Mutations of the cell cycle arrest gene p21WAF1, but not the metastasis-inducing gene S100A4, are frequent in oral squamous cell carcinomas from Sudanese toombak dippers and non-snuff-dippers from the Sudan, Scandinavia, USA and UK

PCR and direct DNA sequencing methods were used to analyse the prevalence of mutations in exon 2 of the p21waf1 gene in 14 oral squamous cell carcinomas (OSCCs) and 8 non-malignant oral mucosal lesions from Sudanese toombak dippers. For comparison, OSCCs (14 from the Sudan, 16 from Norway, 11 from Sweden, 21 from the USA and 14 from the UK) and non-malignant oral mucosal lesions (3 from the Sudan) from non-snuff-dippers were included. The prevalence of mutations in exons 2 & 3 of the S100A4 gene were analysed in the 14 OSCCs from toombak-dippers and in 25 cases of OSCCs from the control non-snuff-dippers. Of the 14 OSCCs investigated from toombak-dippers, mutations in the p21waf1 exon 2 were found in 43% (6 out of 14), compared to 14% (2 out of 14), 22% (6 out of 27) and 14% (5 out of 35) found in those from non-snuff-dippers from the Sudan, Scandinavia and the USA/UK, respectively. OSCCs from toombak-dippers showed 13 different mutations distributed as 10 (77%) transitions and 3 (23%) transversions. OSCCs from non-snuff-dippers from the Sudan, Scandinavia, the USA and the UK showed 33 different mutations distributed as 14 (42%) transitions and 19 (58%) transversions. In the OSCCs examined, cases with mutations in the p21waf1 also had p53 gene mutations. Only exon 2 of the S100A4 gene was found mutated in 3 cases of OSCCs (one from a toombak-dipper and two from the non-snuff-dippers). The toombak-dipper OSCC had 4 mutations (one transition, 3 transversions), compared to the OSCCs from non-snuff-dippers which showed 3 mutations each (one transition, 2 transversions). All these 3 cases were negative for mutations in the p21waf1 and p53 genes. No mutations of p21waf1 or S100A4 were found in the non-malignant oral mucosal lesions from the snuff-dippers/non-dippers. These findings suggest that; (i) p21waf1, together with p53, is a target gene of oral carcinogenesis in OSCCs from toombak-dippers, with the tobacco specific nitrosamines present in toombak possibly acting as principal carcinogens in these OSCCs; (ii) findings of p21waf1 exon 2 mutations in the OSCCs unrelated to snuff use further demonstrate that this gene may play an important role during the pathogenesis of OSCCs caused by smoked tobacco use; (iii) mutations in the S100A4 gene are rare in OSCCs, but appears to be complementary to p21waf1 and p53 mutations. Since molecular analysis of OSCCs can provide clues to endogenous or environmental factors contributing to the high risk of OSCCs, further analysis of the role of the p21waf1 gene mutations as a biomarker of malignant transformation, which is linked to the p53 gene, is necessary, especially in habitual users of toombak from the Sudan.

Difference in Patterns of Met Expression in Papillary Thyroid Carcinomas and Nonneoplastic Thyroid Tissue

Met protein is a tyrosine kinase receptor for hepatocyte growth factor (HGF). c-Met has morphogenic, mitogenic, and motogenic properties and is overexpressed in many solid tumors. We studied c-met mRNA and protein expression in papillary thyroid carcinomas and nonneoplastic thyroid tissue. The c-met mRNA was detected in all biopsies by reverse transcriptase-polymerase chain reaction and by hybridization of complex cDNA probes to a c-met-specific DNA fragment in a dot blot array. Immunohistochemistry on fresh frozen biopsies showed Met protein localized along the basal cell membrane of normal thyrocytes in 32 of 35 nonneoplastic thyroid tissue specimens, sometimes associated with weak cytoplasmic reactivity but without apical cell membrane staining. In papillary carcinomas an increased Met protein expression was seen, comprising a cytoplasmic (33 of 49) and apical cell membrane (24 of 49) immunoreactivity, whereas only 1 of 49 biopsies showed basal cell membrane staining. A 145-kDa Met-specific band was detected by Western immunoblotting on protein extracts from papillary carcinomas. The tight junction protein zona occludens-1 (ZO-1), studied by immunohistochemistry, was weakly expressed along the apical cell membrane in 10 nonneoplastic biopsies. In contrast, increased and cytoplasmic/apical membranous ZO-1 immunostaining was seen in 11 of 15 papillary carcinomas. Nuclear ZO-1 staining was present in a few papillary carcinomas with partial dedifferentiation. The concomitant overexpression and subcellular redistribution of Met and ZO-1 proteins indicate a change in cell polarity in papillary carcinomas compared to nonneoplastic thyroid tissue. These observations may reflect an important feature of the tumorigenesis of papillary thyroid carcinomas. No significant association was found between semiquantitative immunohistochemical assessment of Met protein and clinical parameters in papillary carcinoma patients.

Influence of TP53 gene alterations and c-erbB-2 expression on the response to treatment with doxorubicin in locally advanced breast cancer

TP53 status [mutations, immunostaining, and loss of heterozygosity (LOH)], expression of c-erbB-2, bcl-2, and histological grading were correlated to the response to doxorubicin monotherapy (14 mg/m2) administered weekly to 90 patients with locally advanced breast cancer. Mutations in the TP53 gene, in particular those affecting or disrupting the loop domains L2 or L3 of the p53 protein, were associated with lack of response to chemotherapy (P = 0.063 for all mutations and P = 0.008 for mutations affecting L2/L3, respectively). Similarly, expression of c-erbB-2 (P = 0.041), a high histological grade (P = 0.023), and lack of expression of bcl-2 (P = 0.018) all predicted chemoresistance. No statistically significant association between either p53 immunostaining or TP53 LOH and response to therapy was recorded, despite the finding that both were associated with TP53 mutation status (p53 immunostaining, P < 0.001; LOH, P = 0.021). Lack of immunostaining for p53 despite mutation of the TP53 gene was particularly seen in tumors harboring nonsense mutations or deletions/splices (7 of 10 negative for staining compared with 4 of 16 with missense mutations). TP53 mutations (total/affecting L2/L3 domains) were associated with expression of c-erbB-2 (P < 0.001 for both), high histological grade (P = 0.001 and P = 0.025), and bcl-2 negativity (P = 0.003 and P = 0.002). TP53 mutations, histological grade, and expression of bcl-2 (but not LOH or c-erbB-2 expression) all predicted for relapse-free as well as breast cancer-specific survival in univariate analysis (Ps between <0.0001 and 0.0155), but only tumor grade was found to be predictive in multivariate analysis (P = 0.01 and P = 0.0007, respectively). Our data are consistent with the hypothesis that certain TP53 mutations predict for resistance to doxorubicin in breast cancer patients. However, the observation that the majority of patients with TP53 mutations affecting or disrupting the L2/L3 domains with LOH in addition (n = 12) obtained a partial response (n = 4) or stabilization of disease (n = 5) during chemotherapy suggests redundant mechanisms to compensate for loss of p53 function. Our findings are consistent with the hypothesis that other defects may act in concert with loss of p53 function, causing resistance to doxorubicin in breast cancers.

Expression and alternative splicing of c-ret RNA in papillary thyroid carcinomas

Somatic rearrangements of the ret receptor tyrosine kinase have been consistently reported in papillary thyroid carcinomas (PTC). It is unclear whether the expression of wild-type c-ret may also be implicated in thyroid tumorigenesis. We studied ret mRNA expression in PTC from Norwegian patients. Using RT-PCR, wild-type ret mRNA was detected in all of 22 PTC and in a PTC cell line. c-ret mRNA was clearly overexpressed in PTC as compared to non-neoplastic thyroid tissue. Hybridization using ret exon DNA dot blot arrays and complex cDNA probes confirmed expression of ret RNA in thyroid biopsies. In accordance with the RNA data, Western immunoblotting showed evidence of wild-type Ret protein in PTC. Rearrangements generating the ret/PTC oncogenes co-existed with c-ret mRNA in PTC. Multiple alternative ret splicing variants were detected in PTC. Four novel ret splicing events were found in the region encoding the extracellular domain. The open reading frames of these transcripts were all in-frame with the Ret tyrosine kinase domain. In the central ret mRNA region encoding the cysteine-rich, transmembrane, and main tyrosine kinase domains, no evidence of alternative splicing was detected. Two alternative splice events were detected in the ret mRNA encoding the C-terminal part of Ret protein harboring tyrosine residues important for Ret signaling, excluding exon 19, or retaining intron 19, respectively. Ribonuclease protection assays confirmed the presence of ret alternative splicing events in thyroid biopsies. We conclude that in addition to ret/PTC rearrangements, wild-type c-ret mRNA and alternatively spliced ret transcripts are present in PTC. Transcriptional up-regulation and post-transcriptional mechanisms of c-ret RNA processing may contribute to differences in expression of Ret protein observed in PTC compared to non-neoplastic thyroid tissue.

Ectopic expression of Bcl-2 switches over nuclear signalling for cAMP-induced apoptosis to granulocytic differentiation

The IPC-81 myeloid leukaemia cells undergo apoptosis rapidly after cAMP stimulation (6 h) and cell death is prevented by early over-expression of the cAMP-inducible transcription repressor ICER, that blocks cAMP-dependent nuclear signalling. Therefore, the expression of specific genes controlled by CRE-containing promoters is likely to determine cell fate. We now show that cAMP-induced cell death also is abrogated by the over-expression of the anti-apoptotic gene, Bcl-2. Contrary to ICER, Bcl-2 does not affect cAMP-signalling and allows the analysis of cAMP responses in death rescued cells. The Bcl-2 transfected cells treated with 8-CPT-cAMP were growth-arrested and thereafter cells embarked in granulocytic differentiation, with no additional stimulation. Neutrophilic polynuclear granulocytes benefited from a long life span in G0-G1 and remained functional (phagocytosis). This work demonstrates that, using anti-apoptosis regulators, 'death signals' could be exploited to trigger distinct biological responses. Indeed, cAMP signal can trigger several simultaneously developing biological programs, in the same cell, i.e., growth regulation, apoptosis and differentiation. This cell system should prove useful to determine how a tumour cell can be re-programmed for either apoptosis or functional maturation by physiological signals.

