Search

Germline mutations of the MYH gene have been revealed to associate with the recessive inheritance of multiple colorectal adenomas in Caucasian population. However, MYH mutations in Japanese patients have not yet been clarified. In an assessment of MYH mutations, we examined 35 Japanese patients with multiple colorectal adenomas who had neither dominant inheritance of colorectal tumors, nor germline APC mutations. One patient had a homozygous biallelic MYH mutation, R231C and three independent patients had monoallelic MYH mutations at a splice-site on exon 11 (IVS10-2 A to G). These four patients had 21 to around 100 colorectal adenomas and 1-3 synchronous colorectal carcinomas. The most common mutations in Caucasian patients, Y165C and G382D, were not detected in our Japanese cases. The MYH mutations detected in Japanese patients were novel and different from those detected among Caucasian, Indian and Pakistani patients, which suggests the existence of ethnic differentiation in MYH mutations.

The clinical situation of familial adenomatous polyposis (FAP) in Japan has changed in the period since the last analysis of data of the Japanese Polyposis Center. To reevaluate our data and elucidate the changes we analyzed the records of the 1390 FAP patients in 900 families registered with the Polyposis Committee of the Japanese Society for Cancer of the Colon and Rectum. In the 13-year period 1990-2003, clinical differences between men and women with FAP diminished. The postoperative prognosis was substantially better in patients without advanced colorectal cancer (stage > or = T2) than in those with early cancer or no cancer. Mean age at death improved from 42.5 years in the period before 1990 to 46.0 years, and it was a result of a decreased proportion of deaths from colorectal cancer. The distribution of colorectal cancer in FAP patients was similar to that in the general population. Desmoid tumors accounted for about 10% of deaths in the recent 13 years (1990-2003). The cumulative risk of rectal cancer in the preserved rectum was 12% at 10 years and 23% at 15 years. The registry system in Japan revealed a new clinical situation in FAP patients, and the findings of this study will be useful to improve the prognosis of patients with FAP.

We have previously detected an increased frequency of loss of heterozygosity (LOH) on chromosome 18q during progression of colorectal carcinomas. To clarify the target of 18qLOH, mutation of Smad4 and Smad2 genes was analysed in 176 colorectal tumors with different stages, including liver metastasis, from 111 sporadic, 52 familial adenomatous polyposis (FAP) and nine hereditary nonpolyposis colorectal cancer (HNPCC) patients. Mutation of other Smad gene families in the TGF-beta signaling pathway was also examined. Twenty-one Smad4 mutations and one Smad2 mutation were detected, whereas mutation of Smad3, 6 and 7 genes was not detected. Smad4 mutations included seven frameshift, one inframe deletion, four nonsense and nine missense mutations, 95% of which resulted in alteration of Smad4 protein regions included in homo-oligomer and hetero-oligomer formation. Frequencies of tumors with Smad4 mutation were 0/40 (0%) in adenoma, 4/39 (10%) in intramucosal carcinoma, 3/44 (7%) in primary invasive carcinoma without distant metastasis, 6/17 (35%) in primary invasive carcinoma with distant metastasis, and 11/36 (31%) in distant metastasis (metastatic/non-metastatic: P=0.006 approximately 0.01). Loss of the other allele was observed in 19 of 20 (95%) invasive and metastasized carcinomas with Smad4 mutations. In four cases both primary and metastasized carcinomas in the same patients showed the same mutations. The present results suggest that Smad4 gene is one of true targets of 18qLOH, and that its inactivation is involved in advanced stages, such as distant metastasis, in human colorectal carcinogenesis.

In the forty-seven medical centers in the Kinki district, a comparative trial was conducted to investigate the enhancement of the efficacy of HCEU due to dipyridamol (DP), which is a biochemical modulator in patients with colorectal cancer who have had a curative resection. The trial consisted of two comparative groups: one group (Group A) received HCFU only for five days before operation and for two years from the second week, and the other group (Group B) was given HCFU + DP for the same trial period as Group A. The total number of patients collected was 653 (Group A: 327 patients; Group B: 326 patients) during the two-year trial period from October, 1991. Thymidylate Synthetase (TS) activity in the primary lesions, which is an index of proximity effect, was measured, and the TS inhibition rate (TSIR) was calculated from the activities. The results showed that the TSIR in the primary lesions for the HCFU + DP group (Group B: 0.33) was significantly higher than that of the HCFU group (Group A: 0.27) (p = 0.0006). There was no increase in the side effects of HCFU due to combined administration with DP. From the above results, the therapy with HCFU + DP is expected to be useful for patients with colorectal cancer who have undergone curative resection.

