Evidence of enhancement of the ras oncogene protein product (p21) in a spectrum of human tumors

Triple-negative breast cancer: investigating potential molecular therapeutic target

INTRODUCTION

Triple-negative breast cancer (TNBC) makes up about 10 - 20% of all breast cancers and the lack of hormone receptors and human epidermal growth factor receptor-2/Neu expression is responsible for poor prognosis, no targeted therapies and trouble in the clinical management. Tumor heterogeneity, also within the same tumor, is a major cause for this difficulty. Based on the introduction of new biological drugs against different kinds of tumor, many efforts have been made for classification of genetic alterations present in TNBC, leading to the identification of several oncogenes and tumor suppressor genes involved in breast cancer carcinogenesis.

AREAS COVERED

In this review we investigated the molecular alteration present in TNBC which could lead to the creation of new targeted therapies in the future, with the aim to counteract this disease in the most effective way.

EXPERT OPINION

In this context some hormone receptors like G-protein-coupled receptor 30 and androgen receptors may be a fascinating area to investigate; also, angiogenesis, represented not only by the classical VEGF/VEGFR relationship, but also by other molecules, like semaphorins, fibroblast growth factor and heparin-binding-EGF-like, is a mechanism in which new developments are expected. In this perspective, one technique that may show promise is the gene therapy; in particular the gene transfer could correct abnormal genetic function in cancer cells.

Molecular mechanism of SLC5A8 inactivation in breast cancer

SLC5A8 is a putative tumor suppressor that is inactivated in more than 10 different types of cancer, but neither the oncogenic signaling responsible for SLC5A8 inactivation nor the functional relevance of SLC5A8 loss to tumor growth has been elucidated. Here, we identify oncogenic HRAS (HRAS(G12V)) as a potent mediator of SLC5A8 silencing in human nontransformed normal mammary epithelial cell lines and in mouse mammary tumors through DNMT1. Further, we demonstrate that loss of Slc5a8 increases cancer-initiating stem cell formation and promotes mammary tumorigenesis and lung metastasis in an HRAS-driven murine model of mammary tumors. Mammary-gland-specific overexpression of Slc5a8 (mouse mammary tumor virus-Slc5a8 transgenic mice), as well as induction of endogenous Slc5a8 in mice with inhibitors of DNA methylation, protects against HRAS-driven mammary tumors. Collectively, our results provide the tumor-suppressive role of SLC5A8 and identify the oncogenic HRAS as a mediator of tumor-associated silencing of this tumor suppressor in mammary glands. These findings suggest that pharmacological approaches to reactivate SLC5A8 expression in tumor cells have potential as a novel therapeutic strategy for breast cancer treatment.

Molecular biology of lung cancer: clinical implications

Lung cancer is a heterogeneous disease clinically, biologically, histologically, and molecularly. Understanding the molecular causes of this heterogeneity, which might reflect changes occurring in different classes of epithelial cells or different molecular changes occurring in the same target lung epithelial cells, is the focus of current research. Identifying the genes and pathways involved, determining how they relate to the biological behavior of lung cancer, and their utility as diagnostic and therapeutic targets are important basic and translational research issues. This article reviews current information on the key molecular steps in lung cancer pathogenesis, their timing, and clinical implications.

Human mammary cancer progression model recapitulates methylation events associated with breast premalignancy

Introduction

We have previously identified a rare subpopulation of variant human mammary epithelial cells (vHMEC) with repressed p16^INK4A that exist in disease-free women yet display premalignant properties, suggesting that they have engaged the process of malignant transformation. In order to gain insight into the molecular alterations required for vHMEC to progress to malignancy, and to characterize the epigenetic events associated with early progression, we examined the effect of oncogenic stress on the behavior of these cells.

Methods

HMEC that express p16^INK4A and vHMEC that do not, were transduced with constitutively active Ha-rasV12 and subsequently exposed to serum to determine whether signals from the cellular microenvironment could cooperate with ras to promote the malignant transformation of vHMEC. Epigenetic alterations were assessed using methylation-specific polymerase chain reaction (PCR).

