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

Bacterial protein MakA causes suppression of tumour cell proliferation via inhibition of PIP5K1α/Akt signalling

Recently, we demonstrated that a novel bacterial cytotoxin, the protein MakA which is released by Vibrio cholerae, is a virulence factor, causing killing of Caenorhabditis elegans when the worms are grazing on the bacteria. Studies with mammalian cell cultures in vitro indicated that MakA could affect eukaryotic cell signalling pathways involved in lipid biosynthesis. MakA treatment of colon cancer cells in vitro caused inhibition of growth and loss of cell viability. These findings prompted us to investigate possible signalling pathways that could be targets of the MakA-mediated inhibition of tumour cell proliferation. Initial in vivo studies with MakA producing V. cholerae and C. elegans suggested that the MakA protein might target the PIP5K1α phospholipid-signalling pathway in the worms. Intriguingly, MakA was then found to inhibit the PIP5K1α lipid-signalling pathway in cancer cells, resulting in a decrease in PIP5K1α and pAkt expression. Further analyses revealed that MakA inhibited cyclin-dependent kinase 1 (CDK1) and induced p27 expression, resulting in G2/M cell cycle arrest. Moreover, MakA induced downregulation of Ki67 and cyclin D1, which led to inhibition of cell proliferation. This is the first report about a bacterial protein that may target signalling involving the cancer cell lipid modulator PIP5K1α in colon cancer cells, implying an anti-cancer effect.

Clinicopathological significance and prognostic value of P27 expression in gastric cancer patients: a meta-analysis

Loss of P27 expression correlates with clinical progression in a variety of human cancers. However, the correlation between P27 expression and gastric cancer remains controversial. In this meta-analysis, we performed an electronic search based on six databases to select a sufficient number of studies. Pooled hazard ratio (HR) was used as estimates to investigate the association between P27 expression and prognosis of patients with gastric cancer. We identified 19 studies with 2387 gastric cancer patients, ranging between 50 and 316 samples per study. Q and I2 tests demonstrated that the homogeneity among 19 studies (I2 = 47%, P = 0.0004), thus we applied a fixed-effects model to calculate the pooled HR of P27expression and overall survival (OS) of gastric cancer patients was 0.68, and 95% confidence interval (CI) was 0.60-0.78. Next, we conducted a subgroup meta-analysis and found that patients with low P27 expression in Asians (HR = 0.69, 95% CI: 0.58-0.82) and non-Asians (HR = 0.57, 95% CI: 0.41-0.79) had poor prognosis. In addition, we found the publication bias results of OS in the final included 19 studies showed that this funnel plot presented incomplete symmetry, and then removed three literatures with larger HRs bias, and found that the remaining 16 literatures were homogeneity (I2 = 0%, P = 0.47), the pooled HR was 0.52 with 95% CI of 0.43-0.62, and the publication bias disappeared. These results suggested a strong association between P27 underexpression and poorer prognosis of gastric cancer in patients. P27 may be a tumor suppressor for predicting survival outcome of gastric cancer patients.

Expression of p27 and p16 and their clinical significance in gastric cancer

BACKGROUND

Deregulated expression of cell cycle regulators p27 and p16 is associated with cancer progression. p27^kip1 and p16^INKa are a cyclin dependent kinase inhibitor whose major target is the cyclinE/CDK2 and cyclinD/CDK4/6 complex, respectively, that governs cell cycle transition from late G1 to S phase.

METHODS

We recruited biopsies of a total of 84 subjects including 72 primary tumor biopsies from histopathologically proven gastric carcinoma, 8 adjacent controls and 12 independent controls. We used gastric cancer cell line, AGS, for validation of our data. Expression profiling at transcript level was done by semi-quantitative RT-PCR and at proteome level by immunohistochemistry and immunofluorescence. Receiver operator characteristics analysis was done for determining the diagnostic utility of p27 and p16 with respect to the sensitivity and specificity.

RESULTS

We demonstrate that p27 and p16 are frequently over expressed in early stages of gastric carcinoma. Our semi-quantitative data show a significant upregulation of p27 (Mean ± SEM, 0.4771 ± 0.0895; p = 0.0001) and p16 (Mean ± SEM, 0.4676 ± 0.04305; p = 0.0001) at mRNA level. Concordant to semi-quantitative data, immunohistochemistry data also showed a significant upregulation of p27 (Mean ± SEM, 196.4 ± 10.84; p < 0.0001) and p16 (Mean ± SEM, 100.4 ± 23.71; p < 0.0001) at protein level.

CONCLUSIONS

The present study showed that the significant upregulation of p27 and p16 were associated with early events in gastric carcinogenesis. Our data suggests that clinical correlation of these differentially expressed genes may be useful as diagnostic biomarkers for early detection of gastric carcinoma and promising therapeutics target for GC patients.

Knockdown of CRM1 inhibits the nuclear export of p27(Kip1) phosphorylated at serine 10 and plays a role in the pathogenesis of epithelial ovarian cancer

In a previous study, the nuclear export protein chromosomal region maintenance (CRM1) was correlated with p27(Kip1) in glioma. The aims of the present study were to investigate the expression of CRM1 and pSer10p27 and their functional roles in epithelial ovarian cancer (EOC) tissues. Using immunohistochemical analysis, CRM1 and pSer10p27 expression levels were shown to be associated with histologic stage and grade (P<0.05). High CRM1 and pSer10p27 expression levels were prognostic indicators of overall survival (P<0.05). Knockdown of CRM1 and pSer10p27 expression arrested cell cycle progression and inhibited the proliferation of SKOV3 cells both in vitro and in vivo. These data support the idea that pSer10p27 and CRM1 play cooperative roles in EOC.

Loss of nuclear p27(kip1) and α-dystroglycan is a frequent event and is a strong predictor of poor outcome in renal cell carcinoma

Expression levels of p27(kip1) , a negative regulator of the G1 phase of the cell cycle, and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, were assessed by immunostaining in a series of renal cell carcinomas (RCCs) and their prognostic significance was evaluated. Expression of p27(kip1) as well as of the α-subunit of the dystroglycan (DG) complex, previously reported to be altered in RCC, was also evaluated by western blot analysis. Nuclear expression of p27(kip1) was reduced in a significant fraction of tumors and low p27(kip1) staining correlated with higher tumor grade (P < 0.01). Recurrence and death from clear cell RCCs were significantly more frequent in p27(kip1) -low expressing tumors and Kaplan-Meier curves showed a significant separation between high vs low expressor groups for both disease-free (P = 0.011) and overall (P = 0.002) survival. Low nuclear expression of p27(kip1) as well as loss of α-DG were confirmed to be independent prognostic parameters at a multivariate analysis and the simultaneous loss of both molecules defined a "high-risk" group of patients with increased risk of recurrence (RR = 28.7; P = 0.01) and death (RR = 12.9; P = 0.03). No significant correlation with clinical or pathological parameters was found for 8-OHdG staining. Western blot analyses suggested a post-translational mechanism for the loss of α-DG expression and demonstrated that cytoplasmic dislocation of the protein contributes to the loss of active nuclear p27(kip1) . Loss of nuclear p27(kip1) is a frequent event in human RCCs and is a powerful predictor of poor outcome which, in combination with low DG expression, could help to identify high-risk patients with clear cell RCC.

Subcellular localization of p27 and prostate cancer recurrence: automated digital microscopy analysis of tissue microarrays

Previous investigations have linked decreased nuclear expression of the cell cycle inhibitor p27 with poor outcome in prostate cancer. However, these reports are inconsistent regarding the magnitude of that association and its independence from other predictors. Moreover, cytoplasmic translocation of p27 has been proposed as a negative prognostic sign. Given the cost and accuracy limitations of manual scoring, particularly of tissue microarrays, we determined if laser-based fluorescence microscopy could provide automated analysis of p27 in both nuclear and cytoplasmic locations and, thus, clarify its significance as a prognostic biomarker. We constructed tissue microarrays covering 202 recurrent cases (rising prostate-specific antigen) and 202 matched controls without recurrence. Quadruplicate tumor samples encompassed 5 slides and 1616 cancer histospots. Cases and controls matched on age, Gleason grade, stage, and hospital. We immunolabeled epithelial cytoplasm with Alexafluor 647, p27 with Alexafluor 488, and nuclei with 4c6-diamidino-2-phenylindole·2HCl. Slides were scanned on an iCys laser scanning cytometer (CompuCyte Corp, Cambridge, MA). Nuclear crowding required a stereological approach--random arrays of circles (phantoms) were layered on images and the content of each phantom was analyzed in scatter plots. Both nuclear and cytoplasmic p27 were significantly lower in cases versus controls (P = .014 and P = .004, respectively). Regression models controlling for matching variables plus prostate-specific antigen showed strong linear trends for increased risk of recurrence with lower p27 in both nucleus and cytoplasm (highest versus lowest quartile; odds ratio, 0.35; P = .006). Manual scoring identified an inverse association between p27 expression and tumor grade but no independent association with recurrence. In conclusion, we developed an automated method for subcellular scoring of p27 without the need to segment individual cells. Our method identified a strong relationship, independent of tumor grade, stage, and prostate-specific antigen, between p27 expression--regardless of subcellular location--and prostate cancer recurrence. This relationship was not observed with manual scoring.

