Absence of cyclin D1/PRAD1 point mutations in human breast cancers and parathyroid adenomas and identification of a new cyclin D1 gene polymorphism

Molecular analysis of cyclin D1 modulators PRKN and FBX4 as candidate tumor suppressors in sporadic parathyroid adenomas

OBJECTIVE

Primary hyperparathyroidism is most often caused by a sporadic single-gland parathyroid adenoma (PTA), a tumor type for which cyclin D1 is the only known and experimentally validated oncoprotein. However, the molecular origins of its frequent overexpression have remained mostly elusive. In this study, we explored a potential tumorigenic mechanism that could increase cyclin D1 stability through a defect in molecules responsible for its degradation.

METHODS

We examined two tumor suppressor genes known to modulate cyclin D1 ubiquitination, PRKN and FBXO4 (FBX4), for evidence of classic two-hit tumor suppressor inactivation within a cohort of 82 PTA cases. We examined the cohort for intragenic inactivating and splice site mutations by Sanger sequencing and for locus-associated loss of heterozygosity (LOH) by microsatellite analysis.

RESULTS

We identified no evidence of bi-allelic tumor suppressor inactivation of PRKN or FBXO4 via inactivating mutation or splice site perturbation, neither in combination with nor independent of LOH. Among the 82 cases, we encountered previously documented benign single nucleotide polymorphisms (SNPs) in 35 tumors at frequencies similar to those reported in the germlines of the general population. Eight cases exhibited intragenic LOH at the PRKN locus, in some cases extending to cover at least an additional 1.7 Mb of chromosome 6q25-26. FBXO4 was not affected by LOH.

CONCLUSION

The absence of evidence for specific bi-allelic inactivation in PRKN and FBXO4 in this sizeable cohort suggests that these genes only rarely, if ever, serve as classic driver tumor suppressors responsible for the growth of PTAs.

Clinical and Molecular Genetics of Primary Hyperparathyroidism

Calcium homeostasis is maintained by the actions of the parathyroid glands, which release parathyroid hormone into the systemic circulation as necessary to maintain the serum calcium concentration within a tight physiologic range. Excessive secretion of parathyroid hormone from one or more neoplastic parathyroid glands, however, causes the metabolic disease primary hyperparathyroidism (HPT) typically associated with hypercalcemia. Although the majority of cases of HPT are sporadic, it can present in the context of a familial syndrome. Mutations in the tumor suppressor genes discovered by the study of such families are now recognized to be pathogenic for many sporadic parathyroid tumors. Inherited and somatic mutations of proto-oncogenes causing parathyroid neoplasia are also known. Future investigation of somatic changes in parathyroid tumor DNA and the study of kindreds with HPT yet lacking germline mutation in the set of genes known to predispose to HPT represent two avenues likely to unmask additional novel genes relevant to parathyroid neoplasia.

Clinical significance of the histological and molecular characteristics of ependymal tumors: a single institution case series from China

BACKGROUND

Ependymal tumors are pathologically defined intrinsic neoplasms originating in the intracranial compartments or the spinal cord that affect both children and adults. The recently integrated classification of ependymomas based on both histological and molecular characteristics is capable of subgrouping patients with various prognoses. However, the application of histological and molecular markers in Chinese patients with ependymomas has rarely been reported. We aimed to demonstrate the significance of histological characteristics, the v-relavian reticuloendotheliosis viral oncogene homolog A (RELA) fusions and other molecular features in ependymal tumors.

METHODS

We reviewed the histological characteristics of ependymal tumors using conventional pathological slides and investigate the RELA fusions and Cylclin D1 (CCND1) amplification by Fluorescence in situ hybridization (FISH) and trimethylation of histone 3 lysine 27 (H3K27me3) expression by immunohistochemistry (IHC) methods. SPSS software was used to analyze the data.

RESULTS

We demonstrated that hypercellularity, atypia, microvascular proliferation, necrosis, mitosis, and an elevated Ki-67 index, were tightly associated with an advanced tumor grade. Tumor location, necrosis, mitosis and the Ki-67 index were related to the survival of the ependymomas, but Ki67 was the only independent prognostic factor. Additionally, RELA fusions, mostly presented in pediatric grade III intracranial ependymomas, indicated decreased survival times of patients, and closely related to the patients' age, tumor grade, cellularity, cellular atypia, necrosis and Ki67 index in the intracranial ependymal tumors, whereas reduction of H3K27me3 predicted the worse prognosis in ependymal tumors.

