Cyclin D1 expression is regulated by the retinoblastoma protein

Nasopharyngeal Carcinoma Progression: Accumulating Genomic Instability and Persistent Epstein–Barr Virus Infection

Genomic instability facilitates the evolution of cells, tissues, organs, and species. The progression of human malignancies can be regarded as the accumulation of genomic instability, which confers a high evolutionary potential for tumor cells to adapt to continuous changes in the tumor microenvironment. Nasopharyngeal carcinoma (NPC) is a head-and-neck squamous-cell carcinoma closely associated with Epstein–Barr virus (EBV) infection. NPC progression is driven by a combination of accumulated genomic instability and persistent EBV infection. Here, we present a review of the key characteristics of genomic instability in NPC and the profound implications of EBV infection. We further discuss the significance of profiling genomic instability for the assessment of disease progression and treatment efficacy, as well as the opportunities and challenges of targeted therapies for NPC based on its unique genomic instability.

Lysine stimulates the development of the murine mammary gland at puberty via PI3K/AKT/mTOR signalling axis

Lysine is one of the essential amino acids. The effect of lysine on milk protein and milk fat anabolism has been reported, but the effect on mammary glands development has not been studied in detail. The normal development of the mammary glands at puberty is crucial to lactation of mammals. In this study, to explore the effect of lysine on mammary glands development, we fed different concentrations of lysine (0.025%, 0.05%, 0.1%) to pubertal mice and found that the addition of 0.1% lysine to drinking water significantly promoted mammary glands development. Furthermore, we treated mMECs (mouse mammary epithelial cells) with different concentrations of lysine (0, 0.2, 0.4, 0.6, 0.8 and 1 mM) to explore the underlying mechanism, and found that lysine promoted the proliferation of mMECs and development of mammary glands through PI3K/AKT/mTOR signalling pathway in pubertal mice. Overall, the results of this study revealed that lysine activated the PI3K/AKT/mTOR signal axis, elevated protein concentrations of cell proliferation markers, such as PCNA, Cyclin D1 and D3, and enhanced the proliferation of mMECs, finally promoted the murine mammary glands development at puberty.

The Mus musculus Papillomavirus Type 1 E7 Protein Binds to the Retinoblastoma Tumor Suppressor: Implications for Viral Pathogenesis

The species specificity of papillomaviruses has been a significant roadblock for performing in vivo pathogenesis studies in common model organisms. The Mus musculus papillomavirus type 1 (MmuPV1) causes cutaneous papillomas that can progress to squamous cell carcinomas in laboratory mice. The papillomavirus E6 and E7 genes encode proteins that establish and maintain a cellular milieu that allows for viral genome synthesis and viral progeny synthesis in growth-arrested, terminally differentiated keratinocytes. The E6 and E7 proteins provide this activity by binding to and functionally reprogramming key cellular regulatory proteins. The MmuPV1 E7 protein lacks the canonical LXCXE motif that mediates the binding of multiple viral oncoproteins to the cellular retinoblastoma tumor suppressor protein, RB1. Our proteomic experiments, however, revealed that MmuPV1 E7 still interacts with RB1. We show that MmuPV1 E7 interacts through its C terminus with the C-terminal domain of RB1. Binding of MmuPV1 E7 to RB1 did not cause significant activation of E2F-regulated cellular genes. MmuPV1 E7 expression was shown to be essential for papilloma formation. Experimental infection of mice with MmuPV1 expressing an E7 mutant that is defective for binding to RB1 caused delayed onset, lower incidence, and smaller sizes of papillomas. Our results demonstrate that the MmuPV1 E7 gene is essential and that targeting noncanonical activities of RB1, which are independent of RB1's ability to modulate the expression of E2F-regulated genes, contribute to papillomavirus-mediated pathogenesis. IMPORTANCE Papillomavirus infections cause a variety of epithelial hyperplastic lesions, or warts. While most warts are benign, some papillomaviruses cause lesions that can progress to squamous cell carcinomas, and approximately 5% of all human cancers are caused by human papillomavirus (HPV) infections. The papillomavirus E6 and E7 proteins are thought to function to reprogram host epithelial cells to enable viral genome replication in terminally differentiated, normally growth-arrested cells. E6 and E7 lack enzymatic activities and function by interacting and functionally altering host cell regulatory proteins. Many cellular proteins that can interact with E6 and E7 have been identified, but the biological relevance of these interactions for viral pathogenesis has not been determined. This is because papillomaviruses are species specific and do not infect heterologous hosts. Here, we use a recently established mouse papillomavirus (MmuPV1) model to investigate the role of the E7 protein in viral pathogenesis. We show that MmuPV1 E7 is necessary for papilloma formation. The retinoblastoma tumor suppressor protein (RB1) is targeted by many papillomaviral E7 proteins, including cancer-associated HPVs. We show that MmuPV1 E7 can bind RB1 and that infection with a mutant MmuPV1 virus that expresses an RB1 binding-defective E7 mutant caused smaller and fewer papillomas that arise with delayed kinetics.

Downregulation of TCEAL7 expression induces CCND1 expression in non-small cell lung cancer

Transcription Elongation Factor A-like 7 (TCEAL7) was first reported as a candidate tumor suppressor gene because of its inactivation in ovarian cancer as a result of promoter methylation. Down-regulation of the TCEAL7 gene expression was also associated with other cancers such as endometrial, breast, brain, prostate, gastric cancers, glioblastoma and linked to tumor phenotypes and clinical outcomes. However, there is no report in the literature investigating the role of TCEAL7 in non-small cell lung cancer. Cyclin D1 is an important molecule in the transition from G1 to S phase of the cell cycle, and is frequently deregulated in cancers. Cylin D1 (CCND1) gene is amplified or overexpressed in a variety of tumors. In our previous study we reported that CCND1 over-expression was not associated with amplification in non-small cell lung cancer. Recently, it has been reported that TCEAL7 regulates CCND1 expression through myc-binding E-box sequences. The aim of this study was to investigate the expression of TCEAL7 gene in non-small cell lung cancer and to determine its effect on the CCND1 expression level. For this purpose, expression levels of TCEAL7 and CCND1 genes were investigated in 50 patients with non-small cell lung cancer by quantitative real time polymerase chain reaction (qRT-PCR). TCEAL7 was under-expressed (68%) in non-small cell lung cancer tumor tissues while CCND1 was over-expressed (42%). The TCEAL7 levels negatively correlated with increased CCND1 expression (p = 0.002).

Targeting glutamine-addiction and overcoming CDK4/6 inhibitor resistance in human esophageal squamous cell carcinoma

The dysregulation of Fbxo4-cyclin D1 axis occurs at high frequency in esophageal squamous cell carcinoma (ESCC), where it promotes ESCC development and progression. However, defining a therapeutic vulnerability that results from this dysregulation has remained elusive. Here we demonstrate that Rb and mTORC1 contribute to Gln-addiction upon the dysregulation of the Fbxo4-cyclin D1 axis, which leads to the reprogramming of cellular metabolism. This reprogramming is characterized by reduced energy production and increased sensitivity of ESCC cells to combined treatment with CB-839 (glutaminase 1 inhibitor) plus metformin/phenformin. Of additional importance, this combined treatment has potent efficacy in ESCC cells with acquired resistance to CDK4/6 inhibitors in vitro and in xenograft tumors. Our findings reveal a molecular basis for cancer therapy through targeting glutaminolysis and mitochondrial respiration in ESCC with dysregulated Fbxo4-cyclin D1 axis as well as cancers resistant to CDK4/6 inhibitors.

