Novel polymorphism in p21(waf1/cip1) cyclin dependent kinase inhibitor gene: association with human esophageal cancer

p21(waf1/cip1), an important regulator of the cell cycle, binds to PCNA and acts as a mediator of the growth suppressing and apoptosis promoting functions of p53. We report a hitherto unobserved polymorphism in the carboxy terminal domain (codon 149) of p21(waf1/cip1) gene, the domain encoding the PCNA binding motif. The codon 149 polymorphism (GAT-->GGT) was observed in 42 of 50 (84%) esophageal squamous cell carcinomas (ESCCs) and eight of 50 (16%) normal individuals. The resultant amino acid substitution from aspartate to glycine may have vital implication in PCNA mediated cell cycle regulation by p21(waf1/cip1). The second polymorphism at codon 31, involving a C-->A transversion at nucleotide 168 (AGC-->AGA) changing the amino acid from serine to arginine, was observed in 2/50 (4%) ESCCs at a relatively lower frequency in the Indian population than that reported in the West. No significant association was observed between p21(wap1/cip1) polymorphism at codon 149 and p21(wap1/cip1) protein expression in ESCC in this cohort of patients. Interestingly, the frequency of p21(wap1/cip1) variants (codon 149) in ESCCs (18 of 19 cases) with wild-type p53 was significantly higher than in tumors with p53 mutations, suggesting that this polymorphism affects the p53 pathway and may play an important role in esophageal tumorigenesis. Analysis of p21(waf1/cip1) expression in relation to p53 gene and protein status revealed its induction by p53-dependent as well as independent pathways in esophageal tumorigenesis.     

错配修复基因hMLH1和hMSH2在散发性大肠癌中的表达及其意义

目的 探讨错配修复基因hMLH1和hMSH2在散发性大肠癌(SCC)组织中的表达及其临床意义.方法 采用免疫组化Max Vision二步法对63例SCC标本中的癌组织、距癌灶3 cm以外的癌旁组织、距癌灶10 cm以外的正常组织中hMLH1和hMSH2蛋白的表达进行检测.结果 hMLH1蛋白在63例正常大肠组织、癌旁组织和SCC组织中的阳性表达率分别为95.2%、85.7%和81.0%,hMLH1蛋白在SCC组织中的阳性表达率明显低于正常大肠组织(P＜0.05).hMSH2蛋白在63例正常大肠组织、癌旁组织和SCC组织中的阳性表达率分别为76.2%、66.7%和52.4%,hMSH2蛋白在SCC组织中的阳性表达率明显低于正常大肠组织(P＜0.01).hMLH1蛋白在＜60岁的SCC患者组织中的阳性表达率(100%)明显高于≥60岁的SCC患者组织(75.0%,P＜0.05),在有淋巴结转移的SCC组织中的阳性表达率(50.0%)明显低于无淋巴结转移的SCC组织(93.3%,P＜0.05).hMSH2蛋白在＜60岁的SCC患者组织中的阳性表达率(80.0%)明显高于≥60岁的SCC患者组织(43.8%,P＜0.05),在癌组织浸润至肠壁浆膜层SCC组织中的阳性表达率(61.5%)明显高于浸润至黏膜下层和肌层的SCC组织(37.5%,P＜0.05).SCC组织中hMLH1和hMSH2蛋白的表达呈正相关关系(r=0.254,P＜0.01).结论 hMLH1和hMSH2蛋白在SCC组织中的表达均有一定的缺失,并且与患者的年龄、淋巴结转移和癌组织浸润的范围有关.hMLH1和hMSH2基因可以作为临床预测和判断SCC发生和发展有用的实验室指标.     

Roles of mismatch repair proteins hMSH2 and hMLH1 in the development of sporadic breast cancer

Defects in mismatch repair (MMR) genes, particularly the hMSH2 and hMLH1 genes, are associated with a variety of cancers including sporadic breast cancer. However, whether or not patient clinical background, e.g. age, progesterone receptor (PR), estrogen receptor (ER), tumor progression and stage, chemotherapy history, and menopausal status, influences MMR status is not understood. To address these issues, 83 archival breast cancer specimens were examined for expression of hMSH2 and hMLH1 by immunohistochemistry and the relationship between MMR protein expression and patient clinical background was analyzed. We detected lack of or reduced expression of hMSH2 and hMLH1 in 23 (27.7%) and 26 cases (31.3%), respectively, and hypermethylation of the hMLH1 promoter accounted for the majority of the cases with reduced expression of hMLH1. Statistical analysis revealed that (i) reduced expression of hMLH1 and hMSH2 seemed to confer advantage for the progression of breast tumors to more advanced stages; (ii) attenuated expression of hMLH1 correlated with history of chemotherapy, but not with age, menopause, or the status of PR and ER; (iii) hypermethylation of the hMLH1 promoter was linked with clinical stage and lymphatic metastasis. These analyses indicate that defective expression of MMR genes is closely associated with the development of sporadic breast cancer.     

