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C J Conti

Publications and source records attributed to C J Conti.

At least 91 records · Page 5Linked to original sources
PubMed1994

Altered expression of transforming growth factor-beta 1 mRNA and protein in mouse skin carcinogenesis.

Transforming growth factor (TGF)-beta 1, whose gene is located on mouse chromosome 7, has been proposed to be involved in skin carcinogenesis. In the study presented here, we demonstrated that single topical treatments with different types of tumor promoters, i.e., the protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA, 2 micrograms); the non-protein kinase C activators anthralin (22.6 micrograms), benzoyl peroxide (20 mg), and cumene hydroperoxide (1.2 mg); the first-stage tumor promoters 4-O-methyl-TPA (500 micrograms) and A23187 (166 micrograms); and the second-stage tumor promoter mezerein (2 micrograms) produced transient induction of TGF-beta 1 mRNA in SSIN (inbred SENCAR) mouse skin. The time of maximum induction varied from 3 to 12 h; the relative extent of induction was ranked as cumene hydroperoxide > benzoyl peroxide > anthralin > TPA > 4-O-methyl-TPA > mezerein > A23187. These findings suggested that TGF-beta 1 mRNA induction is a common response of skin to several types of complete and stage-specific promoters; however, the extent of induction did not correlate with the reported hyperplastic activity of single applications of these promoters. We also demonstrated that TGF-beta 1 mRNA expression in papillomas of SENCAR mice generally correlated with expression levels of cyclin D1, another gene on chromosome 7, and with stage of tumor progression. TGF-beta 1 mRNA expression was constitutively elevated in most squamous cell carcinomas from either initiation-promotion or complete carcinogenesis protocols. Cell lines established from carcinomas also overexpressed TGF-beta 1 mRNA. Immunohistochemical staining of tissue sections of normal and TPA-treated skin revealed the presence of extracellular TGF-beta 1 protein in the dermis and intracellular TGF-beta 1 protein in the epidermis, especially in the suprabasal layers. The staining patterns of papillomas varied, with 62 +/- 13% of the tissue showing strong intracellular staining but only 25 +/- 8% of the connective tissue staining for extracellular TGF-beta 1. Variable staining patterns were also found in carcinomas; some areas stained heavily for both the intracellular and extracellular forms of TGF-beta 1. Overall, 28 +/- 6% of the tissue of the 12 analyzed carcinomas stained for the intracellular form and 18 +/- 5% for the extracellular form of TGF-beta 1.

Animals↗
PubMed1994

Expression of keratins in mouse vaginal epithelium.

In the epithelium of the rodent vagina proliferation and differentiation are tightly regulated by ovarian hormones. Estrogens stimulate proliferation and squamous differentiation, whereas progesterone redirects differentiation to a mucus-secreting epithelium formed by goblet-like cells. In the present study, we used monospecific keratin antibodies to show the expression and distribution of keratins in SENCAR mouse vaginal epithelium in different stages of the estral cycle and in ovariectomized animals. In ovariectomized animals, the vaginal epithelium expressed K6, K8, K13 and K14, but not K1. After estrogen treatment, K1 was expressed. During proestrus and estrus, the keratin pattern was essentially identical to that observed in 17 beta-estradiol-stimulated animals. In contrast, during the progestational stages (metaestrus and diestrus) or after progesterone treatment of ovariectomized mice, the most relevant change was the loss of K1. Together, these results show that K1 expression is induced by estrogens in the vaginal epithelium. In contrast, K6, K8, K13 and K14 are constitutively expressed even when squamous differentiation is not observed.

Animals↗
PubMed1994

Induction of cyclin D1 overexpression by activated ras.

Activated ras genes are known to alter control of cell proliferation. This is consistent with the fact that ras proteins are a key component of the biochemical pathway triggered by ligand-bound cell surface receptors that are tyrosine kinases. Although an important part of the ras signaling pathway has been recently uncovered, the molecular target(s) that mediates the effects of ras on cell cycle control remains unknown. Cyclins and cyclin-dependent kinases are key molecules in the control of cell cycle. Cyclin D1, in particular, is a critical target for proliferative signals in G1 and it has been shown that ectopic overexpression of this cyclin can significantly alter cell cycle regulation. Here we report that activated ras induces significant overexpression of cyclin D1 in epithelial cells derived from normal rat intestine and mouse mammary gland. A definitive causal role for activated ras in this overexpression is demonstrated by using intestinal cells transfected with an inducible ras expression vector. Treatment of the ras-transformed intestinal clones with anti-sense cyclin D1 oligonucleotides reduces their rate of cell proliferation indicating that the increment in cyclin D1 expression induced by activated ras is instrumental in the higher rate of cell proliferation conferred by the ras oncogene to the IEC cells. Based on these results we propose that, at least in certain cell types, cyclin D1 can be one of the mediators of the transforming action of activated ras.

