Expression of p21ras in normal and malignant human tissues: lack of association with proliferation and malignancy

KRAS protein expression becomes progressively restricted during embryogenesis and in adulthood

KRAS mutants are common in many cancers and wild-type KRAS is essential in development as its absence causes embryonic lethality. Despite this critical role in development and disease, the normal expression pattern of KRAS protein is still largely unknown at the tissue level due to the lack of valid antibodies. To address this issue, we used the citrine-Kras mouse model in which the Citrine-KRAS (Cit-K) fusion protein functions as a validated surrogate of endogenous KRAS protein that can be detected on tissue sections by immunolabeling with a GFP antibody. In the embryo, we found expression of KRAS protein in a wide range of organs and tissues. This expression tends to decrease near birth, mainly in mesenchymal cells. During transition to the adult stage, the dynamics of KRAS protein expression vary among organs and detection of KRAS becomes restricted to specific cell types. Furthermore, we found that steady state KRAS protein expression is detectable at the cell membrane and in the cytoplasm and that this subcellular partitioning differed among cell types. Our results reveal hitherto unanticipated dynamics in developmental, tissular, cell-specific and subcellular expression of KRAS protein. They provide insight into the reason why specific cell-types are sensitive to KRAS mutations during cancer initiation.

Characterization of oncogene suppressor marker expression in patients with submucosal gastric carcinoma

The aim of the present study was to determine the clinical significance of p53 and p21^ras p21^wafl, p27^kip1 and p16^ink4a expression in cases of early gastric cancer. A total of 81 patients who had undergone gastrectomy with D2 lymphadenectomy between 1971 and 2004 were retrospectively investigated. The immunohistochemical expression of p21^ras, p53, p21^waf1/cip1, p27^kip1 and p16^ink4a in the tissues was evaluated. In normal, metaplastic and tumoral mucosa, p53 was positive in 53, 87.3, and 87.1% of the cases, respectively. In the same tissues, p21^ras was positivE in 85.3, 86 and 96.8%, respectively. Positivity FOR p16^ink4a was DETECTED IN 46.3, 91.1 and 86% OF THE CASES, respectively, WHEREAS p27^kip1 WAS positiVE IN 60, 94.7 and 95.3%, and p21^wafl/cip1 WAS positivE IN 32.4, 72.7 and 71.4% OF THE CASES, respectively. All THE tumors WERE positive for p53. Tumors with lymph node invasion presented WITH OVERexpression (+4) of p53 in 47% of the cases VS. 17% OF patients who DID not HAVE lymph node involvement. THEREFORE, higher expression of p53, p21^ras and p21^wafl/cip1 IN the tumor exhibited a statistically significant association with lymph node involvement.

K-Ras Promotes Tumorigenicity through Suppression of Non-canonical Wnt Signaling

K-Ras and H-Ras share identical effectors and have similar properties; however, the high degree of tumor-type specificity associated with K-Ras and H-Ras mutations suggests that they have unique roles in oncogenesis. Here, we report that oncogenic K-Ras, but not H-Ras, suppresses non-canonical Wnt/Ca(2+) signaling, an effect that contributes strongly to its tumorigenic properties. K-Ras does this by binding to calmodulin and so reducing CaMKii activity and expression of Fzd8. Restoring Fzd8 in K-Ras mutant pancreatic cells suppresses malignancy, whereas depletion of Fzd8 in H-Ras(V12)-transformed cells enhances their tumor initiating capacity. Interrupting K-Ras-calmodulin binding using genetic means or by treatment with an orally active protein kinase C (PKC)-activator, prostratin, represses tumorigenesis in K-Ras mutant pancreatic cancer cells. These findings provide an alternative way to selectively target this "undruggable" protein.

Functional specificity of ras isoforms: so similar but so different

H-ras, N-ras, and K-ras are canonical ras gene family members frequently activated by point mutation in human cancers and coding for 4 different, highly related protein isoforms (H-Ras, N-Ras, K-Ras4A, and K-Ras4B). Their expression is nearly ubiquitous and broadly conserved across eukaryotic species, although there are quantitative and qualitative differences of expression depending on the tissue and/or developmental stage under consideration. Extensive functional studies have determined during the last quarter century that these Ras gene products are critical components of signaling pathways that control eukaryotic cell proliferation, survival, and differentiation. However, because of their homology and frequent coexpression in various cellular contexts, it remained unclear whether the different Ras proteins play specific or overlapping functional roles in physiological and pathological processes. Initially, their high degree of sequence homology and the observation that all Ras isoforms share common sets of downstream effectors and upstream activators suggested that they were mostly redundant functionally. In contrast, the notion of functional specificity for each of the different Ras isoforms is supported at present by an increasing body of experimental observations, including 1) the fact that different ras isoforms are preferentially mutated in specific types of tumors or developmental disorders; 2) the different transforming potential of transfected ras genes in different cell contexts; 3) the distinct sensitivities exhibited by the various Ras family members for modulation by different GAPs or GEFs; 4) the demonstration that different Ras isoforms follow distinct intracellular processing pathways and localize to different membrane microdomains or subcellular compartments; 5) the different phenotypes displayed by genetically modified animal strains for each of the 3 ras loci; and 6) the specific transcriptional networks controlled by each isoform in different cellular settings.

Epithelial tissues have varying degrees of susceptibility to Kras(G12D)-initiated tumorigenesis in a mouse model

Activating mutations in the Kras gene are commonly found in some but not all epithelial cancers. In order to understand the susceptibility of different epithelial tissues to Kras-induced tumorigenesis, we introduced one of the most common Kras mutations, Kras^G12D, broadly in epithelial tissues. We used a mouse model in which the G12D mutation is placed in the endogenous Kras locus controlled by inducible, Cre-mediated recombination in tissues expressing cytokeratin 19 including the oral cavity, GI tract, lungs, and ducts of the liver, kidney, and the pancreas. Introduction of the Kras^G12D mutation in adult mouse tissues led to neoplastic changes in some but not all of these tissues. Notably, many hyperplasias, metaplasias and adenomas were observed in the oral cavity, stomach, colon and lungs, suggesting that exposure to products of the outside environment promotes Kras^G12D-initiated tumorigenesis. However, environmental exposure did not consistently correlate with tumor formation, such as in the small intestine, suggesting that there are also intrinsic differences in susceptibility to Kras activation. The pancreas developed small numbers of mucinous metaplasias with characteristics of early stage pancreatic intraepithelial neoplasms (PanINs), supporting the hypothesis that pancreatic ducts have the potential to give rise pancreatic cancer.

SAFROLE OXIDE INDUCES APOPTOSIS IN A549 HUMAN LUNG CANCER CELLS

3,4-(Methylenedioxy)-1-(2',3'-epoxypropyl)-benzene (safrole oxide) was synthesized in the authors' laboratory. To investigate the effects of safrole oxide on the growth and apoptosis of A549 human lung cancer cells, the authors treated the cells with safrole oxide, 112.36 to 449.44 micromol/L, for 24 to 48 hours. The results showed that the drug led A549 cells to apoptosis and blocked cell cycle completely at G1 phase and partly at G(2)-M phase. To further study the correlated mechanism, the authors examined P53 and H-Ras protein expressions by using immunofluorescence assay. They found that the expression of P53 was dramatically up-regulated but the expression of H-Ras was hardly affected by safrole oxide, 224.72 micromol/L, within 24 hours. Taken together, these results revealed that safrole oxide could induce apoptosis of A549 cells and suggested that safrole oxide might perform its function by blocking cells completely at G1 phase and partly at G(2)-M phase, and also by up-regulating the expression of P53 protein. These findings would raise exciting possibilities for cancer therapy in future.

