Cyclin D1 (PRAD1) alternative transcript b: full-length cDNA cloning and expression in breast cancers

D-Type Cyclins in Development and Disease

D-type cyclins encode G1/S cell cycle checkpoint proteins, which play a crucial role in defining cell cycle exit and progression. Precise control of cell cycle exit is vital during embryonic development, with defects in the pathways regulating intracellular D-type cyclins resulting in abnormal initiation of stem cell differentiation in a variety of different organ systems. Furthermore, stabilisation of D-type cyclins is observed in a wide range of disorders characterized by cellular over-proliferation, including cancers and overgrowth disorders. In this review, we will summarize and compare the roles played by each D-type cyclin during development and provide examples of how their intracellular dysregulation can be an underlying cause of disease.

Influence of cyclin D1 splicing variants expression on breast cancer chemoresistance via CDK4/CyclinD1-pRB-E2F1 pathway

Cyclin D1 (CCND1), a mediator of cell cycle control, has a G870A polymorphism which results in the formation of two splicing variants: full-length CCND1 (CCND1a) and C-terminally truncated CCND1 species (CCND1b). However, the role of CCND1a and CCND1b variants in cancer chemoresistance remains unknown. Therefore, this study aimed to explore the molecular mechanism of alternative splicing of CCND1 in breast cancer (BC) chemoresistance. To address the contribution of G870A polymorphism to the production of CCND1 variants in BC chemoresistance, we sequenced the G870A polymorphism and analysed the expressions of CCND1a and CCND1b in MCF-7 and MCF-7/ADM cells. In comparison with MCF-7 cells, MCF-7/ADM cells with the A allele could enhance alternative splicing with the increase of SC-35, upregulate the ratio of CCND1b/a at both mRNA and protein levels, and activate the CDK4/CyclinD1-pRB-E2F1 pathway. Furthermore, CCND1b expression and the downstream signalling pathway were analysed through Western blotting and cell cycle in MCF-7/ADM cells with knockdown of CCND1b. Knockdown of CCND1b downregulated the ratio of CCND1b/a, demoted cell proliferation, decelerated cell cycle progression, inhibited the CDK4/CyclinD1-pRB-E2F1 pathway and thereby decreased the chemoresistance of MCF-7/ADM cells. Finally, CCND1 G870A polymorphism, the alternative splicing of CCDN1 was detected through Sequenom Mass ARRAY platform, Sanger sequencing, semi-quantitative RT-PCR, Western blotting and immunohistochemistry in clinical BC specimens. The increase of the ratio of CCND1b/a caused by G870A polymorphism was involved in BC chemoresistance. Thus, these findings revealed that CCND1b/a ratio caused by the polymorphism is involved in BC chemoresistance via CDK4/CyclinD1-pRB-E2F1 pathway.

Association between cyclin D1 (CCND1) G870A polymorphism and gastric cancer risk: a meta-analysis

Published data on the association between cyclin D1 (CCND1) G870A polymorphism and gastric cancer (GC) risk are inconclusive. Thus, we conducted a meta-analysis to evaluate the relationship between CCND1 G870A polymorphism and GC risk. We searched PubMed, EMBASE, Web of science and the Cochrane Library up to June 12, 2015 for relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the strength of associations. Nine studies published from 2003 to 2014, with a total of 1813 cases and 2173 controls, were included in this meta-analysis. The pooled results showed that there was no association between CCND1 G870A polymorphism and GC risk in any genetic model. The subgroup analysis stratified by ethnicity showed an increased breast cancer risk in Caucasian based on heterozygote comparison (GA vs. GG: OR=1.49, 95% CI=1.06-2.10, P=0.02). We found the same association in population based (PB) stratified analyses by Source of controls (AA vs. GG: OR=1.39, 95% CI=1.01-1.93, 0.05). When stratifying by the type, Sex and H. pylori infection in dominant model, Interestingly, we found the opposite result in Male (AA + GA vs. GG: OR=0.5, 95% CI=0.33-0.76, P=0.001), there were no association between CCND1 G870A polymorphism and GC risk in any other subgroup. This meta-analysis suggests that CCND1 G870A polymorphism is a risk factor for susceptibility to GC in Caucasians and in general populations. While, CCND1 G870A polymorphism plays a possible protective effect in GC in Male. Further large scale multicenter epidemiological studies are warranted to confirm this finding.

Effect of Polymorphisms in XRCC1, CCND1 and GSTM1 and Tobacco Exposure as Risk Modifier for Oral Leukoplakia

Analysis of gene-environment interactions may help to define the risk of oral leukoplakia. We hypothesized that an individual's susceptibility to leukoplakia is dependent on interactions between polymorphic genotypes at susceptible loci and tobacco exposure. To test this hypothesis, the relationship between tobacco use and polymorphisms in 3 genes that might contribute to variance in individuals′ susceptibility to the risk of leukoplakia was determined. In this case-control study, polymorphic genotypes in XRCC1 (399Gln), a DNA repair gene involved in removing DNA adducts, CCND1 (G870A), a key component of cell cycle regulation, and GSTM1 (null genotype), a xenobiotic-metabolizing enzyme involved in the metabolism of tobacco carcinogens, were analyzed in 100 oral leukoplakia patients and age- and gender-matched controls by PCR using genomic DNA isolated from blood. The GSTM1 null genotype was associated with a 1.6-fold increased risk of developing leukoplakia. The risk conferred by the CCND1 GA+AA variant was 2.4-fold that of the GG genotype. Importantly, among non-users of tobacco, the XRCC1 (GA+AA) variant emerged as the most significant determinant of an individual's susceptibility to leukoplakia (OR=3.5). In GSTM1 null individuals, tobacco consumption increased the risk of leukoplakia 21.3 fold. Similarly, XRCC1 A allele carriers and CCND1 A allele carriers who consumed tobacco were at a significantly high risk of developing leukoplakia (OR=11.8 and 14.9, respectively). Our study provides evidence that tobacco use in individuals harboring these polymorphic genotypes elevates the risk of oral leukoplakia and warrants further studies on gene-environment interactions to define the risk of malignant transformation of leukoplakia.

Anti-oncogenic activities of cyclin D1b siRNA on human bladder cancer cells via induction of apoptosis and suppression of cancer cell stemness and invasiveness

The human cyclin D1 gene generates two major isoforms, cyclin D1a and cyclin D1b, by alternative splicing. Although cyclin D1b mRNA is hardly expressed in normal human tissues, it is detected in approximately 60% of human bladder cancer tissues and cell lines. In the present study, to assess the therapeutic ability of cyclin D1b siRNA, we investigated the anti-oncogenic effects of cyclin D1b siRNA on human bladder cancer cell lines, SBT31A and T24, which express cyclin D1b mRNA. Knockdown of cyclin D1b by specific siRNA significantly suppressed cell proliferation, in vitro cell invasiveness and three-dimensional (3D) spheroid formation in these cell lines. Cell cycle analyses revealed that cyclin D1b siRNA inhibited G1-S transition in T24 cells. The increase in the sub-G1 fraction, morphological aberrant nuclei with nuclear fragmentation and caspase-3 activity in SBA31A cells treated with cyclin D1b siRNA showed that cyclin D1b siRNA induced apoptosis. In T24 cells, knockdown of cyclin D1b suppressed the expression of the stem cell marker CD44. Knockdown of cyclin D1b or CD44 suppressed the invasiveness under 3D spheroid culture conditions and expression of N-cadherin. Tumor growth of SBT31A cells in nude mice was significantly inhibited by cyclin D1b siRNA. Taken together, these results indicate that knockdown of cyclin D1b suppresses the malignant phenotypes of human bladder cancer cells via induction of apoptosis and suppression of cancer cell stemness and epithelial-mesenchymal transition. Applying cyclin D1b siRNA will be a novel therapy for cyclin D1b-expressing bladder cancers.

