Activation of protein kinase C promotes human cancer cell growth through downregulation of p18INK4c

Antineoplastic Effects of Ankaferd Hemostat

Objectıve. Ankaferd hemostat (ABS; Ankaferd Blood Stopper®) contains standardized plant extracts comprising Alpinia officinarum, Glycyrrhiza glabra, Thymus vulgaris, Urtica dioica, and Vitis vinifera. ABS especially was recognized for its hemostatic effect; however, antineoplastic role of ABS was identified during the last decade. The aim of this paper is to review the molecular basis and associated clinical implications of the ABS as a topical antineoplastic agent. Materials and Methods. Up to June 2022, literature searches were performed using the internet search engines Medline, Google Scholar, and Embase: Ankaferd. PRISMA flow diagram described the Ankaferd search. Results. ABS have important effects in several cellular processes, like control of the cell cycle, apoptosis, angiogenesis, signal transduction, inflammation, immunologic, and metabolic mechanisms. The molecular basis of antineoplastic roles of ABS depends on its proteomics, metabolomics, and transcriptomics features. ABS has antineoplastic effects on solid tumors like colon, bladder, breast, and osteosarcoma cancer cells. Also, ABS effects renal tubular apoptosis and has antitumoral roles on malign melanoma cells. ABS inhibits hematological tumors like myeloma and lymphoid cells. ABS induces apoptosis in retinal cells and has inhibitory effects on mesenchymal stem cells. It has an antiproliferative role on gastrointestinal tumors like hepatocellular carcinoma cells. Moreover, ABS has a treatment supportive role in cancer since it can prevent oxidative DNA damage and decrease the intestinal damage in necrotizing enterocolitis. Furthermore, it has chemopreventive and hepatoprotective features and can be used for prophylaxis and treatment of oral mucositis. Conclusion. ABS alters cell metabolism and cell cycle. ABS has antineoplastic role on cancer cells. The expanding context of ABS compromises anti-infective, antineoplastic, and wound healing features. ABS may also be used for the palliative, adjuvant, neoadjuvant, or supportive use by interventional radiology procedures for the treatment of solid tumors. Future controlled studies are necessary to clarify the pleiotropic role of ABS like antineoplastic, antithrombotic, anti-inflammatory, anti-infective, antifungal, and antioxidative effects.

A Novel HCC Prognosis Predictor EEF1E1 Is Related to Immune Infiltration and May Be Involved in EEF1E1/ATM/p53 Signaling

BACKGROUND

EEF1E1 has been reported to play a role in ovarian cancer, breast cancer, non-small cell lung cancer and other cancers, but its role and mechanism in hepatocellular carcinoma (HCC) are still unknown.

METHODS

EEF1E1 expression in human HCC was analyzed via the GTEx and TCGA database. Logistic regression analysis was used to analyze the clinicopathological correlation of EEF1E1 expression. The correlation between EEF1E1 expression and patients' prognosis was analyzed in HCC, shown by forest plots, nomogram and Kaplan-Meier curves. Hazard ratio (HR) with 95% confidence intervals and log-rank p-value were calculated via multivariate/univariate survival analyses. Moreover, the correlation between EEF1E1 and tumor immune infiltration was analyzed using the gsva package with the ssgsea algorithm. Pearson correlation was used to investigate the correlation between EEF1E1 expression and p53 pathway genes expression. Two third-party databases were used to validate the content of EEF1E1 protein and mRNA expression patterns and prognosis analysis. The immunohistochemistry and multiplex immunohistochemistry was used to verify the bio-informatics results.

