Biomedical subjects

C Cordón-Cardó

Publications and source records attributed to C Cordón-Cardó.

15 recordsLinked to original sources

PubMed2001

Inactivation of the apoptosis effector Apaf-1 in malignant melanoma.

Metastatic melanoma is a deadly cancer that fails to respond to conventional chemotherapy and is poorly understood at the molecular level. p53 mutations often occur in aggressive and chemoresistant cancers but are rarely observed in melanoma. Here we show that metastatic melanomas often lose Apaf-1, a cell-death effector that acts with cytochrome c and caspase-9 to mediate p53-dependent apoptosis. Loss of Apaf-1 expression is accompanied by allelic loss in metastatic melanomas, but can be recovered in melanoma cell lines by treatment with the methylation inhibitor 5-aza-2'-deoxycytidine (5aza2dC). Apaf-1-negative melanomas are invariably chemoresistant and are unable to execute a typical apoptotic programme in response to p53 activation. Restoring physiological levels of Apaf-1 through gene transfer or 5aza2dC treatment markedly enhances chemosensitivity and rescues the apoptotic defects associated with Apaf-1 loss. We conclude that Apaf-1 is inactivated in metastatic melanomas, which leads to defects in the execution of apoptotic cell death. Apaf-1 loss may contribute to the low frequency of p53 mutations observed in this highly chemoresistant tumour type.

Antineoplastic Agents↗

PubMed2001

Molecular analysis of the INK4A and INK4B gene loci in human breast cancer cell lines and primary carcinomas.

The INK4A and INK4B loci are located at 9p21 and have been implicated in the tumorigenesis of various human malignancies. The INK4A gene encodes two cell cycle regulators, p16(INK4A) and ARF, while INK4B encodes p15(INK4B). Previously, we have shown that the p16(INK4) tumor suppressor was not mutated or deleted in primary breast carcinomas. However, primary and metastatic breast carcinomas exhibited a relative hypomethylation of p16(INK4A), which is associated with expression, compared to normal breast tissue. The present study was conducted to determine if inactivation of p15(INK4B) and INK4A exon 1beta (ARF) are common events in breast carcinoma. Mutational analysis was performed by PCR-SSCP, and mRNA expression was evaluated by RT-PCR. Methylation-specific PCR was used to determine the methylation status of the p15(INK4B) promoter. Our results demonstrate that the p15(INK4B) gene was altered in 3 (21%) of the 14 breast cell lines; one had a silent mutation and two had homozygous deletion of the gene. None of the cell lines showed methylation of p15(INK4B). Two (14%) cell lines had homozygous deletion of INK4A exon 1beta. All normal and malignant breast tissue samples were wild-type and non-methylated for p15(INK4B) and wild-type for exon 1beta. Our results show that these structurally and functionally related genes are not invariably affected together, and the most frequently observed alteration at the INK4A and INK4B loci in breast carcinoma appears to be p16(INK4A) hypomethylation.

Blotting, Southern↗

PubMed2001

Genetic alterations of the p14ARF -hdm2-p53 regulatory pathway in breast carcinoma.

TP53 is the most commonly mutated tumor suppressor gene in human cancers. The amplification and overexpression of HDM2 plays a role in tumorigenesis via inactivation of p53-dependent cell cycle arrest. p14ARF, an alternate transcript of the INK4A tumor suppressor locus, prevents hdm2-induced transcriptional silencing of p53 by binding hdm2. The role of this p14ARF-hdm2-p53 regulatory pathway in breast carcinoma is unknown. We hypothesized that p14ARF mutations and HDM2 gene amplification may be alternative mechanisms of p53 inactivation in breast cancer. Mutational analysis of TP53 (exons 5-9) and exon 1beta of pl4ARF was performed by PCR-SSCP and putative mutations were confirmed by sequencing. p14ARF mRNA expression was evaluated by RT-PCR and the presence of HDM2 gene amplification by differential PCR. Among the cell lines, 7/14 (50%) harbored TP53 mutations and 2/14 (14%) had a deletion ofp14ARF exon 1beta with no detectable p14ARF mRNA. None demonstrated HDM2 gene amplification. TP53 mutations were identified in 7/36 (19%) breast tumors and HDM2 amplification in 2/30 (7%) tumors. All the tumors contained an intact p14ARF exon 1beta with corresponding expression of the mRNA. Alterations in the various components of this regulatory pathway were identified in nine (64%) cell lines and 25% of the 36 breast cancers with TP53 mutation being the predominant aberration. Although p14ARF mutations and HDM2 gene amplification appear to be uncommon events in breast carcinoma, deregulation of this pathway may occur via alternative mechanisms in breast carcinogenesis.

Breast Neoplasms↗

PubMed1999

Involvement of the Ink4a gene (p16 and p19arf) in murine tumorigenesis.