Cytoplasmic p27 expression is an independent prognostic factor in ovarian cancer

Dysregulation of the cell cycle is an important prerequisite for cancer development. p27 has an established role in cell cycle control and hence may be disrupted during carcinogenesis. The influence of p27 expression, including its subcellular location, on tumor behavior in ovarian cancer has been controversial. The purpose of this study was to evaluate the expression of p27 in a large population of patients with ovarian cancer and correlate this to clinicopathologic variables including overall survival. Using a tissue microarray of 339 primary ovarian cancers, the expression of p27 was assessed immunohistochemically. Coupled to a comprehensive database of clinicopathologic variables, its effect on these factors and survival was studied. Cytoplasmic p27 showed a progressively negative impact on overall survival (P=0.004). Tumors displaying nuclear p27 also had poorer prognosis (P=0.014). Factors shown to predict prognosis independently of each other were age, stage, and the absence of macroscopic disease after surgery. Cytoplasmic p27 expression, but not nuclear, was independently predictive of prognosis on multivariate analysis (P=0.042). Both subcellular locations of p27 expression were more frequently observed in serous compared with mucinous subtypes. Cytoplasmic p27 independently predicts poorer prognosis in ovarian carcinoma. These results seem counterintuitive, when considering the antiproliferative role of p27, but may reflect a more complex function of p27 within cell cycle regulation. These data support a novel role for p27 within the cytoplasm, possibly through effects on apoptosis, cellular motility, and drug resistance.

Differential expression of cell cycle regulators in HCV-infection and related hepatocellular carcinoma

AIM

To investigate cell cycle proteins in chronic hepatitis C virus infection in order to analyze their role in the process of hepatocyte transformation and to characterize their prognostic properties.

METHODS

Subjects of the current study included 50 cases of chronic hepatitis C (CHC) without cirrhosis, 30 cases of CHC with liver cirrhosis (LC), and 30 cases of hepatitis C-related hepatocellular carcinoma (HCC) admitted to the Department of Hepato-Gastroenterology, Theodor Bilharz Research Institute (TBRI), Giza, Egypt. Fifteen wedge liver biopsies, taken during laparoscopic cholecystectomy, were also included as normal controls. Laboratory investigations including urine and stool analysis, liver function tests and prothrombin concentration; serologic markers for viral hepatitis and ultrasonography were done for all cases of the study together with immunohistochemical analysis using primary antibodies against Cyclin D1, Cyclin E, p21, p27 and Rb/p105 proteins.

RESULTS

Normal wedge liver biopsies didn't express Cyclin E or Rb/p105 immunostaining but show positive staining for Cyclin D1, p21 and p27. Cyclin D1 expressed nuclear staining that was sequentially increased from CHC to LC (P < 0.01) to HCC (P < 0.001) cases; meanwhile, Cyclin E revealed nuclear positivity only in the case of HCCs patients that was directly correlated to Rb/p105 immuno-reactivity. The expression of p21 and p27 was significantly increased in CHC and LC cases compared to normal controls and HCCs with no significant difference between well- and poorly-differentiated tumors. p21 showed only a nuclear pattern of staining, while, p27 presented with either cytoplasmic and/or nuclear reactivity in all studied cases. Correlation analysis revealed a direct relation between Cyclin D1 and p21 in CHC cases (P < 0.001), between Cyclin D1 and Cyclin E in HCCs (P < 0.01); however, an inverse relationship was detected between Cyclin D1 and p21 or p27 (P < 0.001) and between p21 and Rb/p105 (P < 0.05) in HCCs.

CONCLUSION

Upregulation of Cyclin D1 in CHC plays a vital role in the development and differentiation of HCC; while, Cyclin E may be a useful marker formonitoring tumor behavior. p21 and p27 can be used as predictive markers for HCC. Furthermore, higher expression of Rb/p105 as well as inverse relation with p21 and histologic grades suggests its important role in hepatic carcinogenesis.

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.

TGF-beta through Smad3 signaling stimulates vascular smooth muscle cell proliferation and neointimal formation

The objective of this study was to better understand the role of transforming growth factor-beta (TGF-beta) and its primary signaling protein Smad3 in the development of intimal hyperplasia. Male Sprague-Dawley rats underwent left carotid balloon injury followed by intra-arterial infection with adenovirus-expressing Smad3 (AdSmad3). In uninfected injured arteries, endogenous Smad3 was upregulated with the expression peaking at 14 days. Moreover, in arteries infected with AdSmad3, we observed an enhancement of intimal hyperplasia and increased vascular smooth muscle cell (VSMC) proliferation. The novel finding, that TGF-beta/Smad3 stimulated rather than inhibited VSMC proliferation, was confirmed in cultured VSMCs infected with AdSmad3 and treated with TGF-beta. To identify the mechanism underlying TGF-beta/Smad3-mediated VSMC proliferation, we studied the cyclin-dependent kinase inhibitor p27. Although the upregulation of Smad3 in VSMCs had no significant effect on total p27 levels, Smad3 did stimulate the phosphorylation of p27 at serine-10 as well as the nuclear export of p27, events associated with cell proliferation. Furthermore, serine-10-phosphorylated p27 was also increased in AdSmad3-infected injured rat carotid arteries, demonstrating the existence of this same mechanism in vivo. In conclusion, our findings identify a novel mechanism for the effect of TGF-beta on intimal hyperplasia. In the presence of elevated levels of Smad3 that develop in response to injury, TGF-beta stimulates smooth muscle cell proliferation through a mechanism involving the phosphorylation and nuclear export of p27.

Inhibition of hepatocelluar carcinoma MAT2A and MAT2beta gene expressions by single and dual small interfering RNA

RNA interference (RNAi) has been successfully applied in suppression of hepatic cancer genes. In hepatocelluar carcinoma cell, one methionine adenosyltransferase (MAT) isozyme, MATII was found to have two catalytic subunits which were encoded by MAT2A and MAT2β respectively. During tumorigeness of hepatocelluar carcinoma, expressions of the two genes were discovered to be increased combining with a switch of MAT (form MATI to MATII), To figure out the role played by MATII in hepatic cancer, In this study, for the first time we established a dual small interfering RNA (siRNA) expression system, which could simultaneously express two different siRNA molecules specifically targeting two genes. To test the effectiveness of this system, we applied this approach to express simultaneously two different siRNA duplexes that specifically target MAT2A and MAT2β genes of hepatocelluar carcinoma respectively in HepG2 cell. Results indicated that dual siRNA could simultaneously inhibit the expression of MAT2A and MAT2β gene by 89.5% and 97.8% respectively, In addition, dual siRNA molecules were able to significantly suppress growth of hepatocelluar carcinoma cell in vitro as well as induce apoptosis which was involved in arrest cell cycle at the G1/S checkpoint and the expressions of p21, p27 and Bax.

Expression patterns of cyclins D1, E and cyclin-dependent kinase inhibitors p21waf1/cip1, p27kip1 in colorectal carcinoma: correlation with other cell cycle regulators (pRb, p53 and Ki-67 and PCNA) and clinicopathological features

Aberrations in the cell cycle regulators are common features of many tumours and several have been shown to have prognostic significant in colorectal cancer. The expression patterns of cyclins D1 and E as well as cyclin-dependent kinase (CDK) inhibitors p21waf1/cip1 and p27kip1 and their interrelationship with other cell cycle checkpoint proteins [p53, pRb, Ki-67 and proliferative cell nuclear antigen (PCNA)] were investigated in colorectal cancer in order to ascertain coregulation and influence on tumour behaviour or survival. These molecular markers were localisated immunohistochemically using the monoclonal antibodies anticyclin D1 (DCS-6), anticyclin E (13A3), anti-p21 (4D10), anti-p27 (1B4), anti-p53 (DO7), anti-Rb (AB-5), MIB1 and PC10 in colorectal cancer tissue from 97 patients. Data were analysed statistically using the spss software program. Overexpression of cyclin D1, cyclin E and p21waf1/cip1 proteins (>5% positive neoplastic cells) was observed in 5.9%, 30% and 7.2% of the cases respectively. Increased levels of cyclin D1 (p = 0.0001) and p21waf1/cip1 protein (p = 0.03) in tumours with mucous differentiation were observed. Overexpression of cyclin D1 was correlated with tumour stage (p = 0.03), the lymph node involvement (p = 0.02), as well as p21waf1/cip1 protein expression (p < 0.0001). Cyclin E was positively correlated with p21waf1/cip1 (p = 0.014), as well as with the cell proliferation as measured by PCNA-labelling index (p = 0.011) and Ki-67 score (p = 0.007). A positive relationship of p21waf1/cip1 expression with the proliferative-associated index Ki-67 was noted (p = 0.005). Downregulation of p27kip1 was observed in 47.4% of the cases and was correlated with downregulation of pRb (p = 0.002) and PCNA score (p = 0.004). The prognostic significance of cyclins D1, E and CDK inhibitors p21waf1/cip1, p27kip1 in determining the risk of recurrence and overall survival with both univariate (long-rang test) and multivariate (Cox regression) methods of analysis showed no statistically significance differences. In conclusion, these findings suggest that, the levels of the cell cycle regulators studied, do not seems to have a prognostic value, in terms of predicting the risk of early recurrence and overall survival. In addition, the interrelationships, probably means their contribution to the regulation of cell growth, through different pathways in colorectal carcinogenesis.