Specificity and expression of RalGPS as RalGEFs

Ral proteins regulate a variety of biological processes and are major downstream targets of Ras because of association of the RalGDS family of exchange factors with Ras-GTP. However, a second, less-characterized family of Ral GEFs has also been isolated. Described here are methods used to determine the substrate specificity of this RalGPS family of GEFs, measure their membrane localization, interactions of with SH3 domains and phospholipids, as well as to measure their ability to activate Ral in vivo.

Activated Kras, but not Hras or Nras, may initiate tumors of endodermal origin via stem cell expansion

The three closely related human Ras genes, Hras, Nras, and Kras, are all widely expressed, engage a common set of downstream effectors, and can each exhibit oncogenic activity. However, the vast majority of activating Ras mutations in human tumors involve Kras. Moreover, Kras mutations are most frequently seen in tumors of endodermally derived tissues (lung, pancreas, and colon), suggesting that activated Kras may affect an endodermal progenitor to initiate oncogenesis. Using a culture model of retinoic acid (RA)-induced stem cell differentiation to endoderm, we determined that while activated HrasV12 promotes differentiation and growth arrest in these endodermal progenitors, KrasV12 promotes their proliferation. Furthermore, KrasV12-expressing endodermal progenitors fail to differentiate upon RA treatment and continue to proliferate and maintain stem cell characteristics. NrasV12 neither promotes nor prevents differentiation. A structure-function analysis demonstrated that these distinct effects of the Ras isoforms involve their variable C-terminal domains, implicating compartmentalized signaling, and revealed a requirement for several established Ras effectors. These findings indicate that activated Ras isoforms exert profoundly different effects on endodermal progenitors and that mutant Kras may initiate tumorigenesis by expanding a susceptible stem/progenitor cell population. These results potentially explain the high frequency of Kras mutations in tumors of endodermal origin.

Two cases of uveal amelanotic melanoma in transgenic Tyr-HRAS+ Ink4a/Arf heterozygous mice

Uveal melanoma (UM) is uncommon among wild type mice. Efforts to develop transgenic mice to study this disease have resulted in pigmented tumors derived from the retinal pigment epithelium (RPE) or mixed tumors of RPE and UM complicating the study of UM specifically. Reported here are two early stage intraocular amelanotic melanomas discovered in 2 Tyr-HRAS+ Ink4a/Arf heterozygous (1 normal CKDN2A allele) transgenic FVB/n mice. These tumors were morphologically and immunohistochemically similar to spontaneous UM recently reported in the Ink4a/Arf homozygous (CKDN2A knockout) parent strain. The tumors originated in the posterior uveal tract. The neoplasms were comprised of bundles of spindle-shaped melanocytes admixed with some epithelioid cells. Tumors were immunohistochemically positive for neuron-specific enolase, S-100, pan-ras, but negative for cytokeratin and Melan-A. The development of early lenticular opacity and bilateral cataracts is a consistent phenotype of transgenic mice in which the retinoblastoma signaling pathway has been disrupted. Lenticular opacity and cataracts are rarely observed clinically in Tyr-HRAS+ Ink4a/Arf heterozygotes, rendering this strain suitable for ophthalmoscopy. Consequently, Tyr-HRAS+ Ink4a/Arf heterozygotes provide practical advantages, compared to the cataract-prone CKDN2A knockout strains, for real-time ophthalomoscopic detection and monitoring of UM while developing chemotherapeutic regimens and other research to understand the biology of UM.

K-ras is critical for modulating multiple c-kit-mediated cellular functions in wild-type and Nf1+/- mast cells

p21(ras) (Ras) proteins and GTPase-activating proteins (GAPs) tightly modulate extracellular growth factor signals and control multiple cellular functions. The specific function of each Ras isoform (H, N, and K) in regulating distinct effector pathways, and the role of each GAP in negatively modulating the activity of each Ras isoform in myeloid cells and, particularly, mast cells is incompletely understood. In this study, we use murine models of K-ras- and Nf1-deficient mice to examine the role of K-ras in modulating mast cell functions and to identify the role of neurofibromin as a GAP for K-ras in this lineage. We find that K-ras is required for c-kit-mediated mast cell proliferation, survival, migration, and degranulation in vitro and in vivo. Furthermore, the hyperactivation of these cellular functions in Nf1(+/-) mast cells is decreased in a K-ras gene dose-dependent fashion in cells containing mutations in both loci. These findings identify K-ras as a key effector in multiple mast cell functions and identify neurofibromin as a GAP for K-ras in mast cells.

Distribution of CIAPIN1 in normal fetal and adult human tissues

CIAPIN1, a newly identified antiapoptotic molecule that plays an essential role in mouse definitive hematopoiesis, is considered a downstream effector of the receptor tyrosine kinase-Ras signaling pathway. Our previous studies have indicated that CIAPIN1 is involved in the development of multidrug resistance (MDR) in gastric cancer cells. However, the mechanism of CIAPIN1-mediated antiapoptosis and MDR has not been fully elucidated. To reveal the possible physiological role of CIAPIN1, we examined the expression and distribution of CIAPIN1 in fetal and adult human tissues using immunohistochemistry. We found that CIAPIN1 was ubiquitously distributed in fetal and adult tissues, and was localized in both the cytoplasm and the nucleus. The expression patterns of CIAPIN1 were similar in fetal and adult tissues, and was correlated with the previously described expression pattern of p21ras. These observations suggest that CIAPIN1 expression appears to be involved in cell differentiation, and that it might exert universal and possibly important physiological functions under the regulation of Ras in humans.

Endocrine tumours of the gastrointestinal tract: aetiology, molecular pathogenesis and genetics

Endocrine tumours of the gut and pancreas originate from cells of the diffuse endocrine system and are characterised by the production of a wide variety of bioactive substances including growth factors. Two major tumour categories are distinguished-well-differentiated and poorly differentiated neoplasms-with distinct phenotypes and significantly diverse clinical behaviour. Here, genetic background data are summarised on an anatomical basis for tumours of foregut, midgut and hindgut derivatives. For well-differentiated tumours, independent techniques identified the abnormality of multiple chromosomal sites and genes, pointing to a complex genetic background. Differences in foregut tumours compared with midgut and hindgut tumours are, however, outlined. The multiple endocrine neoplasia syndrome type 1 (MEN1) gene is reported to be involved in about one-third of sporadic foregut endocrine tumours and exceptionally in midgut and hindgut tumours. Similarly, X chromosome markers are associated with malignant behaviour in foregut tumours only. For poorly differentiated carcinomas, a high degree of chromosomal instability is the common genetic trait independent of tumour site and frequently involving the p53 gene.

ras oncogene mutations in diethylnitrosamine-induced hepatic tumors in medaka (Oryzias latipes), a teleost fish

