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- Elander, Nils
(författare)
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Inflammation-associated genes and genetic variations in colorectal cancer
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Colorectal cancer is a major cause of morbidity and mortality around the world, each year affecting about one million individuals worldwide. The disease is characterized by an accumulation of genetic alterations, and a sequence of events leading to the development of an invasive and metastasising tumour. Chronic or dysregulated inflammation may contribute to tumour initiation and progression via the release and activity of various mediators – e.g. cytokines, prostaglandins, inducible nitric oxide synthase (NOS2), matrix metalloproteinases (MMPs), and vascular endothelial growth factors (VEGF). In the present thesis, genes and genetic alterations controlling these events were analysed and discussed within the context of colorectal cancer.Prostaglandins, being generated from arachidonic acid in reactions dependent on cyclooxygenases (COX-1, COX-2), have been implicated in carcinogenesis of many organs. Since the quite recent characterization of the terminal and specific prostaglandin synthases, which act downstream of COX enzymes, the search for molecular targets which selectively suppress individual prostanoids has been intensified. In papers I-II, the role and regulation of inducible prostaglandin E2 (PGE2) synthase - mPGES-1 - were explored within the context of intestinal cancer. mPGES-1 was genetically deleted in the ApcMin/+ mouse - yielding marked suppression of PGE2 generation in intestinal and tumour tissue. However, a shift towards enhanced generation of non-PGE2 prostanoids was observed in mPGES-1 knock out mice, and these mice developed more and larger instestinal tumours. These results therefore indicate that targeting mPGES-1 may paradoxically promote tumourigenesis, most likely by secondary effects on other potentially pro-tumoural mediators. We also explored the relation of the commonly mutated APC gene and mPGES-1 in colon tumour cells, and found that high expression of mPGES-1 was associated with the presence of wild type APC. Rather than by regulating putative β-catenin/Tcf binding sites of the mPGES-1 promoter, APC seems to influence the stabilisation of mPGES-1 mRNA.In papers III-V, the possible contribution of variations in regulatory regions of genes encoding NOS2, MMPs, and VEGF, was assessed in populations of colorectal cancer patients and healthy control individuals. A single nucleotide insertion (1G/2G) at -1607 upstream the transcription start site of the MMP-1 gene was identified to be a susceptibility factor for colorectal cancer development, although no relation with disease characteristics was observed. Except for a rather uncommon combination of two individual polymorphisms of the VEGF gene, investigated genetic variations of VEGF, other MMPs, and NOS2, were not associated with colorectal cancer susceptibility or clinicopathological characteristics. We therefore suggest that other molecular events play more significant roles for the dysregulation of these genes in colorectal tumours.In summary, accumulating evidence, including the results here presented, suggest significant albeit complex roles of inflammation-induced genes and mediators in colorectal tumourigenesis. The present results may aid in identifying or excluding potential biomarkers and drug targets within cancer-related inflammation.
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- Fransén, Karin, et al.
(författare)
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Promotion of intestinal polyposis in nitric oxide synthase 2 (NOS2) deficient Min mice and expression of genes in the Notch-1 pathway
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Nitric oxide synthase 2 (NOS2) expression has been found in several different tumor types, including colorectal cancers, but the role of NOS2 expression for cancer development is not fully understood. In the present study, we have investigated the role of NOS2 for intestinal polyp development in the APC Min/+ mouse and studied the mRNA expression by real time PCR of Notch-1 and p21 in normal murine small intestinal tissue and polyps from APC Min/+ NOS2+/+ and APC Min/+ NOS2-/- mice. A significant higher polyp frequency was found in mice with APC Min/+ NOS2-/- genotype compared to APC Min/+ NOS2+/+ mice. The expression of Notch-1 was significantly increased in polyps from the APC Min/+ NOS2+/+ mice compared to wild type small intestinal mucosa, but no difference was evident between the APC Min/+ NOS2+/+ and APC Min/+ NOS2-/- mice, which indicates that NOS2 expression does not affect the Notch-1 expression. No significant difference was found between the different mouse groups regarding the expression of p21. Collectively, NOS2 expression is a protective factor in intestinal polyposis, but its role in polyp development is still unclear.