Overexpression of integrin beta1 inhibits proliferation of hepatocellular carcinoma cell SMMC-7721 through preventing Skp2-dependent degradation of p27 via PI3K pathway

Integrins may play important roles in many cellular events, such as cell proliferation, differentiation, and apoptosis. We showed previously that overexpression of integrin beta1 inhibits cell proliferation in SMMC-7721 cells. Here we reported that one of the cyclin-dependent kinase (CDK) inhibitors, p27(Kip1) was involved in proliferation-inhibition induced by overexpression of integrin beta1. Overexpression of integrin beta1 upregulated p27(Kip1) at the protein level, but not mRNA level. The knock-down of p27(Kip1) expression restored cell growth in integrin beta1-overexpressing cells. Cycloheximide (Chx) treatment and pulse-chase experiments revealed that overexpression of integrin beta1 prolonged the half-life of p27(Kip1) by inhibiting its degradation. Proteasome inhibitor (MG132) treatment of the cells indicated that proteasome mediated degradation of p27, and Skp2-dependent degradation might be prevented. Overexpression of integrin beta1 decreased Skp2 at mRNA level, which was regulated by cell adhesion and the subsequent adhesion-dependent signaling. Overexpression of integrin beta1 reduced cell adhesion, accordingly, inactivated the phosphoinositide 3-kinase (PI3K) signaling. PI3K inhibitor LY294002 upregulated p27(Kip1) at post-translational level and downregulate Skp2 at mRNA level, which could mimic the effects of integrin beta1 overexpression on p27(Kip1) and Skp2. Together, these results suggested that overexpression of integrin beta1 inhibited cell proliferation by preventing the Skp2-dependent degradation of p27(Kip1) via PI3K pathway.

p27kip1 deficiency impairs G2/M arrest in response to DNA damage, leading to an increase in genetic instability

p27(kip1) is a cyclin-dependent kinase inhibitor and a tumor suppressor. In some tumors, p27 suppresses tumor growth by inhibition of cell proliferation. However, this is not universally observed, implying additional mechanisms of tumor suppression by p27. p27-deficient mice are particularly susceptibility to genotoxin-induced tumors, suggesting a role for p27 in the DNA damage response. To test this hypothesis, we measured genotoxin-induced mutations and chromosome damage in p27-deficient mice. Both p27(+/-) and p27(-/-) mice displayed a higher N-ethyl-N-nitrosourea-induced mutation frequency in the colon than p27(+/+) littermates. Furthermore, cells from irradiated p27-deficient mice exhibited a higher number of chromatid breaks and showed modestly increased micronucleus formation compared to cells from wild-type littermates. To determine if this mutator phenotype was related to the cell cycle-inhibitory function of p27, we measured cell cycle arrest in response to DNA damage. Both normal and tumor cells from p27-deficient mice showed impaired G(2)/M arrest following low doses of ionizing radiation. Thus, p27 may inhibit tumor development through two mechanisms. The first is by reducing the proliferation of cells that have already sustained an oncogenic lesion. The second is by transient inhibition of cell cycle progression following genotoxic insult, thereby minimizing chromosome damage and fixation of mutations.

In vitro differentiation of HT-29 M6 mucus-secreting colon cancer cells involves a trychostatin A and p27KIP1-inducible transcriptional program of gene expression

Tumor cell dedifferentiation-such as the loss of cell-to-cell adhesion in epithelial tumors-is associated with tumor progression. To better understand the mechanisms that maintain carcinoma cells in a differentiated state, we have dissected in vitro differentiation pathways in the mucus-secretor HT-29 M6 colon cancer cell line, which spontaneously differentiates in postconfluent cultures. By lowering the extracellular calcium concentration to levels that prevent intercellular adhesion and epithelial polarization, our results reveal that differentiation is calcium-dependent and involves: (i) a process of cell cycle exit to G(0) and (ii) the induction of a transcriptional program of differentiation gene expression (i.e., mucins MUC1 and MUC5AC, and the apical membrane peptidase DPPIV). In calcium-deprived, non-differentiated postconfluent cultures, differentiation gene promoters are repressed by a trichostatin A (TSA)-sensitive mechanism, indicating that loss of gene expression by dedifferentiation is driven by histone deacetylases (HDAC). Since TSA treatment or extracellular calcium restoration allow gene promoter activation to similar levels, we suggest that induction of differentiation is one mechanism of HDAC inhibitor antitumor action. Moreover, transcriptional de-repression can also be induced in non-differentiating culture conditions by overexpressing the cyclin-dependent kinase inhibitor p27(KIP1), which is normally induced during spontaneous differentiation. Since p27(KIP1) downregulation in colon cancer is associated with poor prognosis independently of tumor cell division rates, we propose that p27 (KIP1) may prevent tumor progression by, at least in part, enhancing the expression of some differentiation genes. Therefore, the HT-29 M6 model allows the identification of some basic mechanisms of cancer cell differentiation control, so far revealing HDAC and p27(KIP1) as key regulatory factors of differentiation gene expression.

Cytoplasmic localization of p27 (cyclin-dependent kinase inhibitor 1B/KIP1) in colorectal cancer: inverse correlations with nuclear p27 loss, microsatellite instability, and CpG island methylator phenotype

Cytoplasmic mislocalization of p27 (CDKN1B/KIP1) is caused by activated AKT1 and has been associated with poor prognosis in various cancers. CIMP in colorectal cancer is characterized by extensive promoter methylation and is associated with MSI-MSI-H and BRAF mutations. We have recently shown a positive correlation between MSI/CIMP and loss of nuclear p27. However, no study has examined cytoplasmic p27 mislocalization in relation to CIMP and MSI in colorectal cancer. Using MethyLight assays, we quantified DNA methylation in 8 CIMP-specific gene promoters (CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1) in 853 colorectal cancer samples obtained from 2 large prospective cohorts. We assessed expressions of nuclear and cytoplasmic p27 and nuclear p53 by immunohistochemistry. Cytoplasmic p27 expression was inversely associated with loss of nuclear p27 (P < .0001), CIMP-high (P < .0001), MSI-H (P < .0001), and BRAF mutations (P < .0001). The inverse association of cytoplasmic p27 with CIMP-high (or MSI-H) was independent of MSI (or CIMP) status. In addition, the inverse association of cytoplasmic p27 with CIMP-high was independent of KRAS/BRAF status. BRAF and CDKN2A (p16) methylation were not correlated with cytoplasmic p27 after stratification by CIMP status. The inverse associations of cytoplasmic p27 with MSI-H and CIMP-high were much more pronounced in p53-negative than p53-positive tumors. In conclusion, cytoplasmic p27 expression is inversely associated with MSI-H and CIMP-high, particularly in p53-negative tumors, suggesting interplay of functional losses of p27 and p53 in the development of various molecular subtypes of colorectal cancer.

Reciprocal Modifications of CLIC4 in Tumor Epithelium and Stroma Mark Malignant Progression of Multiple Human Cancers

PURPOSE

CLIC4, a member of a family of intracellular chloride channels, is regulated by p53, c-Myc, and tumor necrosis factor-alpha. Regulation by factors involved in cancer pathogenesis, together with the previously shown proapoptotic activity of CLIC4, suggests that the protein may have a tumor suppressor function. To address this possibility, we characterized the expression profile, subcellular localization, and gene integrity of CLIC4 in human cancers and determined the functional consequences of CLIC4 expression in tumor epithelium and stromal cells.

EXPERIMENTAL DESIGN

CLIC4 expression profiles were analyzed by genomics, proteomics, bioinformatics, and tissue microarrays. CLIC4 expression, as a consequence of crosstalk between stroma and epithelium, was tested in vitro by coculture of breast epithelial tumor cells and normal fibroblasts, and the functional consequences of CLIC4 expression was tested in vivo in xenografts of human breast tumor cell lines reconstituted with CLIC4 or mixed with fibroblasts that overexpress CLIC4 transgenically.