Though colorectal tumorigenesis has long been thought to be a multistep mechanisms, recently has it become possible to identify the molecular events that underlie the initiation and progression of colorectal carcinoma. Though the analysis of mutations in colorectal tumors at various stages of their development allows definition of a model for colorectal tumorigenesis, because the progression is the result of a series of genetic changes that accumulate activation of oncogene (K-ras), inactivation of tumor-suppressor gene (two-hit mutation of APC, Pla2s, p53, suppressor gene on chromosome 8p22 locus, NF2 and DCC) and mismatch repair gene (hMSH2, hMLH1 hPMS family and TGF beta II receptor linked DNA repair). These accumulation of genetic alterations contribute to tumor development and/or progression in primary colorectal carcinoma.

The transitional mucosa adjacent to colorectal carcinoma shows characteristic morphological and histochemical abnormalities that may be indicative of premalignant changes. Sixteen colorectal carcinomas were studied to analyse the proliferative activity and its distribution pattern in tissue samples from transitional mucosa located within 2 cm of the cancer and from uninvolved mucosa 10 cm from the cancer. Proliferative activity was assessed using a monoclonal antibody to proliferating cell nuclear antigen (PCNA). The total labelling index (percentage of labelled cells in a column) of transitional mucosa was not significantly different from that of uninvolved mucosa and normal control mucosa but it was significantly higher in cancer tissue (P < 0.001). An upward shift of the compartment of proliferating epithelial cells towards the bowel lumen was seen in transitional mucosa. The labelling index of the middle compartment (compartment 3) of the crypt in transitional mucosa was significantly higher than that in uninvolved mucosa and control mucosa (P < 0.001). Unstable cytokinetic change may already have started in apparently normal transitional mucosa. Assessment of cell proliferation kinetics by PCNA immunostaining may be useful in screening for heightened risk of the development of colorectal cancer.

Muir-Torre syndrome (MTS) is an autosomal dominant genodermatosis that is characterized by the presence of at least one sebaceous gland tumor with or without keratoacanthoma, and a minimum of one internal malignancy. The most commonly associated neoplasms were colorectal (51%) and genitourinary (25%). MTS shares a number of clinical and pathological presentations with hereditary nonpolyposis colorectal carcinoma (HNPCC), including: tendency to develop right-sided colon cancers; predisposition for the development of extracolonic tumors; and prolonged survival after surgical treatment. These family members should be monitored to detect cancers preliminaly and enrolled in life-long surveillance.

A joint multicenter comparative study of carmofur (HCFU) alone or HCFU+dipyridamole (DP) concurrent administration was conducted by the Kinki Colorectal Cancer Chemotherapy Society. In this study, the drugs were administered five days prior to surgery, and thymidylate synthetase (TS) inhibition rate at the primary lesion of colorectal cancer was determined. In addition, the effect of time after resection of the primary lesion before specimen cooling on the TS inhibition rate was investigated. The subjects were 87 registered patients who received colorectal cancer surgery during 4 months from October 1991 to January 1992. The time before postsurgical cooling was divided into four group; within 10 min (n = 67), 11-20 min (n = 8), 21-30 min (n = 7), and 31 min or longer (n = 5). The TS inhibition rates (mean +/- SD) were 0.45 +/- 0.22, 0.38 +/- 0.19, 0.30 +/- 0.21, and 0.04 +/- 0.05 respectively. The longer the time after resection of the primary lesion before specimen cooling, the more TS inhibition rate decreased. When the time before specimen cooling exceeds 30 min, the major part of TS combined with FdUMP exists in a free state. Therefore, it was considered not suitable as the material for the measurement.

To examine early genetic events during colorectal carcinogenesis, we searched for genetic alterations in 75 adenomas from seven patients with familial polyposis coli (FAP) and in 64 sporadic colorectal tumors (63 carcinomas and one adenoma). We investigated germ-line and somatic mutations in the APC gene, somatic mutations in the K-ras and p53 genes, and loss of heterozygosity (LOH) on chromosome 8p21-22. Thirty-two FAP adenomas carried detectable somatic mutations in the APC gene. The frequency of somatic APC mutations among adenomas was the same regardless of differences in size or histopathological classification. On the other hand, K-ras mutation was very rare in small adenomas where dysplasia was mild or moderate but frequent in large adenomas with severe dysplasia. Mutation of the p53 gene was observed in only two adenomas and LOH on 8p22 was detected in none. These results imply that a second 'hit' in the APC gene, but not necessarily mutation in K-ras or p53, is an important and critical event for formation of a colorectal adenoma.

