Lipomas of the Oral Cavity: Utility of MDM2 and CDK4 in Avoiding Overdiagnosis as Atypical Lipomatous Tumor

Traumatized lipomas with degenerative change may demonstrate histopathologic features that mimic atypical lipomatous tumor (ALT). Previously reported series of ALT involving the oral cavity preceded routine use of MDM2 and CDK4 immunohistochemistry. Our aim is to evaluate MDM2 and CDK4 immunohistochemical expression in adipocytic tumors arising in this site, in conjunction with the histiocytic marker PU.1, to determine whether MDM2 and CDK4 impacts classification. 17 cases originally diagnosed as ALT were retrieved and immunohistochemical studies for MDM2, CDK4 and PU.1 were performed. FISH analysis for MDM2 amplification was performed in select cases. For this study group, the male:female ratio was 9:8 and the median age was 62 (range 41-88). All 17 cases presented as well- or predominantly well-circumscribed proliferations of variably sized, mature adipocytes exhibiting uni- or multi-vacuolation with occasional scalloped nuclei and mild nuclear atypia. Variable amounts of fibrous stroma with focal myxoid change and bland spindle cells were identified in 14/17 cases. Lipoblasts or atypical hyperchromatic stromal cells were not identified in any cases. 14 of 17 cases were negative for MDM2 and CDK4 in tumor cells and 11 of these 14 showed weak nuclear positivity for MDM2 in histiocytes. 3 of 17 cases showed weak, multifocal immunohistochemical expression of MDM2 and CDK4. PU.1 highlighted histiocytes in all 17 cases. FISH analysis for MDM2 amplification was negative in all 3 cases with weak MDM2/CDK4 expression. All cases were reclassified as lipoma with degenerative changes. ALT, in all likelihood, is less common than previously thought in this anatomic location and best diagnosed with ancillary studies. MDM2 expression in histiocytes is best interpreted in conjunction with CDK4 immunohistochemistry and confirmatory FISH for MDM2 amplification.

Inhibition of cyclin-dependent kinase 4 as a potential therapeutic strategy for treatment of synovial sarcoma

Synovial sarcoma is a highly aggressive but rare form of soft tissue malignancy that primarily affects the extremities of the arms or legs, for which current chemotherapeutic agents have not been proven to be very effective. The cyclin-dependent kinase 4/6-retinoblastoma protein (CDK4/6-Rb) pathway of cell cycle control is known to be aberrant in a large proportion of cancers. Recently, CDK4 inhibitors have successfully been used pre-clinically for the treatment of many human cancers, and in 2015, following the success of clinical trials, the FDA approved the first selective CDK4/6 inhibitor, palbociclib, for the treatment of endocrine therapy resistant breast cancers. However, the expression and therapeutic potential of targeting CDK4 in synovial sarcoma remains unclear. In the present study, we report that CDK4 is highly expressed in human synovial sarcoma, and high CDK4 expressions are associated with poor prognosis in sarcomas patients and the clinical stage and the TNM grade in synovial sarcoma patients. Knockdown of CDK4 with specific small interference RNAs inhibits cell proliferation and enhances apoptotic effects in synovial sarcoma cells. CDK4 inhibitor palbociclib suppresses synovial sarcoma cell proliferation and growth in a dose and time-dependent manner. Palbociclib also inhibits the CDK4/6-Rb signaling pathway and promotes cell apoptosis without changing CDK4/6 protein levels, suggesting that palbociclib only represses the hyper-activation, not the expression of CDK4/6. Flow cytometry analysis reveals that palbociclib induces G1 cell-cycle arrest and apoptotic effects by targeting the CDK4/6-Rb pathway in synovial sarcoma cells. Furthermore, wound healing assays demonstrate that inhibition of the CDK4/6-Rb pathway by palbociclib significantly decreases synovial sarcoma cell migration in vitro. Our study highlights the importance of the CDK4/6-Rb pathway in human synovial sarcoma pathogenesis, and the role of the current selective CDK4/6 inhibitor, palbociclib, as a potential promising targeted therapeutic agent in the treatment of human synovial sarcoma.

SOX12 upregulation is associated with metastasis of hepatocellular carcinoma and increases CDK4 and IGF2BP1 expression

OBJECTIVE

In this study, we studied the expression profile of SOX12 gene in different pathological stages of hepatocellular carcinoma (HCC) and explored the possible downstream genes related to its regulation of HCC invasion and migration.

MATERIALS AND METHODS

Bioinformatic data mining was performed in liver cancer cohort in TCGA. HepG2 cells were used as in vitro cell model to assess the effect of SOX12 on CDK4 and IGF2BP1 expression. The association between the expression of SOX12, CDK4 or IGF2BP1 and survival time in HCC patients was also assessed based on the data in TCGA.

RESULTS

The regional lymph node metastasis (N1) and distant metastasis (M1) cases had significantly increased SOX12 expression than the lymph node negative (N0) and distant metastasis negative (M0) cases respectively. CDK4 and IGF2BP1 were among the top 20 SOX12 co-upregulated genes in HCC, which have well characterized enhancing the effect on HCC cell growth, invasion, and metastasis. In HepG2 cells, knockdown of SOX12 reduced IGF2BP1 and CDK4 expression, while enforced SOX12 expression significantly enhanced their expression. Low SOX12 or CDK4 expression was associated with significantly better 3-year survival and better 5-year survival. Low IGF2BP1 expression was associated with significantly better 3-year survival in HCC patients.

CONCLUSIONS

SOX12 upregulation is associated with regional and distant metastasis of HCC. SOX12 can increase the expression of CDK4 and IGF2BP1, which confer malignant phenotypes to HCC. The expression of SOX12, IGF2BP1 or CDK4 might be potential clinical prognostic markers for HCC.

[Expression of CDK4 and p16 in laryngeal squamous cell carcinoma]

OBJECTIVE

To investigate the expression of CDK4 and p16 in laryngeal squamous cell carcinoma (LSCC) tissues.