The 4-Celled Tetrabaena socialis Nuclear Genome Reveals the Essential Components for Genetic Control of Cell Number at the Origin of Multicellularity in the Volvocine Lineage

Multicellularity is the premier example of a major evolutionary transition in individuality and was a foundational event in the evolution of macroscopic biodiversity. The volvocine chlorophyte lineage is well suited for studying this process. Extant members span unicellular, simple colonial, and obligate multicellular taxa with germ-soma differentiation. Here, we report the nuclear genome sequence of one of the most morphologically simple organisms in this lineage-the 4-celled colonial Tetrabaena socialis and compare this to the three other complete volvocine nuclear genomes. Using conservative estimates of gene family expansions a minimal set of expanded gene families was identified that associate with the origin of multicellularity. These families are rich in genes related to developmental processes. A subset of these families is lineage specific, which suggests that at a genomic level the evolution of multicellularity also includes lineage-specific molecular developments. Multiple points of evidence associate modifications to the ubiquitin proteasomal pathway (UPP) with the beginning of coloniality. Genes undergoing positive or accelerating selection in the multicellular volvocines were found to be enriched in components of the UPP and gene families gained at the origin of multicellularity include components of the UPP. A defining feature of colonial/multicellular life cycles is the genetic control of cell number. The genomic data presented here, which includes diversification of cell cycle genes and modifications to the UPP, align the genetic components with the evolution of this trait.

Long non-coding RNA LINC-01572:28 inhibits granulosa cell growth via a decrease in p27 (Kip1) degradation in patients with polycystic ovary syndrome

BACKGROUND

Disordered folliculogenesis is a key feature of polycystic ovary syndrome (PCOS), but the underlying molecular mechanism remains unclear.

METHODS

Long non-coding RNA (lncRNA) expression in luteinized granulosa cells (hLGCs) derived from women with and without PCOS were analyzed using microarray and qRT-PCR. Immortalized human granulosa cell lines were cultured for proliferation assays after transfection with the LINC-01572:28 over-expression vector in the presence or absence of p27 siRNA. Protein expression analysis, rescue assays, and RNA immunoprecipitation (RIP) were used to confirm the LINC-01572:28 substrate.

FINDINGS

LINC-01572:28 and p27 protein were elevated whereas proliferating cell nuclear antigen protein was decreased in the hLGCs of women with PCOS. LINC-01572:28 expression was positively correlated with basal testosterone levels. Over-expression of LINC-01572:28 inhibited cell proliferation and impeded G1/S transition, which were partially reversed by siRNA-mediated p27 knockdown.

INTERPRETATION

Our findings, therefore, suggest that LINC-01572:28 suppresses cell proliferation and cell cycle progression by reducing the degradation of p27 protein via SKP2 binding.

Stem-Like Signature Predicting Disease Progression in Early Stage Bladder Cancer. The Role of E2F3 and SOX4

The rapid development of the cancer stem cells (CSC) field, together with powerful genome-wide screening techniques, have provided the basis for the development of future alternative and reliable therapies aimed at targeting tumor-initiating cell populations. Urothelial bladder cancer stem cells (BCSCs) that were identified for the first time in 2009 are heterogenous and originate from multiple cell types; including urothelial stem cells and differentiated cell types—basal, intermediate stratum and umbrella cells Some studies hypothesize that BCSCs do not necessarily arise from normal stem cells but might derive from differentiated progenies following mutational insults and acquisition of tumorigenic properties. Conversely, there is data that normal bladder tissues can generate CSCs through mutations. Prognostic risk stratification by identification of predictive markers is of major importance in the management of urothelial cell carcinoma (UCC) patients. Several stem cell markers have been linked to recurrence or progression. The CD44v8-10 to standard CD44-ratio (total ratio of all CD44 alternative splicing isoforms) in urothelial cancer has been shown to be closely associated with tumor progression and aggressiveness. ALDH1, has also been reported to be associated with BCSCs and a worse prognosis in a large number of studies. UCC include low-grade and high-grade non-muscle invasive bladder cancer (NMIBC) and high-grade muscle invasive bladder cancer (MIBC). Important genetic defects characterize the distinct pathways in each one of the stages and probably grades. As an example, amplification of chromosome 6p22 is one of the most frequent changes seen in MIBC and might act as an early event in tumor progression. Interestingly, among NMIBC there is a much higher rate of amplification in high-grade NMIBC compared to low grade NMIBC. CDKAL1, E2F3 and SOX4 are highly expressed in patients with the chromosomal 6p22 amplification aside from other six well known genes (ID4, MBOAT1, LINC00340, PRL, and HDGFL1). Based on that, SOX4, E2F3 or 6q22.3 amplifications might represent potential targets in this tumor type. Focusing more in SOX4, it seems to exert its critical regulatory functions upstream of the Snail, Zeb, and Twist family of transcriptional inducers of EMT (epithelial–mesenchymal transition), but without directly affecting their expression as seen in several cell lines of the Cancer Cell Line Encyclopedia (CCLE) project. SOX4 gene expression correlates with advanced cancer stages and poor survival rate in bladder cancer, supporting a potential role as a regulator of the bladder CSC properties. SOX4 might serve as a biomarker of the aggressive phenotype, also underlying progression from NMIBC to MIBC. The amplicon in chromosome 6 contains SOX4 and E2F3 and is frequently found amplified in bladder cancer. These genes/amplicons might be a potential target for therapy. As an existing hypothesis is that chromatin deregulation through enhancers or super-enhancers might be the underlying mechanism responsible of this deregulation, a potential way to target these transcription factors could be through epigenetic modifiers.

Abnormalities in Cell Cycle Control in Cancer and Their Clinical Implications

Recent studies indicate that the functions of several genes that control the cell cycle are altered during the carcinogenic process and that these changes perturb both cell proliferation and genomic stability, thus promoting cell transformation and enhancing the process of tumor progression. The purpose of this paper is to review current information on the role of cyclins and related genes in the control of the mammalian cell cycle, the types of abnormalities in these genes found in human tumors and the possible clinical implications of these findings.

Proteomic analysis of the gamma human papillomavirus type 197 E6 and E7 associated cellular proteins

Gamma HPV197 was the most frequently identified HPV when human skin cancer specimens were analyzed by deep sequencing (Arroyo Muhr et al., Int. J. Cancer 136: 2546-55, 2015). To gain insight into the biological activities of HPV197, we investigated the cellular interactomes of HPV197 E6 and E7. HPV197 E6 protein interacts with a broad spectrum of cellular LXXLL domain proteins, including UBE3A and MAML1. HPV197 E6 also binds and inhibits the TP53 tumor suppressor and interacts with the CCR4-NOT ubiquitin ligase and deadenylation complex. Despite lacking a canonical retinoblastoma (RB1) tumor suppressor binding site, HPV197 E7 binds RB1 and activates E2F transcription. Hence, HPV197 E6 and E7 proteins interact with a similar set of cellular proteins as E6 and E7 proteins encoded by HPVs that have been linked to human carcinogenesis and/or have transforming activities in vitro.

Same difference: A pilot study of cyclin D1, bcl-2, AMACR, and ALDH-1 identifies significant differences in expression between primary colon adenocarcinoma and its metastases

Tumor heterogeneity implies the possibility of significantly different expression of key pathways between primary and metastatic clones. Colon adenocarcinoma is one of the few tumors where current practice includes resection of primary and isolated organ metastases simultaneously without neoadjuvant therapy. We performed a pilot study on 28 cases of colon adenocarcinoma resected simultaneously with metastases in patients with no history of neoadjuvant therapy. We assayed matched primary and metastatic tumors from each patient with common diagnostic antibodies to Bcl-2, Cyclin D1, AMACR, and ALDH-1 by immunohistochemistry with semi-quantitative interpretation on archived formalin fixed, paraffin embedded samples. We were powered for large, consistent differences between primary and metastatic expression, and found 21 of 28 had a significant difference in expression of at least one of the four proteins, accounting for multiplicity of testing. Cyclin D1 had significantly more cases with differential metastatic:primary expression than would be expected by chance alone (p-value 0.0043), favoring higher expression in the metastatic sample. Bcl-2 and ALDH-1 had trends in this direction (p-value 0.078 each). Proportionately more cases with significant differences were identified when a liver metastasis was tested. We conclude differences in expression between metastatic and primary colon adenocarcinoma within the same patient exist, and may have therapeutic and biomarker testing consequences.

