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Abstract. Recent data have provided information regarding the profiles of clear cell carcinoma of the ovary (CCC) with adenine-thymine rich interactive domain 1A (ARID1A) mutations. The purpose of this review was to summarize current knowledge regarding the molecular mechanisms involved in CCC tumorigenesis and to describe the central role played by the aberrant chromatin remodeling. The present article reviews the English-language literature for biochemical studies on the ARID1A mutation and chromatin remodeling in CCC. ARID1A is responsible for directing the SWI/SNF complex to target promoters and regulates the transcription of certain genes by altering the chromatin structure around those genes. The mutation spectrum of ARID1A was enriched for C to T transitions. CCC and clear cell renal cell carcinoma (ccRCC) resemble each other pathogenetically. Dysfunction of the ARID1A protein, which occurs with VHL mutations in ccRCC, is responsible for loss of the assembly of the ARID1A-mediated histone H2B complex. Therefore, ARID1A acts as a chromatin remodeling modifier, which stimulates cell signaling that can lead to cell cycle arrest and cell death in the event of DNA damage. The dysfunction of ARID1A may result in susceptibility to CCC carcinogenesis through a defect in the repair or replication of damaged DNA. IntroductionEpithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy worldwide. Epidemiology calculations of lifetime risk for EOC are that 1 in 55 women is likely to develop EOC during their lifetime (1). Since EOC is more likely to be advanced stage with unfavorable tumor biology, there are serious limitations to the surgical and oncological treatment available. Therefore, it is crucial to determine the earliest possible diagnosis. Early diagnosis and surgical resection offer patients the best opportunity of excellent long-term survival. On the other hand, patients who either present with metastatic disease or develop distant relapse within 6 months after surgery and chemotherapy have a poor prognosis. Among EOC, clear cell carcinomas of the ovary (CCC) are frequently characterized by chemoresistance and recurrence, resulting in a poor prognosis (2). Since CCC are resistant to conventional cytotoxic (platinum plus taxan-based) chemotherapy, the prognosis is mostly poor (3). In the USA, the incidence of CCC is 5% of all EOC, but the incidence in Japan is reported to be over 20% of all EOC. Thus, Japanese oncologists have focused on investigating the molecular pathogenesis and treatment strategies of CCC.At present, little is known about the molecular genetic mechanisms that are involved in CCC tumorigenesis. Accumulated somatic mutations found in a subset of cancer genes are frequently noted. Such mutations include insertions/deletions (indels) and base substitutions that act as the 'driver mutations' in oncogenesis. These mutations result in the activation of proto-oncogenes (gain of function) or the inhibition of tumor suppressor genes (loss of function) during the process of carcinoge...