RESULTS

In cDNA arrays of matched human normal and tumor tissues, CLIC4 expression was reduced in renal, ovarian, and breast cancers. However, CLIC4 protein levels were variable in tumor lysate arrays. Transcript sequences of CLIC4 from the human expressed sequence tag database and manual sequencing of cDNA from 60 human cancer cell lines (NCI60) failed to reveal deletion or mutations in the CLIC4 gene. On matched tissue arrays, CLIC4 was predominantly nuclear in normal human epithelial tissues but not cancers. With advancing malignant progression, CLIC4 staining became undetectable in tumor cells, but expression increased in stromal cells coincident with up-regulation of alpha-smooth muscle actin, suggesting that CLIC4 is up-regulated in myofibroblasts. Coculture of cancer cells and fibroblasts induced the expression of both CLIC4 and alpha-smooth muscle actin in fibroblasts adjacent to tumor nests. Introduction of CLIC4 or nuclear targeted CLIC4 via adenovirus into human breast cancer xenografts inhibited tumor growth, whereas overexpression of CLIC4 in stromal cells of xenografts enhanced tumor growth.

CONCLUSION

Loss of CLIC4 in tumor cells and gain in tumor stroma is common to many human cancers and marks malignant progression. Up-regulation of CLIC4 in tumor stroma is coincident with myofibroblast conversion, generally a poor prognostic indicator. Reactivation and restoration of CLIC4 in tumor cells or the converse in tumor stromal cells could provide a novel approach to inhibit tumor growth.

Cytoplasmic expression of p27kip1 is associated with a favourable prognosis in colorectal cancer patients

AIM: To evaluate the prognostic significance of p27^kip1 in colorectal cancer patients.

METHODS: Cytoplasmic and nuclear p27^kip1 expression was evaluated in 418 colorectal cancers using tissue microarrays. Data were associated with known patient and tumor variables and long-term patient outcomes, providing further insight into the mechanisms by which p27^kip1 may influence tumor development.

RESULTS: Nuclear and cytoplasmic p27^Kip1 expressions were detected in 59% and 19% of tumors respectively. Cytoplasmic p27^Kip1 was almost invariably associated with positive nuclear p27^Kip1 expression. Neither case correlated with known clinical or pathological variables, including tumor stage, grade or extramural vascular invasion. Furthermore, nuclear p27^kip1 expression had no impact on survival. However, we identified a significant correlation between expression of cytoplasmic p27^kip1 and longer disease-specific survival times. On multivariate analysis, TNM stage and extramural vascular invasion were highly significant independent prognostic factors, with positive cytoplasmic p27 expression showing a trend towards improved patient survival (P = 0.059).

CONCLUSION: These findings support the recent evidence that cytoplasmic p27^kip1 has a distinct and important biological role that can influence tumor outcome.

Early expression of the Helicase-Like Transcription Factor (HLTF/SMARCA3) in an experimental model of estrogen-induced renal carcinogenesis

BACKGROUND

The Helicase-Like Transcription Factor (HLTF/SMARCA3) belongs to the family of SWI/SNF proteins that use the energy of ATP hydrolysis to remodel chromatin in a variety of cellular processes. Several SWI/SNF genes are disrupted in cancer, suggesting a role of tumor suppressor. Similarly, the HLTF gene was recently found to be inactivated by hypermethylation in a number of advanced colon and gastric tumors. However, other evidences indicated a 20-fold HLTF overexpression in cell lines derived from various neoplasms (ovary, breast, cervix, kidney...).

RESULTS

In the present study, we investigated HLTF expression by immunohistochemistry in a model of kidney tumors induced by continuous administration of diethylstilbestrol to male Syrian golden hamsters. A strong labeling was already detected in small tumor buds, making HLTF an early cancer marker in this model. Although every cell stained for HLTF at this early stage, the number of HLTF-positive cells decreased to 10% with cancer progression, and these positive cells were dispersed in the tumor mass. HLTF expression was conserved in the HKT-1097 cell line established from kidney tumors, but again only 10% of positive cells were found in xenografts produced by HKT-1097 cells in nude mice.

CONCLUSION

In conclusion, our data suggest that HLTF gene activation is linked to initial steps of carcinogenesis in this model and should be investigated in early stages of other neoplasms.

Proliferation and Cdk4 expression in microsatellite unstable colon cancers with TGFBR2 mutations

Approximately 15% of human colon cancers have microsatellite instability (MSI) and carry frameshift mutations in a polyadenine tract (BAT-RII) in the type II transforming growth factor beta (TGF-beta) receptor (TGFBR2), a required component of the TGF-beta receptor. The BAT-RII mutations in MSI colon cancers make the tumors resistant to the effects of TGF-beta. In cultured epithelial cells, TGF-beta can inhibit cell proliferation and induce apoptosis, and in vitro it can regulate the expression of a variety of cyclins, cyclin-dependent kinases (cdks) and cdk inhibitors. These effects are context- and tissue type-dependent, raising questions about which of these in vitro effects of TGF-beta signaling inactivation contribute to the formation of primary colon cancer. Thus, this study sought to determine the pathogenetically relevant effects of TGFBR2 inactivation in primary MSI colon cancers with mutant BAT-RII. Colon cancers with mutant BAT-RII were found to have increased proliferation compared to cancers with wild-type BAT-RII. Assessment of cdk4, cyclin D1 and p27(kip1) expression revealed that only cdk4 expression was increased in the cancers with mutant BAT-RII. In order to determine if TGFBR2 inactivation was the cause of these changes, TGFBR2 was reconstituted in an MSI colon cancer cell line, resulting in decreased proliferation and decreased cdk4 expression and kinase activity. These results suggest that TGFBR2 mutations in primary colon cancers may be responsible for the increased proliferation and cdk4 expression in these tumors and provide evidence that deregulation of cdk4 is a pathogenic in vivo consequence of TGFBR2 inactivation in primary colon cancer.

Biological Correlates of p27 Compartmental Expression in Prostate Cancer

PURPOSE

As one of the cyclin-dependent kinase inhibitors, p27 has been associated with biological behavior and disease progression in malignancies.

MATERIALS AND METHODS

Tissue microarrays were constructed using 640 radical prostatectomy specimens. Normal prostate tissue, benign prostatic hyperplasia and index tumor were cored in triplicate at 0.6 mm. Slides were stained with an antibody to p27 and digitized. The expression of p27 was quantified. SPSS 11.0 (SPSS, Chicago, Illinois) was used to perform the Spearman correlation test, Kaplan-Meier analysis and Cox proportional hazard regression.

RESULTS

We noted p27 expression predominately located in the epithelial nuclei of benign and cancer tissues. In PCa p27 was decreased compared to that in normal tissue, while p27 cytoplasmic expression was increased in PCa. Moderate nuclear p27 and cytoplasmic displacement of p27 were associated with worse disease-free survival compared with high or low p27. The cytoplasmic presence of p27 was an independent indicator for predicting the probability of biochemical recurrence in PCa.

CONCLUSIONS

We report that p27 expression is consistently high in the normal prostate. Moderate levels of nuclear p27 and/or cytoplasmic entrapment of p27 are associated with increased proliferation and worse biochemical recurrence-free survival. These findings suggest that PCa may enhance its growth and progression by decreasing nuclear p27 via cytoplasmic displacement and other molecular mechanisms.

Cyclin-dependant kinase inhibitors CIP1 (p21) and KIP1 (p27) in ovarian cancer

PURPOSE

Deregulation of the cell cycle is one of the important prerequisites for cancer development. p21 and p27 are both universal inhibitors of cyclin-dependent kinases and can therefore influence cell cycle or tumor progression. The aim of this study was to determine the influence of p21 and p27 expression on survival and chemotherapy response.

METHODS

165 patients with ovarian cancer have been examined for p21 and p27 expression by immunohistochemistry on formalin-fixed, paraffin-embedded tissue using the monoclonal primary antibody WAF1 (Oncogene Science) and KIP1 (Transduction Laboratories).

RESULTS

High p21 expression (>50%) correlates only with early tumor stage (P=0.04). There was no correlation found between p21 and p27 expression. Patients with high p27 expression (>25%) had a longer DFS (disease free survival) in both univariate and multivariate analysis (P=0.05 and P=0.043) than patients with low p27 expression. A longer overall survival (OS) could only be proven for the group of high p27 expression in univariate analysis (P=0.03).

CONCLUSION

p27 is an independent prognostic factor for ovarian cancer for DFS though this was not true for OS.

