PubMed Health⌕ Search

Biomedical subjects

C M Aldaz

Publications and source records attributed to C M Aldaz.

At least 37 records · Page 2Linked to original sources
PubMed1996

Deletion map of chromosome 16q in ductal carcinoma in situ of the breast: refining a putative tumor suppressor gene region.

Allelic losses or imbalances affecting chromosome arm 16q appear to be early genomic abnormalities in breast carcinogenesis, because they were observed in a significant number of breast ductal carcinoma in situ lesions in our previous study (Aldaz et al., Cancer Res., 55: 3976-3981, 1995). To define the minimum region of loss of heterozygosity (LOH), we generated a high-resolution allelotype of 35 ductal carcinoma in situ cases and completed a deletion map of chromosome 16q by means of paraffin-embedded tissue microdissection and PCR microsatellite analysis of 22 markers. We observed a strikingly high frequency of LOH in 16q, with 31 of 35 tumors (89%) affected. We identified three distinctive areas with high LOH. Two areas were described previously and correspond to 16q21 and 16q24.2-qter. The third and most commonly affected area spanned the region from marker D16S515 to marker D16S504. The most affected locus was at D16S518, in which LOH was observed in 20 of 26 informative cases (77%), and we estimate that it lies in subregion q23.3-q24.1. The region of highest LOH spanned approximately 2-3 Mb, as determined by a yeast artificial chromosome contig reported to cover this region. Such a high frequency of LOH at a preinvasive stage of breast cancer suggests that a candidate tumor suppressor gene or genes at this location may play an important role in breast carcinogenesis.

Autoradiography↗
PubMed1996

Midkine in the progression of rat N-nitroso-N-methylurea-induced mammary tumors.

Recent studies have implicated a role for midkine (MK) in cancer progression. This is based upon its structural homology with pleiotrophin, an angiogenic growth factor, and its ability to enhance fibrinolytic activity of bovine endothelial cells. To investigate whether MK plays a role in breast cancer, we examined MK mRNA expression in N-nitroso-N-methylurea-induced rat mammary tumors at various stages of tumor progression, including hormone independence and distant metastasis. Well-differentiated mammary adenocarcinomas showed levels of MK comparable to those of normal mammary gland. A 10- to 20-fold reduction in MK mRNA levels was observed in mammary tumors that had progressed to hormone independence and metastasis. The data suggest that loss of MK expression correlates with breast tumor progression. Treatment of rat mammary tumor cell lines with retinoic acid increased MK expression, decreased proliferation, and markedly reduced colony-forming efficiency in agar. This raises the possibility that agents that upregulate MK could have potential in prevention and therapy by causing breast cells to terminally differentiate.

Adenocarcinoma↗
PubMed1996

Allelotypic and cytogenetic characterization of chemically induced mouse mammary tumors: high frequency of chromosome 4 loss of heterozygosity at advanced stages of progression.

Loss of heterozygosity (LOH) is one of the most common genetic abnormalities in cancer. To define the role of LOH and chromosomal abnormalities at various stages of mouse mammary cancer progression, we analyzed the allelotypes and karyotypes of primary mammary tumors induced in CD2F, mice by two basic protocols, the classical multiple-dose 7,12-dimethylbenz[a]anthracene (DMBA) protocol and a novel protocol of combined medroxyprogesterone acetate (MPA) and DMBA. The advantage of the latter protocol is that its latency for tumor development is much shorter and its tumor incidence is higher than those of DMBA alone. To study more advanced stages of mammary tumor progression, we also analyzed mouse mammary tumors that had acquired autonomous growth and were transplantable into syngeneic hosts. The allelotypic studies were performed by means of microsatellite length polymorphism analysis with a minimum of two simple-sequence repeat markers per chromosome. We observed that MPA-DMBA-induced mammary adenocarcinomas, which in general arose earlier because of the growth promotion exerted by MPA, did not show any significant LOH and were essentially diploid. Tumors induced by DMBA alone, which on average took longer to develop, showed a higher frequency of allelic losses. LOH on chromosome 11 was observed in 30% of the cases. Chromosomes 4 and 8 were affected in 25% and 20% of the tumors, respectively. Interestingly, advanced stages of mammary tumor progression, represented by transplantable mammary tumors, showed a much higher level of genomic instability, specifically a very high frequency (66%) of LOH on chromosome 4. These findings indicate that chromosome 4 harbors a gene whose inactivation may play a role in the acquisition of more aggressive characteristics such as autonomous growth and transplantation ability.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Technical approach for the study of the genetic evolution of breast cancer from paraffin-embedded tissue sections.

