RAS-positive thyroid nodules.

PURPOSE OF REVIEW: The current review focuses on the uncertainty regarding the management of rat sarcoma viral oncogene homolog RAS-positive thyroid nodules. The application of oncogene testing has been heralded for improving risk assessment for indeterminate cytology thyroid nodules and has grown in clinical use. RAS mutations are historically considered oncogenic. However, RAS mutation detection in thyroid nodules has proven problematic, as these mutations are found in benign and malignant lesions. RECENT FINDINGS: RAS-positive thyroid nodules frequently have indeterminate cytology and a finding of a positive RAS mutation identifies a significant number of benign lesions as well as thyroid cancers. Long-term follow-up of RAS-positive nodules with benign cytology shows an indolent course not consistent with eventual malignant transformation. Many RAS-positive nodules previously diagnosed as follicular variant of papillary thyroid carcinoma now will be reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features, indicating a more indolent nature of these RAS-positive lesions. SUMMARY: Recent findings have underscored that diagnosis of a RAS-positive thyroid nodule is not synonymous with thyroid malignancy. The ideal clinical and surgical management of these nodules remains challenging.

Down-regulation of K-ras and H-ras in human brain gliomas.

Ras genes, a class of nucleotide-binding proteins that regulate normal and transformed cell growth, have been scarcely investigated in human brain tumours. We evaluated the mutational, mRNA and protein expression profile of the ras genes in 21 glioblastomas multiforme (grade IV), four fibrillary astrocytoma (grade II), four anaplastic astrocytoma (grade III) and 15 normal specimens. K-, H- and N-ras transcript levels were determined by real-time RT-PCR and mutational status by PCR-restriction fragment length polymorphism (RFLP) and direct sequencing. p21 protein was evaluated by Western blot analysis. Two K-ras mutations were found in codons 16 and 26 in one pathological and one normal sample, respectively. Glioblastoma multiforme cases exhibited significantly lower K- and H-ras mRNA levels compared to controls (P < 10(-4)). K- and H-ras mRNA down-regulation was not associated with patient outcome or survival. K-ras was positively correlated with H-ras in glioblastomas (P = 0.005), but not in normal specimens. p21 protein was absent in all samples. Our findings provide evidence of K- and H-ras involvement in brain malignant transformation through transcriptional down-regulation, while N-ras seems to contribute less to brain carcinogenesis.

Downregulation of Ras C-terminal processing by JNK inhibition.

After translation, Ras proteins undergo a series of modifications at their C-termini. This post-translational C-terminal processing is essential for Ras to become functional, but it remains unknown whether and how Ras C-terminal processing is regulated. Here we show that the C-terminal processing and subsequent plasma membrane localization of H-Ras as well as the activation of the downstream signaling pathways by H-Ras are prevented by JNK inhibition. Conversely, JNK activation by ultraviolet irradiation resulted in promotion of C-terminal processing of H-Ras. Furthermore, increased cell density promoted C-terminal processing of H-Ras most likely through an autocrine/paracrine mechanism, which was also blocked under JNK-inhibited condition. Ras C-terminal processing was sensitive to JNK inhibition in the case of H- and N-Ras but not K-Ras, and in a variety of cell types. Thus, our results suggest for the first time that Ras C-terminal processing is a regulated mechanism in which JNK is involved.

Brain cancer stem-like cell genesis from p53-deficient mouse astrocytes by oncogenic Ras.

Here, we show that H-ras(V12) causes the p53-knockout mouse astrocytes (p53-/- astrocytes) to be transformed into brain cancer stem-like cells. H-ras(V12) triggers the p53-/- astrocytes to express a Nestin and a Cd133, which are expressed in normal and cancer neural stem cells. H-ras(V12) also induces the formation of a single cell-derived neurosphere under neural stem cell culture conditions. Furthermore, H-ras(V12)-overexpressing p53-/- astrocytes (p53-/-ast-H-ras(V12)) possess an in vitro self-renewal capacity, and are aberrantly differentiated into Tuj1-positve neurons both in vitro and in vivo. Amongst a variety of Ras-mediated canonical signaling pathways, we demonstrated that the MEK/ERK signaling pathway is responsible for neurosphere formation in p53-deficient astrocytes, whereas the PI3K/AKT signaling pathway is involved in oncogenic transformation in these cells. These findings suggest that the activation of Ras signaling pathways promotes the generation of brain cancer stem-like cells from p53-deficient mouse astrocytes by changing cell fate and transforming cell properties.