Akt-dependent activation of Erk by cyclin D1b contributes to cell invasiveness and tumorigenicity

A total of two major isoforms, cyclin D1a and cyclin D1b, are generated from the human cyclin D1 gene by alternative splicing. Cyclin D1b is scarcely expressed in normal tissues; however, it is expressed at a high frequency in certain types of cancerous tissue. The present authors previously constructed cyclin D1b transgenic (Tg) mice and identified rectal tumors, including adenocarcinoma and sessile serrated adenoma, in 62.5% of female Tg mice. In addition, the present authors indicated that cyclin D1b expression enhances phosphorylation of extracellular signal-regulated kinase (Erk) in these rectal tumors, and in mouse embryonic fibroblast (MEF) cells and human 293T cells. In the present study, it was initially demonstrated that cyclin D1b has the ability to enhance cell invasiveness by itself; it additionally increases cell invasiveness, anchorage-independent growth and tumorigenicity in cooperation with an activated K-ras oncogene in MEF cells. Phosphorylation of Akt was increased in cyclin D1b-expressing MEF cells and in the rectal tumor tissues of cyclin D1b Tg mice. Phosphorylation of Akt was also enhanced by transfection of cyclin D1b, but not cyclin D1a, in human 293T cells. Treatment with an Akt inhibitor suppressed phosphorylation of Erk in 293T cells expressing cyclin D1b and D1bTgRT cells established from rectal cancer of the cyclin D1b Tg mouse. Furthermore, the Akt inhibitor suppressed the invasiveness of D1bTgRT cells and the tumor growth of these cells in nude mice when the Akt inhibitor was injected into the tumors. These results indicate that cyclin D1b activates Erk through Akt, and that activation of Akt contributes to the tumorigenicity of the cyclin D1b Tg mice. Inhibitors targeting the phosphoinositide 3-kinase/Akt signaling pathway are thus expected to have therapeutic potential in a variety of human cancer types expressing cyclin D1b.

Aberrant expression of cyclin D1 in cancer

Cyclin D1 binds and activates cyclin-dependent kinases 4/6 (Cdk4/6) to phosphorylate the retinoblastoma (RB) family proteins, relieving E2F/DPs from the negative restraint of RB proteins and histone deacetylases. The cyclin D-Cdk4/6 complexes activate cyclin E/Cdk2 through titration of the Cdk inhibitors p21^Cip1/p27^Kip1. Cyclin E/Cdk2 further phosphorylates RBs, thereby activating E2F/DPs, and cells enter the S phase of the cell cycle. Cyclin D-Cdk4/6 also phosphorylates MEP50 subunit of the protein arginine methyltransferase 5 (PRMT5), which cooperates with cyclin D1 to drive lymphomagenesis in vivo. Activated PRMPT5 causes arginine methylation of p53 to suppress expression of pro-apoptotic and anti-proliferative target genes, explaining the molecular mechanism for tumorigenesis. Cyclin D1 physically interacts with transcription factors such as estrogen receptor, androgen receptor, and Myb family proteins to regulate gene expression in Cdk-independent fashion. Dmp1 is a Myb-like protein that quenches the oncogenic signals from activated Ras or HER2 by inducing Arf/p53-dependent cell cycle arrest. Cyclin D1 binds to Dmp1α to activate both Arf and Ink4a promoters to induce cell cycle arrest or apoptosis in non-transformed cells to prevent them from neoplastic transformation. Dmp1-deficiency significantly accelerates mouse mammary tumorigenesis with reduced apoptosis and increased metastasis. Cyclin D1 interferes with ligand activation of PPARγ involved in cellular differentiation; it also physically interacts with histone deacetylases (HDACs) and p300 to repress gene expression. It has also been shown that cyclin D1 accelerates tumorigenesis through transcriptional activation of miR-17/20 and Dicer1 which, in turn, represses cyclin D1 expression. Identification of cyclin D1-binding proteins/promoters will be essential for further clarification of its biological activities.

Female-specific rectal carcinogenesis in cyclin D1b transgenic mice

Human cyclin D1 generates two major isoforms via alternative splicing: cyclin D1a and cyclin D1b. Cyclin D1b is hardly expressed in normal tissues but is frequently expressed in certain types of cancer tissues. To clarify the oncogenic potential of cyclin D1b variant, we developed cyclin D1b transgenic (Tg) mice and analyzed their phenotypes. We detected rectal tumors in 63% (15/24) of the female Tg mice. All rectal tumors had the histological characteristics similar to human sessile serrated adenoma/polyps (SSA/Ps). Adenocarcinomas were also found in 53% (8/15) of the rectal tumors, suggesting that these adenocarcinomas originated from the SSA/P-like lesions. No rectal tumors were found in the ovariectomized female cyclin D1b Tg mice (0/10), indicating that ovarian hormones played a critical role in rectal carcinogenesis in these Tg mice. Both phosphorylation of Erk, without activating MEK, and expression of estrogen receptor β were elevated in the rectal tumors of female cyclin D1b Tg mice compared with normal rectums of female wild-type mice. In addition, we established a cell line, D1bTgRT, derived from a rectal cancer of female Tg mouse. Small interfering RNA-induced cyclin D1b knockdown in this cell line suppressed Erk phosphorylation, anchorage-independent growth, cell invasiveness and tumorigenicity in nude mice. In humans, expression of cyclin D1b messenger RNA was detected in 17% (1/6) of colorectal cancer cell lines and 9.7% (3/31) of colorectal cancer tissues. Taken together, these results indicate that cyclin D1b expression contributes to the female- specific rectal carcinogenesis in mouse model.

The impact of cyclin D1 mRNA isoforms, morphology and p53 in mantle cell lymphoma: p53 alterations and blastoid morphology are strong predictors of a high proliferation index

BACKGROUND

Mantle cell lymphoma is a clinically heterogeneous disease characterized by overexpression of cyclin D1 protein. Blastoid morphology, high proliferation, and secondary genetic aberrations are markers of aggressive behavior. Expression profiling of mantle cell lymphoma revealed that predominance of the 3'UTR-deficient, short cyclin D1 mRNA isoform was associated with high cyclin D1 levels, a high "proliferation signature" and poor prognosis.

DESIGN AND METHODS

Sixty-two cases of mantle cell lymphoma were analyzed for cyclin D1 mRNA isoforms and total cyclin D1 levels by real-time reverse transcriptase polymerase chain reaction, and TP53 alterations were assessed by immunohistochemistry and molecular analysis. Results were correlated with proliferation index and clinical outcome.

RESULTS

Predominance of the short cyclin D1 mRNA was found in 14 (23%) samples, including four with complete loss of the standard transcript. TP53 alterations were found in 15 (24%) cases. Predominance of 3'UTR-deficient mRNA was significantly associated with high cyclin D1 mRNA levels (P=0.009) and more commonly found in blastoid mantle cell lymphoma (5/11, P=0.060) and cases with a proliferation index of >20% (P=0.026). Both blastoid morphology (11/11, P<0.001) and TP53 alterations (15/15, P<0.001) were significantly correlated with a high proliferation index. A proliferation index of 10% was determined to be a significant threshold for survival in multivariate analysis (P=0.01).

CONCLUSIONS

TP53 alterations are strongly associated with a high proliferation index and aggressive behavior in mantle cell lymphoma. Predominance of the 3'UTR-deficient transcript correlates with higher cyclin D1 levels and may be a secondary contributing factor to high proliferation, but failed to reach prognostic significance in this study.