METHOD

The expressions of CDK4 and p16 in 30 cases of LSCC tissues and 20 cases of edge tissues were detected by immunohistochemical technology SP method, and discuss their correlation with clincial pathology and clinical stage of LSCC.

RESULT

The positive rates of CDK4 and p16 were 63. 3 %,46. 7% in LSCC tissues, and the positive rates were 25%, 90% in edge tissues. The expression of CDK4 in LSCC tissues was significantly higher than that in edge tissues(P<0. 05), which was not associated with the clincial pathology and clinical stage(P> 0. 05); The expression of p16 in LSCC tissues was significantly lower than that in edge tissues(P<0. 05), it was associated with the clincial pathology (P<0. 05), but not associated with clinical stage(P>0. 05) ;there is a negative correlation between CDK4 and p16 (r= -0. 786, P<0. 05).

CONCLUSION

Low expression of p16 and high expression of CDK4 may play an important role in the development of LSCC and the low expression of p16 in LSCC tissue could be used as important reference markers of malignant degree of tumour.

Novel inhibitors of nuclear transport cause cell cycle arrest and decrease cyst growth in ADPKD associated with decreased CDK4 levels

Autosomal-dominant polycystic kidney disease (ADPKD) is a progressive, proliferative renal disease. Kidneys from ADPKD patients are characterized by the presence of cysts that are marked by enhanced proliferation and apoptosis of renal tubular epithelial cells. Current treatment of this disease is supportive, as there are few if any clinically validated targeted therapeutics. Given the parallels between cystic disease and cancer, and in light of our findings of the efficacy of the nuclear transport inhibitors in kidney cancer, which has similarities to ADPKD, we asked whether such inhibitors show utility in ADPKD. In this study, we tested selective inhibitors of nuclear export (SINE) in two human ADPKD cell lines and in an in vivo mouse model of ADPKD. After effective downregulation of a nuclear exporter, exportin 1 (XPO1), with KPT-330, both cell lines showed dose-dependent inhibition of cell proliferation through G₀/G₁ arrest associated with downregulation of CDK4, with minimal apoptosis. To analyze mechanisms of CDK4 decrease by XPO1 inhibition, localization of various XPO1 target proteins was examined, and C/EBPβ was found to be localized in the nucleus by XPO1 inhibition, resulting in an increase of C/EBPα, which activates degradation of CDK4. Furthermore, inhibition of XPO1 with the parallel inhibitor KPT-335 attenuated cyst growth in vivo in the PKD1 mutant mouse model Pkd1(v/v). Thus, inhibition of nuclear export by KPT-330, which has shown no adverse effects in renal serum chemistries and urinalyses in animal models, and which is already in phase 1 trials for cancers, will be rapidly translatable to human ADPKD.

Coordinated expression of cyclin-dependent kinase-4 and its regulators in human oral tumors

BACKGROUND/AIM

While aberrant expression of cyclin-dependent kinase-4 (CDK4) has been found in squamous cell carcinoma of the head and neck (SCCHN), the associations between CDK4 and its regulators, namely, cyclin D1, cyclin E, gankyrin, SEI1, and BMI1 in gene expression remain to be explored. Herein we investigated the mRNA profiles of these oncogenes and their interrelations in different oral lesion tissues.

MATERIALS AND METHODS

Thirty SCCHN specimens and patient-matched high at-risk mucosa (HARM) and 16 healthy control specimens were subjected to quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses.

RESULTS

The mRNA levels of CDK4, cyclin D1, gankyrin, SEI1, BMI1 were significantly elevated in both HARM and SCCHN (in comparison with control specimens), and statistically significant correlations were found among these markers in gene expression.

CONCLUSION

Up-regulation of CDK4 and its regulators takes place in oral cancer progression in a coordinate manner, and HARM and SCCHN share a similar molecular signature within the CDK4-pRB pathway.

MicroRNA-545 suppresses cell proliferation by targeting cyclin D1 and CDK4 in lung cancer cells

An increasing number of reports have shown that diverse microRNAs are involved in tumorigenesis and tumor progression. We performed this study to identify novel miRNAs that may be involved in lung cancer and study on their functions. We tested the expression of 450 miRNAs in lung tumor tissues and adjacent non-cancerous tissues. We found that miRNA-545 was less abundant in cancerous lung tissues than in adjacent non-cancerous tissues. Our further studies showed that miR-545 suppressed cell proliferation in vitro and in vivo. We also found that miR-545 caused cell cycle arrest at the G0/G1 phase and induced cell apoptosis in lung cancer cells by targeting cyclin D1 and CDK4 genes. The effects of cyclin D1 and CDK4 down-regulated by miR-545 were similar to those caused by siRNAs of cyclin D1 and CDK4, and overexpression of cyclin D1 and CDK4 could abolish the miR-545-induced inhibition of cell proliferation. In conclusion, miR-545 suppressed cell proliferation by inhibiting the expression of cyclin D1 and CDK4. Our findings provide new knowledge regarding the role of miR-545 in the development of lung cancer and indicate the potential application of miR-545 in cancer therapy.

Thioridazine induces apoptosis by targeting the PI3K/Akt/mTOR pathway in cervical and endometrial cancer cells

Recently, thioridazine (10-[2-(1-methyl-2-piperidyl) ethyl]-2-methylthiophenothiazine), a well-known anti-psychotic agent was found to have anti-cancer activity in cancer cells. However, the molecular mechanism of the agent in cellular signal pathways has not been well defined. Thioridazine significantly increased early- and late-stage apoptotic fraction in cervical and endometrial cancer cells, suggesting that suppression of cell growth by thioridazine was due to the induction of apoptosis. Cell cycle analysis indicated thioridazine induced the down-regulation of cyclin D1, cyclin A and CDK4, and the induction of p21 and p27, a cyclin-dependent kinase inhibitor. Additionally, we compared the influence of thioridazine with cisplatin used as a control, and similar patterns between the two drugs were observed in cervical and endometrial cancer cell lines. Furthermore, as expected, thioridazine successfully inhibited phosphorylation of Akt, phosphorylation of 4E-BP1 and phosphorylation of p70S6K, which is one of the best characterized targets of the mTOR complex cascade. These results suggest that thioridazine effectively suppresses tumor growth activity by targeting the PI3K/Akt/mTOR/p70S6K signaling pathway.

