Browsing by Author "Carvallo, Pilar"

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    ATM allelic variants associated to hereditary breast cancer in 94 Chilean women: susceptibility or ethnic influences?
    (2008) Tapia, Teresa; Sanchez, Alejandro; Vallejos, Maricarmen; Alvarez, Carolina; Moraga, Mauricio; Smalley, Susan; Camus, Mauricio; Alvarez, Manuel; Carvallo, Pilar
    Besides BRCA1 and BRCA2, two genes accounting for a small proportion of breast cancer cases, ATM has been widely proposed as a low-penetrance susceptibility gene. Several nucleotide changes have been proposed to be associated with breast cancer, still remaining a high controversy in this sense. We screened the ATM gene in 94 breast cancer patients selected from 78 high-risk families, not presenting a mutation in BRCA1 or BRCA2. We found three novel allelic variants: IVS64 + 51delT and p.L752L, not showing association with hereditary breast cancer, and p.L694L found in one family in two breast cancer patients. Two amino acid substitutions p.S707P and p.F858L, previously reported to be associated with breast cancer, were present in our study in cases and controls, lacking of association with breast cancer. A positive association of c. 5557G > A (p.D1853N) was found (OR 2.52, P = 0.008), when analyzed alone and in combination with an intronic variant IVS24-9delT (OR 3.97; P = 0.0003). We postulate that our discrepancies with other reports related to the associated ATM alleles to hereditary breast cancer, as well as discrepancies in the literature between other groups, could be explained by the diversity in the ethnic origins of families gathered in a sole study, and the selection of the control group. In relation to this issue, and based on genetic markers, we found that the Chilean group of breast cancer families in this study has a stronger European genetic component than our control sample selected randomly from the Chilean population.
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    BRCA1 and BRCA2 screening of nine Chilean founder mutations through allelic-discrimination and real-time PCR in breast/ovarian cancer patients
    (2022) Alvarez, Carolina; Ortega-Hernandez, Victoria; Cortez, Aracely; Carvallo, Pilar
    Background In a previous work, we identified nine founder mutations present in close to 80% of BRCA1 and BRCA2 mutation carriers, and distributed across the country. The presence of founder mutations constitutes a valuable opportunity to develop new strategies for genetic screening. Genetic tests are primarily performed by NGS sequencing, which requires sophisticated and expensive equipment, and it takes 2-3 weeks for the results to be informed to the patient. In addition, genetic tests are not covered by insurance companies in Latin American countries. In this work, we present the standardization and technical validation of a real-time PCR based methodology for allelic discrimination in order to identify the nine Chilean founder mutations in BRCA1 and BRCA2 genes. Methods and results We designed nine pairs of probes and nine pairs of primers to amplify synchronically nine regions of the BRCA1/BRCA2 genes by real-time PCR, in order to identify the nine founder mutations through allelic discrimination analyses. Technical validation was performed using 90 positive and 90 negative samples for each mutation. The methodology was tested in a second group of 60 patients. Our method correctly classified carriers and non-carriers of one of the nine Chilean founder mutations with a 100% specificity and 100% sensitivity, compared with Sanger sequencing performance. Conclusions We develop an inexpensive, simple, and fast mutation detection method that could be implemented locally in Hospitals from the Private to Public health system. This methodology may be useful for the screening of BRCA1 and BRCA2 mutations in other populations.
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    Is Single-Strand Conformation Polymorphism Analysis of the Full 5′ Untranslated Region an Adequate Approach To Study Hepatitis C Virus Quasispecies Distribution?
    (2009) Vera-Otarola, Jorge; Barria, Maria Ines; Leon, Ursula; Carvallo, Pilar; Soza, Alejandro; Lopez-Lastra, Marcelo
    Single-strand conformation polymorphism (SSCP) analysis is used by many laboratories to study the quasispecies distribution of the hepatitis C virus (HCV). Here we question the validity of this experimental approach, as conclusions are drawn from the analysis of the migration patterns of two ssDNA molecules and not from RNA. Using previously characterized mutants of the HCV 5' untranslated regions, we show that contrary to what has been predicted, SSCP migration patterns of DNA amplicons with differences in their nucleotide sequences generated from the full 5' UTR of HCV are not necessarily unique.
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    Promoter hypermethylation of BRCA1 correlates with absence of expression in hereditary breast cancer tumors
    (TAYLOR & FRANCIS INC, 2008) Tapia, Teresa; Smalley, Susan V.; Kohen, Paulina; Munoz, Alex; Solis, Luisa M.; Corvalan, Alejandro; Faundez, Paola; Devoto, Luigi; Camus, Mauricio; Alvarez, Manuel; Carvallo, Pilar
    Germline mutations in BRCA1 account for a low proportion of hereditary cases in diverse populations. Several efforts have been made to find new genes involved in the inheritance of breast cancer with no success until today. The participation of BRCA1 in the development of breast cancer has been proposed in several studies where hypermethylation of its promoter and a decrease in expression has been reported for sporadic cases and one study on familial cases. To explore the participation of BRCA1 in hereditary carcinogenesis through a different mechanism than the inheritance of germline mutations, we studied the methylation status of its promoter in breast tumors, from patients previously screened for BRCA1/BRCA2 germline mutations. We also determined the presence of the BRCA1 protein in these tumors and correlated both events with tumor grade, hormone receptors and ERBB2 presence. Promoter hypermethylation of the BRCA1 gene was detected in 51% of our biopsies, among which 67% did not express the respective protein. This result leads us to suggest that hypermethylation could be considered as an inactivating mechanism for BRCA1 expression, either as a first or second hit. Moreover, a number of biopsies with absence of expression on BRCA1 showed negative detection of estrogen and progesterone receptors, a similar phenotype to BRCA1 mutated breast tumors.