p53 Mutations are present in colorectal cancer with cytoplasmic p53 accumulation

Previous studies have shown that nuclear p53 over-expression is an indicator of p53 mutations whereas cytoplasmic p53 accumulation is related to wild-type p53 in several kinds of tumors. Cytoplasmic p53 accumulation has been demonstrated to be an independent prognostic factor in colorectal adenocarcinomas. The purpose was to examine whether mutations occur in cases with p53 accumulated in the cytoplasm and whether there are any differences in the frequency and characteristics of p53 mutations in different staining patterns. In the present study, we identified p53 mutations using PCR single-strand conformation polymorphism (SSCP) and DNA sequencing in 75 primary colorectal adenocarcinomas with different staining patterns (negative, nucleus, cytoplasm, nucleus and cytoplasm). The results show that the frequency and nature of mutations in tumors with cytoplasmic p53 accumulation were similar to those with nuclear p53 expression. However, the tumors with accumulation in both the nucleus and cytoplasm demonstrated a higher mutation rate. We suppose that the role of cytoplasmic p53 accumulation in predicting prognosis in patients with colorectal cancer may be dependent on both mutational and non-mutational mechanisms.     

DSC3 expression is regulated by p53, and methylation of DSC3 DNA is a prognostic marker in human colorectal cancer

Background:

Desmocollin 3 (DSC3), a member of the cadherin superfamily and integral component of desmosomes, is involved in carcinogenesis. However, the role of DSC3 in colorectal cancer (CRC) has not yet been established.

Methods:

Desmocollin 3 expression in CRC cell lines was analysed by RT–PCR and western blotting. Methylation status of DSC3 was examined by demethylation tests, methylation-specific PCR, and bisulphite sequencing (BS). The regulatory role of p53 was investigated by transfection.

Results:

Desmocollin 3 was downregulated in CRC cells at mRNA and protein levels. Desmocollin 3 expression was restored in five out of seven cell lines after 5-aza-2′-deoxycytidine (DAC) treatment. A heterogeneous methylation pattern was detected by BS in promoter region and exon 1 of DSC3. Methylation of DSC3 genomic sequences was found in 41% (41 out of 99) of primary CRC, being associated with poor prognosis (P=0.002). Transfection of p53 alone or in combination of DAC increased the DSC3 expression. Similarly, treatment with p53 inducer adriamycin alone or in combination with DAC enhanced DSC3 expression.

Conclusions:

DNA methylation contributes to downregulation of DSC3 in CRC cell lines. Methylation status of DSC3 DNA is a prognostic marker for CRC. P53 appears to have an important role in regulating DSC3 expression.     

结直肠癌血清P53抗体和组织P53蛋白的临床意义

目的 :检测结直肠癌患者血清p5 3抗体 (p5 3Ab)的敏感性和特异性 ,并了解其与肿瘤组织p5 3的相关性和临床意义。方法 :检测 2 0 0 2年 7月至 2 0 0 3年 12月的结直肠癌病例 178例。对照组为 4 0例正常健康志愿者。血清p5 3Ab检验采用酶联免疫法 :肿瘤组织p5 3蛋白表达测定应用免疫组化SP染色法。结果 :178例结直肠癌中33例血清p5 3Ab阳性 ,阳性率 18.5 4 % ;4 0例对照组检测阴性 ,特异性 10 0 %。血清p5 3Ab与患者的年龄、性别和肿瘤发生的部位无关 (P >0 .0 5 ) ;血清p5 3Ab阳性为Dukes’分期B期 (16 / 71,2 2 .5 4 % )、C期 (12 / 5 5 ,2 1.82 % )和D期(5 / 30 ,16 .6 2 % )。 10 3例肿瘤组织p5 3蛋白阳性 (5 7.87% ) ,75例阴性 (4 2 .13% ) ;血清p5 3Ab阳性者 6 9.7%组织表达阳性 ,30 .3%组织表达阴性 (P <0 .0 5 )。随访 6～ 2 4个月 ,肿瘤复发率在血清p5 3Ab阳性和阴性患者间无显著性差异 ;平均存活时间亦无统计学意义。结论 :研究表明血清p5 3Ab的产生伴有肿瘤组织p5 3蛋白的积聚 ;因为抗体检测的低敏感性 ,血清p5 3Ab不能作为术前的肿瘤指标 ;但由于它的高特异性 ,对今后的随访可能具有一定临床意义     

