Exosomal miR-1290 is a potential biomarker of high-grade serous ovarian carcinoma and can discriminate patients from those with malignancies of other histological types
microRNAs (miRNAs) stably exist in circulating blood encapsulated in extracellular vesicles such as exosomes; therefore, serum miRNAs have the potential to serve as novel cancer biomarkers. New diagnostic markers to detect high grade serous ovarian cancer (HGSOC) are urgently needed. The aim of this study was to identify miRNAs specific to HGSOC and analyze whether serum miRNA can discriminate HGSOC patients from healthy controls or patients with ovarian malignancies of other histological types.
Exosomes from ovarian cancer cell lines were collected and exosomal miRNAs extracted. miRNA microarray analysis revealed several elevated miRNAs specific to HGSOC. Among these, we focused on miR-1290. Sera from 70 ovarian cancer patients and 13 healthy controls were gathered and its expression levels detected by quantitative real-time polymerase chain reaction.
In HGSOC patients, serum miR-1290 was significantly overexpressed compared to in healthy controls (3.52 fold; P = 0.03), unlike in patients with ovarian cancers of other histological types. The relative expression of miR-1290 was higher in advanced stages of HGSOC than in early stages (4.23 vs. 1.58; P = 0.23). Its expression significantly decreased after operation (5.87 to 1.17; P < 0.01), indicating that this miRNA reflects tumor burden. A receiver operating characteristic curve analysis showed that at the cut-off of 1.20, the sensitivity and specificity were 63% and 85% respectively for discriminating patients with HGSOC (area under the curve [AUC] = 0.71) from healthy controls, and at the cut-off of 1.55, the sensitivity and specificity were 47% and 85% respectively for discriminating patients with HGSOC (AUC = 0.76) from those with malignancies of other histological types.
Serum miR-1290 is significantly elevated in patients with HGSOC and can be used to discriminate these patients from those with malignancies of other histological types; it is a new potential diagnostic biomarker for HGSOC.
KeywordsmicroRNA miR-1290 Ovarian cancer HGSOC Biomarker
Area under the curve
Cancer antigen 125
Epithelial ovarian cancer
Federation of Gynecology and Obstetrics
Human epididymis 4
High grade serous ovarian carcinoma
Immortalized ovarian surface epithelium
N-myc downstream regulated gene 1
Primary debulking surgery
Quantitative real-time polymerase chain reaction
Receiver operating characteristics
Transient receptor potential cation channel, subfamily M, member 7
Epithelial ovarian cancer (EOC) is one of the most common gynecologic malignancies and the fifth leading cause of cancer-related death in women . The most common histological subtype of EOC is high grade serous ovarian carcinoma (HGSOC). HGSOC is asymptomatic in the early stages and causes rapid dissemination through the peritoneum; therefore, it is typically diagnosed at advanced stages when it is incurable . The standard treatment for HGSOC is debulking surgery, followed by repeated courses of platinum- and taxane-based chemotherapy. However, most patients with HGSOC eventually have a relapse despite receiving intensive treatments with a 5-year survival rate of patients with advanced stage being below 30%. In contrast, the few patients who are diagnosed at stage I have a 5-year survival rate of over 90% , indicating that the early detection of ovarian cancer can drastically improve the prognosis of patients .
A feasible way to diagnose cancer at an early stage is to establish a useful and comprehensive diagnostic biomarker. To date, only 2 biomarkers, cancer antigen 125 (CA125) and human epididymis 4 (HE4) have been approved by the Food and Drug Administration as biomarkers for EOC . Several studies have reported that HE4 has the highest sensitivity for detecting EOC as a single biomarker; while a combined biomarker of CA125 and HE4 is a more accurate predictor of malignancy than either alone [6, 7, 8]. HE4 has not been widely used in clinical settings despite its high sensitivity, and conventional CA125 remains the most widely used diagnostic serum biomarker among patients with EOC . Therefore, pelvic examination, transvaginal ultrasonography, and CA125 tests are performed during routine diagnostic procedures; however, they have failed to detect the disease at an early stage and thus have not significantly reduced the mortality rate of patients with EOC . It is obvious that there is an urgent need to develop a new biomarker for HGSOC to detect it at earlier stages and to provide better treatment options.