Expression of a peptide binding to receptor for activated C-kinase (RACK1) inhibits phorbol myristoyl acetate-stimulated phospholipase D activity in C3H/10T1/2 cells: dissociation of phospholipase D-mediated phosphatidylcholine breakdown from its synthesis

The C3H/10T1/2 Cl8 HAbetaC2-1 cells used in this study express a peptide with a sequence shown to bind receptor for activated C-kinase (RACK1) and inhibit cPKC-mediated cell functions. Phorbol myristoyl acetate (PMA) strongly stimulated phosphatidylcholine (PtdCho)-specific phospholipase D (PLD) activity in the C3H/10T1/2 Cl8 parental cell line, but not in Cl8 HAbetaC2-1 cells, indicating that full PLD activity in PMA-treated Cl8 cells is dependent on a functional interaction of alpha/betaPKC with RACK1. In contrast, the PMA-stimulated uptake of choline and its subsequent incorporation into PtdCho, were not inhibited in Cl8 HAbetaC2-1 cells as compared to Cl8 cells, indicating a RACK1-independent but PKC-mediated process. Increased incorporation of labelled choline into PtdCho upon PMA treatment was not associated with changes of either CDP-choline: 1,2-diacylglycerol cholinephosphotransferase activity or the CTP:phosphocholine cytidylyltransferase distribution between cytosol and membrane fractions in Cl8 and Cl8 HAbetaC2-1 cells. The major effect of PMA on the PtdCho synthesis in C3H/10T1/2 fibroblasts was to increase the cellular uptake of choline. As a supporting experiment, we inhibited PMA-stimulated PtdH formation by PLD, and also putatively PtdH-derived DAG, in Cl8 cells with 1-butanol. Butanol did not influence the incorporation of [(14)C]choline into PtdCho. The present study shows: (1) PMA-stimulated PLD activity is dependent on a functional interaction between alpha/betaPKC and RACK1 in C3H/10T1/2 Cl8 fibroblasts; and (2) inhibition of PLD activity and PtdH formation did not reduce the cellular uptake and incorporation of labelled choline into PtdCho, indicating that these processes are not directly regulated by PtdCho-PLD activity in PMA-treated C3H/10T1/2 Cl8 fibroblasts.

Expression of heregulins and associations with the ErbB family of tyrosine kinase receptors in papillary thyroid carcinomas

Heregulin (Hrg) growth factors are natural ligands for ErbB3 and ErbB4. Because these receptors are involved in papillary thyroid carcinomas, we studied expression of Hrgs in fresh-frozen thyroid tissue and analyzed for possible coexpressions among the 4 members of the ErbB family of growth factor receptors and Hrgs in papillary carcinomas. Immunohistochemistry for the Hrg precursor isoform (134 biopsies from 101 patients) showed nuclear immunostaining in 83% of papillary carcinomas but not in normal thyroid tissue. Cytoplasmic immunopositivity for the Hrg precursor isoform was moderate or strong in 78% of papillary carcinoma specimens and weak in 13% of normal thyroid tissue samples. Western blot for the Hrg precursor isoform showed the expected protein band of approximately 70 kDa in papillary carcinomas, but not in non-neoplastic thyroid biopsies. Whereas weak cytoplasmic immunostaining for the mature Hrg alpha, beta1, and beta3, was present in 48, 38, and 51% of papillary carcinomas, respectively, normal thyroid tissue samples were negative. Hrg mRNA was present in both tumor and nontumor tissue, with evidence of increased mRNA expression in 5 of 12 papillary carcinomas. RT-PCR of hrg mRNA, with subsequent DNA sequencing, confirmed the presence of hrg alpha, beta1, beta2, and beta3 mRNA in papillary carcinomas. In 55 papillary carcinomas, increased cytoplasmic immunostaining of the ErbB2 and ErbB3 receptors was significantly associated with each other and with cytoplasmic epidermal growth factor receptor (EGFR) immunoreactivity, indicating a common regulatory mechanism. Cytoplasmic staining for Hrg beta3 was significantly associated with ErbB3 immunostaining, indicating this receptor as the cognate one. The overexpression and nuclear localization of the Hrg precursor isoform were not associated with the expression of ErbB-receptors. This may reflect an unknown mechanism of action, possibly independent of the ErbB receptor system.

Differential TPA and PDGF-BB effects on subcellular localisation of PKC alpha and beta I in C3H/10T1/2 cells

60-75% of PKC alpha and 30-40% of PKC beta I++ protein was located to the membranes and nuclear/nuclear associated endoplasmatic reticulum fractions of resting 10T1/2CI 8 mouse embryo fibroblasts. On average, 35% of the PKC alpha and 65% of the PKC beta I++ isoforms existed in a soluble state. Maximum PDGF-BB-mediated Erk1 activation was obtained without significant changes in soluble PKC alpha- or PKC beta I++- levels. The subcellular localisation of PKC alpha and PKC beta I was not affected by PDGF-BB treatment. 12-O-tetradecanoyl phorbol-13-acetate (TPA) caused translocation of cytoplasmic PKC alpha and beta I to the nucleus/nuclear associated endoplasmatic reticulum fraction. Down-regulation of PKC and bisindolylmaleimide I inhibited both TPA and PDGF-BB stimulated Erk1 activity. We are the first to show that PDGF-mediated activation of Erk1 involves a PKC-dependent step in 10T1/2CI 8 cells. We also provide novel evidence that PDGF-BB mediated Erk1 activation can take place in these cells without apparent recruitment of soluble PKC alpha/beta I to the particulate cell fractions.

A mutated PML/RARA found in the retinoid maturation resistant NB4 subclone, NB4-R2, blocks RARA and wild-type PML/RARA transcriptional activities

The fusion protein PML/RARA, associated with acute promyelocytic leukemia behaves as an abnormal retinoic acid (RA) receptor with altered transactivation properties but is still inducible by RA. The chimeric protein is thought to promote leukemogenesis but also paradoxically to mediate the sensitivity to ATRA of APL cells. This has been supported by works reporting that in vitro ATRA resistance is characterized by defects in the RARA/E-domain of PML/RARA. In the present report, we identified a new mutation in the E domain of PML/RARA which is associated with a RA-resistant subline of NB4 cells; NB4-R2. This mutation, identical to the Gln411 mutation found in HL60-R, changes the amino acid Gln903 to an in-phase stop codon, generating a truncated form of PML/RARA which has lost 52 amino acids at its C-terminal end. We have studied the effect of the truncated PML/RARA protein on PML NB formation and RARA and PML/RARA transcriptional activity. We show here that the fusion mutant exerts a dominant negative effect on wild-type PML, PML/RARA and RARA transcription activity. These findings highlight the important role of the RARA E-domain of PML/RARA in mediating RA sensitivity in APL cells.

Enhanced expression of EGF receptor and low frequency of ras mutations in X-ray-induced rat thyroid tumours

Radiation is recognized as a carcinogenic factor for the thyroid gland. In this experimental study, oncogene expression was investigated in radiation-induced rat thyroid tumours. Forty 3-month-old Wistar rats received X-ray-irradiation to the neck region; 40 animals were untreated controls. After 14 months, thyroid tumours had developed in 25 of the 29 irradiated animals still alive; 76% of these tumours were considered malignant. No tumours developed in controls. Mutations of codons 12-13 and 59-63 of H-, K- and N-ras were analysed by PCR-SSCP (single-strand conformation polymorphism analysis) and sequencing of DNA from thyroid tissue. SSCP indicated a ras mutation frequency of 8%, but only one K-ras codon 12 (Gly-Cys) mutation was confirmed by sequencing. Protooncogene expression was analysed by mRNA slot blot hybridization analysis and immunohistochemistry. K-ras mRNA expression and EGF receptor mRNA and protein expression were significantly increased in the irradiated animals compared with controls, and in tumours versus nontumour tissue. This study of radiation-induced rat thyroid tumours demonstrates that ras expression may be subject to changes apart from activating mutations. Increased expression of EGF receptor in the tumours parallels the situation in human thyroid cancer.

Mutations of the p53 gene in oral squamous-cell carcinomas from Sudanese dippers of nitrosamine-rich toombak and non-snuff-dippers from the Sudan and Scandinavia

Using PCR-SSCP/DNA sequencing methods, we analyzed 14 oral squamous-cell carcinomas (OSCCs) and 8 pre-malignant oral lesions from different Sudanese patients for prevalence of mutations in exons 5 to 9 of the p53 gene in relation to toombak-dipping status. OSCCs (14 from Sudan, 28 from Scandinavia), and 3 pre-malignant oral lesions from Sudanese non-dippers were used as controls. A statistically significant increased incidence in mutations of the p53 gene was found in OSCCs from toombak dippers (93%; 13/14), as compared with those from non-dippers in Sudan (57%; 8/14) and in Scandinavia (61%; 17/28) respectively. In OSCCs from dippers, mutations were found in exons 5 to 9, while in those from non-dippers they were found in exons 5, 7, 8, 9, and no mutations were found in exon 8 in any of the OSCCs from Sudan. Certain types of mutations, however, were similar with respect to exposure to toombak. OSCCs from dippers showed 15 transversions, 9 transitions, 3 insertions and one deletion, compared with 7 transversions, 2 transitions and one deletion found in OSCCs from Sudanese non-dippers, and 9 transversions, 17 transitions and 2 insertions found in those from non-dippers in Scandinavia. No mutations were found in any of the non-malignant oral lesions in relation to dipping or non-dipping status. These findings suggest that (i) the use of toombak plays a significant role in induction of increased p53 gene mutations, (ii) mutations observed were similar to those induced by tobacco-specific N-nitrosamines (TSNAs) in experimental animal models and those already reported in toombak dippers, (iii) types of mutations associated with TSNAs were similar in the exposed and the control groups, (iv) a novel mutation in exon 6 was found in the OSCCs from toombak dippers, (v) the p53 exons 5 (codon 130), 6 (codons 190, 216) and 7 (codons 229, 249, 252) mutations are probable hot spots for toombak-related OSCCs. Further studies are necessary to validate the increased incidence and exon locations of the p53-gene mutations as a biomarker of malignant transformation in populations in which the oral use of tobacco is habitual.

Expression of biomarkers (p53, transforming growth factor alpha, epidermal growth factor receptor, c-erbB-2/neu and the proliferative cell nuclear antigen) in oropharyngeal squamous cell carcinomas

Using immunohistochemistry, expression of p53, transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), c-erbB-2/neu and proliferating cell nuclear antigen (PCNA) was examined in 26 fresh frozen tissue specimens of oropharyngeal squamous cell carcinomas (SCCs). p53 gene mutations were examined by polymerase chain reaction (PCR)/DNA sequencing methods in 22 carcinomas. The findings were examined for correlations with patients' clinicopathological parameters. Expressions of p53 and PCNA were also examined in 21 formalin-fixed corresponding tissues. Of the fresh frozen tissue specimens, 77% (20/26) showed expression and 68% (15/22) showed mutations (substitutions) of the p53, with significant clustering of the mutations in exons 5 (8/22; 36%), 7 (4/22; 18%) and 8 (5/22; 23%). No mutations were found in exon 6. There was a discordance between expression of p53 protein and mutations of the gene. Parallel to expression and mutations of the p53 found in most of the specimens, expression of TGF-alpha, EGFR, c-erbB-2/neu and PCNA was found in 88% (22/25), 92% (23/25), 58% (14/24) and 91% (21/23) of the specimens, respectively. For the formalin-fixed tissue specimens, 62% (13/21) and 90% (19/21) expressed p53 and PCNA, respectively. Examining for correlations with patients' clinicopathological parameters, expression of p53, TGF-alpha, EGFR and c-erB-2/neu seemed to negatively correlate with the increase of the tumour grade. The present work suggests that: (1) lack of negative growth regulation due to inactivation of the p53 gene together with activation of other proto-oncogenes are necessary genetic events in the carcinogenesis of oropharyngeal SCCs; (2) in oropharyngeal SCCs, p53 gene mutations were clustered in exons 5 (codons 130-186), 7 (codons 230-248) and 8 (codons 271-282) which perhaps suggests that tobacco carcinogens probably affect the mutational hot spots of the p53 gene at codons 157, 175, 186, 248, 273 and 282; and (3) fresh frozen and formalin-fixed tissue specimens give similar results when an immunohistochemical method is applied. The importance of p53, TGF-alpha, EGFR, c-erbB-2/neu and PCNA as biomarkers in oropharyngeal SCCs deserves particular attention because it might offer further understanding of the development of these carcinomas.

Early modulation of genes encoding peroxisomal and mitochondrial beta-oxidation enzymes by 3-thia fatty acids

The aim of the present study was to elucidate the effects of a single dose of 3-thia fatty acids (tetradecylthioacetic acid and 3-thiadicarboxylic acid) over a 24-hr study period on the expression of genes related to peroxisomal and mitochondrial beta-oxidation in liver of rats. The plasma triglyceride level decreased at 2-4 hr, 4-8 hr, and 8-24 hr, respectively, after a single dose of 150, 300, or 500 mg of 3-thia fatty acids/kg body weight. Four to eight hours after administration of 3-thia fatty acids, a several-fold-induced gene expression of peroxisomal multifunctional protein, fatty acyl-CoA oxidase (EC 1.3.3.6), fatty acid binding protein, and 2,4-dienoyl-CoA reductase (EC 1.3.1.43) resulted, concomitant with increased activity of 2,4-dienoyl-CoA reductase and fatty acyl-CoA oxidase. The expression of carnitine palmitoyltransferase-I and carnitine palmitoyltransferase-II increased at 2 and 4 hr, respectively, although at a smaller scale. In cultured hepatocytes, 3-thia fatty acids stimulated fatty acid oxidation after 4 hr, and this was both L-carnitine- and L-aminocarnitine-sensitive. The hepatic content of eicosapentaenoic acid and docosahexaenoic acid decreased throughout the study period. In contrast, the hepatic content of oleic acid tended to increase after 24 hr and was significantly increased after repeated administration of 3-thia fatty acids. Similarly, the expression of delta9-desaturase was unchanged during the 24-hr study, but increased after feeding for 5 days. To conclude, carnitine palmitoyltransferase-I expression seemed to be induced earlier than 2,4-dienoyl-CoA reductase and fatty acid binding protein, and not later than the peroxisomal fatty acyl-CoA oxidase. The expression of delta9-desaturase showed a more delayed response.

The Swedish snus and the Sudanese toombak: are they different?

In Sweden, snuff (locally known as snus), was introduced since the year 1637. Presently, Sweden has the highest per capita consumption and sale figures of snuff in the world, and the habit is becoming increasingly popular. Snus is manufactured into a dry form used in the nasal cavity and a moist form used in the oral cavity. Snus manufactured for oral use is a moist ground tobacco of Dark Kentucky or Virginia species mixed with an aqueous solution of water and other blending ingredients. This form of snuff is found in two types: (1) loose and (2) portion-bag-packed. These are the most widely used. The loose moist form (1-2 g a quid) is the most popular type consumed by 73% of the males, followed by the portion-bag-packed form (0.5-1 g a quid), consumed by 13% of the males, while 14% of the males are mixed users. The majority of snus users place the quid in the vestibular area of the upper lip, and the prevalence among persons 15 years of age or older in 15.9% among males and 0.2% among females. The pH of snus has declined from a previous range of 8-9 to a range of 7.8-8.5, moisture content ranges 35-60% and nicotine content is in the order of 5-11 mg/g dry wt tobacco-specific N-nitrosamines (TSNAs) in micrograms (N'-nitrosonornicotine: NNN 5-9; 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone: NNK 1-2; N'-nitrosoanatabine: NAT 2-5). In the Sudan, snuff, locally known as toombak, was introduced approximately 400 years ago. It is always processed into a loose moist form, and its use is widespread in the country. Tobacco used for manufacture of toombak is of the species Nicotiana rustica, and the fermented ground powder is mixed with an aqueous solution of sodium bicarbonate. The resultant product is moist, with a strong aroma, highly addictive and its use is widespread particularly among males. Its pH range is 8-11, moisture content ranges 6-60% and nicotine content is from 8 to 102 mg/g dry wt, and TSNAs contents in micrograms (NNN 420-1 550; NNK 620-7 870; NAT 20-290). Snus and toombak dippers develop a clinically and histologically characteristic lesion at the site of dipping. Probably due to control of the TSNAs in snus, this type of snuff is associated with a lower risk of cancer of the oral cavity (relative risk: RR 5-6-fold), whereas the risk for cancer of the oral cavity among toombak users was high (RR 7.3-73.0-fold). In conclusion, the two snuff products significantly differ in many aspects. Most notable differences are tobacco species, fermentation and ageing, nicotine and TSNAs content, pH, expression of the p53 tumour suppressor gene, and keratin types 13, 14, and 19. It was, therefore, the object of the present study to highlight the oral health hazards of toombak, and to compare it with snus regarding the aforementioned differences.

Choline derived from the phosphatidylcholine specific phospholipase D is not directly available for the CDP choline pathway in phorbol ester-treated C3H10T1/2 Cl 8 fibroblasts

We have shown that 12-O-tetradecanoylphorbol 13-acetate (TPA) increases protein kinase C (PKC)-mediated choline transport, incorporation of choline into phosphatidylcholine (PtdCho) and PtdCho degradation by phospholipase D (PLD) in C3H10T1/2 Cl 8 cells. Dual prelabeling experiment using [3H]/[14C]choline indicated that intracellular choline generated from the PLD reaction was not directly recycled to PtdCho synthesis within the cell, and that a large fraction of the choline was transported out of the TPA-treated cells. In contrast, medium derived choline was preferably channeled to PtdCho synthesis. These results indicate that in TPA-treated cells, the choline derived from the PKC-mediated increased PLD activity and the choline newly taken up by the cell behave as two distinctly different metabolic pools.

[Diagnostic molecular biology in solid tumors--thyroid gland]

Thyroid cancer is not a common disease. It includes tumour types of great diversity in clinical course and molecular basis. Mutations of TSH-receptor, rearrangements of ret proto-oncogene, and altered expression of other tyrosine kinase growth factor receptors are characteristics of the follicular neoplasias and papillary carcinomas, while undifferentiated tumours harbour p53 mutations. Knowledge acquired to date has led to an increased understanding of thyroid growth and tumour development, but it has had no significant impact on diagnostic and treatment measures. On the other hand, the C-cell derived medullary carcinomas include familial cases where identification of germ-line ret mutations provides the basis for prophylactic thyroidectomy in affected individuals.

