Fig. 1

CircPLEKHM3 is down-regulated in ovarian cancer and associated with prognosis. a Scatterplot showing the relative expression of circRNA in ovarian tumor and normal tissues. CircPLEKHM3 is marked as a dark circle. b Schematic diagram of the generation of circPLEKHM3. CircPLEKHM3 was back-spliced from exon 3 of PLEKHM3. Primers were designed on exon 2 to examine the expression of linear transcripts of PLEKHM3. To validate the existence of circPLEKHM3, primers were designed on the spliced junction, followed by Sanger sequencing. To obtain the full-length sequences of circPLEKHM3, three pairs of primers in opposite directions were designed on exon 3, and their PCR products were sequenced. c qRT-PCR analysis of the relative abundance of circPLEKHM3 and PLEKHM3 mRNA in A2780 and OV90 treated with RNase R. d PCR product of full-length circPLEKHM3. Primers used to clone full-length circPLEKHM3 are indicated in Fig. 1b and their sequences can be found in Additional file 2: Table S2. e, f qRT-PCR analysis of the expression of circPLEKHM3 and PLEKHM3 in a new independent cohort including 12 tumor tissues from ovarian cancer patients and 12 normal ovarian tissues from patients with benign gynaecologic diseases (e), and 26 primary ovarian carcinoma and matched peritoneal metastatic ovarian carcinomas (f). g Kaplan–Meier survival analysis of circPLEKHM3 expression in ovarian cancer patients. The expression of circPLEKHM3 was evaluated using a BaseScope assay in 86 FFPE tissues from ovarian cancer patients. h Representative images (20× magnification) of the BaseScope assay for circPLEKHM3 in patients with better prognosis (upper) and worse prognosis (lower). CircPLEKHM3 transcript appears as a distinct red dot, with each dot representing a single RNA transcript. Data are presented as mean ± SD; n = 3; ** P < 0.01, *** P < 0.001