Results

vHMEC expressing Ha-rasV12 (vHMEC-ras) bypassed the classic proliferative arrest that has been previously documented in normal fibroblasts following oncogenic stress, and that we also observe here in normal HMEC. Moreover, vHMEC-ras cells exhibited many additional alterations that are observed during progression to malignancy such as the generation of chromosomal abnormalities, upregulation of telomerase activity, immortalization following exposure to serum, and anchorage-independent growth, but they did not form tumors following orthotopic injection in vivo. Associated with their early progression to malignancy was an increase in the number of genes methylated, two of which (RASSF1A and SFRP1) were also methylated in other immortalized mammary cell lines as well as in breast cancer cells and tissues.

Conclusions

We have characterized a mammary progression model that recapitulates molecular and methylation alterations observed in many breast cancers. Our data suggest that concomitant methylation of RASSF1A and SFRP1 marks an early event in mammary transformation and may thus have prognostic potential.

Proteomic and phosphoproteomic alterations in benign, premalignant and tumor human breast epithelial cells and xenograft lesions: biomarkers of progression

The MCF10A human breast epithelial cell lineage includes the benign MCF10A cells, premalignant cells (MCF10AT, MCF10ATG3B) and malignant MCF10CA1a tumor cells. The premalignant and tumor cells recapitulate the progressive alterations associated with the temporal development of PBD and carcinoma. Ras protein levels were elevated by 6.9-, 22.4- and 32.2-fold in 10AT, 10ATG3B and 10CA1a cells, respectively, relative to 10A cells. K-Ras was not detected, N-Ras levels were unchanged; Rac and Rho levels increased in 10CA1a tumor cells. Phospho-phosphatidylinositol 3-kinase, phosphoinositide-dependent protein kinase 1 (PDK1), phospho-PDK1, phospho-eukaryotic translation initiation factor 4E (eIF4E) and phospho-eukaryotic initiation factor 4E binding protein 1 (4E-BP1) levels progressively increased in the cell lineage, with the greatest increase monitored in 10CA1a tumor cells. Phospho Ser 473 and Thr 408 Akt levels increased 10.2- and 136-fold in 10CA1a cells, respectively, relative to 10A cells. Phospho-p70S6 kinase (p70S6K) increased >2-fold in 10CA1a cells, relative to 10A cells. Immunohistochemistry confirmed Ras, phospho-Akt and phospho-p70S6K (Thr 421/ Ser 424) expression in lesions arising from premalignant and tumor cells. FOXO 1, phospho-FOXO 1 and phospho-FOXO 4 were significantly elevated in 10ATG3B premalignant and 10CA1a tumor cells. Phospho-FOXO 3a was progressively elevated, with the greatest levels detected in 10CA1a tumor cells. Immunohistochemistry revealed that phospho-FOXO 1, 3a and 4 staining was less in benign lesions, but elevated in advanced 10ATG3B and malignant 10CA1a lesions, showing a correspondence between the cells and lesions. Hence, phospho-Akt and phospho-FOXO 1, 3a and 4 merit consideration as biomarkers of tumorigenic risk from hyperplastic breast tissue.

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.

Early involvement of the phosphatidylinositol 3-kinase/Akt pathway in lung cancer progression

Signaling through the phosphatidylinositol 3-kinase (PI3-kinase) pathway has been associated with lung tumorigenesis. We examined the association between gene copy number of the PI3-kinase catalytic subunit alpha (PIK3CA) and phosphorylated Akt expression in invasive and preinvasive lung cancers. We sought to determine at what stage of tumor development gene copy number increase or phosphorylated Akt overexpression might affect tumor development. We assessed PIK3CA gene copy number by fluorescence in situ hybridization and expression of phosphorylated Akt by immunohistochemistry in 242 invasive and 43 preinvasive lung cancers and correlated our findings with clinical outcome. The PIK3CA was amplified in 70% of squamous carcinomas, 38% of large cell carcinomas, 19% of adenocarcinomas, and 67% of small cell lung cancers. Phosphorylated Akt overexpression was frequently observed, and strongly so in 12 to 17% of lung cancers depending on nuclear or cytoplasmic localization. Neither PIK3CA gene copy number nor phosphorylated Akt protein expression had prognostic significance. In preinvasive lesions, amplification of the PIK3CA and overexpression of phosphorylated Akt were associated with severe dysplasia and each other. These observations suggest frequent and early involvement of the PI3-kinase pathway in lung cancer.