CONCLUSIONS

Histological and molecular features facilitate tumor grading and prognostic predictions for ependymal tumors in Chinese patients.

Genetics of Hyperparathyroidism, Including Parathyroid Cancer

Primary hyperparathyroidism (HPT) is a metabolic disease caused by the excessive secretion of parathyroid hormone from 1 or more neoplastic parathyroid glands. HPT is largely sporadic, but it can be associated with a familial syndrome. The study of such families led to the discovery of tumor suppressor genes whose loss of function is now recognized to underlie the development of many sporadic parathyroid tumors. Heritable and acquired oncogenes causing parathyroid neoplasia are also known. Studies of somatic changes in parathyroid tumor DNA and investigation of kindreds with unexplained familial HPT promise to unmask more genes relevant to parathyroid neoplasia.

Androgen Receptor-Mediated Growth Suppression of HPr-1AR and PC3-Lenti-AR Prostate Epithelial Cells

The androgen receptor (AR) mediates the developmental, physiologic, and pathologic effects of androgens including 5α-dihydrotestosterone (DHT). However, the mechanisms whereby AR regulates growth suppression and differentiation of luminal epithelial cells in the prostate gland and proliferation of malignant versions of these cells are not well understood, though they are central to prostate development, homeostasis, and neoplasia. Here, we identify androgen-responsive genes that restrain cell cycle progression and proliferation of human prostate epithelial cell lines (HPr-1AR and PC3-Lenti-AR), and we investigate the mechanisms through which AR regulates their expression. DHT inhibited proliferation of HPr-1AR and PC3-Lenti-AR, and cell cycle analysis revealed a prolonged G₁ interval. In the cell cycle, the G₁/S-phase transition is initiated by the activity of cyclin D and cyclin-dependent kinase (CDK) complexes, which relieve growth suppression. In HPr-1AR, cyclin D1/2 and CDK4/6 mRNAs were androgen-repressed, whereas CDK inhibitor, CDKN1A, mRNA was androgen-induced. The regulation of these transcripts was AR-dependent, and involved multiple mechanisms. Similar AR-mediated down-regulation of CDK4/6 mRNAs and up-regulation of CDKN1A mRNA occurred in PC3-Lenti-AR. Further, CDK4/6 overexpression suppressed DHT-inhibited cell cycle progression and proliferation of HPr-1AR and PC3-Lenti-AR, whereas CDKN1A overexpression induced cell cycle arrest. We therefore propose that AR-mediated growth suppression of HPr-1AR involves cyclin D1 mRNA decay, transcriptional repression of cyclin D2 and CDK4/6, and transcriptional activation of CDKN1A, which serve to decrease CDK4/6 activity. AR-mediated inhibition of PC3-Lenti-AR proliferation occurs through a similar mechanism, albeit without down-regulation of cyclin D. Our findings provide insight into AR-mediated regulation of prostate epithelial cell proliferation.

Gene polymorphisms in the folate metabolism and their association with MTX-related adverse events in the treatment of ALL

The antifolate drug methotrexate (MTX) is widely used in the treatment of various neoplastic diseases, including acute lymphoblastic leukemia (ALL). MTX significantly increases cure rates and improves patients' prognosis. Despite that it achieved remarkable clinical success, a large number of patients still suffer from treatment toxicities or side effects. Even to this date, chemotherapeutic regiments have not been personalized because of interindividual differences that affect MTX response, especially polymorphisms in key genes. The pharmacological pathway of MTX in cells is useful to identify gene polymorphisms that influence the process of treatment. The aim of this review was to discuss the gene polymorphisms of drug-metabolizing enzymes in the MTX pathway and their toxicities on ALL treatment.

Animal models of hyperfunctioning parathyroid diseases for drug development

BACKGROUND

Disorders of mineral and bone metabolism have been implicated as a risk factor in the high mortality in patients with chronic kidney disease (CKD). Hyperphosphatemia, disorders of vitamin D metabolism and secondary hyperparathyroidism of uremia (SHPT) are therapeutic targets in these patients to improve the mortality. Animal models for CKD are indispensable and uremic rats produced by 5/6-nephrectomies are one of the most useful animal models for the development of new therapeutic agents. As there are limitations of uremic rats such as short lifespan and less severity of secondary hyperparathyroidism distinct from CKD patients on maintenance hemodialysis, the development of new model animals is expected.

