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C J Conti

Publications and source records attributed to C J Conti.

At least 73 records · Page 4Linked to original sources
PubMed1996

Novel susceptibility locus for mouse hepatomas: evidence for a conserved tumor suppressor gene.

We have identified previously a putative tumor suppressor gene (TSG) locus at human chromosome (hchr) 7q31 showing that it is altered in a variety of human epithelial tumors. To determine whether this TSG is conserved in mice, we studied loss of heterozygosity (LOH) in chemically induced mouse liver adenomas. The LOH analysis was performed by polymerase chain reaction amplification of 17 (CA)n microsatellite repeats on mouse chromosome (mchr) 6 A2-C3. Ninety-six of 106 cases (90.6%) had LOH at D6Mit50, and 89.5% had LOH at D6Mit179. These two loci are 0.2 cM apart on mchr 6A2. Another high-LOH site was found in the C3 band. The high incidence of LOH in the 7q-homologous segment of mchr 6 indicates that the human TSG is conserved and is involved in the development of hepatomas.

Animals↗
PubMed1996

Molecular genetic alterations as intermediate end points in chemoprevention studies.

It is generally accepted that carcinogenesis is related to the accumulation of genetic damage in somatic cells. In support of this concept, numerous studies have identified and characterized genes that are mutated or deleted in carcinogenesis. Some of these genetic alterations occur very frequently, and therefore it is theoretically possible to use them as diagnostic tools or as intermediate end points for chemoprevention studies. This is particularly relevant for some animal models, in which certain genetic alterations are found at a frequently close to 100%. In contrast, specific genetic alterations normally occur less frequently in human cancer, probably because humans are genetically more heterogeneous and are exposed to multiple carcinogens, tumour promoters, and other modifiers of carcinogenesis. Some genetic alterations occur early in tumour development, as in the case of ras mutations in some chemical carcinogenesis models. Similarly, p53 mutations also appear to be a frequent and early event in ultraviolet light (UV)-induced skin tumours in mice and possibly in humans. However, in other neoplasias such as prostate cancer, p53 alterations occur at late stages of tumour development. Alterations that occur early in neoplastic development may be valuable as early markers of tumour development, whereas those that occur late in development may be useful for determining the action of chemopreventive agents on tumour progression. Although the use of genetic markers as intermediate end points of cancer prevention studies has not been completely developed, it has great potential. The development of simple and sensitive molecular techniques such as the polymerase chain reaction and in situ hybridization has opened the possibility of using these markers in large-scale cancer prevention studies.

Animals↗
PubMed1996

Expression of G1 cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors in androgen-induced prostate proliferation in castrated rats.

Androgen induces prostate cell proliferation in the castrated rat. We hypothesized that G1 cyclins, cyclin-dependent kinases (cdk), and cdk inhibitors mediate this cellular response to mitogenic signals. In this study, induction of cyclins D1, D2, D3, E, and cdks 2, 4, and 6 expression was observed at various time points during testosterone replacement in the ventral prostate of castrated rats. The induction followed prostate epithelium proliferation, which peaked at 48 h and decreased at 120 h during the treatment. The study of cyclin/cdk complex formation revealed that more cyclin D1/cdk4 and cyclin D1/cdk6 complexes were formed at 48 h than at 120 h of treatment, but cyclin D1/cdk2 complexes remained the same. Furthermore, both hyperphosphorylated and hypophosphorylated forms of Rb were detected at 48 h, but only the hypophosphorylated form was detected at 120 h of treatment. p21Cip1, which was very abundant in the ventral prostate of castrated and intact rats, was not detected when the prostate started proliferation and increased gradually as proliferation decreased during the androgen treatment. Meanwhile, p27Kip1 dramatically increased after androgen treatment, and the induction levels were less at the peak of prostate proliferation and higher when proliferation was low. The results presented here suggest that expression of G1 cyclins and their related kinases and kinase inhibitors are well regulated after androgen replacement in the ventral prostate of castrated rats. The cooperation between these cell cycle regulators leads to a well-controlled prostate regeneration.