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.

Human ovarian tumor cells escape γδ T cell recognition partly by down regulating surface expression of MICA and limiting cell cycle related molecules

Background

Mechanisms of human Vγ2Vδ2 T cell-mediated tumor immunity have yet to be fully elucidated.

Methods and Findings

At least some tumor cell recognition is mediated by NKG2D-MICA interactions. Herein, by using MTT assay and PI-BrdU co-staining and Western-blot, we show that these Vγ2Vδ2 T cells can limit the proliferation of ovarian tumor cells by down regulation of apoptosis and cell cycle related molecules in tumor cells. Cell-to-cell contact is critical. γδ T cell-resistant, but not susceptible ovarian tumor cells escape γδ T cell-mediated immune recognition by up-regulating pErk1/2, thereby decreasing surface MICA levels. Erk1/2 inhibitor pretreatment or incubation prevents this MICA decrease, while up-regulating key cell cycle related molecules such as CDK2, CDK4 and Cyclin D1, as well as apoptosis related molecules making resistant tumor cells now vulnerable to γδ T cell-mediated lysis.

Conclusion

These findings demonstrate novel effects of γδT cells on ovarian tumor cells.

Selective inhibition of HTLV-1-infected cell proliferation by a novel tetramethylnaphthalene derivative

Adult T-cell leukemia (ATL) is caused by infection with human T-lymphotropic virus type 1 (HTLV-1). A novel tetramethylnaphthalene derivative, TMNAA, selectively inhibited the proliferation of various HTLV-1-infected cells, including ATL cell lines and peripheral blood mononuclear cells (PBMCs) from ATL patients. In contrast, the proliferation of uninfected cell lines and PBMCs from healthy donors was hardly affected by the compound. Cell-cycle analysis revealed that TMNAA increased the population of the G0/G1 phase and reduced that of the S phase in HTLV-1-infected cells. TMNAA was found to suppress the phosphorylation of retinoblastoma protein and the expression of cyclin-dependent kinase 4 in HTLV-1-infected cells. Furthermore, the inhibition of cell proliferation was partially annihilated by removing the compound. These results indicate that TMNAA exerts selective inhibition of HTLV-1-infected cells through a novel mechanism, presumably modulating cell cycle regulatory proteins associated with the G0/G1 phase.

Anti-proliferative effect and action mechanism of dexamethasone in human medullary thyroid cancer cell line

INTRODUCTION

Dexamethasone is known to inhibit the cell proliferation of certain transformed cell lines. In this study, the effect and action mechanism of dexamethasone were examined in the human medullary thyroid cancer cell line, TT cells.

METHODS

TT cells were treated with or without dexamethasone. 5-Bromo-2'-deoxyuridine uptake assay was used to evaluate cell proliferation. Cell cycle and its regulatory proteins were assessed by flow cytometry and western blot analysis, respectively. Apoptosis was analyzed by Hoechst staining and Annexin V assay.

RESULTS

Dexamethasone significantly reduced TT cell proliferation by 60% (p < 0.01). A substantial portion of cells was arrested at the G1 phase. The expression levels of cyclin D1, cyclin-dependent kinase (CDK)4, and CDK2 were decreased. In addition, the phosphorylation of retinoblastoma protein, which is a critical checkpoint protein in the transition of G1 to S phase, was decreased. On the other hand, the expression level of p27(Kip1), which is a cyclin/CDK inhibitor, was enhanced. Hoechst staining showed many fragmented nuclei in the dexamethasone-treated cells. The proportion of early apoptotic cells was also increased in the Annexin V assay.

CONCLUSION

Dexamethasone inhibited the proliferation of TT cells through cell cycle arrest at the G1 phase and increased apoptosis.

Sansalvamide induces pancreatic cancer growth arrest through changes in the cell cycle

Survival of patients with pancreatic cancer remains poor due to inadequate chemotherapeutic options. Sansalvamide A, a cyclic depsipeptide produced by a marine fungus, has demonstrated significant anticancer activity. We previously observed antiproliferative effects in a series of sansalvamide A analogs in pancreatic cancer cells, one of which was further evaluated in this study. Two human pancreatic cancer cell lines (AsPC-1 and CD18) were incubated with increasing concentrations (10-50 muM) of the sansalvamide analog. Cell proliferation was then measured by thymidine incorporation and cell counting, and cell cycle analysis was determined by flow cytometry. Western blot analysis was used to evaluate expression of cyclin D1, cdk4, cdk6, cyclin E, cyclin A, cdk2, and p21. Sansalvamide caused G(1) phase cell cycle arrest in both cell lines, and Western blot analyses demonstrated up-regulation of p21, down-regulation of cyclins D1, E, and A, and cdk4, consistent with G(0)/G(1) cell cycle arrest. Cumulatively the results show that Sansalvamide A attenuates pancreatic cancer cell growth and represents a potential anticancer therapy.

Porphyromonas gingivalis invades human trophoblasts and inhibits proliferation by inducing G1 arrest and apoptosis

Porphyromonas gingivalis is an oral pathogen that is also associated with serious systemic conditions such as preterm delivery. Here we investigated the interaction between P. gingivalis and a cell line of extravillous trophoblasts (HTR-8) derived from the human placenta. P. gingivalis internalized within HTR-8 cells and inhibited proliferation through induction of arrest in the G1 phase of the cell cycle. G1 arrest was associated with decreased expression of cyclin D and of CDKs 2, 4 and 6. In addition, levels of CDK inhibitors p15, p16, p18 and p21 were increased following P. gingivalis infection. The amount of Rb was diminished by P. gingivalis, and transient overexpression of Rb, with concomitant upregulation of phospho-Rb, relieved P. gingivalis-induced G1 arrest. HTR-8 cells halted in the G1 phase became apoptotic, and apoptosis was accompanied by an increase in the ratio of Bax/Bcl-2 and increased activity of caspases 3, 7 and 9. HTR-8 cells infected with P. gingivalis also exhibited a sustained activation of ERK1/2, and knock-down of ERK1/2 activity with siRNA abrogated both G1 arrest and apoptosis. Thus, P. gingivalis can invade placental trophoblasts and induce G1 arrest and apoptosis through pathways involving ERK1/2 and its downstream effectors, properties that provide a mechanistic basis for pathogenicity in complications of pregnancy.