We have optimized a technique that allows the study of numerous chromosomal loci (n = 20-50) from single paraffin-embedded tissue sections by microsatellite length polymorphism analysis. DNA samples from normal and breast cancerous tissue can be obtained from the same section by means of microdissection. This technique was further improved by subjecting DNA to several cycles of amplification with a degenerate (universal) primer and then with specific microsatellite primers. This amplified DNA was also used to screen for mutations in the p53 gene by means of PCR-SSCP. In addition adjacent tissue sections were used to assess specific chromosome copy number by interphase cytogenetic analyses (chromosome in situ hybridization) and to analyze expression of specific genes such as p53 and ERBB2. As an example of the use of our approach we performed a detailed chromosome 17 allelotypic analysis in 22 breast tumors (5 ductal carcinomas in situ, 13 invasive ductal carcinomas, and 4 invasive lobular carcinomas). We detected mutations in the p53 gene by PCR-SSCP in 36% of the samples. Samples with significant levels of p53 protein accumulation detected by immunohistochemistry were also positive for mobility shifts in the SSCP analysis. We observed that chromosome 17 allelic losses and imbalance occurred at as early a stage as ductal carcinoma in situ (DCIS). Although in some cases we observed allelic losses or imbalance affecting the 17p13 region, close to the p53 locus, several of the tumors showed dissociation between such loss or imbalance and p53 mutation. Lobular carcinomas were predominantly disomic for chromosome 17 in contrast with ductal tumors, which often showed polysomy for chromosome 17. This comprehensive approach correlating the tumor subtype, its allelotype, with specific chromosome copy number and specific gene mutations and expression in preinvasive or early invasive breast cancer lesions will potentially provide information of relevance for a better understanding of the multistep mechanisms of breast carcinogenesis.

Alleles↗
PubMed1996

Regression and progression characteristics of papillomas induced by chrysarobin in SENCAR mice.

The present study was designed to test the effects of a free radical generating tumor promoter, chrysarobin (1,8-dihydroxy-3-methyl-9-anthrone), on the growth and progression of papillomas generated in the skin of SENCAR mice. In the first set of experiments, papillomas were generated by initiation with 6.4 microg of 7,12-dimethylbenz[a]anthracene (DMBA) followed by promotion with once-weekly applications of 52.8 microg chrysarobin for 10 weeks. The fate of individual papillomas was then monitored for a 20 week interval following cessation of promoter treatment. Five weeks after the cessation of chrysarobin treatment, the papilloma response reached a maximum of 13.2 papillomas/mouse. By the end of the 20 week interval 19% and 18% of the papillomas had regressed or coalesced respectively. A three-stage treatment protocol was also utilized to test the ability of chrysarobin to enhance the progression of pre-existing papillomas to squamous cell carcinomas (SCCs). In stage I, mice were initiated with 0.5 microg of DMBA. In stage II, mice were promoted with twice-weekly applications of 1 or 2 microg of 12-0-tetradecanoylphorbol-13-acetate (TPA) for 15 weeks. Then, in stage III, mice were treated with acetone, TPA (1 or 2 microg), chrysarobin (52.8 microg) or benzoyl peroxide (BzPo; 20 mg) for the next 45 weeks. The mean number of papillomas per mouse at plateau was very similar for all groups. The carcinoma incidence was also similar for all groups regardless of the treatment protocol used, as was the mean number of carcinomas per mouse. The ratio of papillomas that converted to SCCs in mice treated with chrysarobin during stage III was not significantly different from the acetone controls or any of the other treatment groups (P > 0.05, Kruskal-Wallis analysis). In addition, BzPo did not enhance the progression of papillomas to SCCs under the current experimental conditions. Collectively, the results indicate that papillomas promoted by chrysarobin have growth properties similar to those promoted by TPA under similar experimental conditions. Furthermore, despite its ability to generate free radical intermediates, chrysarobin does not enhance the malignant progression of pre-existing papillomas induced by TPA treatment.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Medroxyprogesterone acetate accelerates the development and increases the incidence of mouse mammary tumors induced by dimethylbenzanthracene.