Expression of c-erbB proto-oncogene family members in squamous cell carcinoma of the head and neck

The exact role of oncogenes and proto-oncogenes in the development of squamous cell carcinoma of the head and neck (SCCHN) is still debatable. The expression of the c-erbB-2, c-erbB-3 and c-erbB-4 members of the epidermal growth factor receptor family was examined in 16 fresh frozen tissue specimens of SCCHN using avidin-biotin complex immunohistochemistry, with monoclonal and/or polyclonal antibodies directed against each. Eight fresh frozen tissue specimens of normal oral mucosa were included as controls. Of the SCCHN examined, mixed membrane/cytoplasmic staining (moderate to intense) of c-erbB-2 was found in 14/16 cases (88%). When present in the specimen, immunopositive staining of c-erbB-2 was seen in some of the oral surface epithelial cell layers (basal, intermediate and/or superficial) as well as the tumour islands. Weak cytoplasmic staining of c-erbB-3 and c-erbB-4 was found in 13/16 (81%) and 11/16 (69%) cases respectively. When present in the specimen, c-erbB-3 and cerbB-4 immunopositive staining was seen in some of the oral surface epithelial cell layers (basal, intermediate and/or superficial) as well as the tumour islands. For the positive carcinomas for c-erbB-2, c-erbB-3 and c-erbB-4, the epithelium located near the carcinomas showed weak mixed membrane/cytoplasmic staining of c-erbB-2 in 5/14 cases (36%), weak cytoplasmic staining of c-erbB-3 in 7/13 cases (54%) and of c-erbB-4 in 3/11 cases (27%). All the normal control oral mucosa showed the same pattern of staining for c-erbB-2, c-erbB-3 and c-erbB-4 found in the epithelium located near the carcinomas. Only expression of c-erbB-2 was found to correlate with the increase in the tumour stage, while co-expression of c-erbB-2, c-erbB-3 and c-erbB-4 was found to correlate with the patient survival time in 25% of the carcinomas examined. The present study shows that a) expression of c-erbB-2, but not c-erbB-3 and c-erbB-4 correlates with the increase of the tumour stage b) co-expression of c-erbB-2, c-erbB-3 and c-erbB4 correlates with decreased survival time in some of the cases of SCCHN, but not the majority c) co-expression of the c-erbB family in normal oral mucosa as well as in the carcinoma may question whether the increased tendency for development of the disease is due to co-expression of c-erbB proto-oncogenes in head and neck lesions.

1-(Carboxymethylthio)tetradecane attenuates PDGF- and TPA-induced c-fos mRNA expression and increases the formation of phosphatidylethanolamine with a shift from less to more polar molecular species in C3H/10T1/2 cells

1-(Carboxymethylthio)tetradecane caused C3H/10T1/2Cl8 and C3H/10T1/2Cl16 to incorporate 10 times more [32P]Pi into diacylphosphatidylethanolamine than control. This 3-thia fatty acid caused a shift in incorporation of 32P-radioactivity into phosphatidylethanolamine species from species with long to species with short HPLC elution times. The increase in 32P-labeling was parallelled by a change in the apparent mass of phosphatidylethanolamine to a higher proportion of molecular species with short elution times than with long elution times. 1-(Carboxymethylthio)tetradecane caused loss of molecular species containing stearoyl groups. These results indicate that culturing the cells with 1-(carboxymethylthio)tetradecane causes looser packing and an increase in fluidity of the diacylphosphatidylethanolamine molecules in the membranes. 12-O-tetradecanoyl phorbol-13-acetate (TPA), platelet-derived growth factor (PDGF)-BB, or PDGF-AA stimulation of 1-(carboxymethylthio)tetradecane-treated cells resulted in decreased maximal levels of c-fos mRNA expression, indicating attenuation of signal transduction. Compared to cells not treated, the levels of both PDGF-alpha and PDGF-beta receptors were lower while GTPase-activating protein and phospholipase C-gamma levels were not altered in C3H/10T1/2Cl8 and C3H/10T1/2Cl16 cells cultured in the presence of 1-(carboxymethylthio)tetradecane. Our data demonstrate that 1-(carboxymethylthio)tetradecane-mediated changes in phospholipid structure and composition may affect PDGF- and TPA-mediated c-fos gene regulation in fibroblasts.

Immunohistochemical detection of p53 in archival formalin-fixed tissues of lip and intraoral squamous cell carcinomas from Norway

We investigated the expression of p53 in 82 formalin-fixed, paraffin-embedded archival tissue specimens of lip and intraoral squamous cell carcinomas (SCCs) from the period 1930-1995, by immunohistochemistry using three monoclonal antibodies (MAbs DO-7, DO-1 and 1801). Before incubation, sections were pretreated with 0.1% Protease enzyme at 37 degrees C for 10 min followed by 5 + 5 min microwave oven heating at 700 W and 425 W, respectively. Formalin-fixed tissues of 10 carcinomas of the uterine cervix positive for p53 were used as controls. With one or more of the three MAbs, p53 was expressed in 73% of the 82 SCCs examined. With only protease enzyme pretreatment or microwave oven heating, p53 was expressed in 9/82 and 12/82 of the SCCs, respectively. Of the 82 SCCs, 60%, 45% and 23% expressed p53 with DO-7, DO-1 and 1801, respectively. The kappa coefficient indicated poor agreement between these results for the antibodies, and for lip and intraoral SCCs, except for p53 expression in intraoral SCCs demonstrated by DO-1/1801, which showed fair agreement. The present study suggests that combined protease pretreatment and microwave oven heating of tissue sections improved unmasking of p53 antigenic sites in archival material stored for up to 65 years.

Differential changes of retinoid-X-receptor (RXR alpha) and its RAR alpha and PML-RAR alpha partners induced by retinoic acid and cAMP distinguish maturation sensitive and resistant t(15;17) promyelocytic leukemia NB4 cells

The expression of retinoid receptors (RXRalpha, RARalpha and the chimeric form PML-RARalpha) was analysed both at the mRNA and protein level in the maturation sensitive NB4 and resistant NB4-R1 cell lines of t(15;17) promyelocytic leukemia (APL). All-trans RA and cAMP which show synergistic activity in inducing maturation of NB4 cells and maturation triggering of the RA 'primed' NB4-R1 resistant cells, distinctly modulate RXRalpha, RARalpha and PML-RARalpha mRNA. In the NB4 and NB4-R1 cells, RXRalpha mRNA was downregulated by RA, but only in RA-primed NB4-R1 cells a release from RXRalpha mRNA downregulation was obtained by cAMP treatment. RXRalpha protein (53 kDa) was decreased to the western-blot detection limit (97.5%) by RA in NB4 cells, but in NB4-R1 cells although it was frankly decreased (85%), the signal for RXRalpha protein remained very significant. More importantly, while cAMP slightly upregulated RXRalpha protein in RA-treated NB4 cells, it caused an increase of RXRalpha protein in RA-treated NB4-R1 cells bringing RXRalpha to the initial control level. RXRalpha partners in heterodimers (PML-RARalpha, RARalpha) were also analysed. In contrast to RXRalpha, RARalpha and PML-RARalpha mRNA were not modulated by RA and/or cAMP, while significant changes were observed at the protein levels. A putatively phosphorylated form of RARalpha (52 kDa) decreased during maturation of NB4 cells, but was unchanged in resistant NB4-R1 cells. Conversely, while PML-RARalpha remained stable during RA-induced NB4 maturation, RA treatment which failed to induce maturation of NB4-R1 cells significantly down-regulated the chimeric receptor (120 kDa). These differences most likely results from translational and post-translational regulation. This work reveals complex pattern of subtle changes at the protein level distinguishing RA-sensitive and RA-resistant cells. Our data show that the RA-cAMP synergistic effect on NB4 cell maturation and cooperation in triggering maturation of RA-primed NB4-R1 cells operate changes in the RXR/PML-RARalpha ratio which are both favouring RXRalpha. In both cell lines, variations of PML-RARalpha and RXRalpha may result in a decrease in the formation of the PML-RARalpha/RXRalpha heterodimers which are supposed involved in the block of maturation. This may prove crucial to embark cells on maturation.

cAMP signalling is decisive for recovery of nuclear bodies (PODs) during maturation of RA-resistant t(15;17) promyelocytic leukemia NB4 cells expressing PML-RAR alpha

We analysed the expression of retinoid receptors and PML in relation to the morphology of PML-containing nuclear bodies (PODs) in maturation sensitive (NB4) and resistant subclones (NB4-R1 and R2) of the promyelocytic NB4 cell line. The basal level of RARalpha, RXRalpha and PML mRNA and protein were roughly the same in the three cell lines. While NB4 and NB4-R1 cells express comparable amounts of PM-RARalpha mRNA and 120 kDa protein, NB4-R2 cells despite normal mRNA levels the 120 kDa protein was not detectable. In NB4-R2 cells however, two novel PML-related entities of 65 kDa and 85 kDA were detected with a anti-PML antibody, in addition to the two PML isoforms of 78 and 97 kDa found in any NB4 cells. Despite the 120 kDa PML-RARalpha defect, NB4-R2 cells show micropunctuated nuclear bodies typical of APL cells. Contrasting with NB4 cells, neither NB4-R1 cells which express PML-RARalpha, nor NB4-R2 cells lacking the 120 kDa PML-RARalpha reorganised nuclear bodies (PODs) in response to RA. Importantly, in RA-primed NB4-R1 cells, a secondary event triggered by cAMP restored PODs, concomitant to maturation. This indicates that the recovery of nuclear bodies in APL is dissociated from the early action of RA in cell maturation. Finally, the key finding of this work is that cAMP signalling ultimately determines the recovery of nuclear bodies associated to cell maturation.

Expression of c-erbB-3 and c-erbB-4 proteins in papillary thyroid carcinomas

c-erbB-3 and c-erbB-4 protein expression was analyzed using immunohistochemistry in 138 fresh-frozen thyroid tissue samples from 106 patients, including 56 cases of papillary thyroid carcinoma. Increased expression of c-erbB-3 and c-erbB-4 proteins was observed in papillary carcinomas compared to nonneoplastic thyroid tissue. No amplifications of the c-erbB-3 and c-erbB-4 genes were detected. Coexisting overexpression of epidermal growth factor receptor, c-erbB-2, c-erbB-3, and c-erbB-4 was demonstrated in 36 (64%) of 56 papillary thyroid carcinomas. These findings suggest a common regulatory mechanism for the type I (epidermal growth factor receptor-related) receptors in papillary thyroid carcinomas and provide numerous possibilities for functional receptor interactions.

