Mutational analysis of the p27(kip1) gene in hepatocellular carcinoma

p27 inhibits CDK6/CCND1 complex formation resulting in cell cycle arrest and inhibition of cell proliferation

p27 plays critical roles in cell proliferation, differentiation, and apoptosis, which have been well studied in mammals and Drosophila. However, the mechanisms underlying p27 regulation of the cell cycle have not been thoroughly researched. In this study, Genevestigator, Kaplan-Meier Plotter, and the Human Protein Atlas databases were used to analyze the expression of p27, cell division protein kinase 6 (CDK6), and cyclin D1 (CCND1), as well as its prognostic value in different tumor tissues and corresponding normal tissues. Quantitative PCR and immunohistochemistry were used to detect the expression of p27, CDK6, and CCND1 in the tissues of cancer patients. The effects of p27, CDK6, and CCND1 on the proliferation of lung cancer cells were examined by the MTT assay, and flow cytometry was used to investigate the mechanism by which p27 affected cell proliferation. Immunofluorescence, co-immunoprecipitation, and Western blotting were used to determine if p27 interacted with CDK and CCND1 to regulate the cell cycle. The results showed that p27, CDK6, and CCND1 played different roles in tumorigenesis and development, which are in accordance with CDK6 and CCND1 in affecting the cell cycle and cell proliferation. p27 regulated the cell cycle and inhibited cell proliferation by affecting formation of the cell cycle-dependent complex CDK6/CCND1, but did not directly affect the expression of CDK6 and CCND1. Moreover, CCND1 did not regulate the cell cycle alone, but rather, functioned together with CDK6. This study provides insights into the effects of p27 on tumor formation and development, and the underlying regulatory mechanisms.

Promoter hypermethylation of p73 and p53 genes in cervical cancer patients among north Indian population

Hypermethylation of CpG islands leads to transcriptional silencing and it is the predominant mechanism of tumor suppressor gene inactivation in many tumors. Methylation-specific polymerase chain reaction was performed to analyse the methylation status of the promoter region of the tumor suppressor genes. Hypermethylation of the 5' CpG island of the p21 ( CIP1 ), p27 ( KIP1 ), p57 ( KIP2 ), p53, p73 and RB 1 gene promoter were found in 8.8, 8.8, 11.2, 12, 25.6 and 4.8 % of 125 cervical cancer samples from north Indian population, respectively. Methylation of p73 was significantly (P < 0.001) associated with the cervical cancer cases in comparison to controls. Significant correlation was also observed between the methylation of p73 gene and increase in the risk of cervical cancer among passive smokers. Promoter hypermethylation of p53 gene was also observed to be significant among oral contraceptive users and cervical cancer patients having age at first sexual intercourse <20 years whereas hypermethylation of other genes was not found to be significant in the present study. This is the first report showing significant hypermethylation of p73 and p53 genes among cervical cancer patients in north Indian population. This is also the first report on significant p53 hypermethylation in cervical cancer in any population. Our findings did not show any correlation between promoter methylation of p73 and the other genes under study with clinicopathological parameters, including human papillomavirus infection and stage of the disease. The frequency of aberrant methylation of p73 and p53 gene promoter was unchanged according to the age of patients.

Somatic mutation and germline sequence abnormalities in CDKN1B, encoding p27Kip1, in sporadic parathyroid adenomas

CONTEXT

Typical nonfamilial (sporadic) parathyroid adenomas are common endocrine tumors for which no predisposing germline DNA variants and only a few clonally altered genes that drive parathyroid tumorigenesis have been identified. CDKN1B, encoding cyclin-dependent kinase inhibitor p27(kip1), has recently been implicated in a multiple endocrine tumor phenotype in rats and, rarely, in a human familial MEN1 (multiple endocrine neoplasia type 1)-like disorder.

OBJECTIVE

We sought to determine whether mutation of CDKN1B might contribute to the development of common sporadic parathyroid adenomas.

PATIENTS AND DESIGN

We sequenced the CDKN1B gene in 86 parathyroid adenomas from patients with typical, sporadic presentations of primary hyperparathyroidism. Identified alterations were categorized as somatic or germline, and their functional consequences were examined.

