Comparative effects of overexpression of p27Kip1 and p21Cip1/Waf1 on growth and differentiation in human colon carcinoma cells

The Multifaceted p21 (Cip1/Waf1/CDKN1A) in Cell Differentiation, Migration and Cancer Therapy

Loss of cell cycle control is characteristic of tumorigenesis. The protein p21 is the founding member of cyclin-dependent kinase inhibitors and an important versatile cell cycle protein. p21 is transcriptionally controlled by p53 and p53-independent pathways. Its expression is increased in response to various intra- and extracellular stimuli to arrest the cell cycle ensuring genomic stability. Apart from its roles in cell cycle regulation including mitosis, p21 is involved in differentiation, cell migration, cytoskeletal dynamics, apoptosis, transcription, DNA repair, reprogramming of induced pluripotent stem cells, autophagy and the onset of senescence. p21 acts either as a tumor suppressor or as an oncogene depending largely on the cellular context, its subcellular localization and posttranslational modifications. In the present review, we briefly mention the general functions of p21 and summarize its roles in differentiation, migration and invasion in detail. Finally, regarding its dual role as tumor suppressor and oncogene, we highlight the potential, difficulties and risks of using p21 as a biomarker as well as a therapeutic target.

Selenoprotein H controls cell cycle progression and proliferation of human colorectal cancer cells

Selenoprotein H (SELENOH) is supposed to be involved in redox regulation as well as in tumorigenesis. However, its role in healthy and transformed cells of the gastrointestinal tract remains elusive. We analyzed SELENOH expression in cells depending on their selenium supply and differentiation status and found that SELENOH expression was increased in tumor tissue, in undifferentiated epithelial cells from mice and in colorectal cancer lines as compared to more differentiated ones. Knockdown studies in human colorectal cancer cells revealed that repression of SELENOH decreased cellular differentiation and increased proliferation and migration. In addition, SELENOH knockdown cells have a higher competence to form colonies or tumor xenografts. In parallel, they show a faster cell cycle transition. The high levels of SELENOH in tumors as well as in undifferentiated, proliferative cells together with its inhibitory effects on proliferation and G1/S phase transition suggest SELENOH as a key regulator for cell cycle progression and for prevention of uncontrolled proliferation. As SELENOH expression is highly dependent on the selenium status, effects of selenium supplementation on cancer initiation and progression appear to involve SELENOH.

Lysine-specific demethylase 2A expression is associated with cell growth and cyclin D1 expression in colorectal adenocarcinoma

OBJECTIVE

Lysine-specific demethylase 2A (KDM2A), a specific H3K36me1/2 demethylase, has been reported to be closely associated with several types of cancer. In this study, we aimed to investigate the expression and function of KDM2A in colorectal adenocarcinoma.

METHODS

A total of 215 colorectal adenocarcinoma specimens were collected, and then subjected to immunohistochemistry assay to evaluate the expression levels of KDM2A, cyclin D1 and other proteins in colorectal adenocarcinoma tissues. Real-time polymerase chain reaction, Western blot, and other molecular biology methods were used to explore the role of KDM2A in colorectal adenocarcinoma cells.

RESULTS

In this study, we report that the expression level of KDM2A is high in colorectal adenocarcinoma tissues, and this high expression promotes the proliferation and colony formation of colorectal adenocarcinoma cells, as demonstrated by KDM2A knockdown experiments. In addition, the expression of KDM2A is closely associated with cyclin D1 expression in colorectal adenocarcinoma tissues and cell lines.

CONCLUSIONS

Our study reveals a novel role for high-expressed KDM2A in colorectal adenocarcinoma cell growth, and that the expression of KDM2A is associated with that of cyclin D1 in colorectal adenocarcinoma.

In vitro antitumor effects of two novel oligostilbenes, cis- and trans-suffruticosol D, isolated from Paeonia suffruticosa seeds

Naturally derived stilbenes have been shown to elicit cytotoxic, anti-steroidal, anti-mutagenic, anti-oxidative, anti-inflammatory, and antitumor bioactivities. Previous phytochemical studies revealed that the seeds of Paeonia suffruticosa are rich in natural stilbenes. In this study the antitumor effects and mechanism of action of the oligostilbene isomers, cis- and trans-suffruticosol D, isolated from the seeds of P. suffruticosa were examined. cis- and trans-suffruticosol D exhibited remarkable cytotoxicity against the human cancer cell lines A549 (lung), BT20 (breast), MCF-7 (breast), and U2OS (osteosarcoma), but showed significantly less toxicity to the normal human cell lines HMEC (breast) and HPL1A (lung). We also demonstrated that cis- and trans-suffruticosol D exerted their antitumor effects by provoking oxidative stress, stimulating apoptosis, decreasing the mitochondrial membrane potential, inhibiting cell motility, and blocking the NF-κB pathway in human lung cancer cells. In addition, we evaluated their respective bioefficacy and found that trans-suffruticosol D is more potent than cis-suffruticosol D. Collectively, our results suggest that cis- and trans-suffruticosol D could be promising chemotherapeutic agents against cancer.

Basal p21 controls population heterogeneity in cycling and quiescent cell cycle states

Phenotypic heterogeneity within a population of genetically identical cells is emerging as a common theme in multiple biological systems, including human cell biology and cancer. Using live-cell imaging, flow cytometry, and kinetic modeling, we showed that two states--quiescence and cell cycling--can coexist within an isogenic population of human cells and resulted from low basal expression levels of p21, a Cyclin-dependent kinase (CDK) inhibitor (CKI). We attribute the p21-dependent heterogeneity in cell cycle activity to double-negative feedback regulation involving CDK2, p21, and E3 ubiquitin ligases. In support of this mechanism, analysis of cells at a point before cell cycle entry (i.e., before the G1/S transition) revealed a p21-CDK2 axis that determines quiescent and cycling cell states. Our findings suggest a mechanistic role for p21 in generating heterogeneity in both normal tissues and tumors.

The tumor suppressing effects of QKI-5 in prostate cancer: a novel diagnostic and prognostic protein

In recent years, the RNA-binding protein quaking 5 (QKI-5) has been recognized as a novel tumor suppressor in many cancers. To date, no studies have examined the role of QKI-5 in prostate cancer. The present study was designed to elucidate the correlation of QKI-5 expression with the clinical pathological features and prognosis of prostate cancer. In an overwhelming majority of the 184 cases of prostate cancer samples analyzed, the QKI-5 expression was significantly decreased, which was largely due to the high promoter methylation levels. Using lentiviral vectors, we established two stable prostate cancer cell lines with altered QKI-5 expression, including a QKI-5 overexpressing PC3 cell line and a DU145 cell line with knocked-down QKI-5 expression. The effects of the lentiviral-mediated QKI-5 knockdown on the PC3 cells and DU145 cells were assessed by cell growth curves, flow cytometry (FCM), and an invasion assay. The PC3 cells were transplanted into nude mice, and then, the tumor growth curves and TUNEL staining were determined. These results demonstrated that QKI-5 was highly expressed in benign prostatic hyperplasia (BPH) tissues but not in carcinomatous tissues and that QKI-5 effectively inhibited prostate cancer cell proliferation in vitro and in vivo. In addition, the decrease in QKI-5 expression was closely correlated with the prostate cancer Gleason score, poor differentiation, degree of invasion, lymph node metastasis, distant metastasis, TNM grading, and poor survival. These results indicate that the QKI-5 expression may be a novel, independent factor in the prognosis of prostate cancer patients.

