Carlos Sarroca

Characterization of germline mutations of MLH1 and MSH2 in unrelated south American suspected Lynch syndrome individuals

Lynch syndrome (LS) is an autosomal dominant syndrome that predisposes individuals to development of cancers early in life. These cancers are mainly the following: colorectal, endometrial, ovarian, small intestine, stomach and urinary tract cancers. LS is caused by germline mutations in DNA mismatch repair genes (MMR), mostly MLH1 and MSH2, which are responsible for more than 85% of known germline mutations. To search for germline mutations in MLH1 and MSH2 genes in 123 unrelated South American suspected LS patients (Bethesda or Amsterdam Criteria) DNA was obtained from peripheral blood, and PCR was performed followed by direct sequencing in both directions of all exons and intron–exon junctions regions of the MLH1 and MSH2 genes. MLH1 or MSH2 pathogenic mutations were found in 28.45% (34/123) of the individuals, where 25/57 (43.85%) fulfilled Amsterdam I, II and 9/66 (13.63%) the Bethesda criteria. The mutations found in both genes were as follows: nonsense (35.3%), frameshift (26.47%), splicing (23.52%), and missense (9%). Thirteen alterations (35.14%) were described for the first time. The data reported in this study add new information about MLH1 and MSH2 gene mutations and contribute to better characterize LS in Brazil, Uruguay and Argentina. The high rate of novel mutations demonstrates the importance of defining MLH1 and MSH2 mutations in distinct LS populations.

Mutation spectrum in South American Lynch syndrome families

BackgroundGenetic counselling and testing for Lynch syndrome have recently been introduced in several South American countries, though yet not available in the public health care system.MethodsWe compiled data from publications and hereditary cancer registries to characterize the Lynch syndrome mutation spectrum in South America. In total, data from 267 families that fulfilled the Amsterdam criteria and/or the Bethesda guidelines from Argentina, Brazil, Chile, Colombia and Uruguay were included.ResultsDisease-predisposing mutations were identified in 37% of the families and affected MLH1 in 60% and MSH2 in 40%. Half of the mutations have not previously been reported and potential founder effects were identified in Brazil and in Colombia.ConclusionThe South American Lynch syndrome mutation spectrum includes multiple new mutations, identifies potential founder effects and is useful for future development of genetic testing in this continent.

Frequency of hereditary non-polyposis colorectal cancer among Uruguayan patients with colorectal cancer.

Few studies have investigated the frequency of hereditary non‐polyposis colorectal cancer (HNPCC) in patients with colorectal cancer (CRC), and these have shown marked geographic variations. The aim of this study was to estimate the frequency of HNPCC in a cohort of Uruguayan CRC patients. We included all patients operated consecutively for CRC in the Hospital Central de las Fuerzas Armadas (Uruguay) between 1987 and 2003. Cases were classified into three groups: (i) those fulfilling Amsterdam criteria; (ii) those not fulfilling Amsterdam criteria but considered as a population at increased risk of cancer; and (iii) sporadic CRC. Genetic analysis to detect point mutations in hMLH/hMSH2/hMSH6 genes was performed in group 1 patients. Cases not showing mutations were tested by multiplex ligation‐dependent probe amplification. Among 461 patients, group 1 represented 2.6%, group 2 represented 5.6%, and sporadic cases 91.8%. hMLH1/hMSH2/hMSH6 mutations were found in 25% of cases classified as HNPCC (two in hMLH1 and one in hMSH2). No mutations were detected in hMSH6 gene. The proportion of CRC patients that fulfilled Amsterdam criteria agrees with other reports. However, the percentage of HNPCC cases with identified mutations (25%) may be lower than that reported from other populations. This may reflect, among other possible causes, a different genetic profile in the Uruguayan population.