Cytoplasmic localization of EGF receptor in papillary thyroid carcinomas: association with the 150-kDa receptor form

We have previously reported that papillary thyroid carcinomas show an increased expression of EGFR mRNA and protein, compared to non-tumorous thyroid tissue. EGFR immunoreactivity was localized to the cytoplasm as well as to the membrane in papillary carcinomas. To further study EGFR protein expression in human thyroid tissue, we performed immunohistochemistry and Western blots of 64 different thyroid tissue samples from 36 patients, including 23 patients with papillary carcinomas. Two receptor forms were identified in human thyroid tissue, a 170-kDa and a 150-kDa form. The 150-kDa receptor form was more pronounced in papillary carcinomas, while the 170-kDa receptor was the dominant form in non-malignant thyroid tissues. Predominance of the 150-kDa EGFR in the tumour samples was associated with strong cytoplasmic EGFR staining. EGFR gene structure, protein synthesis and maturation were found to be normal. Immunoprecipitation and Western-blot analysis of EGFR from the human thyroid SGHTL-34 cells after increased ligand concentration showed a decreased amount of the mature 170-kDa receptor and a relative increase in the 150-kDa receptor. We have previously demonstrated the presence of a TGF-alpha-EGFR autocrine loop in papillary thyroid carcinomas, and this may explain increased receptor turnover and accumulation of a cytoplasmic degradation product.

Fatty acyl-CoA oxidase activity is induced before long-chain acyl-CoA hydrolase activity and acyl-CoA binding protein in liver of rat treated with peroxisome proliferating 3-thia fatty acids

1. In this study we explored the relationship between specific acyl-CoA esters and induction of acyl-CoA binding protein (ACBP) and enzymes related to the proliferation of peroxisomes. Male Wistar rats were administered a single dose (150 mg/day/kg) of sulphur-substituted fatty acid analogues, and the effects of tetradecylthioacetic acid and 3-thiadicarboxylic acid, which both act as peroxisome proliferators, were compared with the effects of tetradecylthiopropionic acid and palmitic acid which do not induce peroxisome proliferation. 2. The hepatic level of total long-chain acyl-CoA was significantly increased within 12 h of feeding these fatty acids, except in rat fed tetradecylthioacetic acid. Hplc chromatograms of liver extracts prepared from rat fed tetradecylthioacetic acid showed that tetradecylthioacetyl-CoA ester accumulated in the liver 4 h after feeding and had disappeared after 24 h. In liver extracts of the tetradecylthiopropionic acid-treated rat tetradecylthiopropionyl-CoA was not observed, but the appearance of a new long-chain acyl-CoA ester, probably a metabolite of tetradecylthiopropionic acid, was detected. This new peak reached a maximum 4h after feeding. In rat fed tetradecylthioacetic acid and 3-thiadicarboxylic acid the hepatic level of fatty acyl-CoA oxidase mRNA increased 8 h after feeding, while the acyl-CoA oxidase activity had increased after 12 h. 3. The early accumulation of specific tetradecylthioacetyl-CoA suggests that this ester may be a possible mediator of the induction of fatty acyl-CoA oxidase. The level of hepatic acyl-CoA binding protein, long-chain acyl-CoA hydrolase activity and long-chain acyl-CoA synthetase activity did not change after a single dose of all four fatty acids. Prolonged administration of 3-thia fatty acids resulted, however, in a dose- and time-dependent increase in hepatic ACBP content and ACBP mRNA level. The amount of ACBP increased in parallel to the long-chain acyl-CoA hydrolase activity. The correlated induction of fatty acyl-CoA binding protein and long-chain acyl-CoA hydrolase seems to be dependent on a sustained accumulation of total long-chain acyl-CoA esters.

Coordinate induction of hepatic fatty acyl-CoA oxidase and P4504A1 in rat after activation of the peroxisome proliferator-activated receptor (PPAR) by sulphur-substituted fatty acid analogues

1. In the liver of rat fed a single dose of 3-thia fatty acids, 3-dithiahexadecanedioic acid (3-thiadicarboxylic acid) and tetradecylthioacetic acid, steady-state levels of P4504A1 and fatty acyl-CoA oxidase mRNAs increased in parallel. The increases were significant 8 h after administration, reaching a maximum after 12 h and decreased from 12 to 24 h after administration. 2. The corresponding enzyme activities of P4504A1 and fatty acyl-CoA oxidase were also induced in a parallel manner by the 3-thia fatty acids. The enzyme activities were significantly increased 12 h after administration and increased further after 24 h. This may reflect a possible effect of the 3-thia fatty acids not only on mRNA levels, but also on the translation and degradation rate of the two enzymes. 3. Repeated administration of 3-thia fatty acids resulted in an increase of the specific P4504A1 protein accompanied with an increased lauric acid hydroxylase activity. The correlation between induction of P4504A1 and fatty acyl-CoA oxidase mRNAs and their enzyme activities may reflect a coordinated rather than a causative induction mechanism, and that these genes respond to a common signal. This suggests that the increased P450 activity may not be responsible or be a prerequisite for fatty acyl-CoA oxidase induction. 4. Since the peroxisome proliferator-activated receptor (PPAR) plays a role in mediating the induction of fatty acyl-CoA oxidase, we analysed the activation of PPAR by fatty acids and sulphur-substituted analogues utilizing a chimera between the N-terminal and DNA-binding domain of the glucocorticoid receptor and the putative ligand-binding domain of PPAR. Arachidonic acid activated this chimeric receptor in Chinese hamster ovary cells. Inhibitors of P450 did not affect the activation of PPAR by arachidonic acid. Furthermore, dicarboxylic acids including 1,12-dodecanedioic acid or 1,16-hexadecanedioic acid only weakly activated the chimera. 3-Thidicarboxylic acid, however, was a much more effective activator than the non-sulphur-substituted analogues. In conclusion, the data suggest that the most likely mechanism of the induction process is fatty acid-induced activation of PPAR, which then leads to a coordinated induction of P4504A1 and fatty acyl-CoA oxidase.

Three-dimensional growth of glial cell lines affects growth factor and growth factor receptor mRNA levels

We have studied, at the mRNA level, the influence of various defined growth conditions on the expression of TGF-alpha, PDGF-BB, EGF-R, PDGF-R alpha, and PDGF-R beta in five different glioma cell lines (D-37MG, D-54MG, D-263MG, GaMG, and U-251MG). RNA isolated from logarithmically growing, confluent monolayer cells or multicellular spheroids was analyzed. Northern blot experiments show that with a few exceptions, specific mRNA steady-state levels were considerably higher in cells grown in a three-dimensional organization relative to cells in the logarithmic growth phase.

Time-course study of 1,25-(OH)2-vitamin D3 induction of homologous receptor and c-myc in nontransformed and transformed C3H/10T1/2 cell clones

1. We have used 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) to investigate autoregulation of homologous receptor and the control of c-myc mRNA and protein expression in C3H/10T1/2 cells. 2. 10 nM 1,25-(OH)2D3 stimulated 1,25-(OH)2D3 receptor (VDR) synthesis in both non-transformed C3H/10T1/2 Cl 8 and in chemically transformed C3H/10T1/2 Cl 16 cells within 4 hr of treatment. Maximal induction was observed between 8 and 24 hr. 3. Two VDR mRNA transcripts, 2.7 and 4.8 kb, were present in both cell types. There were parallel changes in VDR specific mRNA levels and cellular VDR concentration in the C3H/10T1/2 Cl 8 cells indicating that the increase in receptor concentrations was dependent on de novo mRNA synthesis. 4. The increase in VDR mRNA concentration in the chemically transformed C3H/10T1/2 Cl 16 cells was maximal already at 4 hr, preceding the maximal increase in receptor concentration by 4-6 hr. 5. Analysis of c-myc mRNA levels also showed cell line specificity. 6. The c-myc mRNA level increased 2.1-fold with 10 nM 1,25-(OH)2D3 treatment in C3H/10T1/2 Cl 8 cells after 12 hr while the C3H/10T1/2 Cl 16 cells had maximal c-myc mRNA level after 1 hr. 7. The relative amount of c-myc mRNA remained higher than that of unstimulated controls the next 10-12 hr in C3H/10T1/2 Cl 16 cells. 8. The c-myc protein levels were not affected by 1,25-(OH)2D3 treatment in either cell line as detected by Western blot analysis. 9. Our data suggest that 1,25-(OH)2D3 mediated induction of VDR does not require prior c-myc protein synthesis in the C3H/10T1/2 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneous response to the growth factors [EGF, PDGF (bb), TGF-alpha, bFGF, IL-2] on glioma spheroid growth, migration and invasion

The effects of 5 different growth factors [EGF, PDGF(bb), TGF-alpha, bFGF and IL-2] were studied on tumour spheroids obtained from 5 different human glioma cell lines (U-251MG, D-263MG, D-37MG, D-54MG, GaMG). The expression of EGF and PDGF receptors as well as the endogenous production of TGF-alpha and PDGF were studied by Northern blot analyses. After growth-factor-exposure, tumour spheroid volume growth, and directional cell migration from the spheroids were studied. In addition, tumour-cell invasion was studied in vitro, where foetal rat-brain aggregates were used as a target for the tumour cells. In all the assays a common stimulator for most of the cell lines was EGF. The other growth factors had a more heterogeneous stimulatory effect. Tumour-cell invasion, cell growth and cell migration are biological properties which are not necessarily related to each other. This may explain why the tumours often responded differently to the growth factors in the various assay systems. Two of the cell lines studied were non-invasive (U-251MG, D-263MG). It is shown that these were stimulated both in the directional migration assay and in the spheroid-volume-growth assay. However, their non-invasive behaviour was not influenced by the growth factors studied.