Animals↗
PubMed1995

Expression of a dominant negative mutant of epidermal growth factor receptor in the epidermis of transgenic mice elicits striking alterations in hair follicle development and skin structure.

Epidermal growth factor receptor (EGFR) is a key regulator of keratinocyte biology. However, the physiological role of EGFR in vivo has not been well established. To analyze the role of EGFR in skin, we have generated transgenic mice expressing an EGFR dominant negative mutant in the basal layer of epidermis and outer root sheath of hair follicles. Mice expressing the mutant receptor display short and waved pelage hair and curly whiskers during the first weeks of age, but subsequently pelage and vibrissa hairs become progressively sparser and atrophic. Eventually, most mice present severe alopecia. Histological examination of the skin of transgenic mice shows striking alterations in the development of hair follicles, which fail to enter into catagen stage. These alterations eventually lead to necrosis and disappearance of the follicles, accompanied by strong infiltration of the skin with inflammatory elements. The interfollicular epidermis of these mice shows marked hyperplasia, expression of hyperproliferation-associated keratin K6 and increased 5-bromo-2-deoxyuridine incorporation. EGFR function was inhibited in transgenic skin keratinocytes, since in vivo and in vitro autophosphorylation of EGFR was almost completely abolished on EGF stimulation. These results implicate EGFR in the control of hair cycle progression, and provide new information about its role in epidermal growth and differentiation.

Animals↗
PubMed1995

High susceptibility to ultraviolet-induced carcinogenesis in mice lacking XPC.

Compromise of genetic information by mutation may result in the dysregulation of cellular growth control and subsequent tumour formation. Xeroderma pigmentosum (XP) is a rare autosomal disease characterized by hypersensitivity of the skin to sunlight and > 1,000-fold increased risk of skin cancers in sun-exposed parts of the body. Cell fusion studies have revealed eight complementation groups in XP (A-G, and an XP-variant form); group C is one of the most common forms of the disease. We have isolated a mouse homologue of the human gene for XP group C and generated XPC-deficient mice by using embryonic stem cell technology. Mice homozygous for the XPC mutant allele (xpcm1/xpcm1) are viable and do not exhibit an increased susceptibility to spontaneous tumour generation at one year of age. However, xpcm1/xpcm1 mice were found to be highly susceptible to ultraviolet-induced carcinogenesis compared with mice heterozygous for the mutant allele (xpcm1/+) and wild-type controls. Homozygous xpcm1 mutant mice also display a spectrum of ultraviolet-exposure-related pathological skin and eye changes consistent with the human disease xeroderma pigmentosum group C.

Amino Acid Sequence↗
PubMed1995

Allelic loss at 7q31.1 in human primary ovarian carcinomas suggests the existence of a tumor suppressor gene.

We studied loss of heterozygosity (LOH) in chromosome 7q in order to determine the location of a putative tumor suppressor gene (TSG) in human epithelial ovarian carcinomas. Samples were obtained from 26 primary ovarian carcinomas at the time of staging laparotomy. Paired normal and tumoral DNAs were used as templates for polymerase chain reaction amplification of a set of 14 (C-A)n microsatellite repeats on 7q21-qter. All the cases studied presented LOH at one or more loci on 7q. Seventy-three percent LOH (in 14 of 19 informative cases) were detected in D7S522 at 7q31.1. The percentages of LOH were normally distributed around microsatellite D7S522 determining a smallest common deleted region of 1 cM. The high incidence of LOH in primary ovarian carcinomas suggests that a TSG relevant to the development of ovarian cancers is present at 7q31.1, confirming our previous functional evidence for a TSG in this region.

Adult↗
PubMed1995

Frequent loss of heterozygosity in human primary squamous cell and colon carcinomas at 7q31.1: evidence for a broad range tumor suppressor gene.