RESULTS

CDKN1B sequence abnormalities were identified in four parathyroid adenomas. Acquired biallelic alteration of CDKN1B, resulting from somatic mutation plus loss of heterozygosity, was detected in one tumor. Germline origin was documented in two cases despite nonfamilial presentations. None of the observed alterations were found in 240 CDKN1B alleles from normal individuals, nor among more than 2,000 previously reported alleles. Most identified variants reduced p27(kip1) protein levels or altered in vitro stability.

CONCLUSIONS

In typical, sporadic parathyroid adenomas, CDKN1B mutation can be somatic and clonal, indicative of a directly conferred selective advantage in parathyroid tumorigenesis. Additionally, the identification of germline CDKN1B variants in patients with sporadic presentations provides evidence for CDKN1B as a susceptibility gene in the development of typical parathyroid adenomas.

Immunohistochemically detected expression of p27(Kip1) and Skp2 predicts survival in patients with intrahepatic cholangiocarcinomas

In intrahepatic cholangiocarcinomas (ICCs), the prognostic significance of p27(Kip1), a cyclin-dependent kinase inhibitor, remains controversial, and there have been no studies of degradation pathway associated proteins, S-phase kinase-interacting protein (Skp2), and Jun activation domain-binding protein-1 (Jab1). In the present study of 74 patients with ICC-mass forming type (ICC-MF) undergoing radical surgery, we determined immunohistochemical expression of p27(Kip1), Skp2, and Jab1 and examined relationships with clinicopathologic findings and patient survival. On the basis of the average of labeling indices, we set cutoff values to define high and low expressors and divided the cases into two groups. A statistically significant correlation was found between low p27(Kip1) expression and lymph node metastasis (P = .009). Patient survival in the low p27(Kip1) expression group (n = 25) was also significantly worse than that in the high p27(Kip1) expression group (n = 49, P = .0007). A significant inverse correlation was found between p27(Kip1) and Skp2 expression (P = .016). High Skp2 expression (n = 36) was significantly associated with poor prognosis (P = .0046). High Jab1 expression was observed in 32 cases, but there was no statistically significant relationship with clinicopathologic findings or patient survival. The multivariate analysis revealed that low p27(Kip1) and high Skp2 expression are independent and significant factors of poor prognosis. The results suggest that low p27(Kip1) and high Skp2 expression are associated with aggressive tumor behavior, and these cell-cycle regulators are useful markers to predict outcome of patients with ICC-MF.

p27(Kip1)is overexpressed in very early stages of hepatocarcinogenesis

Hepatocellular carcinoma (HCC) associated with chronic liver disease evolves from precancerous lesions and early HCC to more malignant forms. Despite the demonstrated importance of cell-cycle regulators in tumor biology, there have been few studies of their role in multistep hepatocarcinogenesis. Expression of p27(Kip1) and a degradation pathway associated protein, S-phase kinase-interacting protein 2 (Skp2), was therefore evaluated in surgically resected specimens of eight adenomatous hyperplasias, 16 early HCC and 126 classical HCC. Immunohistochemistry revealed no p27(Kip1) expression in the majority of hepatocytes from normal and cirrhotic liver, whereas positive staining for p27(Kip1) protein was found in 75.0% and 93.8% of adenomatous hyperplasias and early HCC, respectively. The average p27(Kip1) labeling indices (LI) for adenomatous hyperplasias, early HCC, well differentiated HCC, moderately differentiated HCC and poorly differentiated HCC were 36.99, 43.59, 47.73, 49.24, and 30.21, respectively. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) analyses confirmed the increases. Skp2 LI were also significantly elevated in accordance with stepwise progression of hepatocarcinogenesis. Increased expression of Skp2 mRNA was observed most frequently in less differentiated tumors and Kaplan-Meier survival analysis showed a significantly association with a poor prognosis (P = 0.0496). In conclusion, a high level of p27(Kip1) expression is evident from early stages of hepatocarcinogenesis, indicating that this parameter could be a useful diagnostic marker for precancerous lesions and early HCC. In addition, Skp2 expression correlates with tumor dedifferentiation and may contribute to biological aggression in HCC.