Gastrointestinal stromal tumors express ras oncogene: a potential role for diagnosis and treatment.

BACKGROUND: Gastrointestinal stromal tumors (GISTs) constitute the largest category of nonepithelial neoplasms of the gastrointestinal tract. Histologically, they have a spindle cell appearance but stain by immunohistochemistry for the proto-oncogene, c-kit (CD117). There is some evidence that phosphorylation of these receptors leads to a cascade that may activate the ras/mitogen-activated protein kinase pathway, which may, in turn, allow other oncogenes to become active. HYPOTHESIS: Immunohistochemical staining pattern of GISTs will aid in their differentiation from other spindle cell tumors and predict clinical outcome in patients. DESIGN AND SETTING: Retrospective review of patient records and paraffin block specimens of spindle cell tumors. PATIENTS: We have identified 65 patients with spindle cell tumors of the gastrointestinal tract at our institution in the past 10 years. Tumors were diagnosed by their morphology as leiomyomas, leiomyoblastomas, or leiomyosarcomas. MAIN OUTCOME MEASURES: CD117 and ras p21 were stained by immunohistochemistry on formalin-fixed, paraffin-embedded sections of normal and tumor tissues. RESULTS: Of the 65 patients, there were 23 patients diagnosed as having GIST confirmed by CD117 expression and 42 patients without GIST. Gastrointestinal stromal tumor samples of 17 (77%) of 22 patients stained positive for ras protein compared with 0 of 27 patients with leiomyomas (P<.001). CONCLUSIONS: To our knowledge, this study is the first to demonstrate that GISTs stain positive for ras p21. This molecular trait may be a useful diagnostic tool in addition to the c-kit (CD117) to separate GISTs from leiomyomas and leiomyosarcomas. In the future, ras inhibitors may potentially be a therapeutic to treat GISTs.

Canine biphasic synovial sarcoma: case report and immunohistochemical characterization.

The clinical, radiological and pathologic features of a biphasic synovial sarcoma in the left elbow joint of a two-year-old male Rottweiler are presented. The tumor showed positive immunoreactivity for vimentin, Epithelial Membrane Antigen (EMA), p53 and PCNA, while it was negative for the cytokeratin used, S-100, Rb and p21. Immunohistochemistry for EMA allowed the identification of epithelioid components of synovial sarcoma, and may, therefore, contribute in establishing a diagnosis of biphasic synovial sarcoma. Intratumoral variation in PCNA immunoreactivity was minimal, indicating that the various tumor components proliferate at more or less similar rates. Overall, the characterized immunohistochemical profile for canine synovial sarcoma, not defined previously, may provide clues to the histogenesis of the phenotypically mesenchymal and epithelial elements of the tumor, and may be of value in the differential diagnosis of challenging cases, decreasing the risk of under- and mis-diagnosis. Although more cases need to be studied to determine whether there is a consistent pattern of immunostaining in canine synovial sarcoma, its potential significance is discussed in relation to the histogenesis, molecular pathology and differential diagnosis of canine synovial sarcoma.

