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- Brendle, Annika, et al.
(författare)
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Polymorphisms in predicted microRNA-binding sites in integrin genes and breast cancer ITGB4 as prognostic marker.
- 2008
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Ingår i: Carcinogenesis. - : Oxford University Press. - 0143-3334 .- 1460-2180. ; 29:7, s. 1394-1399
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Tidskriftsartikel (refereegranskat)abstract
- Integrins control the cell attachment to the extracellular matrix and play an important role in mediating cell proliferation, migration and survival. A number of important cancer-associated integrin genes can be regulated by microRNAs (miRNAs) that bind to their target sites in the 3' untranslated regions. We examined the effect of single-nucleotide polymorphisms (SNPs) in predicted miRNA target sites of six integrin genes (ITGA3, ITGA6, ITGAv, ITGB3, ITGB4 and ITGB5) on breast cancer (BC) risk and clinical outcome. Six SNPs were genotyped in 749 Swedish incident BC cases with detailed clinical data and up to 15 years of follow-up together with 1493 matched controls. We evaluated associations between genotypes and BC risk and clinical tumour characteristics. Survival probabilities were compared between different subgroups. As a novel finding, several SNPs seemed to associate with the hormone receptor status. The strongest association was observed between the A allele of the SNP rs743554 in the ITGB4 gene and oestrogen receptor-negative tumours [odds ratio 2.09, 95% confidence intervals (CIs) 1.19-3.67]. The same SNP was associated with survival. The A allele carriers had a worse survival compared with the wild-type genotype carriers (hazard ratio 2.11, 95% CIs 1.21-3.68). The poor survival was significantly associated with the aggressive tumour characteristics: high grade, lymph node metastasis and high stage. None of the SNPs was significantly associated with BC risk. As the ITGB4 SNP seems to influence tumour aggressiveness and survival, it may have prognostic value in the clinic.
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| 2. |
- Lei, Haixin
(författare)
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Functional analysis of genetic variants in putative low penetrate breast cancer genes
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Paper I & II: CDH1 germline mutations predispose individuals to diffuse gastric cancer, but its role in breast cancer is less clear. Somatic CDH1 mutations were reported to be frequent in lobular tumours (ILC), but they have not been found in ductal carcinomas (IDC). To define the role of CDH1 in breast cancer, we used denaturing high performance liquid chromatography to screen a series of breast cancer samples for mutations. Somatic mutations were detected in 4 of 83 IDC (5%) and 3 of 25 ILC (12%). No germline mutation was found in 19 familial breast cancer patients that showed loss of heterozygosity (LOH) at 16q24, in 12 cases from 10 families with breast, gastric and colon cancer and in 13 familial lobular breast tumours. Another somatic mutation was detected in one of the familial breast cancer patient with both ductal and lobular foci. Putative breast cancer risk conferred by the promoter polymorphism -161C-A of CDH1 or 1774G-A (Ala592Thr) was also analyzed in case-control studies. No significant difference in allelic frequency was found between the breast cancer patients and controls for either polymorphism. A novel promoter polymorphism was identified at position -152 with a similar frequency of the rare C allele in both breast cancer patients and controls. Transient transfection assay using constructs containing -16IC/-152C or -161A/-152T showed only a slight decrease of the transcription activity as compared to the wild type constructs carrying -161C/152T. We conclude that CDH1 is not a prominent lowpenetrance gene in breast cancer, but CDH1 mutations contribute to the progression of both lobular and ductal tumours. Paper III: BACH1, a gene located in 17q22 and encoding a protein directly interacting with BRCA1, was suggested to be a candidate gene for breast cancer susceptibility. Using PCR-SSCP, we screened for germline BACH] mutations with 29 breast cancer families linked to 17q22 and additional 95 familial breast cancer cases, which were all without detectable BRCA112 mutations. No mutation was found. A C/T polymorphism at position 517 was detected, which leads to Arg173Cys substitution in the putative nuclear localization sequence. This alteration may contribute to the development of breast cancer, but BACH1 is not a major breast cancer gene. Paper IV: ATM has been suggested to act as a tumour suppression gene that requires the inactivation of both alleles in the development of a malignancy. Two mutations designated as T7271G and IVS1O+6 T-G were reported to increase breast cancer risk in multiple-case families in a dominant negative manner. We evaluated the population frequency of these two mutations in Sweden and Czech populations using PCR-RFLP. The mutation T7271G was not detected, mutation IVS 10+6 T-G was found in 2 of 768 cases and I in 557 controls, giving the allelic frequency of 0. 