Role of cyclin E and p53 expression in progression of early gastric cancer

Background. To elucidate the role that cyclin E overexpression plays in the progression of early gastric cancer, we examined the expression of cyclin E and p53, as abnormal p53 expression is linked with cyclin E overexpression in exerting adverse affects on the cell cycle. Methods. Specimens from 108 early gastric cancers were stained by an immunohistochemical method, using anti-cyclin E and anti-p53 antibodies. Results. The positivity rate of cyclin E expression in early gastric cancer was 33% (36/108). Cyclin E-positive tumors invaded more deeply (P < 0.05), infiltrated lymphatic vessels more frequently (P < 0.01), showed a higher incidence of differentiated cancer (P < 0.01), and more often expressed p53 (P < 0.01) than cyclin E-negative tumors. Differentiated cancers showing coexpression of cyclin E and p53 were more likely to metastasize to the lymph nodes. Conclusions. Overexpression of cyclin E may promote the progression of early gastric cancer. Received for publication on Apr. 27, 1998; accepted on Nov. 17, 1998     

Overexpression of Cyclin D1 in Rat Esophageal Carcinogenesis Model

Overexpression of cyclin D1 in human esophageal carcinomas has been well documented. The aim of the present study was to assess the expression of cyclin D1 in different types of esophageal epithelial lesions induced by N -nitrosomethylbenzylamine (NMBA) in rats. A total of 30 rats received s.c.-injections, five times/week, of 1.0 mg/kg NMBA for a period of 5 weeks followed by the same dose once per week for another 10 weeks. An additional 15 rats were given saline and used as controls to provide normal epithelium. The tumor incidence was 100% at the termination point of 21 weeks. Seventeen rats (57%) showed nuclear staining for cyclin D1, with a great variation in the intensity, as demonstrated by using an immunohistochemical technique. The cyclin D1 positive indices were in the range of 0% to 60% of the individual cells. Negligible staining was observed for normal esophageal epithelium, with a minimal increase in hyperplastic and dysplastic lesions. A significant elevation of cyclin D1 levels was observed in tumors. However, no significant differences were found between papillomas and carcinomas. The immunohistochemical results were confirmed by western blotting analysis. Tumors, papillomas and carcinomas overexpressing cyclin D1 had elevated proliferating cell nuclear antigen (PCNA) indices (P<0.05). The correlation coefficient of overexpressions of PCNA and cyclin D1 was r =0.7 for papillomas, but only r =0.3 for carcinomas. The study thus provides strong evidence of relatively early Overexpression of cyclin D1 during tumorigenesis in the present rat esophageal model. Cyclin D1 expression is not simply a direct consequence of increase cell proliferation.     

FBXO4 loss facilitates carcinogen induced papilloma development in mice

Cyclin D1 is frequently overexpressed in esophageal squamous cell carcinoma (ESCC) and is considered a key driver of this disease. Mutations in FBXO4, F-box specificity factor that directs SCF-mediated ubiquitylation of cyclin D1, occur in ESCC with concurrent overexpression of cyclin D1 suggesting a potential tumor suppressor role for FBXO4. To evaluate the contribution of FBXO4-dependent regulation cyclin D1 in esophageal squamous cell homeostasis, we exposed FBXO4 knockout mice to N-nitrosomethylbenzylamine (NMBA), an esophageal carcinogen. Our results revealed that loss of FBXO4 function facilitates NMBA induced papillomas in FBXO4 het (+/−) and null (−/−) mice both by numbers and sizes 11 months after single dose NMBA treatment at 2mg/kg by gavage when compared to that in wt (+/+) mice (P < 0.01). No significant difference was noted between heterozygous or nullizygous mice consistent with previous work. To assess cyclin D1/CDK4 dependence, mice were treated with the CDK4/6 specific inhibitor, PD0332991, for 4 weeks. PD0332991 treatment (150mg/kg daily), reduced tumor size and tumor number. Collectively, our data support a role for FBXO4 as a suppressor of esophageal tumorigenesis.     