Medaka fish are an established non-mammalian research model for the study of liver carcinogenesis and exposure to environmental pollutants. Studies have emphasized the development of hepatic neoplasms in medaka following exposure to model carcinogens. To date however, little information is known regarding the mechanisms underlying initiation of hepatic tumors in this species. The aim of this study was to relate our understanding of diethylnitrosamine (DEN)-induced tumor formation to ras gene activation in hepatic neoplasms of exposed medaka. Initial studies were conducted to identify medaka ras exons 1 and 2 by reverse transcriptase polymerase chain reaction (RT-PCR). Amplification of ras exons 1 and 2 from untreated medaka liver resulted in the identification of three polymorphic ras sequence variants exhibiting a high degree of homology to other teleost and mammalian ras genes. Exposure of medaka to 159 ppm of DEN resulted in a wide range of hepatic neoplasms including: hepatocellular adenomas, hepatocellular carcinomas, cholangiomas, and mixed hepatocholangiocellular carcinomas. Individual liver tumors were examined for oncogenically activating ras mutations by probing genomic DNA with probes specific for activating point mutations or by direct cloning and sequencing of ras transcripts using RT-PCR. Using allele-specific oligonucleotide (ASO) analysis, a single point mutation was detected in codon 12 position two in 8/25 (32%) tumors examined. Mutated ras alleles were additionally detected in 12 of 39 (30%) medaka liver tumors by sequence analysis. Ten of the 12 mutations identified contained a single point mutation at codon 12 resulting in a Gly to Asp amino acid substitution. Two unique mutations were identified at codon 16 resulting in either Lys to Asn or Lys to Thr amino acid substitutions. Our results show that ras mutations are induced by DEN and are present in over 30% of the fish that developed tumors. A ras mutation incidence of 30% is similar to that reported in mammalian species exposed to DEN. While mutations at codon 12 have previously been reported, the present study is the first in vivo report of ras point mutations at codon 16.

Long-term high-level reconstitution of NADPH oxidase activity in murine X-linked chronic granulomatous disease using a bicistronic vector expressing gp91phox and a Delta LNGFR cell surface marker

A murine model of X-linked chronic granulomatous disease (X-CGD), an inherited immune deficiency with absent phagocyte NADPH oxidase activity caused by defects in the gp91(phox) gene, was used to evaluate a bicistronic retroviral vector in which expression of human gp91(phox) and a linked gene for Delta LNGFR, a truncated form of human low-affinity nerve growth factor receptor, are under the control of a spleen focus-forming virus long-terminal repeat (LTR). Four independent cohorts of 11-Gy irradiated X-CGD mice (total, 22 mice) were transplanted with or without preselection of transduced X-CGD bone marrow (BM). Transplanted mice had high-level correction of neutrophil gp91(phox) expression and reconstitution of NADPH oxidase activity. Expression lasted for at least 14 months in primary transplants, and persisted in secondary and tertiary transplants. Both gp91(phox) and Delta LNGFR were detected on circulating granulocytes, lymphocytes, lymphoid, and (for Delta LNGFR) red blood cells. Mice receiving transduced bone marrow [BM] preselected ex vivo for Delta LNGFR expression had high-level (= 80%) reconstitution with transduced cells, with an improved fraction of oxidase-corrected neutrophils posttransplant. Analysis of secondary and tertiary CFU-S showed that silencing of individual provirus integrants can occur even after preselection for Delta LNGFR prior to transplantation, and that persistent provirus expression was associated with multiple integration sites in most cases. No obvious adverse consequences of transgenic protein expression were observed.

Fibroblast activation protein: differential expression and serine protease activity in reactive stromal fibroblasts of melanocytic skin tumors

Growth and metastasis of solid neoplasms require the recruitment of a supporting tumor stroma. A highly consistent trait of tumor stromal fibroblasts in most epithelial cancers is the induction of fibroblast activation protein (FAP), a member of the serine protease family. Recently it was demonstrated that FAP has both dipeptidyl peptidase and collagenolytic activity capable of degrading gelatin and type I collagen. In this study, we describe the expression and enzyme activity of FAP in benign and malignant melanocytic skin tumors. FAP-positive fibroblasts were detected immunohistochemically in the reactive stroma of all melanocytic nevi tested. In primary and metastatic melanomas an upregulation of FAP expression in the reactive mesenchyme could be observed. Whereas 30% of the nevi revealed additional FAP expression on subsets of melanocytic cells, melanoma cells from primary and metastatic melanomas were FAP negative. This may indicate a possible role for FAP in the control of tumor cell growth and proliferation during melanoma carcinogenesis. Consistent with this in vivo expression pattern FAP enzyme activity could be detected by a specific immunocapture assay in extracts of melanocytic nevi and melanoma metastases, whereas no significant activity was detectable in normal adult skin. Strong protein expression of FAP was observed in patterned structures restricted to a subset of the melanoma metastases. Our findings that these FAP-positive structures showed no overlap with endothelial cell surface markers, nor with various melanoma antigens, suggest that FAP is a marker for specific stromal-cell-derived patterns in cutaneous melanoma metastases.

Aberrant G protein signaling in nervous system tumors

Object. Guanosine triphosphate (GTP)—binding proteins, also known as G proteins, play important roles in the regulation of cell growth and differentiation by transmitting intracellular signals from cell surface receptors. In this paper, the authors review G protein signaling in general and its aberrations in four human nervous system tumors.

Methods. In the nervous system, four tumor types have been associated with aberrant G protein signaling. The first tumor type includes astrocytomas, which have increased levels of the activated form of the small G protein, p21-ras, without primary oncogenic p21-ras mutations. The likely source for increased p21-ras activity in sporadically occurring astrocytomas is overexpressed or constitutively activated growth factor receptors, whereas in neurofibromatosis Type 1 (NF1)—associated astrocytomas, the source is a loss of expression of neurofibromin, a major inactivator of p21-ras (ras—GTPase activating protein [GAP]). The second type of tumor associated with aberrant G protein signaling includes sporadic and NF1-associated neurofibromas and malignant peripheral nerve sheath tumors, which also have increased p21-ras activity due to a loss of neurofibromin expression. The third tumor type includes subependymal giant cell astrocytomas as part of the tuberous sclerosis complex (TSC). These tumors display a loss of tuberin expression due to germline mutations in the TSC2 gene. Tuberin functions as an inactivator of the small G protein rap1B (rap1-GAP) and, hence, loss of its expression could lead to increased rap1B activity. In addition to TSC-associated tumors, the authors demonstrate that the majority of sporadically occurring astrocytomas display either loss of tuberin or overexpression of rap1B. This suggests that increased rap1B activity, which can augment p21-ras—mediated signals, also contributes to G protein—mediated aberrant signaling in sporadically occurring astrocytomas. The fourth tumor type includes a significant subset of pituitary adenomas that show constitutive activation of the Gα subunit of the large heterotrimeric Gs protein, which is involved in hormone receptor signaling. The net result of this aberrant activation is increased cyclic adenosine monophosphate and mitogenic tumor-promoting signals.

Conclusions. The authors' review of G protein signaling and aberrations in this process is made with the long-term view that increased understanding of relevant signaling pathways will eventually lead to novel biological targeted therapies against these tumors.

Review of the clinical, histological, and molecular aspects of pancreatic endocrine neoplasms

Pancreatic endocrine neoplasms (PENs) are rare tumors, and little is known about their genetic and chromosomal alterations. Elucidation of the molecular events involved in PEN carcinogenesis has been hindered by the fact that PENs have been considered a single disease entity. The emergence of novel molecular characterization strategies has, however, made it apparent that these lesions exhibit diverse molecular fingerprints, which will facilitate the precise delineation of PEN prognosis, histopathology, and carcinogenesis.

