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Int J Clin Exp Pathol 2(2),154-162;2009

Original Article
Putative Precursor Cancer Cells in the Human Colorectal Cancer Tissue

Teodora E Goranova, Masayuki Ohue and Kikuya Kato

Research Institute and Department of Surgery, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari-ku, Osaka, Japan

Received 11 June 2008; Accepted 1 July 2008; Available online 14 July 2008

Abstract: Multistage carcinogenesis is an important concept in cancer biology. Each new stage is triggered by the acquisition of an additional
genetic aberration, leading to clonal expansion of the cancer cell. The resulting tumor mass consists of cancer cells with all genetic
aberrations, but may include precursor cells at some point of carcinogenesis. We analyzed six colorectal cancer tissues with APC, K-ras, and
p53 mutations. From each sample, 40–50 areas (100×100×40μm) consisting only of cancer cells were microdissected, and genomic DNA was
purified. Ratios of mutated and normal alleles were quantitated by the SNaPshot assay, a primer extension assay. In five tumor tissues, we
identified cancer cell subpopulations corresponding to putative precursors, i.e., cells with mutations in one or two of the three genes. All
samples were likely to be of monoclonal origin, and temporal sequences of the mutations could be deduced from the mutation patterns of
putative precursors. The orders of mutation events were variable. However, the two carcinoma tissues accompanying adenoma regions started
with the APC mutation, not contradicting the previous studies. The analysis also revealed considerable heterogeneity in allele ratios of one or
two of the chromosomes. The current findings are promising to uncover the process of carcinogenesis directly from the tumor tissue of the

Key Words: esophagitis carcinogenesis, somatic mutation, intratumor heterogeneity, chromosome copy number variation, cancer stem cell

Full text PDF,  Supplemental Table S1, Supplemental Table S2, Supplemental Table S3

Address all correspondence to: Kikuya Kato, MD, PhD, Professor and Director, Research Institute, Osaka Medical Center for Cancer and
Cardiovascular Diseases, 1-3-2 Nakamichi, Higashinari-ku, Osaka, 537-8511, Japan. Tel:+81-6-6972-1181 (ext. 4105, 4304); Fax: +81-6-6973-
1209; Email: