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Oncotarget. 2018 Feb 22;9(20):15266-15274. doi: 10.18632/oncotarget.24555. eCollection 2018 Mar 16.

PIK3CA and KRAS mutations in cell free circulating DNA are useful markers for monitoring ovarian clear cell carcinoma.

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Laboratory of Molecular and Genetic Information, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo, Japan.
Department of Obstetrics and Gynecology, Jikei University School of Medicine, Tokyo, Japan.
Department of Obstetrics and Gynecology, Jikei University, Kashiwa Hospital, Chiba, Japan.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.


Ovarian clear cell carcinoma (OCCC) exhibits distinct phenotypes, such as resistance to chemotherapy, poor prognosis and an association with endometriosis. Biomarkers and imaging techniques currently in use are not sufficient for reliable diagnosis of this tumor or prediction of therapeutic response. It has recently been reported that analysis of somatic mutations in cell-free circulating DNA (cfDNA) released from tumor tissues can be useful for tumor diagnosis. In the present study, we attempted to detect mutations in PIK3CA and KRAS in cfDNA from OCCC patients using droplet digital PCR (ddPCR). Here we show that we were able to specifically detect PIK3CA-H1047R and KRAS-G12D in cfDNA from OCCC patients and monitor their response to therapy. Furthermore, we found that by cleaving wild-type PIK3CA using the CRISPR/Cas9 system, we were able to improve the sensitivity of the ddPCR method and detect cfDNA harboring PIK3CA-H1047R. Our results suggest that detection of mutations in cfDNA by ddPCR would be useful for the diagnosis of OCCC, and for predicting its recurrence.


KRAS; OCCC; PIK3CA; cfDNA; digital PCR

Conflict of interest statement

CONFLICTS OF INTEREST The authors declare that they have no conflicts of interest.

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