G9a promotes proliferation and inhibits cell cycle exit during myogenic differentiation

Differentiation of skeletal muscle cells, like most other cell types, requires a permanent exit from the cell cycle. The epigenetic programming underlying these distinct cellular states is not fully understood. In this study, we provide evidence that the lysine methyltransferase G9a functions as a central axis to regulate proliferation and differentiation of skeletal muscle cells. Transcriptome analysis of G9a knockdown cells revealed deregulation of many cell cycle regulatory genes. We demonstrate that G9a enhances cellular proliferation by two distinct mechanisms. G9a blocks cell cycle exit via methylation-dependent transcriptional repression of the MyoD target genes p21(Cip/Waf1) and Rb1. In addition, it activates E2F1-target genes in a methyltransferase activity-independent manner. We show that G9a is present in the E2F1/PCAF complex, and enhances PCAF occupancy and histone acetylation marks at E2F1-target promoters. Interestingly, G9a preferentially associates with E2F1 at the G1/S phase and with MyoD at the G2/M phase. Our results provide evidence that G9a functions both as a co-activator and a co-repressor to enhance cellular proliferation and inhibit myogenic differentiation.

Cyclin D1 Loss Distinguishes Prostatic Small-Cell Carcinoma from Most Prostatic Adenocarcinomas

PURPOSE

Small-cell neuroendocrine differentiation in prostatic carcinoma is an increasingly common resistance mechanism to potent androgen deprivation therapy (ADT), but can be difficult to identify morphologically. We investigated whether cyclin D1 and p16 expression can inform on Rb functional status and distinguish small-cell carcinoma from adenocarcinoma.

EXPERIMENTAL DESIGN

We used gene expression data and immunohistochemistry to examine cyclin D1 and p16 levels in patient-derived xenografts (PDX), and prostatic small-cell carcinoma and adenocarcinoma specimens.

RESULTS

Using PDX, we show proof-of-concept that a high ratio of p16 to cyclin D1 gene expression reflects underlying Rb functional loss and distinguishes morphologically identified small-cell carcinoma from prostatic adenocarcinoma in patient specimens (n = 13 and 9, respectively). At the protein level, cyclin D1, but not p16, was useful to distinguish small-cell carcinoma from adenocarcinoma. Overall, 88% (36/41) of small-cell carcinomas showed cyclin D1 loss by immunostaining compared with 2% (2/94) of Gleason score 7-10 primary adenocarcinomas at radical prostatectomy, 9% (4/44) of Gleason score 9-10 primary adenocarcinomas at needle biopsy, and 7% (8/115) of individual metastases from 39 patients at autopsy. Though rare adenocarcinomas showed cyclin D1 loss, many of these were associated with clinical features of small-cell carcinoma, and in a cohort of men treated with adjuvant ADT who developed metastasis, lower cyclin D1 gene expression was associated with more rapid onset of metastasis and death.

CONCLUSIONS

Cyclin D1 loss identifies prostate tumors with small-cell differentiation and may identify a small subset of adenocarcinomas with poor prognosis. Clin Cancer Res; 21(24); 5619-29. ©2015 AACR.

6p22.3 amplification as a biomarker and potential therapeutic target of advanced stage bladder cancer

Genetic and epigenetic alterations have been identified as to contribute directly or indirectly to the generation of transitional cell carcinoma of the urinary bladder (TCC-UB). In a comparative fashion much less is known about copy number alterations in TCC-UB, but it appears that amplification of chromosome 6p22 is one of the most frequent changes. Using fluorescence in situ hybridization (FISH) analyses, we evaluated chromosomal 6p22 amplification in a large cohort of bladder cancer patients with complete surgical staging and outcome data. We have also used shRNA knockdown candidate oncogenes in the cell based study. We found that amplification of chromosome 6p22.3 is significantly associated with the muscle-invasive transitional cell carcinoma of the urinary bladder (TCC-UB) (22%) in contrast to superficial TCC-UB (9%) (p=7.2-04). The rate of 6p22.3 amplification in pN>1 patients (32%) is more than twice that in pN0 (16%) patients (p=0.05). Interestingly, we found that 6p22.3 amplification is as twice as high (p=0.0201) in African American (AA) than European American (EA) TCC-UB patients. Moreover, we showed that the expression of some candidate genes (E2F3, CDKAL1 and Sox4) in the 6p22.3 region is highly correlated with the chromosomal amplification. In particular, knockdown of E2F3 inhibits cell proliferation in a 6p22.3-dependent manner, whereas knockdown of CDKAL1 and Sox4 has no effect on cell proliferation. Using gene expression profiling, we further identified some common as well as distinctive subset targets of the E2F3 family members. In summary, our data indicate that E2F3 is a key regulator of cell proliferation in a subset of bladder cancer and the 6p22.3 amplicon is a biomarker of aggressive phenotype in this tumor type.

Therapeutic effect of c-Jun N-terminal kinase inhibition on pancreatic cancer

c-Jun N-terminal kinase (JNK) is a member of the mitogen-activated protein kinase (MAPK) family, and it is reportedly involved in the development of several cancers. However, the role of JNK in pancreatic cancer has not been elucidated. We assessed t he involvement of JNK in the development of pancreatic cancer and investigated the therapeutic effect of JNK inhibitors on this deadly cancer. Small interfering RNAs against JNK or the JNK inhibitor SP600125 were used to examine the role of JNK in cellular proliferation and the cell cycles of pancreatic cancer cell lines. Ptf1a(cre/+) ;LSL-Kras(G12D/+) ;Tgfbr2(flox/flox) mice were treated with the JNK inhibitor to examine pancreatic histology and survival. The effect of JNK inhibition on tumor angiogenesis was also assessed using cell lines and murine pancreatic cancer specimens. JNK was frequently activated in human and murine pancreatic cancer in vitro and in vivo. Growth of human pancreatic cancer cell lines was suppressed by JNK inhibition through G1 arrest in the cell cycle with decreased cyclin D1 expression. In addition, oncogenic K-ras expression led to activation of JNK in pancreatic cancer cell lines. Treatment of Ptf1a(cre/+) ;LSL-Kras(G12D/+) ;Tgfbr2(flox/flox) mice with the JNK inhibitor decreased growth of murine pancreatic cancer and prolonged survival of the mice significantly. Angiogenesis was also decreased by JNK inhibition in vitro and in vivo. In conclusion, activation of JNK promotes development of pancreatic cancer, and JNK may be a potential therapeutic target for pancreatic cancer.

Clinical implications of deregulated CDK4 and Cyclin D1 expression in patients with human hepatocellular carcinoma

Deregulated cell cycle can contribute to the unscheduled proliferation in cancer cells. Overexpression of cell cycle regulators CDK4 and Cyclin D1 has been reported in many cancers. The aim of this study is to determine the clinical implications of CDK4 and Cyclin D1 in hepatocellular carcinoma (HCC). The levels of mRNA and protein were analyzed by quantitative real-time RT-PCR and immunohistochemistry, respectively, in 59 paired HCC and the neighboring noncancer tissues. The relationship between CDK4 and Cyclin D1 expression, clinicopathological parameters, and prognosis was investigated. Our data demonstrated that the mRNA level of CDK4 was up-regulated (p = 0.019), while that of Cyclin D1 was down-regulated (p = 0.002), in HCC. Immunohistochemical data confirmed that CDK4 protein was increased in 73 % and Cyclin D1 protein was decreased in 66 % of HCC samples. Overexpression of CDK4 was correlated with HBV (p = 0.054, borderline significant), tumor size (p = 0.014), and stage (p = 0.010). The Kaplan-Meier survival curves showed that high CDK4 was correlated with a poor survival rate (I vs. II, p < 0.001; I vs. III, p < 0.001). Univariate analysis showed that tumor size (p = 0.002), stage (p = 0.021), and high CDK4 score (I vs. II-III, p < 0.001) were significant prognostic factors. Multivariate analysis showed that tumor size (p = 0.007) and high CDK4 score (I vs. II-III, p < 0.001) were independent factors for overall survival of HCC. The expression of Cyclin D1 was not correlated with CDK4 expression, tumor grades, survival rate, and any clinicopathological parameters. CDK4 could provide a clinical prognostic marker for HCC progression.