Progressive Resistance to Apoptosis in a Cell Lineage Model of Human Proliferative Breast Disease

BACKGROUND

Proliferative breast disease (PBD) may increase a woman's risk of developing breast cancer, perhaps by decreasing cellular sensitivity to apoptosis. To determine whether resistance to apoptosis develops during PBD, we investigated apoptosis initiated through the Fas pathway in a series of cell lines that recapitulates the morphologic changes of PBD in nude/beige mice.

METHODS

The series of cell lines used was MCF-10A cells (parental preneoplastic human breast epithelial cells), MCF-10AT cells (transformed with T(24) Ha-ras), and MCF-10ATG3B cells (derivative cells that progress to carcinoma). Fas-mediated apoptosis, induced when a Fas monoclonal antibody bound to and activated the Fas receptor on these cells, was assessed morphologically and by flow cytometry. Levels of proteins involved in Fas-mediated apoptosis and cleavage of poly(adenosine diphosphate-ribose) polymerase (PARP), an end product of caspase activation, were determined by immunoblotting. Bcl-2 and Bax heterodimerization was examined by coimmunoprecipitation. All statistical tests were two-sided.

RESULTS

Sensitivity to Fas-mediated apoptosis decreased with the tumorigenic potential of cells: MCF-10A cells were extremely susceptible, MCF-10AT cells were less susceptible, and MCF-10ATG3B cells were resistant. The percentage of apoptotic cells declined, from 24% to 8% to 6%, respectively. All lines produced Fas ligand (FasL) and had comparable levels of Fas receptor, FasL, Fas-associated death-domain protein, and caspases 3 and 6. Levels of caspase 8 were similar in MCF-10A and MCF-10AT cells but about 30% lower in MCF-10ATG3B cells (P>.01 but <.05). Levels of caspase 10 were about 20% lower in MCF-10AT cells (P>.005 but <.01) and about 59% lower in MCF-10ATG3B cells than in MCF-10A cells (P>.01 but <.05). PARP cleavage was detected in MCF-10A and MCF-10AT cells but not in MCF-10ATG3B cells. Levels of Bax, Bid, and Bak proteins were similar in all lines, but levels of Bcl-2 were lower in MCF-10AT and MCF-10ATG3B cells than in MCF-A cells, and Bcl-2-Bax heterodimerization progressively declined in the series.

CONCLUSION

Resistance to Fas-mediated apoptosis appears to develop progressively in the MCF-10AT cell series.

Nontransgenic models of breast cancer

Numerous models have been developed to address key elements in the biology of breast cancer development and progression. No model is ideal, but the most useful are those that reflect the natural history and histopathology of human disease, and allow for basic investigations into underlying cellular and molecular mechanisms. We describe two types of models: those that are directed toward early events in breast cancer development (hyperplastic alveolar nodules [HAN] murine model, MCF10AT human xenograft model); and those that seek to reflect the spectrum of metastatic disease (murine sister cell lines 67, 168, 4T07, 4T1). Collectively, these models provide cell lines that represent all of the sequential stages of progression in breast disease, which can be modified to test the effect of genetic changes.

Estrogen inducibility of c-Ha-ras transcription in breast cancer cells. Identification of functional estrogen-responsive transcriptional regulatory elements in exon 1/intron 1 of the c-Ha-ras gene

Although mutation of ras gene is rare in human breast cancer, overexpression of normal c-Ha-ras gene is frequently observed. Using a mouse mammary metastasis model consisting of genetically related mammary tumor sublines with variant metastatic potential, we have previously (i) demonstrated a direct correlation between c-Ha-ras mRNA and protein levels and metastatic potential and (ii) identified a novel hormone-responsive transcriptional regulatory element in intron 1 of the mouse c-Ha-ras gene that contains the consensus half-site of a glucocorticoid response element and flanking consensus half-sites for estrogen response element. Here, we have examined the functionality of intron 1 sequence in context of upstream sequences by using transient transfection assays with plasmids expressing chloramphenicol acetyltransferase. Intron 1 sequence and sequences similar to intron 1 element located in exon 1 function as transcriptional regulatory elements that confer hormonal inducibility to chloramphenicol acetyltransferase gene expression both independently and in context of 5'-flanking sequences. Measurement of c-Ha-ras transcription rates and protein expression by nuclear run-on and metabolic labeling assays showed a 5-12-fold enhancement, respectively, following treatment with 17beta-estradiol that was blunted by ICI 182,780 in the nonmetastatic variant. In contrast, constitutive overexpression of c-Ha-ras transcripts and protein in the metastatic subline was unaffected by estrogen and ICI 182,780. Gel shift assays demonstrated specific interaction of c-Ha-ras exon 1 sequence with nuclear proteins of human breast cancer MCF-7 cells with formation of two complexes, one of which contains estrogen receptor. Our data demonstrate a direct (i) interaction of c-Ha-ras sequence with estrogen receptor and (ii) stimulatory effect of estrogen on c-Ha-ras gene transcription and suggest that alteration in transcriptional regulation of c-Ha-ras gene by estrogen may play an important role in progression of breast cancer.