OBJECTIVE

This review discusses the molecular pathogenesis of hyperfunctioning parathyroid diseases and the applications of animal models exhibiting hyperparathyroidisms in the aspect of the development of new therapeutics.

CONCLUSION

PTH-cyclin D1 transgenic mice, with parathyroid-targeted overexpression of cyclin D1 oncogene, not only developed abnormal parathyroid cell proliferation but, notably, also developed biochemical hyperparathyroidism with characteristic abnormalities in bone. The mice exhibit age-dependent development of biochemical hyperparathyroidism, which enables testing of the drug precisely. In addition, the mice develop parathyroid cell hyperplasia, followed by monoclonal expansion, which is observed in refractory SHPT patients.

Clinical and molecular genetics of parathyroid neoplasms

Primary hyperparathyroidism (HPT) results from the excessive secretion of parathyroid hormone from parathyroid tumours. While most HPT is sporadic, it is associated with a familial syndrome in a minority of cases. The study of these syndromes has helped define the pathophysiology of both familial and sporadic parathyroid neoplasms. Investigation of kindred with multiple endocrine neoplasia type 1 (MEN1) and the hyperparathyroidism-jaw tumour syndrome (HPT-JT) led to the discovery of the tumour suppressor genes MEN1 and HRPT2. We now recognise that somatic mutations in MEN1 and HRPT2 tumour suppressor genes are frequent events in sporadic parathyroid adenomas and carcinomas, respectively. Parathyroid tumours in the MEN2A syndrome result from mutational activation of the RET oncogene. The CCND1/PRAD1 oncogene was discovered by analysis of sporadic parathyroid tumours. Studies of familial isolated HPT and analysis of chromosomal loss and gain in parathyroid tumours suggest that other genes relevant to parathyroid neoplasia await identification.

Identification of ASF/SF2 as a critical, allele-specific effector of the cyclin D1b oncogene

The cyclin D1b oncogene arises from alternative splicing of the CCND1 transcript, and harbors markedly enhanced oncogenic functions not shared by full-length cyclin D1 (cyclin D1a). Recent studies showed that cyclin D1b is selectively induced in a subset of tissues as a function of tumorigenesis; however, the underlying mechanism(s) that control tumor-specific cyclin D1b induction remain unsolved. Here, we identify the RNA-binding protein ASF/SF2 as a critical, allele-specific, disease-relevant effector of cyclin D1b production. Initially, it was observed that SF2 associates with cyclin D1b mRNA (transcript-b) in minigene analyses and with endogenous transcript in prostate cancer (PCa) cells. SF2 association was altered by the CCND1 G/A870 polymorphism, which resides in the splice donor site controlling transcript-b production. This finding was significant, as the A870 allele promotes cyclin D1b in benign prostate tissue, but in primary PCa, cyclin D1b production is independent of A870 status. Data herein provide a basis for this disparity, as tumor-associated induction of SF2 predominantly results in binding to and accumulation of G870-derived transcript-b. Finally, the relevance of SF2 function was established, as SF2 strongly correlated with cyclin D1b (but not cyclin D1a) in human PCa. Together, these studies identify a novel mechanism by which cyclin D1b is induced in cancer, and reveal significant evidence of a factor that cooperates with a risk-associated polymorphism to alter cyclin D1 isoform production. Identification of SF2 as a disease-relevant effector of cyclin D1b provides a basis for future studies designed to suppress the oncogenic alternative splicing event.

Cyclin D1 splice variants: polymorphism, risk, and isoform-specific regulation in prostate cancer

PURPOSE

Alternative CCND1 splicing results in cyclin D1b, which has specialized, protumorigenic functions in prostate not shared by the cyclin D1a (full length) isoform. Here, the frequency, tumor relevance, and mechanisms controlling cyclin D1b were challenged.

EXPERIMENTAL DESIGN

First, relative expression of both cyclin D1 isoforms was determined in prostate adenocarcinomas. Second, relevance of the androgen axis was determined. Third, minigenes were created to interrogate the role of the G/A870 polymorphism (within the splice site), and findings were validated in primary tissue. Fourth, the effect of G/A870 on cancer risk was assessed in two large case-control studies.

