Immortalization by truncated myc or ras genes and synergism between myc and ras genes in cell transformation

Human c-myc and normal or mutant T24 H-ras1 genes either linked to the regulatory sequences of the human metallothionein IIa gene or unlinked have been employed individually or in combination to transfect early passage Chinese hamster lung cells. Since the c-myc and H-ras1 genes are present in recombinant plasmids carrying the aminoglycoside phosphotransferase (aph), gene transfectants were selected in the presence of geneticin. A synergistic effect has been observed between myc and H-ras1 genes in measurement of both the number of geneticin resistant colonies obtained and the parameters of morphological transformation and anchorage independence. Out study also demonstrates the ability of truncated myc and ras genes to induce immortalization of hamster cells.     

ras癌基因在人乳腺肿瘤中的表达

应用P_(21)蛋白单克隆抗体,对25例人乳腺癌的免疫组织化学检测显示,在乳腺浸润性导管癌组织中,有高水平的P_(21)表达,阳性率高达92％,与Querzoli等报道一致。29伊4乳腺良性病变的检测结果显示,细胞内P_(21)表达水平的高低与细胞增殖状态相关。临床对比分析提示乳腺癌中P_(21)的表达水平与瘤体大小有关但不能反映病人的淋巴结转移状态。上述结果表明,ras癌基因表达产物P_(21)蛋白,是一个与细胞增殖相关,可反映组织增殖状态的细胞生物学因子。     

Elevated expression of the human ras oncogene family in premalignant and malignant tumours of the colorectum

Study of expression of ras-related oncogenes in human premalignant polyps and malignant tumours of the colorectum, as well as in normal colorectal mucosa, shows a significant elevation in the premalignant and malignant tissues as compared to their respective colorectal mucosa. These results suggest that activation of the ras oncogene family occurs in the development of colorectal tumours and that elevated expression at a premalignant stage may well be critical in the process of carcinogenesis but not in itself sufficient.     

Specific effects of ras oncogene expression on the growth and histogenesis of human epidermal keratinocytes

Little progress has been made in identifying specific regulatory pathways that might be affected in cells by a mutationally activated p21ras when its expression does not lead to complete transformation. We wished to determine whether a normal, diploid human epithelial cell in which activation of ras had occurred could be identified in culture and, furthermore, whether expression of a mutant p21ras in such an otherwise normal cell would result in abnormal histogenic behavior in vivo. Thus, we introduced the v-Ha-ras gene into an early passage culture of normal human epidermal keratinocytes via a defective retrovirus. We examined these genetically engineered cells for changes in growth and differentiation, both in culture and in the epithelium formed when cultures were grafted to the skin of nude mice. We have found that keratinocytes expressing p21v-ras are independent of epidermal growth factor (EGF)--a factor which is normally essential for progressive colony growth, but that they are otherwise indistinguishable in culture from normal cells. v-ras keratinocytes also secrete a factor possessing some specific biological activities of members of the fibroblast growth factor (FGF) family, but which is distinct from acidic and basic FGF. In short-term dermal grafts the v-ras cells form a non-invasive and normally differentiating epidermis. However, the cells express elevated levels of keratin 19, which is a characteristic of fetal epidermis and of premalignant lesions of some stratified squamous epithelia.     

Immunohistochemical study of the ras oncogene expression in human breast lesions

An immunohistochemical study of ras oncogene expression in human breast lesions was carried out using a monoclonal antibody, Y13 259, to the ras encoded p21 protein. A total of 75 cases of breast disease examined included: 33 simple and complex cystic disease; 22 simple and hyperplastic fibroadenomas; 18 ductal, lobular and mixed carcinomas and 2 in situ carcinomas. Most of the complex cystic disease, hyperplastic fibroadenomas and all types of carcinomas showed high p21 expression as indicated by staining intensity. These results suggest that elevated ras expression may play an important role in the development of some premalignant and malignant breast lesions.     