Chemical induction of mammary tumors in mice requires usually a long latency period and is often complicated by high non-mammary tumor related mortality. Classically hormone stimulation has been used as the means to increase tumor incidence. The synthetic progestin medroxyprogesterone acetate (MPA) was postulated by some authors to increase mammary tumor incidence in various rodent models. However, controversy exists regarding the role of MPA in experimental and human carcinogenesis. In our study we tested the use of a protocol of combined MPA- and dimethylbenz[a]anthracene (DMBA) treatment for the obtention of mammary tumors with a short latency and with a lower toxicity than the classical multiple dose DMBA protocol. MPA was very effective in accelerating the development and increasing the incidence of mammary tumors induced by DMBA in CD2F1 mice. MPA by itself did not produce any mammary tumors. The mean latency for tumor development from the end of carcinogen treatment was 99 +/- 51 days in the group that received a combination of MPA and four DMBA doses. This group showed significantly earlier mammary tumor incidence (P < 0.0001) and higher tumor numbers than the groups that received only DMBA. Mammary tumors were also analyzed for effects on the mutation rate affecting the Ha-ras and Ki-ras genes. Our data is consistent with MPA probably increasing the number of target cells at risk for mutation by the chemical carcinogen DMBA and possibly promoting the faster development of tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Cloning and chromosomal localization of the rat Stat5 and Yy1 genes.

Rat beta-casein gene expression is controlled in part by the positively acting factor Stat5 and the negatively acting factor Yy1. Partial cDNAs encoding the SH2 domain of rat Stat5a and Stat5b and the zinc finger domain of rat Yy1 have been cloned by an RT-PCR based approach. The nucleotide sequences encoding the SH2 domain of rat Stat5a and Stat5b are 75% homologous. The rat Yy1 cDNA is 95% homologous to its human and mouse counterparts in the zinc finger domain-encoding region. Using fluorescence in situ hybridization, we have localized Stat5a to rat chromosome band 10q32.1 and Yy1 to rat chromosome band 6q32.

Amino Acid Sequence↗
PubMed1996

The mouse skin carcinogenesis model.

Skin carcinogenesis can be divided into at least three major stages: initiation, promotion, and progression. In the mouse skin model, the first stage is thought to involve the interaction of a tumor initiator with the genetic material of stem cells, leading to an irreversible alteration in growth control or differentiation, probably by activation of the Ha-ras oncogene. The major effect of all skin-tumor promoters seems to be the specific expansion of the initiated stem cells. The correlation between the abilities of tumor promoters to induce sustained hyperplasia and their tumor-promoting activities is very good. We found that the appearance of alpha-glutamyl transpeptidase (GGT) and keratin 13 and the lack of expression of keratins 1 and 10 are good markers for skin tumor progression. These alterations occur when papillomas change from a diploid to an aneuploid state, mainly as a result of developing trisomies 6 and 7. To evaluate the role of GGT in skin-tumor progression, we transfected a functional GGT cDNA into two cell lines that normally produce papillomas when grafted into the skin of nude mice. When injected subcutaneously, all of the GGT-transfected clones formed malignant tumors, whereas only 24% of vector-transfected cells did. When GGT-transfected clones were placed into grafts, the grafts had an average mass almost three times that of grafts of vector-transfected cells. Our recent studies also suggest that the ribonucleoprotein telomerase and the gap-junctional proteins connexins (Cxs) are also important in skin-tumor progression. A progressive increase in telomerase activity was associated with the increased level of genomic instability during tumor progression. In addition, the level and expression of Cx26, Cx43, and Cx31.1 were significantly altered during skin tumor promotion and progression. The differences of various mouse stocks and strains in susceptibility to multistage skin carcinogenesis seem to be related more to alterations in tumor promotion than to tumor initiation; however, the critical events have not been determined. Results with an inbred strain of SENCAR mice, which are very sensitive to papilloma formation by the two-stage protocol, also suggest that susceptibility is related to promotion. Despite the high incidence of papillomas in these inbred SENCAR mice, the number of malignant tumors was extremely low, suggesting that sensitivity to promotion and progression are independent in these mice.

