Absence of a mutation of the p21/WAF1 gene in human lung and pancreatic cancers

Polymorphisms of p53 and p21 genes in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a multifactorial disease influenced by genetic and environmental factors, particularly cigarette smoking. Although cigarette smoke may be directly mutagenic, polymorphisms in the genes controlling acquired somatic mutations may also contribute, at least to some extent, to the observed differing susceptibilities to COPD. To investigate the involvement of genetic polymorphisms of p53 and p21 in the pathogenesis of COPD, the authors performed a case-control study involving 206 subjects with COPD and 210 healthy smokers as control subjects.

METHODS

Polymorphisms of p53 and p21 genes were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique on genomic DNA isolated from peripheral lymphocytes. The distribution of the p53 and p21 polymorphisms in healthy subjects and COPD patients was examined and compared using the Pearson X2 test. Significance was accepted at P < 0.05. Odds ratios (ORs) and 95% confidence intervals (CIs) of each specific genotype were calculated using logistic regression analysis to quantitatively assess the degree of association observed.

RESULTS

The distribution frequencies of genotypes of p53 codon 72 and p21 codon 31 were significantly different between the COPD and the control groups. Higher ORs for COPD were seen for persons with p53 Pro/Pro or Pro/Arg genotypes against Arg/Arg genotype [OR = 2.35, 95% CI 1.27-4.39, P = 0.008], or p21 Arg/Arg and Arg/Ser genotypes against Ser/Ser genotype [OR = 2.07, 95% CI 1.06-4.05, P = 0.033].

CONCLUSIONS

The polymorphisms of p53 and p21 were significantly associated with the occurrence of smoking-related COPD in Taiwan Chinese patients.

A codon 31ser-arg polymorphism of the WAF-1/CIP-1/p21/tumour suppressor gene in Chinese primary open-angle glaucoma

PURPOSE

Glaucomatous neuropathy is a type of cell death by apoptosis. Apoptosis is a genetically controlled form of cell death, and one of its primary regulatory steps is the activation of the tumour suppressor protein p53, of which p21 is an effector protein. The association between p21 codon 31 polymorphism and primary open-angle glaucoma (POAG) patients was evaluated in this study.

METHODS

The study included 58 POAG patients and a control group of 59 healthy volunteers. Polymerase chain reaction-based analysis was used to resolve the p21 codon 31 polymorphism.

RESULTS

The genotype frequencies of p21 codon 31 polymorphism were statistically different (p < 0.05) between the two groups. The Arg allele of the p21 codon 31 polymorphism was more frequently found in POAG patients than in healthy individuals (odds ratio: 2.389, 95% confidence interval: 1.14-5.01).

CONCLUSION

This study suggests that an association exists between the Arg allele of the p21 codon 31 polymorphism and POAG in the Chinese population.

Current understandings of the molecular genetics of gestational trophoblastic diseases

Gestational trophoblastic disease (GTD) is a heterogeneous group of diseases characterized by abnormally proliferating trophoblastic tissues. This includes partial and complete hydatidiform moles, invasive mole, choriocarcinoma and placental site trophoblastic tumour. Cytogenetic studies revealed that hydatidiform moles contain either solely (as in complete moles) or an excess (as in partial moles) of paternal contribution to the genome. Genomic imprinting is believed to play a pivotal role in the pathogenesis of hydatidiform moles. However its precise role and mechanism remains poorly understood. Hydatidiform mole carries a potential of malignant transformation. Similar to other human cancers, malignant transformation in gestational trophoblastic tumours is likely a multistep process and involves multiple genetic alterations including activation of oncogenes and inactivation of tumour suppressor genes. In addition, expression of telomerase activity, altered expression of cell--cell adhesion molecules and abnormal expression of matrix metalloproteinases have also been reported in GTD. These represent disruption of the delicate balance and regulation of cellular processes including proliferation, differentiation, apoptosis and invasion. The significance of these alterations in the pathogenesis and malignant transformation of gestational trophoblastic diseases is reviewed in this paper.

