Mantle cell lymphomas with low levels of cyclin D1 long mRNA transcripts are highly proliferative and can be discriminated by elevated cyclin A2 and cyclin B1

Abstract

The role of transcript variants of cyclin D1 in cancer biology is unclear. Most tumors with high levels of cyclin D1 express 2 transcripts due to alternative splicing: one full-length transcript of 4.4 kb and one short transcript of approximately 1.7 kb. The short transcript lacks part of the 3 0 UTR region regulating mRNA stability and has a longer half-life. In our study, the contribution of each of these mRNAs to gene expression and cell proliferation has been investigated in mantle cell lymphoma (MCL), a B cell lymphoma characterized by a specific gene translocation resulting in enhanced expression of cyclin D1. A subset of MCL tumors with low levels of the long cyclin D1 transcript (cyclin D1 3 0 UTR) was identified by quantitative PCR and by oligonucleotide array hybridization. This tumor-subset had 3.4-fold higher levels of the short form of cyclin D1 mRNA (p < 0.0001) and had higher expression of cyclin D1 protein. Gene expression analysis identified a number of cell-cycle regulatory genes as upregulated. There was a significant difference in frequencies of cyclin B1 (p 5 0.0006) and cyclin A2 (p 5 0.0006) positive cells that discriminated MCL with low cyclin D1 3 0 UTR from other highly proliferative MCL. Among differentially expressed genes, there was a highly upregulated gene with homology to the group of cell-cycle promoting E2F transcription partners, E2F_TDP5. Several of the upregulated genes, such as TOP2A, AURORA A and RRM2 may influence a response to therapy. Identification of MCL with low cyclin D1 3 0 UTR is important because it seems to be associated with shorter overall survival. ' 2005 Wiley-Liss, Inc.Key words: mantle cell lymphoma; cyclins; CCND1 3 0 UTR; proliferation; expression profiling; micro array In most tumors demonstrating inappropriately high levels of cyclin D1 gene expression, 2 cyclin D1 transcripts are present due to alternative polyadenylation: one full-length transcript of 4.4 kb and one shorter transcript of 1.7 kb.1 The short transcript lacks the 3 0 -UTR, AU-rich, sequences of the mRNA containing destabilizing elements (Fig. 1). The role of long and short cyclin D1 transcript in cancer biology is unclear. The aberrant expression of cyclin leads to a disturbed cell cycle regulation; cyclin D1 binds to cyclin dependent kinase Cdk4 and initiates phosphorylation of Rb resulting in the release of E2F and transcriptional activation of S-phase genes.2 It has also been suggested that cyclin D1 sequesters Cip/Kip cell cycle inhibitors such as p21waf1 and p27Kip1 from cyclinE/Cdk2 complexes thereby relieving the inhibitory effect and further inducing progression toward S-phase.3 In addition to the cell cycle related functions, cyclin D1 is a transcriptional activator 2 that induces gene expression not only via the E2F transcription factors but also by modifying the effects of transcription factors such as C/EBP beta 4 and other targets, not yet wellcharacterized. 2Mantle cell lymphoma (MCL) is a non-Hodgkin lymphoma of B cell origin that expresses the B cell markers CD20 and CD7...

3’UTR mediated regulation of the cyclin D1 proto-oncogene

“…In support of this hypothesis, the loss of the cyclin D1 3'UTR has been linked to hyper-proliferative forms of MCL. 18 A number of studies have hypothesized that AREs in the 3'UTR could potentially destabilize the cyclin D1 3'UTR and therefore their loss could contribute to enhanced stability and overexpression of cyclin D1 protein. Using a sensitive reporter assay, the deletion of the AREs in the cyclin D1 3'UTR actually leads to a marked reduction in reporter activity suggesting that AREs have a stabilizing function on the cyclin D1 mRNA.…”

“…17 Hyper-proliferative forms of MCL are characterised by high levels of cyclin D1, especially a shorter transcript which has been associated with a poor prognosis. 18 These shorter forms of cyclin D1 in MCL were believed to derive from an alternatively splicing event which generates a shorter isoform of the cyclin D1 gene. However, in a number of MCL patients, it has recently been demonstrated that the shorter isoforms of the cyclin D1 gene in MCL result from genomic deletions or point mutations that prematurely truncate the cyclin D1 3'UTR.…”

The R-Ras interaction partner ORP3 regulates cell adhesion

“…Analysis of chromosomal abnormalities has revealed that the ORP3 (OSBPL3 -HGNC database) gene region in chromosome 7 is often gained and overexpressed in colon tumors and osteosarcoma (Ozaki et al, 2003;Staub et al, 2006;Tsafrir et al, 2006). Increased expression of ORP3 mRNA has frequently been reported in B-cell-associated malignancies (Ando et al, 2003;Sander et al, 2005;Chng et al, 2006;Ek et al, 2006) and testicular cancer (Sperger et al, 2003;Yamada et al, 2004;Almstrup et al, 2005;Gashaw et al, 2005;Juric et al, 2005). In a prospective study of patients with diffuse large B-cell lymphoma (DLBCL), high ORP3 expression was associated with increased mortality (Ando et al, 2003).…”

The Wnt signaling pathway and mitotic regulators in the initiation and evolution of mantle cell lymphoma: Gene expression analysis

“…With regard to MCL, the 'Lymphoma and Leukemia Molecular Profiling Project (LLMPP)' demonstrated that the length of survival of MCL patients depends upon quantitative differences in progression from G1/S phase of the cell cycle (17). Sander et al also showed that a subset of MCL tumors with low levels of the long CCND1 transcript is highly proliferative and some of its related genes have homology to the group of cell cycle (G1/S) promoting E2F transcription partners (18). Indeed, there is a strong correlation between these reported genes and the 60 we identified in this study as involved in transformation (Table III), which emphasizes the importance of G1/S regulators in MCL evolution.…”