Expression and alteration of ras and p53 proteins in patients with lung carcinoma accompanied by idiopathic pulmonary fibrosis

BACKGROUND

The ras oncogene and the p53 tumor suppressor gene play important roles in the carcinogenic process of lung carcinoma. The authors evaluated whether alterations of the ras and p53 proteins may contribute to the development of lung carcinoma in patients with idiopathic pulmonary fibrosis (IPF) and whether such alterations may explain the high incidence of lung carcinoma among patients with IPF.

METHODS

Lung tissues were obtained from 35 patients who had IPF without complications of lung carcinoma and from 36 patients who had IPF with complications of lung carcinoma. Altered expression of ras and p53 proteins was evaluated by immunohistochemistry, and mutations of both genes were evaluated by polymerase chain reaction-single strand conformation polymorphism and sequencing analyses.

RESULTS

The frequency of expression of ras protein in type II alveolar pneumocytes was significantly greater in lung tissues from patients with IPF who had lung carcinoma compared with lung tissues from patients with IPF who did not have lung carcinoma (75% vs. 40%, respectively; P < 0.01). K-ras point mutation in codon 12 (GGT to GTT transversion) was detected in lung tissue with interstitial pneumonia, in which ras protein was overexpressed in type II alveolar pneumocytes obtained from 2 of 41 patients with IPF complicated by lung carcinoma, causing amino acid substitution (Gly to Val) in both patients. A p53 mutation was detected in three of six lung tissue samples from patients who had IPF lung with positive p53 immunoreactivity, and multiple mutations were detected in two samples.

CONCLUSIONS

Expression of ras protein in type II alveolar pneumocytes and mutation in the codon 12 of K-ras gene in lung tissue may contribute to the induction of lung carcinoma in patients with IPF. Furthermore, the presence of multiple mutations in the p53 gene may explain the high incidence lung carcinoma in patients with IPF.

The IKK-2/Ikappa Balpha /NF-kappa B pathway plays a key role in the regulation of CCR3 and eotaxin-1 in fibroblasts. A critical link to dermatitis in Ikappa Balpha -deficient mice

Tumor necrosis factor (TNF)-alpha-induced phosphorylation of the IkappaB proteins by the IkappaB kinase (IKK) complex containing IKK-2 and subsequent degradation of the IkappaB proteins are prerequisites for NF-kappaB activation, resulting in the stimulation of a variety of pro-inflammatory target genes. The C-C chemokine eotaxin-1 is a potent chemoattractant for eosinophils and Th2 lymphocytes, may play an important role in the pathogenesis of atopic dermatitis, and acts via binding to its receptor CCR3. To investigate the role of NF-kappaB signaling in the regulation of these genes, we stably expressed a transdominant mutant of IkappaBalpha and a constitutively active mutant of IKK-2 in mouse NIH3T3 fibroblasts. The transdominant IkappaBalpha mutant completely inhibited TNF-alpha-mediated induction of both eotaxin-1 and CCR3, whereas expression of constitutively active IKK-2 was sufficient to drive almost full expression of these two genes in the absence of TNF-alpha. Moreover, we observed elevated expression levels of CCR3 and eotaxin-1 protein levels in the skin of IkappaBalpha-deficient mice characterized by a widespread dermatitis. Finally, using dermal fibroblasts derived from IkappaBalpha-deficient mice, we observed elevated basal expression, enhanced inducibility by TNF-alpha, and attenuated down-regulation upon TNF-alpha withdrawal of both CCR3 and eotaxin-1 mRNA levels. These results demonstrate that the IKK-2/IkappaBalpha/NF-kappaB pathway plays a critical role for CCR3 and eotaxin-1 expression in fibroblasts and suggests a critical link to the pathogenesis of atopic dermatitis.

Tumor progression of skin carcinoma cells in vivo promoted by clonal selection, mutagenesis, and autocrine growth regulation by granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor

Tumor microenvironment is crucial for cancer growth and progression as evidenced by reports on the significance of tumor angiogenesis and stromal cells. Using the HaCaT/HaCaT-ras human skin carcinogenesis model, we studied tumor progression from benign tumors to highly malignant squamous cell carcinomas. Progression of tumorigenic HaCaT-ras clones to more aggressive and eventually metastatic phenotypes was reproducibly achieved by their in vivo growth as subcutaneous tumors in nude mice. Their enhanced malignant phenotype was stably maintained in recultured tumor cells that represented, identified by chromosomal analysis, a distinct subpopulation of the parental line. Additional mutagenic effects were apparent in genetic alterations involving chromosomes 11 and 2, and in amplification and overexpression of the H-ras oncogene. Importantly, in vitro clonal selection of benign and malignant cell lines never resulted in late-stage malignant clones, indicating the importance of the in vivo environment in promoting an enhanced malignant phenotype. Independently of their H-ras status, all in vivo-progressed tumor cell lines (five of five) exhibited a constitutive and stable expression of the hematopoietic growth factors granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor, which may function as autocrine/paracrine mediators of tumor progression in vivo. Thus, malignant progression favored by the in vivo microenvironment requires both clonal selection of subpopulations adapted to in vivo growth and mutational events leading to stable functional alterations.

Targeted genomic disruption of H-ras and N-ras, individually or in combination, reveals the dispensability of both loci for mouse growth and development

Mammalian cells harbor three highly homologous and widely expressed members of the ras family (H-ras, N-ras, and K-ras), but it remains unclear whether they play specific or overlapping cellular roles. To gain insight into such functional roles, here we generated and analyzed H-ras null mutant mice, which were then also bred with N-ras knockout animals to ascertain the viability and properties of potential double null mutations in both loci. Mating among heterozygous H-ras(+/-) mice produced H-ras(-/-) offspring with a normal Mendelian pattern of inheritance, indicating that the loss of H-ras did not interfere with embryonic and fetal viability in the uterus. Homozygous mutant H-ras(-/-) mice reached sexual maturity at the same age as their littermates, and both males and females were fertile. Characterization of lymphocyte subsets in the spleen and thymus showed no significant differences between wild-type and H-ras(-/-) mice. Analysis of neuronal markers in the brains of knockout and wild-type H-ras mice showed that disruption of this locus did not impair or alter neuronal development. Breeding between our H-ras mutant animals and previously available N-ras null mutants gave rise to viable double knockout (H-ras(-/-)/N-ras(-/-)) offspring expressing only K-ras genes which grew normally, were fertile, and did not show any obvious phenotype. Interestingly, however, lower-than-expected numbers of adult, double knockout animals were consistently obtained in Mendelian crosses between heterozygous N-ras/H-ras mice. Our results indicate that, as for N-ras, H-ras gene function is dispensable for normal mouse development, growth, fertility, and neuronal development. Additionally, of the three ras genes, K-ras appears to be not only essential but also sufficient for normal mouse development.