Correlation between TGF-beta1 and p21 (WAF1/CIP1) expression and prognosis in resectable invasive ductal carcinoma of the pancreas

Transforming growth factor-beta1 (TGF-beta1) inhibits the growth of a variety of epithelial cells; however, in many types of tumors it loses its inhibitory effect. p21(WAF1/CIP1), one of the cyclin-dependent kinase (Cdk) inhibitors induced by TGF-beta1, is considered a downstream effector of the growth-inhibitory function of TGF-beta1. We assessed the clinicopathologic significance of TGF-beta1 and p21 expression in resectable invasive ductal carcinoma (IDC) of the pancreas. Immunohistochemical examination of the expression of TGF-beta1 and p21 in 62 patients revealed positive expression of TGF-beta1 in 28 (45%) and of p21 in 25 (40%) of the 62 patients, and a significant correlation between the two expressions. The survival curve of patients with TGF-beta1(+) tumors was significantly higher than that of patients with TGF-beta1(-) tumors; p21(+) patients showed a higher survival curve than did p21(-) patients, but the difference was not statistically significant. Simultaneous analysis of TGF-beta1 and p21 expression showed that the patients with TGF-beta1(+)/p21(+) tumors had a significantly better prognosis than the others. Multivariate analysis showed that TGF-beta1 was a significantly low risk factor for death due to IDC. The concurrent evaluation of TGF-beta1 and p21 expression would be an effective tool in the prediction of the prognosis of patients with pancreatic cancer.

Cip/Kip cell-cycle inhibitors: a neuro-oncological perspective

The cell cycle is a precisely controlled cellular program that ensures normal cellular proliferation and development. The cyclin-dependant kinases (CDK) are molecules central to the continued progression through the cell-cycle checkpoints and as such are regulated by various mechanisms including cyclin levels, phosphorylation/dephosphorylation and cyclin-dependant kinase inhibitors (CKI). The CKIs are grouped into two families based on their structure and function, four lnk4 CKIs and three Cip/Kip CKIs. Abnormalities in these proteins can give rise to developmental defects and cancer. In this review, we will discuss the biochemistry and cell biology of the each of the Cip/Kip CKIs, their role in development as evidenced by targeted mutations in mice, and their role as possible tumor suppressor genes.

Lack of evidence of association of p21WAF1/CIP1 polymorphism with lung cancer susceptibility and prognosis in Taiwan

An association between the Arg allele of the p21WAF1/CIP1 codon 31 polymorphism and lung cancer has been reported. However, the genotype distribution of the p21 codon 31 polymorphism, as well as the association of this polymorphism with lung cancer risk and prognosis, remain undefined in the Taiwanese population. Therefore, we investigated the genotype distribution of the p21 codon 31 polymorphism in 155 lung cancer patients and 189 non-cancer controls. The genotype frequencies in the Taiwanese non-cancer controls were 0.51 (Ser) and 0.49 (Arg). Chi2 analysis indicated significant differences in Taiwanese genotype distribution of p21 from those reported for Swedes (P=0.001), Caucasians (P=0.001), Indians (P=0.001), and African-Americans (P=0.001). However, our data did not demonstrate an association of the Arg allele of the p21 polymorphism with lung cancer risk in Taiwan. Lung cancer patients with Ser/Arg and Arg/Arg genotypes were at a nonsignificant 1.15-fold increased risk of lung cancer when compared to individuals with the Ser/Ser genotype (95%CI, 0.70-1.86). In addition, although p21 is a downstream target of p53, we found no significant correlation of the p21 polymorphism with the p53 polymorphism and p53 gene mutation in lung cancer patients. We further investigated the association of the p21 polymorphism with prognosis in 154 lung cancer patients. Patients with the Ser/Ser genotype tended to have a poorer prognosis than those with the Ser/Arg and Arg/Arg genotypes (P=0.097, by the log rank test). Our data suggest that the p21 codon 31 polymorphism may not play a significant role in cancer susceptibility and the prognosis of lung cancer patients in Taiwan.