Conserved cis-elements bind a protein complex that regulates Drosophila ras2/rop bidirectional expression

The Drosophila ras2 promoter region exhibits bidirectional activity, as has been demonstrated for the human c-Ha-ras1 and the mouse c-Ki-ras. Here we address a unique case of ras regulation, as Drosophila ras2 provides the only example to date in which the flanking gene (rop) and its product have been isolated. A linking mechanism of control suggests a mutual interaction between the two gene products. Our studies indicate that the Drosophila ras2 promoter region shares with the human c-Ha-ras1 promoter a CACCC box and an AP-1-like sequence. A 14 bp promoter fragment which holds a CACCC element is demonstrated to interact with a specific transcription factor (factor B). This CACCC promoter element represents a stretch of imperfect palindrome. We present evidence that this factor can form a complex with another specific DNA-binding protein (factor A). The binding sites (A + B) for these protein factors are essential for 95% expression of both genes flanking the promoter (ras2 and rop). Region A consists of four overlapping consensus sequences: a TATA-like element, a DSE-like motif (the core sequence of the serum response element), a DRE octamer, which has been shown to play a role in cell proliferation, and a 5 bp direct repeat representing the GATA consensus sequence. Factor A has a very weak affinity to the full promoter region, but when complexed with factor B binding efficiency is enhanced. We also show that alterations of DNA-protein binding specificities can be achieved by supplementing the growth media with different sera.

Allele loss and point mutation in codons 12 and 61 of the c-Ha-ras oncogene in carcinogen-transformed human breast epithelial cells

There is significant evidence that the ras oncogene plays a role in experimental mammary carcinogenesis; the evidence in human breast cancer, however, is more limited. We induced the expression of transformation phenotypes in the human breast epithelial cell line MCF-10F with the chemical carcinogens 7,12-dimethylbenz[a]anthracene, N-methyl-N-nitrosourea, N-methyl-N-nitro-N'-nitrosoguanidine, and benzo[a]pyrene. This work was designed to clarify whether chemically induced neoplastic transformation correlates with alterations in the ras gene. MCF-10F cells have two c-Ha-ras alleles, identified by 1.0-kb and 1.2-kb restriction fragments. Treatment with carcinogens resulted in the loss of one of the alleles (1.0 kb). Polymerase chain reaction-amplified DNA from all carcinogen-treated cells was analyzed for point mutations in c-Ha-ras at codons 12 and 61. All of the carcinogens induced a mutation of the remaining allele at the first position of codon 12 (GGC-->AGC). Another frequent mutation occurred at the first position of codon 61 (CAG-->GAG). The changes in c-Ha-ras were associated with the emergence of colony formation in agar-methocel, but no specific changes in this gene correlated with the emergence of invasiveness or tumorigenesis, indicating that other genes may be involved in the process.

Molecular pathology of gastric carcinoma: progress and prospects

Gastric carcinoma is the fourth most common malignancy in Western Europe and a major cause of cancer morbidity and mortality worldwide, particularly in the Far East and in areas of South America. The natural history of the disease is not fully established, and there is a need to elucidate the molecular mechanisms of gastric carcinogenesis in order to understand its pathogenesis and to develop molecular markers for clinical diagnostic use. Molecular analysis of colonic carcinogenesis has increased our understanding of its pathogenesis and has demonstrated multistage carcinogenesis in a human cancer. Research in gastric carcinoma has not achieved such significant progress, although a start has been made. We analyze some of the interpretation problems in molecular pathology affecting progress that are of interest to the histopathologist and review recent studies on the molecular biology of gastric carcinoma involving flow cytometry, cytogenetics, allele loss analysis, and transfection. We also summarize current knowledge about each of the major oncogenes and suppressor genes, attempting, in particular, to correlate gene abnormalities with morphologic appearances. The expanding field of cell proliferation and growth factors is outlined, gastric and colon carcinomas are compared, and gastric carcinoma is considered as a model system for the study of differentiation. This report concludes by suggesting directions for future research.