Growth inhibition of human MDA-mB-231 breast cancer cells by delta-tocotrienol is associated with loss of cyclin D1/CDK4 expression and accompanying changes in the state of phosphorylation of the retinoblastoma tumor suppressor gene product

Tocotrienols, a subgroup within the vitamin E family of compounds, have shown antiproliferative and anticancer properties, however, the molecular basis of these effects remains to be elucidated. In this study, the effect of 3-tocotrienol on cell cycle arrest was assessed by studying the retinoblastoma protein (Rb) levels and phosphorylation status, levels of E2F (a transcription factor critically involved in the G1/S-phase transition of the mammalian cell cycle; originally identified as a DNA-binding protein essential for early region 1A-dependent activation of the adenovirus promoter designated E2), and other cell cycle controlling proteins in estrogen receptor-negative MDA-MB-231 breast cancer cells. The cell growth assay demonstrated that exposure of the MDA-MB-231 cells to 6-tocotrienol (1-20 microM) resulted in a dose- and time-dependent inhibition of cell growth as compared with vehicle treated cells and the magnitude of growth inhibition was higher at 10 and 20 microM treatment for 48 and 72 h. The phosphorylation status of Rb plays a central role in the control of the cell cycle at the G0/G1-phase. delta-Tocotrienol treatment reduced the total Rb and its phosphorylation at the Ser780, Ser795, Ser 807/811 and Thr826 positions in a dose- and time-dependent fashion. The site-specific inhibition of the phosphorylation of Rb by delta-tocotrienol was tightly associated with a marked reduction in the expression of cyclin D1 and its regulatory partner cyclin-dependant kinase 4 (CDK4), which is responsible for the phosphorylation of Rb at Ser780, Ser795, Ser 807/811 and Thr826. In addition, delta-tocotrienol also reduced the expression of E2F that occurred simultaneously with the loss of Rb phosphorylation and inhibition of cell cycle progression. Interestingly, delta-tocotrienol also caused a marked reduction in the expression of G2/M regulatory proteins including cyclin B1 and CDK1. To the best of our knowledge, this study was the first to reveal that the target of cell proliferative inhibitory action of delta-tocotrienol in a model estrogen receptor-negative human breast cancer cell line MDA-MB-231 is mediated by the loss of cyclin D1 and associated suppression of site-specific Rb phosphorylation, suggesting its future development and use as an anticancer agent.

Sulindac suppresses beta-catenin expression in human cancer cells

Sulindac has been reported to be effective in suppressing tumor growth through the induction of p21WAF1/cip1 in human, animal models of colon cancer and colon cancer cells. In this study, we treated human breast cancer cell line MCF-7 and lung cancer cell line A549 as well as colon cancer cell line SW620 with sulindac to observe the effects of sulindac in other tissue sites. In all cell lines, proliferation was significantly inhibited by sulindac after 24 and 72 h of treatment. Apoptosis was induced by sulindac in both lung cancer cells and colon cancer cells but was not induced in breast cancer cells. Western blots showed that p21 protein level were induced by sulindac in lung cancer cells and colon cancer cells, but not in breast cancer cells. However, the suppression of beta-catenin, a key mediator of Wnt signaling pathway, was seen in all three cell lines with sulindac administration. Further studies revealed that transcriptional activities of beta-catenin were significantly inhibited by sulindac and that the inhibition was sulindac dosage-dependent. The transcriptional targets of beta-catenin, c-myc, cyclin D1 and cdk 4 were also dramatically downregulated. In conclusion, our data demonstrated that the efficacy of sulindac in the inhibition of cell proliferation (rather than the induction of apoptosis) might be through the suppression of beta-catenin pathway in human cancer cells.

Serum starvation induces G1 arrest through suppression of Skp2-CDK2 and CDK4 in SK-OV-3 cells

Recent studies have suggested that Skp2, an SCF-type ubiquitin ligase, positively regulates cell cycle through degradation of p27, which is an inhibitor of cyclin-dependent kinase 2 (CDK2), which drives cells from the G1 to S phase of cell cycles. In the present study, we examined key regulatory proteins involved in serum starvation-induced cell cycle arrest in human ovarian cancer cells, SK-OV-3. Cell cycle analysis showed that cells were arrested at the G1 phase after serum starvation. Western blot analysis showed that the protein levels of CDK4 and CDK2 were significantly decreased in SK-OV-3 cells. Consistently, Roscovitine, an inhibitor of CDK2, induced cell cycle arrest in normally proliferating cells and a chemical inhibitor of CDK4, 3-ATA [3-Amino-9-thio(10H)-acridone], was found to induce growth arrest. We also found that the protein level of Skp2 was dramatically decreased in response to serum starvation. Moreover, CDK2 protein, which allows cell cycle transit from the G1 to the S phase, was decreased when the Skp2 expression was inhibited by specific siRNA of Skp2, but CDK4 was not decreased. Therefore, these results suggest that serum starvation induces G1 arrest through suppression of Skp2-dependent CDK2 activity and Skp2-independent CDK4 activity in human SK-OV-3 ovarian cancer cells.

Vaccinia virus-mediated cell cycle alteration involves inactivation of tumour suppressors associated with Brf1 and TBP

The vaccinia virus (VV) replicates robustly and alters the progression of the cell cycle via an unknown mechanism. Herein, we provide evidence for the existence of a unique VV infection-induced cell cycle control mechanism. The regulation is correlated with the inactivation of p53 and Rb, which are associated with the RNA polymerase III transcription factor B (TFIIIB) subunits, TBP and Brf1 respectively. VV infection induced the expression of Mdm2 and its translocation into the nucleus, thereby resulting in a disruption of p53. VV also stimulated the expression of TFIIIB and TFIIIC, and consequently induced tRNA synthesis. On the other hand, the total level of Rb was not significantly influenced, but the level of hypo-phosphorylated Rb was enhanced, partially due to the VV-induced downregulation of cyclin-dependent kinases 4 and 6. However, the hypo-phosphorylated Rb appeared to be largely sequestered into a complex with Brf1, which resulted in the blockage of Rb function to repress E2F1 transactivation, thereby leading to a moderately higher proportion of cells in the S and G(2) phases. Conversely, the enforced expression of exogenous Rb restored the normally observed cell cycle patterns. Overall, these controls may contribute to the efficient replication of the virus in rapidly growing cells.

Antiproliferation of human prostate cancer cells by ethanolic extracts of Brazilian propolis and its botanical origin

Propolis is a resinous substance collected by bees (Apis mellifera) from various tree buds which they then use to coat hive parts and to seal cracks and crevices in the hive. Propolis, a known ancient folk medicine, has been extensively used in diet to improve health and to prevent disease. In the present study, we have evaluated the effects of ethanolic extracts of Brazilian propolis group l2 and bud resins of botanical origin (B. dracunculifolia), and propolis group 3 on proliferation of metastasis (DU145 and PC-3) and primary malignant tumor (RC58T/h/SA#4)-derived human prostate cancer cells. The strongest inhibition was observed in propolis group 3 (sample #3) extracts whereas moderate growth inhibition was observed in human prostate epithelial cells. In the RC58T/h/SA#4 cells, resins of botanical origin of propolis group 12 (sample #1) and propolis group 12 (sample #2) induced growth inhibition that was associated with S phase arrest whereas propolis group 3 (sample #3) induced growth inhibition that was associated with G2 arrest. The mechanisms of cell cycle effects of propolis were investigated. The resins of botanical origin of propolis group 12 and propolis group 12 showed similar inhibition of cyclin D1, CDK4 and cyclin B1 expression. Propolis group 3 showed higher induction of p21 expression but no inhibition of cyclin D1, CDK4 and cyclin B1 expression. The results obtained here demonstrate that the Brazilian propolis extracts have significant inhibitory effect on proliferation of human prostate cancer cells. Inhibition was achieved through regulation of protein expression of cyclin D1, B1 and cyclin dependent kinase (CDK) as well as p21. Our results indicate that the Brazilian propolis extracts show promise as chemotherapeutic agents as well as preventive agents against prostate cancer.

Mechanism of saikosaponin-d in the regulation of rat mesangial cell proliferation and synthesis of extracellular matrix proteins

Glomerulosclerosis is a common disorder in many types of chronic kidney diseases. Previous studies have shown that glomerular mesangial cells (MCs) play an important role in the pathogenesis of glomerulosclerosis. The ability of saikosaponin-d (SSd) to reduce the damage of kidney in progressive glomerulosclerosis has been demonstrated. In this study, the effects of saikosaponin-d on MC proliferation and synthesis of extracellular matrix proteins were investigated. Rat MCs were isolated from Wistar rats and cultured in Dulbecco's modified Eagle's medium. MCs were challenged with lipopolysacchorides and incubated with different concentrations of SSd. Cell proliferation and cytotoxicity were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), flow cytometry, and lactate dehydrogenase assays. Type IV collagen, fibronectin, and TGF-beta1 in the conditioned medium were measured. The expression of cyclin-dependent kinase 4, c-Jun, and c-Fos was determined by immunohistochemistry. At a concentration of 4 microg/mL or lower, SSd inhibited MC proliferation but did not cause cell death. SSd also inhibited lipopolysaccharide-induced secretion of type IV collagen, fibronectin, and TGF-beta1 in MCs. Additionally, SSd reduced the expression of CDK4, c-Jun, and c-Fos in MCs. We conclude that SSd inhibited MC proliferation and synthesis of extracullular matrix proteins through the downregulation of the CDK4, c-Jun, and c-Fos genes.

Induced JunD in intestinal epithelial cells represses CDK4 transcription through its proximal promoter region following polyamine depletion

Maintenance of intestinal epithelial integrity requires cellular polyamines that regulate expression of various genes involved in cell proliferation, growth arrest and apoptosis. In prior studies, depletion of cellular polyamines has been shown to stabilize JunD, a member of the AP-1 (activator protein-1) family of transcription factors, leading to inhibition of intestinal epithelial cell proliferation, but the exact downstream targets of induced JunD remain elusive. CDK4 (cyclin-dependent kinase 4) is essential for the G1- to S-phase transition during the cell cycle and its expression is primarily controlled at the transcriptional level. In the present study, we show that induced JunD in IECs (intestinal epithelial cells) is a transcriptional repressor of the CDK4 gene following polyamine depletion. Increased JunD in polyamine-deficient cells was associated with a significant inhibition of CDK4 transcription, as indicated by repression of CDK4-promoter activity and decreased levels of CDK4 mRNA and protein, all of which were prevented by using specific antisense JunD oligomers. Ectopic expression of the wild-type junD also repressed CDK4-promoter activity and decreased levels of CDK4 mRNA and protein without any effect on CDK2 expression. Gel shift and chromatin immunoprecipitation assays revealed that JunD bound to the proximal region of the CDK4-promoter in vitro as well as in vivo, while experiments using different CDK4-promoter mutants showed that transcriptional repression of CDK4 by JunD was mediated through an AP-1 binding site within this proximal sequence of the CDK4-promoter. These results indicate that induced JunD in IECs represses CDK4 transcription through its proximal promoter region following polyamine depletion.