Relationship of p21(WAF1) expression with disease-free survival and biochemical recurrence in prostate adenocarcinomas (PCa)

BACKGROUND

The p21(WAF1) gene is considered to be one of the major regulators of the cell cycle. Its level of expression has been shown to correlate with pathologic stage and Gleason score in prostatic cancer. However, its relationship to clinical outcome is not yet well-characterized.

METHODS

Immunohistochemical staining for p21(WAF1) protein expression was performed in 62 consecutive radical prostatectomy specimens from our institution. The results were correlated with the disease-free survival and biochemical recurrence of the patients.

RESULTS

Thirty-four of the 62 patients were Caucasian and 28 were African American. There was a significant correlation between p21(WAF1) expression and biochemical recurrence after radical prostatectomy (P < 0.0095). However, while p21(WAF1) staining in prostate cancer was a prognostic indicator of disease-free survival in Caucasians (P < 0.0001), it appeared not to be a factor in African-American men (P = 0.908).

CONCLUSIONS

This study suggests that p21(WAF1) may have a role in the pathogenesis and progression of prostate carcinoma, and may serve as a predictor of biochemical recurrence of this tumor. The differences in the values of p21(WAF1) as a prognostic marker of disease-free survival in Caucasians vs. African Americans suggest that progression of prostate cancer may have different mechanisms in different ethnic groups.

Humoral immune response to p21WAF1/CIP1 in tumor patients, non-tumorous patients and healthy blood donors

We performed a serological analysis for anti-p21WAF1/CIP1 antibodies in sera of patients with different gynecological diseases such as breast cancer, ovarian carcinoma, cervix carcinoma and benign gynecological tissue alterations and from healthy blood donors using the immunoblotting technique with recombinant p21WAF1/CIP1 as antigen as well as a newly designed ELISA. We detected antibodies specific for p21WAF1/CIP1 in sera derived from cancer patients, as well as from patients with non-malignant diseases and from healthy blood donors. Thus, the presence of antibodies against p21WAF1/CIP1 is not a marker for malignancies. Some of the sera with antibodies against p21WAF1/CIP1 also contained antibodies against the oncoprotein mdm2, and/or the growth suppressor gene product p53. The presence of antibodies against p53 correlates with a malignant disease.

Alterations of the p53, p21, p16, p15 and RAS genes in childhood T-cell acute lymphoblastic leukemia

We investigated the alterations of the p53, p21, p16, p15 and RAS genes in childhood T-cell acute lymphoblastic leukemia (T-ALL) and T-ALL cell lines by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis and direct sequencing. Mutations of the p53 gene were found in three of 57 (5%) patients at diagnosis, one of 14 (7%) patients at relapse and in 12 of 18 (67%) cell lines. In these 12 cell lines, four had more than two mutations of the p53 gene. The p53 mutations were found in four of five cell lines whose original fresh leukemic cells were simultaneously examined original fresh leukemic cells. However, only one of the four fresh leukemic cells had the same mutation. All patients with p53 mutations in the course of disease died. Mutations of the p21 gene were not identified in 71 fresh samples and in 18 cell lines. N-RAS mutations were found in two of 57 (4%) fresh T-ALL patients at diagnosis, and four of 18 cell lines (22%), whereas no mutations were detected in any samples at relapse. Alterations of the p16 gene were found in 18 of 47 (38%) patients at diagnosis and in seven of 14 (50%) at relapse. These differences were not statistically significant. There were no differences in the frequency of alteration of the p16 and p15 genes between event-free patients and the remaining patients. Furthermore, we found the methylation of p16 gene in three of seven patients lacking homozygous deletions, suggesting higher frequency of p16 inactivation than previous reports in T-ALL. Interestingly, we found that one allele is inactivated by methylation and another allele had nonsense mutation in one cell line (KOPT-KI), resulting in loss of protein expression of p16. This type of p16 inactivation has not been so far reported in leukemia. We conclude that, (1) p53 mutations are infrequent at diagnosis but tend to be associated with poor clinical outcome; (2) RAS and p21 mutations may not be involved in the pathogenesis of T-ALL; (3) not only frequent alterations of p16 and p15 genes but also methylation of p16 gene are involved in initiating the leukemogenesis of T-ALLs, and (4) these 5 genes are independently involved in T-ALL.