The MLL fusion gene, MLL-AF4, regulates cyclin-dependent kinase inhibitor CDKN1B (p27kip1) expression

MLL, involved in many chromosomal translocations associated with acute myeloid and lymphoid leukemia, has >50 known partner genes with which it is able to form in-frame fusions. Characterizing important downstream target genes of MLL and of MLL fusion proteins may provide rational therapeutic strategies for the treatment of MLL-associated leukemia. We explored downstream target genes of the most prevalent MLL fusion protein, MLL-AF4. To this end, we developed inducible MLL-AF4 fusion cell lines in different backgrounds. Overexpression of MLL-AF4 does not lead to increased proliferation in either cell line, but rather, cell growth was slowed compared with similar cell lines inducibly expressing truncated MLL. We found that in the MLL-AF4-induced cell lines, the expression of the cyclin-dependent kinase inhibitor gene CDKN1B was dramatically changed at both the RNA and protein (p27kip1) levels. In contrast, the expression levels of CDKN1A (p21) and CDKN2A (p16) were unchanged. To explore whether CDKN1B might be a direct target of MLL and of MLL-AF4, we used chromatin immunoprecipitation (ChIP) assays and luciferase reporter gene assays. MLL-AF4 binds to the CDKN1B promoter in vivo and regulates CDKN1B promoter activity. Further, we confirmed CDKN1B promoter binding by ChIP in MLL-AF4 as well as in MLL-AF9 leukemia cell lines. Our results suggest that CDKN1B is a downstream target of MLL and of MLL-AF4, and that, depending on the background cell type, MLL-AF4 inhibits or activates CDKN1B expression. This finding may have implications in terms of leukemia stem cell resistance to chemotherapy in MLL-AF4 leukemias.

The clinical significance of p53, p21, and p27 expressions in rectal carcinoma

Many checkpoint proteins that are involved in the control of the cell cycle and apoptosis have been investigated, but only a few studies have evaluated the prognostic significance of multiple factors only in rectal carcinomas. The aim of this study was to determine the role of p53, p21, and p27 protein expression as a prognostic factor in rectal carcinomas. Formalin-fixed, paraffin-embedded tissue blocks from 45 rectal adenocarcinomas with appropriate clinical and prognostic data were examined. The standard streptavidin-biotin immunoperoxidase method was used for immunostaining with p53 protein, p21 WAF1/Cip1 protein, and p27 Kip1 protein. The extent of positive p53, p21, and p27 staining was graded semiquantitatively. The clinicopathologic and prognostic features were statistically analyzed. No significant association was found between p53 status and p21 or p27 protein expression (chi2 test, P=0.42 and P=0.18 respectively). There was no correlation between the expressions of p53, p21, and p27, and conventional clinicopathologic features. The mean time interval to recurrence was 25.7+/-24.7 months (range, 0-54 months). p53, p21, and p27 expression was not associated significantly with recurrence and distant metastasis. However, a significant relationship was found between the expression of p27 protein and hepatic metastasis (independent samples t-test, P=0.007). The authors concluded that p53, p27, and p21 protein expression was not related to the clinicopathologic parameters, tumor aggressiveness, metastatic potential, and survival in rectal carcinomas. Further studies are needed to evaluate the predictors of outcome in rectal cancer, considering a variety of prognosticators.

Prognostic significance of DCC and p27Kip1 in colorectal cancer

The progression of colorectal cancer is a multistage process associated with specific molecular alterations. The stepwise accumulation of these multiple genetic mutations progressively results in the acquisition of neoplastic cell behavior. The genetic abnormalities associated with the expression of metastatic phenotype, therefore, may be of prognostic significance in the clinical treatment of colorectal cancer patients. In this study, the immunohistochemical expression of the deleted in colorectal cancer gene (DCC) and p27Kip1 was assessed in 168 paraffin-embedded, formalin-fixed tumors of patients with stage II and III colorectal cancer. Kaplan-Meier survival curves and log-rank statistics were used to analyze survival times after curative primary tumor resection, and Cox proportional hazards models were used to adjust the assessment of demographic and clinical covariates. Loss of DCC or p27Kip1 expression had no influence on survival in patients with stage II or III colorectal cancer. The 5-year survival rates of DCC-positive and DCC-negative tumors were 51.8% and 35.7% (P=0.40), respectively. The 5-year survival rate of patients with p27Kip1-positive tumors was 47.9%, whereas the rate for patients with p27Kip1-negative tumors was 38.8% (P=0.68). After adjustment for all evaluated variables, neither DCC or p27Kip1 was found to be a predictor of survival (risk ratio for DCC, 0.98; 95% confidence interval, 0.66-1.56; P=0.92; risk ratio for p27Kip1, 0.87; 95% confidence interval, 0.58-1.29; P=0.49). The present study demonstrated that the expression of neither DCC nor p27Kip1 was predictive in poor survival outcome in patients with stage II or III colorectal cancer.

Altered expression of cyclins and cell cycle inhibitors in papillary thyroid cancer: prognostic implications

Currently we lack biochemical or molecular markers that predict recurrence and metastases in thyroid cancer. Recent studies in a number of other human malignancies indicate that expression and/or subcellular localization of certain cell cycle regulators has prognostic utility. We have investigated the expression of cyclins D1 and E and of cyclin-dependent kinase inhibitor's p21 and p27 in papillary thyroid cancer (PTC) and correlated this with clinical/histological stage at diagnosis and with clinical outcome. PTCs were compared to normal thyroid, adenomas, and undifferentiated thyroid cancers (UTCs). Our studies indicate that PTCs and UTCs demonstrate low nuclear expression of cyclin E and p27, allowing a clear distinction between adenomas and these carcinomas (p < 0.004). A pattern of low nuclear expression of all four markers was observed in stage IV PTCs and UTCs, while stage I PTCs had low D1 and E accompanied by high p21 or p27. Expression of cytoplasmic cyclin D1 was significantly lower in stage IV PTCs and UTCs than in stage I-III PTC's (p </= 0.020), and appeared to correlate inversely with poor outcome in PTCs (p = 0.010). These studies suggest that evaluation of a panel of these markers and attention to their subcellular localization may be a useful adjunct in differentiating benign from malignant thyroid neoplasms and in predicting tumor behavior.

Cell proliferation, apoptosis and the related regulators p27, p53 expression in hepatocellular carcinoma

AIM: To investigate the expression of cell apoptosis, proliferation and the related regulators p27, p53 in hepatocellular carcinoma (HCC).

METHODS: The expression of p27, p53, proliferating cell nuclear antigen (PCNA) and apoptosis in 47 HCC specimens and 42 surrounding non-cancerous tissues were detected by the immunohistochemistry and terminal deoxy-nucleotidyl transferase-mediated nick end labeling (TUNEL) technique. Meanwhile, the clinical significance of them was analyzed combining with the clinicopathological factors and follow-up data.

RESULTS: (1) The average proliferating index and apoptotic index in HCC were significantly higher than that in adjacent liver tissues. The proliferating index was associated with extrahepatic metastasis. The apoptotic index was significantly lower in TNM stage I-II than in stage III-IV. The proliferating index of groups with p53-/p27+ was significantly lower than that in group with p53+/p27- (P = 0.030); (2) The level of p27 in the cytoplasmic fraction was higher in non-tumoral liver tissues and was associated with clinical stage; (3) Survival analysis showed advanced stage (P = 0.031) and with extrahepatic metastasis (P = 0.045) was significantly associated with shorter survival. In addition, the prognosis of patients with p53-/p27+ was longer than that of patients with p53+/p27- (P = 0.0356).

CONCLUSION: The p53 mutation and decreased p27 expression might be involved in the imbalance of proliferation and apoptosis in HCC. Cytoplasmic displacement might lead to the inactivation of p27 protein in HCC cells and acts early during carcinogenesis of HCC. The combined examination of p27, and p53 expression allows reliable estimation of prognosis for patients with primary hepatic carcinoma.

The Tumor-specific Hyperactive Forms of Cyclin E Are Resistant to Inhibition by p21 and p27

The low molecular weight (LMW) isoforms of cyclin E are unique to cancer cells. In breast cancer, such alteration of cyclin E is a very strong predictor of poor patient outcome. Here we show that alteration in binding properties of these LMW isoforms to CDK2 and the CDK inhibitors (CKIs), p21 and p27, results in their functional hyperactivity. The LMW forms of cyclin E are severalfold more effective at binding to CDK2. Additionally, compared with the full-length cyclin E-CDK2 complexes, the LMW cyclin E-CDK2 complexes are significantly more resistant to inhibition by p21 and p27, despite equal binding of the CKIs to the LMW complexes. When both the full-length and the LMW cyclin E are co-expressed, p27 preferentially binds to the LMW forms yet is unable to inhibit the CDK2 activity. Thus, the LMW forms of cyclin E may contribute to tumorigenesis through their resistance to the inhibitory activities of p21 and p27 while sequestering these CKIs from the full-length cyclin E.

