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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genome-wide DNA hypomethylation plays has an important role in genomic instability and colorectal carcinogenesis. However, the relationship between cellular DNA methylation level and patient outcome remains uncertain. Using 643 colon cancers in two independent prospective cohorts, we quantified DNA methylation in repetitive long interspersed nucleotide element-1 (LINE-1) elements using pyrosequencing, which is a good indicator of global DNA methylation level. We used Cox proportional hazard models to calculate hazard ratios (HRs) of colon cancer-specific and overall mortality, adjusting for patient and tumoral features, including CpG island methylator phenotype (CIMP). Statistical tests were two-sided. LINE-1 hypomethylation was linearly associated with a statistically significant increase in colon cancer-specific mortality (for a 30% decrease in LINE-1 methylation: multivariable HR = 2.37, 95% confidence interval [CI] = 1.42 to 3.94; P(trend) < .001) and overall mortality (multivariable HR = 1.85, 95% CI = 1.25 to 2.75; P(trend) = .002). The association was consistent across the two independent cohorts and strata of clinical and molecular characteristics, including sex, age, tumor location, stage, and CIMP, microsatellite instability, KRAS, BRAF, p53, and chromosomal instability status. In conclusion, tumoral LINE-1 hypomethylation is independently associated with shorter survival among colon cancer patients.
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PMID:A cohort study of tumoral LINE-1 hypomethylation and prognosis in colon cancer. 1903 68

Transitional cell tumors of the ovary include 2 distinct clinicopathologic categories: Brenner tumors and transitional cell carcinomas (TCCs). Their molecular genetic alterations have not been fully investigated. We have performed a clinicopathologic, immunohistochemical, and molecular genetic analysis of 19 transitional cell tumors including 13 Brenner tumors (5 benign, 7 borderline, and 1 malignant) and 6 TCCs. Immunoreactivity for epidermal growth factor receptor (EGFR), Ras, Cyclin D1, p16, Rb, and p53, as well as fluorescence in situ hybridization analysis for EGFR were assessed in all cases. Screening for mutations in K-Ras, B-Raf, CTNNB1, PIK3CA, and p53 genes was also performed. The mean patient age was 58 years (range, 32 to 85 y). Abdominal enlargement and pain were the usual complaints. Treatment was known in 14 patients: 10 had hysterectomy with bilateral salpingo-oophorectomy, which was accompanied by omentectomy in 7; and 4 had only unilateral or bilateral salpingo-oophorectomy, 1 with omentectomy. Four patients had brachytherapy. Six borderline Brenner tumors were stage IA and 1 stage IIA. The malignant Brenner tumor was stage IA. One TCC was stage IA, one IC, 2 IIIC and the stage was unknown in 2 cases. Follow-up information was available only in 5 of the nonbenign cases. Two patients who had borderline Brenner tumors were alive and well at 3 and 10.9 years. The patient who had a malignant Brenner tumor died of pulmonary thromboembolism shortly postoperatively, and 2 patients with TCCs died of tumor 1.8 and 13 years, postoperatively. Brenner tumors and TCCs differed mainly in the expression of EGFR, p16, and p53. Benign Brenner tumors showed a low immunoexpression for all markers. Borderline Brenner tumors failed to immunoreact for p16, Rb, and p53; and showed weak immunostaining for Cyclin D1, moderate for Ras, and strong for EGFR. The malignant Brenner tumor was also negative for p16, Rb, and p53, and strongly positive for Cyclin D1, Ras, and EGFR. In contrast, TCCs had p53 mutations with p53 and p16 protein overexpression and showed a negative immunoreaction for EGFR, Cyclin D1, and Ras. Our results suggest that Brenner tumors and TCCs follow different tumorigenic pathways, whereas borderline and malignant Brenner tumors are low-grade neoplasms with activation of the PI3K/AKT pathway through EGFR, TCCs are high-grade tumors that have p53 mutations and p16 and p53 protein overexpression.
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PMID:Transitional cell tumors of the ovary: a comparative clinicopathologic, immunohistochemical, and molecular genetic analysis of Brenner tumors and transitional cell carcinomas. 1903 64