Apoptosis induced by lycorine in KM3 cells is associated with the G0/G1 cell cycle arrest

Lycorine is a natural anti-tumor alkaloid extracted from Amaryllidaceae and has various biological effects on malignant cells. The present study explores the effects of lycorine on the human multiple meyloma cell line, KM3, and the possible mechanisms of these effects. An MTT assay showed that lycorine had significant inhibitory activity on KM3 cells. The growth rates of the KM3 cells exposed to lycorine evidently slowed down. Cell fluorescent apoptotic morphological changes, DNA degradation fragments, and a sub-G1 peak were detected, indicating the occurrence of cell apoptosis after lycorine treatment. Furthermore, the release of mitochondrial cytochrome c, the augmentation of Bax with the attenuation of Bcl-2, and the activation of caspase-9, -8, and -3 were also detected, suggesting that the mitochondrial pathway and the death acceptor pathway were also involved. The results also showed that lycorine was able to block the cell cycle at the G0/G1 phase through the downregulation of both cyclin D1 and CDK4. In summary, lycorine can suppress the proliferation of KM3 cells and reduce cell survival by arresting cell cycle progression as well as inducing cell apoptosis.

Chromosome-12 copy number alterations and MDM2, CDK4 and TP53 expression in soft tissue liposarcoma

BACKGROUND

Liposarcoma is a heterogeneous group of soft tissue sarcomas in which definitive prognostic parameters need to be identified.

MATERIALS AND METHODS

The series included 33 consecutive soft tissue (well-differentiated, WDLPS, n=19; and dedifferentiated, DDLPS, n=14) liposarcoma. Clinicopathological variables included age, gender, body location, degree of dedifferentiation and mitotic count. The rrolecular analysis included MDM2, CDK4 and TP53 expressions and chromosome-12 copy number alterations.

RESULTS

Centrally located (retroperitoneal, abdominal cavity or groin region) WDLPS had more dedifferentiation (p=0.001). Patients with DDLPS and a high mitotic rate died (p=0.070) or experienced recurrencies (p=0.029) more frequently. Co-expression of MDM2/CDK4 (p=0.001) and TP53 accumulation (p=0.017) related to dedifferentiation but not to recurrence or death, both in WDLPS and DDLPS. DDLPS had higher centromeric chromosome-12 copy number than WDLPS (p=0.013), but this was unrelated to recurrence or death.

CONCLUSION

Central location is a risk factor in WDLP. Co-expression of MDM2/CDK4/TP53 and chromosome-12 alterations characterize DDLPS suggesting a link with dedifferentiation.

Mechanisms involved in resveratrol-induced apoptosis and cell cycle arrest in prostate cancer-derived cell lines

Resveratrol is a polyphenol found at high concentrations in grapes and red wine with reported anticarcinogenic effects. We studied the molecular mechanism of resveratrol-induced apoptosis and proliferation arrest in prostate derived cells PZ-HPV-7 (nontumorigenic line), LNCaP (androgen-sensitive cancer line), and PC-3 (androgen-insensitive cancer line). Apoptosis and cell cycle distribution were evaluated by flow cytometry and proliferation by MTT assay and direct cell counting. Caspases, bax, bcl-2, cyclins, Cdks, p53, p21, and p27 were measured by Western blot and kinase activities of cyclin/Cdk complexes by immunoprecipitation followed by kinase assays with appropriate substrates. Resveratrol induced a decrease in proliferation rates and an increase in apoptosis in cancer cell lines in a dose- and time-dependent manner. These effects were coincident with cell accumulation at the G0/G1 phase. In LNCaP and PC-3, the apoptosis induced by resveratrol was mediated by activation of caspases 9 and 3 and a change in the ratio of bax/bcl-2. Expressions of cyclin D1, E, and Cdk4 as well as cyclin D1/Cdk4 kinase activity were reduced by resveratrol only in LNCaP cells. In contrast, cyclin B and Cdk1 expression and cyclin B/Cdk1 kinase activity were decreased in both cell lines in the presence of resveratrol. However, modulator proteins p53, p21, and p27 were increased by resveratrol only in LNCaP cells. These effects probably result in the observed proliferation arrest and disruption of cell cycle control. In addition, the specific differences found between LNCaP and PC-3 suggest that resveratrol acts through different mechanisms upon the androgen or estrogen receptor cell status.

The expressions of the Rb pathway in cervical intraepithelial neoplasia; predictive and prognostic significance

OBJECTIVES

The aim of the study was to assess the expression of the Rb pathway (p16(INK4a)-cdk4-pRb) in cervical intraepithelial neoplasia as a prognostic marker by investigating the association between expression of Rb pathway and the recurrence.

METHODS

The study group comprised of 265 paraffin-embedded tissues of the uterine cervix collected from patients between 2001 and 2003. Patients underwent ablative or excisional treatment and were followed for 2 years. RB pathway expression was examined using immunohistochemistry applied to a tissue microarray. HPV detection and genotyping were performed with HPV DNA Chip. Statistical analysis was done by ANOVA test, Student's t test, and Pearson's correlation test.

RESULTS

With increasing CIN grade, p16(INK4a) and cdk4 expression rates increased, while the pRb expression rate decreased. The expression rate of p16(INK4a) was higher (33%) in CIN I with high-risk HPV infection than in CIN I without high-risk HPV infection (19%). The mean expression rates of p16(INK4a) were 29%, 39%, and 64%, respectively, in CIN I, II, and III without recurrence, but 25%, 28%, and 44% in those with recurrence. The mean expression rates of pRb were 47%, 40%, and 18% in CIN I, II, and III without recurrence, respectively, but 48%, 45%, and 34% in those with recurrence.

CONCLUSION

A relatively low expression rate of p16(INK4a) has prognostic significance for predicting recurrence. The clinical utility of p16(INK4a) status for stratifying patients according to their need for aggressive treatment requires further investigation.

IGFII and MIB1 immunohistochemistry is helpful for the differentiation of benign from malignant adrenocortical tumours

AIMS

The differentiation of adrenocortical carcinomas from adenomas may be difficult based on morphology alone. Differential expression of insulin-like growth factor (IGF) II and cyclin-dependent kinase (CDK) 4 has recently been described in these tumours. The aim of this study was to investigate the diagnostic usefulness of these markers immunohistochemically.