IFN-γ/IRF-1-induced p27kip1down-regulates telomerase activity and human telomerase reverse transcriptase expression in human cervical cancer

Telomerase activation is regulated by the expression of human telomerase reverse transcriptase (hTERT) and is a key step in the development of human cancers. Interferon-gamma (IFN-gamma) signaling induces growth arrest in many tumors through multiple regulatory mechanisms. The p27 tumor suppressor protein inhibits the formation of tumors through the induction of cell cycle arrest and/or apoptosis. We demonstrate here that p27Kip1 inhibits hTERT mRNA expression and telomerase activity through post-transcriptional up-regulation by IFN-gamma/IRF-1 signaling. The ectopic expression of p27 suppressed hTERT expression and telomerase activity in human cervical cancer cell lines, HeLa and HT3. Furthermore, hTERT promoter activity of mouse embryonic fibroblasts (MEFs) deficient in p27 (p27-/- MEFs) was significantly higher than that of wild-type MEFs. Overexpression of p27 suppressed hTERT promoter activity and telomerase activity of p27-/- MEFs. In addition p27 down-regulated E7 protein expression and in transiently transfected HeLa cells, E7 increased hTERT promoter activity. In conclusion, we propose that inhibition of the hTERT expression and telomerase activity may be a novel tumor suppressor function of p27.

Prognostic significance of p27(kip-1) expression in colorectal adenocarcinomas is associated with tumor stage

PURPOSE

Although the decreased expression of p27(kip-1), a cyclin-dependent kinase inhibitor, has been correlated with advanced tumor stage and short survival of patients with colorectal adenocarcinomas (CRCs), its prognostic value based on the tumor site, tumor stage, and patient ethnicity was not assessed. Therefore, in this study, we investigated whether the prognostic value of p27(kip-1) expression varies with the tumor site, tumor stage and patient ethnicity.

EXPERIMENTAL DESIGN

We evaluated 206 (85 African Americans and 121 Caucasians) archival tissue specimens of first primary CRCs for immunohistochemical expression of p27(kip-1), and its prognostic significance was analyzed using univariate Kaplan-Meier and multivariate Cox regression survival methods.

RESULTS

Although, similar proportion of CRCs with decreased p27(kip-1) expression was observed in all stages (range, 26-36%), the decreased p27(kip-1) expression has been shown as a marker of poor prognosis only for patients with stage III tumors both in univariate (log-rank test, P = 0.014) and multivariate (hazard ratio = 3.2, 95% confidence interval = 1.3-7.7; P = 0.01) survival analyses. The decreased expression of p27(kip-1) was associated with a high histologic grade (P = 0.016) in stage II CRCs, and with distal tumors (P = 0.001), tumor invasion (P = 0.044), and with local recurrence (P = 0.008) in stage III CRCs.

CONCLUSIONS

No prognostic significance was found for p27(kip-1) expression in stages I, II, or IV CRCs, and its prognostic value was not associated with either ethnicity or tumor location. These studies suggest that decreased expression of p27(kip-1) is an indicator of poor prognosis and aids in identifying a subset of patients with aggressive forms of stage III CRCs.

Immunohistochemical expression of cyclin D1, cyclin E, p21/waf1 and p27/kip1 in inflammatory bowel disease: correlation with other cell-cycle-related proteins (Rb, p53, ki-67 and PCNA) and clinicopathological features

BACKGROUND AND AIMS

The expression patterns of cyclins D1 and E as well as cyclin-dependent kinase inhibitors p21/waf1 and p27/kip1 and their correlation with clinical parameters and other cell cycle regulators was investigated in inflammatory bowel disease (IBD).

PATIENTS AND METHODS

These molecular markers were localized immunohistochemically using the monoclonal antibodies anti-cyclin D1 (DCS-6), anti-cyclin E (13A3), anti-p21 (4D10) and anti-p27 (1B4) in 70 patients with IBD, 30 patients with colorectal cancer and eight healthy subjects. Data were analyzed statistically using the software program.

RESULTS

Cyclin D1 expression was higher in both UC and CD compared with the healthy control group. In addition, CD cyclin D1 expression was higher compared with UC cases and colorectal carcinomas. Cyclin D1 expression was correlated with disease activity and cell proliferation in UC cases. A positive relationship of cyclin D1 with p27/kip1 in both UC and CD was detected. Cyclin E expression was higher in UC, CD and carcinomas compared with healthy control group and its expression correlated with proliferative activity in both UC and CD cases. p21/waf1 expression was higher in IBD cases compared with that of the control group, while a decreased p21/waf1 expression in the group of carcinomas was noted. This expression was correlated with disease activity in UC and the proliferative activity in both UC and CD. The expression of cyclins D1 and E as well as p21/waf1 was also correlated with the existence of dysplastic lesions. A lower p27/kip1 expression in the group of carcinomas compared with IBD cases and healthy controls was found.

CONCLUSIONS

The expression patterns of cyclin D1, cyclin E, p21/waf1 and p27/kip1 in IBD may indicate their contribution in epithelial cell turnover and their possible implication in IBD-related dysplasia-carcinoma.

Mice deficient for the gap junction protein Connexin32 exhibit increased radiation-induced tumorigenesis associated with elevated mitogen-activated protein kinase (p44/Erk1, p42/Erk2) activation

Loss of connexin expression/gap junction intercellular communication (GJIC) has been correlated with decreased growth control and increased tumorigenesis. Studies utilizing Connexin32 (Cx32)-deficient knockout mice have demonstrated that loss of Cx32 increases susceptibility to chemically induced liver tumorigenesis. Here, in addition to dramatically increased liver tumorigenesis, we show that tumor induction utilizing X-ray radiation resulted in a statistically significant increase in overall tumor burden in Cx32-deficient mice compared with wild-type mice due to tumorigenesis in several other tissues (lung, adrenal, lymph and small intestine) even when excluding prevalent liver tumors. Irradiated Cx32-deficient mice were particularly sensitive to liver tumorigenesis (46% incidence compared with 18% in wild-type mice, P = 0.007) demonstrating that Cx32 functions as a hepatic tumor suppressor in response to radiation-associated mutation events. Cx32-deficient mice also exhibited increased lung tumorigenesis (bronchioloalveolar) with an increased progression to carcinoma when compared with wild-type mice. Two Cx32-deficient mice developed an uncommon, invasive medullary adrenal tumor type (pheochromocytoma) not observed in irradiated wild-type mice. Immunohistochemical analysis revealed increased levels of activated mitogen-activated protein kinase (MAPK) (p44/Erk1, p42/Erk2) in Cx32-deficient mouse liver tumors (P = 0.006), lung tumors (P = 0.056) and adrenal tumors (primary and metastases) compared with wild-type counterparts implicating elevated activation of MAPK-interacting pathways in Cx32-deficient tumorigenesis. Interestingly, lung tumors from Cx32-deficient mice also demonstrated decreased p27Kip1 levels compared with wild-type lung tumors (P = 0.05). This study demonstrates that loss of Cx32/GJIC plays a significant role in radiation-induced tumorigenesis of the liver and importantly that Cx32 may also play a role in tumor suppression and/or tumor progression in other tissue types such as lung and adrenal gland. Additionally, this mouse model suggests that MAPK-related pathways may be preferentially activated or conversely that tumors harboring activated MAPK pathways may selectively progress towards more advanced tumor states in the absence of Cx32-mediated GJIC.

Microenvironmental regulation of proliferation in multicellular spheroids is mediated through differential expression of cyclin-dependent kinase inhibitors

Multicellular spheroids composed of transformed cells are known to mimic the growth characteristics of tumors and to develop gradients in proliferation with increasing size. This progressive accumulation of quiescent cells is presumably an active process that occurs in response to the microenvironmental stresses that develop within the three-dimensional structure, and, yet, little is known regarding either the signals that induce the cell cycle arrest or the molecular basis for the halt in proliferation. We have previously reported that regulation of cyclin-dependent kinase (CDK) inhibitors (CKIs) differs in monolayer versus spheroid cell culture. In this study, we have examined the expression of three CKIs in EMT6 mouse mammary carcinoma and MEL28 human melanoma spheroids, as a function both of spheroid size and of location within the spheroid. We report that expression of the CKIs p18(INK4c), p21(waf1/cip1), and p27(Kip1) all increase as the spheroid grows and develops a quiescent cell fraction. However, by examining protein expression in discrete regions of the spheroid, we have found that only p18(INK4c) and p27(Kip1) expression positively correlate with growth arrest, whereas p21(waf1/cip1) is expressed predominantly in proliferating cells. Further analysis indicated that, in the quiescent cells, p18(INK4c) is found in increasing association with CDK6, whereas p27(Kip1) associates predominantly with CDK2. In MEL28 cells, CDK2 activity is completely abrogated in the inner regions of the spheroid, whereas in EMT6 cells, CDK2 activity decreases in accordance with a decrease in expression. We also observed a decrease in all cell cycle regulatory proteins in the innermost spheroid fraction, including CDKs, CKIs, and cyclins. Induction of CKIs from separate families, as well as their association with distinct target CDKs, suggests that there may be multiple checkpoints activated to ensure cell cycle arrest in non-growth-conducive environments. Furthermore, because very similar observations were made in both a human melanoma cell line and a mouse mammary carcinoma cell line, our results indicate that these checkpoints, as well as the signal transduction pathways that activate them, are highly conserved.