Animals↗
PubMed1996

Preferential loss of expression of p16(INK4a) rather than p19(ARF) in breast cancer.

The tumor suppressor p16(INK4a) has been shown to be inactivated in numerous cancer lines and primary tumors. Recently, we reported loss of heterozygosity of the region in which p16(INK4a) is located in more than one-half of primary breast tumors. However, mutational analysis of these same tumors revealed mutation of p16(INK4a) to be infrequent. Other possible modes of inactivation, such as de novo methylation and homozygous deletion, have since been shown to occur in numerous neoplasias. Furthering the complexity of this locus, a transcript overlapping the p16(INK4a) coding sequence and encoding a novel peptide with growth-suppressive activity, p19(ARF), has been described. To clearly elucidate the target of aberrations affecting this subchromosomal region and approximate frequency in breast cancer, we performed a comprehensive study including p16 deletion analysis by means of interphase chromosomal fluorescence in situ hybridization, methylation analysis of the first exon encoding p16(INK4a) (exon 1alpha), mutational analysis of exon 1beta by single-strand conformational polymorphism analysis of p19(ARF) transcripts, and expression of both alpha and beta transcripts by reverse transcription PCR. Homozygous deletion of p16, as determined by interphase chromosomal fluorescence in situ hybridization, was observed in 3 of 18 (17%) tumors analyzed, whereas de novo methylation of exon 1alpha was observed in an additional 17% (4 of 23). Reduced expression of p16(INK4a) was observed in 11 tumors (48%), including all those in which homozygous deletion or complete methylation was observed. No mutations of exon 1 beta were detected, and expression of its transcript was variable, with 13% demonstrating decreased expression and 17% demonstrating overexpression. These results further support p16(INK4a) as a target of inactivation in the 9p21 region for breast cancer.

Breast Neoplasms↗
PubMed1995

Increased telomerase activity in mouse skin premalignant progression.

It has been postulated that the expression of the ribonucleoprotein telomerase is necessary to overcome cellular senescence and that malignant tumors must express telomerase to maintain their immortality. In most human adult tissues, telomerase activity is not detected. In contrast, several murine tissues express various levels of telomerase. Mouse skin however, does not show telomerase activity. Using the mouse skin chemical carcinogenesis system, a well-characterized model for studying premalignant and malignant progression, we assayed telomerase activity at various stages of premalignant papilloma progression by means of the recently developed telomeric repeat amplification protocol. We observed that at 10 weeks of promotion, only one mouse skin papilloma of 11 analyzed showed high levels of telomerase activity. The number of papillomas showing higher levels of telomerase activity increased at 20 weeks, and at 30 weeks of promotion, 100% of papillomas expressed significantly higher levels of telomerase. We learned from previous studies that early papillomas are diploid, well-differentiated lesions, whereas late papillomas are aneuploid and very dysplastic. It appears that the progressive increase in telomerase activity is associated with the increased level of genomic instability and the phenotypic progression of these premalignant tumors. It is also possible, however, that the increase in telomerase activity could be in part a consequence of an increase in the proportion of proliferating cells. Nevertheless, the mouse skin system may be a very useful in vivo model for the study and development of anti-telomerase therapeutic strategies.