Occupation, smoking, and the risk of high-grade invasive bladder cancer in Missouri

Numerous epidemiological studies have established that occupational exposures and smoking are the two major known risk factors for the development of bladder cancer. Using data from the Missouri Cancer Registry, we investigated the hypothesis that individuals with occupationally-related bladder cancer are more likely to have a more invasive form of the disease. Data were analyzed for 2,893 white males diagnosed with primary bladder cancer in Missouri between 1984 and 1988. Of the 1,415 cases whose occupational status was recorded, 236 (17%) were employed in high-risk occupations. Cases with high-grade disease were more likely to have been employed in a high-risk occupation, after adjustment for age and smoking (adjusted odds ratio [AOR] = 1.7, 95% confidence interval [CI] = 1.1-2.6). High-risk workers under 60 years of age were most at risk for developing high-grade bladder tumors (AOR = 2.3, 95% CI = 1.0-5.3). There was no overall association between high-risk occupation and late-stage disease (AOR = 1.1, 95% CI = 0.7-1.5), but it was present in the men younger than 60 years of age (AOR = 2.0, 95% CI = 1.0-3.8). No association was found between tobacco use and grade (AOR = 1.1, 95% CI = 0.8-1.5), but cases with late-stage disease were more likely to be smokers (AOR = 1.5, 95% CI = 1.1-1.9). When occupations were examined individually, motor vehicle operators, truck drivers, vehicle mechanics, other mechanics, and janitors were among those most likely to be diagnosed with high-grade or late-stage tumors. Although further studies are necessary to confirm these results, they suggest that surveillance and targeted screening of workers in high-risk occupations may result in a greater yield of early invasive cancers and possibly decrease the mortality associated with this disease.

Diagnostic utility of oncogenes and their products in human cancer

The first clear cut association of an oncogene with a specific cancer is the c-abl translocation in chronic myelogenous leukemia and acute lymphocytic leukemia; it has been observed in 90% of CML cases examined. This is the major contributing factor to its being the target of the first oncogene-based FDA-approved diagnostic test. Although the role of the abl translocation in the tumorigenic process is not yet understood, it is clear that somehow it must be causally related to the disease, and thus is an ideal target for a diagnostic test. The association of this oncogene with a specific cancer is the model on which all others may be based in the future. Second generation tests could easily include PCR on mRNA, and/or in situ hybridization, both of which could be performed using blood samples. Both methods would provide a faster means of testing a large number of cells, however, the methodologies must be improved through automation and computer-aided image analysis, respectively, in order to become useful routine tests. Both neu and epidermal growth factor receptor (EGFR) appear to have a close correlation between overexpression of the gene product and outcome of disease in breast cancer; valuable information for prognosis of the disease. And again, although the actual mechanism of action of these molecules and how this relates to the tumorigenic process is not yet known, it is believed from the very nature of the molecules that they must in some way contribute to the progression of the disease. In both cases, the protein products are overexpressed in tissue, and in the case of Neu, it appears as through at least some of the patients have a Neu-related protein in their serum. These molecules present relatively easy targets for the development of diagnostic/prognostic assays, as antibodies are easily made and can be incorporated into a variety of assay formats. Current assays available, an ELISA for Neu and a radio-ligand binding assay for EGFR, are highly sensitive, reproducible and relatively easy to perform. Only the ELISA is commercially available, however, and hence allows for easy comparison between laboratories. An abvious step towards the routine measurement of EGFR then is the development of a comparable commercially available test. An improvement for both types of assay would be the incorporation of an internal control to gauge the cellular component of the tissue samples that are tested. The outcome of the applications of myc and ras to cancer diagnostics is not so easily predictable, with a couple of exceptions.(ABSTRACT TRUNCATED AT 400 WORDS)

Enhanced immunoreactivity of ras oncogene p21 protein in urinary bladder epithelium of rats treated with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide

Normal urothelium and various lesions of the rat urinary bladder induced by the dietary administration of 0.2% N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) (up to 77 weeks) or by the combination of 0.2% FANFT and the subsequent administration of 5% sodium saccharin or 2% DL-tryptophan (up to 104 weeks) were evaluated for immunoreactivity with monoclonal antibody to ras p21 by avidin-biotin immunohistochemistry. Seventy-one to 100% of transitional cell carcinomas showed strong reactivity to the antibody to ras p21 depending on treatment with long-term administration of FANFT or by 6 weeks administration of FANFT followed by sodium saccharin or DL-tryptophan. Focal reactivity to the ras p21 antibody was frequently observed in the hyperplastic (57-96%) or normal appearing urinary bladder epithelium (50-100%) in rats treated with FANFT (FANFT alone or in combination with sodium saccharin or tryptophan) but not in hyperplasia or normal epithelium in rats given sodium saccharin or tryptophan alone, without pretreatment with FANFT or in untreated controls. The present results show that there is a close association of enhanced immunoreactivity with ras p21 antibody in the urinary bladder epithelium to FANFT treatment, and that ras p21 is expressed in normal, hyperplastic and neoplastic lesions of the bladder of rats treated with FANFT. These results suggest that enhanced immunoreactivity with ras p21 is observed as a consequence of the treatment with FANFT but it alone does not reflect the progression from benign to malignant lesions.

Transformation of human breast epithelial cells by c-Ha-ras oncogene

To determine whether the c-Ha-ras oncogene plays a role in the initiation of mammary carcinogenesis, an immortalized human breast epithelial cell line, MCF-10A, was transfected with the plasmid vector pHo6T1 containing the T24 Ha-ras oncogene and the aminoglycoside phosphotransferase gene, which confers resistance to geneticin. Transfected cells exhibited an altered pattern of growth and tridimensional morphology in collagen gel. They also exhibited anchorage-independent growth and loss of requirement for hormones and epidermal growth factor; in addition, they expressed invasiveness and increased collagenolytic activity in an in vitro system and became tumorigenic in irradiated nude mice, all properties indicative of malignant transformation. Transformed cells contained the mutated c-Ha-ras oncogene and expressed the p21 mutated protein. These data indicate that the c-Ha-ras oncogene is capable of inducing malignant phenotypes in immortalized human breast epithelial cells.

Structural analysis of the mouse c-Ha-ras gene promoter

Previous studies have demonstrated that the mouse c-Harvey ras proto-oncogene (c-Ha-ras) promoter sequences are GC rich and contain several potential transcription factor SP1 binding sites. We investigated the endonuclease hypersensitivity of this region in nuclei in vitro and whole mouse tissues in vivo and identified a very strong, ubiquitous hypersensitive site covering the proximal promoter sequences. Footprint protection studies using nuclear extracts from various cell types including fibroblasts, erythroid cells, and both normal and transformed epithelial cells revealed a consistent protein-binding pattern. Five protein binding sites were observed, four of which correlated with potential SP1 binding sites. Competition experiments using an oligonucleotide corresponding to a consensus SP1 binding site confirmed that these sequences were indeed bound by the SP1 (or SP1-like) trans-acting factor. In addition, no differences were observed between the footprint patterns obtained using extracts from cells of different lineages or between normal and transformed epithelial cells carrying activated ras genes. The controlling elements responsible for differential c-Ha-ras transcription between cell types or at different stages of carcinogenesis therefore probably lie in other regions of the gene.

Histologic variation among experimental tumors of common origin: relationships to viral p21 expression and to tumor-derived extracellular matrix

