Germline pathogenic variants in BRCA1, BRCA2, PALB2 and RAD51C in breast cancer women from Argentina.

PURPOSE: Each year, 17,000 new breast cancer cases are diagnosed in Argentina, and 5400 women die of breast cancer. The contribution of cancer-related mutations to the incidence of breast cancer in Argentina has not yet been explored. METHODS: We sequenced the entire coding regions of BRCA1, BRCA2, PALB2 and RAD51C in 112 unselected Argentinian breast cancer patients. RESULTS: A pathogenic genetic variant was found in 12 of 112 (10.7%) patients; two in BRCA1 (1.8%), five in BRCA2 (4.5%), four in PALB2 (3.6%) and one in RAD51C (0.9%). Three of four (75%) PALB2 mutation carriers carried the same variant (c.1653T > A). CONCLUSIONS: A founder mutation in PALB2 accounts for up to 4% of breast cancer patients in Argentina. BRCA1, BRCA2, PALB2 and RAD51C should be included in the genetic testing panel of breast cancer patients in Argentina.

Preliminary spectrum of genetic variants in familial hypercholesterolemia in Argentina.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated low-density lipoprotein cholesterol and early cardiovascular disease. As cardiovascular disease is a leading cause of mortality in Argentina, early identification of patients with FH is of great public health importance. OBJECTIVE: The aim of our study was to identify families with FH and to approximate to the characterization of the genetic spectrum mutations of FH in Argentina. METHODS: Thirty-three not related index cases were selected with clinical diagnosis of FH. Genetic analysis was performed by sequencing, multiplex ligation-dependent probe amplification, and bioinformatics tools. RESULTS: Twenty genetic variants were identified among 24 cases (73%), 95% on the low-density lipoprotein receptor gene. The only variant on APOB was the R3527Q. Four were novel variants: c.-135C>A, c.170A>C p.(Asp57Ala), c.684G>C p.(Glu228Asp), and c.1895A>T p.(Asn632Ile); the bioinformatics' analysis revealed clear destabilizing effects for 2 of them. The exon 14 presented the highest number of variants (32%). Four variants were observed in more than 1 case and the c.2043C>A p.(Cys681*) was carried by 18% of index cases. Two true homozygotes, 3 compound heterozygotes, and 1 double heterozygote were identified. CONCLUSION: This study characterizes for the first time in Argentina genetic variants associated with FH and suggest that the allelic heterogeneity of the FH in the country could have 1 relative common low-density lipoprotein receptor mutation. This knowledge is important for the genotype-phenotype correlation and for optimizing both cholesterol-lowering therapies and mutational analysis protocols. In addition, these data contribute to the understanding of the molecular basis of FH in Argentina.

Inversions of chromosomes 2 and 6 in mantle cell lymphoma. Cytogenetic, FISH, and molecular studies.

Inversions are infrequent events in hematological malignancies. We here report the cytogenetic, fluorescence in situ hybridization (FISH), and molecular studies of 2 patients diagnosed with mantle cell lymphoma (MCL) that showed inversions of chromosomes 2 and 6 as part of complex karyotypes. Both patients showed a cytogenetically identical inv(6)(p23q11) detected as a secondary aberration. In addition, both patients had a derivative chromosome 2 which originated by partial deletion of the short arm and a pericentric inversion with different breakpoints on the long arm: der(2)del(2)(p21)inv(2)(p21q11) and der(2)del(2)(p21)inv(2)(p21q13), respectively. The presence of t(11;14)(q13;q32) was confirmed by interphase FISH and by molecular study. Residual normal cells were found in both cases. The patients showed a different clinical evolution with a poor outcome for one case and a favorable course of the disease for the other one. The review of the literature in MCL showed a total of 9 inversions affecting different chromosomes. Considering that inversions are very infrequent events in MCL, our findings could be important for detecting genes potentially involved in development and/or progression of this aggressive non-Hodgkin lymphoma subtype.

Evaluation of constitutional chromosome aberrations in hematologic disorders.

We have reviewed 4164 patients with various hematologic disorders cytogenetically studied in our laboratory during the last 25 years to analyze the frequency of constitutional chromosome aberrations (CCA) and to evaluate their association with hematologic malignancies. Our population of patients included 1133 pediatric patients and 3031 adults. Twenty-four (0.58%) cases showed CCA. They included four patients with Robertsonian translocations, one patient with a balanced translocation, two patients with sex chromosome abnormalities, and 17 cases with Down syndrome (DS). Nonsignificant differences among the frequency of patients with CCA from our hematologic series and those observed in the two largest combined surveys of livebirth published (0.65-0.84%) were found. The incidence of DS patients in our population (0.41%) was approximately three times higher than of that observed at birth (0.12-0.17%; P<0.001). The total incidence of constitutional chromosome abnormalities in the non-DS hematologic patients was 0.168% (7 of 4164) lower than of that observed in the newborn population (0.51-0.67%; P<0.001). Nonsignificant differences were found when the incidences of structural aberrations and sex chromosome anomalies were individually compared with the data of the overall population. Our results suggest that the presence of a CCA, other than DS, would not predispose patients to hematologic malignancies.