Regulation of chemoresistance via alternative messenger RNA splicing

The acquisition of resistance to chemotherapy is a significant problem in the treatment of cancer, greatly increasing patient morbidity and mortality. Tumors are often sensitive to chemotherapy upon initial treatment, but repeated treatments can select for those cells that were able to survive initial therapy and have acquired cellular mechanisms to enhance their resistance to subsequent chemotherapy treatment. Many cellular mechanisms of drug resistance have been identified, most of which result from changes in gene and protein expression. While changes at the transcriptional level have been duly noted, it is primarily the post-transcriptional processing of pre-mRNA into mature mRNA that regulates the composition of the proteome and it is the proteome that actually regulates the cell's response to chemotherapeutic insult, inducing cell survival or death. During pre-mRNA processing, intronic non-protein-coding sequences are removed and protein-coding exons are spliced to form a continuous template for protein translation. Alternative splicing involves the differential inclusion or exclusion of exonic sequences into the mature transcript, generating different mRNA templates for protein production. This regulatory mechanism enables the potential to produce many different protein isoforms from the same gene. In this review I will explain the mechanism of alternative pre-mRNA splicing and look at some specific examples of how splicing factors, splicing factor kinases and alternative splicing of specific pre-mRNAs from genes have been shown to contribute to acquisition of the drug resistant phenotype.

Association between cyclin D1 polymorphism with CpG island promoter methylation status of tumor suppressor genes in gastric cancer

BACKGROUND

CpG island hypermethylation of tumor suppressor genes is highly involved in gastric carcinogenesis, and enhanced cell proliferation could accelerate this process. Cyclin D1 regulates cell cycle function and may play a role in methylation-related carcinogenesis.

AIMS

We investigated the association between Cyclin D1 gene G870A polymorphism and the methylation status of tumor suppressor genes in gastric cancer.

METHODS

Polymorphisms at G870A in the Cyclin D1 gene were genotyped, and methylation status of the p14, p16, DAP-kinase, and CDH1 genes were determined by methylation-specific-polymerase chain reaction in 139 gastric cancer tissues. CIHM high was defined as three or more methylated CpG islands.

RESULTS

Although no association was found between methylation status and different stages and Lauren's subtypes, patients with CIHM of DAP-kinase showed significantly worse survival than those without (p = 0.017). In addition, the number of methylated sites was also associated with survival curves (p = 0.0397). The 870G carrier a significantly lower prevalence of CIHM high compared to the AA genotype in advanced-stage gastric cancer (adjusted OR = 0.32, p = 0.047). A weak correlation between the same genotypes and CIHM of p14 were found in the same subtype (adjusted OR = 0.32, p = 0.052). The mean methylation number was significantly lower in G carriers than in AA genotypes in advanced-stage gastric cancer (p = 0.017).

CONCLUSIONS

Genetic polymorphism of CCND1 is associated with CIHM status in gastric cancer, especially in the advanced stage, but is independent of clinico-pathological features.

Mantle cell lymphoma shows three morphological evolutions of classical, intermediate, and aggressive forms, which occur in parallel with increased labeling index of cyclin D1 and Ki-67

Although the 2008 World Health Organization classification defines two subtypes of mantle cell lymphoma (MCL), classical and aggressive, we often encounter MCL with both features in the same site. We named this feature "MCL with focal aggressive form (intermediate MCL)". In the present study, we reclassified 237 patients with cyclin D1 (CCND1)-positive MCL on the basis of the concept of intermediate MCL, and analyzed the correlation of this reclassification with immunohistochemical detection of CCND1, Ki-67, p53, p27(Kip1), and p21(WAF/Cip1). The median overall survival was 77, 31, and 18 months for classical, intermediate, and aggressive MCL, respectively, showing a statistically significant difference (P < 0.0001). The expression levels of CCND1, Ki-67, p53, and p21(WAF/Cip1) in aggressive MCL (mean 80.1 +/- 27.8%, 73.7 +/- 28.9%, 31.0 +/- 69.0%, and 10.4 +/- 24.8%, respectively) were higher than those in classical MCL (mean 58.1 +/- 36.7%, 25.2 +/- 25.5%, 6.5 +/- 24.3%, and 2.5 +/- 13.0%, respectively) and intermediate MCL (mean 75.7 +/- 31.4%, 30.8 +/- 33.3%, 21.0 +/- 57.4%, and 4.8 +/- 16.5%, respectively). Significantly different levels of Ki-67 and p21(WAF/Cip1) were only recognized between intermediate and aggressive (P < 0.05 and P < 0.0001, respectively), whereas those of CCND1 and p53 were only between classical and intermediate (P < 0.0001 and P < 0.05, respectively). There were no significant differences in p27(Kip1) among the three groups. The subsequent discriminant analysis with independent prognostic factors clearly demonstrated that the morphological evolution of MCL occurs in parallel with increased labeling index of CCND1 and Ki-67. The diagnosis of intermediate MCL thus proved to be of major significance and should enable the design of more tailored therapies.

Identification of a human cyclin D1-derived peptide that induces human cytotoxic CD4 T cells

Cyclin D1 is over-expressed in various human tumors and therefore can be a potential oncogenic target antigen. However, only a limited number of T cell epitopes has been characterized. We aimed at identifying human cyclin D1-derived peptides that include both CD4 and CD8 T cell epitopes and to test if such multi-epitope peptides could yield improved cytotoxic CD8 T cell responses as well as cytotoxic CD4 T cells. Five HLA-DR.B1-binding peptides containing multiple overlapping CD4 epitopes and HLA-A0201-restricted CD8 T cell epitopes were predicted by computer algorithms. Immunogenicity of the synthetic peptides was assessed by stimulating T cells from healthy donors in vitro and the epitope recognition was measured by IFN-γ ELISPOT and ⁵¹Chromium release assays. A HLA-DR.B1 peptide, designed “DR-1”, in which a HLA-A0201-binding epitopes (D1-1) was imbedded, induced CD3 T cell responses against both DR-1 and D1-1 peptides in IFN-γ ELISPOT assay. This suggested processing of the shorter D1-1 epitope from the DR-1 sequence. However, only DR-1-stimulated CD4 or CD3 T cells possessed cytotoxicity against peptide-pulsed autologous DCs and a cancer cell line, that expresses a high level of cyclin D1. Monoclonal antibody to HLA-DR abrogated the epitope-specific responses of both CD3 and CD4 T cells, demonstrating class II-mediated killing. Our studies suggest a possible role of CD4 T cells in anti-tumor immunity as cytotoxic effectors against HLA-DR expressing cancers and provide a rationale for designing peptide vaccines that include CD4 epitopes.

Effect of cyclin D1 (CCND1) polymorphism on gastric premalignant condition

BACKGROUND

Cyclin D1 (CCND1) is known to regulate function in G1 arrest and therefore may play an important role in carcinogenesis. The aim of this study was to investigate the effect of G870A polymorphism of the CCND1 gene on gastric precancerous condition, on histological chronic gastritis, and on the risk of peptic ulcer diseases.

METHODS

Restriction fragment length polymorphism analysis was performed for polymorphisms at 870GA in the CCND1 gene in 524 cancer-free subjects, including 111 gastric and 54 duodenal ulcers, and 359 non-ulcer subjects. Gastritis scores of antral gastric mucosa were assessed according to the updated Sydney system in 384 subjects.

RESULTS

CCND1 genotype was significantly associated with the severity of intestinal metaplasia by the Kruskal-Wallis test, and this tendency was especially stronger among older subjects of 61 years or older (overall subjects: p=0.035, 61 years approximately : p=0.007). We also found that the 870AA genotype held a significant high risk of intestinal metaplasia [Helicobacter pylori infection adjusted odds ratio (OR)=1.8, 95% confidence interval (CI)=1.03-3.15, p=0.04]. The same genotype was more closely associated with the risk of intestinal metaplasia in older subjects of 61 years or older (H. pylori infection adjusted OR=3.45, 95% CI=1.48-8.08, p=0.004). A non-significant association was found between CCND1 G870A genotypes and the risk of peptic ulcer diseases as well as histological severity of acute or chronic inflammation.

CONCLUSIONS

It appears that the G870A polymorphism of CCND1 is associated with gastric premalignant condition especially in older subjects.

