Cytogenetic aberrations and heterogeneity of mutations in repeat-containing genes in a colon carcinoma from a patient with hereditary nonpolyposis colorectal cancer.
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.
Planck
Maria
M
Department of Oncology, University Hospital, 221 85 Lund, Sweden. maria.planck@onk.lu.se
Halvarsson
Britta
B
Pålsson
Eva
E
Hallén
Magnus
M
Ekelund
Mats
M
Pålsson
Birger
B
Baldetorp
Bo
B
Nilbert
Mef
M
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D002869:Chromosome Aberrations; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics* / Q000473:pathology; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D005260:Female; D005434:Flow Cytometry; D018740:Genetic Heterogeneity; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics; D009687:Nuclear Proteins; D011003:Ploidies; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1