RESULTS

EEF1E1 mRNA and protein expression in tumor was statistically higher than normal (EEF1E1 mRNA: p < 0.001; EEF1E1 protein: p < 0.01). Results from paired t-test (cancer and adjacent tissues) exhibited consistent trend (t = 7.572, p < 0.001). Immunohistochemistry showed that EEF1E1 is highly expressed in cancer. The expression of EEF1E1 was positively correlated with body weight, BMI, tumor status, vascular invasion, AFP, logistic grade, T stage and pathological stage. The univariate Cox model revealed that high EEF1E1 expression was strongly associated with worse OS (HR=2.581; 95% CI: 1.782-3.739; p < 0.001), as was T stage, pathologic stage, Histologic grade. High EEF1E1 expression was the only independent prognostic factor associated with OS (HR=2.57; 95% CI: 1.715-3.851; p < 0.001) in the multivariate analysis. EEF1E1 was significantly correlated with various immune cells, including cytotoxic cells, DC, macrophages, neutrophils, NK cd56bright, TFH, Tgd, Th17, Th2, Treg. Multiplex immunohistochemistry showed that the EEF1E1 protein level is positively correlated to the CD3, CD4, PD1 and is negatively correlated to the CD8. The expression level of EEF1E1 in HCC was significantly correlated with the key genes involved in the p53 pathway. The expression of EEF1E1, ATM, p53 and CASPASE3 in HCC tissues was significantly higher than that in adjacent tissues.

CONCLUSION

EEF1E1 is highly expressed in cancer tissues in HCC. EEF1E1's high expression is significantly correlated with worse prognosis and immune cell infiltration of HCC. EEF1E1 may be participating in EEF1E1/ATM/p53 signaling pathway in HCC.

Peroxiredoxin I deficiency increases keratinocyte apoptosis in a skin tumor model via the ROS-p38 MAPK pathway

Keratinocyte hyperproliferation is an essential link in skin cancer pathogenesis. Peroxiredoxin I (Prx I) is known to regulate cancer cell proliferation, differentiation, and apoptosis, but its role in skin cancer remains unclear. This study aimed to elucidate the role and mechanism of Prx I in skin cancer pathogenesis. Dimethylbenz[a]anthracene (DMBA) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were used to create a skin tumor model of the initiation/promotion stage of cancer. The role of Prx I in H₂O₂-induced keratinocyte apoptosis was also investigated. After DMBA/TPA treatment, Prx I deficiency was significantly associated with less skin tumors, lower Bcl-2 expression, and higher p-p38 and cleaved caspase-3 expressions in Prx I knockout tumors than in wild-type controls. H₂O₂ stimulation caused more cellular apoptosis in Prx I knockdown HaCaT cells than in normal HaCaT cells. The signaling study revealed that Bcl-2, p-p38, and cleaved caspase-3 expressions were consistent with the results in the tumors. In conclusion, the deletion of Prx I triggered the DMBA/TPA-induced skin tumor formation in vivo and in vitro by regulating the reactive oxygen species (ROS)-p38 mitogen-activated protein kinase (MAPK) pathway. These findings provide a theoretical basis for treating skin cancer.

PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression

The proto-oncogene c-Myc regulates multiple biological processes mainly through selectively activating gene expression. However, the mechanisms underlying c-Myc-mediated gene repression in the context of cancer remain less clear. This study aimed to clarify the role of PRMT5 in the transcriptional repression of c-Myc target genes in gastric cancer.

Methods: Immunohistochemistry was used to evaluate the expression of PRMT5, c-Myc and target genes in gastric cancer patients. PRMT5 and c-Myc interaction was assessed by immunofluorescence, co-immunoprecipitation and GST pull-down assays. Bioinformatics analysis, immunoblotting, real-time PCR, chromatin immunoprecipitation, and rescue experiments were used to evaluate the mechanism.