p53 mutations predict non-small cell lung carcinoma response to radiotherapy

In vitro and animal studies, the effect of loss of p53 function on radiosensitivity is controversial. p21Waf1/Cip1 is a potent inhibitor of cyclin-dependent kinases and p21 gene polymorphisms are associated with some human cancers. We sought to determine whether p53 mutations or p21 polymorphisms affect response to radiotherapy in patients with recurrent non-small cell lung carcinoma (NSCLC). Thirty-four patients with NSCLC who underwent radiotherapy for recurrent tumors after potentially curative resection were studied. Gene alterations or polymorphisms were analyzed in DNA from the primary tumor tissue, and the response to radiotherapy was based on the metastatic lesion. Mutations in exons 5-8 of the p53 gene were detected by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis. p21 gene polymorphisms were identified by restriction digestion (BsmAI or PstI) of PCR products. Mutations in p53 were found in 13 of 34 patients (38.2%). The response rates (complete plus partial) were 15.4% for patients with tumors having p53 mutations and 61.9% for patients with wild-type p53 (P = 0.013). There was no significant difference between p21 polymorphisms and response to radiation. p53 gene mutations predict response to radiotherapy in NSCLC. Our results provide clinical support for the in vitro model that loss of p53 function decreases radiosensitivity.

Progress in understanding the molecular pathogenesis of human lung cancer

We review the molecular pathogenesis of lung cancer including alterations in dominant oncogenes, recessive oncogenes/tumor suppressor genes, alterations in growth regulatory signaling pathways, abnormalities in other pathways, such as apoptosis, autocrine and paracrine growth stimulatory loops, angiogenesis, and host immune responses, other mechanisms of genetic changes, such as microsatellite and methylation alterations, and the potential for inherited predisposition to lung cancer. These changes are related to multistage carcinogenesis involving preneoplastic lesions, and lung development and differentiation. The translational applications of these findings for developing new ways of early detection, prevention, treatment, and prognosis of lung cancer are discussed.

Role of p53 tumor suppressor gene in pancreatic endocrine tumors of Chinese patients

OBJECTIVE

The molecular genetic of pancreatic endocrine tumor (PET) has rarely been studied in depth because of its rarity. The aim of this study is to determine if there is any implication of p53 overexpression on the pathogenesis and clinicopathological parameters of PET.

METHODS

This study examines the immunohistochemical expression of the p53 gene product in 52 PETs (32 insulinomas, three gastrinomas, two glucagonomas, one carcinoid, and 14 nonfunctional tumors) from Chinese patients (27 men, 25 women) collected over a 23-yr period. Of these, 21% were malignant.

RESULTS

Irrespective of their demographic data, clinical behavior, hormonal status, or pathological features, none of the 52 PETs showed p53 overexpression.

CONCLUSIONS

This observation, together with an analysis of the literature, suggests that p53 gene aberrations may not be important in the pathogenesis of PET.

Accumulation of genetic alterations and their significance in each primary human cancer and cell line

Analyses of multiple genetic alterations accumulated in each cancer cell is expected to provide useful information to elucidate the molecular mechanisms involved in tumorigenesis. Here, we summarized the results of studies on aberrations of oncogenes and tumor suppressor genes by ourselves and other groups. DNAs analyzed were from particular sets of surgical specimens from human tumors and cancer cell lines derived from non-small cell lung cancers, pancreatic cancers, hepatocellular carcinomas and gliomas. Tumors could be grouped into two types based on the genetic alterations detected. Tumors in group 1 had mutations in genes encoding proteins involved in a limited number of signal transduction cascades such as p16-cyclin D1/CDK4-RB or MDM2-p53-p21, where the aberration of one component seems to be sufficient to cause dysfunction of the cascade. Group 2 contained a subset of tumors in which no alteration was detected in the genes analyzed, even in the advanced stage or established cancer cells, indicating the involvement of completely different oncogenic pathways.

p21WAF1/CIP1 expression in gestational trophoblastic disease: correlation with clinicopathological parameters, and Ki67 and p53 gene expression

BACKGROUND

The p21WAF1/CIP1 gene mediates growth arrest by inhibiting G1 cyclin dependent kinases and has been considered as a downstream effector of the tumour suppressor gene p53.