1%. We also tested the hypothesis that ATM mutations would be enriched in breast cancer patients with LOH at 11q22-23 if ATM acted as TSG. Forty-two selected DNA samples from breast cancer cases were screened for mutations in ATM from exons 50 to 66 using PCR-SSCP, but no mutation was detected. Paper V: (manuscript) LST1 is a gene located in the TNFalpha region and producing many isoforms with a possible role in immune response. In an attempt to understand the mechanism of the 3' splicing site selection in LST1, we found that removal of a nearby AG dinucleotide repeat TNFd led to a serine-arginine protein-dependent activation of a cryptic 3' splice site. The highest yield of the novel isoform named LST1/n was induced by ASF and SRp40. This effect was dose-dependent, it was also dependent on the length of TNFd. Deletion of RNA recognition motif 2 (RRM2) of ASF/SF2 abolished the usage of the cryptic splice site, indicating that the activation is mediated by RNA binding. In addition, we showed that hnRNP Al but not hnRNP K could effectively antagonize SR-protein induced activation. Replacement of TNFd with AC or AT repeat indicated a AG-AC>AT repressing hierarchy on the SR protein induced activation. Further removal of a putative splicing silencer A3 alleviated the requirement for exogenous SR proteins in LST/n activation. We also showed that lack of this event in the wild type construct was not due to the differential efficiency in RTPCR for TNFd+ or TNFd-isoform. Insertion of TNFd in a heterologous context showed no evidence of splicing inhibition in in vitro splicing analysis. Insertion of A3 into a middle exon of a heterologousACE Alu + 136/3'ss minigene led to almost full exon skipping, suggesting that A3 contains splicing inhibitory sequences. All these data are consistent with the existence of multiple mechanisms in the repression of pseudo splice sites and with the concept that dinucleotide repeats could act as splicing regulatory elements in the vicinity of splice sites.
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| 3. |
- Lei, Haixin, et al.
(författare)
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PAI-1 -675 4G/5G polymorphism as a prognostic biomarker in breast cancer
- 2008
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Ingår i: Breast Cancer Research and Treatment. - : Springer. - 0167-6806 .- 1573-7217. ; 109:1, s. 165-175
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular matrix degradation, mediated by the urokinase plasminogen activation (uPA) system, is a critical step in tumor invasion and metastasis. High tumor levels of uPA and its inhibitor PAI-1 have been correlated with poor prognosis in breast cancer. We examined whether genetic variation in the genes of the uPA system affect breast cancer susceptibility and prognosis. We genotyped eight potentially functional single nucleotide polymorphisms (SNPs) in six genes of the uPA system in 959 Swedish breast cancer patients with detailed clinical data and up to 15 years of follow-up together with 952 matched controls. We used the unconditional logistic regression models to evaluate the associations between genotypes and breast cancer risk and tumor characteristics. The Kaplan-Meier method was used to estimate the survival probabilities; the log-rank test was used to test differences between subgroups. None of the SNPs conferred an increased breast cancer risk, but correlation with some traditional prognostic factors was observed for several SNPs. Most importantly, we identified the -675 4G/5G SNP in the PAI-1 gene as a promising prognostic biomarker for breast cancer. Compared to the 4G/4G and 4G/5G genotypes 5G/5G homozygosity correlated significantly with worse survival (RR 2.04, 95% CI 1.45-2.86, P<0.001), especially in patients with more aggressive tumors. 5G/5G homozygotes were also the group with worse survival among lymph node negative cases. Our finding suggests that genotyping PAI-1 -675 4G/5G may help in clinical prognosis of breast cancer.
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| 6. |
- Salahshor, Sima, et al.
(författare)
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Low frequency of E-cadherin alterations in familial breast cancer
- 2001
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Ingår i: Breast Cancer Research. - : Springer Science and Business Media LLC. - 1465-5411 .- 1465-542X. ; 3:3, s. 199-207
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Tidskriftsartikel (refereegranskat)abstract
- In order to explore the possible role of E-cadherin in familial cancer, 19 familial breast cancer patients, whose tumours demonstrated loss of heterozygosity (LOH) at the E-cadherin locus, were screened for germline mutations. No pathogenic germline alterations were detected in these individuals. However, a somatic mutation was found (49-2A-->C) in one of the tumours. This tumour showed a pattern of both ductal and lobular histology. Another 10 families with cases of breast, gastric and colon cancer were also screened for germline mutations, and no mutations were found. A missense mutation in exon 12 of E-cadherin (1774G-->A; Ala592Thr) was previously found in one family with diffuse gastric cancer, and colon and breast cancer. An allelic association study was performed to determine whether the Ala592Thr alteration predisposes to breast cancer. In total, we studied 484 familial breast cancer patients, 614 sporadic breast cancer patients and 497 control individuals. The frequencies of this alteration were similar in these groups. However, a correlation between the Ala592Thr alteration and ductal comedo-type tumour was seen. These results, together with previously reported studies, indicate that germline mutations and, more commonly, somatic mutations in E-cadherin may have an influence on the behaviour of the tumours, rather than predispose to breast cancer.
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