Hereditary nonpolyposis colorectal cancer (lynch syndrome II) in Uruguay

PURPOSE: We updated an Uruguayan family with hereditary nonpolyposis colorectal cancer first described in 1977, incorporating knowledge of how thehMLH1 germline mutation has been established and shown to segregate in accord with the expected autosomal dominant mode of genetic transmission. METHODS: DNA-based molecular genetic testing was performed in conjunction with genetic counseling. Individuals were provided with their genetic test results, so that at-risk family members would be able to benefit from targeted management programs. RESULTS: We counseled 19 members of this kindred, 13 of whom were positive for thehMLH1 germline mutation. Specific recommendations for surveillance and management were provided. We were able to describe follow-up, including anecdotal cancer survival and pathology findings extending from the initial 1977 report of this family to the present. A remarkable sibship within this kindred was comprised of eight siblings, six of whom underwent resections for colorectal carcinoma between 1963 and 1971. Colon carcinomas before 1977 in this sibship were treated with classic hemicolectomies. Of those who had hemicolectomies for their first primary colorectal cancers, two had a second colon cancer primary, and two had a third colon cancer primary. CONCLUSIONS: Attention given to this extended family with hereditary nonpolyposis colorectal cancer has had a positive impact on the physician community in Uruguay, leading to the identification of additional families with hereditary nonpolyposis colorectal cancer.

Three new mutations in hereditary nonpolyposis colorectal cancer (Lynch syndrome II) in Uruguay.

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common hereditary form of colorectal cancer (CRC). Our purpose is to describe three extended HNPCC families, each of which manifests novel germline mutations in Uruguay, a small country that is a study model for cancer investigation given its high cancer incidence and mortality rate. This is a study of three extended HNPCC families in which extensive genealogic information, medical history, and pathology findings are critically reviewed. DNA testing was performed for evidence of HNPCC mutations. The findings reveal three novel germline mutations, namely MLH1, with a deletion resulting in a frameshift and a premature stop codon (codon 228) in one of the families; in the second family, MSH2 exon 1, codon 61 at nucleotide 181, which results in immediate stop of translation; and in the third family, a mutation in MSH2 at exon 3: the amino acid at nucleotide 530, codon 117, causing a frameshift and a premature stop codon eight base pairs later. We conclude that it is important to study HNPCC mismatch repair genes because of emerging evidence for genotypic and phenotypic heterogeneity, which will harbor the potential to eventually translate this knowledge into specific screening and management protocols. Future projections for such mutations could even contribute to the emergence of molecular-based designer drugs developed through advances in genomics, proteomics, high-throughput screening, and bioinformatics, which would be effective therapeutically for these high-cancer risk patients.

A survey of the clinicopathological and molecular characteristics of patients with suspected Lynch syndrome in Latin America

BackgroundGenetic counselling and testing for Lynch syndrome (LS) have recently been introduced in several Latin America countries. We aimed to characterize the clinical, molecular and mismatch repair (MMR) variants spectrum of patients with suspected LS in Latin America.MethodsEleven LS hereditary cancer registries and 34 published LS databases were used to identify unrelated families that fulfilled the Amsterdam II (AMSII) criteria and/or the Bethesda guidelines or suggestive of a dominant colorectal (CRC) inheritance syndrome.ResultsWe performed a thorough investigation of 15 countries and identified 6 countries where germline genetic testing for LS is available and 3 countries where tumor testing is used in the LS diagnosis. The spectrum of pathogenic MMR variants included MLH1 up to 54%, MSH2 up to 43%, MSH6 up to 10%, PMS2 up to 3% and EPCAM up to 0.8%. The Latin America MMR spectrum is broad with a total of 220 different variants which 80% were private and 20% were recurrent. Frequent regions included exons 11 of MLH1 (15%), exon 3 and 7 of MSH2 (17 and 15%, respectively), exon 4 of MSH6 (65%), exons 11 and 13 of PMS2 (31% and 23%, respectively). Sixteen international founder variants in MLH1, MSH2 and MSH6 were identified and 41 (19%) variants have not previously been reported, thus representing novel genetic variants in the MMR genes. The AMSII criteria was the most used clinical criteria to identify pathogenic MMR carriers although microsatellite instability, immunohistochemistry and family history are still the primary methods in several countries where no genetic testing for LS is available yet.ConclusionThe Latin America LS pathogenic MMR variants spectrum included new variants, frequently altered genetic regions and potential founder effects, emphasizing the relevance implementing Lynch syndrome genetic testing and counseling in all of Latin America countries.

Lynch syndrome in South America: past, present and future.