Canine biphasic synovial sarcoma: case report and immunohistochemical characterization

The clinical, radiological and pathologic features of a biphasic synovial sarcoma in the left elbow joint of a two-year-old male Rottweiler are presented. The tumor showed positive immunoreactivity for vimentin, Epithelial Membrane Antigen (EMA), p53 and PCNA, while it was negative for the cytokeratin used, S-100, Rb and p21. Immunohistochemistry for EMA allowed the identification of epithelioid components of synovial sarcoma, and may, therefore, contribute in establishing a diagnosis of biphasic synovial sarcoma. Intratumoral variation in PCNA immunoreactivity was minimal, indicating that the various tumor components proliferate at more or less similar rates. Overall, the characterized immunohistochemical profile for canine synovial sarcoma, not defined previously, may provide clues to the histogenesis of the phenotypically mesenchymal and epithelial elements of the tumor, and may be of value in the differential diagnosis of challenging cases, decreasing the risk of under- and mis-diagnosis. Although more cases need to be studied to determine whether there is a consistent pattern of immunostaining in canine synovial sarcoma, its potential significance is discussed in relation to the histogenesis, molecular pathology and differential diagnosis of canine synovial sarcoma.

Immunohistochemical and mutational analyses of beta-catenin, Ki-ras, and p53 in two subtypes of colorectal mucinous carcinoma.

PURPOSE: The adenoma-carcinoma sequence theory is accepted in carcinogenesis of colorectal carcinoma. To elucidate the nature and genetic alterations in colorectal mucinous carcinoma (MC), we analyzed clinical and pathological characteristics of colorectal MC and nonmucinous carcinoma (NMC), and, furthermore, we compared the prognoses and the statuses of the Wnt signaling pathway, Ki-ras, and p53 in these two subtypes. EXPERIMENTAL DESIGN: Samples of colorectal MC obtained by surgical resections from 41 patients during the period from 1980 to 1999 were classified into fixed (FIX) type and floating (FLO) type (22 and 19 cases, respectively). The statuses of the Wnt signaling pathway and p53 protein were estimated by immunohistochemistry of beta-catenin and p53 proteins, respectively. The mutations in the Ki-ras gene were examined by direct sequencing. RESULTS: The prognosis of colorectal MC was poorer than that of NMC at both stage II and stage III (P = 0.0037 and <0.0001, respectively). The survival rate of patients with the FLO type of MC was lower than that of patients with the FIX type (P = 0.021). Although the results of immunohistochemistry of beta-catenin and mutational analysis of the Ki-ras gene in the two subtypes were not significantly different; the rate of positive nuclear staining of p53 was lower in the FLO type than in the FIX type (P = 0.04). CONCLUSIONS: Colorectal MC, particularly the FLO type, has a more aggressive nature than does colorectal NMC. The FLO type of colorectal MC may develop through different mechanisms from those through which NMC and the FIX type develop.

Immunocytochemical detection of p21ras, Raf-1, ERK1/MAP kinase and PKC isoforms in a 20-methylcholanthrene-induced transformed murine embryonal fibroblast cells in culture.

An immunocytochemical study using antibodies against p21ras, Raf-1, MAP kinase/ERK1 and PKCalpha, beta, gamma, delta, epsilon, zeta, isoforms were performed on a 20-methylcholanthrene-induced transformed murine embryonal fibroblast cells in both in vitro and in vivo growth conditions. Altered expression of p21ras, Raf-1, MAP kinase in this particular cell line strongly supported the previous findings of the activation of one component of signal transduction under the influence of the other in the MAP kinase cascade of signal transduction during neoplastic transformation and which also seemed to be involved in CNCI-PM-20 cell line. The altered expression of PKCalpha, beta, and delta was thought to be an epigenetic event occurring under the indirect influence of other changes in these cells. Host physiology and metabolism did not have much impact on the expression of these gene products after biological incubation of these cells in syngenic host.

p21 and p53 Immunostaining and survival following systemic chemotherapy for urothelial cancer.