Emerging evidence has revealed posttranscriptional regulation of gene expression by microRNAs (miRNAs). miRNAs consist of small non-coding RNAs of approximately 22 nucleotides. Aberrant expression of miRNAs has been identified as a key factor in cancer tumorigenesis and progression. miRNAs are found in the cell-free fraction of blood and can be reliably measured  since miRNAs circulating in the serum are present in a variety of forms, such as within small extracellular microvesicles known as exosomes where they are protected from endogenous RNase degradation . Therefore, they have the potential to serve as a disease-specific biomarker for EOC. While various studies have suggested the clinical relevance of circulating miRNAs as diagnostic and prognostic biomarkers for EOC, robust studies evaluating circulatory exosomal miRNA signatures in HGSOC have yet to be reported .
With these in mind, we collected exosomes from the culture media of serous EOC cell lines, performed a miRNA microarray, and found that miR-1290 was specifically elevated in these EOC-derived exosomes. To evaluate the potential of miR-1290 as a biomarker for EOC (specifically HGSOC), its expression level in patients was analyzed and compared with that in healthy controls or in patients with malignancies of other histological types.
Dulbecco’s modified Eagle medium and Roswell Park Memorial Institute 1640 medium were obtained from Nacalai Tesque (Kyoto, Japan). Fetal bovine serum (FBS; #172012) was purchased from Sigma Aldrich (St. Louis, MO). Antibody against CD63 (#11–343-C025) was purchased from EXBIO (Vestec, Czech Republic). Donkey anti-mouse IgG 10 nm gold (#ab39593) was purchased from Abcam (Cambridge, UK).
TYK-nu cell line was purchased from Health Science Research Resources Bank (Osaka, Japan). HeyA8 cell line was generously contributed by Dr. Anil Sood (MD Anderson Cancer Center, Houston, TX). IOSE cell line was generously contributed by Dr. Masaki Mandai (Kyoto University, Kyoto, Japan). Briefly, ovarian surface epithelial cells were collected from normal ovary and transfected with SV40 large T antigen and human telomerase reverse transcriptase . These cell lines were cultured in optimal medium according to the suppliers’ recommendations.
Exosome isolation and miRNA extraction from exosomes
Exosomes were isolated from conditioned medium (CM) by an ultracentrifugation method as previously described . The exosome-containing pellet was resuspended in phosphate-buffered saline (PBS) and the amount of exosomal protein was assessed by the Lowry method (Bio-Rad, Hercules, CA). Total RNA was extracted using TRIzol reagent (Life Technologies, Carlsbad, CA: #15596–018).
The morphology and characteristics of exosomes were verified by transmission electron microscopy using a H-7650 transmission electron microscope from Hitachi (Tokyo, Japan) as described .
Exosomal miRNA microarray
A miRNA microarray using the GeneChip miRNA 4.0 array (Affymetrix, Santa Clara, CA) was performed and analyzed by Filgen (Nagoya, Japan). Briefly, 1000 ng of each miRNA sample was biotin-labeled using a Flash TagTM Biotin HSR RNA labeling kit for Affymetrix GeneChip miRNA arrays (Affymetrix) according to the manufacturer’s protocol. Hybridization solution was prepared using 110.5 μL hybridization master mix and 21.5 μL biotin-labeled sample. The array was incubated using a GeneChip Hybridization Oven 645 (Affymetrix) and washed using a GeneChip Fluidics station 450 (Affymetrix) according to the manufacturer’s protocol. The washed array was analyzed using a GeneChip Scanner 3000 7G (Affymetrix).