Animals↗
PubMed1994

Inhibition of tumorigenicity of a murine squamous cell carcinoma (SCC) cell line by a putative tumor suppressor gene on human chromosome 7.

Alterations in oncogenes and tumor suppressor genes (TSG) are considered to be critical steps in oncogenesis. However information on putative TSG involved in the development of squamous cell carcinomas (SCC) is very limited. In this study we confirmed the existence of a tumor suppressor gene (TSG) on human chromosome 7 (hchr 7) that suppresses the tumorigenicity of squamous cell carcinomas (SCCs). We injected seven clones of CH72 cells (a murine SCC-derived cell line) bearing a hchr 7 (CH72/hchr 7) introduced by microcell fusion, two clones bearing human chromosome 12 (CH72/hchr 12) and parental CH72 cells into athymic Balb/c nude mice. The sizes of the tumors were determined twice a week until tumors reached 12 mm diameter. In situ hybridization for centromeric repetitive sequences of the transferred chromosomes were performed on the cell lines injected and the tumors arising after the injection. Southern blots and polymerase chain reaction (PCR) amplifications of near terminal sequences and (CA) microsatellite repeats were done to test the integrity of the introduced chromosomes. Five out of seven CH72/hchr 7 clones had a twofold and threefold longer latency periods than CH72 cells. The remaining CH72/hchr 7 clones (MF 6 and 13 no. 4) had latency periods similar to that of parental CH72; MF 6 had a deletion in the introduced chromosome 7 involving q31.3-q31.3, whereas the other hybrid (MF 13 no. 4) seemed to have an intact hchr 7. Tumor-derived cells from CH72/hchr 7 hybrids with a delayed latency had lost centromeric and telomeric sequences of Chr 7. In contrast, tumors derived from the MF 6 and MF 13 no. 4 as well as the CH72/hchr 12 clones retained the introduced human chromosome as shown by chromosome 7 or 12 centromeric and telomeric sequences. These results indicate that the tumorigenicity of CH72 murine SCC cells was suppressed by hchr 7 and that the CH72/hchr 7 regain the tumorigenic phenotype after loss of the introduced chromosome, suggesting the presence of a TSG on hchr 7.

Animals↗
PubMed1993

p53 protein accumulation and gene mutation in the progression of human prostate carcinoma.

BACKGROUND: Nuclear accumulation of p53 protein has been shown to be strongly associated with missense p53 mutations. Studies of nuclear accumulation of p53 protein in prostate carcinoma cells have to date been confined to material from primary tumors. PURPOSE: We studied the accumulation of p53 protein in specimens obtained from primary and metastatic sites of prostate carcinoma. By examining the accumulation of this protein as a function of stage, histologic grade, and androgen responsiveness of the tumor, we hoped to determine the role of p53 mutation in the progression of prostate carcinoma. METHODS: The accumulation of the p53 protein in the cell nuclei was determined by immunohistochemical methods using polyclonal antibody to human p53 CM-1. The material studied consisted of formalin-fixed, paraffin-embedded tissue obtained from primary tumors and metastases of 92 patients with prostate carcinoma. Twelve samples from 11 patients were analyzed for the presence of mutations within exons 5-8 of the p53 gene (also known as TP53) by polymerase chain reaction-single-stranded conformation polymorphism (PCR-SSCP) analysis. Sequence analysis was subsequently performed on DNA obtained by polymerase chain reaction amplification of PCR-SSCP reactions produced from six different specimens. The chi-square test, Fisher's exact test, and the Freeman Halton test were used for statistical analyses of the results. RESULTS: All tumors with p53 accumulation were metastatic (stage D), poorly differentiated, and androgen independent. Nuclear accumulation of p53 protein was strongly associated with stage (D2 versus D1 versus A-C, P < .0001), grade (Gleason score 8-10 versus 5-7, P < .003), and androgen sensitivity (androgen independent versus dependent, P < .0001). Logistic regression analysis demonstrated that androgen sensitivity predicted p53 outcome better than did stage (P < .0001) or grade alone (P < .006). There was a perfect concordance between the results obtained by PCR-SSCP analysis and the p53 protein accumulation determined by immunohistochemistry in the 12 samples studied. Mutation of the p53 gene was confirmed by sequencing DNA obtained from six specimens positive in the PCR-SSCP assay. CONCLUSIONS: p53 gene mutation is a late event in the progression of prostate cancer and is associated with advanced (metastatic) stage, loss of differentiation, and the transition from androgen-dependent to androgen-independent growth. IMPLICATION: Testing of prostate cancer biopsy specimens from metastatic sites for p53 protein accumulation and gene mutation may provide useful prognostic information and could influence the recommended course of treatment.