Cyclin D1 overexpression supports stable EBV infection in nasopharyngeal epithelial cells

Undifferentiated nasopharyngeal carcinomas (NPCs) are commonly present with latent EBV infection. However, events regulating EBV infection at early stages of the disease and the role of EBV in disease pathogenesis are largely undefined. Genetic alterations leading to activation of cyclin D1 signaling in premalignant nasopharyngeal epithelial (NPE) cells have been postulated to predispose cells to EBV infection. We previously reported that loss of p16, a negative regulator of cyclin D1 signaling, is a frequent feature of NPC tumors. Here, we report that early premalignant lesions of nasopharyngeal epithelium overexpress cyclin D1. Furthermore, overexpression of cyclin D1 is closely associated with EBV infection. Therefore we investigated the potential role of cyclin D1 overexpression in dysplastic NPE cells in vitro. In human telomerase reverse transcriptase-immortalized NPE cells, overexpression of cyclin D1 or a p16-resistant form of CDK4 (CDK4(R24C)) suppressed differentiation. This suppression may have implications for the close association of EBV infection with undifferentiated NPC. In these in vitro models, we found that cellular growth arrest and senescence occurred in EBV-infected cell populations immediately after infection. Nevertheless, overexpression of cyclin D1 or a p16-resistant form of CDK4 or knockdown of p16 in the human telomerase reverse transcriptase-immortalized NPE cell lines could counteract the EBV-induced growth arrest and senescence. We conclude that dysregulated expression of cyclin D1 in NPE cells may contribute to NPC pathogenesis by enabling persistent infection of EBV.

Role of cyclin D1 amplification and expression in vulvar carcinomas

Cyclin D1 (CCND1) belongs to the family of D-type cyclins involved in cell cycle progression, transcriptional regulation, and cell migration. CCND1 was found to be amplified and overexpressed in a variety of cancers, including some vulvar carcinoma cell lines. To determine the relationship of CCND1 copy number changes and CCND1 protein expression with clinicopathologic features and prognosis, 183 vulvar carcinomas were analyzed on a tissue microarray. Amplification was observed in 32 (22.4%) vulvar cancer specimens and was statistically related to the presence of regional lymph node metastases (P < .001). Detectable CCND1 expression was found in 139 (83.2%) of vulvar carcinomas, and 76 (45.5%) exhibited a moderate or strong expression. Increased levels of CCND1 expression were significantly related to higher patient age (P = .013), positive pN category (P = .004), and negative human papillomavirus status (P < .001). Basaloid as well as verrucous, warty-type, and mixed vulvar carcinomas showed lower CCND1 expression levels than keratinizing or nonkeratinizing tumors (P < .001 and P = .032, respectively). Elevated CCND1 expression levels and amplification of the CCND1 gene were closely connected in the present analysis (P < .001). Patient prognosis was independent from CCND1 amplification status and expression level (P = .57 each). In conclusion, CCND1 is amplified and overexpressed in a substantial proportion of vulvar carcinomas and associated with the occurrence of locoregional lymph node metastases, especially in human papillomavirus-negative tumors.

The cyclins: a family of widely expressed tumor antigens?

Continuous cell division is a hallmark of cancer and cell-cycle regulators therefore represent relevant target molecules for tumor therapy. Among these targets the cyclins are of particular interest as they are overexpressed in various tumor entities with little expression in normal tissue. Here we review evidence that these molecules are recognized by the immune system, summarize why cyclins A, B and D in particular appear to be interesting targets for active and passive immunotherapy, and discuss whether the entire family could be an interesting novel class of tumor antigens for cancer treatment and prevention.

Synergistic effect of low-dose cucurbitacin B and low-dose methotrexate for treatment of human osteosarcoma

We investigated the use of cucurbitacin B, a plant-derived tetracyclic triterpenoid, as a single agent or in combination with methotrexate (MTX) for human osteosarcoma (OS) treatment. Cucurbitacin B showed antiproliferative activity against seven human OS cell lines in vitro accompanying G2/M cell cycle arrest, apoptosis, and inhibition of ERK, Akt, and mTOR proteins. Cucurbitacin B in combination with MTX synergistically inhibited OS cell growth in vitro. Low-dose cucurbitacin B (LD-CuB, 0.5 mg/kg body weight) or low-dose MTX (LD-MTX, 150 mg/kg) failed to decrease the size of human OS xenografts in nude mice. However, combined therapy at identical concentrations inhibited tumor growth by 62% vs. LD-CuB and 81% vs. LD-MTX (p<0.001). Strikingly, the effect persisted even when the dose of MTX was decreased by two thirds (VLD-MTX, 50 mg/kg). In conclusion, cucurbitacin B alone or in combination with MTX shows promising antiproliferative activity against human OS.

Apoptosis signal-regulating kinase 1 and cyclin D1 compose a positive feedback loop contributing to tumor growth in gastric cancer

Mitogen-activated protein kinase (MAPK) pathways regulate multiple cellular functions and are highly active in many types of human cancers. Apoptosis signal-regulating kinase 1 (ASK1) is an upstream MAPK involved in apoptosis, inflammation, and carcinogenesis. This study investigated the role of ASK1 in the development of gastric cancer. In human gastric cancer specimens, we observed increased ASK1 expression, compared to nontumor epithelium. Using a chemically induced murine gastric tumorigenesis model, we observed increased tumor ASK1 expression, and ASK1 knockout mice had both fewer and smaller tumors than wild-type (WT) mice. ASK1 siRNA inhibited cell proliferation through the accumulation of cells in G1 phase of the cell cycle, and reduced cyclin D1 expression in gastric cancer cells, whereas these effects were uncommon in other cancer cells. ASK1 overexpression induced the transcription of cyclin D1, through AP-1 activation, and ASK1 levels were regulated by cyclin D1, via the Rb-E2F pathway. Exogenous ASK1 induced cyclin D1 expression, followed by elevated expression of endogenous ASK1. These results indicate an autoregulatory mechanism of ASK1 in the development of gastric cancer. Targeting this positive feedback loop, ASK1 may present a potential therapeutic target for the treatment of advanced gastric cancer.

The neuronal pentraxin II gene (NPTX2) inhibit proliferation and invasion of pancreatic cancer cells in vitro

The neuronal pentraxin II gene (NPTX2) is expressed in numerous tissues, such as the pancreas and the liver. While its activity in the brain is known to be regulated by neuronal activity, its function in the pancreas is unclear. In this study, we investigated the impact of NPTX2 on the proliferation, migration, invasion, apoptosis, and cell cycle of the pancreatic cancer cells. The expression levels of NPTX2 and their relation to the methylation level of the NPTX2 gene promoter in five pancreatic cancer cell lines were observed. The lower expression of NPTX2 in the cells was restored after the treatment of DNA methyltransferase inhibitor (5-aza-2'-deoxycytidine). Additionally, a full-length NPTX2 cDNA was transfected into pancreatic cancer cells (PANC-1) and we obtained the stably transfected cells (PANC-1-NPTX2). The ectopic NPTX2 expression significantly promoted G0-G1 arrest and cell apoptosis, and reduced cell proliferation, migration and invasion. Notably, the pro-apoptotic gene bax expression was significantly up-regulated while pro-survival gene bcl-2 did not significantly change in the stably transfected cells. Meanwhile, Cyclin D1 was significantly down-regulated. This study suggests that NPTX2, as a tumor-suppressor, plays an anti-tumor effect on pancreatic cancer and its low expression, due to promoter hypermethylation, may play a role in the tumorigenesis of pancreatic cancer.