Patients and samples
In a retrospective cohort study, data were reviewed from patients with ovarian cancer treated at Osaka University Hospital (Suita, Osaka) between January 2013 and May 2015. The study was approved by the Institutional Review Board of the institute and conformed to the provisions of the Declaration of Helsinki. Written informed consent was obtained from every participant for the use of their samples.
Blood samples were collected from healthy volunteers (n = 13) and patients with ovarian cancer (n = 70). From 16 HGSOC patients, blood samples were collected twice at the timing of admission for primary debulking surgery (PDS) (2 or 3 days before surgery) and the initial postoperative chemotherapy (approximately 28 days after surgery). The samples were centrifuged at 1500 x g for 10 min at 4 °C and the upper sera phases were stored in aliquots at − 80 °C until use.
miRNA extraction from serum
miRNAs were extracted from 200 μL serum samples using an miRNeasy Serum/Plasma Kit (QIAGEN, Hilden, Germany) according to the manufacturer’s protocol. The eluates containing miRNAs were stored at − 80 °C until use.
Quantitative real-time polymerase chain reaction (qRT-PCR) of miR-1290
The expression of miR-1290 was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). TaqMan miRNA assays (#4366596, Applied Biosystems, Foster City, CA) with specific reverse transcription primers and probes were used to quantify the expression of mature human miR-1290 (5′ – UGGAUUUUUGGAUCAGGGA – 3′). Before RNA extraction, 100 fmol/mL of synthesized cel-miR-39 (#4427975, Applied Biosystems) was added to an equal volume of serum to serve as a normalizer. The relative levels of miR-1290 in serum were expressed using the 2−ΔCt method, in which ΔCt = CtmiR-1290 − Ctcel-miR-39. qRT-PCR was performed in triplicate with the StepOnePlus Real-Time PCR system (Applied Biosystems).
JMP software version 13.0.0 (SAS Institute, Tokyo, Japan) was used for statistical analysis and the construction of statistical plots. Differences in miRNA expression levels in non-paired samples were tested by the Mann-Whitney U test. The Wilcoxon test was used to compare miRNA expression in paired samples. The values are presented as the mean ± SD and a two-sided P < 0.05 was considered to indicate a statistically significant difference. In the graphs showing the relative expression of miR-1290 in the patients’ sera, Diagnostic performance for each biomarker individually and in combination was evaluated using receiver operating characteristic (ROC) curve analysis and by reporting the area under the curve (AUC).
The identification of candidate miRNAs
Serum miRNA-1290 expression levels in EOC
Characteristics of the participants
(n = 13)
Epithelial ovarian cancer
(n = 70)
FIGO stages of the HGSOC patients
(n = 30)
Serum miR-1290 is significantly elevated in HGSOC and reflects tumor burden
Serum miR-1290 has the potential to differentiate HGSOC patients from non-HGSOC patients
Recently, aberrant expression of various miRNAs has been identified to be closely associated with the initiation and progression of cancer [10, 21, 22]. In this study, through a comprehensive study with miRNA microarray, we identified miR-1290 as being significantly elevated in HGSOC-derived exosomes. Furthermore, we found that serum miR-1290 was significantly elevated in patients with HGSOC and could discriminate such patients from those with malignancies of other histological types, suggesting its potential as a novel diagnostic biomarker for HGSOC. Although CA125, a conventional biomarker of EOC, showed a better performance to discriminate all EOC patients from healthy controls than serum miR-1290, miR-1290 showed a better performance to discriminate HGSOC patients from non-HGSOC patients than CA125.