Evidence against involvement of APC mutation in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is one of several tumours associated with familial adenomatous polyposis (FAP), an inherited tumour syndrome which appears to result from germ-line mutation of the APC tumour suppressor gene. Here we investigate the possibility that somatic mutation of APC might play a role in sporadic PTC. 16 cases of PTC together with matched normal tissue were examined by single-strand conformation polymorphism (SSCP) analysis, concentrating on the mutation cluster region (MCR) of the APC gene (codons 1286-1513). No evidence of mutation was observed in any sample. We conclude that APC mutation, at least in the MCR, is not a significant causal mechanism in sporadic PTC.

Growth requirements and oncogene expression in the human thyroid cell line SGHTL-34

The SV40 T-antigen-transfected human thyroid cell line SGHTL-34 was used to investigate the effect of thyrotropin (TSH), insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF) on c-fos and c-erbB/EGF receptor (EGF-R) mRNA expression and their role in human thyroid cell proliferation. EGF caused a transient 8- and 4-fold increase in c-fos mRNA level after 30 min in serum/hormone-deprived and in logarithmically growing cells, respectively. EGF was only mitogenic in the presence of serum, as measured by 3H-thymidine incorporation and cell counting. TSH had no detectable effect on c-fos mRNA expression and no mitogenic effect on the SGHTL-34 cells. IGF-1 showed no effect alone or in combination with EGF or TSH on either proliferation or c-fos mRNA expression. Our data suggest that increased c-fos mRNA levels are part of the mitogenic pathway, but are insufficient to engender a mitogenic response. SGHTL-34 cells produced high levels of transforming growth factor-alpha (TGF-alpha) and c-erbB/EGF-R mRNA, also seen in thyroid papillary carcinomas. The TGF-alpha protein was detected in conditioned medium from the SGHTL-34 cells, indicating that TGF-alpha may function as an autocrine growth factor. Our data show that the c-erbB/EGF-R mRNA level is regulated by growth factors and hormones in the SGHTL-34 cell line. The SGHTL-34 cells may therefore represent a useful model system for studying the role of TGF-alpha and EGF-R in thyroid carcinogenesis.

Analysis of 1alpha,25-dihydroxyvitamin D3 receptor in cell extracts with low protein concentration

An unacceptable loss of tritiated 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] to the wall of the reaction tubes constituted an obstacle when examining C3H/10T1/2 Cl 8 cells for 1,25-(OH)2D3 receptor. The loss of tracer in low protein cell extracts could be strongly reduced by incubating the cell extracts in polyethylene tubes and in the presence of inert peptides prepared by digestion of gluten proteins. When incubated in buffer the recovery of tracer increased from 3 to 45% by using polyethylene tubes instead of sodium-glass tubes. However, the presence of a sufficient amount of inert peptides in the buffer significantly increased the recovery of tracer to 89%. This procedure improved the saturation binding analysis of the 1,25-(OH)2D3 receptor in the C3H/10T1/2 Cl 8 cells using the hydroxylapatite assay.

Demonstration of a TGF-alpha-EGF-receptor autocrine loop and c-myc protein over-expression in papillary thyroid carcinomas

Autocrine growth stimulation has been identified in several types of human cancer. In the present study we wanted to establish whether autocrine stimulation of the epidermal-growth-factor receptor (EGF-r) by its ligand, transforming growth factor alpha (TGF-alpha) occurs in thyroid neoplasia. We examined 190 fresh, frozen thyroid tissue samples from 70 patients by immunohistochemistry with antibodies to EGF-r, TGF-alpha, c-erbB-2 and c-myc. EGF-r expression was detected in 17 out of 19 papillary carcinomas, TGF-alpha expression in 10, and c-erbB-2 expression in 15. No papillary carcinoma expressed TGF-alpha without also expressing EGF-r. Concomitant expression of EGF-r, TGF-alpha and c-erbB-2 was seen in 7 papillary carcinomas. No EGF-r, TGF-alpha or c-erbB-2 immunopositivity was found in normal-appearing thyroid tissue (25 cases), whereas a few of the non-neoplastic lesions (colloid goitres and diffuse hyperplasias) expressed either EGF-r or TGF-alpha. c-myc expression was detectable in all tissue samples, and expression was invariably nuclear. Increased expression was observed in 10 out of 19 papillary carcinomas, and 8 of these also co-expressed EGF-r and TGF-alpha. In situ hybridization confirmed the presence of TGF-alpha mRNA in tumour epithelium of TGF-alpha-immunopositive samples. The concomitant expression of EGF-r, TGF-alpha and TGF-alpha mRNA gives evidence for a TGF-alpha-EGF-r autocrine loop in thyroid papillary carcinomas. The increased c-myc expression may reflect the proliferative advantage of these tumours.

Inhibition and down-regulation of protein kinase C in cultured atrial myocytes: effects on distribution of specific granules and secretion of atrial natriuretic peptide

Primary cultures of neonatal rat atrial myocytes were subjected to down-regulation of protein kinase C (PKC) and to inhibition of PKC activity. The effects on secretion of atrial natriuretic peptide (ANP), and the intracellular distribution of ANP-containing specific granules and their association to microtubules, were investigated. Treating the cultures with inhibitors of PKC, staurosporine or H7, a translocation of ANP-containing specific granules from the perinuclear sarcoplasm to the periphery of the myocytes was observed, and furthermore, secretion of ANP was significantly decreased. The microtubule network were not structurally affected by the PKC inhibitors. Down-regulation of PKC by 12-O-tetradecanoylphorbol 13-acetate (TPA) for 12 h was not followed by any alteration of localization of specific granules, and the amount of secreted ANP was still considerable. Treating the down-regulated cultures with staurosporine, secretion of ANP was still significantly reduced. The present results suggest that the decreased ANP secretion and the translocation of ANP-containing specific granules in the atrial myocytes following treatment with staurosporine or H7, is mediated through mechanisms not, or only partly, requiring PKC.

Modulation of cell proliferation and cell cycle, and inhibition of cytokinesis by 1,25-dihydroxyvitamin D3 in C3H/10T1/2 fibroblasts

The growth-modulating effects of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] were studied on three mouse embryo fibroblast cell lines. Concentrations ranging from 0.1 to 100 nM inhibited dose-dependently proliferation in the non-tumorigenic C3H/10T1/2 Cl 8 (10T1/2) and the chemically transformed C3H/10T1/2 Cl 16 (Cl 16) cells. The hormone had a biphasic effect on the transformed cell line C3H/10T1/2 TPA 482 (TPA 482) in which growth was stimulated by low concentrations. Exposure to 10 nM 1,25-(OH)2D3 for 5 days resulted in a 90% growth inhibition of 10T1/2 cells, and the hormone was 10 and 100 times less potent in Cl 16 and TPA 482 cells, respectively. The inhibition of cell replication was fully reversible on removal of the hormone. Treatment of 10T1/2 and Cl 16 cells with 10 nM 1,25-(OH)2D3 reduced the saturation density to 30 and 37% that of controls, respectively, suggesting an enhancement of cell-cell contact mediated growth inhibition. 1,25-(OH)2D3 inhibited cytokinesis in 10T1/2 cells, inducing the formation of binucleated cells. Flow cytometric studies showed that 1,25-(OH)2D3-treated cells accumulated in the Go/G1 phase while the number of cells in S phase decreased. This in vitro model system seems to be useful for studies of the molecular mechanisms of the growth modulating effect of 1,25-(OH)2D3.

Absence of PDGF-induced, PKC-independent c-fos expression in a chemically transformed C3H/10T1/2 cell clone

The effect of platelet-derived growth factor (PDGF) on c-fos mRNA transcription was studied in the immortalized mouse embryo fibroblast C3H/10T1/2 Cl 8 (10T1/2) cells and the chemically transformed, tumorigenic subclone C3H/10T1/2 Cl 16 (Cl 16). In the 10T1/2 cells as well as the Cl 16 subclone, the dose-dependent PDGF stimulation of c-fos mRNA synthesis was similar in both logarithmically growing and confluent cultures. c-fos mRNA was induced severalfold by 12-O-tetradecanoylphorbol-13-acetate (TPA) in both 10T1/2 and Cl 16. Down-regulation of protein kinase C (PKC) activity by TPA pretreatment inhibited PDGF-stimulated c-fos mRNA expression in Cl 16 cells but did not affect this induction in the 10T1/2 cells. This inhibition was not a general phenomenon of 3-methylcholanthrene-mediated transformation of 10T1/2 cells since experiments with another transformed 10T1/2 cell clone, C3H/10T1/2 TPA 482, gave qualitatively the same results as the 10T1/2 cells. Receptor binding experiments showed that the nontransformed and transformed cells had a comparable number of PDGF receptors, 1.3 x 10(5) and 0.7 x 10(5) receptors per cell, respectively. Furthermore, cAMP-induced c-fos expression induced by forskolin is formerly shown to be independent of PKC down-regulation. In our experiments, forskolin induced c-fos expression in both clones. However, PKC down-regulation inhibited the forskolin-induced c-fos expression in Cl 16 cells. This apparently demonstrates cross talk between PKC and PKA in the c-fos induction pathway. The present results provide evidence for an impaired mechanism for activating c-fos expression through PKC-independent, PDGF-induced signal transduction in the chemically transformed Cl 16 fibroblasts compared to that in nontransformed 10T1/2 cells.

Expression of c-erbB-2 protein in papillary thyroid carcinomas

c-erbB-2 protein expression was investigated immunohistochemically in frozen thyroid tissue specimens from 42 patients using a polyclonal sheep antibody. c-erbB-2 immunoreactivity was detected in 12 out of 17 papillary carcinomas, while no c-erbB-2 protein immunostaining was seen in cases of follicular adenoma (five cases), follicular carcinoma (five cases) or medullary carcinoma (one case), nor in cases of non-neoplastic tissue, including normal thyroid tissue from tumour-bearing glands. RNA was extracted from 51 thyroid tissue samples from 34 of the above patients, and c-erbB-2 mRNA was analysed by slot-blot hybridisation. c-erbB-2 mRNA was detectable in all samples, but papillary carcinomas and lymph node metastases showed significantly higher levels of c-erbB-2 mRNA compared to non-neoplastic tissue. The present demonstration of positive c-erbB-2 immunostaining in papillary thyroid carcinomas is contradictory to previous findings on formalin-fixed, paraffin-embedded material, and emphasises the importance of tissue quality for c-erbB-2 protein detection.