Cyclin D1b is aberrantly regulated in response to therapeutic challenge and promotes resistance to estrogen antagonists

Cyclin D1 is a key mediator of cell cycle progression that is aberrantly regulated in multiple cancers, especially in breast cancers. A number of studies have indicated that a polymorphism in a splice donor site in the cyclin D1 gene is associated with alternative splicing and the production of the alternative cyclin D1b transcript. Furthermore, this polymorphism is selectively associated with disease outcomes. However, relatively little is known regarding the protein product of the alternatively spliced message, cyclin D1b. Using antibodies specific for cyclin D1b, it was found that this protein is readily detectable in a number of cancer cell lines and primary breast cancers. Whereas cyclin D1b interacts with cyclin-dependent kinase 4 (CDK4), it is relatively inefficient at mediating RB phosphorylation and cell cycle progression in model systems due to the lack of exon 5 of cyclin D1-encoded sequences. However, cyclin D1b protein levels are not significantly attenuated by DNA damage or antiestrogen treatment, indicating that the protein may have significant effect on the response to such therapeutic modalities. Whereas enforced expression of cyclin D1b was not sufficient to abrogate DNA damage checkpoint responses, it did efficiently overcome cell cycle arrest mediated by antiestrogen therapeutics. This action of cyclin D1b was not associated with effects on estrogen receptor activity, but was rather dependent on functional association with CDK4. Combined, these studies indicate that the cyclin D1b protein is aberrantly regulated and could contribute to therapeutic failure in the context of ER-positive breast cancer.

Cyclin D1 expression is induced by viral BARF1 and is overexpressed in EBV-associated gastric cancer

Approximately 10% of gastric carcinomas (GC) worldwide are associated with Epstein-Barr virus (EBV). GC is one of the most frequent human malignancies associated with EBV. The latent expression of the EBV-oncogene BARF1 is restricted to epithelial malignancies. To investigate the underlying BARF1-related mechanisms of oncogenic epithelial transformation, we analyzed gene expression profiles of a BARF1-transfected epithelial (HaCaT+) and the corresponding BARF1-negative (HaCaT-) cell line by cDNA microarray analysis. Real-time PCR was performed to confirm the cDNA microarray results. In addition, immunohistochemistry and fluorescence in situ hybridization were performed on a tissue microarray of 181 GC including 11 EBV-associated GC. Among other genes cyclin D1 expression was significantly upregulated in HaCaT+ on the transcriptional and protein level. Cyclin D1 protein expression in GC revealed a significant overexpression of cyclin D1 in EBV-associated GC (p<0.012) but not in EBV-negative GC. Cyclin D1 FISH showed that cyclin D1 overexpression was not due to gene amplification in EBV-associated GC. Cyclin D1 is induced in HaCaT+ by BARF1 and is overexpressed in EBV-associated GC indicating an interaction of viral BARF1 and cyclin D1.

Alteration of cyclin D1 transcript elongation by a mutated transcription factor up-regulates the oncogenic D1b splice isoform in cancer

Pre-mRNA splicing and polyadenylation are tightly connected to transcription, and transcriptional stimuli and elongation dynamics can affect mRNA maturation. However, whether this regulatory mechanism has a physio/pathological impact is not known. In cancer, where splice variant expression is often deregulated, many mutated oncogenes are transcriptional regulators. In particular, the Ewing sarcoma (EwSa) oncogene, resulting from a fusion of the EWS and FLI1 genes, encodes a well characterized transcription factor. EWS-FLI1 directly stimulates transcription of the CCND1 protooncogene encoding cyclin D1a and a less abundant but more oncogenic splice isoform, D1b. We show that, although both EWS and EWS-FLI1 enhance cyclin D1 gene expression, they regulate the D1b/D1a transcript ratio in an opposite manner. Detailed analyses of RNA polymerase dynamics along the gene and of the effects of an inhibitor of elongation show that EWS-FLI1 favors D1b isoform expression by decreasing the elongation rate, whereas EWS has opposite effects. As a result, the D1b/D1a ratio is elevated in EwSa cell lines and tumors. The endogenous D1b protein is enriched in nuclei, where the oncogenic activity of cyclin D1 is known to occur, and depleting D1b in addition to D1a results in a stronger reduction of EwSa cell growth than depleting D1a only. These data show that elevated expression of a splice isoform in cancer can be due to an alteration of the transcription process by a mutated transcriptional regulator and provide evidence for a physio/pathological impact of the coupling between transcription and mRNA maturation.

Alternative cyclin D1 forms a and b have different biological functions in the cell cycle of B lymphocytes

Cyclin D1 is an important regulator of the early phase of the cell cycle and the transcriptional machinery. It is often deregulated in human tumors of various origins and is considered to be an oncogene. The CCND1 gene encoding cyclin D1 generates two mRNAs by alternative splicing, leading to the production of two alternative proteins: a long form a (36 kDa) and a short form b (30-31 kDa) from which the C-terminal moiety required for protein stability and sub-cellular localization has been deleted. Both forms of RNA and protein have been detected in B-cell hemopathies, but their respective roles are unclear. We investigated the function of cyclin D1b in cell cycle regulation, by generating B-cell lines displaying conditional expression of isoform b. Comparisons of these cell lines (BD1b series) with previously obtained cell lines expressing cyclin D1a demonstrated that cyclin D1b had no cell cycle regulatory properties.

Point mutations and genomic deletions in CCND1 create stable truncated cyclin D1 mRNAs that are associated with increased proliferation rate and shorter survival

A gene expression signature of tumor proliferation rate in mantle cell lymphoma (MCL) is an overriding molecular predictor of the length of survival following diagnosis. Many strongly proliferative MCL tumors have exceptionally high cyclin D1 mRNA levels and preferentially express short cyclin D1 mRNA isoforms. We demonstrate here that these short mRNAs are cyclin D1a isoforms with truncated 3'UTRs, not alternatively spliced cyclin D1b mRNA isoforms. Among 15 MCL tumors with truncated cyclin D1 mRNAs, 7 had genomic deletions in the CCND1 3'UTR region. In 3 others, CCND1 contained point mutations that created premature polyadenylation signals, giving rise to 1.5-kb mRNAs lacking most of the 3'UTR. Both types of genomic alteration created transcripts lacking mRNA destabilization elements present in the wild-type cyclin D1a mRNA. Premature polyadenylation due to a 3'UTR mutation also was present in the Z-138 MCL cell line, which expressed both truncated and full-length cyclin D1a mRNAs. In these cells, the half-life of the short cyclin D1a mRNA was much longer than that of the full-length mRNA. We conclude that alterations of CCND1 3'UTR structure can significantly increase its oncogenic effect and worsen the clinical course of MCL patients.

The regulation of cyclin D1 degradation: roles in cancer development and the potential for therapeutic invention

Cyclin D1 is an important regulator of cell cycle progression and can function as a transcriptionl co-regulator. The overexpression of cyclin D1 has been linked to the development and progression of cancer. Deregulated cyclin D1 degradation appears to be responsible for the increased levels of cyclin D1 in several cancers. Recent findings have identified novel mechanisms involved in the regulation of cyclin D1 stability. A number of therapeutic agents have been shown to induce cyclin D1 degradation. The therapeutic ablation of cyclin D1 may be useful for the prevention and treatment of cancer. In this review, current knowledge on the regulation of cyclin D1 degradation is discussed. Novel insights into cyclin D1 degradation are also discussed in the context of ablative therapy. A number of unresolved questions regarding the regulation of cellular cyclin D1 levels are also addressed.

Mantle Cell Lymphoma: Identifying Novel Molecular Targets in Growth and Survival Pathways

Mantle cell lymphoma (MCL) remains one of the more challenging sub-types of non-Hodgkin lymphoma. This entity, which is only approximately 10 years old, is characterized by response to many different chemotherapy regimens, though the duration of those responses remains often times quite short. Retreatment with second and third line combination regimens results in shorter and shorter durations of response, with the rapid emergence of a very drug-resistant phenotype. Despite these often frustrating clinical features, there is now a lot of new hope in managing patients with MCL. New insights into the molecular pathogenesis of MCL has revealed a plethora of new potential targets, while our continued efforts in novel targeted drug development has produced a host of agents that are already helping patients with this challenging disease. The use of proteasome inhibitors, for example, represents one example of a new strategy that has offered new hope for patients, and new opportunities for the physician treating this disease. In this review, we will put this biology into perspective, and describe how new revelations in MCL pathogenesis are leading to the identification of many exciting new drugs with promising activity.

