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Recently, an activating mutation of the SRCGene has been implicated in about one‐tenth of advanced colon cancers. The SRC 531 mutation results in truncation of SRC directly C‐terminal to the regulatory Tyr 530 and appears to activate the Tyr 530. To investigate whether mutation of SRC plays an important role in the development and progression of gynecological tumors, we performed mutational analysis of the entire coding region of SRC in 70 ovarian carcinomas, 68 endometrial carcinomas and 3 endometrial stromal sarcomas by means of polymerase chain reaction‐single strand conformation polymorphism (PCR‐SSCP) followed by nucleotide sequencing and restriction fragment length polymorphism (RFLP) analysis. We found one truncated mutation at codon 531 (Gln to Stop) in an endometrial carcinoma. However, we found no mutation of this gene in ovarian carcinoma or endometrial stromal sarcoma. Our results suggest that mutation of SRC may be implicated in a small proportion of endometrial carcinomas.

To investigate the contribution of β‐catenin to the development of endometrial carcinoma, we searched for genetic alterations of the β‐catenin gene in primary endometrial carcinomas. Mutational analysis of exon 3 of the β‐catenin gene, encoding the serine/threonine residues for GSK‐3β phosphorylation, was performed for 35 tumors. Nucleotide sequencing analysis revealed that 5 tumors (5/35, 14%) contained mutations (S33C, S37C, S37F, T41A) that altered potential GSK‐3β phosphorylation sites. Each of the mutations resulted in the substitution of serine/threonine residues that have been implicated in the down‐regulation of β‐catenin through phosphorylation by GSK‐3β kinase. Furthermore, the incidence of β‐catenin mutations was significantly higher in early‐onset (3 of 5) than that in late‐onset tumors (2 of 30) (P=0.014, Fisher's exact test). Replication error (RER)‐positive phenotype was not detected in tumors with the β‐catenin gene mutation, although 10 of 35 tumors revealed RER. We performed immunohistochemistry of β‐catenin in 17 cases for which tissue samples were available. We confirmed accumulation of β‐catenin protein in both the nucleus and cytoplasm in 3 tumors, including two in which amino acid alterations had occurred at codon 33 and 37. The other case had no mutation in exon 3. Our results suggested that mutations at serine/threonine residues involved in phosphorylation by GSK‐3β affected the stability of β‐catenin. Accumulation of mutant β‐catenin could contribute to the development of a subset of endometrial carcinomas, particularly those of the early‐onset type.

To investigate the contribution of the β‐cateningene to the development of ovarian carcinomas, mutational analysis of exon 3 of the β‐cateningene was conducted. We analyzed 61 primary ovarian carcinomas, consisting of 49 non‐endometrioid‐type and 12 endometrioid‐type tumors, for genetic alteration of the β‐cateningene. Five carcinomas showed β‐cateninmutations (S37C, T41I, T41A), including 4 (33%) of 12 endometrioid‐type tumors and 1 (14%) of 7 mucinous‐type tumors. All of these mutations altered at the serine/threonine residues that are potential sites of GSK3‐β phosphorylation. We detected no carcinomas with interstitial deletion involving exon 3 of β‐catenin.Furthermore, we immunohistochemically studied 27 of the 61 ovarian carcinomas. Both nuclear and cytoplasmic β‐cateninexpressions were demonstrated in 4 of the 27 ovarian carcinomas for which tissue samples were available for examination. All 4 cases exhibited mutations in exon 3 of β‐catenin, including a mucinous carcinoma. Our results suggested that β‐cateningene mutation at potential GSK3‐β phosphorylation sites results in accumulation of β‐catenin protein within the cells and its translocation to nuclei. Accumulated β‐catenin protein may be involved in the development of endometrioid‐type ovarian carcinomas, and some mucinous‐type ovarian carcinomas.