C4.4A expression is associated with a poor prognosis of esophageal squamous cell carcinoma

BACKGROUND

C4.4A is a glycolipid-anchored membrane protein expressed in several human malignancies. We examined clinical relevance of C4.4A expression in 111 esophageal squamous cell carcinoma (ESCC) tissue samples.

METHODS

Anti-human C4.4A antibody that recognizes the glycosylphosphatidyl inositol (GPI) anchor signaling sequence (C4.4A-GPI Ab) and anti-human C4.4A-119 polyclonal antibody (C4.4A-119 Ab) were used for immunohistochemistry and Western blot testing.

RESULTS

Both antibodies detected the C4.4A protein expression at the parabasal layer of normal epithelium of the esophagus. In tumor tissues, the C4.4A protein was detected in 66 (59.5 %) and 95 (85.6 %) of 111 ESCCs by the C4.4A-GPI Ab and the C4.4A-119 Ab, respectively. The C4.4A-GPI Ab mainly detected membranous C4.4A expression (83.3 %, 55 of 66 positive cases), while the C4.4A-119 Ab exclusively detected cytoplasmic C4.4A expression (100 %, 73 cytoplasm alone and 22 cytoplasm plus membrane in 95 positive cases). Western blot analysis indicated that normal epithelium expressed the band of C4.4A at 70 kDa, whereas the tumor tissues displayed the band at the lower molecular weight. Survival analysis indicated that the C4.4A-positive ESCCs had significantly worse 5-year overall survival than the C4.4A-negative ESCC samples (P = 0.021) when using the C4.4A-GPI Ab, but not when using the C4.4A-119 Ab. This difference was most evident with membranous expression of C4.4A (P = 0.005).

CONCLUSIONS

C4.4A expression was associated with a poor prognosis of ESCC when the GPI-related antibody was used. On the other hand, the C4.4A-119 Ab may be a useful diagnostic tool for ESCC because of its high detection rate.

Kynurenic acid enhances expression of p21 Waf1/Cip1 in colon cancer HT-29 cells

BACKGROUND

Kynurenic acid (KYNA), a tryptophan metabolite, was found in the mucus of rat small intestine. However, its role in the gastrointestinal tract is still not fully elucidated.

METHODS

To verify whether KYNA affects cell cycle regulators, the protein expression of cyclin-dependent kinase inhibitor p21 Waf1/Cip1 was investigated in colon adenocarcinoma HT-29 cells exposed to KYNA. MTT, BrdU assay and siRNA technology were used to evaluate the effect of KYNA on cancer cell proliferation.

RESULTS

KYNA significantly enhanced the expression of p21 Waf1/Cip1. Importantly, the overexpression of this protein was involved in inhibition of proliferation and DNA synthesis in HT-29 cells.

CONCLUSIONS

KYNA may be considered as a potential chemoprevention agent against colon cancer.

Downregulation of tumor suppressor QKI in gastric cancer and its implication in cancer prognosis

Gastric cancer (GC) is the fourth most common cancer and second leading cause of cancer-related death worldwide. RNA-binding protein Quaking (QKI) is a newly identified tumor suppressor in multiple cancers, while its role in GC is largely unknown. Our study here aimed to clarify the relationship between QKI expression with the clinicopathologic characteristics and the prognosis of GC. In the 222 GC patients' specimens, QKI expression was found to be significantly decreased in most of the GC tissues, which was largely due to promoter hypermethylation. QKI overexpression reduced the proliferation ability of GC cell line in vitro study. In addition, the reduced QKI expression correlated well with poor differentiation status, depth of invasion, gastric lymph node metastasis, distant metastasis, advanced TNM stage, and poor survival. Multivariate analysis showed QKI expression was an independent prognostic factor for patient survival.

Expression of C4.4A at the invasive front is a novel prognostic marker for disease recurrence of colorectal cancer

Metastasis-associated gene C4.4A is a glycolipid-anchored membrane protein expressed in several human malignancies. The aim of this study was to explore the expression and clinical relevance of C4.4A in colorectal cancer. By quantitative RT-PCR, 154 colorectal cancer tissues were examined for C4.4A mRNA. We examined 132 colorectal cancer tissues by immunohistochemistry using a new polyclonal antibody that recognizes the C4.4A protein C-terminus containing the glycosylphosphatidyl-inositol anchor signaling sequence. A significant difference in 5-year overall survival was found between samples with high and low expression of C4.4A mRNA (P = 0.0005). Immunohistochemistry showed strong membranous staining of C4.4A at the invasive front of colorectal cancer tumors and at the frontier of metastatic lesions to lymph node and lung. The membranous staining with enhanced intensity at the invasive front of the primary colorectal cancer (Type A: 34/132, 25.6%) was associated with depth of invasion (P = 0.033) and venous invasion (P = 0.003), and was a significant independent prognostic factor (5-year overall survival in the entire series [n = 132; P = 0.004] and disease-free survival in stage II and III colorectal cancers [n = 82; P = 0.003]). Moreover, Type A C4.4A expression was linked to shorter liver metastasis-free survival rate, lung metastasis-free survival rate, or hematogenous metastasis-free survival (P = 0.0279, P = 0.0061, and P = 0.0006, respectively). Our data indicate that expression of the C4.4A protein at the invasive front acts as a novel prognostic marker in colorectal cancer, possibly through invasion-related mechanisms.

RNA-binding protein quaking, a critical regulator of colon epithelial differentiation and a suppressor of colon cancer

BACKGROUND & AIMS

Colon cancer is one of the best understood neoplasms from a genetic perspective, yet it remains the second most common cause of cancer-related death. Post-transcriptional regulation mediated by RNA-binding proteins or microRNAs coordinately targets multiple genes, holding promise involved in colon cancer initiation and development. Here we studied the role of RNA-binding protein quaking (QKI) in colon cancer.

METHODS

We observed the expression pattern of QKI in normal colon and colon cancers through reverse-transcription polymerase chain reaction and Western blot. Bisulfite sequencing and methylation-specific PCR were applied for QKI promoter methylation analysis. We used enterocyte differentiation markers and soft agar assay to test the role of QKI in colon differentiation and colon cancer development. 3' Untranslated region (UTR) reporter assay and RNA-immunoprecipitation were used to confirm the interaction between QKI and beta-catenin or p27.

RESULTS

QKI is significantly down-regulated and even absent in some colon cancers, which is at least partially because of the promoter hypermethylation. Forced expression of QKI in the colon cancer cells increased the expression of enterocyte differentiation marker intestinal alkaline phosphatase and lactase, together with the enhancement of p27Kip1 protein level, and membrane localized beta-catenin. Finally, QKI overexpression reduced the proliferation and tumorigenesis ability.

CONCLUSIONS

Our study establishes that QKI functions as a principal regulator in the differentiation of colon epithelium and a suppressor of carcinogenesis through coordinately targeting multiple genes associated with cell growth and differentiation, whose deregulation by methylation is involved in colon cancer onset and progress.