RESULTS

Cyclin D1b is induced in tumors, and a significant subset expressed this isoform in the absence of detectable cyclin D1a. Accordingly, the isoforms showed noncorrelated expression patterns, and hormone status did not alter splicing. Whereas G/A870 was not independently predictive of cancer risk, A870 predisposed for transcript-b production in cells and in normal prostate. The influence of A870 on overall transcript-b levels was relieved in tumors, indicating that aberrations in tumorigenesis likely alter the influence of the polymorphism.

CONCLUSIONS

These studies reveal that cyclin D1b is specifically elevated in prostate tumorigenesis. Cyclin D1b expression patterns are distinct from that observed with cyclin D1a. The A870 allele predisposes for transcript-b production in a context-specific manner. Although A870 does not independently predict cancer risk, tumor cells can bypass the influence of the polymorphism. These findings have major implications for the analyses of D-cyclin function in the prostate and provide the foundation for future studies directed at identifying potential modifiers of the G/A870 polymorphism.

Cutaneous phenotype and MC1R variants as modifying factors for the development of melanoma in CDKN2A G101W mutation carriers from 4 countries

The G101W founder mutation is the most common CDKN2A mutation in Italy, Spain, and France. As the background of modifying genes, environmental exposures, and sun behavior vary across countries, studying G101W carriers from distinct countries offers a unique opportunity to evaluate possible modifying factors in melanoma development. We evaluated 76 G101W cases and 59 carrier controls from France, Italy, Spain, and the United States. Hair color and dysplastic nevi distributions differed significantly in cases and controls across the 4 study groups. Cases also varied significantly for eye color, freckling, and nevi. The distribution of MC1R variants in cases differed significantly across study groups because 12% of Italian melanoma patients had > or =2 MC1R variants vs. >50% for the other case groups. Several MC1R covariates showed significant associations with melanoma risk in all groups combined and in the American, French, and Spanish samples; no significant findings were observed in the Italian sample. In multiple-case families, the number and type of MC1R variants varied significantly between multiple-primary-melanoma and single-primary-melanoma patients from the 4 groups; there was also a significant decrease in median age at melanoma diagnosis as the number or type of MC1R variants increased. The variation in the effects of the cutaneous phenotypic and MC1R factors across the study sample suggests that these factors differentially contribute to development of melanoma even on a common genetic background of a germline CDKN2A mutation. Differences in melanoma risk across geographic regions justify the need for individual studies in each country before counseling should be considered.

Pharmacogenomics of acute leukemia

Pharmacogenomics provides knowledge regarding how genetic polymorphisms affect treatment responses. Such an approach is particularly needed in cancer therapy, as most chemotherapeutics drugs affect both tumor and normal cells, are ineffective in many patients and exhibit serious side effects. Leukemia exists in two different forms, myeloid and lymphoid. Acute lymphoblastic leukemia more frequently occurs in children, whereas the risk of acute myeloid leukemia is more common in adults. Despite significant progress in the treatment of these diseases, therapy is still unsuccessful in many patients. Prognosis is particularly poor in adult acute myeloid leukemia. Treatment failure in childhood acute lymphoblastic leukemia due to drug resistance remains the leading cause of cancer-related death in children. Here, we provide an overview of pharmacogenetics studies carried out in children and adults with acute lymphoblastic leukemia and acute myeloid leukemia, attempting to find the associations between treatment responses and polymorphisms in the genes whose products are needed for metabolism, and effects of drugs used in the treatment of leukemia.

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.

Tumor susceptibility and prognosis of breast cancer associated with the G870A polymorphism of CCND1

We aimed to investigate the role of CCND1 G870A polymorphism genetic and transcriptomic effects susceptibility in association with breast cancer carcinogenesis and clinical prognosis. A case-control study was conducted with the enrollment of 992 sporadic breast cancer patients and the corresponding 960 normal controls from routine mammographic or sonographic screening for breast cancer between 1995 and 2003 in Taiwan. The 167 fragment spanning the G870A polymorphism in exon 4-intron 4 boundary was amplified to identify genotype of CCND1 (G870A) polymorphism. Competitive RT-PCR were further performed to investigate alternative transcript in four different specimens in association with immunohistochemistry markers. The results showed that AG and AA subgroup were at increased risk for developing breast cancer compared with the GG genotype by 19% (OR 1.19 (0.85-1.67)) and by 34% (OR 1.34 (0.04-1.74)), respectively. A870 allele revealed a recessive tendency while GG and AA/AG subgroup was compared (OR 1.35 (1.07-1.70)). AA genotype also had a higher risk in premenopausal women than postmenopausal ones. The recurrence-free survival was longer in patients with GG+AG than that in patients with AA (P = 0.034). A870 allele produced more transcript b both in malignant. There were significant correlations between several immunohistochemistry markers (such as Ki-67) and cyclin D1 or CDk4. We concluded CCND1 G870A polymorphism make significant contribution to breast cancer in the country with the preponderance of breast cancer in young women. The role of G870A polymorphism in alternative transcript was not only implicated in CCND1 alternative splicing but also correlated with immunohistochemistry markers.