Role of Ras and Mapks in TGFbeta signaling

Normal signaling by TGFbeta, in the absence of serum or exogenous factors, involves a rapid activation of Ras, Erks, and Sapks in proliferating cultures of TGFbeta-sensitive untransformed epithelial cells and human carcinoma cells. Expression of either RasN17 or dominant-negative (DN) MKK4, or addition of the MEK1 inhibitor PD98059, can block the ability of TGFbeta to induce AP-1 complex formation at the TGFbeta(1) promoter and to autoinduce its own production. The primary components present in this TGFbeta-stimulated AP-1 complex are JunD and Fra-2, although c-Jun, and possibly Fos B, may also be present. While there are two potential Smad binding elements (SBE's) in the TGFbeta(1) promoter, supershift assays suggest that at least one of these does not bind Smad4, and the other is unable to bind factors activated by TGFbeta. In contrast, TGFbeta autoinduction is Smad3-dependent, as DN Smad3 inhibits the ability of TGFbeta to stimulate TGFbeta(1) promoter activity. Our results indicate that TGFbeta can activate both the MKK4/Sapk and MEK/Erk pathways, through Ras and TGFbeta R(I) and R(II), to induce TGFbeta(1) production; Smad4 does not appear to be involved, and Smad3 appears to function independently of this Smad4. We also demonstrate that activation of the Ras/Mapk pathway by TGFbeta positively modulates Smad1-signaling-pathway activation by TGFbeta. In addition, Smad1 could enhance TGFbeta activation of the SBE reporter SBE-luc and this effect could be blocked by co-expression of a DN TGFbeta R(I) receptor or by the MEK1 inhibitor PD98059. This cross-talk between the MEK/Erk and Smad1 pathways was mediated through the four Erk consensus phosphorylation sites in the linker region of Smad1. Mutation of these sites resulted in a loss of the ligand-dependence of both Smad1-Smad4 interactions and nuclear accumulation of Smad1, as well as a loss of the ability of Smad1 to enhance TGFbeta-mediated SBE activation. Our results provide evidence that Erk-mediated phosphorylation of Smad1 in response to TGFbeta is critical for regulating Smad1 subcellular localization; this may be a key determinant in maintaining TGFbeta-dependent transcriptional activation.

Expression level of inositol trisphosphate and inositol tetrakisphosphate receptors and their influence on Ca2+ release in permeabilized HL-60 and T15 cells

To try to further define the mechanism of action of the putative second messenger inositol 1,3,4,5-tetrakisphosphate (InsP4), we have studied its effects in permeabilized cells expressing different levels of inositol trisphosphate receptor (InsP3R) types I and III and of the GTPase-activating protein GAP1IP4BP. During the growth curve of human HL-60 cells and mouse T15 cells there was an increase in these proteins, which was further increased by differentiation (HL-60) and, marginally, by transformation (T15). T15 cells entering the stationary phase showed much lower concentrations of these proteins and expression was below detection in apoptotic HL-60 cells. Rasp21 showed a different pattern of expression. The ratios of InsP3R subtypes seem to affect the dose-response curve for inositol 2,4,5-trisphosphate Ins(2,4,5)P3. In permeabilized T15 cells the curve was approximately 5-fold to the right of that obtained using HL-60 cells. However, permeabilized untreated and differentiated HL-60 cells and T15 cells all showed a comparable synergistic effect of InsP4 on Ca2+ release stimulated by a concentration of Ins(2,4,5)P3, releasing approximately 20% of the Ins(1,4,5)P3 sensitive Ca2+ pool. The data indicate that under these conditions InsP4 is acting independently of cell type, of the ratio of inositol trisphosphate receptor subtypes, and of the concentration of GAP1IP4BP.

Clinicopathological profile as a basis for classification of the endocrine tumours of the gastroenteropancreatic tract

Recent developments in the field of endocrine cell biology and pathology, at both morphologic and molecular levels, are briefly outlined and discussed as a basis for endocrine tumour characterization. The main clinicopathological tools available for the identification and characterization of endocrine tumours are discussed. Based on this, classifications of endocrine tumours of the pancreas and gastrointestinal tract are developed covering most clinical (hyperfunctional syndromes included), pathologic and biological patterns and with special emphasis on tumour prognosis.

Origin and Genetic Background of Insulinomas

Insulin-producing B cell tumors (insulinomas) are the most frequent functioning endocrine tumors of the pancreas. Available experimental evidence suggests that the islet B cell is the most likely cell of origin of insulinomas, while the duct endocrine cell should be considered if rearrangement of the pancreatic parenchyma occurs. Data on the genetic background of insulinomas suggest that the B cell tumor development may result from alteration of several genes, including the multiple endocrine neoplasia type 1 (MEN1) gene.

K-ras is an essential gene in the mouse with partial functional overlap with N-ras

Mammalian ras genes are thought to be critical in the regulation of cellular proliferation and differentiation and are mutated in approximately 30% of all human tumors. However, N-ras and H-ras are nonessential for mouse development. To characterize the normal role of K-ras in growth and development, we have mutated it by gene targeting in the mouse. On an inbred genetic background, embryos homozygous for this mutation die between 12 and 14 days of gestation, with fetal liver defects and evidence of anemia. Thus, K-ras is the only member of the ras gene family essential for mouse embryogenesis. We have also investigated the effect of multiple mutations within the ras gene family. Most animals lacking N-ras function and heterozygous for the K-ras mutation exhibit abnormal hematopoietic development and die between days 10 and 12 of embryogenesis. Thus, partial functional overlap appears to occur within the ras gene family, but K-ras provides a unique and essential function.

Ras activation in platelets after stimulation of the thrombin receptor, thromboxane A2 receptor or protein kinase C

Several reports have indicated that the small G-protein Ras is not present immunologically in platelets. However, here we report the identification of Ras in platelets by immunoprecipitation with the Ras-specific monoclonal antibodies Y13-259 or Y13-238, followed by Western blotting. The presence of Ras was not due to contamination of samples with erythrocytes or leucocytes. Immunofluorescence studies indicated that Ras was present in a peripheral rim pattern in fixed, permeabilized platelets, suggesting an intracellular, plasma membrane location. Activation of platelets with the thrombin receptor peptide42-50, the prostaglandin H2/thromboxane A2 mimetic U46619 or phorbol 12-myristate 13-acetate induced a rapid increase in GTP-bound, activated Ras. In each case, this increase was inhibited by the protein kinase C (PKC) inhibitor bisindolylmaleimide GF 109203X, suggesting that Ras is activated downstream of PKC in platelets. Thus the activation of Ras in platelets by agonists will now allow consideration of multiple potential Ras-dependent signal transduction pathways in platelet activation processes.

Rapid ras-oncogene-mediated transformation maintains steroidogenic differentiation in adrenocortical parenchymal cells

While its action as a transforming agent is well known, expression of the ras oncogene may also alter tissue-specific differentiation. We have been examining the relationship of transformation and differentiation in steroidogenic cells of the rat. Infection of adrenocortical zona glomerulosa (GLOM) cells with the v-Ki ras containing Kirsten murine sarcoma virus did not induce focus formation. Instead, diffuse cellular multilayers formed from which loosely adherent, refractile cells emerged. After selective passaging these refractile cells, designated KiGLOM, were morphologically transformed, had reduced serum requirements for growth, greatly increased saturation densities, and they rapidly formed tumours in immunosuppressed hosts. In addition, under conditions where normal cells were no longer steroidogenic (ie. after passaging), KiGLOM cells expressed the steroid-specific cholesterol side chain cleavage cytochrome P-450scc and they produced significant, albeit reduced, amounts of corticosterone in comparison with primary GLOM cultures. Additionally, trophic hormone treatment increased steroid production in Ki-GLOM cells and this increase was partially reversed by lovastatin, a pharmacological inhibitor of ras p21 function. Thus, after a morphological selection that removed normal neighbours, v-Ki ras infected cells transformed rapidly while remaining steroidogenic. These results, combined with previous reports of steroidogenic v-Ki ras transformed adrenocortical fibroblasts and ovarian granulosa cells suggest that the ability of the ras oncogene to co-opt signal transduction pathways associated with both growth and differentiation is a common feature of the steroidogenic phenotype.

Review article: The role of oncogenes, tumour suppressor genes and growth factors in oral squamous cell carcinoma: a case of apoptosis versus proliferation

Mutation, deactivation and disregulated expression of oncogenes and tumour-suppressor genes may be involved in the pathogenesis of oral squamous cell carcinoma (SCC). Deactivation of the p53 tumour-suppressor gene allows cell proliferation and blocks apoptosis of malignant oral keratinocytes. Mutation in the ras oncogene results in persistent mitogenic signalling. Upregulatioed c-Myc expression, in the presence of growth factors, provides an additional proliferative signal. Loss of retinoblastoma tumour-suppressor gene (Rb) function may contribute to oral keratinocyte hyperproliferation and recent evidence suggests that simultaneous deactivation of both p53 and Rb is required for tumourigenesis. Enhanced Bcl-2 and reduced Fas expression inhibit tumour cell apoptosis and may convey resistance to cytotoxic drugs and T cell-mediated cytotoxicity, respectively. Exogenous mutagens such as tobacco, alcohol and viral oncogenes may cause altered expression of oncogenes and tumour-suppressor genes in some cases of oral SCC. The impact of these mechanisms on future therapies for oral SCC is highlighted.

Elevated ras p21 expression in oral premalignant lesions and squamous cell carcinoma in Taiwan

Expression of ras p21 oncoproteins was examined in histological sections of oral squamous cell carcinoma (SCC), epithelial dysplasia, epithelial hyperkeratosis and normal oral mucosa using antibodies to ras p21 with an immunoperoxidase technique. Ras p21-positive staining was found in 47 of 51 (92.2%) cases of oral SCC, 4 of 4 (100%) cases of epithelial dysplasia, 7 of 7 (100%) cases of epithelial hyperkeratosis, and 1 of 6 (16.7%) cases of normal oral mucosa. The positive staining rate of ras p21 in oral SCC, epithelial dysplasia or epithelial hyperkeratosis was significantly higher than that in normal oral mucosa (P < 0.05). No correlation was found between ras p21 expression and patient age, tumour location, tumour size, clinical staging or histological differentiation of SCC. However, a significant positive correlation was found between ras p21 expression and patients' sex (P < 0.05) or regional lymph node status (P < 0.05). A significant positive correlation was also discovered between ras p21 expression and patients' smoking habits (P < 0.01), as well as daily or total betel quid (BQ) consumption (P < 0.05). Of the 47 immunostain-positive SCC patients, specimens from 6 patients were also obtained after chemotherapy, when ras p21 expression was found to be reduced. These results indicate that ras p21 overexpression may play an important role in the initiation and progression of oral SCCs in patients who are smokers and BQ chewers.

Immunohistochemical staining of ras p21: staining in benign and malignant prostate tissue

A total of 124 specimens of prostate tissue (25 normal prostate, 41 benign prostatic hyperplasia, 58 adenocarcinoma) was immunostained for ras p21 using a commercially available monoclonal antibody directed against a peptide sequence conserved among all members of the ras gene family. Of normal prostate specimens, 76% showed no staining while the remainder showed only weak epithelial (glandular) staining. No significant stromal staining was noted in any normal prostate specimen. In contrast most benign prostatic hyperplasia specimens showed abundant staining. Epithelial staining was observed in 88% and stromal staining in 73% of specimens. A majority of prostate carcinoma specimens also stained, with 62% and 36% showing epithelial and stromal staining, respectively. No association was noted between staining and either tumor grade or clinical stage. These data argue against any clinical usefulness of immunostaining for ras p21 in the diagnosis or grading of prostate cancer.

GTP-blot analysis of small GTP-binding proteins. The C-terminus is involved in renaturation of blotted proteins

Recombinant c-Ha-ras, ralA and rap2, but not rap1A or rap1B proteins retained their ability to bind [alpha-32P]GTP after SDS/PAGE and transfer to nitrocellulose. Recombinant c-Has-ras missing the C-terminal 23 amino acid residues failed to bind [alpha-32P]GTP after the blot, and the ability of recombinant ralA missing the C-terminal 28 amino acid residues to bind [alpha-32P]GTP was decreased many-fold. The presence of nonionic detergents of the polyoxyethylene type such as Tween 20, Triton X-100, Nonidet P40 or Lubrol PX in the incubation buffer was necessary to induce renaturation of blotted recombinant c-Ha-ras protein, whereas other types of detergents were ineffective. We propose that detergents of the polyoxyethylene type induce the refolding of some types of blotted small GTP-binding proteins and that the C-terminus is involved in the refolding process. Membranes from NIH3T3 fibroblasts overexpressing c-Ha-ras protein showed much weaker binding of [alpha-32P]GTP as expected from the level of ras immunoreactivity. Treatment of fibroblasts with lovastatin, an inhibitor of hydroxymethylglutaryl-coenzyme A reductase, caused the accumulation of the unfarnesylated form of c-Ha-ras in the cytosol. Examination of [alpha-32P]GTP-binding and immunoreactivity for cytosolic and membrane-bound c-Ha-ras revealed that binding of [alpha-32P]GTP to unprocessed c-Ha-ras was increased about threefold compared to the same amount of processed c-Ha-ras. Our results demonstrate that detection and quantification of small GTP-binding proteins in eukaryotic cells by GTP-blot analysis is hampered by the fact that these proteins differ strongly in their ability to renature after blotting to nitrocellulose.

Expression of the erb B oncogene in the Morris hepatoma 7777

Altered expression of protooncogenes/oncogenes is believed to be involved in hepatocarcinogenesis of the chemically induced, transplantable Morris hepatoma 7777. We compared the mRNA expression of c-N-ras and v-erb B mRNA of normal rat liver with that of Morris hepatoma 7777 using Northern blot analysis and in situ hybridization. Northern blot analysis revealed a strong overexpression of the v-erb B related mRNA, while the c-N-ras mRNA was only slightly increased. In situ hybridization using a c-N-ras mRNA probe also showed only a slightly increased number of silver grains in the hepatoma cells compared with normal rat liver. On the other hand, the v-erb B related mRNA was strongly overexpressed in the hepatoma cells, while the connective-tissue capsule, the blood vessels, blood cells and the necrotic foci did not show an elevated v-erb B related gene mRNA expression. Similar results were obtained in liver metastases. The detectable v-erb B hybridization signal was lost by pretreatment with RNase A. We conclude that the c-N-ras gene is of minor importance in the chemically induced, transplantable Morris hepatoma 7777, while the increased expression of the v-erb B related mRNA is due to a selection of ligand-independent tyrosine kinase activity.

Mutations of Ki-ras oncogene codon 12 in betel quid chewing-related human oral squamous cell carcinoma in Taiwan

In Taiwan, there are two million people who have a betel quid chewing habit, and approximately 80% of all oral cancer deaths are associated with this habit. To investigate the incidence and types of Ki-ras codon 12 mutations in oral cancer associated with betel quid chewing, we used a sensitive mutation-specific two-stage polymerase chain reaction (PCR) technique to examine human oral squamous cell carcinomas from formalin-fixed, paraffin-embedded tissues. DNA sequence analysis of PCR products revealed that 6 of 33 (18%) tumour specimens contained Ki-ras codon 12 mutations. Four of the tumours contained more than one mutation. Three different base changes were detected, resulting from a substitution of wild type glycine (GGT) to either serine (AGT), aspartic acid (GAT) or cysteine (TAT). These results indicate that Ki-ras oncogene activation may play a role in the oncogenesis of betel quid chewing-related human oral squamous cell carcinomas.

Analysis of a non-ras 21-kDa protein in patients with metastatic testicular germ-cell tumors

A novel protein of 21 kDa (p21) has been detected in the sera of patients with different solid tumors. The serum levels of this p21 protein were measured in seven patients with metastatic testicular germ-cell tumors before and after chemotherapy using an enzyme-linked immunosorbent assay. In five out of six patients who responded to chemotherapy a concomitant decrease of p21 serum levels was found. The decrease of p21 was in accordance with the decline of the established tumor markers alpha-fetoprotein, human chorionic gonadotropin beta-subunit and lactate dehydrogenase in three patients with non-seminomatous tumors and with the decline of lactate dehydrogenase and the clinical response in two patients with seminoma. In one patient the predicted decline of p21 did not occur despite the patient's clinical response to chemotherapy. In the seventh patient, who relapsed directly after chemotherapy, no decline of either p21 levels or tumor markers was observed. The absolute amount of the p21 protein prior to chemotherapy did not correlate with the patients' tumor burden. Elevated levels of p21 were found in patients with seminomatous and non-seminomatous germ-cell tumors. Since seminoma patients do not secrete tumor markers like alpha-fetoprotein or human chorionic gonadotropin beta, the determination of p21 levels may help to evaluate the efficacy of chemotherapy in patients with seminomatous as well as in patients with marker-negative non-seminomatous germ-cell tumors. The biological role of p21 and its clinical significance will be further investigated.

Role of the rac1 p21-GDP-dissociation inhibitor for rho heterodimer in the activation of the superoxide-forming NADPH oxidase of macrophages

Activation of the superoxide (O2-)-generating NADPH oxidase of phagocytes requires the interaction of membrane-associated cytochrome b559 with three cytosolic components; p47-phox, p67-phox and sigma 1. We proposed that sigma 1 was a heterodimer composed of proteins of 22 kDa and 24 kDa that were tentatively identified as the small GTP-binding protein (G protein) rac1 p21 and GDP-dissociation inhibitor for rho (rho GDI). We now describe a modified procedure for the rapid purification of sigma 1 and demonstrate that the NADPH-oxidase-activating capacity is associated, throughout the purification sequence, with a protein binding 35S-labelled guanosine 5'-[3-O-thio]triphosphate. SDS/PAGE analysis confirmed the absolute association of sigma 1 activity with the presence of both the 22 kDa and 24 kDa proteins. Immunoblotting with a battery of antibodies against the small G proteins demonstrated that the 22-kDa protein was only recognized by antibodies reacting with rac1 p21; no reaction was found with anti-(rac2 p21), anti-[v-ras(H) p21] and anti anti-(rap1 p21). Free rac1 p21 (not in complex with rho GDI) was not detected at any stage of cytosol fractionation. The proteins comprising the sigma 1 heterodimer could be separated by reverse-phase chromatography and amino acid sequencing was performed on peptides derived by trypsin digestion of each of the isolated proteins. This demonstrated the identity of the 22-kDa protein with rac1 p21 and that of the 24-kDa protein with rho GDI. Purified heterodimeric sigma 1 did not require exogenous GTP for activity under conditions that assured the absence of free nucleotides. Treatment of the sigma 1 heterodimer with 1% sodium cholate, followed by gel filtration or anion-exchange chromatography in the presence of 1% sodium cholate, effectively separated rac1 p21 from rho GDI. Monomeric rac1 p21, obtained by these procedures, was able to stimulate cell-free O2- generation. Artificial heterodimeric sigma 1, capable of NADPH oxidase activation, could be reconstituted in vitro by recombining purified monomeric rac1 p21 and rho GDI and removing the sodium cholate used to dissociate the native sigma 1 dimer. Monomeric rac1 p21 exhibited an almost absolute dependence on exogenous GTP following removal of the endogenous nucleotide in low Mg2+ solution. Under similar conditions, heterodimeric sigma 1 was resistant to nucleotide exchange.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunohistochemical analysis of ras oncogene product p21 in human endometrial carcinoma

Monoclonal antibody rp-28 directed against the ras gene product p21 has been used to evaluate ras p21 expression in endometrial lesions. Endometrial cancer showed a variable reactivity according to histological type: in well differentiated adenocarcinoma 63% were positive (12/19); in moderately differentiated adenocarcinoma 53% were positive (8/15); in poorly differentiated adenocarcinoma 40% were positive (2/5). The staining intensity of ras p21 seemed to be stronger in the more differentiated types of endometrial carcinoma. In endometrial carcinoma with premenopausal women, 27% were positive (3/11), and with postmenopausal women 71% were positive (20/28). The difference between premenopausal and postmenopausal groups was statistically significant (Mantel-Haenszel procedure, M-H chi 2 = 6.765, P < 0.01). The results suggest the existence of different carcinogenetic mechanisms in these two groups of endometrial cancer.

Inhibition of human pancreatic cancer cell (MIA PaCa-2) growth by cholera toxin and 8-chloro-cAMP in vitro

The effects of cholera toxin (CT) and 8-chloro-cAMP (8-Cl-cAMP) on cell growth were investigated using two human pancreatic carcinoma cell lines (MIA PaCa-2, Panc-1). CT, which catalyses the ADP ribosylation of Gs, suppresses the proliferation of MIA PaCa-2(PC) cells. CT at the low dose of 0.1 pg ml-1 was inhibitory of PC cell growth, and the maximum suppression (70%) was achieved at a CT concentration of 100 pg ml-1. This phenomenon was reversible. The production of cAMP by CT (100 pg ml-1) in PC cells was enhanced 320-fold compared with the control. In addition, cAMP analogues (8-Cl-cAMP, 8-Br-cAMP) and forskolin decreased the growth rate of PC cells in a dose-dependent manner. These results support the view that CT suppresses PC cell growth by stimulating cAMP production. Conversely, Panc-1 cells were far less sensitive to CT in cell growth and cAMP production. 8-Cl-cAMP was also less effective on Panc-1 cell growth. The binding of an insulin-like growth factor (IGF)-I and transforming growth factor (TGF)-alpha, which has been shown to stimulate PC cell growth in an autocrine manner, to PC cells was not modified in cells treated with CT or 8-Cl-cAMP. The results suggest that the inhibitory actions of these substances do not occur at the level of the receptor for IGF-I or EGF/TGF-alpha. We have previously shown that phorbol esters, which decrease the binding of TGF-alpha to PC cells, has an anti-proliferative activity on these tumour cells. Inhibited cell growth by maximum suppressive dose of CT or 8-Cl-cAMP was further inhibited by TPA. In addition, an oncogene product of K-ras which is commonly activated in pancreatic cancer, was increased by CT and 8-Cl-cAMP. It is concluded that CT and 8-Cl-cAMP inhibit PC cell growth, presumably in a similar manner, and their mechanism(s) of action may be different from that of TPA. The anti-proliferative effect of CT or 8-Cl-cAMP was enhanced by TPA, implying that the combination of these substances results in increased inhibition of the PC cell growth.