The interaction of the gammaherpesvirus 68 orf73 protein with cellular BET proteins affects the activation of cell cycle promoters

Infection of mice with murine gammaherpesvirus 68 (MHV-68) provides a valuable animal model for gamma-2 herpesvirus (rhadinovirus) infection and pathogenesis. The MHV-68 orf73 protein has been shown to be required for the establishment of viral latency in vivo. This study describes a novel transcriptional activation function of the MHV-68 orf73 protein and identifies the cellular bromodomain containing BET proteins Brd2/RING3, Brd3/ORFX, and BRD4 as interaction partners for the MHV-68 orf73 protein. BET protein members are known to interact with acetylated histones, and Brd2 and Brd4 have been implicated in fundamental cellular processes, including cell cycle regulation and transcriptional regulation. Using MHV-68 orf73 peptide array assays, we identified Brd2 and Brd4 interaction sites in the orf73 protein. Mutation of one binding site led to a loss of the interaction with Brd2/4 but not the retinoblastoma protein Rb, to impaired chromatin association, and to a decreased ability to activate the BET-responsive cyclin D1, D2, and E promoters. The results therefore pinpoint the binding site for Brd2/4 in a rhadinoviral orf73 protein and suggest that the recruitment of a member of the BET protein family allows the MHV-68 orf73 protein to activate the promoters of G(1)/S cyclins. These findings point to parallels between the transcriptional activator functions of rhadinoviral orf73 proteins and papillomavirus E2 proteins.

Prognostic value of the apoptotic index analysed jointly with selected cell cycle regulators and proliferation markers in non-small cell lung cancer

In a previous small series of surgically treated non-small cell lung cancer patients (NSCLC), we found that higher apoptotic index (AI) negatively influenced survival (Dworakowska D, Jassem E, Jassem J, Karmolinski A, Dworakowski R, Wirth T, et al. Clinical significance of apoptotic index in non-small cell lung cancer: correlation with p53, mdm2, pRb and p21WAF1/CIP1 protein expression. J Cancer Res Clin Oncol 2005; 131:617-623.). In this study we attempted to verify our previous finding in larger group of 170 NSCLC cases, additionally correlating AI to selected cell cycle regulators as well as a proliferation marker. Apoptosis was assessed with the use of the TUNEL technique, whereas the expression of p53, pRb, mdm2, p21(WAF1/CIP1), cyclin D1 and PCNA were assessed immunohistochemically. The mean and the median AI was 12 and 8, respectively. The expression of p53, pRb, mdm2, p21(WAF1/CIP1) proteins and cyclin D1 was found in 47%, 71%, 37%, 65% and 40% of cases, respectively. The mean and the median PCNA labeling index (PCNA LI) was 34 and 35, respectively. AI was not correlated with any patient characteristic or other tumor markers. In uni- and multivariate analysis AI, analysed separately or jointly with cell cycle regulators and PCNA LI, did not influence disease-free or over-all survival. However, patients with "very high AI/very high PCNA LI" had a particularly poor prognosis (P=0.001). Patients with "very low AI/negative pRb" phenotype survived for a shorter time in comparison to others (P=0.04). In addition, patients with the highest PCNA LI had a worse outcome in comparison to patients with the lowest PCNA LI (P=0.04), especially those with concomitant p53 protein expression (P=0.026) or lacking pRb protein expression (P=0.04). This study demonstrates that joint analysis of several factors involved in apoptosis, proliferation and cell cycle regulation, but not AI alone, might provide additional prognostic information in NSCLC patients.

Cyclin D1-specific cytotoxic T lymphocytes are present in the repertoire of cancer patients: implications for cancer immunotherapy

PURPOSE

Cyclin D1, a key cell cycle regulator, is overexpressed in multiple types of cancer. Such tumor-associated genes may be useful targets for cancer immunotherapy. Nevertheless, it had previously been suggested that efficient T cells recognizing cyclin D1-derived epitopes are absent from the repertoire because of thymic deletion. We attempted to induce autologous CTL from healthy donors and patients with cyclin D1-overexpressing tumors using a highly efficient T-cell expansion system based on CD40-activated B cells as antigen-presenting cells.

EXPERIMENTAL DESIGN

Cyclin D1-derived, HLA-A*0201-restricted epitopes were predicted by multiple computer algorithms, screened in HLA-A2-binding assays, and used for T-cell stimulation. The generated CTL lines and clones were analyzed by IFN-gamma enzyme-linked immunosorbent spot assay or cytolysis assay.

RESULTS

After screening, at least two naturally processed and presented HLA-A*0201-binding cyclin D1 epitopes were identified. CTL specific for these epitopes could be successfully generated from HLA-A2(+) donors. T cells efficiently recognized target cells pulsed with the cognate peptide and cyclin D1-expressing tumor cell lines in an HLA-A*0201-restricted manner. More importantly, HLA-A*0201-matched, primary cyclin D1(+) tumor cells were efficiently recognized by cyclin D1-specific CTL. These CTL could be generated from patients with mantle cell lymphoma and cyclin D1(+) colon cancer.

CONCLUSIONS

These results underscore that cyclin D1 needs to be considered as a target for broad-based antitumor immunotherapy.

RASSF1A expression inhibits the growth of hepatocellular carcinoma from Qidong County

BACKGROUND AND AIM

The tumor-suppressing role of Ras-association domain family 1A (RASSF1A) has been described in several systems. In this study, we tested its tumor-suppressing ability and the potential molecular mechanisms in hepatocellular carcinoma (HCC) from Qidong County.

METHODS

Reverse transcription polymerase chain reaction and Northern blotting were employed to detect the expression of RASSF1A in HCC. After establishing stable RASSF1A (wild type or mutant) expressing 'qi dong gan ai yan jiu suo' ([Qidong Institute of Liver Cancer] QGY)-7703 cell lines, we tested the effects of RASSF1A expression on cell growth by cell proliferation rate, cell colony formation, and cell cycle progression. We also tested the effects of RASSF1A expression on tumorigenesis in nude mice and on cellular sensitivity to mitomycin treatment.

RESULTS

The RASSF1A transcript was not found in 75% (three of four) of HCC cell lines and 67% (32/48) of HCC primary biopsies. The stepwise regression analyses indicated that the loss of RASSF1A expression was more frequent in patients who were hepatitis B virus surface antigen positive (HBsAg+) compared to those who were HBsAg(-), both in tumor and corresponding non-cancerous tissues. The wild-type (wt)-RASSF1A expression in the QGY-7703 cell line resulted in fewer and smaller clones, decreased xenograft tumor volume and weight, and G(1)/S arrest in vitro and in vivo. The wt-RASSF1A expression also decreased the cyclin D1 protein expression, which appeared to be at the level of post-transcriptional control. In addition, the wt-RASSF1A expression increased cell growth inhibition and the percentage of cells with sub-G(1) DNA content when the cells were treated with mitomycin.

CONCLUSION

RASSF1A is a tumor suppressor in HCC. The loss of RASSF1A expression may be related to HBsAg+ in hepatocarcinogenesis. Its inactivation may play an important role in the development of HCC.