Results: We found that c-Myc directly interacts with protein arginine methyltransferase 5 (PRMT5) to transcriptionally repress the expression of a cohort of genes, including PTEN, CDKN2C (p18^INK4C), CDKN1A (p21^CIP1/WAF1), CDKN1C (p57^KIP2) and p63, to promote gastric cancer cell growth. Specifically, we found that PRMT5 was required to promote gastric cancer cell growth in vitro and in vivo, and for transcriptional repression of this cohort of genes, which was dependent on its methyltransferase activity. Consistently, the promoters of this gene cohort were enriched for both PRMT5-mediated symmetric di-methylation of histone H4 on Arg 3 (H4R3me2s) and c-Myc, and c-Myc depletion also upregulated their expression. H4R3me2s also colocalized with the c-Myc-binding E-box motif (CANNTG) on these genes. We show that PRMT5 directly binds to c-Myc, and this binding is required for transcriptional repression of the target genes. Both c-Myc and PRMT5 expression levels were upregulated in primary human gastric cancer tissues, and their expression levels inversely correlated with clinical outcomes.

Conclusions: Taken together, our study reveals a novel mechanism by which PRMT5-dependent transcriptional repression of c-Myc target genes is required for gastric cancer progression, and provides a potential new strategy for therapeutic targeting of gastric cancer.

Proteomic and transcriptomic analyses to explain the pleiotropic effects of Ankaferd blood stopper

Ankaferd blood stopper is a standardized mixture of the plants Thymus vulgaris, Glycyrrhiza glabra, Vitis vinifera, Alpinia officinarum, and Urtica dioica and has been used as a topical hemostatic agent and with its clinical application established in randomized controlled trials and case reports. Ankaferd has been successfully used in gastrointestinal endobronchial mucosal and cutaneous bleedings and also in abdominal, thoracic, dental and oropharyngeal, and pelvic surgeries. Ankaferd’s hemostatic action is thought to form a protein complex with coagulation factors that facilitate adhesion of blood components. Besides its hemostatic action, Ankaferd has demonstrated pleiotropic effects, including anti-neoplastic and anti-microbial activities and tissue-healing properties; the underlying mechanisms for these have not been well studied. Ankaferd’s individual components were determined by proteomic and chemical analyses. Ankaferd also augments transcription of some transcription factors which is shown with transcriptomic analysis. The independent effects of these ingredients and augmented transcription factors are not known precisely. Here, we review what is known of Ankaferd blood stopper components from chemical, proteomic, and transcriptomic analyses and propose that individual components can explain some pleiotropic effects of Ankaferd. Certainly more research is needed focusing on individual ingredients of Ankaferd to elucidate their precise and effects.

INK4 Family -A promising target for 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer

Inactivation of the p16(INK4a) gene is one of the most frequent defects that contribute to oncogenesis in human cancer, since it is a tumor-suppressor gene. Therefore, functional restoration of p16(INK4a) is one of the most effective methods for cancer prevention. We proposed the concept of 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer, which assumes that transcriptional regulation by drugs on tumor-suppressor genes or functionally similar genes to the tumor-suppressor genes contributes to the prevention of human malignancies. The p16(INK4a) homologs p15(INK4b), p18(INK4c) and p19(INK4d) have been recently identified, and these four members constitute the INK4 family of proteins. All directly bind to cyclin D-cyclin dependent kinase (CDK) 4/6 and are therefore specific inhibitors of these complexes. We recently showed that histone deacetylase (HDAC) inhibitors, promising chemopreventive and chemotherapeutical agents, induce p15(INK4b) and p19(INK4d) gene expression and cause growth arrest, suggesting that both genes are important molecular targets for HDAC inhibitors. Furthermore, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA), which is widely used as a tumor promoter and protein kinase C activator, promotes human cancer cell growth through the down-regulation of p18(INK4c) gene expression. This suggests that a mouse two-stage carcinogenesis model using TPA might partially represent the most common human carcinogenesis pathway related to RB. Our results suggest that the INK4 family consists of attractive and promising molecular targets for the 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer.

