Kazunori Tsujita

Undetectable expression of hMLH1 protein in sporadic colorectal cancer with replication error phenotype

PURPOSE: Four DNA mismatch repair genes have been identified as being susceptible genes for hereditary nonpolyposis colorectal cancer. Deficiency of one of the mismatch repair genes causes the replication error phenotype in more than 80 percent of patients with hereditary non-polyposis colorectal cancer and in 10 to 30 percent of patients with sporadic colorectal cancer. To determine which mismatch repair gene is lacking the function in patients with replication error-positive colorectal cancer, several approaches have been used at the nucleic acid and protein levels. We studied replication error in 40 samples of randomly selected colorectal cancers and expression of hMSH2 and hMLH1 proteins analyzed by immunoblot in the tumor and normal tissues of the replication error-positive and replication error-negative samples. MATERIALS AND METHODS: Frozen tumor and normal tissues were obtained from 40 Japanese patients who had colorectal cancer. According to the Amsterdam criteria, those patients were classified as having 39 sporadic and 1 unknown colorectal cancers. Genomic DNA was extracted from tumor and normal tissues for determining replication error with eight microsatellite markers. Expression of hMSH2 and hMLH1 proteins in cell lysates of tumor and normal tissues of 16 patients was analyzed by immunoblot. RESULTS: The replication error phenotype was found in 6 (15 percent) of the 39 sporadic cases. hMLH1 protein was not detected in two of the six replication error-positive tumor tissues and not in the normal tissues, indicating that the tumor cells of the two patients had severe mutations in both alleles of thehMLH1gene. Another four replication error-positive and ten replication error-negative tumors and normal tissues expressed hMLH1 protein. hMSH2 protein was detected in all samples. CONCLUSION: hMLH1 protein was undetectable in the two tumor tissues of the six replication error-positive samples of sporadic colorectal cancer. The detection procedure used here may have potential use for determining a dysfunctional mismatch repair gene product.

Various AGC repeat numbers in the coding region of the human transcription factor gene E2F-4.

The E2F family of transcription factors regulates the expression of genes required for DNA synthesis and cell cycle control. The AGC triplet repeat in the coding region of the E2F‐4 gene, a member of the family, has been reported to be mutated in colorectal cancers with a microsatellite instability (MSI) phenotype. We found a wider range variation of the repeat number in DNAs from tumors, the corresponding normal mucosa, and healthy individuals. A total of 5 repeat variants, ranging from 8 to 17 AGC repeats, was detected in 6 (9.7%) of the 62 healthy individuals and 8 (8.9%) of the 90 normal DNAs of the patients. The wild‐type 13 repeat was present in all of these individuals. The variation of the AGC repeat number may be a polymorphism. Further, loss of heterozygosity (LOH) at the E2F‐4 locus in the tumor tissues of 2 (25%) of the 8 informative cases was detected. The variation may be a useful marker for detection of LOH in primary tumors. Hum Mutat 15:296–297, 2000.

A Case of Hyperplastic Polyp at The Ureterosigmoidal Anastomosis Occuring 11 Years after Total Cystectomy.

今回, われわれは膀胱全摘後11年して血便を契機に発見された, 尿管S状結腸吻合に発生した乳頭状腫瘍を経験したので報告する. 症例は58歳の男性で, 血便を主訴に当院を受診した. 入院後の注腸検査と下部消化管内視鏡検査にてS状結腸の尿管吻合近傍に腫瘤の形成を認めたため, 悪性腫瘍を疑ったが, 生検ではGroup2であった. 尿管S状結腸吻合術後のS状結腸に発生する腫瘤には癌の頻度が高いことからS状結腸切除を行った. 組織学的には悪性所見は認められず, 陰窩上皮の乳頭状の増生と間質の浮腫, 炎症を伴う過形成性ポリープと診断した. 膀胱全摘出後の尿管S状結腸吻合部に発生した過形成性ポリープの報告は比較的まれで, 今回, 自験例を含めた報告例についての文献的考察を行った.