Comparative genomic hybridization analysis of newly established retinoblastoma cell lines of adherent growth compared with Y79 of nonadherent growth

Retinoblastoma (RB) shows cytogenetic aberrations involving genes other than RB gene located on 13q14. We analyzed genomic aberration in newly established RB cell lines SNUOT-RB1 and SNUOT-RB4 of adherent growth and Y79 cell line of nonadherent growth by microarray comparative genomic hybridization. SNUOT-RB1 showed 44 significant copy number changes (gain in 11 and loss in 33, P<0.0005). SNUOT-RB4 showed 42 significant copy number changes (gain in 8 and loss in 34, P<0.0005). Y79 cell line had the greatest gain of 19.65-fold in the locus of MYCN gene 2p24.1, whereas SNUOT-RB1 and SNUOT-RB4 showed no significant gain. SNUOT-RB1 and SNUOT-RB4 gained chromosomal copy numbers commonly in chromosome 11, especially in locus 11q13, which is responsible for cancer-related genes such as CCND1, MEN1, and FGF3. Losses of copy numbers occurred in chromosomes 3, 9, 10, 11, 16, and 17. In summary, SNUOT-RB1 and SNUOT-RB4 represented similar pattern in gain and loss of chromosomal copy number changes, while different from Y79. The loss of CYLD gene of tumor suppressor gene, 16q12-q13, was only on locus of common involvement in 3 cell lines.

Involvement of cyclins in mammalian spermatogenesis

Mammalian spermatogenesis is a complicated developmental process by which undifferentiated germ cells continuously produce mature sperm throughout a lifetime. Stringent control of the cell cycle during spermatogenesis is required to ensure self-renewal of male germ line cells and differentiation of appropriate numbers of cells for the various lineages. Cyclins are key factors of cell cycle regulation and play crucial roles in governing both the mitotic and meiotic divisions that characterize spermatogenesis. Abnormal expression of some types of cyclins in the testes can induce apoptosis, infertility, testicular tumors, and other problems related to spermatogenesis in mammals. In this review, available data regarding cellular and molecular regulation of several different types of cyclins during mammalian spermatogenesis are collected and further discussed.

Expression of cell cycle associated proteins influences radiocurability of T2N0 squamous cell carcinoma of the larynx

Cell cycle modulators are important in carcinogenesis and may be of prognostic and therapeutic relevance. This study has examined the influence of the proliferation index (Ki-67) and immunocytochemical expression of epidermal growth factor receptor (EGFR), cyclin D1, and retinoblastoma protein on recurrence rates at the primary site in 50 patients with T2N0 laryngeal carcinomas treated with radical irradiation. Pre-treatment biopsies were retrieved and sections scored for the four immunocytochemical markers. Statistical analysis for association, interaction and survival was performed. Five cases showed loss of expression of Rb protein. The median Ki-67 index was 50%, the median cyclin D1 index 21% and the median EGFR index 47% of cells. EGFR and cyclin D1 expression were positively correlated and, whilst local recurrence tended to occur with a Ki-67 labelling index of <50%, this was not statistically significant. When interactions were examined using Multiple Logistic Regression it was found that there was a direct relationship between EGFR and cyclin D1 expression. If the EGFR index was >20% and the cyclin D1 index >10%, then the odds ratio in favour of a primary site recurrence was very high (5.32 +/-0.41). This study demonstrates that the relationship between EGFR index and cyclin D1 index has a very strong association with primary site recurrence for T2 N0 laryngeal carcinomas treated by irradiation.

Expression and prognostic significance of cyclin D3 in ovarian adenocarcinomas

Abnormal expression of cell cycle regulators may contribute to malignant transformation. However, the clinical significance of the expression of cyclin D3 in ovarian cancer remains undefined. We therefore conducted a retrospective investigation to address the role of this cell-cycle protein in this tumor. In our study, paraffin-embedded tissue from 109 nonbenign epithelial ovarian tumors, including 17 tumors of low malignant potential and 92 primary adenocarcinomas, was stained immunohistochemically for cyclin D3. Most of the cases had previously been stained for pRb, p21Cip1, p27Kip1, p53, and Ki-67 antigen. Expression of cyclin D3 was correlated with clinicopathologic features, the expression of other cell cycle regulators, and postoperative survival of patients. Cyclin D3 levels were significantly higher in tumors of low malignant potential than in adenocarcinomas (P = 0.0002). In the latter group, cyclin D3 expression decreased with increasing grade (P = 0.0004) and advancing stage (P = 0.0315). Cyclin D3 expression positively correlated with pRb, p21Cip1, and p27Kip1 levels (P = 0.0021; P = 0.0036; P < 0.0001, respectively) and negatively with p53 and Ki-67 (P = 0.0003; P < 0.0001). Absent cyclin D3 expression was an important indicator of poor survival in univariate analysis in the entire cohort (P > 0.00010) and in the platinum-treated patients (P = 0.001) and in multivariate analysis (P = 0.044). Our results demonstrate that absent or decreased cyclin D3 expression is adversely related to several clinicopathologic indicators of aggressiveness in ovarian adenocarcinomas and is combined with a better prognosis, suggesting that cyclin D3 may have a biological role distinct from that of other G1 cyclins which is possibly regulated through interaction with other cell cycle genes.

Molecular mechanisms of liver carcinogenesis in the mdr2-knockout mice

Mouse models of hepatocellular carcinoma (HCC) simulate specific subgroups of human HCC. We investigated hepatocarcinogenesis in Mdr2-knockout (Mdr2-KO) mice, a model of inflammation-associated HCC, using gene expression profiling and immunohistochemical analyses. Gene expression profiling showed that although Mdr2-KO mice differ from other published murine HCC models, they share several important deregulated pathways and many coordinately differentially expressed genes with human HCC data sets. Analysis of genome positions of differentially expressed genes in liver tumors revealed a prolonged region of down-regulated genes on murine chromosome 8 in three of the six analyzed tumor samples. This region is syntenic to human chromosomal regions that are frequently deleted in human HCC and harbor multiple tumor suppressor genes. Real-time reverse transcription-PCR analysis of 16 tumor samples confirmed down-regulation of several tumor suppressors in most tumors. We show that in the aged Mdr2-KO mice, cyclin D1 nuclear level is increased in dysplastic hepatocytes that do not form nodules; however, it is decreased in most dysplastic nodules and in liver tumors. We found that this decrease is mostly at the protein, rather than the mRNA, level. These findings raise the question on the role of cyclin D1 at early stages of hepatocarcinogenesis in the Mdr2-KO HCC model. Furthermore, we show that most liver tumors in Mdr2-KO mice were characterized by the absence of beta-catenin activation. In conclusion, the Mdr2-KO mouse may serve as a model for beta-catenin-negative subgroup of human HCCs characterized by low nuclear cyclin D1 levels in tumor cells and by down-regulation of multiple tumor suppressor genes.

Identifying the estrogen receptor coactivator PELP1 in autophagosomes

Resveratrol, a well-established phytoestrogen and chemopreventive agent, has gained much attention among oncologists because it can act as both estrogen receptor agonist and antagonist, depending on dosage and cell context. It is increasingly accepted that steroidal receptor coregulators may also function in the cytoplasmic compartment. Deregulation and altered localization of these coregulators could influence target gene expression and participate in the development of hormone-responsive cancers. Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1), a novel estrogen receptor (ER) coactivator, plays an important role in the genomic and nongenomic actions of ER. Furthermore, recent studies have shown that differential compartmentalization of PELP1 could be crucial in modulating sensitivity to tamoxifen. In this study, we investigated the role of PELP1 in resveratrol-induced autophagy in lung cancer and salivary gland adenocarcinoma cell lines. Resveratrol reversibly inhibited the growth of these cancer cell lines and induced autophagy, as evidenced by microtubule-associated protein 1 light chain 3 (LC3) up-regulation in a time-dependent and 3-methyladenine-sensitive manner. Confocal microscopic analysis showed that resveratrol induced PELP1 accumulation in autophagosomes with green fluorescent protein-LC3. The intermediary molecule involved in PELP1 accumulation in resveratrol-induced autophagosomes is hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a trafficking molecule that binds to PELP1. These results identify PELP1 for the first time in autophagosomes, implying that both PELP1 and HRS reallocate to autophagosomes in response to resveratrol treatment, which might be important in the process of autophagy in the cancer cells.