Reorganization of the cytoskeleton and morphological changes induced by 1,25-dihydroxyvitamin D3 in C3H/10T1/2 mouse embryo fibroblasts: relation to inhibition of proliferation

The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3) on cell morphology, the cytoskeleton, and fibronectin were studied in three lines of C3H/10T1/2 mouse embryo fibroblasts in which the antiproliferative effect of the hormone had previously been investigated. We showed that 1,25(OH)2D3 induced morphological changes in the nontransformed C3H/10T1/2 Cl 8 cells, which flattened and spread out markedly. Visualization of actin and tubulin by immunocytochemistry disclosed a reorganization of the microfilament and microtubular systems. 1,25(OH)2D3 also induced an increase in cell-surface-associated fibronectin. These changes were only slight in the transformed cell line C3H/10T1/2 Cl 16 and absent in the transformed C3H/10T1/2 TPA 482 cell line. These effects were correlated with the growth inhibition induced by the hormone, and this suggests a possible relationship between the 1,25(OH)2D3-induced alterations of cell shape and of the cytoskeleton and the effects of the hormone on cell proliferation.

Regulation of cell growth, c-myc mRNA, and 1,25-(OH)2 vitamin D3 receptor in C3H/10T1/2 mouse embryo fibroblasts by calcipotriol and 1,25-(OH)2 vitamin D3

Calcipotriol is a synthetic 1,25-(OH)2D3 analogue with high affinity for the 1,25-(OH)2D3 receptor, but with a lower affinity than 1,25-(OH)2D3 for vitamin D binding protein in serum. The inhibitory action of calcipotriol and 1,25-(OH)2D3 on proliferation of C3H/10T1/2 mouse embryo fibroblasts was examined in the non-transformed cell line Cl 8 and in the two transformed, tumorigenic cell lines Cl 16 and TPA 482. Upon exposure to 10 nmol/l calcipotriol or 1,25-(OH)2D3, the proliferation of Cl 8 cell line was almost completely suppressed, whereas both hormones had no effect on the cell lines Cl 16 and TPA 482. Calcipotriol was at least as effective as 1,25-(OH)2D3 in inducing up-regulation of the 1,25-(OH)2D3 receptor. Displacement studies showed no difference between calcipotriol and 1,25-(OH)2D3 in the affinity for the receptor present in Cl 8 or Cl 16 cell extracts. Furthermore, the inhibition of cell growth in Cl 8 cells by calcipotriol was not accompanied by any consistent change in the steady-state expression of c-myc mRNA. In conclusion, calcipotriol had potent growth inhibitory effect on the non-transformed cell line similar to 1,25-(OH)2D3. In the transformed cell lines, calcipotriol did not inhibit proliferation despite potent up-regulation of the 1,25-(OH)2D3 receptor.

A nonradioactive assay for N5-methyltetrahydrofolate-homocysteine methyltransferase (methionine synthase) based on o-phthaldialdehyde derivatization of methionine and fluorescence detection

The enzyme N5-methyltetrahydrofolate-homocysteine methyltransferase (methionine synthase, EC 2.1.1.13) catalyzes the conversion of homocysteine to methionine in the presence of a reducing system. N5-Methyltetrahydrofolate serves as a methyl donor in this reaction. An assay for the enzyme is described, which is based on methionine quantitation by o-phthaldialdehyde (OPA) derivatization and reversed-phase liquid chromatography. The enzymatic reaction is linear for at least 120 min under reducing conditions (125 mM 2-mercaptoethanol) and running the assay below an oil layer. This reducing system does not interfere with formation of the methionine-OPA adduct, which is separated from interfering compounds and an internal standard (norvaline) by a mobile phase adjusted to pH 5.0. The inclusion of internal standard increases the precision of the assay and corrects for the variable fluorescence yield due to occasional inaccurate pH adjustment before the derivatization step. Norvaline was suitable for this purpose because it elutes close to methionine and is not a natural amino acid present in biological extracts. This nonradioactive assay for methionine synthase was evaluated by comparison with a conventional method based on isolation of radioactive methionine by anion-exchange chromatography and by determination of enzyme activity in extract from cultured cells and liver.

Effect of 1,25-(OH)2-vitamin D3 on growth, homologous receptor and c-myc regulation in C3H/10T1/2 cells

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) receptor concentration, cell proliferation, and the steady-state level of c-myc mRNA were examined in the C3H/10T1/2 mouse embryo fibroblasts, before and after exposing the cells to 1,25-(OH)2D3. The non-transformed, logarithmically growing C3H/10T1/2 Cl 8 cells contained a high concentration of 1,25-(OH)2D3 receptor (164 fmol/mg of protein). An up-regulation of the 1,25-(OH)2D3 receptor and a potent inhibition of cell growth were observed by exposing the cells to 10 nM 1,25-(OH)2D3. The concentration of 1,25-(OH)2D3 receptor in the two chemically transformed, tumorigenic cell lines. C3H/10T1/2 Cl 16 and C3H/10T1/2 TPA 482, was 218 and 63 fmol/mg of protein, respectively. In the two transformed cell lines, 10 nM 1,25-(OH)2D3 had only negligible effect on cell growth. In the Cl 16 cells, an up-regulation of the 1,25-(OH)2D3 receptor was demonstrated, but only a weak up-regulation was found in the TPA 482 cells by the 1,25-(OH)2D3 treatment. No major changes were found in c-myc mRNA levels by the 1,25-(OH)2D3 treatment. Despite inhibition of cell growth, the steady-state level of c-myc mRNA was slightly induced (35%, mean) in the Cl 8 cells compared to control cells. In the transformed cells, no consistent change of the c-myc level was found. In contrast to earlier reports, we did not find any correlation between the 1,25-(OH)2D3 receptor and c-myc level, nor did we find any decrease of c-myc mRNA by 1,25-(OH)2D3 treatment in the C3H/10T1/2 fibroblasts.

Co-expression of the genes encoding transforming growth factor-alpha and its receptor in papillary carcinomas of the thyroid

Transforming growth factor-alpha (TGF-alpha) is frequently coexpressed with its receptor, epidermal growth factor receptor (EGF-R), in several types of carcinoma and sarcoma. It is believed that this results in an autocrine stimulation of tumor growth in these tumors. We have found that TGF-alpha and EGF-R/c-erbB RNAs were co-expressed at significantly higher levels in papillary thyroid carcinomas and their lymph-node metastases than in non-neoplastic thyroid tissues. We also observed a low level of expression of RNA specific for insulin-like growth factor I in these tumors, which was highest in a lymph-node metastasis. Autocrine stimulation by TGF-alpha may thus be a common feature of papillary carcinomas of the thyroid. Since EGF is known to induce proliferation and dedifferentiation of normal thyroid cells in culture, TGF-alpha and its receptor may play an important role in thyroid carcinogenesis.

Structural changes in the ribosomal genes of immortalized and transformed mouse embryo C3H/10T1/2 cell lines

Comparative studies of DNA isolated from adult C3H mouse liver, immortalized mouse embryo cells (C3H/10T1/2 Cl 8) and the tumorigenic methylcholanthrene transformed C3H/10T1/2 Cl 16 cell line have been carried out in order to analyze possible structural changes in the ribosomal genes associated with the immortalization and tumorigenic transformation of mouse cells. Southern blot hybridization experiments revealed a mutation hotspot within repetitive sequences 13 kb upstream from the 18S rRNA genes in the non-transcribed spacer (NTS). Other DNA changes were localized near the initiation and termination regions of rRNA transcription. The differences found in the restriction maps of the 5'-region resided 5 to 6 kd upstream from the 18S 5'-end and the changes located in the 3'-end mapped approximately 5 kb downstream from the 28S 3'-end. Thus, oncogenic transformation of the C3H/10T1/2 Cl 8 cells by methylcholanthrene treatment was associated with stable genetic changes in the 18S rRNA gene. There was no evidence for rRNA gene amplification.

Absence of abnormalities of the c-erbB-1 and c-erbB-2 proto-oncogenes in human thyroid neoplasia

The c-erbB-1 and c-erbB-2 proto-oncogenes are frequently activated by gene amplification and overexpression in a variety of human cancers. In an analysis of a large series of benign and malignant thyroid tumours, no abnormalities of structure or expression of either of c-erbB-1 or c-erbB-2 were found. Activation of these oncogenes is not a necessary event in neoplasia of this epithelial system.