Association of the A870G cyclin D1 gene polymorphism with genetic susceptibility to nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal cancer (NPC) is multifactorial, and the genetic background may be a crucial etiologic factor. Cyclin D1 (CCND1) is a key regulator of the cell cycle, and its altered activity is associated with the development of cancer.

METHODS

We analyzed the A870G CCND1 polymorphism by polymerase chain reaction/restriction fragment length polymorphism (PCR-RFLP) in 281 individuals, including 94 patients with NPC and 187 healthy individuals.

RESULTS

Our results indicate that individuals carrying two G alleles have a 2.17-fold increase in the risk for the development of NPC (odds ratio [OR], 2.17; 95% confidence interval [CI], 1.19-3.98; p = .016). Age-adjusted logistic regression analysis confirmed this association (adjusted odds ratio [aOR], 2.14; 95% CI, 1.14-4.04; p = .018). Multivariate analysis demonstrates an independent association between GG CCND1 genotype (aOR, 2.06), male sex (aOR, 2.66), and age at diagnosis (aOR, 2.02) regarding the development of undifferentiated NPC. The proportion of NPC cases attributable to the GG CCND1 genotype was 14.76%.

CONCLUSIONS

Our results may be important in the definition of a biologic predictive profile for the development of NPC within our population.

The cyclin D1b splice variant: an old oncogene learns new tricks

The function of cyclin D1 as a positive regulator of the cell cycle and proto-oncogene has been well established. Cyclin D1 elicits its pro-proliferative function early in G1 phase, through its ability to activate cyclin dependent kinase (CDK) 4 or 6. Active CDK4/6-cyclin D1 complexes phosphorylate substrates that are critical for modulating G1 to S phase progression, and in this manner promote cellular proliferation. Emerging data from a number of model systems revealed that cyclin D1 also holds multiple, kinase-independent cellular functions. First, cyclin D1 assists in sequestering CDK inhibitors (e.g. p27^kip1), thus bolstering late G1 CDK activity. Second, cyclin D1 is known to bind and modulate the action of several transcription factors that hold significance in human cancers. Thus, cyclin D1 impinges on several distinct pathways that govern cancer cell proliferation. Although intragenic somatic mutation of cyclin D1 in human disease is rare, cyclin D1 gene translocation, amplification and/or overexpression are frequent events in selected tumor types. Additionally, a polymorphism in the cyclin D1 locus that may affect splicing has been implicated in increased cancer risk or poor outcome. Recent functional analyses of an established cyclin D1 splice variant, cyclin D1b, revealed that the cyclin D1b isoform harbors unique activities in cancer cells. Here, we review the literature implicating cyclin D1b as a mediator of aberrant cellular proliferation in cancer. The differential roles of cyclin D1 and the cyclin D1b splice variant in prostate cancer will be also be addressed, wherein divergent functions have been linked to altered proliferative control.

Association of the cyclin D1 gene G870A polymorphism with susceptibility to sporadic renal cell carcinoma

PURPOSE

Cyclin D1 (CCND1) mRNA is alternatively spliced to produce 2 transcripts (transcript-a and transcript-b), which may be modulated by a G870A single nucleotide polymorphism at the conserved splice donor site of exon 4. Previous studies have suggested a significant association between the CCND1 genotype and the development of various cancers. We explored the possible association between this polymorphism and the onset or disease statue of sporadic renal cell carcinoma (RCC).

MATERIALS AND METHODS

The CCND1 G870A genotype was determined in 191 RCC cases and in 400 controls by polymerase chain reaction restriction length polymorphism analysis.

RESULTS

Subjects with the AA genotype were at 1.70-fold significant higher risk for RCC than those with the GG genotype (age and sex adjusted OR 1.70, 95% 95% CI 1.03 to 2.82, p = 0.039). In addition, the A allele had a gene dose effect in increasing the risk of RCC (adjusted OR 1.30, 95% CI 1.01 to 1.67, p = 0.045). For tumor stage no significant difference in genotype frequency was found (p = 0.646).

CONCLUSIONS

These data suggest that the CCND1 variant A allele may be a genetic susceptibility factor with a recessive or gene dose effect for the onset of sporadic RCC. More extensive and larger studies are required to clarify whether the CCND1 genotype is more specifically involved in the onset of a histological subset of RCC or RCC at a younger age.

Cyclin D1: polymorphism, aberrant splicing and cancer risk

The cyclin D1 proto-oncogene exercises powerful control over the mechanisms that regulate the mitotic cell cycle, and excessive cyclin D1 expression and/or activity is common in human cancers. Although somatic mutations of the cyclin D1 locus are rarely observed, mounting evidence demonstrates that a specific polymorphism of cyclin D1 (G/A870) and a protein product of a potentially related alternate splicing event (cyclin D1b) may influence cancer risk and outcome. Herein, we review the epidemiological and functional literatures that link these alterations of cyclin D1 to human tumor development and progression.

Common genetic polymorphisms and prognosis of sporadic cancers: prostate cancer as a model

To date, most molecular epidemiological studies on gene polymorphisms in cancer have focused on the risk of development and susceptibility to cancer. However, interindividual genetic variation may contribute greatly to the treatment outcome and prognosis of cancer by affecting the interaction between cancer cells and hormones, growth factors and factors influencing the tumor microenvironment. In prostate cancer, several recent molecular epidemiological studies suggested the possibility of predicting treatment outcome and prognosis using genetic polymorphisms. Candidate genes are hormone-related, oncogenes, tumor-suppressor and cell cycle-growth control-related genes, as well as genes related to immune response, inflammatory change, neovasculization, and the extracellular matrix, genes involved in drug and xenobiotic metabolism and genes involved in DNA repair and genome stability. There remain a huge number of candidate genes whose polymorphisms may affect the progression and treatment outcome of various kinds of cancer, including that of prostate cancer.

Increased risk of cervical cancer associated with cyclin D1 gene A870G polymorphism

Human papillomavirus (HPV) plays a major role in the etiology of cervical cancer. However, a complex correlation between viral and cellular genes is necessary for cell cycle control deregulation in the progression to invasive cervical cancer (ICC). Cyclin D1 (CCND1) is an important positive regulator of the G1/S phase of the cell cycle. The CCND1 gene is located at 11q13 and is often altered in human cancers. We analyzed the A870G CCND1 polymorphism by polymerase chain reaction/restriction fragment length polymorphism analysis in 246 women including 50 cases with high-grade squamous intraepithelial lesions of the cervix (HSIL), 93 with ICC, and 103 healthy women. The GG genotype was associated with a 4.32-fold higher risk for the development of HSIL [adjusted odds ratio (aOR)=4.32, 95% confidence interval (CI) 1.50-12.46, P=0.0067), and a 3.26-fold increased risk for the development of ICC (aOR=3.26, 95% CI 1.42-7.53, P=0.006). The proportion of cervical cancer cases attributable to the GG CCND1 genotype was 17.26%. This study indicates that the A870G CCND1 polymorphism could act as a cofactor of HPV in the initiation of cervical carcinogenesis, particularly in the transformation zone of HPV-infected women, supporting evidence for a genetic factor in ICC risk.

Cyclin D1 in Breast Cancer Pathogenesis

Taking a perspective on available evidence that emphasizes relevance to human disease, cyclin D1 is solidly established as an oncogene with an important pathogenetic role in breast cancer and other human tumors. However, the precise cellular mechanisms through which aberrant cyclin D1 expression drives human neoplasia are less well established. Indeed, emerging evidence suggests that cyclin D1 might act, predominantly or at least in part, through pathways that do not involve its widely accepted function as a cell cycle regulator. Although therapeutic exploitation of the role of cyclin D1 as a molecular driver of breast cancer carries great promise, it is also suggested that direct targeting of the cyclin D1 gene or gene products may prove more successful than approaches that rely on arguably incomplete knowledge of the oncogenic mechanisms of cyclin D1.