p21(waf1/cip1)-null human fibroblasts are deficient in nucleotide excision repair downstream the recruitment of PCNA to DNA repair sites

The cyclin-dependent kinase inhibitor p21(waf1/cip1) is known to impair DNA synthesis by binding to PCNA, the co-factor of DNA polymerases delta and epsilon. However, a positive role for p21 in nucleotide excision repair (NER) has been suggested. In this study, the sensitivity to DNA damage and DNA repair efficiency were investigated in p21-null human fibroblasts obtained by targeted homologous recombination. After UV-C irradiation, p21-/- cells showed a threefold reduction in clonogenic survival and an increased susceptibility to apoptosis, as compared with parental p21+/+ cells. Removal of cyclobutane pyrimidine dimers was significantly reduced in p21-/- cells both in the whole genome, and at the level of the rDNA gene cluster, as determined by immunoassay and Southern blot, respectively. After DNA damage, the recruitment of PCNA as detergent-insoluble form associated to DNA repair sites in p21-/- fibroblasts, was comparable to that observed in parental p21+/+ cells. However, PCNA remained associated with DNA for a longer period in p21-/- than in p21+/+ cells. These results suggest that in human cells, p21 is required for NER at a step located downstream the recruitment of PCNA to DNA repair sites.     

Expression of p53 and p21waf1/cip1 in gastric carcinoma: lack of inter-relationship or correlation with prognosis.

AIMS: The cell cycle regulators p53 and p21waf1/cip1 are expressed variably in human cancers. We investigated their expression in gastric carcinoma and determined their inter-relationship and prognostic significance. METHODS: Immunohistochemistry was used to determine their expression in material from 100 resected specimens of gastric carcinoma, and comparison was then made of the degree of expression between each, with conventional clinicopathological indices and with survival. RESULTS: Positivity was found with p53 (40%) and p21 (75%). There was no significant correlation between the expression of each individual marker, nor between each marker and 5-year survival. There appeared to be an association between p53 expression and lymph node metastases, and a higher frequency of p21waf1/cip1 expression in males. CONCLUSIONS: The expression of p53 and p21waf1/cip1 as detected by immunohistochemistry were of no value in predicting the prognosis of patients with gastric carcinoma.     

Expression of the DNA mismatch repair proteins hMLH1 and hPMS2 in normal human tissues.

hMLH1 and hPMS2 are part of the DNA mismatch repair complex. Mutations in these genes have been linked to hereditary non-polyposis colon cancer; they also occur in a variety of sporadic cancers. Western blot analysis and immunohistochemistry demonstrated that hMLH1 and hPMS2 are widely expressed nuclear proteins with a distribution pattern very similar to that previously described for hMSH2. These observations showing similar localization of hMLH1 and hPMS2 with hMSH2 are consistent with the biochemical function of these proteins in DNA mismatch repair.     

错配修复基因hMSH2和hMLH1在结直肠癌组织中的表达及临床意义

  目的   评价hMLH1和hMSH2蛋白在结直肠癌中的表达及意义。   方法   选取2009年1月至2011年12月经病理学确诊的结肠癌手术切除标本72例, 所有患者在术前均未接受过放疗或化疗, 内镜活检取正常肠黏膜上皮25例。免疫组织化学检测hMLH1和hMSH2蛋白表达情况。   结果   结直肠癌组织中hMSH2缺失率为88.9% (64/72), 高于正常肠组织中hMSH2蛋白缺失率28.0% (7/25)。hMSH2蛋白缺失率随T分期增加而增加, 但差异无统计学意义(χ2=37.622, P < 0.001);hMSH2蛋白缺失率与N分期相关, 有淋巴结转移者的hMSH2蛋白缺失40例, 缺失率达97.6% (40/41), 无淋巴结转移患者的hMSH2蛋白缺失率为77.4% (24/31, χ2=7.251, P=0.007)。而hMLH1蛋白缺失率为90.3% (65/72), 高于正常组肠组织中hMLH1蛋白缺失率为32.0% (8/25, χ2=33.847, P < 0.001), 但与肿瘤部位、分期、分化程度均无关。   结论   在结直肠癌组织中存在错配修复基因hMSH2和hMLH1蛋白缺失, 且表达缺失与肿瘤分期有关。通过免疫组织化学方法检测hMLH1和hMSH2蛋白表达可以简便、准确地发现错配修复基因的突变, 从而对其后期的治疗和预后判断有参考价值。      

DNA mismatch repair genes hMLH1, hMSH2, and hMSH6 are not inactivated in bronchioloalveolar carcinomas of the lung.