PI3K/Akt/p27kip1 pathway mediates chemoresistance to Etoposide and Doxorubicin in gastric carcinoma cell line BGC-823 and its mechanism

AIM: To investigate the effect of chemo-resistance to Etoposide and Doxorubicin mediated by the PI3K/Akt/p27 pathway on human gastric carcinoma cell line BGC-823 and its mechanism.

METHODS: Cultured BGC-823 gastric cancer cells were divided into control group, PI3K/Akt/p27 Kip1 channel inhibitor Wort (Wort) group, Etoposide (Eto) group, Doxorubicin (Dox) group, Eto + Wort group and Dox + Wort group. Cell survival was assessed with MTT method. Cell cycle and apoptosis were detected using a flow cytometer (FCM). Expression level of p27 Kip1 and p27 gene mRNA was determined by Western blotting analysis and reverse transcription-polymerase chain reaction, respectively.

RESULTS: The cell survival rate at 24 h was lower in Wort group, Eto +Wort group and Dox +Wort group than in control group (57.8%, 46.5%, 44.3% vs 46.5%, 44.3%, P < 0.01). The cell ratio in G₀-G₁ phase was higher in Wort group, Eto +Wort group and Dox + Wort group than in control group (85.0 ± 3.54, 91.5 ± 3.63, 92.4 ± 3.64 vs 71.5 ± 3.25, P < 0.01) and the protein expression was increased at 12 h and 24 h. The cell survival rate in Eto and Dox groups was higher than that in control group, but no obvious change was found in G₀ - G₁ phase. The p27 mRNA expression was similar in different groups.

CONCLUSION: Activation of PI3K/Akt/p27 channel can mediate chemo-resistance to tumor cells.

Molecular analysis of the p27/kip1 gene in breast cancer

BACKGROUND

Genetic polymorphisms and mutations of the genes involved in tumorigenesis may determine individual susceptibility for cancer. The p27/Kip1 protein belongs to the family of cyclin-dependent kinase-inhibitory proteins, which are negative regulators of cell-cycle progression. Reduced protein levels of p27/Kip1 have been reported in numerous human cancers including breast cancer.

METHODS AND RESULTS

p27 gene mutations and the codon 109 polymorphism were investigated in breast cancer patients by single strand conformation polymorphism analysis, PCR-restriction fragment length polymorphism analysis and DNA sequencing. Mutations were identified in 2 of 24 breast tumor samples. One G-->A transition resulting in a silent mutation and a single base deletion resulting in a nonsense mutation were detected in one patient. Another breast cancer sample harbored a T-->A transition at codon 159. An association between the codon 109 B allele and breast cancer was observed.

CONCLUSION

Our study indicates that mutational alterations in the p27 gene are rare in human breast cancer. The codon 109 B allele is associated with high-grade tumors.

Expression and hypermethylation of p27kip1 in hepatocarcinogenesis

AIM: To study the expressions of p27^kip1 protein and p27mRNA, the hypermethylation of p27^kip1 and the relation between them in various stages of hepatocarcinogenesis.

METHODS: p27 protein and p27mRNA were detected by immunohistochemical staining and in situ hybridization respectively in 68 cases of normal liver, liver cirrhosis, pericancerous cirrhosis and hepatocellular carcinoma (HCC). The hypermethylation of p27^kip1 was detected by methylation-specific PCR (MSP) in 44 cases of normal liver, liver cirrhosis, and HCC.

RESULTS: The positive rate of p27 protein was 66.7% (4/6) in normal liver, 60.0% (6/10) in liver cirrhosis, 50.0% (12/24) in pericancerous cirrhosis and 21.4% (6/28) in HCC. There were no statistical differences in normal liver, liver cirrhosis and pericancerous cirrhosis, but the positive rate of p27 protein significantly decreased in HCC compared to that in the other groups (P = 0.006, χ² = 7.664). The positive rate of p27^kip1 mRNA was 83.3% (5/6) in normal liver, 70.0% (7/10) in liver cirrhosis, 75.0% (18/24) in pericancerous cirrhosis and 25.0% (7/28) in HCC. There were no statistical differences in normal liver, liver cirrhosis and pericancerous cirrhosis, but the positive rate of p27^kip1 mRNA also significantly decreased in HCC compared to that in the other groups (P = 0.000, χ² = 16.600). In addition, there was a significant correlation between the expression of p27 protein and p27mRNA in the integrated group of normal liver and liver cirrhosis. However, no significant correlation was found between pericancerous cirrhosis and HCC. Using MSP, we found that 1 HCC in 44 cases (including 6 cases of normal liver, 10 cases of liver cirrhosis and 28 cases of HCC) was methylated, whose p27 protein and p27mRNA were negative.