Clinical significance of cyclin D1 expression in patients with node-positive breast carcinoma treated with adjuvant therapy

BACKGROUND:: Experimental and clinical studies suggest that cyclin D1 isinvolved in transformation and tumour progression. However,there is little and contradictory data on the clinical significanceof cyclin D1 in human invasive breast carcinoma. PATIENTS AND METHODS:: We investigated whether the determination of cyclin D1 has prognosticvalue in a series of 180 patients with node-positive breastcarcinoma and treated with adjuvant therapy with a median follow-upexceeding 6 years. We assessed cyclin D1 expression using theCDS-6 monoclonal antibody and a highly sensitive immunohistochemicaltechnique. RESULTS:: We found that most of the evaluable tumours (117 of 167; 70.1%)presented nuclear cyclin D1 staining and that its expressionwas significantly associated with both the hormone receptors(P=0.009 and P=0.005 for ER and PgR, respectively). Furthermore,29 (17%) of 167 tumours had a weak (15 cases) or strong (9 cases)cytoplasmic cyclin D1 staining. In a subgroup of cases we alsostudied the amplification of the cyclin D1 gene and a moderateagreement between cyclin D1 nuclear overexpression assessedimmunohistochemically and the gene amplification was found. In univariate analysis, cyclin D1 nuclear positivity was significantlyassociated with improved 6-year relapse-free survival (RFS)(P=0.004), but not with overall survival (OS) (P=0.12). Theresults of the Cox multivariate analysis (final model) indicatethat cyclin D1 expression (P=0.0049) as well as the number ofinvolved nodes (P<0.001) and tumour size (P=0.036) are significantprognostic indicators for RFS. Only the number of involved nodesretained significance (P<0.001) for OS in our series. The joint assessment of the variables considered in the finalmodel of the multivariate analyses had a moderate prognosticcapability as determined using the Harrell c statistic (c=0.66and 0.64 for RFS and OS, respectively). CONCLUSIONS:: The patients with node-positive breast cancer who have a higherlikelihood of gaining benefit from adjuvant therapy are thosewith tumours with cyclin D1 nuclear expression, small size andless than 3 metastatic nodes. Further studies are needed to verify the prognostic value ofcyclin D1 in relation to different adjuvant treatments and todeepen the biological pathways that regulate its activation/suppressionin human breast carcinoma. breast cancer, cyclin D1, p53, prognosis     

Cyclin D1 expression is associated with poor prognostic features in estrogen receptor positive breast cancer

Cyclins D1 and E play an important role in breast carcinogenesis. High cyclin E expression is common in hormone receptor negative and high grade aggressive breast cancer, whereas cyclin D1 in hormone receptor positive and low grade breast cancer. Experimental data has suggested that cyclin D1 and E mediate cell proliferation by different mechanisms in estrogen receptor (ER) positive and negative breast cancer. To test this hypotheses in large breast cancer material and to clarify the histopathological correlations of cyclin E and D1, especially the association with proliferation, we analyzed cyclin E and D1 immunohistochemical expression on breast tumour microarrays consisting of 1348 invasive breast cancers. High cyclin D1 expression was associated with high grade (P < 0.0005), high cyclin A (P < 0.0005) and Ki67 (P < 0.0005) expression among ER positive but with low grade (P = 0.05) and low Ki67 (P = 0.01) expression among ER negative breast cancers. Cyclin E and D1 expression correlated positively in ER positive (P < 0.0005) but had a negative correlation in ER negative tumours (P = 0.004). Cyclin E associated with high grade among all tumours (P < 0.0005). In conclusion, the findings of this study show that cyclin D1 has separate roles, and proliferation is driven by different mechanisms in ER positive and negative breast cancers.     