Immunohistochemical analysis of p53 in colorectal cancer regarding clinicopathological correlation and prognostic significance

The overexpression of the tumor suppressor gene p53 was investigated immunohistochemically in 144 cases of primary colorectal cancer and in 8 cases with cancer in the corresponding metastatic lymph nodes. Abnormalities in p53 expression were found in 36 cases (25%) of the 144 primary cancer cases. In addition, p53-positive tumors were found to metastasize frequently to the lymph nodes, as compared to p53-negative tumors (61.1% vs. 41.7%, P=0.0428). p53 staining was identical in 7 of 8 (87.5%) cases in primary and metastatic lesions. When the DNA content of the tumor was determined by flow cytometry, the DNA index (mean ± SD) was significantly higher in p53-positive tumors than in p53-negative tumors (1.57 ± 0.38 vs. 1.39 ± 0.37, P=0.012). Therefore, the immunohistochemical data of p53 in colorectal cancer may help in potentially predicting metastatic spread to the lymph nodes. © 1995 Wiley-Liss, Inc.     

Combination of p53 codon 72 polymorphism and inactive p53 mutation predicts chemosensitivity to 5‐fluorouracil in colorectal cancer

There are increasing reports showing the clinical significance of the p53 polymorphism status in terms of the response to chemotherapy. We investigated whether p53 polymorphism and mutation were associated with in vitro sensitivity to 5‐fluorouracil (5‐FU) in patients with colorectal cancer. Chemosensitivity to 5‐FU was evaluated by the collagen gel droplet embedded culture drug sensitivity test. 5‐FU sensitivity of tumor cells without inactive p53 mutation in the arginine/arginine (Arg/Arg) variant was significantly higher than that of tumor cells with or without inactive p53 mutation in other variants (p = 0.022), whereas the 5‐FU sensitivity of tumor cells with inactive p53 mutation in the Arg/Arg variant was significantly lower than that of tumor cells with or without inactive p53 mutation in other variants (p = 0.002). In the Arg/Arg variant, apoptotic cells induced by 5‐FU treatment in patients without inactive p53 mutation were more markedly increased than those in patients with inactive p53 mutation (p = 0.037). Bax and Bcl‐2 protein expressions in tumor tissue treated with 5‐FU were associated with both 5‐FU sensitivity and the apoptotic cell count. Our data show that the Arg/Arg genotype without inactive p53 mutation could be predictive of a more favorable response and the Arg/Arg genotype with inactive p53 mutation a less favorable response to chemotherapy using 5‐FU in CRC. The combination of the p53 codon 72 polymorphism and p53 mutation status is a potential predictive marker of sensitivity to 5‐FU in CRC.     

自噬相关基因Beclin-1与抑癌基因PTEN、p53在大肠癌中的表达和意义

目的:检测自噬相关基因Beclin-1与抑癌基因PTEN、p53在大肠正常黏膜、大肠腺瘤、大肠癌组织中的表达,探讨它们与大肠癌发生发展的相关性。方法:采用免疫组织化学SP法检测Beclin-1与PTEN、p53在15例大肠正常黏膜、30例腺瘤及65例大肠癌组织中的表达,结合临床病理因素进行分析。结果:Beclin-1在大肠癌组阳性表达率高于正常大肠黏膜组(P<0.001)与大肠癌组织学分化程度、Dukes分期及淋巴结转移无关。PTEN在大肠正常黏膜组中的表达高于大肠癌组(P=0.001),与大肠癌组织学分化程度、Dukes分期及淋巴结转移有关。p53在大肠正常黏膜、腺瘤及大肠癌组织中的表达逐渐增高(P<0.001)与大肠癌组织学分化程度、Dukes分期及淋巴结转移有关。经Spearman秩相关检验,Beclin-1蛋白与PTEN蛋白相关系数为-0.289,呈负相关表达;Beclin-1蛋白与p53蛋白相关系数为0.347,呈正相关表达。结论:Beclin-1、PTEN、p53在大肠癌中的异常表达与大肠癌的发生、发展密切相关。自噬可能与大肠癌的发生相关,自噬活性的上调与大肠癌发生有关。自噬相关基因Beclin-1与抑癌基因PTEN、p53在大肠癌的发生发展中起协调作用。同时检测对判断大肠癌的进展程度具有重要的意义。     