Targeted inhibition of the epidermal growth factor receptor-tyrosine kinase by ZD1839 (?Iressa?) induces cell-cycle arrest and inhibits proliferation in prostate cancer cells

The epidermal growth factor (EGF) plays a role in the development of prostate cancer, which becomes essential after androgen resistance has emerged. The EGF receptor (EGFR) is therefore a potential target for anticancer therapy. We evaluated the effects of ZD1839 ('Iressa'), an orally active EGFR-tyrosine kinase inhibitor, on prostate cancer cell lines. The effects of ZD1839 were evaluated on the anchorage dependent and independent growth of androgen-responsive (LNCaP) and androgen-independent (DU145 and PC3) cells by a cell proliferation assay, cell counting, and soft agar analysis. Flow cytometric analysis and Western blotting were used to assess the effects on the cell-cycle and on protein expression levels, respectively. ZD1839 caused a dose- and time-dependent growth inhibition in all three cell lines. A dose-dependent supra-additive increase in growth inhibition was observed when ZD1839 was combined with the antiandrogen flutamide or ionizing radiation (IR). The antiproliferative effect of ZD1839 was mainly cytostatic and associated with a block in the G(0)/G(1) phase of the cell-cycle, evident after about 12 h of treatment. In the DU145 cells this block was associated with an increase in expression of the CDK inhibitor p27(Kip1), both in the cytoplasmic and nuclear fractions. The increase in p27(Kip1) was not evident in the LNCaP and PC3 cells. No changes were observed in the expression of cyclin D1 protein. These results demonstrate the antiproliferative effects of ZD1839 on the growth of prostate cancer cells and suggest that inhibition of EGFR-associated signal transduction pathway might represent a promising novel therapeutic strategy for the treatment of prostate cancer.

Pleomorphic carcinomas of the lung show a selective distribution of gene products involved in cell differentiation, cell cycle control, tumor growth, and tumor cell motility: a clinicopathologic and immunohistochemical study of 31 cases

We investigated 31 cases of pleomorphic carcinomas of the lung, with a double component of neoplastic epithelial cells and of spindle and/or giant cells. To correlate the morphologic diversity of these two cell components with their immunophenotype, we evaluated the expression of several gene products involved in cell differentiation (cytokeratins, epithelial membrane antigen, carcinoembryonic antigen, vimentin, S-100 protein, smooth muscle actin, desmin), cell cycle control and apoptosis (p53, p21Waf1, p27Kip1, FHIT), tumor growth (proliferative fraction, assessed by Ki-67 antigen, and microvascular density, assessed by CD34 immunostaining), and tumor cell motility (fascin). We found the epithelial component to be significantly more immunoreactive for cytokeratins, epithelial membrane antigen, carcinoembryonic antigen, cell cycle inhibitors p21Waf1, p27Kip1 and tumor suppressor gene FHIT, whereas the sarcomatoid component, independent of tumor stage and size, was more immunoreactive for vimentin, fascin, and microvascular density. Accordingly, we suggest a model of tumorigenesis whereby the mesenchymal phenotype of pleomorphic cells is likely induced by the selective activation and segregation of several molecules involved in cell differentiation, cell cycle control, and tumor cell growth and motility. Whether pleomorphic carcinomas of the lung are tumors with a dismal prognosis still remains an unsettled issue. In our series, however, stage I pleomorphic carcinomas have the same clinical behavior as ordinary non-small cell lung cancer, and only a high proliferative index (Ki-67 labeling index >35%) is associated with a worse prognosis in these tumors.

Poor prognosis of colorectal cancer in patients over 80 years old is associated with down-regulation of tumor suppressor genes

GOALS, BACKGROUND: The elderly population has been increasing during the last half a century and it would be important to know how aging influences the occurrence and biologic behavior of cancers.

STUDY

We investigated clinicopathologic characteristics of colorectal cancer in 1354 patients who underwent colorectal cancer resection and compared the results between extremely elderly patients (over 80 years old) and middle-aged/elderly patients (40 to less than 80 years old). Furthermore, we also examined expression of tumor suppressor genes and Cox-2 using frozen samples of colorectal cancer obtained from 62 patients ranging in age from 45 to 87 years.

RESULTS

The results obtained in the extremely aged patients were: (1) higher ratio of women, (2) higher incidence at the proximal site, (3) higher incidence of cases with deeper invasion, (4) higher incidence of cases with lymph node metastasis (5) poorer survival rate as compared with middle-aged/elderly patients, and (6) lower mRNA expression levels of p27 and p53.

CONCLUSIONS

These findings taken together suggest that poor prognosis of colorectal cancer in patients over 80 years is associated with down-regulation of mRNA expression of some tumor suppressor genes.

p27 Protein and cancers of the gastrointestinal tract and liver: an overview

GOALS

The purpose of this review is to look at the evidence presented in the literature on the immunoexpression of p27 in cancers of the gastrointestinal tract and liver.

BACKGROUND

Cell cycle proteins have been shown to play an important role in the oncogenesis of many tumors. Several of these proteins have been examined in concert and in isolation, and some have been put forward as putative tumor markers. p27, which is an important inhibitory protein in the cell cycle and belonging to a group of cyclin-dependent kinase inhibitors, has also been studied in several malignancies, most notably breast, lung, bladder, and prostate cancers. Considerable work has also been done on the expression of this protein in cancers occurring within the gastrointestinal tract.

RESULTS

Cancers occurring in the major sites of the gastrointestinal tract (esophagus, stomach, and colorectum) and liver show a similar pattern with regard to p27 protein levels. p27 emerges as a statistically significant predictor of survival and tumor behavior. It has been suggested that p27 loss occurs early in the carcinogenesis process, with dysplastic epithelium having decreased expression. The more aggressive, metastasizing cancers tend to lack p27 expression as well. Some studies have also invoked the subcellular localization of p27 (cytoplasmic versus nuclear) as also being of prognostic value.

CONCLUSION

Therefore, in gastrointestinal and hepatic cancers, low p27 expression is regarded as an important adverse prognostic factor.

p27(Kip1) (Cdkn1b)-deficient mice are susceptible to chemical carcinogenesis and may be a useful model for carcinogen screening

The two-year rodent bioassay is one of several tests that are widely used by governmental regulatory agencies as well as pharmaceutical and chemical companies to determine the carcinogenic potential of chemicals or environmental agents where human exposure is anticipated. That this assay has remained relatively unchanged for the last 25 years is a testament to the power of this approach to identify carcinogens and thus to minimize human exposure. However, there has long been controversy over the specificity and relevance of the rodent bioassay as well as its high cost in terms of time, expense, and numbers of mice. Much discussion has been generated in recent years over how to improve the 2-year rodent bioassay for more accurate and faster detection of potential human carcinogens. Here, we argue that the use of p27(Kip1) (Cdkn1b) knockout mouse for carcinogen screening may solve several shortcomings inherent in the conventional bioassay while preserving its best quality, that is, protecting public health by providing reliable in vivo information on the potential of chemicals to cause cancer.

Growth regulation by p27Kip1 is abrogated by multiple mechanisms in aggressive malignant lymphomas

The cyclin-dependent kinase inhibitor p27Kip1 is a key regulator of the G1/S transition, and an inverse relationship between p27Kip1 protein expression and proliferation index has been reported in malignant lymphomas. However, a subset of aggressive B-cell lymphomas demonstrates high p27Kip1 expression despite a high proliferation index. The aim of this study was to determine potential mechanisms by which lymphoma cells abrogate the growth inhibitory effect of high p27Kip1. The effect of transforming growth factor-beta (TGF-beta) and serum stimulation on p27Kip1 expression and cyclin E/cdk2 activity was investigated in four lymphoma cell lines, Jurkat, CEM-6, OCI-Ly1 and Nalm-6. Reactive lymphocytes responded to growth inhibitory TGF-beta by inducing p27Kip1 expression, with subsequent accumulation of cells in G0/G1. In contrast, TGF-beta did not alter the level of p27Kip1 in Jurkat, CEM-6 and OCI-Ly1 cells with no change in cyclin E/cdk2-kinase activity. Serum stimulation also did not result in a significant change in p27Kip1 expression. Western blot analysis of subcellular fractions demonstrated cytoplasmic p27Kip1, corroborated by immunocytochemistry in a subset of the lymphoma cells. Sequestration of p27Kip1 by cyclin D3 was observed in the nuclear and cytoplasmic fractions of Nalm-6, OCI-Ly-1 and NCEB cells. These results indicate that multiple mechanisms contribute to the abrogation of growth regulation by unscheduled high p27Kip1 protein expression including deficient response to TGF-beta and serum, sequestration by cyclin D3 and cytoplasmic displacement.