Adult↗
PubMed1993

Low frequency of codon 61 Ha-ras mutations and lack of keratin 13 expression in 7,12-dimethylbenz[a]-anthracene-induced hamster skin tumors.

Alterations in the pattern of keratin expression are a common feature of skin-tumor development. In this study, we investigated whether the loss of epidermal keratin 1 (K1) and its replacement by mucosal keratin 13 (K13) is unique to mouse skin tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) and 12-O-tetradecanoylphorbol-13-acetate (TPA), since it has been reported that human epidermal tumors do not exhibit aberrant expression of K13. With that purpose, we analyzed the keratin profiles of 16 DMBA-induced hamster skin tumors using monospecific antibodies against K1 and K13. Although all the tumors expressed K1, they also showed an overall tendency towards loss of this keratin; furthermore, none of the tumors expressed K13. Previous studies have suggested that the induction of K13 in mouse skin is related to the mutation of the Ha-ras gene by the initiating agent DMBA, a mutation consistently found in murine DMBA/TPA-induced tumors and rarely found in human skin tumors. Therefore, we also evaluated the tumors for the presence of codon-61 mutations by direct sequencing of DNA extracted from paraffin-embedded tissue sections. Only three tumors showed an A-->T transversion in the second nucleotide of Ha-ras codon 61. However, presence of the mutation did not correlate with K1 staining. Although hamster skin tumors were induced by the same initiator as were mouse skin tumors, hamster skin tumors did not show the same keratin profile. Moreover, their immunohistochemical expression of K1 and K13 and their codon 61 sequences resembled that of their human counterparts. These results suggest that the aberrant expression of K13 may be unique to murine skin. Furthermore, although codon 61 Ha-ras mutation appears to be related to keratin alterations in the mouse model, this mutation is not sufficient to produce the same biochemical changes in other species.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

Further studies on the influence of initiation dose on papilloma growth and progression during two-stage carcinogenesis in SENCAR mice.

The present study was designed to further evaluate the growth and progression of papillomas to squamous cell carcinomas (SCCs) in groups of animals receiving initiating doses of 7,12-dimethylbenz[a]anthracene (DMBA) producing relatively low papilloma yields following long term promotion (60 weeks) with 12-O-tetradecanoylphorbol-13-acetate (TPA). For comparison, groups of animals were initiated with various doses of DMBA and then promoted with mezerein (MEZ), benzoyl peroxide (BzPo) and chrysarobin (CHRY). Following initiation, groups of female SENCAR mice received the following promoter doses: TPA (1.0 or 2.0 micrograms per mouse); MEZ (2.0 micrograms per mouse); BzPo (20.0 mg per mouse); and CHRY (52.8 micrograms per mouse). The maximum papilloma to SCC conversion ratio obtained with TPA in the current study was 0.32. This value was in the range of maximum conversion ratios obtained with the other compounds: MEZ, 0.40; CHRY, 0.32 and BzPo, 0.19. In general, the highest papilloma to SCC conversion ratios observed with TPA as the promoter were obtained in groups that received the lowest doses of DMBA and had relatively low papilloma burdens. A comparison of papilloma to SCC conversion in groups of mice promoted with TPA, MEZ or CHRY and having similar papilloma yields, revealed very similar conversion ratios. Comparison of the BzPo group with a similar papilloma yield indicated that the conversion ratio was slightly lower with this promoter. The present results indicate that in mice promoted with TPA and having relatively low papilloma numbers, a larger proportion of these papillomas progress to SCCs during continued promoter treatment. Furthermore, the results suggest that papillomas behave similarly in their ability to progress to SCCs regardless of the promoter used when comparing groups of mice with similar tumor numbers. The data are discussed in terms of possible mechanisms for the observed results.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

Simultaneous PAGE, immunoblotting, and immunohistochemical analysis of differentiation associated keratins in lesions of the oral mucosa.

The expression of differentiation associated high PM Keratin polypeptides of the oral mucosa lesions were studied by immunohistochemical and immunoblotting techniques applied to adjacent sections of each biopsy specimen. The material studied included specimens of leukoplakia, verrucous carcinoma, squamous cell carcinoma, adenocarcinoma and keratoacanthoma. Little or no expression of 65-67 Kd keratins was evident in squamous cell carcinoma and adenocarcinoma. Hyperkeratotic (both benign and dysplastic) lesions such as verrucous carcinoma, leukoplakia, and keratoacanthoma, showed great variations in the intensity of 65-67 bands and a very irregular immunohistochemical staining pattern. Increased amounts of horny substance was usually accompanied by absence of, or decreased expression of 65-67 Kd keratins, thus indicating a change in the polypeptide composition of the horny layer in pathological conditions of the oral epithelium.

Adenocarcinoma↗
PubMed1993

Overexpression of cyclin D1 in mouse skin carcinogenesis.

Recent studies have provided evidence suggesting that disruption of cyclin function may play a critical role in tumorigenesis. Cyclin D1, a putative G1 cyclin previously isolated in human parathyroid adenomas (designated PRAD1) and mouse macrophages (designated Cyl1), has been implicated in various neoplasias including breast and squamous cell carcinomas (SCC). The role of cyclin altered regulation in the different stages of tumor progression has not been studied in a well defined animal model system. In the study presented here, Cyl1 was mapped to the distal end of mouse chromosome 7 and found to be dramatically overexpressed in skin SCC. In premalignant stages of tumor development, early papillomas showed basal Cyl1 transcript levels, whereas over-expression was observed in most advanced papillomas. These findings suggest that altered expression of cyclin D1 plays a critical role in mouse skin carcinogenesis and may be related to the acquisition of autonomous growth by papillomas. Further studies on the role of cyclin D1 in the mouse model system should prove valuable for understanding the multistep basis of tumor progression.

Animals↗
PubMed1992

Dissociation of sensitivities to tumor promotion and progression in outbred and inbred SENCAR mice.

The sensitivity of outbred SENCAR mice and inbred SENCAR (SSIN) mice to multistage carcinogenesis was studied. Tumors were induced using either 7,12-dimethylbenz[a]anthracene or N-methyl-N'-nitro-N-nitrosoguanidine as initiators and 12-O-tetradecanoylphorbol-13-acetate or benzoyl peroxide as promoting agents. Although the number of papillomas per mouse was higher in SSIN than in outbred SENCAR mice, the number of carcinomas observed in the SSIN strain was significantly lower regardless of the initiator or promoter used. It was also observed that the expression of markers of premalignant progression (i.e., dysplasia, expression of keratin K13, and loss of keratin K1 expression) was markedly suppressed in SSIN papillomas. After 50 wk of promotion with 12-O-tetradecanoylphorbol-13-acetate, the pattern of expression of K13 and K1 in SSIN mice was comparable to the pattern observed in outbred SENCAR mice after 10 to 20 wk of promotion with 12-O-tetradecanoylphorbol-13-acetate. It was also observed that 67% of the tumors induced in SSIN mice by initiation with 7,12-dimethylbenz[a]anthracene exhibited a mutation in codon 61 of the Ha-ras-1 gene. This latter finding suggests that the differences observed in tumor progression between the inbred strain and the outbred stock are not related to a genetic alteration in the Ha-ras-1 gene but rather to an independent event that we have postulated to involve a putative suppressor gene. The data reported here suggest that the putative gene(s) that confers susceptibility to tumor promotion was segregated from the gene(s) involved in tumor progression during selection and inbreeding of the SENCAR mouse stock.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

The effect of dietary fat on the rapid development of mammary tumors induced by 7,12-dimethylbenz(a)anthracene in SENCAR mice.