Aberrant expression of the Rb pathway proteins in soft tissue sarcomas

Cell cycle regulation depends on a fine balance between cyclins, cyclin-dependent kinases (CDKs), and cyclin-dependent kinase inhibitors (CKIs) that block the cycle progression. Alterations of the cell cycle regulators are a common feature of many malignant tumors, and some have been shown to have prognostic significance. In this study, 152 cases of different types of soft tissue sarcomas were evaluated for alterations of cell cycle regulator proteins that control the cell cycle progression from G1 to S phase and govern the Rb pathway. Immunohistochemical stains for proteins Rb, E2F1, cyclin D1, CDK4, CDK6, p16, and p27 were carried out on tissue microarrays. The relationship between the expression of these proteins and the histologic grade of the sarcomas was assessed. Altered expression for Rb and p16 proteins was identified in 67.8% and 65.1% of the cases, respectively. Overexpression of E2F1, cyclin D1, CDK4, and CDK6 was detected in 50.7%, 24.3%, 92.1%, and 10.5%, respectively. Overexpression of E2F1 was associated with altered expression of Rb protein. Overexpression of cyclin D1, CDK4, and CDK6 showed an association with normal Rb expression. CDK6 expression revealed a positive correlation with the histologic grade of the sarcoma, and p27 expression was inversely correlated with sarcoma grade. These results suggest that alterations of the Rb pathway proteins are common in soft tissue sarcomas and may participate in their tumorigenesis. CDK6 and p27 showed correlation with the histologic grade of the sarcomas, suggesting that these proteins could be used as prognostic markers.

Cell cycle-controlled interaction of nucleolin with the retinoblastoma protein and cancerous cell transformation

Retinoblastoma protein (Rb) is a multifunctional tumor suppressor, frequently inactivated in certain types of human cancer. Nucleolin is an abundant multifunctional phosphoprotein of proliferating and cancerous cells, recently identified as cell cycle-regulated transcription activator, controlling expression of human papillomavirus type 18 (HPV18) oncogenes in cervical cancer. Here we find that nucleolin is associated with Rb in intact cells in the G1 phase of the cell cycle, and the complex formation is mediated by the growth-inhibitory domain of Rb. Association with Rb inhibits the DNA binding function of nucleolin and in consequence the interaction of nucleolin with the HPV18 enhancer, resulting in Rb-mediated repression of the HPV18 oncogenes. The intracellular distribution of nucleolin in epithelial cells is Rb-dependent, and an altered nucleolin localization in human cancerous tissues results from a loss of Rb. Our findings suggest that deregulated nucleolin activity due to a loss of Rb contributes to tumor development in malignant diseases, thus providing further insights into the molecular network for the Rb-mediated tumor suppression.

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.

Altered expression of cell cycle regulatory proteins in gastrointestinal stromal tumors: markers with potential prognostic implications

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the digestive tract. The prediction of the malignant potential of GISTs is still difficult. Altered cell cycle regulation may underlie the tumorigenesis and/or the progression of human malignancies. Although p53 and Bcl-2 have been extensively investigated in GISTs, little is known about the frequency of expression and possible clinical implications of alterations of other cell cycle regulatory proteins in these neoplasms. We have previously investigated the role of loss of p16(INK4A) by loss of heterozygosity and immunohistochemistry in the progression of GISTs and found that loss of heterozygosity of 9p and loss of p16 expression are confined to malignant GISTs. This has led us to investigate the role of other cell cycle regulatory proteins in these tumors. Twenty-three cases of GIST (9 low malignant potential [LMP], 10 primary malignant, and 4 intra-abdominal recurrences) were examined. All cases were strongly positive for KIT (CD117). Immunohistochemical stains were carried out on tissue microarrays to evaluate the expression of proteins involved in the G(1)-S transition and proteins that regulate apoptosis including Rb, E2F1, cyclin D1, CDK4, CDK6, p27(KIP1), p21(WAF1/CIP1), p53, Mdm2, Bcl-2, and Bax. The positive phenotypes identified were as follows: Rb, 39.1%; E2F1, 69.6%; cyclin D1, 30.4%; CDK4, 100%; CDK6, 30.4%; 39.1%; p27(KIP1), 47.8%; p21(WAF1/CIP1), 39.1%; p53, 43.5%; Mdm2, 17.4%; Bcl-2, 91.3%; and Bax, 100%. Malignant GISTs are more likely to be associated with a positive E2F1 and p53 phenotype and a negative p16 and p27(KIP1) phenotype. It was concluded that aberration of the cell cycle regulators is a frequent finding and may be a contributing factor to the pathogenesis of GISTs. While some alterations are seen in LMP and malignant GISTs and therefore may represent an early event in molecular tumorigenesis of GISTs, other alterations are more common in malignant GISTs than LMP and therefore have potential utility as complementary tools for the prognostication of GISTs.

Differential disruption of cell cycle pathways in small cell and non-small cell lung cancer

Lung cancer is the leading cause of cancer-related mortality in the world, with small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) comprising the two major cell types. Although these cell types can be distinguished readily at the histological level, knowledge of their underlying molecular differences is very limited. In this study, we compared 14 SCLC cell lines against 27 NSCLC cell lines using an integrated array comparative genomic hybridisation and gene expression profiling approach to identify subtype-specific disruptions. Using stringent criteria, we have identified 159 of the genes that are responsible for the different biology of these cell types. Sorting of these genes by their biological functions revealed the differential disruption of key components involved in cell cycle pathways. Our novel comparative combined genome and transcriptome analysis not only identified differentially altered genes, but also revealed that certain shared pathways are preferentially disrupted at different steps in these cell types. Small cell lung cancer exhibited increased expression of MRP5, activation of Wnt pathway inhibitors, and upregulation of p38 MAPK activating genes, while NSCLC showed downregulation of CDKN2A, and upregulation of MAPK9 and EGFR. This information suggests that cell cycle upregulation in SCLC and NSCLC occurs through drastically different mechanisms, highlighting the need for differential molecular target selection in the treatment of these cancers.

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.

Mammalian target of rapamycin (mTOR) regulates both proliferation of megakaryocyte progenitors and late stages of megakaryocyte differentiation

A major determinant in platelet production is the megakaryocyte (MK) size that is regulated both by ploidization and the increase in cytoplasmic volume at the end of maturation. Here we investigated the involvement of the mammalian target of rapamycin (mTOR) pathway in the regulation of megakaryopoiesis. We show that phosphorylation of mTOR, p70S6K1, and 4E-BP1 was diminished in thrombopoietin-cultured human MKs after rapamycin treatment. Rapamycin induced an inhibition in the G1/S transition and a decrease in the mean MK ploidy via a diminution of p21 and cyclin D3 occurring at a transcriptional level. Both cycling (2N/4N) and polyploid (8N/16N) MKs were reduced in size, with a size reduction slightly more pronounced in mature polyploid MKs than in immature ones. Rapamycin also induced a delay in the expression of MK markers and prevented the generation of proplatelet MKs. Additional experiments performed in vitro with MKs from mutant mice showed that the decrease in mean ploidy level and the delay in MK differentiation in the presence of rapamycin were less pronounced in CdknIa (p21)–/– MKs than in CdknIa (p21)+/+ MKs. These findings indicate that the mTOR pathway plays an important role during megakaryopoiesis by regulating ploidy, cell size, and maturation, in part by regulating p21 and cyclin D3.