Dual suppression of the cyclin-dependent kinase inhibitors CDKN2C and CDKN1A in human melanoma

Resistance to BRAF^V600E inhibitors is associated with reactivation of mitogen-activated protein kinase (MAPK) signaling at different levels in melanoma. To identify downstream effectors of MAPK signaling that could be used as potential additional therapeutic targets for BRAF^V600E inhibitors, we used hTERT/CDK4R24C/p53DD-immortalized primary human melanocytes genetically modified to ectopically express BRAF^V600E or NRAS^G12D and observed induction of the AP-1 transcription factor family member c-Jun. Using a dominant negative approach, in vitro cell proliferation assays, western blots, and flow cytometry showed that MAPK signaling via BRAF^V600E promotes melanoma cell proliferation at G1 through AP-1-mediated negative regulation of the INK4 family member, cyclin-dependent kinase inhibitor 2C (CDKN2C), and the CIP/KIP family member, cyclin-dependent kinase inhibitor 1A (CDKN1A). These effects were antagonized by pharmacological inhibition of CDKN2C and CDKN1A targets CDK2 and CDK4 in vitro. In contrast to BRAF^V600E or NRAS^G12D-expressing melanocytes, melanoma cells have an inherent resistance to suppression of AP-1 activity by BRAF^V600E- or MEK-inhibitors. Here, CDK2/4 inhibition statistically significantly augmented the effects of BRAF^V600E- or MEK-inhibitors on melanoma cell viability in vitro and growth in athymic nude Foxn1^nu mice (P = .03 when mean tumor volume at day 13 was compared for BRAF^V600E inhibitor vs BRAF^V600E inhibitor plus CDK2/4 inhibition; P = .02 when mean tumor volume was compared for MEK inhibitor vs MEK inhibitor plus CDK2/4 inhibition; P values were calculated by a two-sided Welch t test; n = 4–8 mice per group).

MicroRNA-212 displays tumor-promoting properties in non-small cell lung cancer cells and targets the hedgehog pathway receptor PTCH1

Overexpression of microRNA-212 promoted cell cycle progression and cell proliferation, migration, and invasion in non–small cell lung cancer cells. PTCH1, a receptor of hedgehog pathway, is a functional target of miR-212. The role of miR-212 in cell proliferation may be mediated by PTCH1.

Dysexpression of microRNAs has been found in many tumors, including lung cancer. The hedgehog (Hh) signaling pathway plays an important role during normal development, and the abnormal regulation of its members has also been related to many tumors. However, little is known about the relationship between microRNA and the Hh pathway. In this paper, we report microRNA-212 (miR-212) playing a role in non-small cell lung cancer (NSCLC) and targeting PTCH1, a receptor of the Hh pathway. We found that miR-212 was up-regulated when cells were treated with 4ß-12-O-tetradecanoylphorbol-13-acetate (TPA). We ectopically expressed miR-212 in NSCLC cell lines to examine the influence of miR-212 overexpression. The results showed that overexpression of miR-212 in NSCLC cells promoted cell cycle progression and cell proliferation, migration, and invasion. The promoting effects of miR-212 on cell proliferation, migration, and invasion were partially reversed by the miR-212 inhibitor anti-miR-212. These results suggested that miR-212 might have tumor-promoting properties. Potential targets of miR-212 were predicted, and we showed tumor suppressor PTCH1 was a functional target of miR-212. PTCH1 may be responsible for the effect of miR-212 on cell proliferation. Altogether, our results indicated that miR-212 was involved in tumorigenesis, and the oncogenic activity of miR-212 in NSCLC cells was due, in part, to suppression of PTCH1.

Evaluation of the novel protein kinase C inhibitor sotrastaurin as immunosuppressive therapy after renal transplantation

IMPORTANCE OF THE FIELD

The prevalence of acute renal allograft rejection has decreased substantially in past decades due to new and more specific immunosuppressive compounds but improvements in long-term graft function have not been achieved. There is a large need for new immunosuppressive agents that lack toxicity of current agents such as calcineurin inhibitors but show high synergistic efficiency in preventing rejection processes.

AREAS COVERED IN THIS REVIEW

This review summarizes data concerning the pharmacokinetics, pharmacodynamics and clinical efficacy of the new PKC inhibitor sotrastaurin with a focus on renal transplantation. The article contains information that has been presented at international transplant meetings and congresses and that has been published between 2006 and 2010. Additionally, current ongoing trials are described in detail.