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.

Cyclin D1 in non-small cell lung cancer: a key driver of malignant transformation

PURPOSE

To review the evidence implicating the deregulation of cyclin D1 in the pathogenesis of non-small cell lung cancer (NSCLC), and to discuss the opportunities for targeted clinical intervention.

METHODS

Data published until June 2006 are summarized, and previously unpublished results from our own research are included.

RESULTS

In normal cells, cyclin D1 complexes with and activates cyclin-dependent kinases (CDK) and acts as a transcriptional regulator. The protein is frequently overexpressed in a wide range of cancers, sometimes coincident with CCND1 (cyclin D1) gene amplification (5-20% of tumours). A low level of somatic mutations have been seen in certain tumours. CCND1 is amplified in NSCLC and cyclin D1 is frequently overexpressed in tumours and pre-invasive bronchial lesions, generally from one parental allele. Mutation analyses revealed a frequent CCND1 gene polymorphism (A870G) that modulates alternative splicing and allows expression of an alternative cyclin D1 transcript (transcript cyclin D1b). The encoded cyclin D1b protein lacks a specific phosphorylation site required for nuclear export. Genotype has been correlated with the risk and/or severity of disease or drug response across a range of malignancies, including lung cancer. Together, these findings suggest a strong pathological role for cyclin D1 deregulation in bronchial neoplasia.

CONCLUSION

Current data indicate that cyclin D1 overexpression is not a consequence of, but rather a pivotal element in the process of malignant transformation in the lung and other tissues. This understanding may open new avenues for lung cancer diagnosis, treatment and prevention.

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.

Cyclin D1 gene (CCND1) polymorphism and the risk of squamous cell carcinoma of the larynx

Cyclin D1 is one of the key proteins involved in cell cycle control, and it is believed that its overexpression may be connected with tumorigenesis. A reason for cyclin D1 deregulation may be connected to a common G870A polymorphism at codon 242 in exon 4 of the CCND1 gene. This single nucleotide substitution, localized in the conserved splice donor site between exon 4 and the intron 4 boundary, might modulate the frequency of alternative splicing. It has been postulated that the A allele results in a higher level of mRNA (transcript b) encoding a protein with an altered C-terminal domain. The influence of CCND1 G-->A polymorphism for the risk of cancer and the prognosis of patients with different types of solid tumors has already been suggested. This study was conducted to investigate the association between the cyclin D1 gene polymorphism and laryngeal cancer risk, as well as the clinical outcome. We also examined the relationship between genotype/allele distributions and the cyclin D1 expression profile. The genotyping study was done using the PCR-RFLP method in 63 patients with larynx cancer and 102 healthy controls. The heterozygotic genotype GA as well as a combination of GA and AA genotypes were associated with an increased risk of larynx cancer compared to the GG genotype (OR =3.02; P =0.004 and OR =2.52; P =0.013, respectively). The A allele frequency was higher in cancer cases (0.484) than in controls (0.416) that were connected with a slightly increased risk of cancer development (OR =1.34); however, the difference was not significant. The AA genotype was associated with an early cancer onset compared to the GG genotype (median age: 51.5 and 63.0 years, respectively). We also demonstrated that the AA genotype was associated with the occurrence of lymph node metastases (OR =3.26) and a higher level of cyclin D1 overexpression. These results suggest that the CCND1 A allele may be a genetic factor that modulates the risk of larynx cancer development, and it may also have an effect on tumor biology and disease prognosis.