Sodium butyrate induces human colon carcinoma HT-29 cell apoptosis through a mitochondrial pathway

Some tumours respond favourably to tumour necrosis factor-alpha (TNF-alpha). Despite this preferential sensitivity, resistance to TNF-alpha remains a clinical problem and more interest is now being focused on finding compounds that induce apoptosis through other pathways. Sodium butyrate (NaBt) has anti-tumour effects on colon cancer cells, inhibiting cell growth and promoting differentiation and apoptosis. In this study we investigated whether NaBt induced apoptosis in the human colon cancer cell line HT-29 and examined the intracellular mechanisms involved. Pre-incubation of cells with NaBt significantly increased apoptosis as measured by fluorescence activated cell sorter analysis and mitochondrial membrane potential determination. This effect could be blocked with the caspase inhibitors, z-VAD-fmk (pan-caspase inhibitor), z-DEVD-fmk (caspase-3 inhibitor) and z-LEHD-fmk (caspase-9 inhibitor), but not with z-IETD-fmk (caspase-8 inhibitor). Enhancement of caspase-3 and caspase-9 activities suggests that NaBt induces apoptosis via mitochondrial pathways not involving TNF-alpha.

Calcyclin-binding protein inhibits proliferation, tumorigenicity, and invasion of gastric cancer

Calcyclin-binding protein/Siah-1-interacting protein (CacyBP/SIP), a target protein of the S100 family, which includes S100A6, S100A1, S100A12, S100B, and S100P, has been identified as a component of a novel ubiquitinylation complex leading to beta-catenin degradation. However, the function of CacyBP/SIP in gastric cancer has not been elucidated. In the present study, we prepared CacyBP/SIP overexpressing and knockdown cell lines of gastric cancer. Forced CacyBP/SIP expression inhibited the proliferation of gastric cancer cells, suppressed tumorigenicity in vitro, and prolonged the survival time of tumor-bearing nude mice. In addition, increased CacyBP/SIP repressed the invasive potential of gastric cancer cells. Conversely, the down-regulation of CacyBP/SIP by RNA interference showed the opposite effects. Further studies showed that depressed CacyBP/SIP increased the expression of total and nuclear beta-catenin at the protein level and elevated the transcriptional activity of Tcf/LEF. Taken together, our results suggest that CacyBP/SIP may be a potential inhibitor of cell growth and invasion in the gastric cancer cell, at least in part through the effect on beta-catenin protein expression and transcriptional activation of Tcf/LEF.

Upregulation of p27 and its inhibition of CDK2/cyclin E activity following DNA damage by a novel platinum agent are dependent on the expression of p21

The cisplatin analogue 1R,2R-diaminocyclohexane(trans-diacetato)(dichloro)platinum^IV (DAP) is a DNA-damaging agent that will be entering clinical trials for its potent cytotoxic effects against cisplatin-resistant tumour cells. This cytotoxicity may reside in its ability to selectively activate G1-phase checkpoint response by inhibiting CDKs via the p53/p21 pathway. We have now evaluated the role of another CDK inhibitor p27 as a contributor to DAP-mediated inhibition of G1-phase CDK2 activity. Our studies in ovarian A2780 tumour cells demonstrate that p27 levels induced by DAP are comparable to or greater than those seen for p21. The induction of p27 is not through a transcriptional mechanism, but rather is due to a four-fold increase in protein stabilisation through a mechanism dependent on p21. Moreover, DAP-induced p21 promoted the selective increase of p27 in the CDK2 complex, but not in CDK4 complex, and this selective increase contributed to inhibition of the CDK2 kinase activity. The inhibited complex contained either p27 or p21, but not both, with the relative levels of cyclin E associated with p27 and p21 indicating that about 25% of the inhibition of CDK2 activity was due to p27 and 75% due to p21. This study provides the first evidence that p27 upregulation is directly attributable to activation of the p53/p21 pathway by a DNA-damaging agent, and promulgates p53/p21/p27 axis as a significant component of checkpoint response.

Expression of PPARdelta in multistage carcinogenesis of the colorectum: implications of malignant cancer morphology

Whether peroxisome proliferator-activated receptor (PPAR) delta is a good target for the chemoprevention and/or treatment of colorectal cancer (CRC) remains controversial. Our goal was to examine PPARdelta expression in multistage carcinogenesis of the colorectum and to assess the relevance of PPARdelta in CRC. Immunohistochemical analysis indicated that PPARdelta expression increased from normal mucosa to adenomatous polyps to CRC. In cancer tissues, the PPARdelta protein was accumulated only in those cancer cells with highly malignant morphology, as represented by a large-sized nucleus, round-shaped nucleus, and presence of clear nucleoli. Interestingly, the cancer tissue often contained both PPARdelta-positive and -negative areas, each retaining their respective specific morphological features. Moreover, this pattern persisted even when PPARdelta-positive and -negative cells were aligned next to each other within a single cancer nest or gland and was present in the majority of CRC cases. Immunohistochemistry for Ki-67 proliferation marker showed no significant correlation between Ki-67 and PPARdelta in CRC samples. Based on Western blot analysis and quantitative RT-PCR, high PPARdelta protein expression correlated with high PPARdelta mRNA levels. Peroxisome proliferator-activated receptor delta may have a supporting role in tumorigenesis, and the close association between PPARdelta expression and malignant morphology of CRC cells suggests a pivotal role in cancer tissue.

Role of p21waf1/cip1 in effects of oxaliplatin in colorectal cancer cells

Clinical studies have shown that oxaliplatin, a novel platinum derivative, is a potent chemotherapeutic agent for colorectal cancer when combined with 5-fluorouracil and leucovorin. Although the toxic activity is based on covalent adducts between platinum and DNA, its actual biological behavior is mostly unknown. In an effort to explore the mechanism of tumor susceptibility to oxaliplatin, we examined the cytotoxic effects of oxaliplatin in colorectal cancer cell lines in reference to p53 gene status. Although p53 gene status did not clearly predict sensitivity to oxaliplatin, p53 wild-type cells including HCT116 were sensitive but HCT116 p53-/- were found to be resistant to oxaliplatin. Oxaliplatin caused strong p21waf1/cip1 induction and G0-G1 arrest in p53 wild-type cells, whereas cisplatin did not induce G0-G1 arrest. Assays using p53 wild but p21waf1/cip1 null HCT116 cells revealed that oxaliplatin did not show G0-G1 arrest and reduced growth-inhibitory effects, suggesting that p21waf1/cip1 may be a key element in oxaliplatin-treated p53 wild-type cells. Although HCT116 is DNA mismatch repair-deficient, a mismatch repair-proficient HCT116+ch3 cell line displayed similar responses with regard to p21waf1/cip1-mediated growth inhibition and G0-G1 arrest. In p53 mutant cells, on the other hand, oxaliplatin caused an abrupt transition from G1 to S phase and eventually resulted in G2-M arrest. This abrupt entry into S phase was associated with loss of the p21waf1/cip1 protein via proteasome-mediated degradation. These findings suggest that p21waf1/cip1 plays a role in oxaliplatin-mediated cell cycle and growth control in p53-dependent and -independent pathways.