Immunohistochemical study of the ras oncogene expression in human bladder endoscopy specimens

We have used the monoclonal antibody Y13 259 to the ras oncogene p21 protein product in 42 endoscopy specimens from the bladder of 37 patients, in order to determine the ras oncogene expression in different conditions of the urothelium. The examined material included: 27 normal and hyperplastic or dysplastic mucosae and 13 papillomas and transitional cell carcinomas, graded according to Mostofi's classification. Our results showed the following: the normal urothelium sections tended to be negative, while the umbrella cells from the superficial layer always expressed a higher degree of positivity. The majority of the hyperplastic lesions and the papillomas were weakly positive or negative. In contrast, all the dysplastic lesions and the carcinomas of different grades were strongly positive. Our results suggest that elevated expression of ras oncogene may serve as an early marker in the pathogenesis of bladder lesions.     

Wilms' tumours: about tumour suppressor genes, an oncogene and a chameleon gene

Genes identified as being mutated in Wilms' tumour include TP53, a classic tumour suppressor gene (TSG); CTNNB1 (encoding β-catenin), a classic oncogene; WTX, which accumulating data indicate is a TSG; and WT1, which is inactivated in some Wilms' tumours, similar to a TSG. However, WT1 does not always conform to the TSG label, and some data indicate that WT1 enhances cell survival and proliferation, like an oncogene. Is WT1 a chameleon, functioning as either a TSG or an oncogene, depending on cellular context? Are these labels even appropriate for describing and understanding the function of WT1?     

The role of ras and myc oncogenes in human solid tumours and their relevance in diagnosis and prognosis (review)

Advances in the field of oncogenes have produced a tool to investigate the different stages in multistep carcinogenesis. The role of the ras and myc gene families have been extensively investigated in the progression of carcinogenesis in a range of human solid tumours. This review critically analyses the data available on the role of these oncogenes in the six most common cancers worldwide, (i.e. cancer of the stomach, lung, breast, colon, cervix, and mouth and pharynx). In certain cases the incidence of aberrant gene expression and genetic alterations of the ras and myc gene families have been shown to be important in the progression of these cancers and may be of use as prognostic indicators.     

Myc族癌基因与食管癌相关性的研究

目的　通过检测食管癌组织中myc族癌基因的扩增情况探讨myc族癌基因与食管癌发生、发展及预后的关系。方法　聚合酶链反应 (PCR)测定。结果　myc族癌基因的阳性扩增率 5 5 .0 % (11/2 0 )。其过表达与肿瘤分化程度、浸润范围、淋巴结转移、临床病理分期方面在统计学上有差异 (P <0 .0 5 ) ,而与病人年龄、肿瘤部位在统计学上无差异性 (P >0 .0 5 )。结论　myc族癌基因的过表达与食管癌的生物学行为有关。有可能为食管癌病人的防治及预后判定提供新的方法。     

Inhibition of interferon-gamma antiviral and antiproliferative activities by ras oncogene expression

In this study, we evaluated the effect of ras oncogene activation on cell response to interferons (IFNs). For this purpose, we treated NIH 3T3 murine fibroblasts transformed by transfection with K-, Ha-, or N-ras oncogenes, either mutated or amplified, for 24 hours with IFN-gamma or IFN-alpha. We evaluated cell response by measuring virus replication, [3H]thymidine incorporation, 2',5'-oligoadenylate synthetase activation, and class I antigen induction. Transformed cells were much less responsive to IFN-gamma antiviral and antiproliferative activities than normal NIH 3T3 cells. Similarly, the induction of 2',5'-oligoadenylate synthetase following IFN-gamma treatment was completely depressed in transformed cells. Only class I antigens, measured at the cell surface and mRNA levels, appeared partially inducible by IFN-gamma in ras-transformed cells. When the same cell lines were treated with IFN-alpha, we observed full response. Because both normal and ras-transformed NIH 3T3 cells were able to bind [125I]IFN-gamma with comparable Kd values (8.3 X 10(-11) M vs. 3 X 10(-11) M, respectively), these findings suggest that ras oncogenes may differentially impair IFN-gamma activities by affecting activation of IFN-inducible genes downstream from the receptor binding event.     