We recently reported (J. Leyton et al., Cancer Res., 51: 907-915, 1991) an inverse correlation between skin tumor number and level of dietary linoleic acid (LA) in SENCAR mice following an initiation-promotion protocol. These results differed from the reported (C. Ip et al., Cancer Res., 45: 1997-2001, 1985) positive correlation between dietary LA and tumor incidence for the rat mammary gland. The goal of the study reported here was to determine whether this dissimilarity was due to organ site or species differences. Female SENCAR mice were fed 1 of 3 15% fat diets containing LA at levels of 0.8, 4.5, and 8.4% before, during, and after intragastric administration of 6 mg (1 mg/week) 7,12-dimethylbenz(a)anthracene. A positive correlation between level of dietary LA and mammary tumor incidence was observed such that for the first 15 weeks, the incidence was greatest in the 8.4% LA diet group, followed by the 4.5% and then the 0.8% LA groups. Distinct dietary effects on latency were also noted in that 15, 12, and 8 weeks after cessation of 7,12-dimethylbenz(a)anthracene were required for a 40% carcinoma incidence in the 0.8, 4.5, and 8.4% LA diet groups, respectively. A histopathological analysis of all tumors revealed that the predominant type was the adenosquamous carcinoma, which comprised 46.6, 54.1, and 77.7% of all mammary tumors for diets containing 0.8, 4.5, and 8.4% LA, respectively. The second most common tumor was the adenocarcinoma type B, which was found with a frequency of 33% in the 0.8% and 4.5% LA diet groups and 22% in the 8.4% LA diet group. These results indicate that SENCAR mice have a short latency period for 7,12-dimethylbenz(a)anthracene-induced mammary tumor development and that rat and mouse mammary tumor development is modified by dietary LA in a similar manner, although in the SENCAR mouse dietary LA did not have a saturating effect. In addition, high dietary LA was found to be associated specifically with an increased incidence of adenosquamous carcinomas but not of other types of mammary tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Activating mutation of the Ha-ras gene in chemically induced tumors of the hamster cheek pouch.

The presence of an activating mutation in the Ha-ras gene in hamster cheek pouch tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) complete carcinogenesis was investigated. The normal sequence of a fragment of genomic DNA encompassing codon 61 of the Ha-ras gene was amplified by the polymerase chain reaction using primers designed for a highly conserved region of the mouse Ha-ras-1 gene. The sequence of the amplified fragment was determined by a direct sequencing technique and exhibited 83.3% and 87.5% homology with the corresponding human and mouse sequences, respectively. At the amino acid level, the sequence was identical among the three species. Paraffin sections of 11 squamous cell carcinomas of the cheek pouch were used to detect mutated Ha-ras alleles. DNA sequencing of the tumors showed that six of 11 tumors presented an A----T transversion in the second position of codon 61, resulting in an amino acid change from glycine to leucine. As has been demonstrated in other systems, we have shown a specific mutation of the Ha-ras gene in chemically induced tumors of the hamster cheek pouch, further supporting the role of this oncogene in chemical carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Aberrant expression of the simple epithelial type II keratin 8 by mouse skin carcinomas but not papillomas.

Keratins have been demonstrated to be suitable markers of changes taking place during epithelial neoplasia. Therefore, we analyzed 18 mouse skin tumors (nine papillomas and nine squamous cell carcinomas), induced either by two-stage carcinogenesis with 7,12-dimethylbenz[a]anthracene(DMBA)/12-O-tetradecanoylphorbol-13-acetat e or complete carcinogenesis with DMBA, by immunofluorescence with a monoclonal antibody to keratin (K) 8 (TROMA-1). Immunoperoxidase staining and immunoblotting were also used on selected tumor samples to further explore for the presence of K8. All of the papillomas tested were negative for the presence of K8, whereas the carcinomas were positive. The level of K8 expression in carcinomas showed a positive correlation with the degree of malignancy. Northern blot analysis using a K8 cDNA probe suggested that control of K8 expression in mouse skin tumors occurs at the transcriptional level. Double-label immunofluorescence staining using TROMA-1 and RK13 antibodies demonstrated that K8 did not generally colocalize with K13, a keratin normally found in internal stratified epithelial but aberrantly expressed in mouse epidermal tumors. Furthermore, tumors expressing high levels of K8 showed a reduced expression of K13. Histological examination of immunoperoxidase-stained tumors demonstrated that K8-positive cells were mainly found in anaplastic areas, whereas K13 foci were restricted to well-differentiated regions. Our results demonstrate that K8 expression is a marker of late stages of carcinoma progression in the mouse skin carcinogenesis model.

9,10-Dimethyl-1,2-benzanthracene↗