Background: Ovarian clear cell carcinoma (OCCC) is one of the 4 major histological types of ovarian carcinoma (OVC) and is frequently arising from ovarian endometriotic cysts. OCCC is rare in the United States and western countries, but it is more frequent in Japan and may be seen in almost 25% of OVC. OCCC commonly shows chemo-resistance which makes difficult to treat OCCC. In order to develop the new therapeutics for OCCC, genetic abnormalities that lead to the development of OCCC need to be elucidated in detail. The comprehensive analysis using next-generation sequencing has rapidly revealed the accumulation of genetic abnormalities in many cancers. However, the significance of each abnormality has not been elucidated. Therefore, functional screening using a cDNA expression library was performed in order to identify genes involved in the pathogenesis of OCCC.
Methods: The mRNA was extracted from an OCCC cell line, RMG-1, and a cDNA library was established using a retroviral vector. This cDNA library was transfected into mouse NIH3T3 cells, and then the transformed foci which formed multilayered growth were picked up and the inserted DNAs of those foci were detected by sequencing. The mRNA and protein expression and the transforming ability of the identified genes were confirmed by immunohistochemistry and focus-formation assay.
Result: Seven genes were isolated; Dishevelled 1(DVL1), beta subunit of Sec61 (SEC61B), K-specific demethylase 4A (KDM4A), chromosome 1 open reading frame 38 (C1ORF38), splicing factor 1 (SF1), ribosomal protein S2 (RPS2), and ribosomal protein S3A (RPS3A). Of these genes, RT-PCR and immunostaining revealed that the expression of SEC61B and C1ORF38 was stronger than that in other histological types of ovarian cancer. A mutational analysis of the DVL1 c-terminal region detected 3 point-mutations in RMG1 cells, whereas no mutation was found in 24 cases of OCCC. Focus formation was confirmed by the transfection of SEC61B, C1ORF38, and DVL1 into NIH3T3 cells.
Conclusion: These results suggest that SEC61B, C1ORF38, and DVL1 may be involved in the pathogenesis of OCCC.
Citation Format: Tsutomu Miyamoto, Yasushi Yamada, Koichi Ida, Ryoichi Asaka, Hisanori Kobara, Hirofumi Ando, Hiroyasu Kashima, Akihisa Suzuki, Tanri Shiozawa. Functional screening of genes involved in carcinogenesis using a cDNA expression library of ovarian clear cell carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3091.