Amplification of IGH/CCND1 fusion gene in a primary plasma cell leukemia case

Genetic and expression variations of cell cycle pathway genes in brain tumor patients

The present study was designed to determine the association between the genetic polymorphisms/expression variations of RB1 and CCND1 genes and brain tumor risk. For this purpose, 250 blood samples of brain tumor patients along with 250 controls (cohort I) and 96 brain tumor tissues (cohort II) with adjacent control section were collected. Mutation analysis of RB1 (rs137853294, rs121913300) and CCND1 (rs614367, rs498136) genes was performed using ARMS-PCR followed by sequencing, and expression analysis was performed using real-time PCR and immunohistochemistry. The results showed homozygous mutant genotype of RB1 gene polymorphism, rs121913300 (P=0.003) and CCND1 gene polymorphism rs614367 (P=0.01) were associated significantly with brain tumor risk. Moreover, significant down-regulation of RB1 (P=0.005) and up-regulation of CCND1 (P=0.0001) gene was observed in brain tumor sections vs controls. Spearman correlation showed significant negative correlation between RB1 vs proliferation marker, Ki-67 (r = -0.291*, P<0.05) in brain tumors. Expression levels of selected genes were also assessed at protein level using immunohistochemical analysis (IHC) and signification down-regulation of RB1 (P=0.0001) and up-regulation of CCND1 (P=0.0001) was observed in brain tumor compared with control sections. In conclusion, it is suggested that polymorphisms/expression variations of RB1 and CCND1 genes may be associated with increased risk of brain tumor.

CCND1-IGH Fusion-Amplification and MYC Copy Number Gain in a Case of Pleomorphic Variant Mantle Cell Lymphoma

OBJECTIVES

Mantle cell lymphoma (MCL) may present de novo or undergo progression to a clinically aggressive variant, known as a blastoid or pleomorphic variant. We report an unusual case of classic MCL in a 78-year-old man with a typical immunophenotype, including CD5 positivity, who subsequently relapsed with CD5-negative pleomorphic variant MCL.

METHODS

Biopsy specimens were evaluated using Wright-Giemsa-stained or H&E-stained sections, flow cytometry, immunohistochemistry, conventional cytogenetic, next-generation sequencing, and fluorescence in situ hybridization.

RESULTS

The patient continued to be refractory to intensive chemotherapy and radiation therapy. Initial conventional cytogenetic analysis showed a complex karyotype with amplification of the CCND1-IGH fusion gene on the der(14): 44, Y, t(X;2)(p22.3;q21), del(2)(p21), del(6)(p23), add(7)(p22),-9, del(9)(p22), add(11)(q13),-13, add(14)(p11.2), der(14)t(11;14)(q13;q32)hsr(14)(q32), add(18)(q23), add(21)(p11.1),-22,+mar[12]. A repeat biopsy revealed MCL, pleomorphic variant, with loss of CD5 expression and extra copies of the MYC CONCLUSIONS: CCND1-IGH fusion-amplification with MYC copy number gain is extremely rare and may play a role in disease progression in a subset of MCL cases.

F-box protein FBXL2 targets cyclin D2 for ubiquitination and degradation to inhibit leukemic cell proliferation

Hematologic maligancies exhibit a growth advantage by up-regulation of components within the molecular apparatus involved in cell-cycle progression. The SCF (Skip-Cullin1-F-box protein) E3 ligase family provides homeostatic feedback control of cell division by mediating ubiquitination and degradation of cell-cycle proteins. By screening several previously undescribed E3 ligase components, we describe the behavior of a relatively new SCF subunit, termed FBXL2, that ubiquitinates and destabilizes cyclin D2 protein leading to G(0) phase arrest and apoptosis in leukemic and B-lymphoblastoid cell lines. FBXL2 expression was strongly suppressed, and yet cyclin D2 protein levels were robustly expressed in acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) patient samples. Depletion of endogenous FBXL2 stabilized cyclin D2 levels, whereas ectopically expressed FBXL2 decreased cyclin D2 lifespan. FBXL2 did not bind a phosphodegron within its substrate, which is typical of other F-box proteins, but uniquely targeted a calmodulin-binding signature within cyclin D2 to facilitate its polyubiquitination. Calmodulin competes with the F-box protein for access to this motif where it bound and protected cyclin D2 from FBXL2. Calmodulin reversed FBXL2-induced G(0) phase arrest and attenuated FBXL2-induced apoptosis of lymphoblastoid cells. These results suggest an antiproliferative effect of SCF(FBXL2) in lymphoproliferative malignancies.