Alternative splicing of the K-ras gene in mouse tissues and cell lines

The mRNA from the K-ras protooncogene is alternatively spliced into 2 transcripts, K-ras4A and K-ras4B, which possess 2 alternative fourth coding exons. In the present study, expression of K-ras4A and K-ras4B transcripts in 8 organs, including heart, brain, spleen, lung, liver, skeletal muscle, kidney, and testis, from BALB/c mice were determined by Northern blot hybridization. K-ras4B, observed in all organs, accounted for approximately 90% to 99% of total K-ras mRNA. K-ras4A was detected only in lung, liver, and kidney. In addition, K-ras expression in lungs and K-ras4A/K-ras4B ratios in lung, liver, spleen, and kidney from A/J, BALB/c, C3H/HeJ, and C57BL/6J mice were determined. A/J lungs expressed K-ras mRNA 2-fold higher than C3H/HeJ or C57BL/6J lungs, whereas K-ras mRNA expression in BALB/c lungs was intermediate. Higher percentages of K-ras4A mRNA were found in lungs and kidneys from A/J and BALB/c mice, as compared with those from C3H/HeJ and C57BL/6J mice. Levels of K-ras4A and K-ras4B mRNAs were also examined in 20 NIH 3T3 cell lines transformed by DNA from spontaneous A/J mouse lung tumors. K-ras4A was expressed 2- to 3-fold higher in these cell lines than in nontransformed NIH 3T3 cells and in C10 cell lines. These results suggest that: (1) there may be functional differences between the protein encoded by K-ras4A and that encoded by K-ras4B in each tissue type, and in tumor cells; and (2) K-ras mRNA expression and K-ras4A/K-ras4B ratios detected in lung tissues from different strains of mice correlate with susceptibility to tumor induction.

Detection of differentially expressed genes in mouse lung adenocarcinomas

Increasing evidence suggests that altered gene expression is associated with the induction and maintenance of malignancy in various organs including mouse lung adenocarcinomas. A competitive cDNA library screening (CCLS) was used to examine gene expression in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung adenocarcinomas from (C3H/HeJ x A/J])F1 mice. Comparisons of RNA expression in lung adenocarcinomas to those of normal surrounding lung tissue revealed altered expression in 220 clones from more than 50,000 clones screened. Fifty clones were selected for quantitative reverse transcriptase-polymerase chain reaction (PCR) analysis to verify altered expression. PCR primers were designed based on partial sequence analysis of the clones. Twenty-two clones were found to be differentially expressed in lung adenocarcinomas compared with normal lungs. GenBank database analysis showed that 14 of the 22 clones were homologous with known genes, whereas 8 clones contained novel sequences. Thirteen clones were down regulated in tumors compared to normal lung tissues, and 9 were overexpressed. The clones underexpressed or absent include adipocyte p27, carbonic anhydrase III, carbonyl reductase, cytochrome CYP2E1, skelemin, myosin, major urinary protein, and contrapsin. Overexpressed clones include Bruton's tyrosine kinase, cyclin D3, poly(A)-binding protein, alpha-fetoprotein, transferrin, and mouse B2 family repetitive sequence. Further examination of biologic implications of the differentially expressed genes in lung adenocarcinomas is necessary to understand their role(s) in mouse lung carcinogenesis.

Chromosome 3p tumor-suppressor gene alterations in cervical carcinomas

Loss of heterozygosity (LOH) on chromosome 3p is a common event in cervical cancer and typically occurs in a dispersed pattern involving several loci. This implies that more than one resident tumor-suppressor gene is involved in the genesis of these tumors; however, specific targets remain to be identified. The region of 3p14.2-pter encompasses a region of frequent loss and contains at least three tumor-suppressor genes: fragile histidine triad (FHIT), transforming growth factor-beta receptor II (T beta R-II), and Von Hippel-Lindau. To identify those loci within 3p14.2-pter that are important in cervical cancer, invasive tumors were first subjected to high-density LOH analysis. With 25 microsatellite markers, LOH was detected in seven of 15 cervical carcinomas (47%). Losses always included markers mapping to 3p22, and markers at this location were exclusively lost in two tumors, implicating this as a site of a cervical tumor-suppressor gene. Because it is a known tumor-suppressor gene located at 3p22 and thus a potential target for inactivation in these tumors, the T beta R-II gene was subsequently screened for mutation and altered expression levels. Whereas no tumor-derived mutations were detected in any of the tumors, six of ten tumors showed T beta R-II transcript levels reduced by > or = 50% when compared with normal cervical epithelium. Nine of 15 (60%) tumors exhibited LOH at 3p22 or reduced expression of T beta R-II, suggesting that reduced T beta R-II levels contribute to cervical tumorigenesis. Two cases exhibited silent germline polymorphisms of T beta R-II: one corresponding to a C1167T transversion and the other to an A1266G transition. The FHIT gene, which is located at 3p14.2, also frequently incurred LOH and abnormal transcription in these tumors. LOH of FHIT was observed in five of the 15 tumors analyzed. Neither mutations nor homozygous deletions of FHIT were detected in the tumors. However, aberrantly short transcripts of the FHIT gene were evident in six of nine (67%) tumors. Only one of these also displayed LOH, indicating that this gene was altered in at least 10 of 15 (67%) tumors. These results provide evidence that the inactivation of two known tumor-suppressor genes, TbetaR-II and FHIT, on chromosome 3p is involved in cervical carcinogenesis. Mol. Carcinog. 30:159--168, 2001.