Growth dysregulation and p53 accumulation in human primary colorectal cancer.

p53 accumulation is common in colorectal cancer, but effects on growth homeostasis are unclear. In this study, DNA content, cell cycle phase fractions and DNA strand-breaks consistent with apoptosis were assessed by flow cytometry in 42 fresh primary colorectal tumours and matched normal mucosa. p53 accumulation was assessed in 37 fixed tumour sections, by immunohistochemistry. In normal mucosa, 10.3 +/- 6.6% (mean +/- s.d.) cells were in DNA synthesis phase while 28.7 +/- 17.9% showed apoptosis. A relationship suggestive of growth homeostasis, was observed between these parameters (r = 0.8; P < 0.05). In cancers, a greater number of cells were in DNA synthesis phase (15.6 +/- 12.9% tumour vs mucosa 10.3 +/- 6.6%; P < 0.02) while fewer showed apoptosis than normal mucosa (18.5 +/- 17.0% tumour vs mucosa 28.7 +/- 17.9%; P < 0.01). DNA synthesis and apoptosis fractions were unrelated in cancers, suggesting growth dysequilibrium. p53 accumulation was detected in 59% (22/37) tumours and was associated with reduced apoptosis compared to p53-negative tumours or mucosa (14.8 +/- 15% p53 accumulation vs 26.3 +/- 18% p53-negative; P < 0.05; vs 28.7 +/- 17.9% mucosa; P < 0.05). p53 accumulation was unrelated to DNA synthesis phase fractions. p53 accumulation is accompanied by reduced apoptosis which may accentuate growth dysequilibrium in colorectal cancer.     

RASSF10 suppresses colorectal cancer growth by activating P53 signaling and sensitizes colorectal cancer cell to docetaxel

RASSF10 has previously been reported to be frequently methylated in a number of malignancies. To understand the importance of RASSF10 inactivation in colorectal carcinogenesis, eight colorectal cancer cell lines, 89 cases of primary colorectal cancer and 5 cases of normal colorectal mucosa were examined. Methylation specific PCR, western blot, siRNA, gene expression array and xenograft mice were employed. The expression of RASSF10 was regulated by promoter regional methylation in colorectal cancer cells. RASSF10 was methylated in 60.7% (54/89) of primary colorectal cancers and was positively associated with tumor stage (p < 0.05) and metastasis (p < 0.05). Restoration of RASSF10 led to inhibition of colorectal cancer cell proliferation in vitro and in vivo and increased apoptosis. Gene expression arrays discovered RASSF10 inhibition of MDM2 expression as a mediator of these effects, which was confirmed with RT-PCR and western blot. RASSF10 was shown to activate P53 signaling in RKO and HCT116 cells after UV exposure, and sensitized these cells to docetaxel. In conclusion, our study demonstrates RASSF10 is frequently methylated in human colorectal cancer leading to loss of expression. RASSF10 normally suppresses human colorectal cancer growth by activating P53 signaling in colorectal cancer, and restored expression sensitizes colorectal cancer to docetaxel.     