Differential expression of myc, max and RB1 genes in human gliomas and glioma cell lines.

Deregulated expression of myc proto-oncogenes is implicated in several human neoplasias. We analysed the expression of c-myc, N-myc, L-myc, max and RB1 mRNAs in a panel of human gliomas and glioma cell lines and compared the findings with normal neural cells. The max and RB1 genes were included in the study because their protein products can interact with the Myc proteins, being thus putative modulators of Myc activity. Several gliomas contained c/L-myc mRNAs at levels higher than those in fetal brain, L-myc predominantly in grade II/III and c-myc in grade III gliomas. High-level N-myc expression was detected. In one small-cell glioblastoma and lower levels in five other gliomas. In contrast, glioma cell lines totally lacked N/L-myc expression. The in situ hybridisations revealed mutually exclusive topographic distribution of myc and glial fibrillary acidic protein (GFAP) mRNAs, and a lack of correlation between myc expression and proliferative activity, max and RB1 mRNAs were detected in most tumours and cell lines. The glioma cells displayed interesting alternative splicing patterns of max mRNAs encoding Max proteins which either suppress (Max) or augment (delta Max) the transforming activity of Myc. We conclude that (1) glioma cells in vivo may coexpress several myc genes, thus resembling fetal neural cells; but (2) cultured glioma cells expression only c-myc; (3) myc, max and RB1 are regulated independently in glioma cells; and (4) alternative processing of max mRNA in some glioma cells results in delta Max encoding mRNAs not seen in normal fetal brain.     

Mutations and differential expression of the ras family genes in human nasal polyposis

Although it is well established that ras genes contribute to tumourigenesis either through the accumulation of mutations or by aberrant expression in a wide range of human cancers, little is known regarding their involvement in human nasal polyps (NPs). In the present study, the occurrence of mutations in codons 11 and 12 of the ras family genes was examined by PCR/RFLP and direct sequencing in 23 human NPs and their adjacent turbinates, as well as in turbinates from 13 control subjects. Moreover, the expression pattern of ras mRNA levels was assessed in NP specimens and compared to adjacent and control tissues. K-ras codon 11 and 12 mutations were detected in 17 and 35% of NPs, respectively, and were found in the adjacent inferior turbinate (AIT) (22 and 16%, respectively) and adjacent middle turbinates (AMT) (16 and 26%, respectively). K- and H-ras expression levels were elevated, whereas N-ras mRNA levels were lower in NPs and adjacent turbinates as compared to the control tissues. K-ras mRNA levels were up-regulated in advanced-stage polyps (P=0.037), while N-ras levels were found elevated in small polyps (P=0.046). Statistically significant negative correlations between K- and N-ras expression profiles arose in NPs and AITs (P=0.009 and 0.003, respectively). This, to our knowledge, is the first report on ras mutations and expression analysis in NPs. Our findings suggest a potential key role for activated members of ras family genes in terms of their contribution to the development of NPs as well as to the hypertrophy of adjacent turbinates.     

Tumor resistance to oxidative stress: Association with ras oncogene expression and reversal by lovastatin,an inhibitor of p21ras isoprenylation

The ras oncogene family has been implicated in tumor resistance to ionizing radiotherapy. Using the gene-transfer model, we show here that ras expression may also affect cell responses to chemical inducers of oxidative stress. Studies involving human osteosarcoma subclones, which vary in their levels of EJras expression, revealed a tight correlation between the amounts of ras-encoded mRNA and p21 produced, and the degree of resistance to doxorubicin or hydrogen peroxide. Differences in response could not be explained by increased activity of anti-oxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione S-transferase or glutathione peroxidase. Moreover, there were no significant differences in glutathione levels. Although the resistant cells had elevated levels of gamma-glutamyl-transferase mRNA indicative of an increased rate of glutathione turnover, this elevation was not specific for ras-transfected cell lines. Lovastatin, an inhibitor of protein isoprenylation critical for p21 ras membrane association and function, restored the sensitivity of ras-transformed cells to doxorubicin and hydrogen peroxide. The data indicate that pharmacological agents affecting ras expression may enhance responses of some human tumors to free-radical-mediated chemotherapies. © 1995 Wiley-Liss, Inc.     