Cyclin D1 Gene Polymorphism and Susceptibility to Childhood Acute Lymphoblastic Leukemia in a Chinese Population

Cyclin D1 is a key protein involved in cell cycle regulation. A common A870G single nucleotide polymorphism in exon 4 of the cyclin D1 gene (CCND1) has an effect on the transcription of 2 different cyclin D1 messenger RNAs. Correlation between genetic polymorphism of A870G of CCND1 and clinical outcome among patients with acute lymphoblastic leukemia (ALL) has been reported. However, the effect on ALL occurrence remains unclear. To examine the genotypic frequency of CCND1 polymorphism, we performed a case-control study in a Chinese population of 183 children with ALL and 190 healthy controls. The genetic frequency of CCND1 had a significant overall correlation in patients and controls. The AA genotype of CCND1 showed a tendency to increase ALL risk 3.2898-fold compared with the AG + GG genotype (P = .0207). Stratification of patients according to cell type, risk level, and chemotherapeutic response showed significance for the AA genotype in T-cell ALL, ALL with high risk, and no complete remission (P = .047, P = .011, and P = .007, respectively). No gene dosage effect was observed in this study. The results of the present study suggested that CCND1 genetic polymorphism may be related to the occurrence of ALL in a population of Chinese children.

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.

Pharmacogenetics of methotrexate

Methotrexate (MTX) has proven efficient in the treatment of a number of malignancies, as well as non-malignant disorders characterized by a rapid cellular growth. Yet some patients might develop resistance, while others could have toxic side effects. MTX achieves its cytotoxicity through the inhibition of folate-dependent enzymes, suggesting that the genes controlling their activity or the levels of folate cofactors can modulate drug efficacy and, thus, the sensitivity of a patient to MTX. Indeed, several studies, conducted mostly in leukemia and rheumatoid arthritis patients, have addressed the potential for tailoring MTX therapy based on a patient's genetics. Several genetic variants have been shown to have a predictive role, among which the most frequently studied are those of methylenetetrahydrofolate reductase and thymidylate synthase genes. The other candidates, as well as gene-gene interactions, which may be even more important for the prediction of disease outcomes than the individual gene effects, are also briefly discussed.

Molecular biology of primary hyperparathyroidism

As molecular biology and genetic mapping receive wider application to human disease, genetic alterations have been identified with increased frequency in some patients with primary hyperparathyroidism(HPT). These alterations have been found in molecules related to cellular signaling and growth (RET proto-oncogene)and in tumor suppressors that control cell cycle progression and gene transcription (cyclin D1 and the MEN1 gene product. Although primary HPT can usually be treated surgically without knowledge of which specific genetic alteration has occurred, this information may assist clinicians in identifying which patients will go on to develop multiglandular or recurrent disease. In addition,such an approach would facilitate more appropriate postoperative surveillance, as well as counseling and screening of family members who may be at high risk for HPT.

The 870G>A polymorphism of the cyclin D1 gene is not associated with breast cancer

A common 870G > A polymorphism in the gene for cyclin D1, CCND1, has been linked to alternative splicing and cancer susceptibility. To analyze its role for breast cancer, we determined the CCND1 genotype in 500 breast cancer patients and 500 controls. CCND1 genotype frequencies were similar among patients and controls. The CCND1 genotype was furthermore not associated with tumor characteristics. We conclude that the CCND1 870G > A polymorphism is not associated with breast cancer.

The influence of cyclin D1 (CCND1) 870A>G polymorphism and CCND1-thymidylate synthase (TS) gene-gene interaction on the outcome of childhood acute lymphoblastic leukaemia

The 870A>G polymorphism in the cyclin D1 (CCND1) gene modulates mRNA splicing, leading to altered protein that may affect the regulation of the G1/S cell-cycle checkpoint. This polymorphism has been reported to influence susceptibility to and progression of several malignancies. Furthermore, the change of retinoblastoma protein regulation mediated by CCND1 may play a role in the development of methotrexate (MTX) resistance via an associated higher activity of enzymes that are inhibited by MTX. This study shows that children with acute lymphoblastic leukaemia (ALL) who are homozygous for the CCND1 A variant have a lower probability of event-free survival (P = 0.006) compared to carriers of the G variant. A significant result is retained in the presence of other prognostic factors. This impact is even more apparent in individuals who are also homozygous for thymidylate synthase (TS) triple repeat (P < 0.00005), which has previously been shown to influence the outcome of childhood ALL.