p53 mutation is common in microsatellite stable, BRAF mutant colorectal cancers

The majority of "serrated pathway" colorectal cancers have mutation of the BRAF oncogene and display the CpG island methylator phenotype (CIMP). Half these cancers have microsatellite instability (MSI) and an excellent prognosis. In the absence of MSI (microsatellite stable, MSS), BRAF mutation has been associated with a particularly poor prognosis. "Traditional pathway" cancers are BRAF wild type. Mutation of p53 is common and this correlates with advanced stage. We therefore hypothesized that p53 mutation would be common in MSS/BRAF mutant colorectal cancer. One thousand and eighty-one colorectal cancers were screened for BRAF mutation to identify two BRAF mutant study groups (MSI: n = 77; MSS: n = 69) and a BRAF wild type control group (n = 101). These were screened for p53 mutation by high resolution melt analysis and classified for CIMP and MGMT methylation by quantitative methylation specific PCR. Molecular data were compared to patient age, gender, tumor location and stage. p53 was mutated significantly more frequently in MSS/BRAF mutant (28/69, 40.6%) compared to MSI/BRAF mutant cancers (13/77, 16.9%), but this mutation rate did not differ from MSS/BRAF wild type cancers (47/101, 46.5%)(p < 0.0001). CIMP was less common in MSS/BRAF mutant (26/47, 55.3%) compared to MSI/BRAF mutant cancers (41/54, 75.9%), but was more common than in MSS/BRAF wild type cancers (3/85, 3.5%) (p < 0.0001). MSS/BRAF mutant cancers were more commonly proximal (38/54, 70.3%), but were similar to MSS/BRAF wild type cancers in terms of patient age, gender distribution and stage at presentation. MSS/BRAF mutant cancers share molecular and clinical features of both the serrated and traditional pathways of colorectal tumorigenesis.     

Relaxed cell-cycle arrests and propagation of unrepaired chromosomal damage in cancer cell lines with wild-type p53

The role of the p53 protein in mediating G₁ and G₂ cell-cycle arrests after genotoxic insult has been clearly and reproducibly established in primary diploid fibroblasts, but data obtained from p53 wild-type (wt) cancer cell lines are inconsistent. Furthermore, a large proportion of human tumors have p53 wt genotypes but present genetic aberrations that may result from defective cell-cycle checkpoints. We therefore investigated the integrity of G₁/S and G₂/M cell-cycle arrests in p53 wt cancer cell lines. In the study presented here, we showed that in most cancer cells tested, G₁ arrest was relaxed or absent in comparison with arrest in normal diploid fibroblasts, despite seemingly normal p53 and p21 responses. Two cell lines (MCF7 and HCT116) were synchronized in G₀/G₁ by leucine starvation and subjected to genotoxic stress to determine more precisely the relative proportion of cells arresting in G₁ and G₂. Whereas the MCF7 cells showed consistent G₁ arrest, the HCT116 cells showed none at all. Furthermore, cell-cycle arrests in G₁ and G₂ in response to γ irradiation and bleomycin treatment were transient, as the cells resumed cycling after 48–72 h. The cells resuming proliferation suffered massive apoptosis, but a proportion of the cells were rescued and showed normal doubling times. These cells retained a p53 wt genotype but presented gross chromosomal aberrations in 15–20% of the analyzed metaphases. The aberrations were not clonal. These data show that p53 wt cancer cells have relaxed cell-cycle controls after genotoxic insult and tolerate unrepaired chromosomal damage, despite normal p53 function. Mol. Carcinog. 23:1–12, 1998. © 1998 Wiley-Liss, Inc.     

