We examined the incidence of point mutation in codon 12 of Ki-ras oncogene in human colorectal carcinomas by polymerase chain reaction in combination with alot-blot hybridization using mutation-specific ollgodeoxynucl...We examined the incidence of point mutation in codon 12 of Ki-ras oncogene in human colorectal carcinomas by polymerase chain reaction in combination with alot-blot hybridization using mutation-specific ollgodeoxynucleotide as probes. Among 72 colorectal carcinomas, point mutations were found in 36 samples, GGT to TGT in 16 cases and to AGT In 21 cases, one sample contain two different mutations. One of five normal mucosa contains the same mutation as in the adjacent carcinoma, suggesting that genetic alterations may also exist in the regions from which such carcinomas arise.展开更多
Aims: Ophthalmic pterygium is a potentially vision-threatening lesion of unkn own etiology, related to an exposure to solar light. Mutations to the ras genes are frequently observed in lesions related to an exposure t...Aims: Ophthalmic pterygium is a potentially vision-threatening lesion of unkn own etiology, related to an exposure to solar light. Mutations to the ras genes are frequently observed in lesions related to an exposure to solar light. The pr esent study aims at screening pterygia for mutations at codons 12 and 13 of the ras genes. Methods: In all, 50 pterygia were examined, together with respective blood samples and specimens of normal conjunctiva. A PCR reaction was performed to amplify sequences containing codons 12 and 13 of Ki-ras, H-ras, and N-ras. An RFLP analysis was then performed to detect point mutations at codon 12. The mutational status at codons 12 and 13 was further explored with sequencing of PC R products. Results: RFLP analysis revealed Ki-ras mutations at codon 12 in fiv e (10%) of pterygia, whereas H-ras or N-ras mutations were not observed. Sequ encing confirmed Ki-ras mutations at codon 12 and revealed absence of mutations at codon 13. The presence of Ki-ras mutations was significantly correlated wit h postoperative recurrence (P=0.02) and young age (P=0.04). Mutations were not o bserved in specimens of blood or normal conjunctiva for any of the genes examine d. Conclusions: The absence of Nras mutations is in agreement with previous repo rts concerning mucosal lesions. The detection of Ki-ras mutations and the assoc iation with postoperative recurrence implies a possible role of Ki-ras in the c linical profile of pterygium. The mechanism of Ki-ras mutations is unclear and could be independen t of the action of UV light.展开更多
Background. The point mutations occurring in codons 12 and 13 of the Ki-ras gene are useful genetic markers to identify intratumoral heterogeneity. A single tumor crypt, which consists of monoclonal cells, can be obta...Background. The point mutations occurring in codons 12 and 13 of the Ki-ras gene are useful genetic markers to identify intratumoral heterogeneity. A single tumor crypt, which consists of monoclonal cells, can be obtained using the crypt isolation method. Ki-ras gene mutations have been examined using the crypt isolation method to determine whether multiclonarity is present within the same tumor. Methods. Ki-ras gene mutations were analyzed using a crypt isolation technique coupled with polymerase chain reaction and direct sequencing in 21 sporadic colorectal carcinomas. The specimens were divided into two groups: a representative sample, which was composed of more than 50 tumor crypts, and a single tumor crypt sample. The latter consisted of 10 single tumor crypts, which were obtained from the same tumor separately. Results. Ki-ras gene mutations were found in 11 of 21 representative samples and in 12 of 21 single tumor crypt samples. In the 11 samples with Ki-ras mutation, Ki-ras mutations were also found in most single tumor crypts. Among the 12 base substitutions found, G:C to A:T transitions were the most commonly observed. There were no differences between the two samples in the types of Ki-ras mutations found. One Ki-ras mutation that was not detected in the representative sample was observed in only a single tumor crypt. Conclusions. Most carcinomas appear to have a homogeneous composition that may result from the successful progression of one of the clones having a Ki-ras mutation. Additional mutations in the Ki-ras gene were rarely observed in colorectal carcinomas.展开更多
文摘We examined the incidence of point mutation in codon 12 of Ki-ras oncogene in human colorectal carcinomas by polymerase chain reaction in combination with alot-blot hybridization using mutation-specific ollgodeoxynucleotide as probes. Among 72 colorectal carcinomas, point mutations were found in 36 samples, GGT to TGT in 16 cases and to AGT In 21 cases, one sample contain two different mutations. One of five normal mucosa contains the same mutation as in the adjacent carcinoma, suggesting that genetic alterations may also exist in the regions from which such carcinomas arise.
文摘Aims: Ophthalmic pterygium is a potentially vision-threatening lesion of unkn own etiology, related to an exposure to solar light. Mutations to the ras genes are frequently observed in lesions related to an exposure to solar light. The pr esent study aims at screening pterygia for mutations at codons 12 and 13 of the ras genes. Methods: In all, 50 pterygia were examined, together with respective blood samples and specimens of normal conjunctiva. A PCR reaction was performed to amplify sequences containing codons 12 and 13 of Ki-ras, H-ras, and N-ras. An RFLP analysis was then performed to detect point mutations at codon 12. The mutational status at codons 12 and 13 was further explored with sequencing of PC R products. Results: RFLP analysis revealed Ki-ras mutations at codon 12 in fiv e (10%) of pterygia, whereas H-ras or N-ras mutations were not observed. Sequ encing confirmed Ki-ras mutations at codon 12 and revealed absence of mutations at codon 13. The presence of Ki-ras mutations was significantly correlated wit h postoperative recurrence (P=0.02) and young age (P=0.04). Mutations were not o bserved in specimens of blood or normal conjunctiva for any of the genes examine d. Conclusions: The absence of Nras mutations is in agreement with previous repo rts concerning mucosal lesions. The detection of Ki-ras mutations and the assoc iation with postoperative recurrence implies a possible role of Ki-ras in the c linical profile of pterygium. The mechanism of Ki-ras mutations is unclear and could be independen t of the action of UV light.
文摘Background. The point mutations occurring in codons 12 and 13 of the Ki-ras gene are useful genetic markers to identify intratumoral heterogeneity. A single tumor crypt, which consists of monoclonal cells, can be obtained using the crypt isolation method. Ki-ras gene mutations have been examined using the crypt isolation method to determine whether multiclonarity is present within the same tumor. Methods. Ki-ras gene mutations were analyzed using a crypt isolation technique coupled with polymerase chain reaction and direct sequencing in 21 sporadic colorectal carcinomas. The specimens were divided into two groups: a representative sample, which was composed of more than 50 tumor crypts, and a single tumor crypt sample. The latter consisted of 10 single tumor crypts, which were obtained from the same tumor separately. Results. Ki-ras gene mutations were found in 11 of 21 representative samples and in 12 of 21 single tumor crypt samples. In the 11 samples with Ki-ras mutation, Ki-ras mutations were also found in most single tumor crypts. Among the 12 base substitutions found, G:C to A:T transitions were the most commonly observed. There were no differences between the two samples in the types of Ki-ras mutations found. One Ki-ras mutation that was not detected in the representative sample was observed in only a single tumor crypt. Conclusions. Most carcinomas appear to have a homogeneous composition that may result from the successful progression of one of the clones having a Ki-ras mutation. Additional mutations in the Ki-ras gene were rarely observed in colorectal carcinomas.