WHAT THE READER WILL GAIN

Immunosuppressive regimens after kidney transplantation consist of a combination of several agents in order to minimize drug toxicity. Therefore, the reader is presented with the most up-to-date/current developments in sotrastaurin applications in Phase I and II trials with emphasis on data maintained from studies that combined sotrastaurin with established agents such as mycophenolic acid and tacrolimus.

TAKE HOME MESSAGE

Several trials are ongoing and planned to determine the optimal immunosuppressive regimen to benefit from sotrastaurin's distinct mechanism of action.

Effects of the new immunosuppressive agent AEB071 on human immune cells

BACKGROUND. The novel immunosuppressive agent AEB071 is currently being evaluated for its capability to prevent rejection after kidney transplantation as a potential adjunct to calcineurin inhibitor-based regimen. AEB071 is a selective protein kinase C inhibitor and has been shown to be well tolerated in humans. We here present extensive in vitro studies that contribute to the understanding of AEB071 effects on human lymphocyte, natural killer (NK) cell and dendritic cell (DC) action.

METHODS

The impact of AEB071 on several T-cell activation and costimulatory markers was assessed. Furthermore, assays were performed to study the effect on T-cell proliferation and intracellular cytokine production. Additionally, the effect of AEB071 on DC maturation and their capacity to stimulate allogeneic T-cells was examined. Also, an evaluation of AEB071 effects on the lytic activity of human NK cells was performed.

RESULTS

We were able to show that T-cell proliferation and cytokine production rates are significantly reduced after AEB071 administration. Also, mitogen-induced T-cell activation characterized by expression levels of surface markers could be significantly inhibited. In contrast, the T-cell stimulatory capacity of AEB071-treated mature monocyte-derived DC (Mo-DC) is not reduced, and AEB071 administration does not prevent lipopolysaccharide (LPS)-induced Mo-DC maturation. It could be demonstrated that AEB071 significantly inhibited the cytotoxic activity of NK cells.

CONCLUSIONS

The promising immunosuppressive agent AEB071 has a strong impact on T-cell activation, proliferation and cytokine production as well as NK cell activity, but not DC maturation in vitro, and therefore, seems to function T-cell and NK cell specific via protein kinase C (PKC) inhibition.

Amplicons on chromosome 3 contain oncogenes induced by recurrent exposure to 12-O-tetradecanoylphorbol-13-acetate and sodium n-butyrate and Epstein-Barr virus reactivation in a nasopharyngeal carcinoma cell line

Nasopharyngeal carcinoma (NPC) is closely associated with Epstein-Barr virus (EBV) infection and exposure to environmental carcinogens. In this study, an inducible Epstein-Barr virus (EBV) reactivation NPC cell line, NA, was used to investigate the impact of recurrent 12-O-tetradecanoylphorbol-13-acetate-sodium n-butyrate (TPA/SB) treatment and EBV reactivation on chromosomal abnormalities utilizing array-based comparative genomic hybridization (CGH). It was observed that most copy-number aberrations (CNA) were progressively nonrandomly clustered on chromosomes 3, 8, and 9, as the frequency of TPA/SB treatment and EBV reactivation increased. All of the prominent amplicons detected (including 3p14.1, 3p13, 3p12.3, 3p12.2, 3q26.2, 3q26.31, and 3q26.32) were located on chromosome 3, with multiple oncogenes assigned to these sites. The amplification patterns of 3p12.3 and 3q26.2 were validated using fluorescence in situ hybridization (FISH) analysis. Subsequent quantitative real-time polymerase chain reaction detected increasing expression of ROBO1 and SKIL oncogenes in NA cells harboring higher frequency of TPA/SB treatment and EBV reactivation, consistent with copy-number amplification of these loci. These findings demonstrate that a high incidence of TPA/SB induced-EBV reactivation has a profound influence on the carcinogenesis of NPC through altered DNA copy number.