p53 Arg72Pro polymorphism and risk of colorectal adenoma and cancer

A single nucleotide polymorphism (SNP) at codon 72 of the p53 gene (Arg72Pro) alters the p53 protein structure and affects its activity. We investigated this SNP in relation to colorectal adenoma and cancer among men and women from case-control studies nested within the Nurses' Health Study, the Health Professionals Follow-up Study and the Physicians' Health Study. Among 856 colorectal adenoma cases and 1,184 controls, we observed a modest association with p53 Arg72Pro genotype (multivariate odds ratio (OR) = 1.25, 95% confidence interval (CI) = 1.04-1.50 for Arg/Pro and Pro/Pro vs. Arg/Arg). This association did not vary by colorectal site or by sex. Among 442 colorectal cancer cases and 904 controls, we observed no significant overall association between p53 Arg72Pro genotype and colorectal cancer (multivariate OR = 1.14, 95% CI = 0.90-1.45). However, when colorectal site and sex was accounted for, the Pro carrier genotypes compared to Arg/Arg were associated with an increased risk of proximal colon cancers in women (multivariate OR = 2.59, 95% CI = 1.49-4.52) though not with distal colon or rectal cancers, while among men the same genotypes were associated with an increased risk of distal colon cancers (multivariate OR = 2.09, 95% CI = 1.28-3.40) but not proximal colon or rectal cancers. Our results suggest that Arg72Pro may play a role in the early stages of colorectal neoplasia and possibly in progression to invasive disease, depending on site and sex.     

Relationship between apoptosis regulator proteins (bcl-2 and p53) and Gleason score in prostate cancer

Cellular proliferation programmed cell death (apoptosis) are associated with tumor growth in general, and prostate cancer growth in particular. The aim of this study was to examine the expression of the apoptosis regulating genes bcl-2 and p53 and Gleason score in core needle biopsy specimens of prostate cancer using immunohistochemistry. We studied bcl-2 and p53 expression in 12 cases of low grade (Gleason score 2-5), 12 cases of intermediate grade (Gleason score 6-7) and 8 cases of high grade (Gleason score 8-10) prostate cancer. Overexpression of bcl-2 was noted in 3 of 32 patients (9.32%). One of them was high grade; others were intermediate grades. Expression of p53 was observed in 3 of low grades; others were high grade. The statistical analysis of present data suggest that there is no significant relation between p53 and bcl-2 expression and Gleason score in prostate cancer.     

Expression of high p53 levels in colorectal cancer: a favourable prognostic factor.

The expression of p53 protein was examined in a series of 111 colorectal cancer adenocarcinomas with a long follow-up. A quantitative luminometric immunoassay (LIA) was used for the measurement of wild-type and mutant p53 protein in extracts from colorectal tumour cytosols, p53 being detected in 42% of the samples (range 0.0-52 ng (mg-1)). Using an arbitrary cut-off value of 2.7 ng mg(-1), 25% of the tumours were classified as manifesting high p53 levels. There was no association of p53 expression with patient age, sex, serum preoperative carcinoembryonic antigen (CEA) levels, tumour site and size, nodal status or TNM stage. Significant and independent correlation was found to exist between high p53 levels and prolonged disease-free survival (P = 0.05) at a median follow-up of 60 months. This survival advantage was most apparent among stage III cancer patients. The results from this study would suggest that expression of high p53 levels appear to be useful in selecting a group of colorectal cancer patients with a better prognosis.     

Thymidilate synthase and p53 primary tumour expression as predictive factors for advanced colorectal cancer patients

The purpose of this work was to analyse the ability of p53 and thymidilate synthase (TS) primary tumour expression to retrospectively predict clinical response to chemotherapy and long-term prognosis in patients with advanced colorectal cancers homogeneously treated by methotrexate (MTX)-modulated-5-fluorouracil (5-FU-FA). A total of 108 advanced colorectal cancer patients entered the present retrospective study. Immunohistochemical p53 (pAb 1801 mAb) and TS (TS106 mAb) expression on formalin-fixed paraffin-embedded primary tumour specimens was related to probability of clinical response to chemotherapy, time to progression and overall survival. p53 was expressed in 53/108 (49%) tumours, while 54/108 (50%) showed TS immunostaining. No relationship was demonstrated between p53 positivity and clinical response to chemotherapy (objective response (OR): 20% vs 23%, in p53+ and p53- cases respectively) or overall survival. Percent of OR was significantly higher in TS-negative with respect to TS-positive tumours (30% vs 15% respectively; P < 0.04); simultaneous analysis of TS and p53 indicated 7% OR for p53-positive/TS-positive tumours vs 46% for p53-positive/TS-negative tumours (P < 0.03). Logistic regression analysis confirmed a significant association between TS tumour status and clinical response to chemotherapy (hazard ratio (HR): 2.91; 95% confidence interval (CI) 8.34-1.01; two-sided P < 0.05). A multivariate analysis of overall survival showed that only a small number of metastatic sites was statistically relevant (HR 1.89; 95% CI 2.85-1.26; two-sided P < 0.03). Our study suggests that immunohistochemical expression of p53 and TS could assist the clinician in predicting response of colorectal cancer patients to modulated MTX-5-FU therapy.     