CONCLUSION: The reduction or loss of p27 protein and p27mRNA are potentially involved in hepatocarcinogenesis. The hypermethylation of p27 might lead to the loss of p27mRNA transcription.

A single-nucleotide polymorphism in the human p27kip1 gene (-838C>A) affects basal promoter activity and the risk of myocardial infarction

BACKGROUND

Excessive proliferation of vascular smooth muscle cells and leukocytes within the artery wall is a major event in the development of atherosclerosis. The growth suppressor p27kip1 associates with several cyclin-dependent kinase/cyclin complexes, thereby abrogating their capacity to induce progression through the cell cycle. Recent studies have implicated p27kip1 in the control of neointimal hyperplasia. For instance, p27kip1 ablation in apolipoprotein-E-null mice enhanced arterial cell proliferation and accelerated atherogenesis induced by dietary cholesterol. Therefore, p27kip1 is a candidate gene to modify the risk of developing atherosclerosis and associated ischaemic events (i.e., myocardial infarction and stroke).

RESULTS

In this study we found three common single-nucleotide polymorphisms in the human p27kip1 gene (+326T>G [V109G], -79C>T, and -838C>A). The frequency of -838A carriers was significantly increased in myocardial infarction patients compared to healthy controls (odds ratio [OR] = 1.73, 95% confidence interval [95%CI] = 1.12-2.70). In addition, luciferase reporter constructs driven by the human p27kip1 gene promoter containing A at position -838 had decreased basal transcriptional activity when transiently transfected in Jurkat cells, compared with constructs bearing C in -838 (P = 0.04).

CONCLUSIONS

These data suggest that -838A is associated with reduced p27kip1 promoter activity and increased risk of myocardial infarction.

Loss of p27(Kip1) accelerates DNA replication after partial hepatectomy in mice

BACKGROUND

Liver regeneration after partial hepatectomy (PH) is accomplished by a synchronous replication of hepatocytes. Both positive and negative regulators of cyclin-dependent protein kinase (Cdk) have been implicated in hepatocyte proliferation, but their specific roles in vivo remain to be clarified. To investigate the specific role of p27(Kip1), a member of the Cip/Kip family of Cdk inhibitors, in cell-cycle regulation during liver regeneration, p27-knockout mice were studied after PH.

MATERIALS AND METHODS

Under ether anesthesia, mice were subjected to 70% PH. Animals were sacrificed at intervals after the surgery, and the remnant liver was harvested and analyzed.

RESULTS

In p27-deficient mice, the timing of DNA synthesis was significantly accelerated with a perturbation in the ordered distribution of proliferating cells in the hepatic lobule. p27 deficiency, however, did not affect the whole population of cycling cells, the number of apoptotic cells, or liver injury and mortality after PH.

CONCLUSION

These data provide in vivo evidence that p27 functions as a brake in the "start" of the hepatocyte cell cycle, thereby coordinating temporally and spatially the onset of DNA synthesis of hepatocytes within the hepatic lobules.

p27(Kip1) is an independent predictor of recurrence after surgical resection in patients with small hepatocellular carcinoma

BACKGROUND/AIMS

Alterations in p27(Kip1) (p27) and cyclin E (cycE) expression are found in tumors and are related to poor prognosis. This study assesses the role of these cell cycle regulators in the development of recurrence after surgical resection in 46 cirrhotic patients (age: 61.3+/-7 years, 30 males, 44 Child-Pugh's A, 30 HCV-positive) with small hepatocellular carcinoma (HCC, size: 3.1+/-1.5cm, 40 solitary at pathological examination).

