Latin American Study of Hereditary Breast and Ovarian Cancer LACAM: A Genomic Epidemiology Approach.

Purpose: Hereditary Breast and Ovarian Cancer (HBOC) syndrome is responsible for ~5-10% of all diagnosed breast and ovarian cancers. Breast cancer is the most common malignancy and the leading cause of cancer-related mortality among women in Latin America (LA). The main objective of this study was to develop a comprehensive understanding of the genomic epidemiology of HBOC throughout the establishment of The Latin American consortium for HBOC-LACAM, consisting of specialists from 5 countries in LA and the description of the genomic results from the first phase of the study. Methods: We have recruited 403 individuals that fulfilled the criteria for HBOC from 11 health institutions of Argentina, Colombia, Guatemala, Mexico and Peru. A pilot cohort of 222 individuals was analyzed by NGS gene panels. One hundred forty-three genes were selected on the basis of their putative role in susceptibility to different hereditary cancers. Libraries were sequenced in MiSeq (Illumina, Inc.) and PGM (Ion Torrent-Thermo Fisher Scientific) platforms. Results: The overall prevalence of pathogenic variants was 17% (38/222); the distribution spanned 14 genes and varied by country. The highest relative prevalence of pathogenic variants was found in patients from Argentina (25%, 14/57), followed by Mexico (18%, 12/68), Guatemala (16%, 3/19), and Colombia (13%, 10/78). Pathogenic variants were found in BRCA1 (20%) and BRCA2 (29%) genes. Pathogenic variants were found in other 12 genes, including high and moderate risk genes such as MSH2, MSH6, MUTYH, and PALB2. Additional pathogenic variants were found in HBOC unrelated genes such as DCLRE1C, WRN, PDE11A, and PDGFB. Conclusion: In this first phase of the project, we recruited 403 individuals and evaluated the germline genetic alterations in an initial cohort of 222 patients among 4 countries. Our data show for the first time in LA the distribution of pathogenic variants in a broad set of cancer susceptibility genes in HBOC. Even though we used extended gene panels, there was still a high proportion of patients without any detectable pathogenic variant, which emphasizes the larger, unexplored genetic nature of the disease in these populations.

Thymidylate synthase gene variants as predictors of clinical response and toxicity to fluoropyrimidine-based chemotherapy for colorectal cancer.

BACKGROUND: Fluoropyrimidines form the chemotherapy backbone of advanced and metastatic colorectal cancer (CRC). These drugs are frequently associated with toxicity events that result in dose adjustments and even suspension of the treatment. The thymidylate synthase (TYMS) gene is a potential marker of response and toxicity to fluoropyirimidines as this enzyme is the molecular target of these drugs. Our aim was to assess the association between variants of TYMS with response and toxicity to fluoropyrimidines in patients with CRC in independent retrospective and prospective studies. METHODS: Variants namely rs45445694, rs183205964, rs2853542 and rs151264360 of TYMS were genotyped in 105 CRC patients and were evaluated to define their association with clinical response and toxicity to fluoropyrimidines. Additionally, the relationship between genotypes and tumor gene expression was analyzed by quantitative polymerase chain reaction. RESULTS: The 2R/2R (rs45445694) was associated with clinical response (p=0.05, odds ratio (OR)=3.45) and severe toxicity (p=0.0014, OR=5.21, from pooled data). Expression analysis in tumor tissues suggested a correlation between the 2R/2R genotype and low TYMS expression. CONCLUSIONS: The allele 2R (rs45445694) predicts severe toxicity and objective response in advanced CRC patients. In addition, the alleles G(rs2853542) and 6bp-(rs151264360) are independent predictors of response failure to chemotherapy. This is the first study made on a Latin American population that points out TYMS gene variants have predictive values for response and toxicity in patients with CRC treated with fluoropyrimidine-based chemotherapy.

[Pharmacogenomics of the first-line treatment for gastric cancer: advances in the identification of genomic biomarkers for clinical response to chemotherapy]. / Farmacogenómica del tratamiento de primera linea en el cáncer gástrico: avances en la identificación de los biomarcadores genómicos de respuesta clínica.