INTRODUCTION: Induction of apoptosis and regulation of cell cycle checkpoints are important mechanisms of chemotherapy-induced cell death. The intact p53 tumor suppressor gene is required for efficient activation of apoptosis. The WAF1/p21 gene is transcriptionally activated by p53 and mediates p53-dependent G1 arrest following DNA damage. Therefore, p53 and p21 expression might be related to urothelial tumor response to cytotoxic therapy. METHODS: In a retrospective study, archival tumor specimens from 60 patients treated with cisplatinum-based systemic chemotherapy for locally advanced and/or metastatic urothelial cancer were immunohistochemically stained for p53 and p21. Response to chemotherapy and overall survival were correlated with the results of immunohistochemistry. RESULTS: Thirty-five tumors (58%) of the 60 specimens showed p53 accumulation, and 25 (42%) expressed detectable p21. No association between p53 accumulation and expression of p21 was observed. Correlation with complete and partial remissions following inductive chemotherapy (n = 39) demonstrated that patients with intact p53 responded significantly better (70 vs. 31%, p < 0.05). However, no difference in overall survival was observed with regard to p53 immunostaining (median 12 and 17 months for p53-positive and p53-negative tumors, respectively). The p21 expression was related neither to response nor to overall survival following inductive chemotherapy. In patients receiving adjuvant chemotherapy after cystectomy (n = 21), the outcome was correlated with the immunohistochemistry results. While the survival times for p53-negative patients (60 months) and p53-positive patients (23 months) did not translate into a significant difference, the median overall survival for patients with p21-positive or p21-negative tumors (60 vs. 21 months) was significantly different (p < 0.005). CONCLUSIONS: The short survival of patients with metastatic bladder cancer may conceal putative differences between different prognostic groups in smaller trials. In contrast, p21 immunohistochemistry appears to be of prognostic value in patients receiving systemic adjuvant chemotherapy for locally advanced bladder cancer. The observations made in this retrospective study in a limited number of patients warrant further investigation on the correlation between G1/S checkpoint regulatory genes and adjuvant chemotherapy in larger prospective studies.

Diagnostic biochip array for fast and sensitive detection of K-ras mutations in stool.

BACKGROUND: Tumor cells that shed into stool are attractive targets for molecular screening and early detection of colon or pancreatic malignancies. We developed a diagnostic test to screen for 10 of the most common mutations of codons 12 and 13 of the K-ras gene by hybridization to a new biochip array. METHODS: DNA was isolated from 26 stool samples by column-based extraction from 9 cell lines. Peptide nucleic acid (PNA)-mediated PCR clamping was used for mutant-specific amplification. We used a biochip, consisting of a small plastic support with covalently immobilized 13mer oligonucleotides. The read out of the biochip was done by confocal time-resolved laser scanning. Hybridization, scanning, and data evaluation could be performed in <2 h. RESULTS: Approximately 80 ng of DNA was obtained from 200-mg stool samples. No inhibition of the PCR by remaining impurities from stool was observed. Mutation detection was possible in 1000-fold excess of wild-type sequence. Discrimination ratios between the mutations were >19 as demonstrated by hybridization with tumor cell line DNA. Stool samples (n = 26) were analyzed in parallel with PNA-PCR, restriction assay for K-ras codon 12 mutations, sequencing, and hybridization to the biochip. Nine mutations were found by hybridization, all confirmed by sequencing. PNA-PCR alone leads to an overestimation of mutations because suppression of the wild type is not effective enough with high concentrations of wild-type DNA. The restriction assay found only four mutations. CONCLUSIONS: The K-ras biochip is well suited for fast mutation detection from stool in colorectal cancer screening.

Role of pretherapeutic biomarkers in predicting postoperative radiotherapy response in patients with advanced squamous cell carcinoma.

PURPOSE: To assess the role of biomarker levels in predicting radiotherapy (RT) response in patients with squamous cell carcinoma of buccal mucosa treated with postoperative RT. MATERIALS AND METHODS: Thirty-one patients with squamous cell carcinoma of buccal mucosa who received postoperative RT were enrolled for the study. Glutathione S-transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD) and catalase activity were analysed from primary tumour and adjacent normal mucosa of the same patients before RT. p53 and p21ras were localized immunohistochemically. RESULTS: Enzyme activation was predicted by comparing the levels of these enzymes in tumour and adjacent normal mucosa. Deactivation of GST, activation of GR, SOD and catalase were associated with poor response to RT. p53 immunoreactivity was associated with failure to respond to RT. CONCLUSIONS: These markers may be useful in predicting treatment outcome in patients receiving postoperative RT, although this conclusion requires confirmation in a larger group of patients.

p53, p21 and metallothionein immunoreactivities in patients with malignant pleural mesothelioma: correlations with the epidemiological features and prognosis of mesotheliomas with environmental asbestos exposure.