Aberrant cytoplasmic expression of cyclin B1 protein and its correlation with EBV-LMP1, P53 and P16(INK4A) in classical Hodgkin lymphoma in China

The relationships between the expression of cyclin B1, EBV-LMP1, P53 and P16(INK4A) in Chinese classical Hodgkin lymphoma are unknown and need exploring. Samples of classical Hodgkin lymphoma from 60 Chinese patients were analyzed for the expression of cyclin B1, EBV-LMP1, P53 and P16(INK4A) proteins by immunohistochemistry. Cyclin B1 protein was overexpressed in 90.0% (54/60) of this group of classical Hodgkin lymphoma, staining mainly and strongly in cytoplasm but also sparsely and weakly in nucleus of the Hodgkin and Reed-Sternberg (HRS) cells. EBV-LMP1, P53 and P16(INK4A) were overexpressed in 85.0%, 96.7% and 71.7% of Hodgkin lymphoma, respectively. EBV-LMP1, P53 and P16(INK4A) were was noted in the nucleus of HRS cells. Microscopically, cyclin B1 and P53 staining distinguished the HRS cells from the complex background of lymphocytes. Cyclin B1 was positively correlated with EBV-LMP1(P < 0.001) and P53(P < 0.001), but was inversely related to P16(INK4A) (P < 0.05). It is suggested that overexpression of cyclin B1 could play an important role in the evolution of classical Hodgkin lymphoma, and cyclin B1 may be considered as a potential adjunct marker to identify HRS cells in diagnosis and be served as Hodgkin lymphoma-associated antigen in the near future.     

High cyclin D3 expression confers erlotinib resistance in aerodigestive tract cancer

Background

Prior studies highlighted cyclin D1 as a key biomarker of response to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. This study builds on prior work by examining the roles of cyclin D1, cyclin D3, and cyclin E in mediating erlotinib sensitivity or resistance.

Methods

Expression plasmids for G1 cyclins were independently transfected into NIH 3T3 cells and effects on erlotinib sensitivity were examined. The expression profiles of G1 cyclins were compared in erlotinib-sensitive and erlotinib-resistant lung cancer cell lines. A549 and H358 cells were treated with erlotinib and changes in cyclin protein expression were assessed. Cyclin D3 immunohistochemical staining was measured in biopsy tissues obtained from patients before and after treatment with erlotinib. Erlotinib-sensitive lung cancer cells were transfected with cyclin D3 and changes in erlotinib sensitivity were examined.

Results

Individual transfection of cyclin D1, cyclin D3, and cyclin E expression plasmids each significantly reduced erlotinib sensitivity in NIH-3T3 cells. The erlotinib-resistant A549 cell line expressed high basal levels of cyclin D3 mRNA and protein. Comparison of tumor biopsies obtained from patients before and after treatment with erlotinib indicated an increase in the percentage of cancer cells expressing cyclin D3 following treatment with erlotinib (P = .02). Transfection of cyclin D3 into an erlotinib-sensitive lung cancer cell line inhibited erlotinib-induced signaling changes and reduced the growth-suppressive effects of erlotinib.

Conclusions

High expression of cyclin D3 confers resistance to erlotinib in vitro and in vivo. Cyclin D3 immunohistochemical staining warrants investigation as a biomarker for predicting erlotinib resistance.     

Deregulated expression of cyclin D1 and other cell cycle-related genes in carcinogen-induced rat mammary tumors

Dysregulation of cyclin expression has been reported for severalhuman malignancies, including breast cancer. To further investigatethe role of cyclin genes in mammary tumorigenesis we analyzedthe expression of cyclins D1, E and A and other cell cycle-relatedproteins in a series of nine N-methyl-N-nitrosourea-inducedprimary rat mammary tumors. Western blot analysis revealed a10- to 15-fold increase in the level of cyclin D1 protein inmost (7/9) of the tumors, when compared with normal rat mammarygland. The two tumors that did not show this increase also displayednegligible levels of the retinoblastoma protein. A moderateincrease, 1.5- to 2-fold, in the level of cyclin E was observedin four tumors and three tumors displayed abnormal low molecularweight cyclin E-related proteins. None of the tumors showedamplification of the cyclin D1 or E genes when studied by Southernblot analysis. All nine tumors showed a 2- to 6-fold increasein the level of cyclin A protein. Most of the tumors also displayeda marked increase in levels of the CDK2 and CDK4 proteins. Thesechanges did not appear to be simply a consequence of increasedcell proliferation, as assessed by proliferating cell nuclearantigen analysis. Thus, aberrant expression of cyclins and othercyclin-related genes occurs frequently in mammary tumorigenesisin both rodents and humans     