The incidence of colorectal carcinoma has increased among patients <40 years of age for unclear reasons. In this study, we describe the clinical, pathologic, and molecular features of colorectal carcinomas that developed in young patients. We compiled a study group of 24 patients <40 years of age with colorectal carcinoma, and 45 patients > or =40 years of age served as controls. Cases were evaluated for clinical risk factors of malignancy and pathologic features predictive of outcome. The tumors were immunohistochemically stained for O6-methylguanine methyltransferase, MLH-1, MSH-2, MSH-6, beta-catenin, chemokine (C-X-C motif) receptor 4, epidermal growth factor receptor, TP53, p16, survivin, and alpha-methylacyl-CoA racemase; assessed for microsatellite instability and mutations in beta-catenin, APC, EGFR, PIK3CA, KRAS, and BRAF; evaluated for micro-RNA expression (miR-21, miR-20a, miR-183, miR-192, miR-145, miR-106a, miR-181b, and miR-203); and examined for evidence of human papillomavirus infection. One study patient each had ulcerative colitis and hereditary nonpolyposis colorectal cancer. Ninety-two percent of tumors from young patients occurred in the distal colon (P=0.006), particularly the rectum (58%, P=0.02), and 75% were stage III or IV. Tumors from young patients showed more frequent lymphovascular (81%, P=0.03) and/or venous (48%, P=0.003) invasion, an infiltrative growth pattern (81%, P=0.03), and alpha-methylacyl-CoA racemase expression (83%, P=0.02) compared with controls. Carcinomas in this group showed significantly increased expression of miR-21, miR-20a, miR-145, miR-181b, and miR-203 (P< or =0.005 for all comparisons with controls). These results indicate that early-onset carcinomas commonly show pathologic features associated with aggressive behavior. Posttranslational regulation of mRNA and subsequent protein expression may be particularly important to the development of colorectal carcinomas in young patients.
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PMID:Clinical, pathologic, and molecular features of early-onset colorectal carcinoma. 1904 96

Ovarian serous carcinoma (OSC) is the most common and lethal histologic type of ovarian epithelial malignancy. Mutations of TP53 and dysfunction of the Brca1 and/or Brca2 tumor-suppressor proteins have been implicated in the molecular pathogenesis of a large fraction of OSCs, but frequent somatic mutations in other well-established tumor-suppressor genes have not been identified. Using a genome-wide screen of DNA copy number alterations in 36 primary OSCs, we identified two tumors with apparent homozygous deletions of the NF1 gene. Subsequently, 18 ovarian carcinoma-derived cell lines and 41 primary OSCs were evaluated for NF1 alterations. Markedly reduced or absent expression of Nf1 protein was observed in 6 of the 18 cell lines, and using the protein truncation test and sequencing of cDNA and genomic DNA, NF1 mutations resulting in deletion of exons and/or aberrant splicing of NF1 transcripts were detected in 5 of the 6 cell lines with loss of NF1 expression. Similarly, NF1 alterations including homozygous deletions and splicing mutations were identified in 9 (22%) of 41 primary OSCs. As expected, tumors and cell lines with NF1 defects lacked mutations in KRAS or BRAF but showed Ras pathway activation based on immunohistochemical detection of phosphorylated MAPK (primary tumors) or increased levels of GTP-bound Ras (cell lines). The TP53 tumor-suppressor gene was mutated in all OSCs with documented NF1 mutation, suggesting that the pathways regulated by these two tumor-suppressor proteins often cooperate in the development of ovarian carcinomas with serous differentiation.
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PMID:Neurofibromin 1 (NF1) defects are common in human ovarian serous carcinomas and co-occur with TP53 mutations. 1904 15

JC virus has a transforming gene encoding JC virus T-antigen (JCVT). JCVT may inactivate wild-type p53, cause chromosomal instability (CIN), and stabilize beta-catenin. A link between JCVT and CpG island methylator phenotype (CIMP) has been suggested. However, no large-scale study has examined the relations of JCVT with molecular alterations, clinical outcome, or prognosis in colon cancer. We detected JCVT expression (by immunohistochemistry) in 271 (35%) of 766 colorectal cancers. We quantified DNA methylation in eight CIMP-specific promoters (CACNA1G, CDKN2A, CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1) and eight other loci (CHFR, HIC1, IGFBP3, MGMT, MINT1, MINT31, p14, WRN) by MethyLight. We examined loss of heterozygosity in 2p, 5q, 17q, and 18q. JCVT was significantly associated with p53 expression (P < .0001), p21 loss (P < .0001), CIN (>/=2 chromosomal segments with LOH; P < .0001), nuclear beta-catenin (P = .006), LINE-1 hypomethylation (P = .002), and inversely with CIMP-high (P = .0005) and microsatellite instability (MSI) (P < .0001), but not with PIK3CA mutation. In multivariate logistic regression analysis, the associations of JCVT with p53 [adjusted odds ratio (OR), 8.45; P < .0001], CIN (adjusted OR, 2.53; P = .003), cyclin D1 (adjusted OR, 1.57; P = .02), LINE-1 hypomethylation (adjusted OR, 1.97 for a 30% decline as a unit; P = .03), BRAF mutation (adjusted OR, 2.20; P = .04), and family history of colorectal cancer (adjusted OR, 0.64; P = .04) remained statistically significant. However, JCVT was no longer significantly associated with CIMP, MSI, beta-catenin, or cyclooxygenase-2 expression in multivariate analysis. JCVT was unrelated with patient survival. In conclusion, JCVT expression in colorectal cancer is independently associated with p53 expression and CIN, which may lead to uncontrolled cell proliferation.
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PMID:JC virus T-antigen in colorectal cancer is associated with p53 expression and chromosomal instability, independent of CpG island methylator phenotype. 1910 35