The aim of this study is to investigate immunoreactivity for p53, p21 and metallothionein in diffuse malignant pleural mesothelioma (DMPM) and to determine the relationships between the age, sex, asbestos exposure time, survival of DMPM patients with environmental asbestos exposure and immunoreactivity to p53, p21 and metallothionein. Sixty-seven histopathologically-confirmed DMPMs, 38 of whom had environmental and 29 had occupational asbestos exposure, were included. The tumour tissue samples were immunostained with antibodies against p53, p21 and metallothionein. Epidemiological data and the survival times for the DMPM patients with environmental asbestos exposures were obtained from hospital records. Thirty-three per cent of the DMPMs were positive for p53, 35% for p21 and 52% for metallothionein. There was no statistical difference between the histological subtypes of DMPM in terms of immunoreactivity for p53, p21 and metallothionein. For p21 and metallothionein there was a statistically significant difference between the exposure characteristics: patients with environmental asbestos exposure had shown more immunopositivity. There were statistically significant differences between age groups and between asbestos exposure times for metallothionein, and between asbestos exposure times and p21. The patients with positive immunostaining had longer exposure times and were older than those having negative immunostaining. The differences between survival of the patients were not statistically significant in terms of the immunohistochemical results for p53, p21 and metallothionein.

Epithelial proliferation and ras p21 oncoprotein expression in rectal mucosa of patients with ulcerative colitis.

In ulcerative colitis (UC), epithelial proliferation plays a role in crypt repair and neoplastic evolution. Proliferative status is predominantly connoted in active disease, but not defined in remission. Histologically, remission is characterized by normalization of the picture or development of atrophy. Mutation of the ras oncogene is involved in intestinal carcinogenesis. Aim of this work was to assess the proliferative pattern of rectal epithelium in UC during disease activity and in remission and correlate it with ras oncoprotein p21. The study was performed retrospectively in rectal biopsies from four groups each of 10 patients: active ulcerative colitis (AUC), remission with a normal histology (RUC), remission with rectal atrophy (ARUC), and irritable bowel syndrome (C, control group). In all, immunohistostain was employed to evaluate the proliferation cell nuclear antigen labeling index (PCNA LI) and ras p21. Statistical analysis was performed by ANOVA and Student-Neumann-Keuls tests. PCNA LI was significantly higher in AUC and ARUC than in RUC and C. Positive cells were predominant in the lower zone of crypts in RUC and C, while a significant expression of PCNA was also observed in the upper areas in AUC and ARUC. Oncoprotein p21 was expressed on the apical surface of the epithelium in 3/10 AUC patients, in all 10 ARUC patients and in none of RUC and C. The persistently increased epithelial proliferation associated with ras p21 expression in ARUC may be due to the action of an abnormal, mutated ras gene that could play a role in UC-related tumorigenesis.

Effects of green tea on colonic aberrant crypt foci and proliferative indexes in rats.

The present study was designed to investigate the effect of green tea on 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci (ACF) formation in Wistar rats. Forty-five male weanling Wistar rats were randomly divided into three groups. Rats in Group 1 were injected with DMH (20 mg/kg s.c.) once a week for 10 weeks. Animals in Group 2 received 2% green tea water extract as the sole source of drinking fluid in addition to the same treatment used for Group 1. Group 3 was the negative control group. Animals were killed at the end of Week 16 after the first DMH treatment. ACF were formed in animals in their DMH-treated groups at the end of Week 16. Group 2 had fewer ACF than Group 1. Compared with the positive control group, proliferating cell nuclear antigen labeling index, silver-stained nucleolar organizer regions, and ras-p21 expression were significantly reduced in Group 2. It was concluded that green tea drinking inhibited ACF formation in rats, and such effects may be related to the suppression of cell proliferation in the intestinal crypts.

