conclude that germline mutations in CDH1 are not common in familial lobular breast cancer. Although large single or multiple exon deletions can be occasionally identified in association with a highly penetrant phenotype for lobular breast cancer. We cannot however rule out the possibility that hypermethylation of promoter and regulatory regions of both CDH1 and TWIST1 contribute to the altered expression of these genes frequently observed in breast tumours. Additional studies are needed to provide more insight into the aetiology of lobular breast carcinoma and to identify further causal variants.

Acknowledgements. This work was funded through support of the NIHR Manchester Biomedical Research Centre and Central Manchester Foundation Trust Research Grant.

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Conflict of Interest:

None declared