The classification of colorectal cancer (CRC) by microsatellite instability (MSI) status is important for effective clinical management. In fact, microsatellite instability-high (MSI-H) cancer has distinctive clinicopathological and molecular features. However, microsatellite instability-low (MSI-L) cancer is not clearly defined. The objective of this study was to further clarify the characteristics of MSI-L CRC. A consecutive series of 940 primary CRCs were subdivided into three groups according to the level of MSI and analyzed the clinicopathological features and genetic changes in the KRAS, BRAF and p53 mutation and the loss of heterozygosity (LOH) of adenomatous polyposis coli (APC) gene and methylation status of the O(6)-methylguanine-DNA methyltransferase (MGMT) and MLH1 promoter. Of the 940 CRCs, 5.9% were MSI-H, 7.1% were MSI-L and 87% were microsatellite stable (MSS). KRAS and BRAF mutations were detected in 39.4 and 4.6% of the CRCs, respectively. The frequency of KRAS mutations in MSI-H, MSI-L and MSS cancer was 30, 48 and 39%, respectively. The proportion of KRAS mutations in MSI-L cancer increased from 16 to 63% accompanying the progression from Dukes' A to Dukes' B. While the LOH of D5S346, which is located near the APC gene, and p53 mutation was observed in 75 and 67% of MSI-L CRC at Dukes' A, respectively. These results indicated that the LOH of APC and p53 mutation has already occurred by the Dukes' A lake 'suppressor pathway' but not the KRAS mutation in MSI-L CRCs. The genes involving MSI-L carcinogenesis are similar to MSS but the timing and frequency of the KRAS mutation is different.
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PMID:Microsatellite instability-low colorectal cancer acquires a KRAS mutation during the progression from Dukes' A to Dukes' B. 1914 61

Despite rapid advances in understanding ovarian cancer etiology, epithelial ovarian cancer remains the most lethal form of gynecologic cancers in the United States. The four morphologically-defined epithelial ovarian cancer subtypes-serous, endometrioid, mucinous, and clear cell carcinomas--are generally believed to originate from ovarian epithelial cells. Although it remains unclear how this single cell layer gives rise to morphologically distinct cancers, it has been suggested that early genetic events may direct the differentiation of ovarian epithelial cells. A number of genetic alterations are frequently encountered during ovarian tumorigenesis, including oncogenic activities of KRAS, BRAF and AKT, and silencing mutations of TP53, RB and PTEN. However, knowledge about how these genetic elements are coordinated during ovarian cancer initiation and progression is very limited. The establishment of cell-culture systems and rodent-based models has made big strides towards a better understanding of the genetic bases of human epithelial ovarian tumorigenesis. More importantly, the rise of genetically-engineered rodent and human models, particularly in the past five years, has provided key insight in the role of specific genes during ovarian tumorigenesis. In this review, we offer a comprehensive coverage of currently-available in vitro and in vivo models of human epithelial ovarian cancer, focusing on latest updates of genetically-modified rodent and human models and the valuable information conveyed by them.
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PMID:Epithelial ovarian cancer: focus on genetics and animal models. 1922 85