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- Jerhammar, Fredrik, et al.
(författare)
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YAP1 Gene Amplification is a Marker for Cetuximab Resistance in Head and Neck Cancer
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The epidermal growth factor receptor (EGFR) is commonly overexpressed in head and neck squamous cell carcinomas (HNSCC). The monoclonal antibody cetuximab (Erbitux®) inhibits its signaling and has been approved for treatment of HNSCC. However, since many patients do not benefit from cetuximab treatment, predictive biomarkers of cetuximab response are required. The present study aims at finding novel markers of cetuximab resistance. The intrinsic cetuximab sensitivity of 35 HNSCC cell lines was determined, and revealed a great variation in the response between cell lines. Five cell lines (14%) were cetuximab sensitive, and 12 (34%) were resistant. Interestingly, two cell lines proliferated after cetuximab treatment. 10 cell lines (five cetuximab sensitive and five cetuximab resistant) were selected for gene copy number array analysis on the Affymetrix SNP 6.0 platform. 39 protein coding genes were amplified in cetuximab resistant cells and normal in sensitive cells, all present on genomic regions 11q22.1 or 5p13-15. Five genes were selected for quantitative PCR verification, namely, YAP1 and TRPC6 (11q22.1) and PDCD6, TPPP, and PTGER4 (5p13-15). An extended panel of totally 10 cetuximab resistant and 10 sensitive cell lines verified that YAP1 amplified cells are cetuximab resistant. YAP1 gene amplification was highly correlated to the YAP1 mRNA expression, which was significantly higher in cetuximab resistant cells than in sensitive. YAP1 downregulation resulted in increased cetuximab sensitivity in one of two cetuximab resistant cell lines investigated and growth inhibition in another. We conclude that YAP1 is a marker for cetuximab resistance in head and neck cancer.
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- Ungerbäck, Jonas, et al.
(författare)
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Genetic variation in NFκB signaling pathway genes in colorectal cancer susceptibility and survival
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- PURPOSE: Variations in genes orchestrating inflammatory responses, such as those being connected with NFκB and NLRP3 inflammasome signaling, are associated with chronic inflammatory bowel diseases, which are well-known risk factors for colorectal cancer (CRC). The purpose of this study was to investigate the association between genetic variation and alterations in genes involved in NFκB and NLRP3 inflammasome signaling and their possible influence on susceptibility and clinical outcome of colorectal cancer. EXPERIMENTAL DESIGN: 344 CRC cases and 793 randomly selected healthy individuals from southeastern Sweden were examined with regard to seven polymorphisms in NFκB, TNFAIP3, NLRP3, CARD8 and TLR4 genes. Chi-square tests and multiple logistic regression analysis were used to test for associations between the SNPs and CRC susceptibility, while log-rank tests and Cox proportional hazard regression analysis were used to examine the association between the SNPs and CRC-specific survival. Gene expression assay and loss of heterozygosity analyzes of TNFAIP3 were carried out in a subset of tumors to assess its role as a potential tumor suppressor in CRC. RESULTS: Adjusted for age, gender and polypoid/ulcerative CRC phenotype, a panel of heterozygous and mutant TNFAIP3 (rs6920220), mutant NFκB -94 ATTG ins/del and heterozygous NLRP3 (Q705K) genotypes were found to be associated with poorer survival in patients diagnosed with invasive CRC (aHR = 5.2 95% CI 2.5-10.9, P < 0.001). TNFAIP3 mRNA levels were significantly decreased in tumors compared to adjacent non-neoplastic mucosa (P < 0.0001) and LOH of 6q23.3, (TNFAIP3), was detected in 17% of cases, while only 2.5% of the investigated specimens displayed TNFAIP3 gene mutations. CONCLUSIONS: A panel of the TNFAIP3 (rs6920220), NFκB -94 ATTG ins/del and NLRP3 (Q705K) polymorphisms are associated with poor survival in patients with advanced CRC and may be used as a prognostic marker. Experimental results indicate that TNFAIP3 may act as a tumor suppressor in CRC.
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