Analysis of chromosomal instability in human colorectal adenomas with two mutational hits at APC.

@article{citeulike:3040241, abstract = {In vitro data show that the adenomatous polyposis coli (APC) protein associates with the mitotic spindle and that mouse embryonic stem cells with biallelic Apc mutations are karyotypically unstable. These findings led to suggestions that APC acts in chromosomal segregation and that APC inactivation leads to chromosomal instability (CIN). An alternative hypothesis based on allelic loss studies in colorectal adenomas proposes that CIN precedes and contributes to genetic changes at APC. We determined whether colorectal adenomas with two mutations at APC show features consistent with these models by studying 55 lesions (average size 5 mm; range 1-13 mm) from patients with familial adenomatous polyposis. A variety of methods was used depending on available material, including flow cytometry, comparative genomic hybridization, and loss of heterozygosity (LOH) analysis. Selected adenomas were assessed for proliferative activity by Ki-67 immunocytochemistry. Seventeen of 20 (85\%) tumors were diploid, two were near-diploid, and one was hypotetraploid. Just one (near-diploid) tumor showed increased proliferative activity. LOH was found occasionally on chromosome 15q (2 of 49 tumors), but not on chromosome 18q (0 of 48). In 20 adenomas, LOH at APC was associated with loss at 5q but not 5p markers, with the former encompassing a minimum of 20 Mb. However, three of these lesions analyzed by comparative genomic hybridization displayed normal profiles, suggesting, together with other data, that the mechanism of LOH at APC is probably somatic recombination. Our results therefore do not support the hypothesis that CIN precedes APC mutations in tumorigenesis. Regarding the model in which APC mutations lead directly to CIN, if APC mutations do have this effect in vivo, it must be subtle. Alternatively, CIN associated with APC mutations might be essentially an in vitro phenomenon.}, address = {Molecular and Population Genetics Laboratory, FACS Laboratory, Cancer Research UK.}, author = {Sieber, O. M. and Heinimann, K. and Gorman, P. and Lamlum, H. and Crabtree, M. and Simpson, C. A. and Davies, D. and Neale, K. and Hodgson, S. V. and Roylance, R. R. and Phillips, R. K. and Bodmer, W. F. and Tomlinson, I. P. }, citeulike-article-id = {3040241}, doi = {http://dx.doi.org/10.1073/pnas.012679099}, issn = {0027-8424}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, keywords = {summer}, month = {December}, number = {26}, pages = {16910--16915}, posted-at = {2008-07-24 16:35:24}, priority = {2}, title = {Analysis of chromosomal instability in human colorectal adenomas with two mutational hits at APC.}, url = {http://dx.doi.org/10.1073/pnas.012679099}, volume = {99}, year = {2002} }

TY - JOUR ID - citeulike:3040241 L3 - citeulike-article-id:3040241 TI - Analysis of chromosomal instability in human colorectal adenomas with two mutational hits at APC. JF - Proceedings of the National Academy of Sciences of the United States of America VL - 99 IS - 26 SP - 16910 EP - 16915 AD - Molecular and Population Genetics Laboratory, FACS Laboratory, Cancer Research UK. SN - 0027-8424 N2 - In vitro data show that the adenomatous polyposis coli (APC) protein associates with the mitotic spindle and that mouse embryonic stem cells with biallelic Apc mutations are karyotypically unstable. These findings led to suggestions that APC acts in chromosomal segregation and that APC inactivation leads to chromosomal instability (CIN). An alternative hypothesis based on allelic loss studies in colorectal adenomas proposes that CIN precedes and contributes to genetic changes at APC. We determined whether colorectal adenomas with two mutations at APC show features consistent with these models by studying 55 lesions (average size 5 mm; range 1-13 mm) from patients with familial adenomatous polyposis. A variety of methods was used depending on available material, including flow cytometry, comparative genomic hybridization, and loss of heterozygosity (LOH) analysis. Selected adenomas were assessed for proliferative activity by Ki-67 immunocytochemistry. Seventeen of 20 (85%) tumors were diploid, two were near-diploid, and one was hypotetraploid. Just one (near-diploid) tumor showed increased proliferative activity. LOH was found occasionally on chromosome 15q (2 of 49 tumors), but not on chromosome 18q (0 of 48). In 20 adenomas, LOH at APC was associated with loss at 5q but not 5p markers, with the former encompassing a minimum of 20 Mb. However, three of these lesions analyzed by comparative genomic hybridization displayed normal profiles, suggesting, together with other data, that the mechanism of LOH at APC is probably somatic recombination. Our results therefore do not support the hypothesis that CIN precedes APC mutations in tumorigenesis. Regarding the model in which APC mutations lead directly to CIN, if APC mutations do have this effect in vivo, it must be subtle. Alternatively, CIN associated with APC mutations might be essentially an in vitro phenomenon. KW - summer AU - Sieber, OM AU - Heinimann, K AU - Gorman, P AU - Lamlum, H AU - Crabtree, M AU - Simpson, CA AU - Davies, D AU - Neale, K AU - Hodgson, SV AU - Roylance, RR AU - Phillips, RK AU - Bodmer, WF AU - Tomlinson, IP PY - 2002/12/24/ UR - http://dx.doi.org/10.1073/pnas.012679099 ER -