Sleeping Beauty transposase modulates cell-cycle progression through interaction with Miz-1

We used the Sleeping Beauty (SB) transposable element as a tool to probe transposon-host cell interactions in vertebrates. The Miz-1 transcription factor was identified as an interactor of the SB transposase in a yeast two-hybrid screen. Through its association with Miz-1, the SB transposase down-regulates cyclin D1 expression in human cells, as evidenced by differential gene expression analysis using microarray hybridization. Down-regulation of cyclin D1 results in a prolonged G(1) phase of the cell cycle and retarded growth of transposase-expressing cells. G(1) slowdown is associated with a decrease of cyclin D1/cdk4-specific phosphorylation of the retinoblastoma protein. Both cyclin D1 down-regulation and the G(1) slowdown induced by the transposase require Miz-1. A temporary G(1) arrest enhances transposition, suggesting that SB transposition is favored in the G(1) phase of the cell cycle, where the nonhomologous end-joining pathway of DNA repair is preferentially active. Because nonhomologous end-joining is required for efficient SB transposition, the transposase-induced G(1) slowdown is probably a selfish act on the transposon's part to maximize the chance for a successful transposition event.

Array-based comparative genomic hybridization analysis identified cyclin D1 as a target oncogene at 11q13.3 in nasopharyngeal carcinoma

Nasopharyngeal carcinoma is highly prevalent in Southern China and Southeast Asia. To unveil the molecular basis of this endemic disease, high-resolution comparative genomic hybridization arrays were used for systematic investigation of genomic abnormalities in 26 nasopharyngeal carcinoma samples. A comprehensive picture of genetic lesions associated with tumorigenesis of nasopharyngeal carcinoma was generated. Consistent chromosomal gains were frequently found on 1q, 3q, 8q, 11q, 12p, and 12q. High incidences of nonrandom losses were identified on chromosomes 3p, 9p, 11q, 14q, and 16q. In addition to previously characterized regions, we have identified several novel minimal regions of gains, including 3q27.3-28, 8q21-24, 11q13.1-13.3, and 12q13, which may harbor candidate nasopharyngeal carcinoma-associated oncogenes. In this study, gain of 11q13.1-13.3 was the most frequently detected chromosomal aberration and a 5.3-Mb amplicon was delineated at this region. Within this 11q13 amplicon, concordant amplification and overexpression of cyclin D1 (CCND1) oncogene was found in nasopharyngeal carcinoma cell lines, xenografts, and primary tumors. Knockdown of cyclin D1 by small interfering RNA in nasopharyngeal carcinoma cell lines led to significant decrease of cell proliferation. The findings suggest that cyclin D1 is a target oncogene at 11q13 in nasopharyngeal carcinoma and its activation plays a significant role in nasopharyngeal carcinoma tumorigenesis.

Combined expression of p53, cyclin D1 and epidermal growth factor receptor improves estimation of prognosis in curatively resected oral cancer

p53, cyclin D1 and epidermal growth factor receptor (EGFR) are molecular markers that regulate the cell cycle or cell growth and play important roles in tumor development and progression. In this study, we examined the impact of immunohistochemical expression of these markers on tumor progression in 140 oral cancers. p53, cyclin D1 and EGFR were expressed in 64 cases (46%), 54 cases (39%) and 54 cases (39%), respectively, but there was no inter-relationship between any two of these markers. In the association of these markers with clinicopathological features, EGFR expression alone was significantly associated with poor differentiation (P=0.0008) and invasive growth pattern (P=0.0003). Any of these markers, including EGFR, had no significant impact on survival. Coexpression of all these markers, however, was significantly associated with invasive growth pattern (P=0.0149) and shortened survival (P=0.0181), and was a significant and independent unfavorable prognostic factor (P=0.0002), along with tumor size (P=0.0040), nodal metastasis (P=0.0137) and growth pattern (P=0.0017) in a multivariate analysis. Simultaneous coexpression of these markers in oral cancers might prove to be a useful indicator for identification of low- or high-risk patients.

Aberrant cell cycle regulation in cervical carcinoma

Carcinoma of the uterine cervix is one of the most common malignancies among women worldwide. Human papillomaviruses (HPV) have been identified as the major etiological factor in cervical carcinogenesis. However, the time lag between HPV infection and the diagnosis of cancer indicates that multiple steps, as well as multiple factors, may be necessary for the development of cervical cancer. The development and progression of cervical carcinoma have been shown to be dependent on various genetic and epigenetic events, especially alterations in the cell cycle checkpoint machinery. In mammalian cells, control of the cell cycle is regulated by the activity of cyclin-dependent kinases (CDKs) and their essential activating coenzymes, the cyclins. Generally, CDKs, cyclins, and CDK inhibitors function within several pathways, including the p16(INK4A)-cyclin D1-CDK4/6-pRb-E2F, p21(WAF1)- p27(KIP1)-cyclinE-CDK2, and p14(ARF)-MDM2-p53 pathways. The results from several studies showed aberrant regulation of several cell cycle proteins, such as cyclin D, cyclin E, p16(INK4A), p21(WAF1), and p27(KIP1), as characteristic features of HPV- infected and HPV E6/E7 oncogene-expressing cervical carcinomas and their precursors. These data suggested further that interactions of viral proteins with host cellular proteins, particularly cell cycle proteins, are involved in the activation or repression of cell cycle progression in cervical carcinogenesis.

Cyclins D1, D3, E, and A in vulvar carcinoma patients

OBJECTIVE

The treatment of vulvar squamous cell carcinoma patients is often mutilating. Effort is being made to individualize treatment in order to reduce negative side effects for patients with good prognosis. Molecular markers have been able to predict patient outcome in several tumors. The aim of this study was to characterize the expression of cyclins D1, D3, E, and A in a comparatively large series of patients with vulvar squamous cell carcinoma and look for prognostic impact.

METHODS

A total of 224 vulvar squamous cell carcinomas were immunohistochemically investigated for expression of cyclins D1, D3, E, and A using the biotin-streptavidin-peroxidase method and the OptiMax Plus automated cell staining system.

RESULTS

High protein levels of cyclin D1 (any positive nuclei) were found in 58 (26%) cases, cyclin D3 (> or =50% positive nuclei) in 61 (27%) cases, cyclin E (> or =50% positive nuclei) in 41 (18%) cases, and cyclin A (> or =5% positive nuclei) in 156 (70%) cases. No prognostic impact was found for the cyclins D1, D3, E, or A.

CONCLUSIONS

The high number of cases showing increased levels of cyclin A suggests that this protein may be important in the pathogenesis of vulvar squamous cell carcinoma. No prognostic impact was found for the cyclins D1, D3, E, or A.

Expression of estrogen receptor-alpha and Ki67 in relation to pathological and molecular features in early-onset infiltrating ductal carcinoma

Estrogen causes breast cancer by triggering proliferation via an estrogen receptor (ER)-mediated mechanism. However, paradoxically, ER alpha, one of the two known ER subtypes, and the proliferation marker, Ki67, are not usually expressed in the same breast tumor. To explore whether ER alpha-positive tumors and proliferating (Ki67-positive) tumors have different tumorigenic characteristics, we performed an immunohistochemical study on 74 early-onset infiltrating ductal carcinomas of the breast. To test this hypothesis, we examined whether ER alpha-positive and Ki67-positive tumors showed differences in (i) pathological grade, (ii) three indices of tumor grade (tubule formation, nuclear pleomorphism, and mitotic number), and (iii) expression of important proteins implicated in breast tumorigenesis (cyclin D1, ErbB2, ATM, BRCA1, Rb, p53, and p21). The results of the multigenic analysis showed that ER alpha and Ki67 were the only two important markers significantly and independently associated with tumor grade, consistent with the above hypothesis. ER alpha-positive, Ki67-negative tumors frequently displayed a low tumor grade (i.e. being well differentiated), whereas Ki67-positive, ER alpha-negative tumors were more likely to exhibit a high tumor grade. In addition, positive ER alpha expression (46 of 74 cases, 62%) correlated well with positive cyclin D1 expression (p < 0.005), less nuclear pleomorphism (p < 0.001), and a low mitotic count (p < 0.005), whereas positive Ki67 expression (36 of 74 cases, 49%) correlated with reduced BRCA1 expression (p < 0.01) and high mitotic activity (p < 0.01). These findings suggest that the expressions of ER alpha and Ki67 might be involved in distinct pathological and molecular features during breast cancer development.