Exosomes are cell-derived extracellular vesicles that promote cell-cell communication, shuttling various molecules including miRNAs to recipient cells . In the blood, most miRNAs are present in exosomes as exosomal miRNAs and are not degraded by proteases ; therefore, exosomal miRNAs in body fluids have the potential to diagnose normal or abnormal processes or diseases . Several studies have shown the clinical relevance of circulating miRNAs as diagnostic and prognostic biomarkers for ovarian cancer, using blood plasma or serum as we reviewed previously . In 2008, Taylor et al. first reported that 8 exosomal miRNAs (miR-21, miR-141, miR-200a, miR-200b, miR-200c, miR-203, miR-205, and miR-214) from sera were elevated in ovarian cancer patients as compared to benign controls. These miRNA signatures from exosomes were parallel to those from the originating tumor cells, indicating that circulating miRNA profiles accurately reflect the tumor profiles . Recently, Yokoi et al. developed a novel predictive model using a combination of 8 circulating serum miRNAs (miR-200a-3p, miR-766-3p, miR-26a-5p, miR-142-3p, let-7d-5p, miR-328-3p, miR-130b-3p, and miR-374a-5p) which could distinguish EOC patients from healthy controls with high sensitivity and specificity (0.92 and 0.91, respectively) . They demonstrated that most of these miRNAs were packaged in extracellular vesicles, including exosomes, and were derived from ovarian cancer cells. In a cohort of 56 HGSOC patients, Shah et al. reported a combination of miR-375 and CA-125 was the strongest discriminator of healthy versus HGSOC serum with an AUC of 0.956 and the combination of miR-34a-5p and CA-125 the strongest predictor of completeness of surgical resection with an AUC of 0.818 . However, despite these interesting reports, progress for the development of reliable serum biomarkers for the early detection of HGSOC remains very limited due to the small size of available research cohorts.
Given that HGSOC is the most common EOC and responds well to chemotherapy, if we had a biomarker to differentiate HGSOC from non-HGSOC, it would be clinically advisable to choose NAC or PDS for the treatment of stage III/VI ovarian cancer. Herein, we showed that miR-1290 is better than CA125 for distinguishing HGSOC from non-HGSOC, suggesting the potential of this miRNA as a biomarker. Thus, in addition to CA125 and HE4, the measurement of miR-1290 may provide a more accurate diagnosis for EOC.
Several limitations should be acknowledged. The sample size is too small to reach a solid conclusion. Large and prospective registry-embedded trials would be needed to strengthen our hypothesis that serum miR-1290 can serve as a biomarker of HGSOC. Besides, the mechanisms behind why miR-1290 is up-regulated in HGSOC serum need to be explored. Further studies would be indispensable for the identification of putative target genes of miR-1290 in HGSOC to clarify its role. Endogenous controls for miRNA normalization remain critical for the reliable quantification of miRNAs. RNU-6B, RNU-48, or miR-16 are commonly used as endogenous controls; however, no definitive control gene has been established . In this study, exogenous miRNA (synthesized cel-miR-39) was used as a control for miRNA normalization. The establishment of an appropriate normalization method is indispensable for clinical use.
Serum miR-1290 reflects tumor burden and shows promise as a potential biomarker to aid in the diagnosis of HGSOC. Elevated serum miR-1290 has the potential to distinguish HGSOC patients from non-HGSOC patients. The addition of this miRNA measurement to conventional biomarkers such as CA125 and HE4 may provide an accurate diagnosis for EOC. Further studies would be needed to elucidate the molecular mechanisms of miR-1290 in HGSOC tumorigenesis and progression.
This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan (18 K09227 and 26293360 to KS). This work was also supported by Takeda Science Foundation (to KS) and Osaka Medical Research Foundation for Intractable diseases (to KN).
Availability of data and materials
All data generated or analyzed during this study are included in this published article.
MK performed the experiments and wrote the initial manuscript; KS designed the study and revised and finalized the manuscript; KN and AY performed the experiments and analyzed the data; MM, AS, KI, EN, MK, KH and SM were involved in drafting this article; TK supervised the study. All authors read and approved the final version of the manuscript.
Ethics approval and consent to participate
This study was approved by the ethics committee of Osaka University Hospital.
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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