Browsing by Author "Wistuba, Ignacio I."
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- ItemAllelotyping, Microsatellite Instability, and BRAF Mutation Analyses in Common and Atypical Melanocytic Nevi and Primary Cutaneous Melanomas(LIPPINCOTT WILLIAMS & WILKINS, 2009) Uribe, Pablo; Wistuba, Ignacio I.; Gonzalez, SergioLoss of heterozygosity (LOH) in several chromosomal regions is found in melanoma, and it has been partially studied in nevi. BRAF mutations are found in melanoma and nevi and in colorectal cancer are linked to mismatch repair deficiency. We studied early genetic events involved in melanomagenesis through analysis of allelic loss, microsatellite instability (MSI), and BRAF mutations.
- ItemComparative analysis of loss of heterozygosity and microsatellite instability in adult and pediatric melanoma.(2005) Uribe González, Pablo Francisco; Wistuba, Ignacio I.; Solar, Antonieta; Balestrini, Claudia; Perez-Cotapos, Maria Luisa; Gonzalez, SergioAlthough 0.3% of melanomas occur in children, the incidence has risen in past decades. In adult melanoma, some chromosomal regions in 1p, 6q, 9p, 10q, and 11q are frequently deleted. Microsatellite instability (MSI), which reflects impaired DNA repair, has been found at low levels in adult melanoma and melanocytic nevi. To investigate the molecular changes in pediatric melanoma, a screening for loss of heterozygosity and microsatellite instability was performed and compared with changes found in adult melanoma. Formalin-fixed, paraffin-embedded tissues from 10 adult melanomas, 9 melanocytic nevi, and 8 pediatric melanomas were microdissected and the DNA was extracted. Loss of heterozygosity and microsatellite instability were evaluated using 13 microsatellite repeat polymorphisms located in 1p36, 1q32, 2p12, 2p22-25, 2q33-37, 9p21, 10q23.3, 11q23, 13q14, 17p13, and 17q21. The overall frequency of loss of heterozygosity was 0.09 for nevi, 0.30 for adult melanoma, and 0.43 for pediatric melanoma (nevi vs. adult melanoma, P = 0.0082; nevi vs. pediatric melanoma, P = 0.0092). Pediatric melanoma has more loss of heterozygosity (44%) in 11q23 than adult melanoma (7%, P = 0.046). The microsatellite instability overall frequency was greater in pediatric melanoma (0.24) than nevi (0.05, P = 0.0031) and adult melanoma (0.09, P = 0.0195). Our findings suggest that pediatric melanoma has a different abnormal pattern than adult melanoma. Pediatric melanoma has more microsatellite instability than adult melanoma. 11q23 could contain genes related to the early age onset of melanoma. The high frequency of microsatellite instability is coincidental with the finding of higher levels of microsatellite instability in pediatric brain tumors and could play a role in the pathogenesis of pediatric melanoma.
- ItemExtrahepatic Bile Duct Adenocarcinoma: Patients at High-Risk for Local Recurrence Treated with Surgery and Adjuvant Chemoradiation Have an Equivalent Overall Survival to Patients with Standard-Risk Treated with Surgery Alone(2008) Borghero, Yerko; Crane, Christopher H.; Szklaruk, Janio; Oyarzo, Mauricio; Curley, Steven; Pisters, Peter W.; Evans, Douglas; Abdalla, Eddie K.; Thomas, Melanie B.; Das, Prajnan; Wistuba, Ignacio I.; Krishnan, Sunil; Vauthey, Jean-NicolasBackground: Patients with resected extrahepatic bile duct adenocarcinoma who have microscopically positive resection margins and/or pathologic locoregional nodal involvement (R1pN1) have a high-risk of locoregional recurrence, and therefore, we advocate the use of adjuvant chemoradiation. To evaluate the safety and effectiveness of this treatment, we compared survival and side effects outcomes between such patients and patients with negative resection margins and pathologically negative nodes (R0pN0) who did not receive adjuvant treatment.