Induced expression of humanCCND1 alternative transcripts in mouseCyl-1 knockout fibroblasts highlights functional differences

Splicing of human cyclin D1 (CCND1) mRNA producing transcripts a and b is modulated by a common polymorphism (A --> G) located in a conserved splice donor region at nucleotide 870. CCND1 A/G(870) genotype is associated with tumour progression and clinical outcome in a variety of cancers. Although in vitro expression of cyclin D1 transcript a (CCND1(tra)) has been widely investigated, few studies have examined the expression of CCND1 transcript b (CCND1(trb)). We have studied the effects of inducible expression of human CCND1(trb) in comparison with human CCND1(tra) in a mouse fibroblast knock-out for cyclin D1 (MEF(Cyl-1-/-)). Inducible expression was in stable clones isolated from MEF(Cyl-1-/-) transfectants. Induction of CCND1(tra) produced a 36-kDa protein, which led to a significant increase in the proportion of cells in S-phase, as detected by BrdU incorporation after 32 hr, compared to non-induced cells (p = 0.012). Clones induced to express CCND1(tra) exhibited a significantly increased ability to grow in serum depleted (2% FCS) medium compared to non-induced clones (p = 0.0004). Induced expression of CCND1(trb) in MEF(Cyl-1-/-) transfectants produced a 31-kDa protein and resulted in no significant difference in DNA synthesis, neither did the cells acquire the ability to grow in serum-depleted conditions compared to non-induced cells. Induction of CCND1(trb) significantly enhanced the ability of MEF(Cyl-1-/-) transfectants to form colonies in soft agar, (average 30-fold increase) compared to non-induced clones or those induced to express CCND1(tra). Our data supports the emerging view that CCND1 alternate transcripts encode proteins with differing independent biological functions. We suggest that CCND1(tra) encodes a protein involved in regulating mitogen responsive, anchorage-dependent G(1) progression, whereas CCND1(trb) modulates the ability of the cell to grow in an anchorage-independent manner.

Polymorphism within the cyclin D1 gene is associated with an increased risk of carcinoma in situ in patients with superficial bladder cancer

OBJECTIVES

To evaluate the prognostic value of CCND1 polymorphism in superficial and invasive transitional cell cancer of the bladder.

METHODS

CCND1 polymorphism of blood DNA from patients with transitional cell cancer of the bladder was evaluated using the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

No statistically significant difference was found in the recurrence-free survival of patients with superficial (pTa-T1) transitional cell cancer after transurethral resection among different genotype groups (AA versus GG, P = 0.746; GA versus GG, P = 0.979). In patients with superficial bladder cancer, the occurrence of primary carcinoma in situ was significantly greater in patients with the AA genotype compared with those with the GA or GG genotypes (P = 0.006, chi-square test). No statistically significant difference was found in disease-specific survival after radical cystectomy among the different genotype subgroups (AA versus GG, P = 0.245; GA versus GG, P = 0.649).

CONCLUSIONS

Although CCND1 polymorphism is not able to serve as a prognostic marker for bladder cancer, the CCND1 variant A allele may recessively increase the risk of carcinoma in situ incidence in patients with superficial bladder cancer.

αCP-4, Encoded by a Putative Tumor Suppressor Gene at 3p21, But Not Its Alternative Splice Variant αCP-4a, Is Underexpressed in Lung Cancer

alpha CP-4 is an RNA-binding protein coded by PCBP4, a gene mapped to 3p21, a common deleted region in lung cancer. In this study we characterized the expression of alpha CP-4 and alpha CP-4a, an alternatively spliced variant of alpha CP-4, in lung cancer cell lines and non-small cell lung cancer (NSCLC) samples from early stage lung cancer patients. In NSCLC biopsies, an immunocytochemical analysis showed cytoplasmic expression of alpha CP-4 and alpha CP-4a in normal lung bronchiolar epithelium. In contrast, alpha CP-4 immunoreactivity was not found in 47% adenocarcinomas and 83% squamous cell carcinomas, whereas all of the tumors expressed alpha CP-4a. Besides, lack of alpha CP-4 expression was associated with high proliferation of the tumor (determined by Ki67 expression). By fluorescence in situ hybridization, >30% of NSCLC cell lines and tumors showed allelic losses at PCBP4, correlating with the absence of the protein. On the other hand, no mutations in the coding region of the gene were found in any of the 24 cell lines analyzed. By Northern blotting and real-time reverse transcription-PCR, we detected the expression of alpha CP-4 and alpha CP-4a messages in NSCLC and small cell lung cancer cell lines. Our data demonstrate an abnormal expression of alpha CP-4 in lung cancer, possibly associated with an altered processing of the alpha CP-4 mRNA leading to a predominant expression of alpha CP-4a. This may be considered as an example of alternative splicing involved in tumor suppressor gene inactivation. Finally, induction of alpha CP-4 expression reduced cell growth, in agreement with its proposed role as a tumor suppressor, and suggesting an association of this RNA-binding protein with lung carcinogenesis.

Association of cyclin D1 (G870A) polymorphism with susceptibility to esophageal and gastric cardiac carcinoma in a northern Chinese population

Our aim was to investigate the association of cyclin D1 (G870A) single nucleotide polymorphism with susceptibility to esophageal and cardiac carcinoma in a northern Chinese population. By polymerase chain reaction-single strand conformation polymorphism analysis, cyclin D1 (G870A) genotyping was carried out among 120 patients with esophageal squamous cell carcinoma (ESCC), 87 patients with gastric cardiac adenocarcinoma (CAC), and 183 age- and gender-matched controls. The cyclin D1 genotype distribution among ESCC patients was significantly different from that among healthy controls (chi(2) = 7.372, p = 0.025). The G/G genotype was significantly less frequent among ESCC patients (9.2%) than among healthy controls (20.8%) (chi(2) = 7.192, p = 0.007). The G/G genotype significantly reduced risk for the development of ESCC compared to the combination of G/A and A/A genotypes (adjusted odds ratio [OR] = 0.37, 95% confidence interval [CI] = 0.16-0.83). After stratification according to smoking status, the A/A frequency among smoking ESCC (34.3%) and CAC patients (35.7%) was significantly higher than that among smoking healthy controls (18.6%) (chi(2) = 5.426 and 5.599, p = 0.020 and 0.018, respectively). Smokers with the A/A genotype had an about 2-fold increased risk for both of ESCC and CAC compared to the G/A and G/G genotypes, with an adjusted OR of 2.26 in ESCC (95% CI = 1.14-4.49) and of 2.42 in CAC (95% CI = 1.17-4.98). No correlation between the cyclin D1 genotype and development of ESCC or CAC was found among nonsmokers. Determination of the cyclin D1 (G870A) single nucleotide polymorphism may be suitable to identify individuals with increased risk for ESCC or CAC in the northern Chinese population.

Cyclin D1 genotype, response to biochemoprevention, and progression rate to upper aerodigestive tract cancer

BACKGROUND

Altered cyclin D1 expression in advanced preinvasive lesions of the upper aerodigestive tract (UADT) is associated with an increased risk of developing cancer and histologic progression during and after combination biochemopreventive therapy (13-cis-retinoic acid, alpha-interferon, and alpha-tocopherol). Both alleles of the adenine (A)/guanine (G) cyclin D1 polymorphism located at nucleotide 870 encode two alternatively spliced transcripts, but the A allele preferentially encodes a protein with an extended half-life. We investigated whether the cyclin D1 genotype at nucleotide 870 was associated with baseline levels of cyclin D1 protein, post-treatment modulation of cyclin D1 protein levels, histologic response to treatment, and the outcome for subjects with preinvasive UADT lesions after biochemopreventive therapy.

