Eiichi Ikeda

DNA ploidy analysis by laser scanning cytometry (LSC) in colorectal cancers and comparison with flow cytometry

We evaluated laser scanning cytometry (LSC) by comparing nuclear DNA ploidy determined by LSC and by flow cytometry (FCM) in 77 samples of human colorectal cancer from 48 patients. Both methods revealed an aneuploid peak in 30 (62.5%) of the cases, although two samples that were aneuploid by LSC were diploid by FCM and two others were diploid by LSC and aneuploid by FCM. The concordance rate for nuclear DNA ploidy was 91.7% in the 48 patients and 87.0% for the 77 samples. The DNA index was also highly correlated between two methods (r2 = 0.97, P < 0.001). We concluded that LSC provides DNA histograms equivalent to FCM for surgical specimens and has potential clinical application in pathology.

Monosomy of chromosome 18 detected by fluorescence in situ hybridization in colorectal tumors

Background.At least two different evolutional pathways of colorectal cancer, namely the adenoma‐carcinoma sequence and de novo carcinogenesis, have been indicated. However, whether there is a difference between them in affected chromosomes and genes has not yet been elucidated. Chromosomal examination is expected to provide a clue to an answer to this question. In this study, the relation of aberrations in chromosome 18 to type of colorectal cancer was examined.

Immunohistochemical detection of p21waf1/cip1/sdi1 and p53 proteins in formalin-fixed, paraffin-embedded tissue sections of colorectal carcinoma

Wild-type p53 protein is a critical participant in G1 cell cycle arrest through the induction of waf1/cip1/sdi1 gene product p21, but mutant p53 proteins have lost transcriptional activity. To know whether the view obtained from studies using cultured cells is adaptable to human solid tumors, the authors immunohistochemically stained p21 and p53 in formalin-fixed, paraffin-embedded tissue sections from 67 cases of colorectal carcinoma. Of these, 54 cancers showed positive staining of p53, whereas p21-positive cells were identified in 46 tumors. However, the proportion of cells positive for these proteins varied considerably among cases, and moreover wide variation in p21 immunoreactivity was noted within the same tumor. Although there was an inverse relationship between p21 and p53 staining in tumors, namely, p21-positive cells were p53 negative and vice versa, an intermingling of tumor cells expressing concomitantly both genes was noted in 34 (51%) of 67 tumors. In these tumors, both proteins were usually moderately stained, but tumor cells intensely coexpressing both were found in one sample. This study supports the notion that although p21 expression is regulated by p53 under physiological conditions, it can be regulated by an additional pathway(s) in solid malignant tumors.

Cytogenetic Aberrations Detected by Flow Cytometry and Fluorescence in situ Hybridization in Colorectal Cancers: Two Cytogenetic Pathways in Colorectal Carcinogenesis

We measured DNA content by flow cytometry and determined the number of chromosomes 7, 17 and 18 by fluorescence in situ hybridization using DNA probes in 38 sporadic colorectal adenocarcinomas including 14 early cancers. Based on DNA ploidy and the copy number of chromosome 18, colorectal cancers were divided into two groups. In early cancers (mucosal and submucosal adenocarcinomas), monosomy 18 with DNA hypotriploidy was detected exclusively in 6 sessile tumors without adenoma portions. Seven of the remaining 8 tumors in which adenoma portions coexisted manifested disomy 18 and DNA diploidy or near diploidy. These tumors were considered to occur along the adenoma-carcinoma sequence. In contrast, monosomy 18 was accompanied by DNA diploidy or near diploidy in advanced cancers penetrating the muscularis propria. In advanced cancers, DNA hypertriploidy was linked with disomy 18 and chromosomes 7 and 17 were trisomic or tetrasomic. Observations indicate at least two different cytogenetic pathways in colorectal carcinogenesis. According to these findings, two thirds of advanced cancers were estimated to originate from adenoma, and the others were not.