Inhibition of COX-2 and induction of apoptosis: two determinants of nonsteroidal anti-inflammatory drugs' chemopreventive efficacies in mouse lung tumorigenesis

Recent studies suggested that nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit lung tumorigenesis under conditions that are immunosuppressive. We hypothesized that this inhibition of mouse lung tumorigenesis requires induction of apoptosis and inhibition of COX (cyclooxygenase)-1, COX-2, and the incidence of K-ras mutation. The NSAIDs used in this study include acetylsalicylic acid (ASA) that is anti-inflammatory with COX-1 and COX-2 inhibition and N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS398) that is a specific COX-2 inhibitor. We have previously demonstrated that ASA (147 and 294 mg/kg diet) and NS398 (7 mg/kg diet) inhibited lung tumorigenesis by 31%, 44%, and 34%, respectively, in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-treated A/J mice. No difference in the incidence and types of K-ras mutations was found between the lung tumors treated with NNK and those treated with NNK/ASA and NNK/NS398. In NNK-treated mice, ASA (394 mg/kg diet) or NS398 significantly increased the apoptotic index, from 0.07 to 0.30 or to 0.33, respectively. ASA (294 mg/kg diet) and NS398 also inhibited the expression of COX-2. Finally, modulation of gene expression by NS398 and ASA (294 mg/kg diet) was determined using Atlas cDNA expression arrays. Expression of cyclin B2 was decreased and expression of Fas-L and BAD were increased in lung tissues treated with both NS398 and ASA. Treatment with NS398 also increased expression of p57kip2 and myosin. These genes modulated by NSAIDs may play a role in mediating the observed chemopreventive effects of the NSAIDs in the mouse lung. Our results demonstrate that lung tumor prevention with NSAIDs involve both the induction of apoptosis and the inhibition of COX-2 expression.

Chemopreventive efficacy of promising farnesyltransferase inhibitors

The studies presented were designed to test the efficacy of farnesyltransferase inhibitors (FTIs) as potential chemopreventive compounds in the mouse lung tumor model, and in tumor cell lines. The compounds included manumycin, gliotoxin, dihydroepiandrosterone (DHEA), perillyl alcohol (POH), and FTI-276. Each of these compounds had the potential, based on in vitro and limited in vivo evidence, to inhibit mouse lung tumorigenesis. In vitro studies were conducted with both K-ras-transformed NIH-3T3 cells and mouse lung tumor epithelial cell lines. We utilized 2 primary mouse lung tumor models that reliably produce lung tumors with an oncogenic K-ras mutation when induded by 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK). Manumycin, gliotoxin, DHEA, and POH were administered 3 times per week peritoneally (i.p.), starting 1 week prior to carcinogen treatment, and throughout the test period (4.5 months). FTI-276 was delivered daily for 4 months by a time-release pellet method. Both the manumycin and gliotoxin treatment groups demonstrated 100% incidence and an increase in tumor multiplicity over control, of 66% and 58% increase respectively (P < .05). Although DHEA showed no significant chemopreventive effect, POH treatment demonstrated a 22% reduction in tumor incidence (P < .05) and a 58% reduction in tumor multiplicity (P < .05). Finally, FTI-276 reduced both the tumor multiplicity by 41.7% (P < .005), and the total tumor volume/burden per mouse by 79.4% (P < .0001). The apoptotic index in FTI-276-treated tumors showed an increase of 77% over control tumors (P < .05). In vitro, all compounds demonstrated growth inhibition at a dose-response manner; however, manumycin, gliotoxin, and DHEA demonstrated an initial increase in growth rate at lower doses. In summary, we have shown that POH and FTI-276 are chemopreventive in a primary mouse lung tumor model. In contrast, DHEA was not significantly chemopreventive at the dosage utilized, and treatment of an immunocompetent host with manumycin or gliotoxin demonstrated a significant increase in tumorigenicity over carcinogen control.

Use of p53 transgenic mice in the development of cancer models for multiple purposes

The tumor suppressor gene p53 is perhaps the most commonly mutated gene in human cancer, being mutated in a high percentage of colon, breast, skin, bladder, and many cancers of the aerodigestive tract. Individuals with Li-Fraumeni syndrome, who routinely have a germline mutation in the p53 tumor suppressor gene, are at high risk for lung cancer, confirming its intimate role in lung tumorigenesis in humans. In contrast, the majority of chemically induced or spontaneous cancers in rodents do not contain mutations in p53. Therefore, we examined a transgenic mouse that contains a dominant negative mutation (Arg135Val) in the p53 gene placed under the control of its own endogenous promoter. The resulting mice have 3 copies of the mutated transgene as well as 2 normal p53 alleles. In the chemical carcinogenesis studies, we employed mice containing the mutated p53 gene to examine for carcinogen susceptibility. We found that mice with the p53 mutation, on an A/J F1 background, were more susceptible to a number of potential lung carcinogens, including N-methyl-N-nitrosourea (MNU) and the known tobacco carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo(a)pyrene (BP). Mice with a mutant p53 developed larger tumors and roughly 3 times as many tumors, emphasizing the potential effects of a p53 mutation both on tumor initiation and progression. In addition, we examined 2 nonlung carcinogens, 1,2-dimethylhydrazine (DMH), a colon carcinogen, and N-butyl-N-(4-hydroxybutyl)-nitrosamine (OHBBN), a bladder carcinogen. Interestingly a germline p53 mutation increased the incidence of DMH-induced colon, lung, hepatic, and uterine tumors, while having limited effects on OHBBN-induced bladder tumors. Because of its heightened susceptibility we are examining the use of this model in smoke-induced tumorigenesis in A/J mice as well. Employing the lung adenomas induced by NNK, we found that mice with or without a p53 mutation were equally susceptible to the chemopreventive effects of dexamethasone plus myo-inisitol and green tea. These tumors, which arise in a highly reproducible manner in p53 transgenic mice following carcinogen treatment, have mutations in both p53 and the K-ras oncogene. Thus, this model appears useful for examining for potential chemotherapeutic agents. p53-mutated or wild-type mice were equally susceptible to the therapeutic effects of Taxol or Adriamycin. Interestingly, piroxicam was similarly effective in inhibiting colon tumor formation by DMH in mice with or without a mutation in the p53 tumor suppressor gene. In contrast, lung and uterine tumors developing in these mice were not susceptible to the chemopreventive effects of piroxicam. In summary, mice with mutations in the p53 tumor suppressor gene appear to be particularly applicable for basic mechanistic studies, for screening for potential carcinogens, and for screening for chemopreventive or chemotherapeutic agents.

Detection of genetic alterations in mouse lung adenocarcinomas by two-dimensional gel electrophoresis

DNA from 14 mouse lung adenocarcinomas and 7 normal lungs were examined by 2-dimensional gel electrophoresis (2-DGE) for genetic alterations. 2-DGE profiles from tumor samples were compared with those profiles from normal lung tissues through a computer-assisted color overlay system. Compared to the profiles in normal lung DNA, 6 spots were amplified and 16 spots were partially reduced in their intensity in tumors. Two spots were detectable only in tumor tissues. These altered spots indicate genetic changes in mouse lung tumor development. The identification of these genetic alterations is probably important in understanding mouse lung carcinogenesis.

Fine mapping and characterization of candidate lung tumor resistance genes for the Par2 locus on mouse chromosome 18

In a number of recent studies, a lung tumor resistance locus designated either Par2 or Pas7 was mapped to distal chromosome 18 in crosses between susceptible A/J and more resistant BALB/c mice. This locus is important in that it accounts for as much as 60% of the difference in lung tumor susceptibility between the A/J and BALB/c mice, both of which contain the susceptible allele of Kras2, a marker and strong candidate for the major lung tumor susceptibility gene on mouse chromosome 6. We have now fine-mapped the Par2 locus by using congenic mice that were constructed by placing part of chromosome 18 from the susceptible A/J onto the genetic background of lung tumor-resistant BALB/c mice. After 7 generations of backcrossing, N7 mice that carried 28 cM of the A/J quantitative trait locus (QTL) region were crossed to the BALB/c to generate the N8 generation. Congenic strains (N8) that contain various QTL regions were generated. N9 mice, generated from N8 males x 3 BALB/c females, were genotyped in the region of the Par2 locus and treated with an initiating dose of urethane and allowed to form lung tumors over 6 months. The mice were killed and the lung tumors counted. With this cross the Par2 locus was narrowed to a 6-cM region. Potential candidate genes in this region include Smad4, Smad2, and Dcc. Previously, we excluded Smad4 and Smad2 as candidates for Par2 based on the lack of functional polymorphism(s) and differential expression in lungs from A/J and BALB/c mice. In this study, no polymorphism of the coding sequence of Dcc was observed between A/J and BALB/c mice. Further fine mapping and positional cloning are required for the identification of the Par2 gene.

[Arthropod diversity in leafy vegetable field and sampling technology]

Two sampling units (plant and quadrat) and two sampling methods (random and fixed) were adopted to compare the variation degree of the diversity of arthropod communities in different chinese cabbage fields. The results show that a lower variation degree was found when the random sampling method was adopted with quadrat (0.11 m2) as sampling unit at seedling stage and with plant as sampling unit from growing to mature stage. The community diversity was relatively steady, when the critical number of samples was more than 12 quatrats (0.11 m2) at seedling stage, 30 plants in growing period, and 20 plants at mature stage. The optimum sampling unit, sampling method and sampling number of arthropod diversity in leafy vegetable field were also determined.

Bcl-2 and Bax are differentially expressed in hyperplastic, premalignant, and malignant lesions of mammary carcinogenesis

Previously, we found that vorozole (Vz), a nonsteroidal aromatase inhibitor, suppresses the development and progression of mammary tumors in rats. Here we evaluated for the first time the expression of cell death-related proteins Bcl-2 and Bax in hyperplastic, premalignant (carcinoma in situ), or malignant (carcinoma) lesions of mammary carcinogenesis; we also assessed whether these proteins are involved in mediating Vz-induced cell death in tumors. We found that Bcl-2 and Bax were equally expressed in epithelial cells of terminal end buds, ducts, and alveoli. However, in myoepithelial cells, the level of Bax expression was much higher than the level of Bcl-2 expression. Bcl-2 and Bax levels in hyperplastic lesions were similar to those of normal mammary epithelial cells but lower in most carcinomas in situ and carcinomas. In animals with established mammary tumors, Vz induced apoptotic cell death, which was primarily associated with a decrease in Bcl-2 and, to a lesser extent, with a decrease in Bax. These data support the hypothesis that Bcl-2 loss is more potent than Bax gain in regulating apoptotic cell death in mammary tumors.

Role and regulation of Rel/NF-kappaB activity in anti-immunoglobulin-induced apoptosis in WEHI-231 B lymphoma cells

In WEHI-231 cells, anti-immunoglobulin (anti-Ig) treatment leads to both a decrease in the DNA-binding activity of p50/c-Rel/p53 protein complexes and a transient enhancement in the DNA-binding activity of p50 homodimeric complexes. These cells subsequently undergo apoptosis. Because IkappaB-alpha plays a pivotal role in the regulation of Rel/NF-kappaB activity, we have characterized both the nature and kinetics of the expression of IkappaB-alpha following anti-Ig-induced apoptosis in WEHI-231 cells. Anti-Ig treatment of WEHI-231 cells decreased the steady-state level of IkappaB-alpha mRNA, but enhanced the stability of IkappaB-alpha, leading to an accumulation of IkappaB-alpha in both the cytosol and nucleus. Concomitant with the increase in IkappaB-alpha expression there was a gradual decline in the nuclear expression of c-Rel. Because c-Rel plays an important role in the survival of WEHI-231 cells, these results suggest that post-transcriptional regulation of IkappaB-alpha expression might play a role in the anti-Ig-induced apoptosis in WEHI-231 cells.

A germ-line p53 mutation accelerates pulmonary tumorigenesis: p53-independent efficacy of chemopreventive agents green tea or dexamethasone/myo-inositol and chemotherapeutic agents taxol or adriamycin

Recent evidence indicates that individuals with a p53 germ-line mutation (Li-Fraumeni syndrome) have a 50% risk of developing lung cancer by age 60. In this study, p53 heterozygous knockout mice and p53 transgenic mice carrying a dominant negative mutant were crossed with the A/J mouse, which is highly susceptible to lung tumor induction, to investigate whether a p53 germ-line mutation is a predisposing gene for carcinogen-induced pulmonary adenomas in mice. The number of lung tumors was not significantly increased in (TSG-p53 x A/J)F1 p53 heterozygous knockout mice as compared with that in (TSG-p53 x A/J)F1 wt mice 16 weeks after exposure to N-nitrosomethylurea (MNU). In contrast, an average of 22 lung tumors were observed in (UL53-3 x A/J)F1 mice carrying a mutant p53 transgene (135Valp53) compared with an average of 7 lung tumors seen in (UL53-3 x A/J)F1 wt mice after treatment with N-nitrosomethylurea. Similar enhancement of lung tumor multiplicity (approximately 3-fold) was seen when mutant versus wt mice were treated with the tobacco-related carcinogens benzo[a]pyrene or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. These results suggest that the mutant p53 transgene may have a dominant negative effect on the wt p53. The potential usefulness of this new mouse model in lung cancer chemoprevention and chemotherapy was examined. The chemopreventive efficacy of the green tea or a combination of dietary dexamethasone and myoinositol and the chemotherapeutic efficacy of Taxol or Adriamycin was examined in wt mice or mice with a mutation in the p53 gene. Mice treated with dexamethasone/myo-inositol and green tea displayed an average of 70 and 50% inhibition of lung tumors, respectively, regardless of p53 status. Similarly, when mice bearing established lung adenomas were treated with Taxol or Adriamycin, a decrease in tumor volume of approximately 70% was observed independent of p53 mutation status. Thus, the (UL53-3 x A/J)F1 p53 transgenic mouse seems to be an excellent model for human carriers of p53 germ-line mutations (Li-Fraumeni syndrome). Furthermore, the lung adenomas generated in this model possess mutations in both the K-ras proto-oncogene and the p53 tumor suppressor gene. This model should prove directly useful for chemoprevention and chemotherapy studies.

Effect of farnesyltransferase inhibitor FTI-276 on established lung adenomas from A/J mice induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone

The Ras protein undergoes a series of post-translational modifications at the C-terminal CAAX motif, which culminates with the anchoring of p21 Ras to the plasma membrane where it relays growth regulatory signals from receptor tyrosine kinases to various pathways of cell signal transduction. FTI-276 is a CAAX peptidomimetic of the carboxyl terminal of Ras proteins. Pharmacokinetic analysis of FTI-276 in A/J mice with a time-release pellet system showed a dose of 50 mg/kg body wt achieved an average serum level of 1.68 microg/ml for up to 30 days following implantation. In the present study, 4 week old A/J mice were initiated with a single dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (100 mg/kg), and monitored for 18 weeks. Mice were grouped for daily delivery (time-release pellet) of 50 mg/kg of FTI-276 for 30 days (n = 12) and the control group (n = 12). Analysis of tumors from time-release pellet treated animals showed a 60% reduction in tumor multiplicity and a 42% reduction in tumor incidence. Moreover, FTI-276 treatment resulted in a significant reduction in tumor volume (approximately 58%). Mutation analysis of the lung tumors from both treatment groups revealed that most of the tumors harbored mutations in the codon 12 of K-ras and there is no significant difference in the incidence and types of mutations between tumors from the treated and control animals. This is the first demonstration of chemotherapeutic efficacy of a synthetic CAAX peptidomimetic farnesyltransferase inhibitor in a primary lung tumor model.

Small molecule antagonists of the bradykinin B1 receptor

Screening Pharmacopeia's encoded combinatorial libraries has led to the identification of potent, selective, competitive antagonists at the bradykinin B1 receptor. Libraries were screened using a displacement assay of [3H]-des-Arglo-kallidin ([3H]-dAK) at IMR-90 cells expressing an endogenous human B1 receptor (Bmax = 20,000 receptors/cell, K(D) = 0.5+/-0.1 nM) or against membranes from 293E cells expressing a recombinant human B1 receptor (Bmax = 8,000 receptors/cell, K(D) = 0.5 +/- 0.3 nM). Compound PS020990, an optimized, representative member from the class of compounds, inhibits specific binding of 3H-dAK at IMR-90 cells with a KI of 6 +/- 1 nM. The compound inhibits dAK-induced phosphatidyl inositol turnover (K(Bapp) = 0.4 +/- 0.2 nM) and calcium mobilization (K(Bapp) = 17 +/- 2 nM) in IMR-90 cells. Compounds from the lead series are inactive at the B2 receptor and are > 1000-fold specific for B1 vs. a variety of other receptors, ion channels and enzymes. PS020990 and other related chemotypes therefore offer an excellent opportunity to explore further the role of B1 receptors in disease models and represent a potential therapeutic avenue.

Cdkn2a encodes functional variation of p16INK4a but not p19ARF, which confers selection in mouse lung tumorigenesis

The cyclin-dependent kinase inhibitor 2a (Cdkn2a) locus encodes two distinct tumor suppressors, p16INK4a and p19ARF, whose functions interrelate in the regulation of cell proliferation as key components of the retinoblastoma and p53 pathways, respectively. In many types of cancer, alterations of Cdkn2a abrogate the functions of both suppressors, implying that both are integral to the genesis of certain cancer types. While this has been observed in mouse lung adenocarcinogenesis, recent observations also suggested that naturally occurring variation at the Cdkn2a locus is probably operative in the development of these tumors. Firstly, two common haplotypes of mouse Cdkn2a have been identified, each of which encodes cosegregating variants of p16INK4a and p19ARF. The p16INK4a variants differ at amino acids 18 (histidine or proline) and 51 (valine or isoleucine), whereas the p19ARF variants differ only at amino acid 72 (histidine or arginine). Secondly, genetic resistance to lung tumor formation appears to segregate with one particular haplotype, which also is deleted preferentially in lung adenocarcinomas of Cdkn2a heterozygous mice. Here we attempt to explain these observations and to characterize further the roles of p16INK4 and p19ARF in mouse lung tumorigenesis by examining the function and expression of each of the variants of Cdkn2a. Functional analysis showed that the proline 18/isoleucine 51 p16INK4a variant was diminished in cdk6 binding, cdk6 inhibition and NIH/3T3 fibroblast growth suppression compared with the histidine 18/valine 51 variant, whereas both of the p19ARF variants suppressed growth with similar potencies. Also, the different alleles for p16INK4a and p19ARF were transcribed equally in the normal lungs of Cdkn2a heterozygotes, as determined by comparative reverse transcription-polymerase chain reaction-single-stranded conformation polymorphism analysis. These results indicate that strain-specific variation in p16INK4a function is exploited in mouse lung tumorigenesis and strongly implicate a role for p16INK4a in lung cancer predisposition and development.

Shp-2 tyrosine phosphatase functions as a negative regulator of the interferon-stimulated Jak/STAT pathway

Shp-2 is an SH2 domain-containing protein tyrosine phosphatase. Although the mechanism remains to be defined, substantial experimental data suggest that Shp-2 is primarily a positive regulator in cell growth and development. We present evidence here that Shp-2, while acting to promote mitogenic signals, also functions as a negative effector in interferon (IFN)-induced growth-inhibitory and apoptotic pathways. Treatment of mouse fibroblast cells lacking a functional Shp-2 with IFN-alpha or IFN-gamma resulted in an augmented suppression of cell viability compared to that of wild-type cells. To dissect the molecular mechanism, we examined IFN-induced activation of signal transducers and activators of transcription (STATs) by electrophoretic mobility shift assay, using a specific DNA probe (hSIE). The amounts of STAT proteins bound to hSIE upon IFN-alpha or IFN-gamma stimulation were significantly increased in Shp-2(-/-) cells. Consistently, tyrosine phosphorylation levels of Stat1 upon IFN-gamma treatment and, to a lesser extent, upon IFN-alpha stimulation were markedly elevated in mutant cells. Furthermore, IFN-gamma induced a higher level of caspase 1 expression in Shp-2(-/-) cells than in wild-type cells. Reintroduction of wild-type Shp-2 protein reversed the hypersensitivity of Shp-2(-/-) fibroblasts to the cytotoxic effect of IFN-alpha and IFN-gamma. Excessive activation of STATs by IFNs was also diminished in mutant cells in which Shp-2 had been reintroduced. Together, these results establish that Shp-2 functions as a negative regulator of the Jak/STAT pathway. We propose that Shp-2 acts to promote cell growth and survival through two mechanisms, i.e., the stimulation of growth factor-initiated mitogenic pathways and the suppression of cytotoxic effect elicited by cytokines, such as IFNs.

5-Aza-2'-deoxycytidine is chemopreventive in a 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone-induced primary mouse lung tumor model

Carcinogenesis is a multistep process in which many alterations in both genetic and epigenetic controls lead to a growth advantage for neoplastic cells. Hypermethylation has been established as the basis of genomic imprinting, but recent studies have also shown that alterations in genomic methylation patterns may contribute to tumorigenesis. The chemical 5-aza-2'-deoxycytidine (5-aza-dC) has been used both in vitro and in vivo to inhibit DNA methylation. In this study, we investigated the chemopreventive efficacy of 5-aza-dC in a well-established primary mouse lung tumor model. Five-week-old male (C3H/HeJ x A/J) F1 hybrid mice were treated for 24 consecutive weeks with 5-aza-dC, three times per week i.p. Lung tumors were induced with two consecutive weekly doses of 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone starting 1 week after initial treatment with 5-aza-dC. We demonstrated that 5-aza-dC exhibits a chemopreventive effect in this primary mouse lung tumor model which, like human lung adenocarcinomas, harbors an activating K-ras mutation. Treatment with 5-aza-dC resulted in a 23% reduction in tumor incidence, as well as a 42% reduction in tumor multiplicity. This work supports further investigation of methylation inhibitors likes 5-aza-dC for early intervention, prevention and treatment of lung cancer.

Identification of v-Rel oncogene-induced inhibitor of apoptosis by differential display

The v-Rel oncoprotein is a member of the Rel/NF-kappaB family of transcription factors. v-Rel induces oncogenic transformation and inhibits apoptosis. To identify aberrantly expressed cellular genes in v-Rel transformed cells, gene expression patterns in normal and v-Rel transformed cells were compared by mRNA differential display. Northern blotting analysis with radiolabeled cDNAs from differential display confirmed the reproducible differential expression of 10 transcripts in v-Rel transformed cells. One of the identified genes, termed ch-IAP1, encodes a chicken homolog of the inhibitor-of-apoptosis protein (IAP) family. ch-IAP1 contains N-terminal baculovirus IAP repeats (BIR), the hallmark of IAPs, and has a C-terminal RING finger motif commonly present in the other IAPs. Like other IAPs, ch-IAP1 is expressed predominantly in the cytoplasm of cells. ch-IAP1 is highly expressed in v-Rel transformed fibroblasts, B- and T-cell lines, and spleen cell lines. In contrast, ch-IAP1 expression levels were low in chicken cell lines transformed by several other unrelated tumor viruses. Additionally, ch-IAP1 expression is downregulated in temperature-sensitive (ts) v-Rel transformed spleen cells at the nonpermissive temperature. Overexpression of the full-length ch-IAP1 suppresses mammalian cell apoptosis induced by the interleukin-1-converting enzyme (ICE), a member of the mammalian caspase family of cysteine proteases. Furthermore, expression of exogenous ch-IAP1 inhibits apoptosis of ts v-Rel transformed spleen cells at the nonpermissive temperature.

MR findings in isolated oculomotor nerve palsy associated with infectious mononucleosis caused by Epstein-Barr virus infection

A 20-year-old man presented with fever, bilateral swelling of the cervical and inguinal lymph nodes, and splenomegaly. Later he noted diplopia. CSF was unremarkable. High serum antibodies to Epstein-Barr virus (EBV) were discovered. MRI revealed an abnormal lesion in the right third cranial nerve, which was considered to be the pathological lesion associated with his clinically apparent oculomotor nerve dysfunction.

At least four loci and gender are associated with susceptibility to the chemical induction of lung adenomas in A/J x BALB/c mice

Four putative quantitative trait loci (QTLs) that influence susceptibility to the induction of lung adenomas by urethane in an F2 cross between A/J and BALB/cOlaHsd have been mapped. Following microsatellite typing of mice with resistant and susceptible phenotypes at 97 microsatellite marker loci, a major locus was identified on chromosome 18 with a lod score of 15. This was responsible for an 8- to 10-fold increase in tumor multiplicity in males and females, respectively, having the AA and CC genotypes at the D18Mit188 marker locus. It mapped close to Dcc (deleted in colorectal cancer). A locus on chromosome 4 (lod score 6.5) had the resistant allele in strain A/J and the susceptible allele in BALB/c, with a 14-fold difference in tumor multiplicity between mice of the AA and CC genotypes. This mapped close to the Cdkn2a (cyclin-dependent kinase inhibitor 2A) locus, which is commonly deleted in mouse lung tumors. Two loci with smaller effects (lod scores 3.03 and 3.25) were identified on chromosomes 1 and 11. There was also significant sexual dimorphism in tumor multiplicity both among 151 F2 hybrids and among 52 mice resulting from a backcross to strain A/J, with males having higher tumor counts than females.

Preclinical and clinical models of lung cancer chemoprevention

In smokers, beta-carotene, retinol, and vitamins E and C appear to have little or a negative effect against human lung cancer development. Similarly, these chemicals have generally failed to inhibit lung tumorigenesis in rodents. The agents that have been shown to inhibit lung tumorigenesis in rodents, such as glucocorticoids, green tea, NSAIDs, and isothiocyanates, have not been tested yet in humans. These agents may be more effective in preventing human lung cancer in smokers than are the chemicals tested so far, especially if they are delivered by inhalation route.

Synergistic activation of MAP kinase (ERK1/2) by erythropoietin and stem cell factor is essential for expanded erythropoiesis

Stem cell factor (SCF) and erythropoietin (EPO) work synergistically to support erythropoiesis, but the mechanism for this synergism is unknown. By using purified human erythroid colony-forming cells (ECFC), we have found that SCF and EPO synergistically activate MAP kinase (MAPK, ERK1/2), which correlates with the cell growth and thus may be responsible for the synergistic effects. Treatment of the cells with PD98059 and wortmannin, inhibitors of MEK and PI-3 kinase, respectively, inhibited the synergistic activation of MAPK and also the cell growth, further supporting this conclusion. Wortmannin only inhibits MAPK activation induced by EPO but not that by SCF, suggesting that SCF and EPO may activate MAPK through different pathways, which would facilitate synergy. Furthermore, EPO, but not SCF, led to activation of STAT5, whereas SCF and wortmannin had no effect on the EPO-induced STAT5 activation, suggesting that STAT5 is not involved in the synergistic action of SCF and EPO. Together, the data suggest that synergistic activation of MAPK by SCF and EPO is essential for expanded erythropoiesis.

Chemopreventive effects of the aromatase inhibitor vorozole (R 83842) in the methylnitrosourea-induced mammary cancer model

The chemopreventive activity of the highly specific nonsteroidal aromatase inhibitor, vorozole, was examined in the methylnitrosourea (MNU)-induced rat model of mammary carcinogenesis. Various doses of vorozole (0.08-1.25 mg/kg body wt/day) were administered daily (by gavage) to female Sprague-Dawley rats starting at 43 days of age. Seven days later, the rats were given a single i.v. dose of MNU (50 mg/kg body wt). Rats were continually treated with vorozole until the end of the experiment (120 days post-MNU). Vorozole caused a dose dependent inhibition of mammary cancer multiplicity. The highest dose of vorozole (1.25 mg/kg body wt/day) decreased cancer multiplicity by approximately 90%, and simultaneously decreased cancer incidence from 100 to 44%. The next two highest doses of vorozole (0.63 and 0.31 mg/kg body wt/day) inhibited MNU-induced mammary cancer multiplicity by 70-80%. Even the two lowest doses of vorozole (0.16 and 0.08 mg/kg body wt/ day) decreased cancer multiplicity -50%. Serum level determinations were performed on a variety of endpoints at either 4 or 24 h following the last dose of vorozole. Insulin-like growth factor (IGF)-1 levels were slightly, but significantly, increased by vorozole treatment. Vorozole induced striking increases in serum testosterone levels at 4 h at all the dose levels employed. Testosterone levels were significantly elevated over controls at 24 h in rats given the lower doses of vorozole (0.08-0.31 mg/kg body wt/day), but were significantly lower than in rats administered the higher doses of vorozole (0.63 or 1.25 mg/kg body wt/ day). This result presumably reflects the limited half-life of vorozole in rats. In a second series of experiments, the effects of limited duration of dosing with vorozole (2.5 mg/kg body wt/day) or intermittent dosing with vorozole were determined. Treatment of rats with vorozole for limited time periods, from 3 days post-MNU administration until 30 or 60 days post-MNU treatment, resulted in significant delays in the time to appearance of palpable cancers. However, these limited treatments did not greatly affect the overall incidence or multiplicity of mammary cancers when compared with the MNU controls at the end of the study (150 days post-MNU). Finally, the effects of intermittent dosing with vorozole (2.5 mg/kg body wt/day) were examined. Rats were administered cycles of vorozole daily for a period of 3 weeks followed by treatment with the vorozole vehicle for the next 3 weeks (total of four cycles). Although this intermittent treatment did inhibit the appearance of new tumors during each of the periods that vorozole was administered, it did not cause regression of palpable cancers.

Additional evidence that the K-ras protooncogene is a candidate for the major mouse pulmonary adenoma susceptibility (Pas-1) gene

A locus for mouse pulmonary adenoma susceptibility, Pas-1, has been mapped on distal chromosome 6, where the K-ras gene is located. Allele-specific activation and expression of the K-ras allele from the susceptible parent has been observed in lung tumors from F1 hybrid mice. We report here genetic mapping of lung tumor susceptibility genes in urethane-treated A x B and B x A recombinant inbred (RI) mice using microsatellite markers to seek further evidence for the K-ras gene as candidate for Pas-1. The K-ras genotype differs between the A/J and C57BL/6J progenitors of the RI strains, and distal chromosome 6 contained a major lung tumor susceptibility determinant in the RI mice. Additional evidence that Pas-1 is K-ras involved linkage analysis of (A/JOLaHsd x BALB/ cOLaHsd) F2 intercross mice whose parents shared the same K-ras genotype. In contrast to the results with the A x B and B x A RI strains, no distal chromosome 6 site was significantly associated with tumor development in these F2 mice. In addition to this major locus, linkage analysis of the RI mice revealed additional quantitative trait loci for susceptibility on chromosomes 10, 17, and 19. These loci may serve as modifiers of Pas-1. The relationship between the K-ras genotype and the frequency of K-ras mutations in urethane-induced lung tumors from the RI mice was also explored. All 18 tumor DNAs from RI mice with high susceptibility contained an AT-->TA transversion at the second base of K-ras codon 61. This was also true for DNAs from 27 of 27 (100%) tumors in mice with high intermediate susceptibility. In RI strains with a low intermediate susceptibility, the DNA from 39 of 47 (83%) tumors contained an AT-->TA transversion at codon 61, and only 13 of 21 (62%) tumors had this mutation in the most resistant group. This reflects a positive correlation between the frequency of K-ras mutations in lung tumors of A x B or B x A RI strains and their susceptibility to lung carcinogenesis. Since K-ras appears to be Pas-1, these results suggest that some RI mice that have the resistant K-ras or Pas-1 allele undergo tumor development by a K-ras-independent route.

Expression of cell cycle proteins in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced mouse lung tumors

Cyclin D1 dysregulation and differential inactivation of p16INK4a and Rb have been observed in human lung cancer. In chemically induced mouse lung tumors, the p16INK4a gene is a target of inactivation, and Rb is reduced at the mRNA level (Northern blot) although similar at the protein level (Western blot) when compared to normal lung tissues. The expression of cyclin D1, cdk4, p16INK4a, and Rb protein was examined by immunohistochemistry in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse lung tumors. Immunohistochemical staining revealed exclusive nuclear staining of both cyclin D1 and cdk4 that was light to moderate in normal mouse lung tissues, but intense in lung adenomas and adenocarcinomas. Western blot analysis confirmed the increased expression of cyclin D1 and cdk4 in lung tumors compared to normal lung. Immunohistochemical analyses of lung tumors showed focal areas which lacked p16INK4a staining. Expression of p16INK4a, as determined by RT-PCR, was variable in lung tumors. Mutations in p16INK4a were not found by SSCP analysis. Immunohistochemical analyses of normal lung tissues showed intense staining for Rb protein in alveolar epithelial cells and in other lung cell types; however, in the lung tumors the staining intensity was reduced and the distribution was altered. Expression of Rb was detected in normal lung tissues but was barely detectable by Northern blot hybridization in lung tumors. Western blot analysis indicated the presence of both hypophosphorylated and hyperphosphorylated Rb protein in lung tumors and in normal lung tissues. These results suggest that alterations in the cell cycle proteins, cyclin D1, cdk4, p16INK4a, and Rb, may play a role in the acquisition of autonomous growth by adenomas. Furthermore, they demonstrate the importance of immunohistochemical studies to examine expression in tissues that contain multiple cell types, such as the lung, and in tumors that by nature are heterogeneous.