Identical, unique p53 mutations in a primary ovarian mucinous adenocarcinoma and a synchronous contralateral ovarian mucinous tumor of low malignant potential suggest a common clonal origin

Radiation-induced bystander effects, carcinogenesis and models

Implications for carcinogenesis of radiation-induced bystander effects are both mechanistic and practical. They include induction of second cancers, perturbations to tissue social control and induction of genomic instability and delayed or immediate mutations in areas not receiving a direct deposition of energy. Bystander effects have consequences for DNA damage-mutation-cancer initiation paradigms of radiation carcinogenesis that provide the mechanistic justification for low-dose risk estimates. If carcinogenesis does not result from directly induced DNA mutations, then the carcinogenic initiation process may not simply relate to radiation dose. Modification of the preclonal state through genetic and epigenetic mechanisms may occur. To deal with the complexity of these interactions, a 'chaotic' or 'bifurcation' model invoking autopoietic theory is proposed that could accommodate both beneficial (hormetic) and harmful effects of radiation at comparable doses. Carcinogenesis may then be thought of as the result of a disturbance of the genetic/epigenetic balance occurring within the organ. Ultimate clonality may reflect domination due to selection processes rather than the initiating damage.

Heterogeneous genetic alterations in ovarian mucinous tumors: application and usefulness of laser capture microdissection

Histologic observation of ovarian mucinous tumors suggests that there is a multistep transition through the accumulation of genetic alterations. We analyzed loss of heterozygosity (LOH) and replication error (RER) on TP53 and D17S855 as well as K-ras point mutations of the heterogeneous histologic areas of the same tumor in 26 cases of ovarian mucinous tumor. The laser capture microdissection (LCM) technique has been applied to the study of K-ras point mutation in 10 cases. As for genetic alterations for LOH or RER on TP53 and D17S855, 2 (1 borderline tumor and 1 carcinoma) of 14 cases and 4 (1 borderline tumor and 3 carcinomas) of 12 cases, respectively, showed genetic heterogeneities in different histologic areas. Six (2 borderline tumors and 4 carcinomas) of 18 cases showed heterogeneity of K-ras point mutation in the different histologic areas of the same tumor, and 5 (1 cystadenoma with Brenner tumor component, 2 borderline tumors, and 2 carcinomas) of 10 cases showed heterogeneous K-ras mutation pattern in the same tumor when the LCM technique was used. Atypical areas tended to show K-ras point mutations frequently. Out of 3 cases of mixed mucinous cystadenoma and Brenner tumor, 1 case showed K-ras point mutation in the Brenner tumor area but not in the area of mucinous cystadenoma. These preliminary results suggest that a subset of ovarian mucinous tumors occur through multistep carcinogenesis and show that LCM is useful for molecular pathologic studies.