Adaptative metabolic response of human colonic epithelial cells to the adverse effects of the luminal compound sulfide

Hydrogen sulfide (H(2)S), a bacterial metabolite present in the lumen of the large intestine, is able to exert deleterious effects on the colonic epithelium. The mechanisms involved are still poorly understood, the reported effect of sulfide being its capacity to reduce n-butyrate beta-oxidation in colonocytes. In this work, we studied both the acute effect of the sodium salt of H(2)S on human colonic epithelial cell metabolism and the adaptative response of these cells to the pre-treatment with this agent. Using the human colon carcinoma epithelial HT-29 Glc(-/+) cell model, we found that the acute effect of millimolar concentrations of NaHS was to inhibit l-glutamine, n-butyrate and acetate oxidation in a dose-dependent manner. Using micromolar concentrations of NaHS, a comparable effect but largely reversible was observed for O(2) consumption and cytochrome c oxidase activity. Pre-treatment with 1 mM NaHS induced several adaptative responses. Firstly, increased lactate release and decreased cellular oxygen consumption evidenced a Pasteur-like effect which only partly compensated for the altered mitochondrial ATP production. Thus, a decrease in the proliferation rate with a constant adenylate charge was observed. Secondly, in these pre-treated cells, NaHS induced a hypoxia-like effect on cytochrome c oxidase subunits I and II which were decreased. Thirdly, a mild uncoupling of mitochondrial respiration possibly resulting from an increase of UCP 2 protein was observed. The NaHS antimitotic activity was not due to cellular apoptosis and/or necrosis but to a proportional slowdown in all cell cycle phases. These results are compatible with a metabolic adaptative response of the HT-29 colonic epithelial cells to sulfide-induced O(2) consumption reduction which, through the maintenance of a constant energetic load and an increased mitochondrial proton leak, would participate in the preservation of cellular viability.

Oxaliplatin, a Potent Inhibitor of Survivin, Enhances Paclitaxel-induced Apoptosis and Mitotic Catastrophe in Colon Cancer Cells

BACKGROUND

Clinical studies have demonstrated that oxaliplatin, a novel platinum derivative, is a potent chemotherapeutic agent, especially when combined with other reagents. The aim of the present study was to explore the mechanism of such action.

METHODS

Using colon cancer cell lines, we examined changes in cell cycle, apoptosis and mitotic catastrophe induced by oxaliplatin and/or paclitaxel.

RESULTS

Oxaliplatin at its IC(50) induced apoptosis and cell cycle arrest at G(2)-M phase. Western blot analyses indicated that oxaliplatin decreased mitosis-commencing protein cdc2 and anti-apoptotic proteins, phospho-Bcl(2) and Bcl-xl in the three colon cancer cells tested. Since cdc2 stabilizes survivin, a putative IAP (inhibitor of apoptosis) family member, through phosphorylation of Thr34, we examined the level of survivin and found a marked decrease due to oxaliplatin. This finding is of particular interest because survivin is a promising molecular target against various human cancers and a key molecule involved in both apoptosis and mitotic catastrophe. When used in combination with paclitaxel (taxol), a putative apoptosis-inducing reagent, the isobologram indicated that the taxol-oxaliplatin sequence or taxol plus oxaliplatin had synergic or additive effects, while the oxaliplatin-taxol sequence resulted in a prominent antagonism. The taxol-oxaliplatin sequence caused marked growth inhibition of DLD1 and SW480 cells, possibly due to upregulation of apoptotic and non-apoptotic pathways, respectively. Morphological surveys indicated that the non-apoptotic process could be mitotic catastrophe.

CONCLUSION

Our results suggest that oxaliplatin that potently inhibited survivin may exert outstanding cytotoxic effects when combined with certain chemoreagents through enhancement of apoptosis and mitotic catastrophe.

Short-chain fatty acids and colon cancer cells: the vitamin D receptor--butyrate connection

Butyrate and its prodrug tributyrin, as well as 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), have important physiological effects on proliferation and differentiation in a variety of malignant cells. The aim of this study was to elucidate the role of the vitamin D receptor (VDR) in butyrate-induced cell differentiation and cell cycle arrest in Caco-2 cells, a human colon cancer cell line. Cell differentiation was evaluated by analyzing the activity of alkaline phosphatase (AP). Protein of VDR, cyclins, cyclin-dependent kinases (cdks) and of cdk inhibitors was quantified by Western blot analysis, VDR-mRNA by PCR. Pre- and postconfluent cells were assessed for VDR binding activity. Cell cycle was analyzed by flow cytometry. Tributyrin significantly increased VDR-mRNA level (250% vs. control) and VDR binding activity. Butyrate also enhanced VDR protein content in the nucleus in a time- and dose-dependent manner and more potently than other short-chain fatty acids of a related structure. Both butyrate (640% vs. control) and 1,25-(OH)2D3 (350% vs. control) significantly stimulated differentiation, whereas combined treatment with butyrate and 1,25-(OH)2D3 resulted in a synergistic amplification of AP activity (1400% vs. control). In the presence of the VDR antagonist ZK 191732, butyrate-induced differentiation was completely abolished (150% vs. control). While butyrate alone increased p21Waf1/Cip1 expression and down-regulated cdk 6 and cyclin A, and combined exposure with 1,25-(OH)2D3 resulted in a synergistic enhancement of butyrate-induced changes, expressions did not change from control level after treatment with butyrate and ZK 191732. G1 cell cycle arrest induced by butyrate was also abolished after combined treatment with butyrate and ZK 191732. In conclusion, differentiation and cell cycle arrest of Caco-2 cells induced by butyrate are mediated by up-regulation of VDR, followed by a stimulation of the negative cell cycle regulator p21Waf1/Cip1 and by a down-regulation of cdk 6 and cyclin A, both involved in cell cycle progression.

Temporal distribution of CDK4, CDK6, D-type cyclins, and p27 in developing mouse oocytes

Various molecular interactions not operating in other cell types are most likely required for mammalian oocytes to develop into fully competent eggs. This study seeks to initiate analyses of the potential oocyte-specific functions of regulators of G1/S progression-CDK4, CDK6, D-type cyclins, and p27-by first determining their expression patterns in growing and maturing mouse oocytes and in mouse embryos early after fertilization. Western blot and immunofluorescence analyses on isolated oocytes were employed to evaluate both their levels and their localization. The data show that 1). mouse oocytes contain significant amounts of all studied regulators; 2). their amounts and localization undergo dramatic changes as the oocytes grow, meiotically mature, and transit into embryogenesis; and 3). some regulators (CDK4, CDK6, cyclin D2, and p27) appear in unusual, most likely posttranslationally modified, forms. These data distinguish G1/S regulators as the potential players in molecular processes that are important for oocytes to function normally.

JTE-522, a cyclooxygenase-2 inhibitor, is an effective chemopreventive agent against rat experimental liver fibrosis1

BACKGROUND & AIMS

The aim of this study was to assess the effects of cyclooxygenase (COX)-2 inhibition on rat experimental liver fibrogenesis.

METHODS

We investigated the inhibitory effects of a selective COX-2 inhibitor, JTE-522, on liver fibrosis induced by a choline-deficient, l-amino acid-defined diet (CDAA). Inhibitory effect was also tested in a second model of thioacetamide (TAA)-induced liver fibrosis.

