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- Planck, Maria, et al.
(författare)
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Cytogenetic aberrations and heterogeneity of mutations in repeat-containing genes in a colon carcinoma from a patient with hereditary nonpolyposis colorectal cancer.
- 2002
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Ingår i: Cancer Genetics and Cytogenetics. - 0165-4608. ; 134:1, s. 46-54
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Tidskriftsartikel (refereegranskat)abstract
- The majority of tumors from patients affected by hereditary nonpolyposis colorectal cancer (HNPCC) exhibit a mutator phenotype characterized by widespread microsatellite instability (MSI) and somatic mutations in repeated sequences in several cancer-associated genes. An inverse relationship between MSI and chromosomal instability (CIN) has been demonstrated and HNPCC-associated tumors are generally characterized by diploid or near-diploid cells with few or no chromosomal rearrangements. We have studied MSI, somatic mutations in repeat-containing genes, DNA-ploidy, and cytogenetic aberrations in a colon carcinoma from a patient with a germline MLH1 mutation. Mutations in coding repeats were assessed in 10 macroscopically separate areas of the primary tumor and in two lymph nodes. Some of the genes studied (E2F4, MSH3, MSH6, TCF4, and TGFBRII) showed a consistent lack of mutations, whereas others (BAX, Caspase-5 and IGFIIR) displayed alterations in some tumor regions but not in others. The tumor had DNA-index 1.1-1.2 and a stable, aberrant karyotype with extra copies of chromosomes 7 and 12 and the structural aberrations i(1q), der(20)t(8;20), and der(22)t(1;22). The finding of CIN, MSI, and somatic mutations in coding repeats in this tumor suggests that these phenomena may act together in HNPCC tumorigenesis. Furthermore, the observed intratumoral heterogeneity of mutations in coding repeats implies these changes occur late in tumorigenesis and, thus, probably play a role in tumor progression rather than initiation.
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- Planck, Maria
(författare)
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Hereditary Nonpolyposis Colorectal Cancer - Molecular Genetics and Biology of Associated Tumors
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on one of the most common types of hereditary cancer, hereditary nonpolyposis colorectal cancer (HNPCC). This syndrome is characterized by an autosomal dominant inheritance, an increased risk for several types of cancer (especially cancer of the colorectum, small bowel, endometrium, ovary and urinary tract), early age at diagnosis, and frequent development of multiple primary malignancies. HNPCC is caused by a germline mutation in one of several DNA mismatch-repair (MMR) genes. In paper I, we screened 16 families with suspected HNPCC for germline MMR gene mutations and found a diverse spectrum of mutations, involving the MMR genes MLH1, MSH2 and MSH6. A defective MMR is associated with microsatellite instability (MSI) in the tumor tissue and with somatic mutations in repeated sequences in several cancer-associated genes. In paper II, we studied the occurrence of such alterations in 24 tumors from 14 individuals in an HNPCC family with a germline MSH2 mutation and found an extensive intra- and inter-individual variation. Paper III demonstrates intratumoral heterogeneity of repeat-mutations in 10 macroscopically different areas of a colon carcinoma in a patient with a germline MLH1 mutation. The variation in the somatic mutations in repeat-containing genes suggests that these alterations are important for tumor progression rather than initiation and that the accumulation of mutations, rather than the specific alterations, drives HNPCC tumorigenesis. MMR defects play a role also in the development of sporadic (non-hereditary) cancer and are found in about 15% of colon cancers. In paper IV, we investigated rectal cancer patients regarding a family history of cancer and MSI in the tumor tissue. Only 3/165 (2%) of the tumors had MSI and all 3 patients were found to carry germline HNPCC-causing mutations. We conclude that MSI is rare in rectal cancer, but, when present, strongly indicates HNPCC. In paper V, we studied MSI and immunohistochemical expression of the MMR proteins in small bowel adenocarcinomas and found MSI in 11/70 (16%) tumors, 7 of which showed loss of MMR expression. Defective MMR thus contributes to small bowel carcinogenesis in a fraction of the tumors similar to colon cancer. In paper VI, we studied a population-based series of women who developed the two most common cancer types in HNPCC, colorectal cancer and endometrial cancer, before age 50. MSI was demonstrated in 75% of the tumors and concordant loss of the same MMR protein in both tumors, suggesting an underlying MMR gene mutation, was found in 12/27 patients. In summary, this thesis presents novel HNPCC-causing mutations, demonstrates variability among somatic mutations in repeat-containing genes in HNPCC-tumors, delineates the contribution of defective MMR in rectal cancer and small bowel cancer and points to a high risk of HNPCC among women with colorectal and endometrial cancer at young age.
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- Planck, Maria, et al.
(författare)
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High frequency of microsatellite instability and loss of mismatch-repair protein expression in patients with double primary tumors of the endometrium and colorectum
- 2002
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Ingår i: Cancer. - : Wiley. - 1097-0142 .- 0008-543X. ; 94:9, s. 2502-2510
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND. Patients with the familial syndrome hereditary nonpolyposis colorectal carcinoma (HNPCC) exhibit air increased risk for several tumor types, of which the greatest lifetime risk is for colorectal and endometrial carcinoma. HNPCC is caused by a germline mutation in one of several identified mismatch repair (MMR) genes and typically presents with microsatellite instability (MSI) and frequent loss of NMR protein expression in the tumor tissue. The objective of this study was to estimate the proportion of double primary tumors of the endometrium and colorectum that displays tumor characteristics suggestive of MMR deficiency. METHODS. The authors used the southern Sweden regional population-based Cancer Registry to identify women who developed double primary tumors of tire endometrium and colorectum. Of the 256 women who were diagnosed with carcinoma at both of these sites during the period 1958-1998, 39 women had developed their first tumor before age 50 years. The authors successfully retrieved 67 tumors from 36 of these patients and analyzed them for MSI and immunohistochemical expression of the MMR genes, MLH1, MSH2, and MSH6. RESULTS. The MSI status of the 67 tumors was high MSI in 37 tumors, low MSI in 13 tumors, and microsatellite stable (MSS) in 17 tumors. Immunohistochemical loss of MMR protein expression was correlated with MSI status and was demonstrated in 29 high MSI turners, in 1 low MSI tumor, and in 1 MSS tumor. A concordant loss of the same MMR protein in both tumors was found in 12 of 27 patients. CONCLUSIONS. The authors demonstrated a high frequency of MSI (75%) in tumors from women with endometrial and colorectal carcinoma who had their first tumor diagnosed before age 50 years and observed concordant immunohistochemical loss of MMR protein expression, suggestive of a possible underlying germline mutation, in 12 of 27 patients (44%). They concluded that double primary malignancies of the colorectum and endometrium at a young age should make the clinician suspect (C) 2002 American Cancer Society.
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