METHODS

UADT tissue biopsy samples were obtained before and 6 and 12 months after biochemopreventive treatment from 31 individuals with advanced preinvasive UADT lesions. Tissues were examined for cyclin D1 genotype (by DNA single-strand conformation polymorphism analysis), for cyclin D1 protein expression (by immunohistochemistry), and for cyclin D1 gene copy number (by fluorescence in situ hybridization). Associations of cyclin D1 genotype with histologic response to therapy and time to progression to a higher degree of dysplasia or invasive cancer were investigated. All statistical tests were two-sided.

RESULTS

The A allele was associated with increased baseline cyclin D1 expression in the parabasal epithelial layer (16 of 18 AA/AG subjects versus four of nine GG subjects; P =.02), decreased histologic response to biochemopreventive treatment (six of 21 AA/AG subjects versus four of 10 GG subjects; P =.70), decreased favorable modulation of cyclin D1 expression by the treatment (seven of 18 AA/AG subjects versus eight of nine GG subjects; P =.02), and shorter progression-free survival (P =.05).

CONCLUSIONS

The cyclin D1 A allele was associated with a diminished modulation of normal physiologic and treatment-induced decreased expression of cyclin D1, a decreased likelihood of response to biochemopreventive intervention, and an increased rate of progression to cancer development, findings that require validation in a larger cohort.

Increased risk of prostate cancer associated with AA genotype of cyclin D1 gene A870G polymorphism

CCND1 mRNA is alternatively spliced to produce 2 transcripts, and the splicing pattern may be modulated by a frequent A870G single-nucleotide polymorphism within the conserved splice donor site of exon 4. Several studies have suggested a significant association between the CCND1 genotype and onset or progression of various cancers. To investigate the correlation of the polymorphism with genetic susceptibility to PCa and its disease status, we examined the polymorphism in 214 cases of PCa, 234 cases of BPH and 254 male controls. The CCND1 A allele was more frequently observed in the PCa group (p = 0.015) and the BPH group (p = 0.018) than the control group. Men with the AA genotype had an increased risk of PCa (aOR = 1.93, 95% CI 1.13-3.30, p = 0.016) and BPH (aOR = 1.84, 95% CI 1.09-3.09, p = 0.023) compared to those with the GG genotype. No significant association was observed when men with the AG genotype were compared to those with the GG genotype (PCa: aOR = 1.00, 95% CI 0.65-1.54, BPH: aOR = 0.91, 95% CI 0.60-1.39). The risk of PCa associated with the AA genotype appeared to be stronger in men aged 73 years or younger (aOR = 2.89, 95% CI 1.38-6.01, p = 0.005), whereas no association was found in men older than 73 years (aOR = 1.02, 95% CI 0.44-2.34). No significant difference in genotype frequency was found among patients with low-, intermediate- and high-grade tumors (p = 0.730) or between patients with localized and metastatic PCa (p = 0.679). However, in patients with high-grade or metastatic PCa, a significantly increased risk associated with the AA genotype compared to controls was observed, while no significant results were found in those with low/intermediate or localized PCa. The A allele of the CCND1 A870G polymorphism was recessively associated with susceptibility to PCa and BPH in a Japanese population, giving a 2-fold increased risk of PCa and BPH in men with the AA genotype compared to those with the GG genotype. Although the risk of PCa associated with the AA genotype appeared to contribute especially to men aged 73 years or younger and the A allele may be associated with disease status of PCa, these conjectures require validation in future studies on a larger number of subjects.

Cyclin D1 gene polymorphism is associated with an increased risk of urinary bladder cancer

Cyclin D1 is believed to play an important role in the genesis and/or progression of transitional cell cancer (TCC) of the urinary bladder. Cyclin D1 gene (CCND1) mRNA is alternatively spliced to produce two transcripts, and the splicing pattern may be modulated by a G to A single nucleotide polymorphism within the splice donor site of exon 4. This study was conducted to explore the association between the polymorphism and the susceptibility to and disease status of TCC of the bladder in 222 cases and 317 native Japanese controls. The relationship between the CCND1 polymorphism and the mRNA splicing pattern in TCC cells was evaluated by semi-quantitative reverse-transcription PCR. The CCND1 A allele was more frequently observed in the TCC group than the control group (P = 0.032) with a significant difference in the genotype frequency between the two groups (P = 0.029). The AA genotype was associated with a significantly higher risk of TCC compared with the AG+GG genotypes (adjusted odds ratio (aOR) = 1.76, 95% confidence interval (CI) = 1.09-2.84, P = 0.022). This association was observed more significantly in nonsmoking cases (aOR = 2.53; 95% CI = 1.28-4.51, P = 0.008). Looking at tumor grade, the presence of the A allele was associated with higher grade (= grade 3) tumors with a gene dosage effect (aOR = 1.77, CI = 1.16-2.69, P = 0.008). In tumor stage, although not significant, the AA + AG genotypes tended to be more frequently observed in cases with T1-4 tumors than those with Ta tumors (aOR = 1.94, 95% CI = 0.98-3.82, P = 0.057). The genotype seemed to influence the two alternatively spliced forms of the CCND1 mRNA because the ratio of the CCND1 transcript-b/transcript-a was significantly higher in cases with the AA genotype compared with those with the AG + GG genotypes. These data suggest that the CCND1 variant A allele may be associated with an increased risk of TCC of the bladder, especially in men without a history of smoking, and it may also have an effect on its disease status.

The EWS/NOR1 fusion gene product gains a novel activity affecting pre-mRNA splicing

In extraskeletal myxoid chondrosarcoma, chromosomal translocation creates a gene fusion between EWS and the orphan nuclear receptor NOR1. The resulting fusion gene product, EWS/NOR1, has been believed to lead to malignant transformation by functioning as a transcriptional activator, but an alternative mechanism may also be involved. Here, using a newly developed functional complementation screening in yeast, we found that EWS/NOR1, but not EWS or NOR1, complemented the loss of function of the small nuclear ribonucleoprotein Snu23p, an essential factor for pre-mRNA splicing in yeast. To verify the potential function of EWS/NOR1 in mammalian cells, we next showed that overexpression of EWS/NOR1 caused increased usage of the distal 5'-splice site of pre-mRNA splicing and that EWS/NOR1 interacted with the human splicing protein U1C; neither EWS nor NOR1 had the same activity or interaction as EWS/NOR1. Altogether, our findings reveal that EWS/NOR1 gains a novel activity affecting pre-mRNA splicing.

Binding of a SART3 tumor-rejection antigen to a pre-mRNA splicing factor RNPS1: a possible regulation of splicing by a complex formation

We recently reported the identification of a human SART3 gene that encodes a tumor-rejection antigen recognized by cytotoxic T lymphocytes (CTLs). The squamous-cell carcinoma antigen recognized by T cells-3 (SART3) is an RNA-binding protein expressed in the nucleus of the majority of proliferating cells, including normal cells and malignant cells, but not in normal tissues except for the testes and fetal liver. To determine its biologic function, we employed a 2-hybrid screening in yeast for proteins interacting with SART3, and this method yielded a pre-mRNA splicing factor (RNA-binding protein prevalent during the S phase or RNA-binding protein with a serine-rich domain [RNPS1]) that activated both constitutive and alternative splicing of pre-mRNA in vitro. Interaction of SART3 with RNPS1 through the physical association of N-terminal domains of RNPS1 was confirmed by both in vitro pull-down assay and immunoprecipitation assay. Cotransfection of the 2 genes changed the distribution pattern of SART3 from diffuse nucleoplasmic spreading to nuclear speckled regions in which the RNPS1 was colocalized, suggesting a complex formation of the 2 proteins. In cooperation with RNPS1, SART3 stimulated the proximal alternative 3' splicing of a calcitonin-dihydrofolate reductase chimeric minigene pre-mRNA. These results suggest that SART3 is involved in the regulation of mRNA splicing probably via its complex formation with RNPS1.