RESULTS

CDAA induced liver fibrosis and preneoplastic foci at 12 weeks and cirrhosis at 36 weeks. Hepatocellular carcinoma was noted in 13 of 15 rats (87%). JTE-522 significantly inhibited fibrosis and development of preneoplastic lesions in a dose-dependent manner and completely inhibited generation of cirrhosis and hepatocellular carcinoma at both low and high doses (10 and 30 mg/kg body wt/day, respectively). JTE-522 administrated only from 12 weeks to 36 weeks also prevented cirrhosis and formation of hepatocellular carcinoma. JTE-522 itself did not cause local or systemic gross or histopathologic changes at 36 weeks. Mechanistic studies indicated that the CDAA model displayed up-regulation of several biomarkers, including COX-2, arachidonate metabolite (prostaglandin E(2)), serum aspartate aminotransferase, and c-myc expression. The model also showed an increased proportion of activated hepatic stellate cells, proliferating cell nuclear antigen index, and CD45-positive inflammatory cells in the liver. JTE-522 effectively diminished these changes. JTE-522 exhibited similar antifibrosis effects in the TAA model.

CONCLUSIONS

Our results suggest that COX-2 is involved in CDAA- and TAA-induced liver fibrosis. Our data also indicate that JTE-522 is a potent chemopreventive agent of rat liver fibrosis with low toxicity.

Growth arrest of HPV-positive cells after histone deacetylase inhibition is independent of E6/E7 oncogene expression

Inhibitors of histone deacetylase (HDAC) are capable of arresting growth in cervical carcinoma cells in the G1 phase of the cell cycle. Although HPV E6/E7 mRNA steady-state levels appeared to be constant after prolonged treatment, time-course experiments revealed that viral transcription was transiently down-regulated between 7-10 h prior to cdk2 suppression. To test whether transitory suppression was a prerequisite for the biological outcome after HDAC inhibition, we took advantage of two immortalized human keratinocyte cell lines in which E6/E7 oncogene expression was controlled by different regulatory regions. After treatment with sodium butyrate (NaB) or trichostatin A (TSA), HPV16 upstream regulatory region (URR)-directed transcription was down-regulated, showing kinetics similar to those in cervical carcinoma cells. In contrast, beta-actin promoter controlled E6/E7 transcription was even temporarily increased and finally declined to levels initially detected in the untreated controls. Both cell lines, however, were arrested in G1 and showed complete suppression of cdk2 activity that was preceded by a strong up-regulation of the cdk2 inhibitors p21(CIP1) and p27(KIP1). These results demonstrate that growth of HPV16/18-positive cells can be arrested by HDAC inhibitors despite ongoing HPV transcription and thus independently of any potential position effects uncoupling URR-directed gene expression by adjacent cellular promoters or by downstream 3'-polyadenylation sites after viral integration into the host genome during multistep carcinogenesis.

Low level of p27(Kip1) protein expression in gastric adenocarcinoma is associated with disease progression and poor outcome

BACKGROUND AND OBJECTIVES

Low tumor expression of the p27(Kip1) protein, which is involved in cell cycle control and apoptosis, is considered a negative prognostic factor in different types of cancer. The aim of this study was to evaluate the clinical and pathological significance of low p27(Kip1) protein expression in patients who had undergone resection for gastric adenocarcinoma.

METHODS

p27(Kip1) protein was studied by immunohistochemistry in formalin-fixed tumor sections from 95 patients who underwent resection for gastric adenocarcinoma between 1991 and 1996. Based on the median value of protein expression, p27(Kip1) protein expression was classified as low or high.

RESULTS

Low p27(Kip1) protein expression was significantly associated with tumor de-differentiation, increased penetration through the gastric wall, lymph node metastasis, and advanced tumor stage. In the group of 84 patients who underwent curative surgery, 5-year survival was 74% in cases with high p27(Kip1) protein expression and 38% in those with low p27(Kip1) protein expression (P < 0.001). At multivariate analysis, low p27(Kip1) protein expression was an independent negative prognostic factor for survival (RR = 3.671; P = 0.004).

CONCLUSIONS

In gastric adenocarcinoma, low p27(Kip1) protein expression is associated with poorly differentiated and advanced tumors and is a negative prognostic factor of potential clinical value.

Comparison of the expression of p53, p21, Bax and the induction of apoptosis between patients with basal cell carcinoma and normal controls in response to ultraviolet irradiation

AIM

Ultraviolet light (UV) is known to cause DNA damage in the epidermis. The damaged DNA is repaired or deleted by apoptosis to prevent the generation of cancer. It has been suggested that a deficient apoptotic mechanism may predispose individuals to skin cancer. Therefore, the response of normal controls and patients with basal cell carcinoma (BCC) to UV irradiation was investigated.

METHODS

The buttock skin from normal volunteers and patients with BCC was irradiated using solar simulated radiation (SSR). SSR mimics the effect of natural sunlight. Skin biopsies were excised and examined for p53, p21, and Bax protein expression and for the induction of apoptosis.

RESULTS

At 33 hours after UV irradiation, the induction of apoptosis was significantly higher (p = 0.04) in patients with BCC than in normal volunteers (Mann Whitney test). A trend towards higher p21 expression was found at 33 hours in patients with BCC (mean, 18.69 positive cells/field) than in normal volunteers (mean, 9.89), although this difference was not significant (p = 0.05 positive cells/field).

CONCLUSION

These results may imply that patients with BCC have enhanced sensitivity to UV irradiation or that there is some defect in the cell arrest or repair pathways, which results in damaged cells been pushed into apoptosis rather than repair.

Pathway-specific tumor suppression. Reduction of p27 accelerates gastrointestinal tumorigenesis in Apc mutant mice, but not in Smad3 mutant mice

Expression of the cyclin-dependent kinase inhibitor p27(Kip1) (p27) is frequently reduced in human colorectal cancer, and this correlates with poor patient prognosis. To clarify the role of p27 in gastrointestinal (GI) cancer, we measured p27 expression, as well as the effect of germline deletion of p27, in 3 different mouse models of GI neoplasia. p27 expression was frequently reduced in GI tumors arising in 1,2-dimethylhydrazine (DMH) treated mice, and in Apc mutant Min/+ mice, but not in GI tumors arising in Smad3 mutant mice. Germline deletion of p27 resulted in accelerated tumor development and increased tumor cell proliferation in both DMH treated and Min/+ mice, but not in Smad3 mutant mice. p27 deficiency also led to increased adenoma to adenocarcinoma progression. These results indicate that reduction of p27 cooperates with mutations in Apc but not in Smad3 during GI tumorigenesis. Thus, tumor suppression by p27 is contingent on the specific oncogenic pathway that drives tumor development.