Evaluation of dose and treatment duration on the esophageal tumorigenicity of N-nitrosomethylbenzylamine in rats

N-Nitrosomethylbenzylamine (NMBA) is a potent esophagus-specificcarcinogen that has been utilized extensively in the study ofesophageal carcinogenesis in rats. While many studies have focusedon the pathogenesis of NMBA-induced esophageal tumors, the tumorigenicityof NMBA itself has not been thoroughly investigated in any single,systematic dose-response study. Therefore, in this study weevaluated NMBA tumorigenicity in rats following various short-terms.c. treatment regimens with the aim of developing an abbreviatedtreatment protocol which could be used in future studies. Toassess the possible correlation of basal cell proliferationwith NMBA tumorigenicity, we evaluated the expression of proliferatingcell nuclear-antigen (PCNA) in both control and NMBA-treatedrats. In rats which received a cumulative NMBA dosage of 7.5mg/kg over the course of 5 weeks, tumor incidence and multiplicitywere as follows: 40% with 0.4 ± 0.3 tumors/rat at week10; 100% with 2.2 ± 1.0 tumors/rat at week 20; and 100%with 2.3 ± 1.0 tumordrat at week 30. These rats exhibitedmarked increases in basal cell labeling, with indices that were1.5- to 1.8-fold higher than controls. NMBA treatment regimensof shorter duration with equivalent or higher cumulative dosageswere generally ineffective in producing esophageal tumors, eventhough significantly elevated levels of basal cell proliferationoccurred. Together, these findings indicate that the durationof NMBA treatment is of critical importance in the tumorigenicpotential of the carcinogen.     

The expressions and significance of α-, β-catenins and cyclin D1 in breast cancers

Objective  To study the relationship between expressions of α-, β-catenins and cyclin D1 and the occurrence, infiltration and metastasis of breast cancer. Methods  High sensitive S-P immunohistochemical method was used to detect the protein expressions of α-, β-catenins and cyclin D1 in the 60 cases of breast cancer tissues. Results  Abnormal immunoreactivities of α-and β-catenins were observed in 37 (61.7%) and 42 (70%) cases of breast cancer tissues, respectively. There were 28 cases (46.7%) who showed cyclin D1 overexpression. The abnormal expression rates of α-and β-catenins in infiltrating lobular carcinoma (ILC) were significantly higher than those in infiltrating ductal carcinoma (IDC) (P < 0.05), but they had no relations to the extent of differentiation and lymphatic metastasis of breast cancer (P > 0.05). The overexpression rate of cyclin D1 was correlated with tumor stage and lymphatic metastasis of breast cancer (P < 0.05), but not with histological type and the extent of differentiation (P > 0.05). Cyclin D1 overexpression was observed in 57.1% (24/42) of these cases that showed abnormal staining of β-catenin, but only observed in 22.2% (4/18) of these cases with normal membranous staining of β-catenin. There was a significantly positive correlation between the abnormal expression of β-catenin and overexpression of cyclin D1 (r _s = 0.321, P < 0.05). Conclusion  The abnormal expression of β-catenin may play an important role in the genesis of breast cancer by triggering cyclin D1 overexpression in breast cancer. The abnormal expressions of α-and β-catenins are not a key factor in malignant cell metastasis in breast cancer, but may also involve in the progress.     