After decades of unawareness about Lynch syndrome, the medical community in South America is increasingly interested and informed. The visits and support of mentors like H. T. Lynch had been crucial to this awakening. Several countries have at least one registry with skilled personnel in genetic counseling and research. However, this only represents a very restricted resource for the region. According to the GETH, there are 27 hereditary cancer care centers in South America (21 in Brazil, 3 in Argentina, 1 in Uruguay, 1 in Chile and 1 in Peru). These registries differ in fundamental aspects of function, capabilities and funding, but are able to conduct high quality clinical, research and educational activities due to the dedication and personal effort of their members, and organizational support. More support from the governments as well as the participation of the community would boost the initiatives of people leading these groups. Meantime, the collaboration among the South American registries and the involvement of registries and leaders from developed countries will allow to maximize the efficiency in caring for affected patients and their families. The aim of this article is to describe how the knowledge of LS began to be spread in South America, how the first registries were organized and to summarize the current state of progress. In addition, we will provide an update of the clinical and molecular findings in the region.

The Development of the Study of Hereditary Cancer in South America

Benedito Mauro Rossi, Carlos Sarroca, Carlos Vaccaro, Francisco Lopez, Patricia Ashton-Prolla , Fabio de Oliveira Ferreira and Erika Maria Monteiro Santos. Grupo de Estudios de Tumores Hereditarios, São Paulo, SP, Brazil. 2 Hospital Sírio-Libanês, São Paulo, SP, Brazil 3 Hospital Militar, Montevideo, Uruguay. 4 Hospital Italiano, Buenos Aires, Argentina. 5 Clínica Las Condes, Santiago, Chile. 6 Hospital de Clínicas and UFRGS, Porto Alegre, RS, Brazil. 7 A.C.Camargo Cancer Center, São Paulo, SP, Brazil.

From colorectal cancer pattern to the characterization of individuals at risk: picture for genetic research in Latin America: From colorectal cancer pattern to the characterization of individuals at risk: picture for genetic research in Latin America

Colorectal cancer (CRC) is one of the most common cancers in Latin America and the Caribbean, with the highest rates reported for Uruguay, Brazil and Argentina. We provide a global snapshot of the CRC patterns, how screening is performed, and compared/contrasted to the genetic profile of Lynch syndrome (LS) in the region. From the literature, we find that only nine (20%) of the Latin America and the Caribbean countries have developed guidelines for early detection of CRC, and also with a low adherence. We describe a genetic profile of LS, including a total of 2,685 suspected families, where confirmed LS ranged from 8% in Uruguay and Argentina to 60% in Peru. Among confirmed LS, path_MLH1 variants were most commonly identified in Peru (82%), Mexico (80%), Chile (60%), and path_MSH2/EPCAM variants were most frequently identified in Colombia (80%) and Argentina (47%). Path_MSH6 and path_PMS2 variants were less common, but they showed important presence in Brazil (15%) and Chile (10%), respectively. Important differences exist at identifying LS families in Latin American countries, where the spectrum of path_MLH1 and path_MSH2 variants are those most frequently identified. Our findings have an impact on the evaluation of the patients and their relatives at risk for LS, derived from the gene affected. Although the awareness of hereditary cancer and genetic testing has improved in the last decade, it is remains deficient, with 39%–80% of the families not being identified for LS among those who actually met both the clinical criteria for LS and showed MMR deficiency.

Evaluation of MLH1 variants of unclear significance

Inactivating mutations in the MLH1 gene cause the cancer predisposition Lynch syndrome, but for small coding genetic variants it is mostly unclear if they are inactivating or not. Nine such MLH1 variants have been identified in South American colorectal cancer (CRC) patients (p.Tyr97Asp, p.His112Gln, p.Pro141Ala, p.Arg265Pro, p.Asn338Ser, p.Ile501del, p.Arg575Lys, p.Lys618del, p.Leu676Pro), and evidence of pathogenicity or neutrality was not available for the majority of these variants. We therefore performed biochemical laboratory testing of the variant proteins and compared the results to protein in silico predictions on structure and conservation. Additionally, we collected all available clinical information of the families to come to a conclusion concerning their pathogenic potential and facilitate clinical diagnosis in the affected families. We provide evidence that four of the alterations are causative for Lynch syndrome, four are likely neutral and one shows compromised activity which can currently not be classified with respect to its pathogenic potential. The work demonstrates that biochemical testing, corroborated by congruent evolutionary and structural information, can serve to reliably classify uncertain variants when other data are insufficient.