11q23.1 and 11q25-qter YACs suppress tumour growth in vivo.
Frequent allelic deletion at chromosome 11q22-q23.1 has been described in breast cancer and a number of other malignancies, suggesting putative tumour suppressor gene(s) within the approximately 8 Mb deleted region. In addition, we recently described another locus, at the 11q25-qter region, frequently deleted in breast cancer, suggesting additional tumour suppressor gene(s) in this approximately 2 Mb deleted region. An 11q YAC contig was accessed and three YACs, one containing the candidate gene ATM at 11q23.1, and two contiguous YACs (overlapping for approximately 400-600 kb) overlying most of the 11q25 deleted region, were retrofitted with a G418 resistance marker and transfected into murine A9 fibrosarcoma cells. Selected A9 transfectant clones (and control untransfected and 'irrelevant' alphoid YAC transfectant A9 clones) were assayed for in vivo tumorigenicity in athymic female Balb c-nu/nu mice. All the 11q YAC transfectant clones demonstrated significant tumour suppression compared to the control untransfected and 'irrelevant' YAC transfected A9 cells. These results define two discrete tumour suppressor loci on chromosome 11q by functional complementation, one to a approximately 1.2 Mb region on 11q23.1 (containing the ATM locus) and another to a approximately 400-600 kb subterminal region on 11q25-qter. (+info)
Superimposed histologic and genetic mapping of chromosome 9 in progression of human urinary bladder neoplasia: implications for a genetic model of multistep urothelial carcinogenesis and early detection of urinary bladder cancer.
The evolution of alterations on chromosome 9, including the putative tumor suppressor genes mapped to the 9p21-22 region (the MTS genes), was studied in relation to the progression of human urinary bladder neoplasia by using whole organ superimposed histologic and genetic mapping in cystectomy specimens and was verified in urinary bladder tumors of various pathogenetic subsets with longterm follow-up. The applicability of chromosome 9 allelic losses as non-invasive markers of urothelial neoplasia was tested on voided urine and/or bladder washings of patients with urinary bladder cancer. Although sequential multiple hits in the MTS locus were documented in the development of intraurothelial precursor lesions, the MTS genes do not seem to represent a major target for p21-23 deletions in bladder cancer. Two additional tumor suppressor genes involved in bladder neoplasia located distally and proximally to the MTS locus within p22-23 and p11-13 regions respectively were identified. Several distinct putative tumor suppressor gene loci within the q12-13, q21-22, and q34 regions were identified on the q arm. In particular, the pericentromeric q12-13 area may contain the critical tumor suppressor gene or genes for the development of early urothelial neoplasia. Allelic losses of chromosome 9 were associated with expansion of the abnormal urothelial clone which frequently involved large areas of urinary bladder mucosa. These losses could be found in a high proportion of urothelial tumors and in voided urine or bladder washing samples of nearly all patients with urinary bladder carcinoma. (+info)
Multiple target sites of allelic imbalance on chromosome 17 in Barrett's oesophageal cancer.
Twelve Barrett's adenocarcinomas have been analysed for the occurrence of allelic imbalance (LOH) on chromosome 17 using 41 microsatellite markers. This study provides evidence for 13 minimal regions of LOH, six on 17p and seven on 17q. Four of these centre in the vicinity of the known tumour suppressor genes (TSGs) TP53 (17p13.1), NFI (17q11.2), BRCA1 (17q21.1), and a putative TSG (17p13.3). The tumours all displayed relatively small regions of LOH (1-10 cM), and in several tumours extensive regions of LOH were detected. One tumour displayed only two very small regions of LOH; 17p11.2 and 17p13.1. The frequency of allelic imbalance has been calculated based on the LOH encompassing only one minimal region, and based on all the LOH observations. By both evaluations the highest LOH frequencies were found for regions II (p53), III (17p13.1 centromeric to p53), IV (17p12), V (17p11.2) and VII (NF1, 17q11.2). Our data supports the existence of multiple TSGs on chromosome 17 and challenges the view that p53 is the sole target of LOH on 17p in Barrett's adenocarcinoma. (+info)
Correlation between the status of the p53 gene and survival in patients with stage I non-small cell lung carcinoma.
The association of p53 abnormalities with the prognosis of patients with non-small cell lung carcinoma (NSCLC) has been extensively investigated to date, however, this association is still controversial. Therefore, we investigated the prognostic significance of p53 mutations through exons 2 to 11 and p53 protein expression in 103 cases of stage I NSCLC. p53 mutations were detected in 49 of 103 (48%) tumors. Two separate mutations were detected in four tumors giving a total of 53 unique mutations in 49 tumors. Ten (19%) of mutations occurred outside exons 5-8. Positive immunohistochemical staining of p53 protein was detected in 41 of 103 (40%) tumors. The concordance rate between mutations and protein overexpression was only 69%. p53 mutations, but not expression, were significantly associated with a shortened survival of patients (P<0.001). Furthermore, we investigated the correlation between the types of p53 mutations and prognosis. p53 missense mutations rather than null mutations were associated with poor prognosis (P < 0.001 in missense mutations and P=0.243 in null mutations). These results indicated that p53 mutations, in particular missense mutations, rather than p53 expression could be a useful molecular marker for the prognosis of patients with surgically resected stage I NSCLC. (+info)
p73 at chromosome 1p36.3 is lost in advanced stage neuroblastoma but its mutation is infrequent.