Insulin-like growth factor-I has a biphasic effect on colon carcinoma cells through transient inactivation of forkhead1, initially mitogenic, then mediating growth arrest and differentiation

IGF-I stimulates intestinal cell differentiation after initiating a short proliferative burst, similar to its effect on muscle cell differentiation. Levels of IGF-I attainable in serum (10-20 ng/ml) induced transient growth stimulation of colon carcinoma cells, then growth arrest. When IGF-I functioned as a mitogen, it blocked differentiation. Intestinal cell differentiation occurred once cells had undergone the IGF-I-initiated growth arrest and IGF-I and butyrate acted synergistically to induce maturation markers. IGF-I induces NIH-3T3 cell proliferation and survival by activating the kinase akt, which in turn inhibits various apoptotic mediators and the forkhead family of transcription factors, which mediate expression of p27(kip1). Promoter reporter assays demonstrated that forkhead1 mediates transcription of p27(kip1) in colon carcinoma cells. The mitogenic effects of IGF-I on 4 colon carcinoma cell lines were transient because the inactivating phosphorylation of forkhead1 by akt was short-lived. This allowed transcriptional upregulation of the cdk inhibitor p27(kip1), with a resulting growth arrest. In contrast, in NIH-3T3 cells treated in parallel with identical IGF-I levels, forkhead phosphorylation levels were sustained; thus, no increase in p27(kip1) levels was seen and cells continued to proliferate. Intestinal epithelial cells in vivo undergo a limited number of divisions, then growth arrest and completion of their maturation. IGFs found in intestinal tissue may control the timing of this process. In addition, colon cancers may have developed strategies to overcome IGF-I-mediated growth arrest. Earlier (Kansra et al., Int J Cancer 2000;87:373-8), we found that levels of IGFBP-3 were elevated at least 2-fold in 70% of resected colon cancers compared with adjacent normal tissue. In the current study, growth inhibition by IGF-I and IGF-II was blocked by concurrent addition of IGFBP-3, implying that colon cancers with elevated IGFBP-3 levels would be selected for in vivo because they could bind and inactivate high serum IGF-I levels and continue to proliferate.

Differential roles of p21(Waf1) and p27(Kip1) in modulating chemosensitivity and their possible application in drug discovery studies

In this study, the differential role of the cyclin-dependent kinase (CDK) inhibitors p21(Waf1) and p27(Kip1) in cell cycle regulation was proposed for use in screening natural or synthetic compounds for cell cycle-dependent (particularly M phase-dependent) antineoplastic activity. p21(Waf1) or p27(Kip1) was ectopically expressed with an ecdysone-inducible mammalian expression system in a human colon adenocarcinoma cell line. Induction of p21(Waf1) or p27(Kip1) expression inhibited the activities of CDK2 and completely arrested cells at G(1) phase of the cell cycle by p27(Kip1) and at G(1) and G(2) phases by p21(Waf1). We examined the sensitivity of these cells to several antineoplastic agents known to be cell cycle-dependent or -independent. Substantially increased resistance to cell cycle-dependent antineoplastic agents was found in the cells when the expression of p21(Waf1) or p27(Kip1) was induced. In contrast, only a desensitization to cell cycle-independent antineoplastic agents was found in the cells arrested by p21(Waf1) or p27(Kip1). Because p21(Waf1) induces an additional block at G(2) phase that inhibits cell entry into M phase, we further examined the difference between p21(Waf1)- and p27(Kip1)-induced cells in their sensitivity to D-24851, a novel M phase-dependent compound. We found that induction of p21(Waf1) after exposure of the cells to D-24851 conferred stronger resistance than did induction of p27(Kip1). Taken together, our results suggest that the differential effect of p21(Waf1) and p27(Kip1) on cell cycle regulation may be advantageous for screening chemical libraries for novel antineoplastic candidates that are cell cycle-dependent, and M phase-dependent in particular.

Clinical significance of CDC25A and CDC25B expression in squamous cell carcinomas of the oesophagus

CDC25A, CDC25B and CDC25C belong to a family of protein phosphatases which activate the cyclin-dependent kinase at different points of the cell cycle. According to accumulating evidence, CDC25A and CDC25B seem to possess oncogenic properties. We have analysed these expressions by immunohistochemistry, western blot and RT-PCR in a series of 100 patients with squamous cell carcinoma of the oesophagus. When compared with non-cancerous cells, CDC25A and CDC25B were strongly expressed in the cytoplasm of cancer cells, with positive (+) classification in 46% (46 cases) and 48% (48 cases), respectively. There was no significant correlation between CDC25A and CDC25B expression, nor was there any association with the expression of other cell cycle-regulating molecules, including cyclin D1, Rb, p16(INK4), p27(KIP1)and PCNA (proliferating cell nuclear antigen). CDC25A (+), as well as CDC25B (+), was more frequently found in patients with deeper tumour invasion and lymph node metastasis, while tumour size was correlated only with CDC25A expression. Postoperative survival was significantly poorer for CDC25A (+) patients than CDC25A (-) patients, but was not affected by the CDC25B status. Nuclear localization of CDC25A was observed in 51 cases (51%), regardless of its cytoplasmic expression, and was not associated with clinico-pathological factors or prognosis. Multivariate analysis revealed only the CDC25A status to be an independent significant prognostic factor among these biological and clinico-pathological factors. CDC25A but not CDC25B may be a new prognostic factor for squamous cell carcinoma of the oesophagus. Thus, regulation of the G1 checkpoint in the cell cycle may be important in oesophageal carcinogenesis, which may also involve many other oncogenes.

HMG-CoA reductase inhibitor mevastatin enhances the growth inhibitory effect of butyrate in the colorectal carcinoma cell line Caco-2

Mevastatin is an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in cholesterol synthesis. Butyrate, a short-chain fatty acid, reduces proliferation and induces differentiation of human colon cancer cells. The aim of our study was to determine the effect of mevastatin, alone or in combination with butyrate, on proliferation, the cell cycle and apoptosis in the human colorectal carcinoma cell line Caco-2. In this report we show that mevastatin combined with butyrate synergistically suppressed growth of Caco-2 cells in a dose- and time-dependent manner. In addition, incubation with mevastatin arrested cells in the G1 phase of the cell cycle after 24 h with a switch to the G2/M phase after 72 h. This was accompanied by a down-regulation of cyclin-dependent kinases (cdk) 4 and cdk 6 as well as cyclin D1, while cdk 2 and cyclin E protein levels remained unchanged during mevastatin treatment. Cell cycle inhibitors p21 and p27 were significantly upregulated by mevastatin. The proapoptotic properties of mevastatin were further enhanced by co-incubation with butyrate. Lastly, the effects of mevastatin could be reversed by addition of mevalonate, but not farnesyl- or geranylgeranylpyrophosphate, intermediate products of cholesterol synthesis, to the medium. These results suggest that HMG-CoA reductase inhibitors like mevastatin may enhance the antiproliferative effect of butyrate in colon cancer cells via induction of apoptosis together with a G0/G1 cell cycle arrest.

1,25-Dihydroxycholecalciferol enhances butyrate-induced p21(Waf1/Cip1) expression

Butyrate, a short-chain fatty acid produced in the colon, as well as its prodrug tributyrin, reduce proliferation and increase differentiation of colon cancer cells. p21(Waf1/Cip1) and p27(Kip1) are negative regulators of cell cycle and are thought to have a key function in the differentiation of various cell lines. We studied the effects of butyrate on differentiation, VDR expression, as well as on p21(Waf1/Cip1) and p27(Kip1) expression in human colon cancer cells (Caco-2). Butyrate induced cell differentiation, which was further enhanced after addition of 1,25-dihydroxycholecalciferol. Synergistic effect of butyrate and dihydroxycholecalciferol in Caco-2 cells was due to butyrate-induced overexpression of VDR. While butyrate as well as dihydroxycholecalciferol increased p21(Waf1/Cip1) and p27(Kip1) expression, in contrast combined exposure of butyrate and dihydroxycholecalciferol resulted in a synergistic amplification of p21(Waf1/Cip1), but not of p27(Kip1) expression. These data imply that butyrate selectively increases p21(Waf1/Cip1) expression via upregulation of VDR in Caco-2 cells.

