Orofacial clefts (OFC) are among the most common birth defects worldwide. The etiology of non-syndromic OFC is still largely unknown. During embryonic development, the cell adhesion molecule E-cadherin, encoded by CDH1, is highly expressed in the median edge epithelium of the palate. Furthermore, in multiple families with CDH1 mutations, OFC cases are observed. To determine whether CDH1 is a causative gene for non-syndromic OFC and to assess whether CDH1 mutation screening in non-syndromic OFC patients enables identification of families at risk of cancer, direct sequencing of the full coding sequence of CDH1 was performed in a cohort of 81 children with non-syndromic OFC. Eleven children had heterozygous CDH1 sequence variants, 5 cases with 4 distinct missense mutations and 8 cases with 4 intronic variants. Using a combination of in silico predictions and in vitro functional assays, three missense mutations in four non-syndromic OFC patients were predicted to be damaging to E-cadherin protein function. The intronic variants including one tested in an in vitro assay appeared to be benign, showing no influence on splicing. Functionally relevant heterozygous CDH1 missense mutations were found in 4 out of 81 (5%) patients with non-syndromic OFC. This finding opens a new pathway to reveal the molecular basis of non-syndromic OFC. Cancer risk among carriers of these mutations needs to be defined.

Recent studies have reported germline mutations in cases of lobular breast cancer (LBC) not associated with the classical hereditary diffuse gastric cancer syndrome. A multidisciplinary workgroup discussed genetic susceptibility, pathophysiology and clinical management of hereditary LBC (HLBC). The team has established the clinical criteria for screening and results' interpretation, and created consensus guidelines regarding genetic counselling, breast surveillance and imaging techniques, clinicopathological findings, psychological and decisional support, as well as prophylactic surgery and plastic reconstruction. Based on a review of current evidence for the identification of HLBC cases/families, genetic testing is recommended in patients fulfilling the following criteria: (A) bilateral LBC with or without family history of LBC, with age at onset<50 years, and (B) unilateral LBC with family history of LBC, with age at onset <45 years. In asymptomatic mutant carriers, breast surveillance with clinical examination, yearly mammography, contrast-enhanced breast MRI and breast ultrasonography (US) with 6-month interval between the US and the MRI should be implemented as a first approach. In selected cases with personal history, family history of LBC and mutations, prophylactic mastectomy could be discussed with an integrative group of clinical experts. Psychodecisional support also plays a pivotal role in the management of individuals with or without germline alterations. Ultimately, the definition of a specific protocol for genetic screening and ongoing coordinated management of patients with HLBC is crucial for the effective surveillance and early detection of LBC.

a b s t r a c t E-cadherin plays a major role in cell-cell adhesion and inactivating germline mutations in its encoding gene predispose to hereditary diffuse gastric cancer. Evidence indicates that aside from its recognized role in early tumourigenesis, E-cadherin is also pivotal for tumour progression, including invasion and metastization. Herein, we discuss E-cadherin alterations found in a cancer context, associated cellular effects and signalling pathways, and we raise new key questions that will impact in the management of GC patients and families.

Nonsyndromic orofacial cleft (NSOFC) is a complex disease of still unclear genetic etiology. To investigate the contribution of rare epithelial cadherin (CDH1) gene variants to NSOFC, we target sequenced 221 probands. Candidate variants were evaluated via in vitro, in silico, or segregation analyses. Three probably pathogenic variants (c.760G>A [p.Asp254Asn], c.1023T>G [p.Tyr341*], and c.2351G>A [p.Arg784His]) segregated according to autosomal dominant inheritance in four nonsyndromic cleft lip with or without cleft palate (NSCL/P) families (Lod score: 5.8 at θ = 0; 47% penetrance). A fourth possibly pathogenic variant (c.387+5G>A) was also found, but further functional analyses are needed (overall prevalence of CDH1 candidate variants: 2%; 15.4% among familial cases). CDH1 mutational burden was higher among probands from familial cases when compared to that of controls (P = 0.002). We concluded that CDH1 contributes to NSCL/P with mainly rare, moderately penetrant variants, and CDH1 haploinsufficiency is the likely etiological mechanism.