Animals↗
PubMed1995

Comparative allelotype of in situ and invasive human breast cancer: high frequency of microsatellite instability in lobular breast carcinomas.

To better understand the timing for presentation of allelic losses in human breast carcinogenesis, we compared the allelotypic profile of 23 in situ ductal carcinomas with that of 29 invasive ductal carcinomas. We also compared the allelotype of the invasive ductal breast carcinomas with that of 23 invasive lobular breast carcinomas. These studies were performed by means of microsatellite length polymorphisms from microdissected paraffin sections. We observed that involvement of chromosome arms 1p, 3p, 3q, 6p, 16p, 18p, 18q, 22q, and possibly 6q and 11p appear to be late events in breast cancer progression because allelic losses or imbalances affecting these areas were observed with very low frequency at the in situ stage. On the other hand, allelic imbalances and losses affecting chromosome arms 7p, 16q, 17p, and 17q appear to be early abnormalities because they were observed in approximately 25-30% of ductal carcinoma in situ lesions. Allelic losses and imbalances affecting the 8p arm were frequently observed in invasive lobular breast carcinomas. It was also interesting that microsatellite instability, also known as replication error (RER) phenotype, was found to occur at a high frequency in invasive lobular breast carcinomas because 9 of 23 (39%) were RER+, compared with 7 of 52 (13.5%) RER+ of breast cancers with ductal differentiation (P = 0.012, chi 2 test). Our findings provide for the first time molecular evidence suggesting that invasive lobular breast carcinomas may arise by a different mechanism of carcinogenesis than ductal carcinomas.

Adult↗
PubMed1995

Chromosome 9p allelic loss and p16/CDKN2 in breast cancer and evidence of p16 inactivation in immortal breast epithelial cells.

To define the extent of involvement of chromosome 9p in breast carcinogenesis, we performed microsatellite length polymorphism analysis of markers spanning this region. Of 24 primary breast carcinomas analyzed, we observed a high frequency (58%) of loss of heterozygosity or allelic imbalance affecting subregion 9p21-22. Mutational analysis of CDKN2 (p16) was performed to determine whether this gene was the target of such alterations. Of 21 tumors analyzed, only 1 showed a mutation of probable consequence, suggesting that CDKN2 appears not to be the target of loss of heterozygosity and indicating the possible existence of another tumor suppressor gene within this region. Additionally, since it has been suggested that some CDKN2 deletions and mutations could be due to an in vitro phenomenon, four immortal breast cell lines derived from normal epithelium, MCF10F, MCF12F, 184A1, and 184B5, were examined for loss or mutation of CDKN2. Two lines (MCF10F and MCF12F) showed homozygous deletions of CDKN2, and one (184A1) revealed a hemizygous deletion and a nonsense mutation in the remaining allele. This could imply an important role of CDKN2 in the control of immortalization or in vitro adaptation and is the first evidence of such in nontumor-derived cell lines. Additionally, this is the first report of frequent loss of heterozygosity in the 9p21-22 chromosome subregion of uncultured primary breast tumors.

Alleles↗
PubMed1995

Involvement of the polyamine pathway in breast cancer progression.

These experiments were designed to test the role of the polyamine pathway in breast cancer progression utilizing an experimental system based on the development of ovary-independent rat mammary tumors and their sequential transplantation into syngeneic hosts. Three key enzymes involved in the PA biosynthetic/catabolic pathway (ornithine-decarboxylase (ODC), S-adenosylmethionine decarboxylase (SAMDC), and spermidine/spermine N'-acetyltransferase (SSAT)) were measured in tumors at different stages of progression. The most significant finding was the association between increased ODC activity and the acquisition of a hormone-independent, poorly differentiated phenotype. SSAT levels tended to be higher in hormone-independent tumors and, in this tumor category, they tended to be positively correlated with differentiation. However, significant interaction between hormone dependence and differentiation status on SSAT expression prevented reliable assessment of the possibly complex role of this enzyme in tumor progression. Neither hormone dependence nor differentiation status were correlated with SAMDC levels. We conclude that, among the three enzymes tested, ODC overexpression is the most significant alteration in the PA metabolic pathway associated with breast cancer progression in this experimental system.