Expression of cyclin E and cyclin D1 in non-small cell lung cancers

The relationships between overexpression of cyclin D1 or cyclin E and clinicopathological factors were investigated in 157 patients with non-small cell lung cancers (NSCLCs) using immunohistochemical analysis. Fifty-eight cases of NSCLCs (58/157, 37%) showed the overexpression of cyclin D1, and 64 cases (64/157, 41%) were positive for cyclin E. Cyclin E and cyclin D1 were infrequently concurrently overexpressed (17/157, 10.8%). Overexpression of cyclin E was more frequently observed in squamous cell carcinoma (29/57, 51%) compared with that in adenocarcinoma (28/86, 33%) (P<0.05). In addition, overexpression of cyclin E was more frequently observed in poorly or moderately differentiated NSCLCs (52/103, 50%) than in well-differentiated ones (12/54, 22%) regardless of their histological types (P<0.01). On the contrary, there was no statistically significant relationship between cyclin D1 overexpression and histological types or grade of tumor differentiation. These findings suggest that expression of cyclin E was frequently independent of that of cyclin D1 and played some roles in the grade of tumor differentiation in NSCLCs.     

细胞周期素D1的表达与肺癌临床生物学特性的关系研究

目的：研究细胞周期素Ｄ１（Ｃｙｃｌｉｎ Ｄ１）在肺癌中的表达及其与肺癌临床生物学特性的关系。方法：采用免疫斑点和免疫组化法对４６例肺癌患进行Ｃｙｃｌｉｎ Ｄ１检测。结果：Ｃｙｃｌｉｎ Ｄ１在肺癌中的表达高于正常肺组织，且与肺癌的分化和转移密切相关，与吸烟也有一定关系。结论：Ｃｙｃｌｉｎ Ｄ１的过在肺癌发生发展过程中可能起到重要作用。     

Cyclin E、CDK2和p21WAF1在食管上皮癌变过程中的表达及意义

目的探讨食管上皮癌变过程中细胞周期调控因子cyclin E、CDK2和p21WAF1的表达状况及其意义.方法应用免疫组化SP法和原位杂交方法分别检测48例食管癌组织、31例非典型增生组织和17例正常食管粘膜中cyclin E、CDK2和p21WAF1蛋白及mRNA表达.应用半定量RT-PCR和Western blot检测22例新鲜食管癌及相应癌旁组织的mRNA和蛋白表达.结果从食管正常粘膜、非典型增生组织到癌组织,cyclin E和CDK2蛋白和mRNA阳性表达率逐渐上升,差异具有统计学意义(P＜0.01或P＜0.05).食管癌组织中cyclin E、CDK2和p21WAF1蛋白及mRNA高表达,与癌旁组织或切缘正常食管粘膜有显著性差异(P＜0.01).cyclin E、CDK2和p21WAF1基因表达显著正相关(P＜0.01或P＜0.05).结论食管上皮癌变过程中,细胞周期相关基因cyclin E和CDK2表达逐渐增强.cyclin E基因表达异常是食管癌变过程中的早期事件.p21WAF1基因在食管癌中高表达,可能与细胞周期调控的反馈机制有关.     

Specific Overexpression of Cyclin E·CDK2 in Early Preinvasive and Primary Breast Tumors in Female ACI Rats Induced by Estrogen