p73, a novel p53 family member, is a recently identified candidate neuroblastoma (NBL) suppressor gene mapped at chromosome 1p36.33 and was found to inhibit growth and induce apoptosis in cell lines. To test the hypothesis that p73 is a NBL suppressor gene, we analysed the p73 gene in primary human NBLs. Loss of heterozygosity (LOH) for p73 was observed in 19% (28/151) of informative cases which included 92 mass-screening (MS) tumors. The high frequency of p73 LOH was significantly associated with sporadic NBLs (9% vs 34%, P<0.001), N-myc amplification (10% vs 71%, P<0.001), and advanced stage (14% vs 28%, P<0.05). Both p73alpha and p73beta transcripts were detectable in only 46 of 134 (34%) NBLs at low levels by RT-PCR methods, while they were easily detectable in most breast cancers and colorectal cancers under the same conditions. They found no correlation between p73 LOH and its expression levels (P>0.1). We found two mutations out of 140 NBLs, one somatic and one germline, which result in amino acid substitutions in the C-terminal region of p73 which may affect transactivation functions, though, in the same tumor samples, no mutation of the p53 gene was observed as reported previously. These results suggest that allelic loss of the p73 gene may be a later event in NBL tumorigenesis. However, p73 is infrequently mutated in primary NBLs and may hardly function as a tumor suppressor in a classic Knudson's manner. (+info)
High polymorphism level of genomic sequences flanking insertion sites of human endogenous retroviral long terminal repeats.
The polymorphism at the multitude of loci adjacent to human endogenous retrovirus long terminal repeats (LTRs) was analyzed by a technique for whole genome differential display based on the PCR suppression effect that provides selective amplification and display of genomic sequences flanking interspersed repeated elements. This strategy is simple, target-specific, requires a small amount of DNA and provides reproducible and highly informative data. The average frequency of polymorphism observed in the vicinity of the LTR insertion sites was found to be about 12%. The high incidence of polymorphism within the LTR flanks together with the frequent location of LTRs near genes makes the LTR loci a useful source of polymorphic markers for gene mapping. (+info)
Structure of cag pathogenicity island in Japanese Helicobacter pylori isolates.
BACKGROUND: cag pathogenicity island (PAI) is reported to be a major virulence factor of Helicobacter pylori. AIM: To characterise cagA and the cag PAI in Japanese H pylori strains. METHODS: H pylori isolates from Japanese patients were evaluated for CagA by immunoblot, for cagA transcription by northern blot, and for cagA and 13 other cag PAI genes by Southern blot. cagA negative strains from Western countries were also studied. Induction of interleukin-8 secretion from gastric epithelial cells was also investigated. RESULTS: All Japanese strains retained cagA. Fifty nine of 63 (94%) strains had all the cag PAI genes. In the remaining four, cag PAI was partially deleted, lacking cagA transcripts and not producing CagA protein. Details of the PAI of these strains were checked; three lacked cagB to cagQ (cagI) and continuously cagS to cag13 (cagII), and the remaining one lacked cagB to cag8. Western cagA negative strains completely lacked cag PAI including cagA. Nucleotide sequence analysis in one strain in which the cag PAI was partially deleted showed that the partial deletion contained 25 kb of cag PAI and the cagA promoter. Interleukin-8 induction was lower with the cag PAI partial deletion strains than with the intact ones. All Japanese cag PAI deleted strains were derived from patients with non-ulcer dyspepsia, whereas 41 of 59 (70%) CagA-producing strains were from patients with peptic ulcers or gastric cancer (p<0.05). CONCLUSIONS: Most Japanese H pylori strains had the intact cag PAI. However, some lacked most of the cag PAI in spite of the presence of cagA. Thus the presence of the cagA gene is not an invariable marker of cag PAI related virulence in Japanese strains. (+info)
Screening for mutations of the cationic trypsinogen gene: are they of relevance in chronic alcoholic pancreatitis?
BACKGROUND: In hereditary pancreatitis mutations of exons 2 (N21I) and 3 (R117H) of the cationic trypsinogen gene have been described. AIMS: To investigate whether the same mutations can also be found in patients with chronic alcoholic pancreatitis. METHODS: Leucocyte DNA was prepared from 23 patients with chronic alcoholic pancreatitis, 21 with alcoholic liver cirrhosis, 34 individuals from seven independent families with hereditary pancreatitis, and 15 healthy controls. DNA was also obtained from pancreatic tissue (n=7) and from pancreatic juice (n=5) of patients suffering from chronic alcoholic pancreatitis. R117H was detected by restriction digestion with Afl III. N21I was identified by an allele specific polymerase chain reaction (PCR). RESULTS: R117H was detected in four families with hereditary pancreatitis. The N21I mutation was identified in three families. All mutations were confirmed by sequencing of the corresponding DNAs. In patients with chronic alcoholic pancreatitis neither the exon 2 nor exon 3 mutations were present in blood leucocytes, pancreatic juice, or pancreatic tissue. DNA of the patients with alcoholic liver cirrhosis as well as all controls was of wild type. CONCLUSIONS: The allele specific PCR may be used to screen for the N21I mutation of cationic trypsinogen. Both trypsinogen mutations were found in hereditary pancreatitis but do not seem to be major pathogenic factors in chronic alcoholic pancreatitis. (+info)