Structure-related clustering of gene expression fingerprints of thp-1 cells exposed to smaller polycyclic aromatic hydrocarbons

This study was undertaken to test the hypothesis that structurally similar PAHs induce similar gene expression profiles. THP-1 cells were exposed to a series of 12 selected PAHs at 50 microM for 24 hours and gene expressions profiles were analyzed using both unsupervised and supervised methods. Clustering analysis of gene expression profiles revealed that the 12 tested chemicals were grouped into five clusters. Within each cluster, the gene expression profiles are more similar to each other than to the ones outside the cluster. One-methylanthracene and 1-methylfluorene were found to have the most similar profiles; dibenzothiophene and dibenzofuran were found to share common profiles with fluorine. As expression pattern comparisons were expanded, similarity in genomic fingerprint dropped off dramatically. Prediction analysis of microarrays (PAM) based on the clustering pattern generated 49 predictor genes that can be used for sample discrimination. Moreover, a significant analysis of Microarrays (SAM) identified 598 genes being modulated by tested chemicals with a variety of biological processes, such as cell cycle, metabolism, and protein binding and KEGG pathways being significantly (p < 0.05) affected. It is feasible to distinguish structurally different PAHs based on their genomic fingerprints, which are mechanism based.

Proteomic analysis of protein expression changes in a model of gliomagenesis

Loss of p53 function is a common event in a variety of human cancers including tumors of glial origin. Using an in vitro mouse model of malignant astrocyte transformation, three cleavable isotope coded affinity tag (cICAT) experiments were performed comparing cultured wild-type astrocytes and two p53(-/-) astrocyte cultures before and after malignant transformation. We identified and quantitated an average of 1366 proteins per experiment and demonstrated that the protein quantitation ratios in each individual cICAT experiment correlated well to ratios determined in the other two studies. These data were further supported by microarray analysis which also correlated to changes in protein expression. The results showed significant changes in protein expression in association with malignant transformation. Proteins overexpressed in malignant astrocytes were typically involved in ribosome biogenesis/protein synthesis and DNA replication, while underexpressed proteins were generally associated with the regulation of cell cycle checkpoint control, tumor suppression, and apoptosis. Among the significantly up-regulated proteins and transcripts in malignant mouse astrocytes were members of the minichromosome maintenance (MCM) family. Western blot analysis verified increased expression of MCM proteins in malignant human astrocytoma cell lines, which had not previously been described. These results demonstrate the usefulness of the cICAT approach for comparing differences in protein expression profiles between normal and malignant cells.

12-o-Tetradecanoylphorbol 13-acetate prevents baicalein-induced apoptosis via activation of protein kinase C and JNKs in human leukemia cells

In the present study, we found that baicalein (BE), but not its glycoside baicalin (BI), induced apoptosis in human leukemia HL-60 and Jurkat cells, but not in primary murine peritoneal macrophages (PMs) or human polymorphonuclear (PMN) cells, by the MTT assay, LDH release assay, and flow cytometric analysis. Activation of the caspase 3, but not caspase 1, enzyme via inducing protein processing was detected in BE-induced apoptosis. The ROS-scavenging activity of BE was identified by the anti-DPPH radical, DCHF-DA, and in vitro plasmid digestion assay, and none of chemical antioxidants including allpurinol (ALL), N-acetyl-cystein (NAC), and diphenylene iodonium (DPI) affected BE-induced apoptosis in HL-60 cells. This suggests that apoptosis induced by BE is independent of the production of ROS in HL-60 cells. Interestingly, the apoptotic events such as DNA ladders formation and activation of the caspase 3 cascade were significantly blocked by TPA addition in the presence of membrane translocation of PKCalpha, and TPA-induced protection was reduced by adding the PKC inhibitors, GF-109203X and staurosporin. TPA addition induces the phosphorylation of JNKs and ERKs, but not p38, protein in HL-60 cells, and incubation of HL-60 cells with JNKs inhibitor SP600125, but not ERKs inhibitor, PD98059 or the p38 inhibitor SB203580, suppressed the protective effect of TPA against BE-induced apoptotic events including DNA ladders, apoptotic bodies, caspase 3 and D4-GDI protein cleavage in according with blocking JNKs protein phosphorylation. In addition, PKC inhibitor GF-109203X treatment blocks TPA-induced ERKs and JNKs protein phosphorylation, which indicates that activation of PKC locates at upstream of MAPKs activation in TPA-treated HL-60 cells. Additionally, a loss in mitochondrial membrane potential with a reduction in Bcl-2 protein expression, the induction of Bad protein phosphorylation, and translocation of cytochrome c from mitochondria to the cytosol were observed in BE-treated HL-60 cells, and these events were prevented by the addition of TPA. GF-109203X and SP600125 suppression of TPA against cytochrome c release induced by BE was identified. This suggests that activation of PKC and JNKs participate in TPA's prevention of BE-induced apoptosis via suppressing mitochondrial dysfunction in HL-60 cells.