The INK4A and INK4B genes map to 9p21, with the INK4A gene encoding two products, p16 and p19ARF. Many neoplasms in which INK4A and INK4B genes are altered show deletions involving both genes. Mice carrying a targeted Ink4a deletion develop tumors at an early age. In the present study we examined the genetic alterations affecting the remaining Ink4a allele and the Ink4b gene in tumors arising in heterozygous Ink4a mice. We identified deletion of the remaining Ink4a allele in 7 of 18 (39%) tumors. We also observed deletion of the exon 1beta in 3 cases, one of them presenting this deletion as a unique alteration. In conclusion, the deletion of the remaining Ink4a allele was the alteration most frequently observed, representing the inactivation of two proteins capable of arresting the cell cycle through different pathways that involve the tumor suppressors pRB and p53.

Animals↗

PubMed1998

Genotypic and phenotypic characterization of the histoblood group ABO(H) in primary bladder tumors.

The ABO(H) histoblood group genes have been mapped by linkage analysis to 9q34.1-34.2, an area of common deletions in bladder cancer. Lack of ABO(H) antigen expression in bladder tumors is a frequent and well-documented event. In bladder neoplasms the loss of A and B transferase activity is due to down-regulation of the ABO gene transcripts. Our study was undertaken in order to determine the presence of structural alterations of the ABO(H) gene-encoding locus in primary bladder tumors, to estimate the extent of allelic deletions and to characterize further the pattern of histoblood group antigen expression. Fifty-three primary bladder tumors were analyzed by immuno-histochemistry (IHC) using a panel of well-characterized antibodies and fresh frozen tissue sections. Normal and tumor DNA also were analyzed by PCR coupled with restriction enzyme analysis in order to establish the ABO genotype. Results obtained from these analyses were then compared to allelotyping data at the 9q34.1-4 region by Southern blotting. IHC data showed undetectable levels of antigen expression on neoplastic cells in 59% of informative cases. PCR-based genotypic results revealed allelic losses in 27% of heterozygous cases. Four of the 16 pheno- and/or genotypically altered cases (25%) presented loss of heterozygosity at D9S10 or D9S7 loci. Our data indicate that the lack of ABO antigen expression in certain bladder tumors is due to the allelic loss of the ABO glycosyltransferase-encoding genes and that in some of these tumors the loss involves the surrounding chromosomal region at 9q34.1-4.

ABO Blood-Group System↗

PubMed1998

Mutational study of p16CDKN2/MTS1/INK4A and p57KIP2 genes in hepatocellular carcinoma.

p16 and p15 are representative members of cyclin-dependent kinase inhibitors. Because the selective expression of p57KIP2 in liver, and because p16CDKN2/MTS1/INK4A has been found altered in many primary tumors, we undertook the present study to determine the presence of alterations in these genes in a group of hepatocellular carcinomas (HCC). Seventeen tumor and normal DNA pairs were analyzed by Southern blot, PCR-SSCP and DNA sequencing. Microsatellite markers surrounding the area of the p16 gene was also used. Southern blot analysis did not show allelic losses of the p16 or p57KIP2 genes. In 4 cases, an extra band was observed when hybridizing with the specific p16 cDNA. Overall, 4/17 (24%) cases presented microsatellite alterations at the 9p21-24 region. These results suggest that deletions or point mutations in these genes are not frequent if present at all in HCC, but reveals the existence of microsatellite alterations at the 9p21-24 region in HCC.

Amino Acid Substitution↗

PubMed1996

Cyclin-dependent kinase inhibitor p57KIP2 in soft tissue sarcomas and Wilms'tumors.

Mammalian cyclin-dependent kinase inhibitors fall into two families, the INK4 and the CIP/KIP. The CIP/KIP family comprises three structurally related members, including p21CiP1/WAF1, p27KIP1, and p57KIP2. These proteins are all capable of inhibiting the progression of the cell cycle by binding and inhibiting G(1) cyclin/cyclin-dependent kinase complexes. In humans, p57KIP2 is expressed specifically in skeletal muscle, heart, brain, kidney, and lung. Human KIP2 resides in 11p15.5, a chromosomal region that is a common site for loss of heterozygosity in certain sarcomas, Wilms' tumors, and tumors associated with the Beckwith-Wiedemann syndrome. Because of the function, selective expression, and chromosomal location of p57KIP2, we undertook the present study to search for potential mutations of KIP2 in a cohort of 126 tumors composed of 75 soft tissue sarcomas and 51 Wilms' tumors. The KIP2 gene was characterized by Southern blot, comparative multiplex PCR, PCR -single-strand conformational polymorphism, and DNA sequencing assays in these neoplasms. Deletions of the KIP2 gene or point mutations at the region encoding the cyclin-dependent kinase inhibitory domain were not found in the tumors analyzed. The absence of KIP2 mutations might indicate that these tumors arise due to defects at a closely linked but separate locus. Alternatively, similarly to the mouse homologue, inactivation of KIP2 could occur via genomic imprinting.

Adult↗

PubMed1991