Gastric cancer (GC) is often diagnosed at later stages due to the lack of specificity of symptoms associated with the neoplasm, causing high mortality rates worldwide. The first line of adjuvant and neoadjuvant treatment includes cytotoxic fluoropyrimidines and platin-containing compounds which cause the formation of DNA adducts. The clinical outcome with these antineoplastic agents depends mainly on tumor sensitivity, which is conditioned by the expression level of the drug targets and the DNA-repair system enzymes. In addition, some germ line polymorphisms, in genes linked to drug metabolism and response to chemotherapy, have been associated with poor responses and the development of adverse effects, even with fatal outcomes in GC patients. The identification of genomic biomarkers, such as individual gene polymorphisms or differential expression patterns of specific genes, in a patient-by-patient context with potential clinical application is the main focus of current pharmacogenomic research, which aims at developing a rational and personalized therapy (i.e., a therapy that ensures maximum efficacy with no predictable side effects). However, because of the future application of genomic technologies in the clinical setting, it is necessary to establish the prognostic value of these genomic biomarkers with genotype-phenotype association studies and to evaluate their prevalence in the population under treatment. These issues are important for their cost-effectiveness evaluation, which determines the feasibility of using these medical genomic research products for GC treatment in the clinical setting.

Farmacogenómica del tratamiento de primera línea en el cáncer gástrico: avances en la identificación de los biomarcadores genómicos de respuesta clínica / Pharmacogenomics of the first-line treatment for gastric cancer: advances in the identification of genomic biomarkers for clinical response to chemotherapy

Debido a la inespecificidad de los síntomas, el cáncer gástrico (CG) es diagnosticado frecuentemente en etapas avanzadas, lo que da cuenta de los altos índices de mortalidad debido a esta neoplasia a nivel mundial. El esquema de tratamiento adyuvante o neoadyuvante en los países occidentales incluye el uso de fluoropirimidinas citotóxicas y compuestos de platino formadores de aductos en el ADN. La respuesta clínica al tratamiento con estos fármacos depende principalmente de la sensibilidad del tumor, la cual a su vez está condicionada por el nivel de expresión de los blancos terapéuticos y de las enzimas de reparación del ADN. Sumado a esto, algunos polimorfismos de línea germinal en genes asociados al metabolismo y a la respuesta a estos fármacos, han mostrado asociación con respuestas pobres y con el desarrollo de eventos adversos, incluso con resultados fatales. La identificación de biomarcadores genómicos, en la forma de polimorfismos genéticos o la expresión diferencial de genes específicos asociados a la respuesta quimioterapeútica ha sido motivo de intensa investigación como base para la aplicación de la farmacogenómica en el establecimiento de una terapia farmacológica racional y personalizada del CG. Sin embargo, ante la eventual aplicación de la farmacogenómica en el ámbito clínico, es necesario establecer el valor pronóstico real de dichos biomarcadores mediante los estudios de asociación genotipo-fenotipo, así como su prevalencia en el contexto de cada población de pacientes. Estos aspectos son indispensables al evaluar la relación costo-efectividad de la introducción de los productos de la medicina genómica predictiva en el tratamiento del CG.

Gastric cancer (GC) is often diagnosed at later stages due to the lack of specificity of symptoms associated with the neoplasm, causing high mortality rates worldwide. The first line of adjuvant and neoadjuvant treatment includes cytotoxic fluoropyrimidines and platin-containing compounds which cause the formation of DNA adducts. The clinical outcome with these antineoplastic agents depends mainly on tumor sensitivity, which is conditioned by the expression level of the drug targets and the DNA-repair system enzymes. In addition, some germ line polymorphisms, in genes linked to drug metabolism and response to chemotherapy, have been associated with poor responses and the development of adverse effects, even with fatal outcomes in GC patients. The identification of genomic biomarkers, such as individual gene polymorphisms or differential expression patterns of specific genes, in a patient-by-patient context with potential clinical application is the main focus of current pharmacogenomic research, which aims at developing a rational and personalized therapy (i.e., a therapy that ensures maximum efficacy with no predictable side effects). However, because of the future application of genomic technologies in the clinical setting, it is necessary to establish the prognostic value of these genomic biomarkers with genotype-phenotype association studies and to evaluate their prevalence in the population under treatment. These issues are important for their cost-effectiveness evaluation, which determines the feasibility of using these medical genomic research products for GC treatment in the clinical setting.