METHODS AND RESULTS

We examined 22 benign and 17 malignant adrenocortical tumours and compared IGFII and CDK4 expression with known immunohistochemical as well as morphological criteria of malignancy. Thirteen of 17 carcinomas showed immunohistochemical reactivity for IGFII, whereas all adenomas but one were negative. Intense CDK4 expression was detected in 11 of 17 carcinomas but was present in only three of 22 adenomas. The MIB1 index was >5% in 14 of 16 carcinomas and was <5% in all adenomas but one. The combination of IGFII immunohistochemistry with MIB1 index led to high sensitivity and specificity in detecting adrenocortical carcinomas.

CONCLUSIONS

IGFII and MIB1 are helpful immunohistochemical markers to predict malignancy in adrenocortical neoplasms. These markers can be used in addition to clinical, gross and morphological features to establish a diagnosis in difficult cases.

[Transfection of pemt-2-cDNA inhibits the expression of cell cycle related proteins in rat CBRH-7919 hepatoma cells]

OBJECTIVES

To unravel the molecular mechanism of proliferation inhibition induced by transfection of pemt2-cDNA into rat CBRH-7919 hepatoma cells.

METHODS

We started with the highly expressed PEMT2 clone. Cell culture and Western blotting techniques were used to examine the expression of cyclinD1/CDK4, cyclinE/CDK2, phospho-Rb, caspase-3, c-jun and caveolins.

RESULTS

Our results showed that CDK4, CDK2, phospho-Rb and c-jun were down regulated in the pemt2 highly expressed cell clone. The high expression clone of pemt2-transfected cells also showed over expression of caspase-3.

CONCLUSION

The reductions of proliferation and apoptosis of pemt2 transfected cells could be related to the G1 phase arrest induced by down-regulation of the cell cycle-associated proteins.

[cyclin D1/E2F pathways involved in cell cycle changes of human embryo lung fibroblasts induced by benzo(a)pyrene]

OBJECTIVE

To investigate the roles of cyclin D1/CDK4-E2F-1/4 pathway in cell cycle changes of human embryo lung fibroblasts (HELF) induced by two different benzo(a)pyrene [B(a)P] treatment models.

METHODS

Two B(a)P treatment models: HELF were treated by 2 micromol/L B(a)P for 24 hours; HELF were treated by 100 micromol/L B(a)P three times 24 hours each and provide with some characteristics of transformed cells (T-HELF). Changes of cell cycle and the expression of cyclin D1, CDK4 and E2F-1/4 were checked using the flow cytometry and Western bolt analysis.

RESULTS

After 24 hours 2 microml/L B(a)P treatment, the HELFs in the G(1) phase was decreased. In HELF transfected with antisense cyclin Dl (A-Dl) and antisense CDK4 (A-K4), the expression of cyclin Dl and CDK4 blocked the cell cycle changes from the G(1) phase to the S phase induced by B(a)P. The overexpression of cyclin Dl and E2F-1 in HELF was induced by B(a)P. The E2F-1 overexpression in A-D1 induced B(a)P was inhibited. The E2F-4 expression was decreased and the CDK4 expression was increased significantly in A-K4 after B(a)P treatment. Most of T-HELF transfected with antisense cyclin Dl (T-A-Dl) and antisense CDK4 (T-A-K4) were retained in G(1) phase. The cyclin Dl expression in T-HELF was increased significantly compared with that in HELF. The E2F-4 expression in T-A-Dl and T-A-K4 was increased significantly compared with that in T-HELF.

CONCLUSION

B(a)P induces the cell cycle changes through cyclin D1/CDK4-E2F-1/4 pathway in HELF treated by 2 micromol/L B(a)P while it induces cell cycle changes through cyclin D1/CDK4-E2F-4 pathway in T-HELF.

Overexpression of cyclin D1-CDK4 in silica-induced transformed cells is due to activation of ERKs, JNKs/AP-1 pathway

Silica has been known to be a factor inducing acute injury and chronic pulmonary fibrosis. Silica has also been listed as a human carcinogen in 1996 by International Agency for Research on Cancer (IARC). However, the molecular mechanisms involved its pathologic effects are not well understood. In these studies, we found that exposure of human embryonic lung fibroblasts (HELF) to crystalline silica could cause increases in activation of extracellular signal-regulated kinases (ERKs), p38K, and c-Jun NH2-terminal amino kinases (JNKs), and HELF transformation. Interestingly, silica-induced transformation of HELF (S-HELF) led to increases in activated levels of ERKs and p46 of JNKs, and decrease in p38K activation, and no effect on activation of p54 of JNKs, as compared with those in parental HELF. Further studies showed that there are differential effects of ERKs, JNKs and p38K, as well as their downstream transcription factor AP-1, in regulation of expression of cyclin D1 and CDK4 and cell cycle alternations induced by silica. Cyclin D1 and CDK4 were increased in S-HELF as compared with those in HELF. Inhibition of ERKs activation by AG126, JNK by SP600125, and AP-1 by curcumin could reduced the induction of cyclin D1 and CDK4. There is no significant difference for cell cycle distribution between groups. These results demonstrate that ERKs and JNKs, but not p38K is responsible for induction of cyclin D1 and CDK4 in S-HELF, suggesting that overexpression of cyclin D1 and CDK4 caused by silica is mediated by ERK, JNK/AP-1signaling pathway.