Consistent deletions and loss of heterozygosity (LOH) in polymorphic markers in a determinate chromosomal fragment are known to be indicative of a closely mapping tumor suppressor gene. Deletion of the long arm of chromosome 7 is a frequent trait in many kinds of human primary tumors. We studied LOH of 14 markers on chromosome 7q in order to determine the location of a putative tumor suppressor gene in human primary squamous cell carcinoma of the head and neck and in human primary colon carcinomas. Samples were obtained from 18 primary squamous cell carcinomas of the head and neck and 18 primary colon carcinomas surgically removed from patients at the Fox Chase Cancer Center. Loss of heterozygosity was studied performing PCR amplifications of a set of 14 CA microsatellite repeats encompassing 7q21-qter. Of 18 squamous cell carcinomas of the head and neck cases studied, 12 had LOH at one or more loci on 7q. Fifty-three percent of 15 informative cases had LOH of the CA microsatellite dinucleotide repeat marker D7S522 at 7q31.1-7q31.2. Eleven of 18 colon carcinoma cases had LOH of one or more markers assayed, and the maximum LOH (80% of 10 informative cases) was at D7S522. Distributions of percentage of LOH in both tumor types were normally distributed around microsatellite D7S522. The high incidence of LOH in both tumor types studied suggests that a tumor suppressor gene relevant to the development of epithelial cancers is present on the 7q31.1-31.2, confirming our previous functional evidence for a tumor suppressor gene on chromosome 7.

Carcinoma, Squamous Cell↗
PubMed1995

Human chromosome 11 inhibits tumorigenicity of a murine squamous cell carcinoma cell line.

Loss of heterozygosity (LOH) of mouse chromosome 7 has been consistently demonstrated in chemically induced murine squamous cell carcinomas (SCCs). The region of this chromosome presenting LOH in the mouse tumors is syntenic to human chromosome segments 11p15 and 11q. To determine whether the introduction of human chromosome (Hchr) 11 can suppress the growth of murine SCC, we injected four clones of a chemically induced murine SCC cell line bearing an Hchr 11 into athymic BALB/c nude mice. All microcell hybrid clones with Hchr 11 (CH72/Hchr 11) had latency periods twice as long as those of the parental CH72 cells and control hybrids containing a Hchr 12. Tumor-derived cells from CH72/Hchr 11 hybrids had lost centromeric and telomeric sequences from Hchr 11. All repressed cell lines grew significantly more slowly in vitro than did the controls. These results suggest that Hchr 11 contains a tumor-suppressor gene capable of inhibiting tumorigenicity in chemically induced SCC, confirming common pathways in the development of human neoplasias and the murine model.

Alleles↗
PubMed1995

Frequency and characterization of p53 mutations in clinically localized prostate cancer.

OBJECTIVES: To determine the frequency of abnormal p53 expression and to characterize confirmed p53 mutations in tumors from patients with clinically localized adenocarcinoma of the prostate. METHODS: p53 protein nuclear accumulation was determined immunohistochemically in the initial diagnostic tumor specimens from 37 patients with clinically localized prostate carcinoma. Two primary antibodies were used on all specimens. Structural analysis of the p53 gene was performed using the methods of polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) and DNA sequencing. RESULTS: In 1 of the 37 (2.7%) tumor specimens, intense p53 nuclear staining was demonstrated using either antibody PAb 1801 or CM-1. The staining in this case was heterogeneous, with approximately 40% of tumor nuclei staining for p53. This tumor specimen was microdissected and DNA was extracted. Following PCR amplification, abnormally migrating bands were noted on SSCP analysis of exon 8. DNA sequencing confirmed the mutation as a C-->A transversion in codon 281 (asp-->glu). PCR/SSCP analysis of exons 5 through 8 was also performed for seven additional tumors that were negative for p53 nuclear accumulation by immunohistochemical (IHC) methods. All of these specimens demonstrated wild-type p53. CONCLUSIONS: The results of this study confirm and extend our previous findings that p53 mutations are rare in clinically localized adenocarcinoma of the prostate. In detecting clonal p53 mutations, standard immunohistochemical technique correlates reliably with structural p53 gene analysis of the evolutionary conserved domains encompassing exons 5-8. Importantly, most reports have demonstrated that p53 mutations detected by IHC are a late step in the progression of prostate cancer and are associated with advanced disease, dedifferentiation, and the acquisition of androgen independence.