p27(Kip1): regulation and function of a haploinsufficient tumor suppressor and its misregulation in cancer

A major function of p27, also known as Kip1, is to bind and inhibit cyclin/cyclin-dependent kinase complexes, thereby blocking cell cycle progression. As p27 operates at the heart of the cell cycle, it is perhaps not surprising that it is emerging as a key player in multiple cell fate decisions including proliferation, differentiation, and cell death. The central role of p27 makes it important in a variety of disease processes that involve aberrations in cellular proliferation and other cell fates. Most notable among these processes is neoplasia. A large number of studies have reported that p27 expression is frequently downregulated in human tumors. In most tumor types, reduced p27 expression correlates with poor prognosis, making p27 a novel and powerful prognostic marker. In addition to these practical implications, murine and tissue culture models have shown that p27 is a potent tumor suppressor gene for multiple epithelially derived neoplasias. Loss of p27 cooperates with mutations in several oncogenes and tumor suppressor genes to facilitate tumor growth, indicating that p27 may be a "nodal point" for tumor suppression. In contrast to most tumor suppressor genes studied to date, which are recessive at the cellular level, p27 is haploinsufficient for tumor suppression. The fact that tumor suppression by p27 is critically dependent on the absolute level of p27 expression indicates that p27 acts as a rheostat rather than as an on/off switch to control growth and neoplasia.

Modulation of cell cycle-related protein expression by sodium butyrate in human non-small cell lung cancer cell lines

To elucidate the mechanism of action of sodium butyrate (NaB), we examined its effect on the expression of some cell cycle-related proteins (cyclins D1 and E, p16(ink4), p21(waf1), p27(kip1)) in 2 human non-small cell lung cancer cell lines (NCI-460 and NCI-H23) characterized by wild- type and mutant TP53, respectively. The growth of both cell lines was inhibited in a dose-dependent manner and this process was accompanied by a modulation of cell cycle-related proteins. In NCI-H460, the p27(kip1) and p16(ink4) protein levels were markedly increased following NaB treatment, whereas p21(waf1) was only slightly elevated, with a peak at 2 mM NaB, and p53 was unaffected by any concentration. By contrast, in NCI-H23, a marked increase in p21(waf1) protein was paralleled by decreased p53 levels, whereas all the other investigated proteins remained stable. The results suggest that NaB blocks the growth of both cell lines by induction of cyclin-dependent kinase inhibitors (in particular, p21(waf1) in NCI-H23 and p27(kip1) and p16(ink4) in NCI-H460) through a p53-dependent or p53-independent mechanism, and open up interesting perspectives for the use of NaB as an alternative or additional strategy in the treatment of non-small cell lung carcinoma.

Butyrate-induced differentiation of Caco-2 cells occurs independently from p27

Butyrate, a short-chain fatty acid produced in the colon, reduces proliferation and increases differentiation of colon cancer cells. p27, an inhibitor of cyclin-dependent kinases and a negative regulator of the cell cycle, is thought to have a key function in the differentiation of various cell lines. The objective of the present study was to elucidate the role of p27 in butyrate-induced differentiation of the human colorectal carcinoma cell line Caco-2. In this report we show that in spite of the increase in p27 protein expression after incubation with the HMG-CoA reductase inhibitor mevastatin, alkaline phosphatase activity decreases significantly in this cell line. In addition, mevastatin caused a significant increase in the cell cycle inhibitor p21. All effects could be reversed by addition of mevalonate to the medium. Taken together, we provide the first evidence that in Caco-2 cells p27 may have other functions apart from the regulation of cell differentiation.

Role of p27(Kip1) in human intestinal cell differentiation

BACKGROUND & AIMS

Growth arrest and differentiation are generally considered to be temporally and functionally linked phenomena in the intestinal epithelium.

METHODS

To delineate the mechanism(s) responsible for the loss of proliferative potential as committed intestinal cells start to differentiate, we have analyzed the regulation of G(1)-phase regulatory proteins in relation to differentiation in the intact epithelium as well as in well-established intestinal cell models that allow the recapitulation of the crypt-villus axis in vitro.

RESULTS

With intestinal cell differentiation, we have observed an induction of the cell cycle inhibitors p21(Cip), p27(Kip1), and p57(Kip2) expression with an increased association of p27(Kip1) and p57(Kip2) with cyclin-dependent kinase 2 (Cdk2). At the same time, there was an accumulation of the hypophosphorylated form of the pRb proteins and a strong decline in Cdk2 activity. Stable expression of a p27(Kip1) antisense complementary DNA in Caco-2/15 cells did not prevent growth arrest induced by confluence, but repressed villin, sucrase-isomaltase, and alkaline phosphatase expression.

CONCLUSIONS

Our results indicate that the growth arrest that precedes differentiation involves the activation of Rb proteins and the inhibition of Cdk2. Furthermore, intestinal cell differentiation apparently requires a function of p27(Kip1) other than that which leads to inhibition of Cdks.

Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium

Members of the protein kinase C (PKC) family of signal transduction molecules have been widely implicated in regulation of cell growth and differentiation, although the underlying molecular mechanisms involved remain poorly defined. Using combined in vitro and in vivo intestinal epithelial model systems, we demonstrate that PKC signaling can trigger a coordinated program of molecular events leading to cell cycle withdrawal into G(0). PKC activation in the IEC-18 intestinal crypt cell line resulted in rapid downregulation of D-type cyclins and differential induction of p21(waf1/cip1) and p27(kip1), thus targeting all of the major G(1)/S cyclin-dependent kinase complexes. These events were associated with coordinated alterations in expression and phosphorylation of the pocket proteins p107, pRb, and p130 that drive cells to exit the cell cycle into G(0) as indicated by concomitant downregulation of the DNA licensing factor cdc6. Manipulation of PKC isozyme levels in IEC-18 cells demonstrated that PKCalpha alone can trigger hallmark events of cell cycle withdrawal in intestinal epithelial cells. Notably, analysis of the developmental control of cell cycle regulatory molecules along the crypt-villus axis revealed that PKCalpha activation is appropriately positioned within intestinal crypts to trigger this program of cell cycle exit-specific events in situ. Together, these data point to PKCalpha as a key regulator of cell cycle withdrawal in the intestinal epithelium.

Microsatellite instability and Epstein-Barr virus infection in gastric remnant cancers

Clinicopathological analysis, microsatellite analysis, detection of Epstein-Barr virus (EBV), and immunohistochemistry on p53 protein were performed in 26 cases of gastric remnant cancer (GRC). They were divided into two groups; Group A (n = 14) who had undergone a primary gastrectomy for benign gastric disease, and Group B (n = 12) who had undergone the same operation for gastric cancer. EBV infection was present in 29% of Group A, 8% of Group B and 6% of the conventional gastric carcinoma (CGC) (Group A vs CGC, P = 0.01). Microsatellite instability (MSI) was found in 7% of Group A, 25% of Group B, and 9% of the CGC (Group B vs CGC; P = 0.08). p53 Overexpression was observed in 46% of the GRC and 33% of the CGC. p53 Overexpression was observed in 90% of the intestinal type of GRC, but in only 20% of the diffuse type of GRC (P = 0.002). The cancer stage was a significant factor in the univariate analysis of survival (P = 0.04). In conclusion, GRC is different from CGC in terms of MSI or EBV association. The pathogenetic differences between the two groups require further investigation. EBV infection may have been involved in the carcinogenesis of Group A. MSI may be an important factor in the carcinogenesis of metachronous multiple gastric cancer (Group B).