BACKGROUND: Defective DNA mismatch repair (MMR) appears to be rare in nonsmall cell carcinomas of the lung. Defective DNA MMR results from genetic or epigenetic alterations that inactivate the DNA MMR genes hMLH1 or hMSH2, and rarely hMSH6. The loss of normal DNA MMR is thought to promote tumorigenesis by accelerating the accumulation of mutations in oncogenes and tumor suppressor genes. Inactivation of hMLH1, hMSH2, and hMSH6 is observed as a loss of expression of these proteins by immunohistochemistry. Bronchioloalveolar carcinoma is a subtype of adenocarcinoma with distinctive clinical and pathologic features. MATERIALS AND METHODS. An immunohistochemical study was performed on paraffin embedded sections of 33 bronchioloalveolar carcinomas (20 nonmucinous and 13 mucinous) for hmlh1, hmsh2, and hmsh6 proteins. RESULTS All the tumors showed normal expression of hmlh1, hmsh2, and hmsh6. CONCLUSIONS: These findings suggest that defective DNA MMR due to inactivation of hMLH1, hMSH2, or hMSH6 does not play a significant role in the pathogenesis of bronchioloalveolar carcinomas.     

Immunohistochemical analysis of expression and allelotype of mismatch repair genes (hMLH1 and hMSH2) in bladder cancer

Mutation of human homologues of DNA mismatch repair (MMR) genes in tumours has been shown to be associated with the phenomenon of microsatellite instability (MSI). Several studies have reported the occurrence of MSI in bladder cancer, but evidence of involvement of MMR genes in the pathogenesis of this cancer is still unclear. We therefore utilized quantitative immunohistochemical (IHC) image analysis and PCR-based allelotype analysis to determine hMLH1 and hMSH2 genes alteration in a cohort of Egyptian bladder cancer samples. IHC analysis of 24 TCC and 12 SCC revealed marked- intra and intertumour heterogeneity in the levels of expression of the two MMR proteins. One TCC lost MLH1 expression and one lost MSH2, (1/24, 4%), and one SCC lost MSH2 (1/12, 8%). A large proportion of analysed tumours revealed a percentage positivity of less than 50% for MLH1 and MSH2 expression (44% and 69%, respectively). Complete loss of heterozygosity in three dinucleotide repeats lying within, or in close proximity to, hMLH1 and hMSH2 was rare (2/57, (4%) for MLH1; and 1/55, (2%) for MSH2), however allelic imbalance was detected in 11/57 (hMLH1) and 10/55 (hMSH2) at any of the informative microsatellite loci. These alterations in structure and expression of DNA MMR genes suggest their possible involvement in the tumorigenesis and/or progression of bladder cancer.     

The cyclin-dependent kinase inhibitor p21(cip1/waf1) enhances the cytotoxicity of ganciclovir in HSV-tk transfected ovarian carcinoma cells

Suicide gene therapy could be an attractive addition to the treatment of ovarian carcinomas, for which acquired chemoresistance frequently results in treatment failure. Here we show that transfection of the HSV-tk gene, followed by incubation with up to 1 mM ganciclovir fails to induce cell death in SKOV3 chemoresistant human ovarian carcinoma cells. However, co-transfection of HSV-tk with Cip1/Waf1 encoding the p21(cip1/waf1) inhibitor of cdks, allows 100 microM ganciclovir to eradicate the population of tumor cells. Potentiation of a drug by co-transfer of HSV-tk with Cip1/Waf1could thus represent another therapeutic approach for tumours that are resistant to conventional therapy.     

The Role of Expression of Mismatch Repair Proteins hMSH2 and hMLH1 in Gastric Carcinogenesis and its Clinical Significance