Adenocarcinoma↗
PubMed1995

The effect of dietary fermented milk products and lactic acid bacteria on the initiation and promotion stages of mammary carcinogenesis.

The effects of spray-dried yogurt powder product (YPP), bifidobacteria, and Lactobacillus acidophilus were studied during the initiation and promotion phases of carcinogenesis using the 7,12-dimethylbenz[a]anthracene (DMBA)-induced mouse mammary carcinogenesis model. In two separate studies, Sencar mice were fed a diet consisting of 86%, 43%, or 0% YPP or 0% YPP, but with added cultures of bifidobacteria or L. acidophilus. When the animals were 55-63 days old, DMBA was administered by intragastric gavage at 1 mg/mouse and continued once a week for six weeks. During the initiation study, the test diets were fed for four weeks before and during DMBA administration. One week after the final DMBA treatment, all animals were switched to a basal diet based on the AIN-76 formulation. For the promotion study, the diets were introduced one week after the final dose of DMBA and fed for the remainder of the study. Palpable tumor development was monitored weekly throughout the studies. For the initiation study, mice fed 86%, 43%, or 0% YPP or 0% YPP supplemented with bifidobacteria or L. acidophilus had a histologically verified mammary tumor incidence of 15%, 35%, 19%, 30%, and 20%, respectively. The histologically verified tumor incidence for the promotion study was 48%, 58%, 36%, 59%, and 43% in the mice fed diets consisting of 86%, 43%, or 0% YPP or 0% YPP supplemented with bifidobacteria or L. acidophilus, respectively. The data indicate that neither the initiation nor the promotion phase of carcinogenesis is significantly affected by diets composed of 86% YPP, 43% YPP, 0% YPP, or 0% YPP supplemented with bifidobacteria or L. acidophilus.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Early overexpression of cyclin D1 protein in mouse skin carcinogenesis.

Abnormal expression of cell-cycle regulatory proteins, particularly cyclin D1, has been described in human cancers. However, there are few reports of this kind in experimental carcinogenesis models, which provide a framework to analyze the importance of those alterations in early cancer development. Previous studies from our laboratory showed that cyclin D1 mRNA was overexpressed in skin tumors generated in SENCAR mice by a two-stage carcinogenesis protocol. In the study presented here, immunoprecipitation of fresh tumor samples confirmed the overexpression of cyclin D1 protein. We also developed an immunohistochemical technique to determine which cells in the lesions overexpressed the cyclin and the timing of deregulation during cancer development. Surprisingly, we found that all premalignant lesions, including small incipient papillomas, overexpressed cyclin D1, whereas normal and hyperproliferative skin were negative. Nuclear immunostaining was detected only in the proliferative compartments of the tumors and showed an apparent cell-cycle-related variation. These results provide evidence for a role of cyclin D1 overexpression in mouse skin carcinogenesis and support the use of this model as an alternative to in vitro studies to help understand the involvement of cyclin deregulation in cancer development.

Animals↗
PubMed1995

Positive immunohistochemical staining of p53 and cyclin D in advanced mouse skin tumors, but not in precancerous lesions produced by benzo[a]pyrene.