New chromosome abnormalities and lack of BCL-6 gene rearrangements in Argentinean diffuse large B-cell lymphomas.

OBJECTIVES: Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphomas. Cytogenetic studies have revealed a broad spectrum of clonal genetic abnormalities and complex karyotypes. The purpose of this study was to contribute to the understanding of the genomic alterations associated with this group of lymphomas. METHODS: Cytogenetic, fluorescence in situ hybridization (FISH) and molecular analyses were performed in 30 cases with DLBCL: 20 de novo DLBCL (dn-DLBCL) and 10 DLBCL secondary to follicular lymphoma (S-DLBCL). RESULTS: A total of 37 different structural chromosomal rearrangements were found: 27% translocations, 54% deletions, and 19% other alterations. Chromosomes 8, 6, 2, and 9 were the most commonly affected. Interestingly, translocation t(3;14)(q27;q32) and/or BCL-6 gene rearrangements were not observed either by cytogenetic studies or by FISH analysis. Fifteen novel cytogenetic alterations were detected, among them translocations t(2;21)(p11;q22) and t(8;18)(q24;p11.3) appeared as sole structural abnormalities. Translocation t(14;18)(q32;q21) and/or BCL-2-IGH gene rearrangements were the genomic alterations most frequently observed: 50% of S-DLBCL and 30% of dn-DLBCL. Deletions del(4)(q21), del(6)(q27), del(8)(q11), and del(9)(q11) were recurrent. The most common gains involved chromosome regions at 12q13-q24, 7q10-q32, and 17q22-qter; 6q was the most frequently deleted region, followed by losses at 2q35-qter, 7q32-qter, and 9q13-qter. Four novel regions of loss were identified: 5q13-q21, 2q35-qter (both recurrent in our series), 4p11-p12, and 17q11-q12. CONCLUSIONS: These studies emphasize the value of combining conventional cytogenetics with FISH and molecular studies to allow a more accurate definition of the genomic aberrations involved in DLBCL.

Cytogenetic, FISH, and molecular studies in a case of B-cell chronic lymphocytic leukemia with karyotypic evolution.

We report the clinical, cytogenetic, fluorescence in situ hybridization (FISH) and molecular findings in a 54-yr-old male patient diagnosed with B-cell chronic lymphocytic leukemia (B-CLL), who showed progression to a diffuse large B-cell lymphoma (Richter's syndrome). Genetic studies were performed at diagnosis and during the Richter's transformation (RT). A clonal karyotype with two dicentric chromosomes, psu dic(12,21)(q24;q10) and dic(17,18)(p11.2;p11.2), was found. Both rearrangements were confirmed by FISH. Molecular cytogenetics analysis using p53 probe showed monoallelic loss of this tumor suppressor gene in 43.8% and 77.3% of cells for the first and the second studies, respectively). In both studies, deletions of D13S319 (18% and 12% of cells) and D13S25 loci (13% and 12% of cells) at 13q14 were found. Polymerase chain reaction analysis showed the MBR/JH rearrangement of the bcl-2 gene. FISH studies using LSI bcl-2/IgH probe allowed quantifying the clonal cell population with this rearrangement (4% and 6.6% of cells at diagnosis and RT, respectively). To our knowledge, this is the first case with a psu dic(12,21) described in B-CLL. The low percentage of cells with the 13q14 deletion and bcl-2/IgH rearrangement suggests that they were secondary events that resulted from clonal evolution. Our patient had a short survival (9 months) and a clear lack of response to several therapeutic agents, confirming the association of p53 gene deletion and karyotypic evolution with disease progression.

Structural aberrations of chromosomes 17 and 12 in chronic B-cell disorders.

OBJECTIVES: Genomic aberrations can now be identified in approximately 80% of chronic lymphocytic leukemia, small lymphocytic lymphoma (CLL/SLL) patients. In the present study, four new structural changes involving chromosomes 17 and 12 in CLL/SLL patients are described. METHODS: Five patients were selected for inclusion in the present report among a total of 92 cases with diagnosis of CLL/SLL. Cytogenetic studies and fluorescence in situ hybridization (FISH) analysis to detect some of the most frequent cryptic aberrations occurring in CLL/SLL patients were performed. Clinical studies are also described. RESULTS: Four cases showed structural rearrangements of chromosome 17. A psu dic(17;2)(p11.2;p21), leading to p53 deletion, was observed in a patient who developed a mixed cellularity Hodgkin's disease coexisting with the CLL/SLL in the same lymph node. Epstein Barr virus was detected in the Reed-Sternberg cells. Two cases had a balanced translocation t(2;17)(p21;q23). Both patients showed trisomy 12 and clonal evolution and one of them also had 11q deletion. In addition, a der(17)t(12;17)(q13;q25) as a part of a complex karyotype, and a complex translocation t(5;12;19) (q15;p11;q13) were also found. Four patients had an adverse clinical outcome and died because of disease progression. CONCLUSIONS: Four unreported nonrandom chromosome aberrations in CLL/SLL patients, one of them who might represent a new recurrent abnormality, are described. These uncommon abnormalities, mostly associated with evolving disease, may have implications for the understanding of genetic events associated with disease progression in this pathology.