AIM

To analyse the role of p21WAF1/CIP1 in gestational trophoblastic disease.

METHODS

The immunohistochemical expression of p21WAF1/CIP1 gene was measured in 33 placentas, 28 partial hydatidiform moles, 54 complete hydatidiform moles, and 13 choriocarcinomas in paraffin wax embedded tissue. The results were correlated with p53 (DO7) and Ki67 (MIB1) immunoreactivity as well as clinical progress.

RESULTS

p21WAF1/CIP1 immunoreactivity was found predominantly in the nuclei of the syncytiotrophoblasts. p21WAF1/CIP1 protein expression correlated with gestational age in normal placentas (p = 0.0001) but not in hydatidiform moles (p = 0.89). Complete hydatidiform moles and choriocarcinomas had a significantly higher p21WAF1/CIP1 expression compared with normal placentas and partial hydatidiform moles (p < 0.001); there was no difference between placentas and partial hydatidiform moles. No correlation between p21WAF1/CIP1 expression and either the proliferation (Ki67) index (p = 0.34) or p53 protein accumulation (p = 0.68) was demonstrated. There was no significant difference (p > 0.05) in p21WAF1/CIP1 expression between the 17 patients who developed persistent gestational trophoblastic disease and those who did not.

CONCLUSIONS

This study suggests that p21WAF1/CIP1 expression in trophoblastic disease may be induced by a p53 independent pathway. The proliferative activity of gestational trophoblastic diseases might not be determined solely by the control of the cell cycle operated by p21WAF1/CIP1. p21WAF1/CIP1 expression is not an accurate prognostic indicator of gestational trophoblastic disease.

Lack of mutation in the WAF1/CIP1 gene during bovine leukemia virus-induced leukemogenesis

As a cyclin-dependent kinases (Cdks) inhibitor (CDI), the protein p21WAF1/CIP1 is able to interfere with cell cycle progression. Its expression is upregulated by wild-type p53, and the p21WAF1/CIP1 protein appears to be a potent effector of the p53-dependent cell cycle regulatory pathway. We have previously reported that p53 mutations frequently occur during bovine leukemia virus (BLV)-induced leukemogenesis in cattle but not in sheep. Therefore, we have investigated the involvement of p21WAF1/CIP1 mutations in the tumorigenic process associated with BLV. We first cloned the bovine and ovine WAF1 genes and determined the complete nucleotide sequences of their second coding exons. These sequences share respectively 79% and 80% homology with those of the human counterpart exon. In order to screen for mutations that could be associated with BLV-induced pathogenicity, we performed single strand conformation polymorphism (SSCP) assays on the WAF1 genes from BLV-induced tumors. No WAF1 mutations were detected in any of the ten BLV-induced bovine tumor samples. Among eleven sheep tumors and three ovine cell lines, only one sample revealed a single mutation in the WAF1 coding sequence, but this mutation was silent at the translational level. We concluded that mutations of the WAF1 gene are not involved in the development of the tumors during BLV-induced leukemogenesis.

Association between human cancer and two polymorphisms occurring together in the p21Waf1/Cip1 cyclin-dependent kinase inhibitor gene

BACKGROUND

The cyclin-dependent kinase inhibitor gene p21Waf1/Cip1 plays a role in signaling cellular growth arrest. In response to DNA damage, p21 is induced by the p53 gene, thereby playing a direct role in mediating p53-induced G1 arrest. Alterations in this gene may adversely affect regulation of cellular proliferation and increase susceptibility for cancer. Two polymorphisms have previously been characterized in the p21 gene: a C-->A transversion at codon 31 (ser-->arg) and a C-->T transition 20 nucleotides downstream from the 3' end of exon 3.