Cyclin-dependent kinase 4 expression is essential for neu-induced breast tumorigenesis

Previous work has shown that cyclin D1 expression is required for neu- and ras-induced, but not wnt- or c-myc-induced, breast tumorigenesis in mice. Although cyclin D1 binds and activates cyclin-dependent kinase 4 (Cdk4), thereby mediating activation of a program of E2F-dependent gene expression, it has been suggested that the oncogenic activities of cyclin D1 are independent of Cdk4. To determine whether Cdk4 expression is required for breast tumorigenesis in mice, we have generated compound mice ectopically expressing the neu or wnt oncogenes in the mammary glands of wild-type and Cdk4-/- mice. Our results show that Cdk4 expression is required for efficient neu-induced tumorigenesis but is dispensable for wnt-induced breast tumorigenesis. In contrast to results previously observed in the mammary glands of cyclin D1-/- virgin females, our results show defects in mammary gland development in Cdk4-/- virgin females, suggesting differences in compensatory mechanisms in the absence of either subunit of the cyclin D1/Cdk4 complex. These results suggest that drugs targeted to inhibit Cdk4 activities could be developed to specifically treat certain breast tumors as Cdk4 is not essential for viability.

[Study on mechanism of the anti-tumor activity of Acanthopanax gracilistylus]

OBJECTIVE

To study the mechanism of anti-tumor activity of Acanthopanax gracilistylus extract (Age).

METHODS

The tumor cells proliferation was detected by using (3H)-TdR incorporation method, and the effects of Age on cell cycle of tumor cells, retinoblastoma (Rb) protein and cyclin-dependent kinases (Cdk) were analyzed by flow cytometry and Western blotting assay, respectively.

RESULTS

It was indicated by cytoactivity test in vitro that Age only had effect in inhibiting the proliferation of tumor cells, it couldn't lead to death of cells. Under action of Age, the proliferation of tumor cells was halted at G0/G1 stage of cell cycle, and showed no direct cytotoxic effect by Age. Age could induce lowering of the expression of Rb, Cdk2 and Cdk4, cause halt of tumor cell proliferation.

CONCLUSION

The tumor inhibitory effect of Age is realized by way of regulating the activity of cell cycle controlling enzymes to suspend the proliferation of tumor cells.

[Expressions of FHIT and cyclin D1/CDK4 in oral cancer and oral precancerous lesions]

OBJECTIVE

To detect the expressions of fragile histidine triad (FHIT) and cyclin D1/CDK4 in oral squamous cell carcinoma (OSCC) and oral precancerous lesions and investigate the relationship between the expressions and the histopathological changes.

METHODS

Immunohistochemical staining by SP methods was utilized to detect the expression of FHIT and cyclin D1/CDK4 in 64 cases of OSCC, 39 oral precancerous lesions and 12 normal oral mucosa specimens.

RESULTS

The rate of the negative or low FHIT expression in OSCC was 17% (11/64), which was remarkably lower than that in normal oral membrane and oral precancerous lesions (P<0.01). Significantly higher levels of cyclin D1/CDK4 expressed in OSCC than in normal oral membrane and precancerous lesions (P<0.01). There was no significant correlation between FHIT and cyclin D1/CDK4, and positive correlation between cyclin D1 and CDK4 was observed.

CONCLUSION

FHIT, cyclin D1 and CDK4 may play a role in the pathogenesis of OSCC, and FHIT can down-regulate the expression of cyclin D1.

[Expression of PTKs CDK4 and p15 in the middle ear cholesteatomatous epithelium]

OBJECTIVE

To explore the cells proliferation and its molecular regulating mechanisms of cholesteatomatous epithelium from the aspect of protein tyrosine kinases (PTKs) signal transduction and cell cycle control.

METHOD

The expressions of phosphated PTKs, CDK4 and p15 were investigated by immunohistochemical S-P method and computer image analysis in 30 specimens of the middle ear cholesteatomatous epithelium and 19 specimens of external auditory canal epithelium from patients with chronic otitis media with cholesteatoma. The expressive results of phosphated PTKs, CDK4 and p15 were determined in same epithelium of different slices of same specimen. Statistical analysis was performed by the connection with degree of subepidermal inflammatory cell infiltration and degree of bone destruction.

RESULT

The expression of phosphated PTKs was primarily staining in cell membrane, and the staining of CDK4 were located in the nuclei as well as the cytoplasm of cells, and the staining of nuclei was primary, but the staining of p15 was expressed only in the nuclei of cell. The expressions of phosphated PTKs, CDK4 and p15 in epithelium were clearly increased compared with that of external auditory canal epithelium (P < 0.01). The expression of phosphated PTKs and CDK4 tended to be strong in the epithelium with subepidermal inflammatory, and the expression of CDK4 tended to be strong in the epithelium with high level expression of phosphated PTKs (P < 0.01). The expressions of above investigated indexes were not significantly different under the different degree of bone destruction (P > 0.05).

CONCLUSION

The cholesteatomatous epithelium have a hyperproliferation ability, and also show a mechanism of inhibiting proliferation ability. The microenvironment with inflammatory cell infiltration has a tendency to greatly affect proliferation ability of cholesteatomatous epithelium.

[Effects of celecoxib on the proliferation and apoptosis of human colorectal cancer cell line HT-29]

OBJECTIVE

To determine the effect of Celecoxib on the proliferation and apoptosis of human colorectal cancer cell line HT-29 and the probable mechanism involved.

METHODS

Using MTT assay, flow cytometry, Acridine orange and Ethidium bromide staining, and Western blotting analysis, the effects of celecoxib on the proliferation and apoptosis of HT-29 cells as well as its related mechanism were studied.

RESULTS

The growth of HT-29 cell was inhibited by celecoxib in a dose- and time-dependent manner. Sub-G1 peak was detected by FCM, and apoptotic rate was between (7.31 +/- 2.37) % and (48.30 +/- 2.86) %. The cell ratio of G0/G1 phase increased,whereas the cell ratio of S and G2/M phases decreased in a dose-dependent manner after the treatment. The HT-29 cell line exhibited some morphologic features of apoptosis, including cell shrinkage, nuclear condensation, DNA fragmentation, and formation of apoptosis bodies, and the apoptotic rate was in a dose- and time-dependent manner. Celecoxib down-regulated the expression of CDK2, CDK4 and up-regulated the expression of P2 WAF1/CIP1

CONCLUSION

The effect of celecoxib inhibiting cell HT-29 proliferation and inducing cell apoptosis may relate to its blocking cell cycle progress.