To determine whether protein tyrosine kinase (PTK) could be utilized as a biological indicator of colonic tumorigenesis, we examined the PTK activity in the cytosolic and particulate fractions of homogenates from 25 adenomas (polyps) and from adjacent normal mucosa. The particulate fraction PTK activity in the colorectal adenomas was significantly higher than in the normal mucosa. The adenomas were then analyzed according to size, histological type (tubular and tubulovillous), and degree of dysplasia (mild, moderate and severe). The average particulate fraction PTK activity ratio (adenoma/normal mucosa) of tubulovillous adenomas or adenomas with moderate to severe dysplasia was significantly elevated in comparison with that of tubular adenomas or adenomas with mild dysplasia. The particulate PTK activity ratio increased significantly with increasing adenoma size, while the cytosolic ratio did not. The cytosolic PTK activity ratio in tubulovillous adenomas or adenomas with severe dysplasia decreased significantly with increasing size. These findings suggest that colonic carcinogenesis might be associated with alterations in the cellular level of PTK activity and that the PTK activity ratio (adenoma/normal mucosa) in the particulate and/or cytosolic fractions may possibly correlate with the risk of malignant transformation.

We examined protein kinase C (PKC) activity in the cytosolic and particulate fractions of homogenates obtained from 25 colorectal adenomas and adjacent normal mucosa in patients with colorectal carcinoma. The total PKC activity of colorectal adenomas was significantly reduced compared with that of normal mucosa in all cases (122 +/- 45.8 vs 174 +/- 50.5 pmol min-1 mg-1) (means +/- s.d.) (P less than 0.001). The particulate fraction PKC activity of adenomas was also significantly lower than in normal mucosa (71.4 +/- 31.3 vs 115 +/- 39.6 pmol min-1 mg-1) (P less than 0.001). Adenomas were classified by size, histological type and degree of dysplasia. The average particulate PKC activity ratio (adenoma/normal mucosa) of tubulovillous adenomas or those with severe dysplasia was significantly reduced compared with that of tubular adenomas or tumours with mild and moderate dysplasia (both P less than 0.001), while there were no significant differences in the cytosolic PKC activity ratio. The particulate PKC activity ratio decreased significantly with increasing adenoma size (P less than 0.001), while the cytosolic ratio again showed no difference. These findings suggested that the particulate PKC activity ratio had a possible correlation with the malignant potential of colorectal adenomas and that this ratio may be a useful biological indicator of colorectal carcinogenesis.

To additionally understand the molecular mechanisms and biologic indicators of colonic tumorigenesis through the adenoma-carcinoma sequence, protein kinase C (PKC) activity was examined in the cytosol and particulate fraction of specimen homogenates from 18 human colonic carcinomas and seven coexisting colonic adenomas and was compared with the adjacent normal mucosal tissues. This study showed that PKC activity could be detected precisely using mini DEAE-Sephacel column purification and histone III-S as a substrate. The PKC activity in both colonic adenoma and carcinoma progressively was reduced in the particulate fraction compared with that of the adjacent normal mucosa from each patient (74.9 +/- 11.3 and 42.4 +/- 9.37 versus 112 +/- 16.8 pmol/min/mg, P less than 0.001), although PKC activity in the cytosolic fraction was not significantly different (62.6 +/- 17.7 and 63.1 +/- 8.08 versus 56.4 +/- 7.32 pmol/min/mg) with respect to protein concentration. Both colonic adenomas and carcinomas showed a significant progressive decrease in total particulate PKC activity compared with the adjacent normal mucosa of each patient (13.5 +/- 2.18 and 7.64 +/- 1.35 versus 19.8 +/- 2.74 pmol/min/g tissue, P less than 0.001) and no difference in total cytosolic PKC activity (15.2 +/- 3.80 and 16.5 +/- 2.02 versus 14.6 +/- 1.81 pmol/min/g tissue). Among PKC activities in carcinomas, there was no difference related to histologic type, Dukes' staging, or carcinoembryonic antigen values. Among PKC activities in colonic adenomas, a significant decrease in particulate PKC correlated with size. The specific PKC activity in the particulate fraction decreased with advancing adenoma size (P less than 0.05). This study showed that colonic carcinogenesis might be associated with alterations in cellular levels of PKC activity and that the decrease in particulate PKC activity in the adenoma had a possible correlation with adenoma size.