Role of p53 in the induction of cyclooxygenase-2 by cisplatin or paclitaxel in non-small cell lung cancer cell lines

Non-small cell lung Cancer (NSCLC) is extremely resistant to chemotherapeutic agents, such as cisplatin. High expression of the inflammatory enzyme Cyclooxygenase-2 (COX-2) has been shown to inhibit chemotherapy-induced apoptosis, but little is known about COX-2 regulation upon drug treatment. Recent data indicate the tumor suppressor protein p53 as an important regulator of COX-2. Therefore, TP53 status could change tumor sensitivity to chemotherapy through induction of the anti-apoptotic protein COX-2. The main objective of this work was to analyze the effect of chemotherapy on the expression of COX-2, according to TP53 status. We report herein that lung cancer cell lines expressing wild-type p53, when exposed to cisplatin treatment, induced COX-2 (mRNA and protein), with concurrent synthesis of prostaglandins (PGE₂). In contrast, COX-2 expression was not changed after cisplatin treatment of cells containing an inactive form of p53. Further, after silencing of wild-type p53 expressed in A549 cells by RNA interference, cisplatin was no longer able to induce COX-2 expression. Therefore, we suggest that induction of COX-2 by cisplatin in NSCLC cell lines is dependent on p53. For paclitaxel treatment, an increase in COX-2 mRNA expression was observed in H460 and A549 (wild-type p53 cell lines). Moreover, paclitaxel treatment increased COX-2 expression in ACC-LC-319 cell lines (p53 null), showing a p53-independent effect. These data may have therapeutic implications in the selection of patients and strategy for future COX-2 inhibition trials.     

Relationship of P-glycoprotein and p53 protein to chemosensitivity in colorectal cancer

Background Resistance of tumors to chemotherapeutic agents is a major problem in cancer treatment. Recent advances in molecular biology have shown a role for oncogenes in this resistance. Methods We determined the positive or negative expression of P-glycoprotein and mutant p53 protein by immunohistochemistry on 101 human colorectal cancer and correlated the expression of these proteins with the chemosensitivity of the tumors to various anticancer agents using the succinate dehydrogenase inhibition (SDI) test. Results Fifty-five (54.5%) of 101 tumors expressed P-glycoprotein and 53 (52.5%) expressed a mutant p53 protein. Thirty-seven of 55 tumors positive for P-glycoprotein also expressed a mutant p53 protein. The association between the coexpression of P-glycoprotein and p53 protein was statistically significant (P=0.001). Neither the expression of P-glycoprotein nor p53 protein affected the chemosensitivity of the tumor to doxorubicin hydrochloride, aclarubicin hydrochloride, pirarubicin, epirubicin hydrochloride, mitomycin C, 5-fluorouracil, cisplatin, carboplatin, or etoposide. However, a positive correlation was found between the control optical density and chemosensitivity in the P-glycoprotein or mutant p53 protein negative tumors. Oppositely, some P-glycoprotein or mutant p53 protein positive tumors showed low chemosensitivity in spite of their high control optical density. Conclusions A highly statistically significant coexpression of P-glycoprotein and mutant p53 protein was found in colorectal cancer. Furthermore, differences in cell growth between the tumor samples indicate the possibility that the expression of P-glycoprotein and mutant p53 protein in colorectal cancer tumors could be associated with chemoresistance.