Overexpressed Aurora A, amplified centrosomes, and aneuploidy are salient features of estrogen-induced mammary preinvasive lesions and tumors in female August--Copenhagen Irish (ACI) rats. Intimately involved in these events are cyclins and their associated cyclin-dependent kinase (CDK) partners. Cyclin E1·CDK2 overexpression plays an important dual role in late G1/S phase of the cell cycle in cancer cells. It increases DNA replication providing growth advantage to cancer cells and facilitates aberrant centrosome duplication, generating chromosomal instability and aneuploidy leading to tumor development. Presented herein, a 24.0- and 45.0-fold elevation in cyclin E1 and CDK2 was found in 17β-estradiol (E(2))-induced ACI rat mammary tumors (MTs), respectively. Cyclin E·CDK2 positive staining was confined to the large round cells found within focal dysplasias, ductal carcinomas in situ, and invasive MTs. Co-immunoprecipitation and in vitro kinase activity of these tumors revealed that these cell cycle entities are functional. When mammary tissue derived from untreated normal, E(2)-induced hyperplasia and primary tumors were normalized to cyclin E1 levels, low molecular weight (LMW) cyclin E1 forms (33- and 45-kDa) were detected in all of these tissue groups. Moreover, increasing concentrations of protease inhibitor in tissue lysates resulted in a marked reduction of LMW forms, indicating that the presence of cyclin E1 LMW forms can be markedly reduced. Significant increases in cyclin E1 mRNA (2.1-fold) were detected in primary ACI rat E(2)-induced breast tumors, and quantitative real-time polymerase chain reaction revealed a 20% amplification of the cyclin E1 gene (CCNE1). Collectively, these results support the involvement of cyclin E1·CDK2 in centrosome overduplication during each stage of E(2)-induced mammary tumorigenesis.     

Cyclin A and cyclin B1 overexpression in differentiated thyroid carcinoma

Approximately 30% of patients with thyroid nodules have indeterminate or suspicious fine-needle aspiration (FNA) biopsy results. These patients usually undergo thyroidectomy because of cancer risk. Our aim was to determine diagnostic value of cyclin A and cyclin B1 immunohistochemistry added to routine cytology and their expression on histological sections. We studied the expression of cyclin A and cyclin B1 in FNA biopsies and resection specimens of 168 indeterminate or suspicious FNA biopsy results retrospectively at an academic hospital using immunohistochemistry. Malignant histopathology consisted 64 of resection specimens (58 papillary, 4 follicular, 1 medullary, and 1 Hürthle cell carcinoma). Cyclin A was overexpressed in 51.5% of malignant cases in contrast to 31.7% of 104 benign pathology specimens (P = 0.025). Cyclin B1 was positive in 39.1% of malignant specimens in contrast to 15.4% of benign cases (P = 0.001). Cyclin A overexpression was not linked to cyclin B1 overexpression. No association was found between overexpression of cyclin A, cyclin B1 and age, thyroiditis, multifocality, tumor size, extra-thyroidal extension, capsule infiltration, lymph node and distant organ metastases and TNM stage in malignant cases. Female patients with thyroid carcinoma overexpressed significantly more cyclin B1 than male patients (P = 0.015). Retrospective analysis of cyclin A and cyclin B1 in FNA biopsies yielded negative results for both benign and malignant cases. In conclusion, cyclin A and cyclin B1 are useful markers in the distinction of benign and malignant thyroid tumors and can increase diagnostic accuracy.     

Cell proliferation and esophageal carcinogenesis in the zinc-deficient rat

Target cell proliferation was investigated throughout the developmentof esophageal cancer induced by N-nitroso-methylbenzylamine(NMBA) in weanhing rats maintained on zinc-deficient or sufficientdiets. Deficient rats were fed ad libitum, while zinc-sufficientrats were either pair-fed to the deficient animals or fed adlibitum. After 5 weeks, half of the animals in each dietarygroup were given six intragastric doses of NMBA (2 mg/kg; twiceweekly). The remaining rats were untreated by carcinogen. Atweeks 1, 2, 3, 4, 5, 7, 9 and 11 post first dose, esophagealcell proliferation was assessed in rats from each group by invivo bromodeoxyuridine (BrDU) labeling followed by immunohistochemicaldetection of cells in S-phase. At 11 weeks, the tumor incidencewas 100, 23 and 6%, respectively, in the zinc-deficient, zinc-sufficient,ad libitum and pair-fed groups. In vivo BrDU labeling revealedthat in the NMBA-untreated groups, the labeling index (LI),the number of labeled cells, and the total number of cells percross section of entire esophagi were significantly increasedby zinc deficiency at all time points; LI was lowest in zinc-sufficient,pair-fed rats. During NMBA treatment (weeks 6, 7 and 8), increasedcell proliferation occurred in both groups of zinc-sufficientesophagi but only during week 6 in the deficient ones. In theweeks following the cessation of NMBA treatment, zinc-deficientesophagi showed significantly increased LI and greater numberof labeled cells than the carcinogen treated, zinc-sufficientpair-fed or ad libitum fed groups. On the other hand, NMBA-treatedzinc-sufficient pair-fed rats showed lower LI and smaller numberof labeled cells than their zinc-sufficient ad libitum counterparts.Most importantly, esophageal papillomas were found in two zinc-deficientanimals that had received no NMBA treatment, after 10–11weeks of experimental diet These data support a direct relationshipbetween cell proliferation and tumor incidence, and also provideevidence that zinc deficiency and its associated cell proliferationcould be carcinogenic.     

