Translocation t(2;7)(p12;q21-22) with dysregulation of the CDK6 gene mapping to 7q21-22 in a non-Hodgkin’s lymphoma with leukemia

Background and Objectives. A female patient presented with splenomegaly and lymphocytosis with atypical lymphoid cell morphology, We identified t(2;7)(p12;q21) prompting studies of the translocation breakpoint and its consequences on protein expression to confirm or otherwise the recently reported involvement of CDK6 and IG kappa genes in the t(2;7) leading to over-expression of CDK6 protein. Design and Methods. A variety of clinical and laboratory techniques including cell marker, cytogenetic and histologic studies were applied in order to establish the diagnosis. Fluorescence in situ hybridization (FISH) and Southern blotting were used for mapping the translocation breakpoint and Western blotting for assessing protein expression. Results. Immunophenotyping showed the presence of a B-cell population with strong expression of FMC7, CD22, CD79b, CD5 and K restricted surface immunoglobulins. Based on morphology and immunophenotypic markers the diagnosis of B-cell nonHodgkin’s lymphoma was made. Karyotyping revealed a clone with t(2;7)(p12;q21-22). Evidence for clonal evolution with additional abnormalities including a deletion of the TP53 was present, We established by FISH and Southern blotting that the breakpoint on 7q21-22 fell in a region 66kb telomeric to the previously reported breakpoint for the t(2;7) and was the same as that observed in a t(7;21). CDK6 protein was over-expressed. The patient received alkylating agents and splenectomy and is alive but the lymphocytosis persists with evidence of disease progression. Interpretations and Conclusions. We have demonstrated that CDK6 expression is dysregulated even when the breakpoint on 7q21-22 is located 66kb upstream from the coding region. Interestingly, the precise assignment of the lymphoma type in our case was not possible even when the splenic histology was analyzed. (C)2002, Ferrata Storti Foundation

Pro-apoptotic and antiproliferative activity of human KCNRG, a putative tumor suppressor in 13q14 region

Deletion of 13q14.3 and a candidate gene KCNRG (potassium channel regulating gene) is the most frequent chromosomal abnormality in B-cell chronic lymphocytic leukemia and is a common finding in multiple myeloma (MM). KCNRG protein may interfere with the normal assembly of the K+ channel proteins causing the suppression of Kv currents. We aimed to examine possible role of KCNRG haploinsufficiency in chronic lymphocytic leukemia (CLL) and MM cells. We performed detailed genomic analysis of the KCNRG locus; studied effects of the stable overexpression of KCNRG isoforms in RPMI-8226, HL-60, and LnCaP cells; and evaluated relative expression of its transcripts in various human lymphomas. Three MM cell lines and 35 CLL PBL samples were screened for KCNRG mutations. KCNRG exerts growth suppressive and pro-apoptotic effects in HL-60, LnCaP, and RPMI-8226 cells. Direct sequencing of KCNRG exons revealed point mutation delT in RPMI-8226 cell line. Levels of major isoform of KCNRG mRNA are lower in DLBL lymphomas compared to normal PBL samples, while levels of its minor mRNA are decreased across the broad range of the lymphoma types. The haploinsufficiency of KCNRG might be relevant to the progression of CLL and MM at least in a subset of patients

Mammalian microRNAs: a small world for fine-tuning gene expression

The basis of eukaryotic complexity is an intricate genetic architecture where parallel systems are involved in tuning gene expression, via RNA-DNA, RNA-RNA, RNA-protein, and DNA-protein interactions. In higher organisms, about 97% of the transcriptional output is represented by noncoding RNA (ncRNA) encompassing not only rRNA, tRNA, introns, 5′ and 3′ untranslated regions, transposable elements, and intergenic regions, but also a large, rapidly emerging family named microRNAs. MicroRNAs are short 20-22-nucleotide RNA molecules that have been shown to regulate the expression of other genes in a variety of eukaryotic systems. MicroRNAs are formed from larger transcripts that fold to produce hairpin structures and serve as substrates for the cytoplasmic Dicer, a member of the RNase III enzyme family. A recent analysis of the genomic location of human microRNA genes suggested that 50% of microRNA genes are located in cancer-associated genomic regions or in fragile sites. This review focuses on the possible implications of microRNAs in post-transcriptional gene regulation in mammalian diseases, with particular focus on cancer. We argue that developing mouse models for deleted and/or overexpressed microRNAs will be of invaluable interest to decipher the regulatory networks where microRNAs are involved

Delineation of the minimal region of loss at 13q14 in multiple myeloma

Previous studies have focused on the incidence and prognostic implications of 13q14 deletions in multiple myeloma (MM), but none has sought to delineate the minimal common deleted region (CDR). In an effort to do so, dual-color interphase fluorescence in situ hybridization (FISH) was applied on 82 myeloma cases, initially by use of three probes for 13q14 (RBI, D13S319, and DIMS). Deletions were detected in 29/82 (35.4%) cases, and all except one were monoallelic. Subsequently, contiguous YACs, PACs, and a BAC spanning the 13q14-q21 region were employed for deletion mapping in addition to a 13q telomere probe. Large deletions extending to the 13q34 region were found in 55% of the deleted cases, whereas an additional 13.8% showed loss of both 13q34 and 13q 14 regions with retention of 13q21. A CDR of approximately 350 kb was identified at 13q 14 with the proximal border approximately 120 kb centromeric from D13S319, encompassing an area rich in expressed sequence tagged sites and containing DLEU1, DLEU2, and RFP2 genes. Direct sequencing of the RFP2 gene revealed no mutations in six patients and four MM cell lines harboring deletions of the CDR. However, a role for RFP2 in the pathogenesis of MM cannot yet be excluded, given that alternative mechanisms such as haploinsufficiency remain possible. (C) 2003 Wiley-Liss, Inc