Decitabine, an epigenetic modifier that reactivates genes otherwise suppressed by DNA promoter methylation, is effective for some, but not all cancer patients, especially those with solid tumors. It is commonly recognized that to overcome resistance and improve outcome, treatment should be guided by tumor biology, which includes genotype, epigenotype, and gene expression profile. We therefore took an integrative approach to better understand melanoma cell response to clinically relevant dose of decitabine and identify complementary targets for combined therapy. We employed eight different melanoma cell strains, determined their growth, apoptotic and DNA damage responses to increasing doses of decitabine, and chose a low, clinically relevant drug dose to perform whole-genome differential gene expression, bioinformatic analysis, and protein validation studies. The data ruled out the DNA damage response, demonstrated the involvement of p21(Cip1) in a p53-independent manner, identified the TGFbeta pathway genes CLU and TGFBI as markers of sensitivity to decitabine and revealed an effect on histone modification as part of decitabine-induced gene expression. Mutation analysis and knockdown by siRNA implicated activated beta-catenin/MITF, but not BRAF, NRAS or PTEN mutations as a source for resistance. The importance of protein stability predicted from the results was validated by the synergistic effect of Bortezomib, a proteasome inhibitor, in enhancing the growth arrest of decitabine in otherwise resistant melanoma cells. Our integrative analysis show that improved therapy can be achieved by comprehensive analysis of cancer cells, identified biomarkers for patient's selection and monitoring response, as well as targets for improved combination therapy.
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PMID:Integrative analysis of epigenetic modulation in melanoma cell response to decitabine: clinical implications. 1923 9

The BRAFV600E mutation is common in human melanoma. This mutation enhances IkappaB kinase (IKK)/nuclear factor-kappaB (NF-kappaB) and extracellular signal-regulated kinase/activator protein signaling cascades. In this study, we evaluated the efficacy of targeting either B-Raf or IKKbeta in combination with the DNA alkylating agent temozolomide for treatment of advanced metastatic melanoma. Xenografts of Hs294T human metastatic melanoma cells exhibiting the BRAFV600E mutation were treated with inhibitors of IKKbeta (BMS-345541), B-Raf (BAY 54-9085), and/or temozolomide. Drug response was mechanistically analyzed in vitro and in vivo. In this study, we determined that the antitumor activity of all three drugs depends on inhibition of NF-kappaB. BMS-345541 inhibits IKKbeta-mediated phosphorylation of IkappaBalpha and thus blocks the nuclear localization of NF-kappaB, whereas BAY 54-9085 inhibits activation of NF-kappaB through a mechanism that does not involve stabilization of IkappaBalpha. Moreover, BMS-345541, but not BAY 54-9085, activates the death pathways of p53 and c-Jun-NH2-kinase, contributing to the killing of melanoma cells. Temozolomide inhibits both NF-kappaB and extracellular signal-regulated kinase activity, conferring effective in vivo antitumor activity. Thus, temozolomide, but not BAY 54-9085, has a synergistic in vivo antitumor effect with BMS-345541. We conclude that the efficacy of antimelanoma therapy depends on inhibition of expression of antiapoptotic genes transcriptionally regulated by NF-kappaB. In contrast, drug targeting of the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway alone in melanoma cells is ineffective for melanoma therapy in cases where NF-kappaB is not also targeted.
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PMID:Molecular determinants of melanoma malignancy: selecting targets for improved efficacy of chemotherapy. 1927 65

Ovarian clear cell carcinoma (CCC) is one of the most malignant types of ovarian carcinomas, particularly at advanced stages. Unlike the more common type of ovarian cancer, high-grade serous carcinoma, ovarian CCC is often resistant to platinum-based chemotherapy, and therefore an effective treatment for this tumor type at advanced stages is urgently needed. In this study, we analyzed 97 ovarian CCCs for sequence mutations in KRAS, BRAF, PIK3CA, TP53, PTEN, and CTNNB1 as these mutations frequently occur in other major types of ovarian carcinomas. The samples included 18 CCCs for which affinity-purified tumor cells from fresh specimens were available, 69 microdissected tumors from paraffin tissues, and 10 tumor cell lines. Sequence mutations of PIK3CA, TP53, KRAS, PTEN, CTNNB1, and BRAF occurred in 33%, 15%, 7%, 5%, 3%, and 1% of CCC cases, respectively. Sequence analysis of PIK3CA in 28 affinity-purified CCCs and CCC cell lines showed a mutation frequency of 46%. Samples with PIK3CA mutations showed intense phosphorylated AKT immunoreactivity. These findings demonstrate that ovarian CCCs have a high frequency of activating PIK3CA mutations. We therefore suggest that the use of PIK3CA-targeting drugs may offer a more effective therapeutic approach compared with current chemotherapeutic agents for patients with advanced-stage and recurrent CCC.
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PMID:Frequent activating mutations of PIK3CA in ovarian clear cell carcinoma. 1934 52


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