Dystroglycan expression is frequently reduced in human breast and colon cancers and is associated with tumor progression

Dystroglycan (DG) is an adhesion molecule responsible for crucial interactions between extracellular matrix and cytoplasmic compartment. It is formed by two subunits, alpha-DG (extracellular) and beta-DG (transmembrane), that bind to laminin in the matrix and dystrophin in the cytoskeleton, respectively. In this study we evaluated by Western blot analysis the expression of DG in a series of human cancer cell lines of various histogenetic origin and in a series of human primary colon and breast cancers. Decreased expression of DG was observed in most of the cell lines and in both types of tumors and correlated with higher tumor grade and stage. Analysis of the mRNA levels suggested that expression of DG protein is likely regulated at a posttranscriptional level. Evaluation of alpha-DG expression by immunostaining in a series of archival cases of primary breast carcinomas confirmed that alpha-DG expression is lost in a significant fraction of tumors (66%). Loss of DG staining correlated with higher tumor stage (P = 0.022), positivity for p53 (P = 0.033), and high proliferation index (P = 0.045). A significant correlation was also observed between loss of alpha-DG and overall survival (P = 0.013 by log-rank test) in an univariate analysis. These data indicate that DG expression is frequently lost in human malignancies and suggest that this glycoprotein might play an important role in human tumor development and progression.

Expression of p27 and VHL in renal tumors

Renal tumors, in particular clear cell renal cell carcinomas, have an unclear prognosis and metastatic potential. Cell cycle regulators play a key role in cellular proliferation and have been implicated in neoplasia. The cell cycle inhibitor p27 has been associated with prognosis in various tumor types. Recently a reported association between p27 and Von Hippel-Lindau (VHL) gene function has also been noted. We have examined p27 and VHL expression by immunohistochemistry in a panel of kidney tumors and have noted specific and unique patterns of p27 expression in various tumor types. In addition, we have analyzed p27 expression in clear cell type renal cell carcinomas and have noted a significant association between decreasing p27 expression and increasing tumor size, suggesting a relation between renal cell proliferation and loss of p27 function. These findings suggest a role for p27 in the development of various types of renal tumors.

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.

Expression of Skp2, a p27(Kip1) ubiquitin ligase, in malignant lymphoma: correlation with p27(Kip1) and proliferation index

Reduced levels of p27(Kip1) are frequent in human cancers and have been associated with poor prognosis. Skp2, a component of the Skp1-Cul1-F-box protein (SCF) ubiquitin ligase complex, has been implicated in p27(Kip1) degradation. Increased Skp2 levels are seen in some solid tumors and are associated with reduced p27(Kip1). We examined the expression of these proteins using single and double immunolabeling in a large series of lymphomas to determine if alterations in their relative levels are associated with changes in cell proliferation and lymphoma subgroups. We studied the expression of Skp2 in low-grade and aggressive B-cell lymphomas (n = 86) and compared them with p27(Kip1) and the proliferation index (PI). Fifteen hematopoietic cell lines and peripheral blood lymphocytes were studied by Western blot analysis. In reactive tonsils, Skp2 expression was limited to proliferating germinal center and interfollicular cells. Skp2 expression in small lymphocytic lymphomas (SLLs) and follicular lymphomas (FCLs) was low (mean percentage of positive tumor cells, less than 20%) and was inversely correlated (r = -0.67; P <.0001) with p27(Kip1) and positively correlated with the PI (r = 0.82; P <.005). By contrast, whereas most mantle cell lymphomas (MCLs) demonstrated low expression of p27(Kip1) and Skp2, a subset (n = 6) expressed high Skp2 (exceeding 20%) with a high PI (exceeding 50%). Skp2 expression was highest in diffuse large B-cell lymphomas (DLBCLs) (mean, 22%) and correlated with Ki-67 (r = 0.55; P <.005) but not with p27(Kip1). Cytoplasmic Skp2 was seen in a subset of aggressive lymphomas. Our data provide evidence for p27(Kip1) degradative function of Skp2 in low-grade lymphomas. The absence of this relationship in aggressive lymphomas suggests that other factors contribute to deregulation of p27(Kip1) expression in these tumors.

Ketoconazole potentiates the antitumor effects of nocodazole: In vivo therapy for human tumor xenografts in nude mice

Our previous studies demonstrated that the oral antifungal agent ketoconazole (KT) induces apoptosis and G0/G1 phase cell cycle arrest in human cancer cell lines. In this study, we first demonstrated that KT (1 microM) potentiated the apoptotic effects of nocodazole (ND, 1 nM) in COLO 205 cancer cells. We further demonstrated the therapeutic efficacy of a combined treatment of KT (50 mg/kg/three times per week) and ND (5 mg/kg/three times per week) in vivo by treating athymic mice bearing COLO 205 tumor xenografts. The antitumor effects of ND were significantly potentiated by KT in mice after 6 wk of treatment. No gross signs of toxicity were observed in mice receiving these treatment regimens. The apoptotic cells were detected in a microscopic view of the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining and by observation of DNA fragmentation in KT + ND-treated tumor tissues. The levels of cell cycle regulatory proteins were determined by Western blot analysis. Treatment with KT inhibits tumor growth through elevation of p53, p21/CIP1, and p27/KIP1 as well as inhibition of cyclin D3 and cyclin-dependent kinase 4 protein expression. Immunohistochemical staining analysis showed that p53, p21/CIP1, and p27/KIP1 immunoreactivity were induced in the tumor tissues. To clarify the roles of the p21/CIP1 and p27/KIP1 protein expression involved in G(0)/G(1) arrest and/or apoptosis induced by a combined treatment with KT and ND, antisense oligodeoxynucleotides (ODNs) specific to p21/CIP1 and p27/KIP1 were used. Our results demonstrated that apoptotic phenomena, including BAX induction and cytochrome C released from mitochondria induced by KT + ND, were significantly attenuated by pretreatment the cells with the p27/KIP1-specific antisense ODNs. These results indicate that p27/KIP1 protein does indeed play a critical role in the KT + ND-induced apoptosis. Our study revealed the molecular mechanism of KT + ND in regression of the tumor growth. The apoptotic effects of KT in a great variety of cancer cells make it a very attractive agent for cancer chemotherapy.

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.

Molecular markers in prognosis of colorectal cancer and prediction of response to treatment

Colorectal cancer is the third most common human malignancy. Direct observation and biopsy sampling by colonoscopy have provided unique opportunities to study the natural history of the disease. As a consequence, advances in the understanding of colorectal cancer pathogenesis have evolved more rapidly than with most other solid tumours. Numerous molecular events arising during the development of colorectal cancer have been sorted out over the past two decades. Despite these advances, predicting outcome and response to therapy is still a major challenge in the management of patients with colorectal cancer. Molecular and biochemical markers of colorectal cancer are greatly needed for diagnosis and prognosis as well as for the selection and monitoring of treatments. The purpose of this chapter is to provide a critical assessment of the usefulness of markers in the prognosis and prediction of response to treatment in colorectal cancer.

Pulmonary Epithelial-Myoepithelial Tumor of Unproven Malignant Potential: Report of a Case and Review of the Literature

Epithelial-myoepithelial tumors of the lung are rare neoplasms whose biological behavior and clinical course still remain to be defined. A case of epithelial-myoepithelial tumor of the lung arising from bronchial mucosa-submucosa and occurring as a polypoid lesion of the upper left bronchus in a 47-year-old man is reported. The tumor did not infiltrate the cartilaginous wall of the bronchus and showed a biphasic histological appearance with a double layering of epithelial and myoepithelial cells. Myoepithelial spindle cells with eosinophilic cytoplasm were also observed. Mitotic figures were very rare and necrosis absent. Immunohistochemical study for epithelial and muscular markers confirmed the presence of a double-cell component in the tumor, namely epithelial and myoepithelial. The patient is alive and well, with no evidence of recurrent or metastatic disease 6 months after surgery. On the basis of the present case and the six previously reported cases, we suggest using the noncommittal term pulmonary epithelial-myoepithelial tumor of unproven malignant potential (PEMTUMP) for this type of neoplasm. In addition, we first introduce p63 as a novel marker for highlighting the myoepithelial cells of the respiratory tract and speculate on the role of these cells in the development of this unusual tumor.