Correlation between the expression of oncogenes ras and c-erbB-2 and the biological behavior of bladder tumors

Expression of the ras and the c-erbB-2 oncogene products was investigated in 56 cases of human bladder transitional cell carcinoma and 6 samples of human normal bladder tissue using an immunohistochemical method. Thirty of the 56 cases of bladder tumor were found to be immunohistologically positive with the monoclonal anti-ras p21 antibody, while 19 of 56 cases were positive with the polyclonal anti-c-erbB-2 oncoprotein antibody. All 6 controls were negative with both antibodies. The ras p21 positive staining was found more frequently in the well or moderately differentiated, superficial and non-recurrent tumors than in the poorly differentiated (p < 0.01), muscle invasive (p < 0.05) and recurrent tumors (p < 0.01), while the c-erbB-2 gene product was more commonly detected in high-grade (p < 0.01), invasive (p < 0.01) and recurrent tumors (p < 0.05). Thus, the expression of either ras or c-erbB-2 was closely associated with the histological grade, clinical stage and recurrence of bladder transitional cell carcinomas.

Cell kinetics evaluation of colorectal tumors after in vivo administration of bromodeoxyuridine

Although several biomarkers have been tested, Dukes' (or TNM) stage at diagnosis is still considered the only prognostic factor of clinical relevance in colorectal cancer. Among the various biomarkers, the fraction of cells engaged in DNA synthesis has been extensively investigated as an indicator of tumor aggressiveness. Bromodeoxyuridine (BUdR) is a non-radioactive thymidine analogue which is incorporated into DNA during the S-phase of cycling cells. In order to evaluate the relationships between cell kinetics and morphologic variables, 500 mg of BUdR were given i.v. to 46 patients with colorectal cancer prior to surgery. After operation, a large tumor sample was taken and processed for immunohistochemical detection of BUdR-labeled cells in various regions of the neoplasm and in normal colorectal mucosa. Smaller superficial tumor specimens were also incubated with 3H-thymidine (3H-TdR) for the autoradiographic identification of labeled cells. In the 43 evaluable tumors, the overall BUdR labeling index (BLI, percent of labeled cells) was significantly higher in carcinoma (20.30 +/- 0.86%, SEM) than in normal colonic mucosa (6.51 +/- 0.49%). BLIs in central and peripheral regions of carcinoma were closely correlated (r = 0.48, p = 0.003). In 21 neoplasms a high correlation between overall BUdR and 3H-TdR labeling index in the same tumor was observed (r = 0.57, p = 0.007). No evident association between overall BLI and clinical or morphologic parameters of the tumor was seen, including number of capillaries and ras-p21 protein expression. We conclude that BUdR immunostaining after in vivo administration of BUdR is a simple method for studying cell kinetics in various regions of colorectal cancer. BUdR labeling data are comparable to those obtained with in vitro incorporation of 3H-TdR.

Studies and perspectives of signal transduction in the skin

Tumor-promoting phorbol ester and epidermal growth factor (EGF) exert marked influences on the proliferation and differentiation of keratinocytes. These two agents bring their physiological functions into play via protein kinase C (PKC) activation (and/or down regulation) and protein tyrosine kinase, respectively. In this paper, the present situation in the studies on the signal transduction of keratinocytes centering around these two kinases is discussed. An outline of studies on signal transduction of cells other than keratinocytes in the skin is also given.

Distribution of p21ras in postimplantation rat embryos

Expression of ras cellular oncogenes during the early postimplantation period in the rat was investigated using immunohistochemistry to p21ras. A broad spectrum polyclonal antibody recognizing N-, Ha- and Ki- forms of p21ras was used in an indirect avidin-biotin-peroxidase (ABC) technique. Positive staining indicating the presence of p21ras was found in embryos from 6.5 to 12 days embryonic age. In early egg cylinders (6.5 days), positive staining for p21ras was observed on the ectoplacental cone, primitive ectoderm and trophectoderm, while primitive endoderm and parietal endoderm appeared paler. In later egg cylinder stages (7.5 days), strong positive staining was observed in the primitive embryonic ectoderm and ectoplacental cone, but parietal and visceral endoderm still appeared to be devoid of positive staining. As development proceeded during primitive streak stages, the visceral and parietal endoderm became positively stained. By 10 days, all tissues appeared to be positive for p21ras, with strong staining appearing in the heart and neural elements. Therefore, p21ras does not appear to be ubiquitous in the rat conceptus prior to gastrulation, but shows differential distribution, appearing later in endodermal derivatives. Possibly p21ras is involved in determination of the ectodermal and endodermal lineages.

Prognostic factors in survival of bladder cancer

Clinical and pathologic data of 36 patients with transitional cell carcinoma of the bladder were investigated to determine the significance on patient survival of these factors: pathologic grade and stage; the immunohistochemistry of eight cell and tumor markers; nuclear DNA flow cytometric parameters; and patient smoking status. The bivariate and multivariate statistical analysis significantly correlated patient survival rates with the immunohistochemical expression of blood group, isoantigens A (P less than 0.05), O(H) (P = 0.001), the oncogene-related protein ORP-p21 (P less than 0.05), the pathologic grade and stage (P = 0.002), and the tumor DNA ploidy (P less than 0.05). Smoking status correlated aneuploidy (P less than 0.05) and tumor expression of ORP-p21 (P less than 0.05) with the patient survival rate. Despite the relatively small number of patients in this study, the results suggest that the clinicopathologic variables are significant factors in survival of bladder cancer.

Generation of specific antibodies against the rap1A, rap1B and rap2 small GTP-binding proteins. Analysis of rap and ras proteins in membranes from mammalian cells

Specific antibodies against rap1A and rap1B small GTP-binding proteins were generated by immunization of rabbits with peptides derived from the C-terminus of the processed proteins. Immunoblot analysis of membranes from several mammalian cell lines and human thrombocytes with affinity-purified antibodies against rap1A or rap1B demonstrated the presence of multiple immunoreactive proteins in the 22-23 kDa range, although at strongly varying levels. Whereas both proteins were present in substantial amounts in membranes from myelocytic HL-60, K-562 and HEL cells, they were hardly detectable in membranes from lymphoma U-937 and S49.1 cyc- cells. Membranes from human thrombocytes and 3T3-Swiss Albino fibroblasts showed strong rap1B immunoreactivity, whereas rap1A protein was present in much lower amounts. In the cytosol of HL-60 cells, only small amounts of rap1A and rap1B proteins were detected, unless the cells were treated with lovastatin, an inhibitor of hydroxymethylglutaryl-coenzyme A reductase, suggesting that both proteins are isoprenylated. By comparison with recombinant proteins, the ratio of rap1A/ras proteins in membranes from HL-60 cells was estimated to be about 4:1. An antiserum directed against the C-terminus of rap2 reacted strongly with recombinant rap2, but not with membranes from tested mammalian cells. In conclusion, rap1A and rap1B proteins are distributed differentially among membranes from various mammalian cell types and are isoprenylated in HL-60 cells.