[The inhibitory effect of CLA on mice forestomach neoplasia induced by B(a)P].

OBJECTIVE: To study the inhibitory effect of CLA on the postinitiation phase of forestomach neoplasia formation induced by B(a)P and explore its possible mechanism of anticarcinogenesis. METHODS: Kunming mice were divided into five groups, i.e. salad oil control group, CLA control group, B(a)P group, B(a)P + high dose CLA group and B(a)P + low dose CLA group. The experimental period was 23 weeks, and the endpoints included cell proliferation, expression of Pan-ras P21 and some enzymes. RESULTS: Short term CLA treated significantly inhibited the forestomach neoplasia formation induced by B(a)P at postinitiation phase. The incidence of tumor in the groups of B(a)P, B(a)P + high dose CLA and B(a)P + low dose CLA was 100%, 60% and 69% respectively (P < 0.05). The possible mechanism of this anticarcinogenic effect may be related to the inhibition of cell proliferation and the induction of the activities of GSH-Px, GST and SOD, irrespective of the regulation of expression of Pan-ras P21. CONCLUSION: CLA is a promising chemopreventive agent, and its anticarcinogenic effect may involve its effects on the redox system.

Ras oncogenes and p53 tumor suppressor gene analysis in cardiac myxomas.

Although ras oncogenes and p53 tumor suppressor gene mutations are implicated in the development of several human tumors, little is known about their role in the pathogenesis of primary cardiac tumors. Paraffin-embedded tissue from 19 cardiac myxomas were investigated for the presence of ras oncogenes and p53 tumor suppressor gene abnormalities. Immunohistochemical analysis was used to identify the accumulation of p21-ras and p53 proteins. A polymerase chain reaction was used to amplify exons 1 and 2 of the ras genes and exons 5 to 8 of the p53 gene. The PCR products were analyzed by single strand conformation polymorphism analysis and by direct DNA sequencing. Three of 19 myxomas showed strong positive staining for the ras p21 protein. In contrast, nuclear p53 was not detectable in any of the myxomas. Among the ras p21 immunopositive myxomas, 2 were heterozygous for a missense point mutation of the K-ras, Gly 12Asp. Further screening of the remaining myxomas showed no mutation or even silent polymorphism in any exon of the ras and p53. The results suggest that although genetic alterations of ras oncogenes and p53 are uncommon events in cardiac myxomas, ras mutations may be involved in the pathogenesis of a subgroup of this type of tumor.

Mitogenic phospholipase D activity is restricted to caveolin-enriched membrane microdomains.

Phospholipase D (PLD) activity is elevated in response to the oncogenic stimulus of several signaling oncogenes. PLD activity is also elevated in response to peptide growth factors, indicating that PLD likely plays an important role in mitogenic signaling. Many proteins that mediate mitogenic signaling are localized in caveolin-enriched membrane microdomains (CEMMs). We report here that the elevated PLD activity in NIH 3T3 cells transformed by activated oncogenic forms of Src, Ras, and Raf is largely restricted to the CEMMs. Likewise, the PLD activity stimulated by epidermal growth factor is also restricted to the CEMMs. Although both PLD1 and PLD2 were found in CEMMs, neither was particularly enriched in the CEMMs of the transformed relative to the parental cells, indicating that it is the specific activity of PLD that is increased in the CEMMs. An apparent PLD substrate specificity in transformed cells for phosphatidylcholine lacking arachidonate acyl groups is also explained by the localization of activity in the CEMMs where [(3)H]arachidonate-labeled PC was excluded. These data indicate that mitogenic signals through PLD are initiated in CEMMs where many signaling molecules colocalize.