METHODS

The codon 31 polymorphism in exon 2 of the p21 gene was identified by restriction digestion (Alw26I) of products amplified by polymerase chain reaction (PCR). The polymorphism downstream from exon 3 of the p21 gene was identified by single strand conformation polymorphism (SSCP) analysis of PCR amplified products and was confirmed by PstI enzyme restriction digestion. DNA variant alleles were confirmed by direct DNA sequencing. The entire coding region and the promoter region (p53 binding domain) of the p21 gene were screened for mutations by SSCP analysis or DNA sequencing.

RESULTS

The two polymorphisms were found in 18 of 96 tumor samples lacking p53 alterations (18.8%). Nine of 54 prostate adenocarcinoma samples (16.7%) contained both p21 variants, whereas 9 of 42 squamous cell carcinomas of the head and neck (21.4%) displayed both polymorphisms. Of the 110 controls examined, 10 (9.1%) had both alterations. Both p21 polymorphisms occurred together in all samples examined and there was no indication of mutation in the coding region of the p21 gene or in the p53 binding domain of the promoter region.

CONCLUSIONS

These data suggest that p21 gene variants may play a role in increased susceptibility for the development of some types of cancer. In the current study, the authors demonstrated that the occurrence of these two polymorphisms is increased in prostate adenocarcinoma and squamous cell carcinoma of the head and neck. The polymorphic sites may be directly responsible for this apparent increased susceptibility or they may be linked to regulatory region alterations.

Molecular diagnosis of pancreas carcinoma

Cellular protooncogenes, tumor suppressor genes (antioncogenes), and DNA mismatch repair mutators are generally the key molecular genetic biomarkers undergoing alterations during carcinogenesis, i.e., activation of oncogenes, inactivation of tumor suppressors, and DNA mismatch repair gene defects are essential events in cancer causation. In pancreas cancer, high incidence of oncogene K-ras point mutations at the codon 12th is associated with premalignant and malignant transformation. Mutation in p53 tumor suppressor is also detected in pancreas adenocarcinoma. Concurrent loss of p53 and K-ras function may contribute to the clinical aggressiveness of pancreas cancer. Microsatellite instability and DNA mismatch repair defects may represent new mutator phenotype for pancreas carcinogenesis. Mutation of cell cycle regulators, such as inhibitor of CDK4 or p16 tumor suppressor gene, is a new molecular event in pancreas cancer. Mutation of cyclin-dependent kinases also may be involved in pancreas carcinogenesis. Loss or mutation of a new candidate tumor suppressor, DPC4 (deleted in pancreas carcinoma locus 4), is reported in pancreas cancer. The protein products of these gene mutations are potential tumor antigens, thus genotype expression can be detected by phenotype. Most of these emerging molecular genetic biomarkers are associated with regulation of cell growth and recognition, as well as gene expression, and may offer new insight into the cellular precursors to and genesis of pancreas cancer.

Failure to detect mutations in the retinoblastoma protein-binding domain of the transcription factor E2F-1 in human cancers

The functions of the transcription factor E2F-1 are regulated by the RB protein through the RB-binding domain of E2F-1 and this factor is considered to be an important molecule that functions downstream of the RB protein. In order to determine whether E2F-1 that cannot bind to RB might be associated with various human cancers, we searched for mutations in the RB-binding domain of E2F-1 using samples of DNA from various clinical specimens obtained from 406 cancer patients (with lung, pancreatic, stomach, colon, esophageal, and hepatic cancers) by analysis of polymerase chain reaction-mediated single-strand conformational polymorphism. No mutations or deletions were detected in genes for E2F-1 from any of the tumor tissues examined. These results suggest that a mutation or deletion in E2F-1 that might affect binding of the RB protein is not involved in human cancers.