Expression of ras and myc oncogenes in human hepatocellular carcinoma and non-neoplastic liver tissues

An immunohistochemical assay was used to assess expression of ras p21 and myc p62 oncogene products in human hepatocellular carcinoma (HCC) and non-neoplastic liver tissues. The monoclonal antibodies Y13 259 and Myc1-9E10, specific for ras p21 and myc p62 oncoproteins, were employed on paraffin-embedded sections. Most HCCs showed enhanced ras p21 and myc p62 expression, as indicated by staining intensity. Cirrhotic livers revealed increased myc p62 and occasionally increased ras p21 expression. HBsAg+ hepatocytes showed intense immunostaining for ras p21. Fibrotic, cholestatic, fetal and normal adult liver did not present enhancement of oncoprotein production. We suggest that combined over-expression of ras and myc oncoproteins may be important for the malignant phenotypic alteration in human HCC.     

An immunocytochemical study of ras and myc oncoproteins and EGFr expression in pleural effusion smears

Pleural effusion smears from 112 patients with either benign or malignant lung disease were investigated for the expression of EGFr and the oncogene proteins myc p64 and ras p21. The streptavidin-biotin peroxidase technique was used. In the studied malignant group of effusions both EGFr and ras have greater sensitivity in the detection of a malignant process than does routine cytological examination though EGFr was less specific. The combination of positive cytology and 3 positive markers is highly specific for a malignant process (90%). Myc and ras had a 100% sensitivity in squamous cell carcinomas but an overall specificity of only 67.3% and 66.6% respectively. The differences in myc and ms positivity, between squamous cell and adenocarcinoma effusion smears were highly significant (p <0.005). All effusion smears associated with undifferentiated carcinomas were ras positive and 2 of them were myc and EGFr positive.     

Analysis of oncogene alterations in human endometrial carcinoma: prevalence of ras mutations

The molecular genetics of human endometrial carcinoma have yet to be defined to any significant extent. Cell lines from 11 endometrial carcinomas were examined for alterations in proto-oncogenes that might predictably be present, based on existing data from the better-characterized human carcinomas of the uterine cervix, ovary, and breast. Codons 12, 13, and 61 of the Ha-ras, Ki-ras, and N-ras genes were examined for possible point mutations, and the c-erbB2/neu, c-myc, and epidermal growth factor receptor (EGFR) genes were examined for amplification or overexpression. Ras mutations were found in seven of 11 (64%) tumors, including three in codon 61 of Ha-ras (CAG----CAT) and four in codon 12 of Ki-ras (GGT----GAT in two and GGT----GTT in two). No evidence was found for amplification or overexpression of the c-erbB2 or EGFR genes in any tumor. One tumor contained amplified c-myc sequences and exhibited relative overexpression of c-myc. These data suggest that the amplification or overexpression of several proto-oncogenes frequently observed in other human gynecologic and breast tumors are not prevalent in endometrial carcinoma and that ras gene mutations are relatively common in this tumor type.     

Clinical relevance of oncogene expression in head and neck tumours

A study was undertaken to determine whether the variation in the increased expression of three oncogenes (Ha-ras, Ki-ras and myc) could be correlated with various clinicopathological parameters of squamous cell carcinoma (SCC) of the head and neck region. No correlation was found with sex, age, site of primary tumour, level of differentiation of the tumour, previous X-ray treatment, or fate. The one exception was myc expression with TNM staging of SCC. A significant increase was found for myc expression in TNM Stage III and IV as compared to the combined stages of I and II. Elevated expression of Ha-ras, Ki-ras and myc oncogenes was found in pleomorphic salivary adenoma (PSA), but at a lower level than SCC. It is proposed that in a percentage of cases the elevated expression of these oncogenes in PSA corresponds to a relatively early event in the multistep process of carcinogenesis.