METHODS

p27 and cycE expression in tumoral and non-tumoral liver were analyzed by Western blot (WB). p27 was also assessed by immunohistochemistry (IHC).

RESULTS

Tumor p27 underexpression (50% decreased vs. non-tumoral liver) occurred in 12 cases. Throughout follow-up, 26 patients developed recurrence, which was significantly higher in patients with p27 underexpression than in those without (3-year recurrence: 80 vs. 44%, respectively, P=0.026). IHC showed concordant inverse findings: 13 tumors showed high p27 staining that was related to lower recurrence rate (P=0.019). Multivariate analysis identified p27 measured by WB as an improved predictor of recurrence (OR: 3.09, 95% CI: 1.26-7.08, P=0.016). By contrast, cycE, increased in 66% of the tumors, had no impact on recurrence but was associated to poor differentiation (P=0.015) and microvascular invasion (P=0.016).

CONCLUSIONS

p27 underexpression is frequent in relatively early stages of HCC and constitutes an independent predictor of recurrence after surgical resection.

Molecular cloning and characterization of a novel gene which is highly expressed in hepatocellular carcinoma

To gain new insight into the molecular mechanism underlying the pathogenesis of human primary hepatocellular carcinoma (HCC), we searched for HCC-specific molecules through screening genes that are differentially expressed between cancerous and noncancerous counterparts of liver and identified a novel HCC-associated gene, HCCA1 encoding a approximately 80 kDa cytoplasmic protein that contains several proline-rich motifs likely for SH3-binding. HCCA1 transcript, albeit present in some adult tissues, is up-regulated selectively in HCC but not in other tumor cells. High expression of HCCA1 occurs as a late event frequently (89.2%) in HCCs and correlated significantly with the degree of tumor progression. When treated with antisense oligonucleotides to HCCA1, HCCA1 expression in HCC cells (HuH-7) was effectively suppressed and cell growth was down-regulated in a time- and dose-dependent manner. Furthermore, HuH-7 cells harboring the HCCA1 antisense expression clone displayed a remarkably reduced efficiency in colony formation. Together, these data strongly suggest that HCCA1 is a positive effector in cell proliferation and contributes to HCC carcinogenesis and progression. We believe that this protein will serve as a novel useful marker for HCC and is a potential target for pharmaceutical intervention of this malignant disease.

Expression of p27(KIP1) and p21(WAF1/CIP1) in primary hepatocellular carcinoma: clinicopathologic correlation and survival analysis

To investigate the possible roles of p27(KIP1) and p21(WAF1/CIP1), inhibitors of cyclin-dependent kinases, in hepatocellular carcinoma (HCC), we examined p27(KIP1) and p21(WAF1/CIP1) expression in primary HCC with immunohistochemistry and Northern blot hybridization and correlated the results with clinicopathologic features and survival. With immunohistochemistry, positive staining for p27(KIP1) and p21(WAF1/CIP1) protein was found in 54.3% and 63.8% of HCCs, respectively. Both p27(KIP1) and p21(WAF1/CIP1) scores of the tumors were significantly higher than those of the corresponding nontumorous livers (P <.0001 and.009, respectively). Higher levels of p27(KIP1) were associated with a lower incidence of direct liver invasion (P =.021) and, less significantly, with a low incidence of multiple tumor nodules (P =.056). Patients whose tumors had higher p27(KIP1) protein scores had longer disease-free survival (P =.011). For p21(WAF1/CIP1), in contrast to the overexpression of the p21(WAF1/CIP1) protein in HCC, the relative amounts of p21(WAF1/CIP1) messenger RNA (mRNA) in the tumors were found to be reduced compared with those of the nontumorous livers (P =.039). In conclusion, p27(KIP1) and p21(WAF1/CIP1) proteins were frequently overexpressed in HCC. Longer disease-free survival rates were seen in patients whose tumors had higher p27(KIP1) expression. The accumulation of p21(WAF1/CIP) protein in the presence of a reduced mRNA level suggests probable posttranslational protein stabilization, and the reduced transcription of p21(WAF1/CIP) may represent a form of dysfunction of cyclin-dependent kinase inhibitor involved in hepatocarcinogenesis.