- ItemFrequent epigenetic inactivation of chromosome 3p candidate tumor suppressor genes in gallbladder carcinoma(ELSEVIER IRELAND LTD, 2007) Riquelme, Erick; Tang, Moying; Baez, Sergio; Diaz, Alfonso; Pruyas, Martha; Wistuba, Ignacio I.; Corvalan, AlejandroGallbladder carcinoma (GBC) is a highly malignant neoplasm that represents the leading cause of death for cancer in Chilean females. There is limited information about the molecular abnormalities involved in its pathogenesis. We have identified a number of molecular changes in GBC, including frequent allelic losses at chromosome 3p regions. Four distinct 3p sites (3p12, 3p14.2, 3p21.3 and 3p22-24) with frequent and early allelic losses in the sequential pathogenesis of this neoplasm have been detected. We investigated epigenetic and genetic abnormalities in GBC affecting 6 candidate tumor suppressor genes (TSG) located in chromosome 3p, including DUTT1 (3p12), FHIT(3p14.2), BLU, RASSF1A, SEMA3B and hMLH1 (3p21.3). DNA extracted from frozen tissue obtained from 50 surgical resected GBCs was examined for gene promoter methylation using MSP (methylation-specific PCR) technique after bisulfite treatment in all 6 genes. In addition, we performed PCR-based mutation examination using SSCP in FHIT and RASSF1A genes and loss of heterozygosity (LOH) analysis using microdissected tissue in a subset of tumors for the 3p21.3 region with 8 microsatellite markers. A very high frequency of GBC methylation was detected in SEMA3B (46/50, 92%) and FHIT (33/50, 66%), inter-mediate incidences in BLU (13/50, 26%) and DUTT1 (11/50, 22%) and very low frequencies in RASSF1A (4/50, 8%) and hMLH1 (2/50, 4%). Allelic loss at 3p21.3 was found in nearly half of the GBCs examined. We conclude that epigenetic inactivation by abnormal promoter methylation is a frequent event in chromosome 3p candidate TSGs in GBC pathogenesis, especially affecting genes SEMA3B (3p21.3) and FHIT (3p 14.2). (c) 2006 Elsevier Ireland Ltd. All rights reserved.
- ItemMismatch repair expression in testicular cancer predicts recurrence and survival(WILEY-LISS, 2008) Velasco, Alfredo; Corvalan, Alejandro; Wistuba, Ignacio I.; Riquelme, Erick; Chuaqui, Rodrigo; Majerson, Alejandro; Leach, Fredrick S.We investigated mismatch repair (MMR) gene expression in testicular cancer as a molecular marker for clinical outcome (recurrence, response to chemotherapy and death) using protein expression and specific genetic alterations associated with the presence or absence of MMR activity. One hundred sixty-two cases of paraffin-embedded testis cancer specimens were subjected to immunohistochemical analysis using monoclonal antibody for MLH1 and MSH2 MMR proteins and genetic analysis using specific polymorphic markers. The degree of MMR immunoreactivity and genetic instability in the form of loss of heterozygosity (LOH) and/or microsatellite instability (MSI) were determined by comparing matched normal and tumor tissue. The degree of immunohistochemical staining for MMR expression was associated with a shorter time to tumor recurrence, resistance to chemotherapy and death. Furthermore, clinical relapse and cancer specific death was also associated with tumors exhibiting a high degree of MSI, p = 0.01 and 0.04, respectively. In contrast, LOH was not associated with recurrence, resistance to chemotherapy or death. Therefore, MMR expression defines testis cancers with distinct molecular properties and clinical behavior, such that tumors with decreased MMR immunostaining and/or increased frequency of MSI have a shorter time to recurrence and death despite chemotherapy. (c) 2007 Wiley-Liss, Inc.
- ItemMismatch repair expression in testicular cancer predicts recurrence and survival(2008) Velasco Palma, Alfredo Alejandro; Corvalán Rodríguez, Alejandro; Wistuba, Ignacio I.; Riquelme, Erick; Chuaqui, Rodrigo; Majerson Grinberg, Alejandro; Leach, Fredrick S.We investigated mismatch repair (MMR) gene expression in testicular cancer as a molecular marker for clinical outcome (recurrence, response to chemotherapy and death) using protein expression and specific genetic alterations associated with the presence or absence of MMR activity. One hundred sixty-two cases of paraffin-embedded testis cancer specimens were subjected to immunohistochemical analysis using monoclonal antibody for MLH1 and MSH2 MMR proteins and genetic analysis using specific polymorphic markers. The degree of MMR immunoreactivity and genetic instability in the form of loss of heterozygosity (LOH) and/or microsatellite instability (MSI) were determined by comparing matched normal and tumor tissue. The degree of immunohistochemical staining for MMR expression was associated with a shorter time to tumor recurrence, resistance to chemotherapy and death. Furthermore, clinical relapse and cancer specific death was also associated with tumors exhibiting a high degree of MSI, p = 0.01 and 0.04, respectively. In contrast, LOH was not associated with recurrence, resistance to chemotherapy or death. Therefore, MMR expression defines testis cancers with distinct molecular properties and clinical behavior, such that tumors with decreased MMR immunostaining and/or increased frequency of MSI have a shorter time to recurrence and death despite chemotherapy. (c) 2007 Wiley-Liss, Inc.