EWS/FLI alters 5'-splice site selection

The chimeric gene EWS/FLI is present in at least 85% of Ewing's sarcomas as a result of chromosomal translocations. The resulting fusion protein contains the N terminus of the RNA-binding protein EWS and the ETS DNA-binding domain of the transcription factor FLI-1. Although EWS/FLI binds DNA and activates transcription, both EWS and EWS/FLI also interact with SF1 and U1C, essential components of the splicing machinery. Therefore, we tested the ability of EWS and EWS/FLI to alter 5'-splice site selection using an E1A gene in vivo splicing assay. We found that EWS/FLI, but not EWS, interfered with heterogeneous nuclear ribonucleoprotein A1-dependent splice site selection of E1A. Mutational analysis of EWS/FLI revealed that the ability to affect pre-mRNA splicing coincided with transforming activity. Therefore, EWS/FLI has the ability to influence splicing as well as transcription.

The splicing factor U1C represses EWS/FLI-mediated transactivation

EWS is an RNA-binding protein involved in human tumor-specific chromosomal translocations. In approximately 85% of Ewing's sarcomas, such translocations give rise to the chimeric gene EWS/FLI. In the resulting fusion protein, the RNA binding domains from the C terminus of EWS are replaced by the DNA-binding domain of the ETS protein FLI-1. EWS/FLI can function as a transcription factor with the same DNA binding specificity as FLI-1. EWS and EWS/FLI can associate with the RNA polymerase II holoenzyme as well as with SF1, an essential splicing factor. Here we report that U1C, one of three human U1 small nuclear ribonucleoprotein-specific proteins, interacts in vitro and in vivo with both EWS and EWS/FLI. U1C interacts with other splicing factors and is important in the early stages of spliceosome formation. Importantly, co-expression of U1C represses EWS/FLI-mediated transactivation, demonstrating that this interaction can have functional ramifications. Our findings demonstrate that U1C, a well characterized splicing protein, can also function in transcriptional regulation. Furthermore, they suggest that EWS and EWS/FLI may function both in transcriptional and post-transcriptional processes.

Differential expression of the splicing regulatory factor genes during two-step chemical transformation in a BALB/3T3-derived cell line, MT-5

Although the alternative splicing of various genes is a common event in human tumors, the mechanisms behind it have not been characterized. We hypothesized that the expression of splicing regulatory factors would be changed during cellular transformation. Gene expression of three splicing regulatory factors, alternative splicing factor/splicing factor 2 (ASF/SF2), heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2) and the 65 kDa subunit of U2 small nuclear ribonucleoprotein particles auxiliary factor (U2AF(65)), were examined by northern blotting in a two-step chemical transformation model. This in vitro model is composed of BALB/3T3 cells and a BALB/3T3-derived N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-initiated cell line (MT-5). MT-5 cells can be transformed on exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA). ASF/SF2 mRNA levels were decreased 2-fold in both MNNG-initiated cells and TPA-induced transformed cells compared with the normal parental cells, whereas hnRNP A2 mRNA expression did not significantly change between these three types of cells. U2AF(65) mRNA levels were markedly increased ( approximately 4.7-fold) associated with progression of cellular transformation. Moreover, RT-PCR analysis showed that distinct forms of ASF/SF2 mRNA were present in the MNNG-initiated cells and TPA-induced transformed cells but not in the parental cells. These findings indicate that ASF/SF2 or U2AF(65) gene expression is altered during in vitro two-step chemical transformation. The data suggest that the differential expression of splicing regulatory factors is one cause of aberrant expression of alternatively spliced mRNAs encoded by various genes in tumor cells.

Cyclin-D1 expression in human renal-cell carcinoma

Cyclin-D1 over-expression represents one of several common alterations in the G1-S transition associated with malignancies. Conclusive evidences indicate that cyclin D1 is a proto-oncogene and the gene is amplified or rearranged in different tumour types. Since very little is known about aberrations in the G1-S transition in human renal-cell carcinoma (RCC), we have characterized the expression of cyclin D1 in 80 human renal-cell carcinomas and 12 normal kidney cortex tissues using Western blotting. The cyclin-D1-protein content varied considerably and 75% of the tumours expressed higher levels than normal kidney cortex, in contrast to 25% of the tumours either lacking cyclin D1 or with low protein levels. Although it is difficult to define aberrant expression of cyclin D1, the results might indicate that the proto-oncogene was activated in a sub-set of RCC. It is also possible that low expression of cyclin D1 represents an aberrant down-regulation of the protein. Immunohistochemical assessment of cyclin D1 in a sub-set of the tumours showed large variations in the fraction of cyclin-D1-positive cells, supporting the Western-blot analyses. Surprisingly, cyclin-D1 expression did not correlate with proliferation determined by Ki-67-antigen expression or S-phase analyses. In non-papillary renal-cell carcinomas, high cyclin-D1 expression was associated with a diploid DNA profile and smaller tumour size, but there was no association between cyclin-D1 expression and tumour stage or nuclear grade. In nonpapillary tumours, high cyclin-D1 expression was further significantly associated with a better prognosis according to univariate and multivariate analyses (p = 0.005 and 0.002 respectively), as compared with highly aggressive tumours with low cyclin-D1 levels.

Cyclin D1/PRAD1/BCL-1 alternative transcript [B] protein product in B-lymphoid malignancies with t(11;14)(q13;q32) translocation

The cyclin-D1/PRAD1 oncogene, a key regulator of the G1-phase progression of the cell cycle, has been identified as the long-sought BCL-1 oncogene in B-cell malignancies with t(11;14)(q13;q32) translocation. A novel alternative spliced cyclin-D1 transcript, called transcript[b], has been identified. The level of the variant transcript[b] was lower than that of the originally reported cyclin-D1 transcript, called transcript[a], in several human non-lymphoid cancer cell lines but the endogenous cellular expression of transcript[b] products has not yet been determined. Northern-blot analysis and reverse-transcription-polymerase-chain-reaction (RT-PCR) analysis revealed that transcript[b] mRNA is well expressed in B-lymphoid cell lines with t(11;14)(q13;q32) translocation and at much lower or undetectable levels in other cells. Western-blot analysis using a human cyclin-D1-specific monoclonal antibody, which can recognize and distinguish the products of transcripts [a] and [b], strongly suggested that the transcript [b] protein is indeed expressed in these B-cell lines. The present study provides identification of the endogenous cellular expression of the cyclin-D1-transcript[b] protein and strongly suggests that this alternative form of cyclin D1 may play a significant role in the molecular pathogenesis of B-lymphoid malignancies with t(11;14)(q13;q32) translocation.

A small deletion in the 3'-untranslated region of the cyclin D1/PRAD1/bcl-1 oncogene in a patient with chronic lymphocytic leukemia

The cyclin DI/PRAD1 oncogene, a key regulator of the G1 phase of the cell cycle, has been incriminated in the pathogenesis of human neoplasia. Cyclin D1 was also demonstrated to be identical to the long-sought bcl-1 oncogene in B-cell malignancies with the t(11;14)(q13;q32) translocation. We report here a small deletion in the 3'-untranslated portion of the cyclin D1 gene in leukemia cells of a patient diagnosed with B-chronic lymphocytic leukemia (CLL), associated with overexpression of the corresponding cyclin D1 mRNA. During a Northern blot survey of B-cell malignancies, we identified a patient whose CLL cells showed a marked increase in 1.5-1.6 kb cyclin D1 mRNA species. Subsequent Southern blot analysis showed that genomic DNA from the patient's cells contained an extra band in the EcoRI digest, suggesting that one allele of the cyclin D1 gene may be altered. Polymerase chain reaction (PCR) analysis of the genomic DNA and direct DNA sequencing clearly disclosed that one allele of the cyclin D1 gene was deleted in the 3'-untranslated region, which would contribute to an increased stability of its mRNA. Reverse transcription-polymerase chain reaction (RT-PCR) analysis and direct DNA sequencing revealed that the cyclin D1 mRNA was deleted at the corresponding region. This finding provides further evidence for a critical role of cyclin D1 in the pathogenesis of B-cell malignancies and highlights a novel mechanism, a small deletion in the 3'-untranslated region, responsible for deregulation of the cyclin D1 gene in oncogenesis.