Complementary molecular approaches reveal heterogeneous CDH1 germline defects in Italian patients with hereditary diffuse gastric cancer (HDGC) syndrome

Abstract

Germline inactivation of the E-cadherin gene (CDH1) is associated with hereditary diffuse gastric cancer (HDGC), a rare autosomal dominant syndrome predisposing to both diffuse gastric cancer (DGC) and lobular breast cancer (LBC). We searched for CDH1 germline defects in 32 HDGC Italian probands selected according to international consensus criteria and in 5 selected relatives. We used a series of molecular methods, including: DNA sequencing, multiplex ligation-dependent probe amplification, single-nucleotide primer extension, bisulfite sequencing, reverse-transcription PCR, and bioinformatics tools. We identified pathogenic mutations in 6 out of 32 probands (19%): one truncating and two missense mutations, one large deletion, one allelic expression imbalance and one splicing defect. Three out of six CDH1 constitutive alterations were novel. Our data support the need for a multimethod approach for CDH1 genetic testing, demonstrating that both DNA and RNA analyses are required to increase the detection rate of pathogenic mutations, thus reducing the number of patients without a clear molecular diagnosis. On the whole, our results indicate that not only DGC patients, but also subjects with personal or family history of LBC might benefit from CDH1 genetic testing. Moreover, our findings support the notion that prophylactic gastrectomy should be offered to asymptomatic CDH1 mutation carriers; indeed, while endoscopic analysis with histological examination of random gastric biopsies can miss cancer foci, gastrectomy performed in these subjects always revealed foci of cancer cells.

Accuracy of Hereditary Diffuse Gastric Cancer Testing Criteria and Outcomes in Patients With a Germline Mutation in CDH1

“…13,32 The current HDGC criteria and accompanying mutation detection rates of 30-50% are based on small, highly selected series of gastric cancer patients. 15,16,30,33,34 Most of these studies were published before 2010 and included families that fulfilled the original strict HDGC criteria: (i) two or more gastric carcinomas in first-degree relatives with at least one DGC diagnosed before age 50 or; (ii) three or more DGC in first-degree relatives diagnosed at any age. For these two criteria, the CDH1 mutation detection rate in our cohort is only 21% (13/63).…”

Hereditary diffuse gastric cancer in two families: A case report

“…As her maternal grandmother was diagnosed with DGC at 64 years of age, documented with a pathological report, a CDH1 molecular test was performed. This test revealed a pathogenic deletion of exons 7-8 of CDH1 (11). The patient underwent gastroscopy with 36 random biopsies, all of which were negative.…”

“…A mutational screening of the CDH1 gene was previously carried out by complementary molecular approaches including DNA sequencing, multiplex ligation-dependent probe amplification, single-nucleotide primer extension, bisulfite sequencing, reverse transcription-polymerase chain reaction and bioinformatics tools (11). During that screening, a c.688-1G>C mutation affecting mRNA splicing and leading to a premature termination codon were identified in case 1, whereas an intragenic deletion of exons 7 and 8 were identified in case 2 (11 A second line of chemotherapy was initiated with 8 cycles of irinotecan and capecitabine.…”

“…During that screening, a c.688-1G>C mutation affecting mRNA splicing and leading to a premature termination codon were identified in case 1, whereas an intragenic deletion of exons 7 and 8 were identified in case 2 (11 A second line of chemotherapy was initiated with 8 cycles of irinotecan and capecitabine. Even though the pedigree was silent at that time, due to her young age, she was offered genetic counseling and was tested for CDH1.…”

“…Even though the pedigree was silent at that time, due to her young age, she was offered genetic counseling and was tested for CDH1. The results revealed a pathogenic splicing mutation (11). As there was no family history of gastric cancer, her parents were tested.…”