Recent studies have identified a gene on chromosome 5q, designated MCC (mutated in colorectal cancers), as a candidate for the putative colorectal tumor suppressor gene that is located at 5q21. We examined loss of heterozygosity (LOH) at the MCC locus and its vicinity in sporadic colorectal carcinomas, using 12 RFLP (restriction fragment length polymorphism) markers. One clone, L5.71, had been used to identify the MCC gene; all 12 markers also had tight linkage to the gene responsible for adenomatous polyposis coli. All 40 cases studied were informative with at least one marker, and 22 of them (55%) showed LOH at one or more loci. LOH in the tumors was more frequent in the immediate vicinity of L5.71 than in distant parts of the chromosome, and a common region of deletion was detected between markers L5.62 and 15A6. In one case, alleles were retained at L5.71 and at loci proximal to L5.71, but alleles were lost at loci distal to L5.71. In another case, both alleles were retained at L5.71 but alleles were lost at loci proximal and distal to L5.71. These results support the conclusion that a tumor suppressor gene for colorectal carcinoma is located within or around locus L5.71.

A lectin histochemistry approach was adopted for comparative assessment of a colon cancer risk. Binding of Ulex europaeus agglutinin-I (UEA-I), peanut agglutinin (PNA), Griffonia simplicifolia agglutinin-II (GSA-II), and Dolichos biflorus agglutinin (DBA) was investigated in tumor and background tissue from a total of 34 adenoma and 44 cancer patients and compared with reaction patterns in control and familial adenomatous polyposis (FAP) patients. Adenoma patients with UEA-I positive rectal mucosa were found to have a 33.3 percent familial history of large bowel cancer, which was significantly higher (P less than 0.05) than the respective 4.0 percent figure for patients with negative rectal mucosa. In the cancer patients, an even stronger correlation was noted, with a 63.2 percent UEA-I positive family history association being recorded, as opposed to 4.0 percent in the negative rectal mucosa patients (P less than 0.01). Thus, the results suggest that, apparently, normal rectal background mucosa of individuals genetically at high risk for colon and rectal cancer demonstrates a specific lectin binding ability similar to that of FAP patients and that the simple method using UEA-I staining of rectal biopsy specimens can be of practical use in identification of high-risk colorectal cancer.

Familial adenomatous polyposis (FAP), which includes familial polyposis coli (FPC) and the Gardner syndrome (GS), is a genetically determined premalignant disease of the colon inherited by a locus (APC) mapping within 5q15-q22. To elucidate the role of 5q loss in FAP tumorigenesis, we analysed 51 colorectal tumors and seven desmoids from 19 cases of FPC and five GS patients, as well as 15 sporadic colon cancers. RFLP analysis revealed a high incidence of allelic deletion in hereditary colon cancers as well as in sporadic colon cancers with a peak at the APC locus. APC loss resulted primarily from interstitial deletion or mitotic recombination. Combined tumor and pedigree analysis in a GS family revealed loss of normal 5q alleles in three tumors, including a desmoid tumor, which suggests the involvement of hemizygosity or homozygosity of the defective APC gene in colon carcinogenesis and, possibly, in extracolonic neoplasms associated with FAP.

Sixty-four patients undergoing elective operations for cancer of the colon and rectum were given mechanical bowel preparation in the form of whole gut irrigation with polyethylene glycol electrolyte solution. When their colonic cleansing scores were compared, it was found that the preparation was significantly less effective in the left colon (n = 49) than in the right (n = 15), the mean (SEM) scores being 3.8 (0.56) and 2.65 (1.01), respectively, p less than 0.001. We then compared the scores of 26 patients with stenosing lesions with those of 38 that were not: in the right colon the score for stenosing tumours was 3.9 (0.14) compared with 3.8 (0.25) for non-stenosing tumours. In the left colon, however, they were 2.3 (0.23) and 2.9 (0.18), respectively (p less than 0.01). We conclude that stenosis of the colon caused by malignant lesions reduces the efficacy of mechanical bowel preparation with polyethylene glycol electrolyte solution in the left colon but not in the right colon.