Squamous cell carcinomas (SCCs) of the mouse skin, as well as several types of preinvasive carcinoma precursor lesions, were produced by complete carcinogenesis protocols with benzo[a]pyrene (B[a]P). Groups of mice were studied histologically at several time points. Tumors and precursor lesions were systematically counted on microscope slides. The main feature of tumor development using this ubiquitous human carcinogen was the sequential appearance of in situ flat lesions with progressive degrees of dysplasia. These changes, preceding the development of SCCs, were observed 20 weeks after beginning the carcinogen treatments. At this time point, in situ lesions outnumbered SCC approximately 10:1 at the higher total carcinogen dose examined. Ten weeks later, this ratio was approximately 1:1. With the lower total carcinogen dose protocol, progression was delayed since at 27 weeks preinvasive lesions outnumbered SCCs approximately 8:1. In addition to the in situ lesions, papillomas and keratoacanthomas were noted with the high B[a]P dose protocol, but tended to disappear at the end of the experiment, also indicating their probable role as SCC precursors. A study of histochemical markers showed that gamma-glutamyltranspeptidase (GGT) and keratin 13, although good markers of malignant changes in early papillomas produced by two-stage carcinogenesis protocols, were mainly negative in dysplastic lesions produced by complete carcinogenesis with B[a]P. Immunohistochemical detection of p53 showed that 50% of SCCs were positively stained, whereas only 3% of in situ lesions were p53 immunoreactive. Similarly, 62% of SCCs were immunohistochemically positive for cyclin D, but no precursor lesions were positive. Molecular analysis of the tumors showed the absence of H-ras mutations. No amplification of the cyclin-D-1 gene was detected in eight SCCs examined. Collectively, these findings indicate that preinvasive in situ lesions are frequent during early stages of carcinogenesis when B[a]P is used in a complete carcinogenesis protocol. Although the absence of p53 immunoreactivity in this mouse model differs from the observed changes in human premalignant squamous lesions, the sequence of morphological changes and the final incidence of p53 and cyclin D staining abnormalities are very similar to the well-known alterations that take place during human squamous carcinogenesis.

Animals↗
PubMed1995

Genetic susceptibility to papilloma progression in SENCAR mice.

Previous results showed that in an inbred line (SSIN) derived from outbred SENCAR mice there is a dissociation between susceptibility to papilloma development and the malignant conversion of these into squamous cell carcinomas (SCC). To extend this conclusion, we designed an interstrain breeding experiment using the two-step carcinogenesis protocol in order to study the susceptibility to tumor progression of F1 offspring. The strains used were SSIN, BALB/c, both known for their resistance to papilloma progression, and SENCAR. Both the SSIN X SENCAR and SENCAR X SSIN F1s showed a promotion sensitivity similar to that of the SSIN mice. This behavior was also seen in the SSIN X (SSIN X SENCAR) and SSIN X (SENCAR X SSIN) backcrossed animals, suggesting that susceptibility to 12-O-tetradecanoylphorbol-13-acetate promotion under these protocol conditions is inherited as a dominant trait. The BALB/c X SENCAR F1s showed an average response that was intermediate between the two parental strains/stocks. Regarding the progression, all F1s showed a cumulative number of SCCs similar to the SENCAR progenitor. We also investigated the previously described switch of keratin 1 to 13 as a marker of premalignant progression, which is significatively delayed in SSIN mice compared with SENCAR mice. The SSIN X SENCAR F1s expressed this switch in a way similar to the SENCAR mice. These findings suggest that susceptibility to tumor progression is inherited as a dominant autosomal trait. The putative gene(s) that confers susceptibility is present in the SENCAR stock and was probably lost in the selection and inbreeding of the SSIN mice.

Animals↗
PubMed1995

Induction of short-term biomarkers of tumor promotion in skin of CD-1 mice by petroleum middle distillates: preliminary observations.