Oct-1 is involved in the transcriptional repression of the p15(INK4b) gene

p15(INK4b) functions as a tumor suppressor and implicated in cellular senescence. Here, we show that the Oct-1 binding site in the human p15(INK4b) gene promoter functions as a silencer. Oct-1 specifically interacts with this binding site in vitro and in vivo and SMRT and HDAC1 are present in the p15(INK4b) proximal promoter region. Moreover, mouse embryo fibroblasts (MEFs) lacking Oct-1 have shown significantly increased levels of p15(INK4b) protein compared to their normal counterparts. Treatment with a histone deacetylase (HDAC) inhibitor has activated the expression of p15(INK4b) in wild-type MEFs but has no effect in MEFs lacking Oct-1, suggesting that Oct-1 represses p15(INK4b) gene expression in an HDAC-dependent manner. Finally, we show that the expression of Oct-1 protein significantly decreases, whereas p15(INK4b) protein significantly increases with the cellular aging process. Taken together, these results suggest that Oct-1 is an important transcriptional repressor for p15(INK4b) gene and the transcriptional repression of the p15(INK4b) gene by Oct-1 may be one of the regulatory mechanisms of cellular senescence.

C3-induced 3LL cell proliferation is mediated by C kinase

It has been demonstrated that the third component of complement (C3)(1) and its peptides increase normal and tumour cell proliferation. However, the signal cascade responsible for this phenomenon is still unknown. In this study, we elucidate some of the mechanisms involved in the signalling of C3 stimulation of cell proliferation. We have first investigated the in and out traffic of C3 peptides, then we have identified the subcellular localisation of internalised C3 and, finally, we have explored the role of protein phosphorylation in C3 traffic and in the proliferation of the Lewis lung carcinoma (3LL) cells. Our results indicate that traffic of C3 is not dependent on cytoskeletal integrity and requires protein kinase C-dependent phosphorylation. In addition, proliferation of 3LL cells stimulated by C3 depends on both C3 internalisation and protein-kinase C phosphorylation.

Trichostatin A activates p18INK4c gene: differential activation and cooperation with p19INK4d gene

We have reported that histone deacetylase (HDAC) inhibitors activate a member of the INK4 family, the p19INK4d gene, causing G1 phase arrest. We report here that HDAC inhibitor, Trichostatin A, activates another member of the INK4 family, the p18INK4c gene, through its promoter in Jurkat cells. Interestingly, the activation patterns of the p18INK4c gene were different from those of p19INK4d. Furthermore, mouse embryo fibroblasts lacking p18Ink4c or p18Ink4c/p19Ink4d were resistant to the growth inhibitory effects of TSA as compared to their wild-type counterpart. Our findings suggest that p18INK4c is involved in TSA-mediated cell growth inhibition and cooperates with p19INK4d.