Cyclin D1 genotype in areca-associated oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the most common malignancy in areca-chewing regions, accounting for up to 50% of malignant tumors in some South Asian countries. Amplification and/or over-expression of cyclin D1 (CCND1) is a frequent event in human malignancies, including OSCC. CCND1 G870A polymorphism (codon 242) gives rise to two isoforms of the protein. The objective of the present study was to evaluate if the risk, onset, and prognosis of areca-associated OSCC is related to CCND1 genotypes.

METHODS

We analyzed the CCND1 genotype in 70 OSCC cases and 93 control Taiwanese using single-strand conformation polymorphism techniques.

RESULTS

Statistical analysis showed that CCND1 genotype had no impact on the risk, onset, or survival of areca-associated OSCC. However, buccal squamous cell carcinoma (BSCC) appeared to be less frequently associated with AA genotype than non-BSCC (P = 0.02). In addition, amplification of CCND1 was significantly more prevalent in OSCC cases (22%) than in control subjects (2%, P < 0.01).

CONCLUSION

This study demonstrates that the CCND1 genotype may confer different risks for BSCC and non-BSCC.

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 NeiI polymorphism in the cyclin D1 gene and sporadic primary hyperparathyroidism

OBJECTIVES

The cell cycle regulator cyclin D1 plays an important role in parathyroid tumourigenesis. The NciI polymorphism in exon 4 has recently been associated with early onset of hereditary nonpolyposis colorectal cancer and is a prognostic indicator of nonsmall cell lung cancer and squamous cell carcinomas. Furthermore, a limited study of 28 primary hyperparathyroidism (pHPT) patients displayed a tendency of NciI influence on HPT development. We hypothesized that the NciI polymorphism may relate to a risk of developing pHPT.

DESIGN, SETTING AND SUBJECTS

We genotyped 182 patients with sporadic pHPT and matched controls for the cyclin D1 polymorphism. A total of 88 pHPT patients and controls were recruited via a health-screening.

RESULTS

The frequency distribution of the NciI genotypes NN, Ni, and ii were in pHPT patients and controls 22, 44 and 34%, and 26, 49 and 25%, respectively. The calculated allele frequencies were A = 0.56; G = 0.44 in cases and A = 0.49; G = 0.51 in controls. The frequency distributions did not differ comparing cases and controls when subgrouped after age and menopausal status. The NciI genotypes were not significantly associated with age of the individuals, serum (s)-calcium, s-parathyroid hormone (PTH), bone mineral density (BMD) or parathyroid tumour weight in any of the groups of pHPT patients or controls.

CONCLUSIONS

No significant differences in distribution of the genotypes could be detected between the groups, suggesting that the polymorphism has minor or no pathogenic importance in the development of pHPT. Our results suggest that determination of the NciI polymorphism in the cyclin D1 gene is not a clinically useful tool for prediction of pHPT.

Primary hyperparathyroidism caused by parathyroid-targeted overexpression of cyclin D1 in transgenic mice

The relationship between abnormal cell proliferation and aberrant control of hormonal secretion is a fundamental and poorly understood issue in endocrine cell neoplasia. Transgenic mice with parathyroid-targeted overexpression of the cyclin D1 oncogene, modeling a gene rearrangement found in human tumors, were created to determine whether a primary defect in this cell-cycle regulator can cause an abnormal relationship between serum calcium and parathyroid hormone response, as is typical of human primary hyperparathyroidism. We also sought to develop an animal model of hyperparathyroidism and to examine directly cyclin D1's role in parathyroid tumorigenesis. Parathyroid hormone gene regulatory region--cyclin D1 (PTH--cyclin D1) mice not only developed abnormal parathyroid cell proliferation, but also developed chronic biochemical hyperparathyroidism with characteristic abnormalities in bone and, notably, a shift in the relationship between serum calcium and PTH. Thus, this animal model of human primary hyperparathyroidism provides direct experimental evidence that overexpression of the cyclin D1 oncogene can drive excessive parathyroid cell proliferation and that this proliferative defect need not occur solely as a downstream consequence of a defect in parathyroid hormone secretory control by serum calcium, as had been hypothesized. Instead, primary deregulation of cell-growth pathways can cause both the hypercellularity and abnormal control of hormonal secretion that are almost inevitably linked together in this common disorder.