Ouabain-resistant (Na+,K+)-ATPase enzyme activity in chemically induced ouabain-resistant C3H/10T1/2 cells

To further understand the molecular nature of changes leading to chemically induced ouabain resistance in C3H/10T1/2 Cl 8 (10T1/2) cells, we isolated plasma membranes from wild-type and ouabain-resistant (Ouar) 10T1/2 cells and characterized (Na,K)-ATPase activity in the plasma membrane fraction. (Na+,K+)-ATPase enzyme activity in membrane fractions extracted from wild-type 10T1/2 cells was inhibited in a concentration-dependent manner by ouabain and was completely inhibited by 2.4 mM ouabain. Lineweaver-Burke and Eisenthal/Cornish-Bowden analysis indicated that the inhibition was uncompetitive. Ten to 45% of (Na+,K+)-ATPase enzyme activity extracted from three Ouar 10T1/2 cell lines cultured in 1 mM ouabain was resistant to 2.4 mM ouabain, depending on the cell line. Resistance of (Na+,K+)-ATPase activity in the plasma membrane fraction of Ouar cells to inhibition by ouabain and resistance of cultured Ouar cells to the cytotoxicity of ouabain occurred over similar concentrations of ouabain (0.1-3mM). Two ouabain-resistant cell lines, Ouar MNNG Cl 2 and Ouar MCA Cl 16-7, demonstrated the same total (Na+,K+)-ATPase specific activity as 10T1/2 cells, but the fraction of Ouar enzyme activity increased (from 18 to 40% in MNNG Cl 2 cells and from 10 to 25% in Sp Ouar Cl 16 cells) when the cells were cultured in ouabain. Thermal denaturation profiles and pH dependence profiles of (Na+,K+)-ATPase activity in plasma membranes from wild-type and Ouar 10T1/2 cells were identical. A 3.9-kb (Na,K)-ATPase alpha subunit mRNA transcript was found in 10T1/2 cells, and in the Ouar MNNG Cl 2 cell line cultured in the presence or absence of ouabain. There was no amplification of the gene coding for the alpha subunit of (Na+,K+)-ATPase in the chemically induced Ouar MNNG Cl 2 cell line, whether this cell line was cultured in the presence or absence of ouabain. These studies provide further evidence that the Ouar phenotype of chemically induced and spontaneous Ouar 10T1/2 cell lines derives from Ouar (Na+,K+)-ATPase activity, and that this Ouar (Na+,K+)-ATPase activity increases further in some cell lines cultured in the presence of ouabain.

Expression of oncogenes in thyroid tumours: coexpression of c-erbB2/neu and c-erbB

The receptor-type oncogenes c-erbB2/neu and c-erbB have been found amplified and/or overexpressed in a number of tumours of epithelial origin. We have studied the expression of oncogenes in biopsies from human thyroid tumours. The c-erbB2/neu and c-erbB oncogenes showed two- to three-fold higher levels of RNA in papillary carcinomas and lymph node metastases as well as in one adenoma when compared to non-tumour tissue. The nuclear oncogenes c-myc and c-fos were found to be expressed at varying levels in both non-tumour and tumour tissue. RNA transcripts specific for the platelet-derived growth factor A and B chains and the N-ras oncogene were detected in one anaplastic carcinoma. Neither rearrangements nor amplifications of oncogenes were observed in the thyroid tumours. These data are particularly interesting in light of the recent findings that epidermal growth factor induces proliferation and dedifferentiation of normal thyroid epithelial cells in vitro. We suggest that the epidermal growth factor or other ligands for the c-erbB and c-erbB2/neu receptors may contribute to the development and/or maintenance of the malignant phenotype of papillary carcinomas of the thyroid.

Growth support and toxicity of homocysteine and its effects on methionine metabolism in non-transformed and chemically transformed C3H/10T1/2 cells

The effects of homocysteine (Hcy) on one non-transformed (Cl 8) and two malignant clones (Cl 16 and Cl T422) of the C3H/10T1/2 mouse embryo fibroblasts, were examined with regard to toxicity, ability to support growth and effects on methionine (Met) metabolism and glutathione level. Homocysteine in its reduced form (Hcy-SH) was toxic to all cell lines, and the LD90 was estimated to be 1.0 X 10(-4) M for Cl 8 and Cl 16 cells measured by plating efficiency, 0.8 X 10(-4) M for Cl 8 and 0.3 X 10(-4) M for Cl 16 when measured by total cell growth. At toxic concentrations, Hcy-SH showed a drastic effect on cell morphology both in the presence and absence of Met. The same effect was demonstrated with L-cysteine. No toxic effect was seen with homocystine (Hcy-SS-Hcy) or homocysteine thiolactone (Hcy-tl) at similar concentrations. Hcy-tl supported growth of both the non-transformed and malignant cells in Met-deficient medium but with decreasing efficiency in the order Cl 8, Cl 16 and Cl T422. The growth rate constant compared to that of Met-supplemented medium was 0.62 for Cl 8, 0.44 for Cl 16 and 0.38 for Cl T422 cells. The intracellular level of S-adenosylhomocysteine (AdoHcy) increased in all three cell lines in Hcy-tl-supplemented medium. The S-adenosylmethionine (AdoMet) content increased in Cl 8 cells, was constant in Cl 16 cells and decreased in Cl T422 cells under the same conditions. This resulted in a constant ratio of AdoMet/AdoHcy in the non-transformed cells (Cl 8) whereas this ratio decreased by 40% in Cl 16 and by 72% in Cl T422 cells when Hcy-tl replaced Met in the medium. The ability of Hcy-tl to support growth thus seemed to correlate well with alteration in Met metabolism in this cell culture system. The intracellular level of glutathione (GSH) was measured during exponential growth, but showed small variations between non-transformed cells and Cl 16 cells. However, Cl T422 cells showed a distinct lower level of GSH in Met-supplemented medium, and this increased 3- to 4-fold when Met was replaced with Hcy-tl.

Evidence that neomycin inhibits binding of herpes simplex virus type 1 to the cellular receptor

The effect of neomycin, a phosphoinositide-binding aminoglycoside, on herpes simplex virus type 1 (HSV-1) infection of BHK cells was studied. We showed earlier that it specifically inhibits HSV-1 production but not HSV-2 production (Langeland et al., Biochem Biophys. Res. Commun. 141:198-203, 1986). We now show that neomycin had no effect on cellular protein synthesis, as judged by the appearance of 35S-labeled polypeptides separated by polyacrylamide gel electrophoresis. Virus-induced polypeptides, however, were strongly inhibited at neomycin concentrations above 2 mM. Comparison among different aminoglycosides showed a variation in inhibition of HSV-1 production that paralleled the cationic charge of the aminoglycosides. HSV-1 receptor binding at 4 degrees C was completely inhibited by neomycin. At 37 degrees C both receptor binding and internalization, as measured by an indirect assay, appeared to be inhibited by more than 90%. The effect of neomycin on the infection was almost immediate upon the addition of the drug and preceded virus internalization. Possible mechanisms of the neomycin effect are discussed.

Biological and biochemical characterization of cell lines derived from initiation-promotion transformed C3H/10T1/2 cells

A two-stage transformation protocol was used to chemically transform the mouse embryo fibroblasts, C3H/10T1/2 Cl 8. To initiate the cells 0.37 microM 20-methylcholanthrene was used and 0.17 microM of the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate was employed to complete the transformation process. Six weeks later transformed foci were identified and isolated by the ring-cloning technique. Altogether eight different foci were trypsinized resulting in a total of 12 morphologically transformed subclones. Three of these clones, designated TPA 41, TPA 42 and TPA 482, have been characterized in detail. Their growth morphologies were different. The TPA 482 cells grew in a criss-cross pattern with piled up foci, thus showing a characteristic type III morphology. The TPA 482 clone did not show cell-density growth inhibition and grew in soft agar. The TPA 41 and TPA 42 clones exhibited cell-density growth inhibition, grew as monolayers and formed only few colonies in soft agar. Late passages of the TPA 42 clone acquired growth characteristics similar to TPA 482. The C3H/10T1/2 Cl 8 and the TPA 41 cells were not tumorigenic when transplanted into syngeneic mice. TPA 482 cells were strongly tumorigenic, producing tumors in 6/6 mice in 21 days. The TPA 42 cells were also tumorigenic, the first tumors appearing after 4 weeks; all animals injected with TPA 42 cells had tumors after 8 weeks. All tumors observed appeared to be fibrosarcomas. Flow cytometric analysis indicated differences in DNA distributions between tumor cells grown in vitro and the tumors in vivo. Two-dimensional gel analysis of the total cellular and the nuclear proteins showed an increase in the TPA 42 and TPA 482 cells of an acidic 48,000 and a basic 83,000 mol. wt polypeptides, and a decrease of a neutral polypeptide of mol. wt 46,000, located in the nucleus of TPA 482 cells.

Cell transformation and promoter activity of insulation oils in the Syrian hamster embryo cell and in the C3H/10T1/2 mouse embryo fibroblast test systems

The ability of mineral-oil-based and synthetic cable insulating fluids to transform and promote transformation of mammalian cells in vitro have been studied. In experiments with the Syrian hamster embryo cell transformation assay, it was found that C15-C18 alkylbenzenes were the most potent inducers of transformation, followed by low-viscosity and residual mineral oils. No activity and low cytotoxicity were found for a low-viscosity polyisobutylene-based oil. In the two-stage transformation assay of C3H/10T1/2 cells, promoter activity was obtained with all fluids tested. A blend of residual and low-viscosity mineral oils showed the highest activity. This oil possessed a low cytotoxicity and was tested at a relatively high concentration. The alkylbenzenes were more potent than the polyisobutylene-based fluid. The alkylbenzenes were also found to possess initiating activity in the two-stage assay, when 12-O-tetradecanoylphorbol 13-acetate (TPA) was used as promoter. All the fluids showed low potency compared to benzo[a]pyrene and the tumor promoter TPA.

Ornithine decarboxylase activity in foetal rat brain cells and in the mouse embryo fibroblasts C3H/10T1/2 CL8 cells: differences in response to medium change and to the tumor promoter TPA

12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced ornithine decarboxylase (ODC, EC 4.1.1.17) in normal, preneoplastic and malignant rat brain cells in culture, but treatment with phorbol, acetate or medium shift resulted in a similar response. Medium shift induced ODC activity in C3H/10T1/2 CL8 cells 4 and 12 hr after treatment. TPA induced only the 12 hr peak. ODC induction in C3H/10T1/2 CL8 cells was completely inhibited by cycloheximide and actinomycin D. Addition of alpha-amanitin abolished the 12 hr peak, but the TPA induced ODC activity was only partly inhibited. ODC induction by TPA was lower in C3H/10T1/2 CL8 cells initiated with 3-methyl-cholanthrene (MCA). ODC increased with TPA up to 10(-7) M and decreased at higher concentrations of TPA.