Transformed lines, obtained by infection of adult rat adrenocortical fibroblast-like cells with Kirsten murine sarcoma virus, produce s.c. tumors which range histologically from fibrosarcomas to carcinomas to undifferentiated neoplasms. This study was undertaken to determine whether the histology was a stable characteristic of individual lines and whether it was related to oncogene expression and to differentiation in culture. Three lines were infected at passage 1 and tumor histology, differentiation markers and expression of the transforming protein v-p21 were evaluated periodically over a 1-year period. The original stromal characteristics of the target cells (metachromatic extracellular matrix (ECM), a high rate of collagen production and collagen incorporation into ECM, and a fibroblastic morphology) diminished with transformation. In contrast, parenchymal differentiation markers (lipid, steroidogenic enzymes) were enhanced and constitutively expressed in all lines. The two lines in which ECM production was most reduced formed carcinomas in vivo, while the third line showed a smaller shift in these characteristics and formed sarcomas. Thus, histopathology seemed to be influenced by tumor-derived ECM but unrelated to the expression of steroidogenic properties. The tumors became less differentiated with time, but retained distinct line-specific phenotypes. Throughout the study, v-p21 remained overexpressed in all lines to a similar degree, but the subcellular localization of v-p21 differed between fibroblastic and epithelial cells, suggesting a possible correlation with differentiation.

Application of automated image analysis to demonstrate the correlation between ras p21 expression and severity of gliomas

We found a direct correlation between increasing ras p21 protein immunopositivity and severity of human glioma using computer-assisted, digital-image processing to quantify the amount of p21 immunoreactive to the monoclonal antibody RAP-5. We determined that there was a significant difference in reactivity between glioblastoma multiformes and more-differentiated astrocytomas (experiment-wise error less than 0.05). This result confirmed the conclusions made on the same tumors using standard light microscopy and visual examination. Immunohistochemistry quantized by automated image analysis may be a useful adjunct to current histopathological strategies since it decreases assay subjectivity and variation.

An immunohistochemical analysis of ras oncogene expression in epithelial neoplasms of the colon

Colonic epithelial tumors (101) including villoglandular adenomas, carcinomas in situ, adenocarcinomas, and neuroendocrine (NE) carcinomas were studied immunohistochemically with monoclonal antibodies (MoAb) RAP-5 and RAS-10 recognizing altered and unaltered ras oncogene products. In addition, 20 samples from multiple polyposis including adenomas with and without dysplasia, carcinomas in situ, and invasive carcinomas were studied. Using immunostaining techniques, normal mucosa was weakly stained, whereas the mucosa in the vicinity of tumors or inflammation showed enhanced staining. More tumors stained intensely with MoAb RAP-5 than with MoAb RAS-10. With MoAb RAP-5, most benign and malignant tumors showed enhanced staining. No significant differences in staining were noted in relation to superficial versus deeply invasive carcinomas or clinical staging. Immunostaining was also noted in some metastases. No significant differences in enhanced staining were found in carcinomas. Interestingly, the most extensive and enhanced immunostaining was noted in the villoglandular adenomas, dysplastic adenomas, and carcinomas in situ. The authors conclude that (1) ras protein expression is detectable in most benign, borderline, and malignant epithelial tumors of the colon as determined with MoAb RAP-5 and RAS-10, whereas enhanced expression is more often detected with RAP-5; (2) enhanced ras product expression in colon carcinomas does not seem to correlate with advanced tumor stages or with exocrine, NE, or phenotypically mixed tumors; and (3) the finding of the most intensely enhanced ras products expression in villoglandular polyps and carcinomas in situ suggests a possibly significant role for the oncogene in the early phases of transformation.

Some ras-transformed cells have increased radiosensitivity and decreased repair of sublethal radiation damage

We examined the effect of 60Co irradiation on the clonogenic survival of rat NRK cells, NRK cells carrying a temperature-sensitive viral K-ras oncogene (tsK-NRK), mouse NIH 3T3 cells, and NIH 3T3 cells transformed with the human bladder cancer (T24) H-ras oncogene (PAP2). We tested the hypothesis that ras oncogene expression renders cells more resistant to radiation, but found in both systems that ras-transformed cells were more, not less, sensitive to radiation. We also found indications of altered repair of sublethal radiation damage. PAP2 cells were more sensitive to radiation than NIH 3T3 cells. Increased sensitivity was reflected in a decreased shoulder region of the survival curve with little effect on its slope (D0). TsK-NRK cells were also slightly more sensitive to radiation than NRK and exhibited decreased repair of sublethal damage at both the permissive and nonpermissive temperatures. Thus, we found that expression of ras oncogenes is not always associated with increased radiation resistance. In summary, our results suggest that (1) ras oncogene expression in some cells may be associated with increased, rather than decreased, radiation sensitivity, and (2) ras oncogene expression may alter the shoulder region of the dose response curve, suggesting changes in the repair of sublethal radiation damage.