Increased expression of cyclin E is associated with an increased resistance to doxorubicin in rat fibroblasts

Cell cycle progression in eukaryotic cells is regulated by a family of cyclin-dependent kinases (CDKs). Cyclin E is a regulatory subunit of CDK2 and drives cells from G1 to S phase. Increased expression of cyclin E is a frequent event in human malignancies and has been associated with poor prognosis in various cancers. In this study, we evaluated the effects of cyclin E-overexpression on the sensitivity of rat fibroblasts to anticancer drugs. Cyclin E-overexpressing cells were less sensitive to doxorubicin-induced inhibition of cell growth but not to other antineoplastic drugs, such as paclitaxel, vincristine, etoposide and methotrexate. Cyclin E-overexpressing fibroblasts also displayed a reduction in ROS levels and a significantly lower increase following doxorubicin treatment compared with vector control cells. The expression of manganese superoxide dismutase (MnSOD) and its activity were increased (about 1.3-fold) in cyclin E-overexpressing derivatives compared with control cells. These results suggest that cyclin E overexpression might reduce tumour cells sensitivity to doxorubicin by affecting the expression of MnSOD and that determination of cyclin E expression levels might help to select patients to be treated with an anthracycline-based antineoplastic therapy.     

Cyclin D1 and cyclin E expression in malignant thyroid cells and in human thyroid carcinomas

Evidence of the involvement of cyclin gene alterations in human cancer is growing. In this study, we sought to determine the pattern of expression of cyclin D1 and cyclin E in normal and malignant thyroid cells. Quiescent rat thyroid cells in culture, induced to synthesize DNA by thyrotropin (TSH), expressed cyclin D1 gene after 6 hr and cyclin E gene with a peak at 18 hr from the stimulus; K-ras-transformed rat thyroid cells, which grew without addition of hormones necessary for normal cell proliferation, expressed elevated levels of cyclin D1 and cyclin E, compared with normal differentiated thyroid cells. Human benign and malignant thyroid tumors and their relative normal tissues were then analyzed. Neither major genetic alterations nor amplifications for cyclin D1 and cyclin E genes were found by Southern blot analysis in genomic DNAs extracted from all types of thyroid tumors. Moreover, statistical analyses of densitometric values from Northern blots did not show increased levels of cyclin D1 and E mRNAs in the tumor samples, compared with normal thyroid. Immunohistochemical analyses of formalin-fixed, paraffin-embedded sections of tissues with specific antibodies revealed a prevalent cytoplasmic cyclin E staining in the thyroid tissues analyzed. Cyclin D1, instead, was present in the cytoplasm of normal thyroids and adenomas, but in 31% of thyroid papillary carcinomas analysed, it was overexpressed, with a localization in the nucleus. Our in vivo observations suggest that unlike cyclin E, elevated nuclear cyclin D1 expression defines a subset of thyroid papillary carcinomas, and might be a contributory factor to thyroid tumorigenesis. Int. J. Cancer 76:806–811, 1998.© 1998 Wiley-Liss, Inc.