Genetic alterations in primary and secondary hyperparathyroidism

Hyperparathyroidism refers to a term representing a wide spectrum of parathyroid disorders that are characterized by the increased production of parathyroid hormone. Hyperparathyroidism was once thought to be rare but is now more commonly recognized, affecting 1 in 500 women over 40 years of age. Yet the interpretation of parathyroid pathology is still controversial and confusing. Over the past 10 years, genetic changes (ret and menin genes) involved in the pathogenesis of MEN 2 and MEN 1 have been discovered in succession. Different mutations of the calcium-sensing receptor gene have been identified in neonatal severe hyperparathyroidism and familial hypocalciuric hypercalcemia, respectively. The HRPT 2 gene responsible for the development of hereditary hyperparathyroidism and jaw tumors has been localized on the 1q21-31 locus. Several genetic alterations have also been characterized in primary and secondary hyperparathyroidism. Different genetic alterations appear to involve the development of different types of hyperparathyroidism. These novel advances give us new insights into the pathogenesis of hyperparathyroidism and allow better differentiation between the different types of parathyroid disorders.

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.

Mechanism of cyclin D1 (CCND1, PRAD1) overexpression in human cancer cells: analysis of allele-specific expression

The cyclin D1/CCND1 oncogene (PRAD1) is amplified in 15% of primary human breast cancers and overexpressed in 30-50% of breast cancers, suggesting that mechanisms in addition to DNA amplification may lead to deregulated expression of this gene in breast cancer. Cyclin D1 overexpression at a higher frequency than gene amplification is also seen in a variety of other tumors. Cyclin D1 overexpression without amplification could result from a trans-acting regulatory disturbance or could be a consequence of a clonal regulatory mutation in one allele of the gene. We have, therefore, examined whether the overexpression of cyclin D1 mRNA is derived from one parental allele or both alleles in tumor cell lines with or without amplification of the cyclin D1 gene. Eight tumor cell lines, MCF-7, SK-BR-3, ZR-75-1, U-2-OS, SK-LMS-1, DLD1, HCT15, and HT29, out of 20 tumor cells initially examined were found to be heterozygous at the polymorphic NciI site within exon 4 of the cyclin D1 gene. Polymerase chain reaction and NciI digestion (PCR-RFLP) analysis of genomic DNA demonstrated DNA amplification of one allele in the ZR-75-1 cells and HT29 cells and no such imbalance in cyclin D1 gene copy number in the other cells, consistent with Southern blot analyses. Reverse-transcription polymerase chain reaction analysis and NciI digestion (RT-PCR-RFLP) of total cDNA revealed that the overexpressed cyclin D1 mRNA is preferentially derived from the amplified allele in the ZR-75-1 and HT29 cells. In contrast, the other tumor cells overexpressed cyclin D1 mRNA equally from both alleles. This finding strongly suggests that, in breast, sarcoma, and in colon cancer cells with cyclin D1 overexpression and normal gene copy number, elevated levels of cyclin D1 mRNA result from a trans-acting influence on both alleles rather than a clonal somatic mutation or rearrangement in or near a single cyclin D1 gene.

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

The cyclin D1/PRAD1 protooncogene is a key regulator of the G1 phase of the cell cycle and has been incriminated in the pathogenesis of a variety of primary human tumors. Recently, part of a novel alternatively spliced cyclin D1 transcript, called transcript b, has been identified. This variant transcript showed a failure of splicing at the 3' end of exon 4 and as a result, the expected protein product is altered at its C-terminus. Because of similar transcript sizes, previous Northern analyses would not have been expected to distinguish the two variants, and the relative levels of the two cyclin D1 transcripts in human tumors is unknown. To elucidate the role of cyclin D1 transcript b, we have isolated cDNA clones of this variant transcript from human breast cancer cell lines and report the sequence of the entire coding region of the cDNA. The protein predicted from the cDNA sequence consists of 274 amino acid residues and lacks a PEST sequence in its C-terminus. Examination of the levels of the two alternative cyclin D1 transcripts in primary breast cancers and breast cancer cell lines by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) assays showed that the variant transcript b is indeed expressed in primary breast cancers and breast cancer cell lines, but the level of transcript b is dramatically lower than that of the originally reported transcript a of the cyclin D1 gene. In breast cancers, oncogenic overexpression of cyclin D1 mRNA appears to consist overwhelmingly of transcript a, and the role of transcript b, if any, in oncogenesis remains to be established. Science Ireland Ltd.