The induction of sustained epidermal hyperplasia in mouse skin has been shown to be a reliable predictor of tumor promoting activity for chemicals as diverse as phorbol esters, anthralins, n-dodecane and organic peroxides (DiGiovanni, 1992). The results contained herein demonstrate that API 81-07 and API 81-10, petroleum middle distillates that exhibit tumor promoting activity in mouse skin, induce epidermal hyperplasia and ODC activity. Other petroleum middle distillates (odorless light petroleum hydrocarbons, a light vacuum distillate, and a mineral seal oil) were also shown to share these activities. It should be emphasized that the relevance of these observations to human skin remains unresolved; however, the availability of these short-term biomarkers offers the opportunity to address the issue by performing comparative investigations on the effects of petroleum middle distillates on human skin xenografted to athymic (nude) mice. Such studies are being initiated.

Alkanes↗
PubMed1994

Loss of heterozygosity in human primary prostate carcinomas: a possible tumor suppressor gene at 7q31.1.

We studied loss of heterozygosity (LOH) on human chromosome 7q to determine the location of a putative tumor suppressor gene (TSG) in human primary prostate carcinomas. Samples were obtained from 16 primary prostate carcinomas surgically removed from patients at The University of Texas M. D. Anderson Cancer Center. Paired normal and tumor DNAs were used as template for PCR amplification of a set of 14 CA microsatellite repeats on 7q21-qter. Twelve of 16 cases studied had LOH at one or more loci on 7q. Eighty-three percent LOH (five of six informative cases) was detected with D7S522 at 7q31.1-7q31.2. Percentage of LOH was normally distributed around D7S522. The high incidence of LOH in primary prostate carcinomas suggests that there is a TSG relevant to the development of prostate cancers at 7q31.1-31.2, confirming our previous functional evidence for a TSG at this location. Further research needs to be conducted to establish the identity and function of this putative TSG.

Carcinoma↗
PubMed1994

(C-A)n microsatellite repeat D7S522 is the most commonly deleted region in human primary breast cancer.

Loss of heterozygosity in human chromosome 7q was studied to determine the location of a putative tumor suppressor gene. Twenty-six of 31 cases studied presented loss of heterozygosity at one or more loci on chromosome 7q. Eighty-three percent loss of heterozygosity (in 11 informative cases) was detected by using the (C-A)n microsatellite repeat marker D7S522 at 7q31.1-7q31.2. These results suggest that a tumor suppressor gene relevant to the development of breast cancer is present in the 7q31.1-7q31.2 region, confirming our previous evidence for a tumor suppressor gene in this chromosome and frequent deletions of the long arm in human primary breast cancers.

Alleles↗
PubMed1994

Transforming growth factor-beta 1 expression in Syrian hamster cheek pouch carcinogenesis.

The expression pattern of transforming growth factor-beta 1 (TGF-beta 1) during the stages of complete carcinogenesis in the hamster cheek pouch model was studied. The right cheek pouches of 18 male hamsters were treated with 0.5%, 7,12-dimethylbenz[a]anthracene (DMBA) for 16 wk. TGF-beta 1 was detected immunohistochemically in the resulting samples with two different polyclonal monospecific antibodies that recognize intracellular and extracellular forms of TGF-beta 1. In the normal cheek pouch, extracellular protein stained the corium strongly, but the reaction was not evenly distributed. As treatment progressed, the reaction increased in both area and intensity; the peak was reached at 8 wk. Intracellular TGF-beta 1 expression followed a similar pattern, with a peak at 4 wk of treatment. The results of northern blot analysis were concordant with the immunohistochemical results. Overexpression of TGF-beta 1 was also observed in the malignant tumors, but only the extracellular form of the protein was present; intracellular TGF-beta 1 was not detected in these tumors. The expression of TGF-beta 1 in this carcinogenesis model seems to have two formal stages, the first being an overexpression step as a reaction to the uncontrolled growth and the second being one in which tumors have no internal expression of TGF-beta 1 but in which external protein accumulates in the surrounding stroma. A possible explanation of this paradox may be that TGF-beta 1 has functions other than its growth-repressing activity.

9,10-Dimethyl-1,2-benzanthracene↗