CDH1 encodes E-cadherin, a key protein in adherens junctions. Given that E-cadherin is involved in major cellular processes such as embryogenesis and maintenance of tissue architecture, it is no surprise that deleterious effects arise from its loss of function. E-cadherin is recognised as a tumour suppressor gene, and it is well established that CDH1 genetic alterations cause diffuse gastric cancer and lobular breast cancer—the foremost manifestations of the hereditary diffuse gastric cancer syndrome. However, in the last decade, evidence has emerged demonstrating that CDH1 mutations can be associated with lobular breast cancer and/or several congenital abnormalities, without any personal or family history of diffuse gastric cancer. To date, no genotype–phenotype correlations have been observed. Remarkably, there are reports of mutations affecting the same nucleotide but inducing distinct clinical outcomes. In this review, we bring together a comprehensive analysis of CDH1-associated disorders and germline alterations found in each trait, providing important insights into the biological mechanisms underlying E-cadherin’s pleiotropic effects. Ultimately, this knowledge will impact genetic counselling and will be relevant to the assessment of risk of cancer development or congenital malformations in CDH1 mutation carriers.

The role of E-cadherin in Hereditary Diffuse Gastric Cancer (HDGC) is unequivocal. Germline alterations in its encoding gene (CDH1) are causative of HDGC and occur in about 40% of patients. Importantly, while in most cases CDH1 alterations result in the complete loss of E-cadherin associated with a well-established clinical impact, in about 20% of cases the mutations are of the missense type. The latter are of particular concern in terms of genetic counselling and clinical management, as the effect of the sequence variants in E-cadherin function is not predictable. If a deleterious variant is identified, prophylactic surgery could be recommended. Therefore, over the last few years, intensive research has focused on evaluating the functional consequences of CDH1 missense variants and in assessing E-cadherin pathogenicity. In that context, our group has contributed to better characterize CDH1 germline missense variants and is now considered a worldwide reference centre. In this review, we highlight the state of the art methodologies to categorize CDH1 variants, as neutral or deleterious. This information is subsequently integrated with clinical data for genetic counseling and management of CDH1 variant carriers.

The extracellular matrix (ECM) is a dynamic and highly organized tissue structure, providing support and maintaining normal epithelial architecture. In the last decade, increasing evidence has emerged demonstrating that alterations in ECM composition and assembly strongly affect cellular function and behavior. Even though the detailed mechanisms underlying cell-ECM crosstalk are yet to unravel, it is well established that ECM deregulation accompanies the development of many pathological conditions, such as gastric cancer. Notably, gastric cancer remains a worldwide concern, representing the third most frequent cause of cancer-associated deaths. Despite increased surveillance protocols, patients are usually diagnosed at advanced disease stages, urging the identification of novel diagnostic biomarkers and efficient therapeutic strategies. In this review, we provide a comprehensive overview regarding expression patterns of ECM components and cognate receptors described in normal gastric epithelium, pre-malignant lesions, and gastric carcinomas. Important insights are also discussed for the use of ECM-associated molecules as predictive biomarkers of the disease or as potential targets in gastric cancer.

Missense mutations result in full-length proteins containing an amino acid substitution that can be neutral or deleterious, interfering with the normal conformation, localization, and function of a protein. A striking example is the presence of CDH1 (E-cadherin gene) germline missense variants in hereditary diffuse gastric cancer (HDGC), which represent a clinical burden for genetic counseling and surveillance of mutation carriers and their families. CDH1 missense variants can compromise not only the function of E-cadherin but also its expression pattern. Here, we propose a novel method to characterize E-cadherin signature in order to identify cases with E-cadherin deregulation and functional impairment. The strategy includes a bioimaging pipeline to quantify the expression level and characterize the distribution of the protein from in situ immunofluorescence images. The algorithm computes 1D (dimension intensity) radial and internuclear fluorescence profiles to generate expression outlines and 2D virtual cells representing a typical cell within the populations analyzed. Using this new approach, we verify that cells expressing mutant forms of E-cadherin display fluorescence profiles distinct from those of the wild-type cells. Mutant proteins showed a significantly decrease of fluorescence intensity at the membrane and often abnormal expression peaks in the cytoplasm, reflecting the underlying molecular mechanism of trafficking deregulation. Our results suggest employing this methodology as a complementary approach to evaluate the pathogenicity of E-cadherin missense variants. Moreover, it can be applied to a wide range of proteins and, more importantly, to diseases characterized by aberrant protein expression or trafficking deregulation.