Acetyltransferases↗
PubMed1995

Deficiency of p53 accelerates mammary tumorigenesis in Wnt-1 transgenic mice and promotes chromosomal instability.

By crossing mice that carry a null allele of p53 with transgenic mice that develop mammary adenocarcinomas under the influence of a Wnt-1 transgene, we have studied the consequences of p53 deficiency in mammary gland neoplasia. In Wnt-1 transgenic mice homozygous for the p53 null allele, tumors appear at an earlier age than in animals heterozygous or wild-type at the p53 locus. About half of the tumors arising in p53 heterozygotes exhibit loss of the normal p53 allele, implying selection for p53-deficient cells. Mammary tumors lacking p53 display less fibrotic histopathology and increased genomic instability with aneuploidy, amplifications, and deletions, as detected by karyotype analysis and comparative genomic hybridization. In one tumor, the amplified region of chromosome 7 had an ectopically expressed int-2/FGF3 proto-oncogene, a gene known to cooperate with Wnt-1 in the production of mammary tumors. These findings favor a model in which p53 deficiency relaxes normal restraints on chromosomal number and organization during tumorigenesis.

Adenocarcinoma↗
PubMed1995

Loss of heterozygosity at chromosome 1q loci in rat mammary tumors.

To better characterize abnormalities affecting rat chromosome 1 during mammary carcinogenesis, tumors were induced by nitrosomethylurea in F1 hybrid rats polymorphic at multiple chromosome 1 loci. By means of restriction fragment length polymorphism and microsatellite length polymorphism analyses, we observed loss of heterozygosity or allelic imbalance affecting various loci on the q arm of chromosome 1 in a high percentage of the 49 tumors analyzed. Fifty percent of the tumors showed loss or imbalance affecting the most distal (1q55) INS1 (rat insulin 1 gene) locus. The MT1PA (metallothionein-1 pseudogene a) locus was observed to be affected in 58% of tumors induced in BUF/NCr x ACI/Vsp rats. Most of the losses appeared to have occurred by mitotic recombination. No parental bias was observed on the affected chromosome 1. Tumors were also screened for mutations in codon 12 of the Ha-ras-1 gene, which is located on 1q. We observed an association between the presence of mutation and allelic imbalance. These studies confirm our previous cytogenetic observations of a high level of nonrandom instability affecting rat chromosome 1 during mammary carcinogenesis. The observed loss of heterozygosity may indicate the existence of a putative tumor suppressor gene within the distal half of the 1q arm. These abnormalities, however, could also be related to the early stages of Ha-ras amplification.

Adenocarcinoma↗
PubMed1995

Colocalization of the rat homolog of the von Hippel Lindau (Vhl) gene and the plasma membrane Ca++ transporting ATPase isoform 2 (Atp2b2) gene to rat chromosome bands 4q41.3-->42.1.

Using fluorescence in situ hybridization, we localized the rat homolog of the von Hippel-Lindau gene (Vhl) to rat chromosome band 4q41.3-->q42.1. We also mapped the gene encoding the plasma membrane Ca(++)-transporting ATPase isoform 2(Atp2b2) to the same chromosome subregion. These two genes together with Raf1 appear to be members of a large syntenic gene cluster that maps to human chromosome bands 3p25-->p26, mouse chromosome bands 6 C3-->E, and rat chromosome bands 4q41-->q42. Cytogenetic analysis of NRK 52E cells derived from immortalized normal rat kidney epithelial cells revealed an inverted duplication of the region containing this gene cluster.

Animals↗