Multiple functions of p27(Kip1) and its alterations in tumor cells: a review

Cyclin-dependent kinases (CDKs), together with cyclins, their regulatory subunits, govern cell-cycle progression in eukaryotic cells. p27(Kip1) is a member of a family of CDK inhibitors (CDIs) that bind to cyclin/CDK complexes and arrest cell division. There is considerable evidence that p27(Kip1) plays an important role in multiple fundamental cellular processes, including cell proliferation, cell differentiation, and apoptosis. Moreover, p27(Kip1) is a putative tumor-suppressor gene that appears to play a critical role in the pathogenesis of several human malignancies and its reduced expression has been shown to correlate with poor prognosis in cancer patients. This study reviews current information on the functions of p27(Kip1), its abnormalities found in human tumors, and the possible clinical implications of these findings with respect to the management of cancer patients.

Reduced expression of the cell-cycle inhibitor p27Kip1 is associated with progression and lymph node metastasis of gastric carcinoma

AIMS

p27Kip1 (p27), a cyclin-dependent kinase inhibitor, plays an important role as inhibiting the progression of the cell cycle. Decreased expression of p27 is associated with high histological grade and aggressiveness of several human tumours. We aimed to evaluate the role of p27 in the progression and metastasis of gastric carcinoma.

METHODS AND RESULTS

We analysed the expression of p27 in 67 primary gastric carcinomas and 31 lymph node metastases by immunohistochemistry. Reduced expression of p27 was found more frequently in advanced gastric cancer (40.9%) than in early gastric cancer (15.6%) (P < 0.001). Decreased p27 expression correlated with large tumour size, high histological grade, lymphatic invasion, advanced stage, deep invasion, lymph node metastasis and recurrence. The expression of p27 showed an inverse correlation with the Ki67 labelling index. There was a significant reduction of p27 expression in metastatic tumour cells in lymph nodes (mean positive cells: 3. 7%) when compared to the corresponding primary gastric carcinomas (mean positive cells: 8.1%) (P = 0.008).

CONCLUSIONS

Alterations of p27 expression may play an important role in the progression and metastasis to lymph node of tumour cells in human gastric carcinoma.

Expression of insulin-like growth factor-1 receptor (IGF-1R) and p27Kip1 in melanocytic tumors: a potential regulatory role of IGF-1 pathway in distribution of p27Kip1 between different cyclins

Insulin-like growth factor-1 receptor (IGF-1R) has been shown to be important for melanoma cell growth and survival. In this study we first show, using immunohistochemistry, that progression from benign nevi to malignant melanoma is paralleled by an increased expression of IGF-1R and a down-regulation of the cyclin-dependent kinase inhibitor p27Kip1. Even though the expression of p27Kip1 was drastically reduced compared to benign tumors, detectable amounts of it could be assayed by Western blotting in cultured melanoma cells. To analyze whether there is a causative relationship between the IGF-1 pathway and p27Kip1 expression, melanoma cells were treated with alpha IR-3, an antibody blocking the IGF-1 binding to IGF-1R, or Tunicamycin, which inhibits the translocation of IGF-1R to the cell surface. From these studies we could conclude that the overall expression of p27Kip1 is independent of the IGF-1 pathway. In contrast, the association of p27Kip1 with the different cyclins was drastically affected. Both TM and alpha IR-3 decreased the binding of p27Kip1 to cyclin D1, whose expression was drastically reduced. On the other hand there was an increased binding of p27Kip1 to cyclin E and cyclin A. This redistribution of p27Kip1 may be a mechanism for growth arrest and induction of apoptosis following interruption of the IGF-1 pathway in melanoma cells.

Reduced expression and altered subcellular localization of the cyclin-dependent kinase inhibitor p27(Kip1) in human colon cancer

The p27(Kip1) protein is a negative regulator of the cell cycle and a potential tumor suppressor gene. Reduced expression of the p27(Kip1) protein has been reported in several human tumors and has been associated with higher tumor grade and increased mortality in breast, lung, colon, prostate, bladder, and gastric cancers. On the other hand, increased expression of the p27(Kip1) protein, in the absence of gene mutation, has been observed in primary colon and breast cancers. It was recently suggested that sequestration in the cytoplasm might be an alternative way to inactivate p27(Kip1)-associated inhibitory activity. This study was undertaken to further evaluate p27(Kip1) expression in primary colon tumors and to verify whether differences exist between normal and cancer tissues in terms of subcellular localization of this protein. Both normal and neoplastic tissues expressed variable amounts of the p27(Kip1) protein, as assessed by western blot analyses. Although the mean values were not different between tumor and normal mucosa samples, the expression of total p27(Kip1) was reduced in a subset of tumors. Decreased levels of total p27(Kip1) were associated with high tumor grade (P=0.03) and stage (P=0.04). Moreover, while there was no significant difference in nuclear p27(Kip1), the amount of p27(Kip1) in the cytoplasmic fraction was significantly higher in the tumor samples than in the normal mucosa samples (P=0.0001). These results suggest that p27(Kip1) expression is lost in a subset of colorectal tumors and that alterations in the subcellular localization of this protein might play a role in colon carcinogenesis.

p27 expression in inflammatory bowel disease-associated neoplasia. Further evidence of a unique molecular pathogenesis

The cyclin-dependent kinase inhibitor p27 is a negative regulator of the transition from G1 to S phase of the cell cycle, protects against inflammatory injury and promotes epithelial differentiation. Because p27 protein has been shown to be abnormally expressed both in dysplasia associated with Barrett's esophagus and in sporadic colorectal adenomas, we used immunohistochemistry to evaluate p27 expression in inflammatory bowel disease (IBD)-associated dysplasia and carcinomas. Normal, inflamed, and transitional mucosa, sporadic adenomas, and sporadic colonic carcinomas were studied as controls. In normal colonic epithelium p27 expression was restricted to the superficial, terminally differentiated cells. In colitic and inflamed diverticular mucosa p27 was expressed in the base of the crypts in 86 and 70% of cases, respectively. Similarly, in transitional mucosa adjacent to sporadic carcinomas p27 was expressed in the base of the crypts in all cases. Strong p27 expression extended more frequently from the base of the crypts to superficial cells in IBD-associated dysplasia than in sporadic adenomas (P < 0.007). Twenty of 20 (100%) IBD-associated carcinomas showed low p27 expression (<50% nuclei positive) compared to 6 of 20 (30%) stage-matched sporadic colorectal carcinomas (P < 0.001). We conclude (i) aberrant p27 protein expression in inflamed and IBD-associated nondysplastic mucosa is indistinguishable from that found in transitional mucosa adjacent to sporadic carcinomas; (ii) p27 is overexpressed in dysplastic lesions, perhaps as an attempt to counterbalance proliferative stimuli; and (iii) IBD-associated colorectal carcinomas have significantly lower p27 expression, commonly associated with poor prognosis, than stage-matched sporadic colorectal carcinomas. These findings further substantiate the existence of divergent molecular pathogenetic pathways between these types of carcinomas and suggest an intrinsically more aggressive behavior of IBD-associated colon carcinomas compared to sporadic ones.