OBJECTIVE To investigate the expression of the mismatch repair proteins hMSH2 and hMLH1,and to examine the clinical significance of the intracellular expression site(ICES)in gastric carcinogenesis. METHODS Specimens from 172 cases of gastric cancer,151 tissues from paraneoplastic gastric mucosa and 34 from noncancerous gastric mucosa were collected in Dalain,China.An immunohistochemical method was used to determine the expression of the hMSH2,hMLH1 proteins and their ICES in the gastric mucosas. RESULTS The rate of hMSH2 expression in gastric cancers,paraneoplastic gastric mucosas and noncancerous gastric mucosas were respectively 69.8%,49.7%and 32.4%.The rate was significantly higher in gastric cancer compared to the latter two groups(P=0.000),but there was no obvious difference in the expression between the two latter groups(P=0.067). The hMLH1 protein expression rates were respectively 73.3%,57.6%and 41.2%in the above three groups.The expression was significantly higher in the gastric cancer group compared to the two latter groups(P=0.000),while there was no significant difference between the latter groups(P=0.082). There was no obvious correlation between the hMSH2 and hMLH1 protein expression rates and related factors,such as gender,age and differentiated level of gastric cancer etc.The cell-nuclear expression of the hMSH2 protein was respectively 70.0%,58.7%and 36.4%in the gastric cancer,paraneoplastic gastric mucosa and noncancerous gastric mucosa groups.The cytoplasmic expression rates were 30.0%,41.3%and 63.6%in the three groups. The cell-nuclear expression rate of the hMSH2 protein gradually decreased in the gastric mucosas in the fol owing order:cancer,paraneoplastic and noncancerous but cytoplasmic expression only increased slightly in these groups(r=0.161,P=0.020).There was no significant difference in the ICES of the hMLH1 protein among the three different gastric mucosas(P=0.659). CONCLUSION Simultaneous determination of the expression and ICES of the mismatch repair proteins hMSH2 and hMLH1 in the gastric mucosa may be helpful in detecting early gastric cancer.     

Differential expression of p53, p21waf1/cip1 and hdm2 dependent on DNA damage in Bloom's syndrome fibroblasts

The Bloom's syndrome gene, BLM, encodes a protein which bears homology to the RecQ helicases. It is believed to be involved in DNA replication and has been implicated in the maintenance of genomic stability. To investigate whether BLM was involved in cellular responses to DNA damage Bloom's syndrome fibroblasts were treated with either UV or ionizing radiation and the levels of p53 and two of its down stream effectors, p21waf1/cip1 and hdm2, were determined by western blot analysis. Following 20 J/m2 UVC-radiation we observed that the maximal accumulation of p21waf1/cip1 and hdm2 proteins preceded that of p53 in both a normal diploid fibroblast cell strain (GM0038) and in two Bloom's syndrome cell strains. Furthermore, the Bloom's syndrome cells demonstrated a delayed and prolonged accumulation of all three proteins and a delayed recovery of the protein levels back to pre-damage levels compared with the normal cell strain. Conversely, normal and Bloom's syndrome cell response following 2.5 Gy of ionizing radiation was quite similar for p21waf1/cip1 and hdm2, but differed significantly for p53. Maximum accumulation of p53 occurred within 2 h of damage and preceded that of p21waf1/cip1 and hdm2. These results suggest that the BLM protein may play a role in the detection of certain types of DNA damage and in the cellular response to that damage.      

The p21(cip1/waf1) cyclin-dependent kinase inhibitor enhances the cytotoxic effect of cisplatin in human ovarian carcinoma cells

The seriousness of ovarian cancer, which is related to the observed link between recurrency and cell cycle control defect, prompted us to explore the effect of ectopic expression of the cdk inhibitor p21(cip1/waf1) on ovarian carcinoma chemosensitivity. The transfection of p21(cip1/waf1) cDNA into SKOV3 and OVCAR3 cells led to reduction of tumor cell growth, enhanced susceptibility to cisplatin-induced apoptosis, and abolition of recurrency after cisplatin exposure. p21(cip1/waf1) gene transfer allowed a marked reduction of the cisplatin concentration needed to erradicate the tumor cell population. These results suggest exploring the possible use of p21(cip1/waf1) as an adjunctive to conventional chemotherapy.     

骨肉瘤p21 ras蛋白、p21 wafl/cip1蛋白、PCNA与AgNOR的表达及其临床意义

目的探讨骨肉瘤组织中p21ras蛋白、p21wafl/cip1蛋白、PCNA与AgNOR的表达及其临床意义.方法应用免疫组化方法和组织化学方法检测45例骨肉瘤病人的骨肉瘤组织、20例骨软骨瘤病人的骨软骨瘤组织和20例正常骨组织中p21ras蛋白、p21wafl/cipl蛋白、PCNA与AgNOR的表达情况,对有关临床病理指标综合分析.结果45例骨肉瘤组织中p21ras蛋白、p21wafl/cipl蛋白和PCNA的阳性表达率分别为86.7%、13.3%和100%,AgNOR计数为9.63±2.47,阳性表达率与AgNOR计数均高于骨软骨瘤和正常骨组织;p21ras蛋白的表达与PCNA的表达存在平行关系;AgNOR计数与PCNA的表达呈正相关;四者的表达与骨肉瘤有关临床病理指标之间存在一定的关系.结论检测p21ras蛋白、p21waf1/cip1蛋白、PCNA与AgNOR为骨肉瘤恶性程度和预后的评估提供了重要的辅助参考指标.