MicroRNAs in Differentiation of Embryoid Bodies and the Teratoma Subtype of Testicular Cancer

Abstract

Background: Testicular germ cell tumours (TGCTs) are the most frequent tumour type among young, adult men. TGCTs can be efficiently treated, but metastases of the teratoma subtype, for which there are no circulating biomarkers, represent a challenge. Materials and Methods: Global microRNA expression in teratoma tissue and embryoid bodies was assessed using next-generation sequencing. Levels of microRNAs identified as potential biomarkers were obtained from serum of patients with teratoma and matched healthy men. Results: We identified miR- 222-5p, miR-200a-5p, miR-196b-3p and miR-454-5p as biomarker candidates from the tumour tissue and embryoid body screening but the expression of these microRNAs was very low in serum and not statistically different between patients and controls. miR-375-3p was highly expressed, being highest in patients with teratoma (p=0.012) but the levels of expression in serum from these patients and healthy controls overlapped. miR-371a-3p was not expressed in serum from patients with pure teratoma, only in patients with mixed tumours. Conclusion: The microRNA profiles of the teratoma subtype of TGCT and embryoid bodies were obtained and assessed for candidate circulating biomarkers, but none with high sensitivity and specificity for teratoma were identified in our study. We conclude that neither the proposed teratoma marker miR-375-3p nor miR-371a-3p are suitable as circulating teratoma markers.Testicular germ cell tumours (TGCT) are rare and account for less than 1% of all male cancer but represent the most common malignancy among young men between 15-40 years (1). The incidence of TGCT has been rising and is highest in men of northern European ancestry (2). Known main risk factors for TGCT are cryptorchism, prior diagnosis, increased adult height and a familial history of TGCT (3, 4). Gain of chromosome 12p and aneuploidy are found in nearly all cases (5) and more than 40 susceptibility loci with moderate risk have been identified (6, 7). These include KIT and KRAS, but with no major high-risk genes (8-10). Although genetic risk factors are observed, the rapid increase in TGCT incidence seen in Western countries since the 1950s cannot be explained by genetic factors alone. A gene-environmental model has been proposed where genetic factors work in concert with environmental and lifestyle factors (11). The associations of TGCT with environmental/lifestyle factors are debated and are generally considered weak, but include, among others, dietary intake, physical exercise, birth weight, exposure to hormones in utero, maternal smoking, parity and reduced gestational age (12).The majority of TGCTs are thought to arise from intratubular, incompletely differentiated embryonal cells where a failure in control of their latent developmental potential and reprogramming gives raise to germ cell neoplasia in situ (13,14). According to the World Health Organization's 2016 classification of testicular germ cell tumours, germ cell neoplasia in situ-derived tumours are further classified into seminom...

MicroRNAs in Testicular Germ Cell Tumors: The Teratoma Challenge

“…However, when compared to the control group, no significant differences in blood levels were discerned. On the other hand, miR-222-5p, miR-200a-5p, miR-196b-3p, and miR-454-5p were found to be ineffective in distinguishing teratoma from other conditions [39].…”

MiRNA biomarkers in cancers of the male reproductive system: Are we approaching clinical application?

“…The authors did not find any other miR-NAs predictive of pure teratoma through small RNA sequencing. 101 One of the critical clinical needs in TGCTs remains the lack of a reliable circulating teratoma marker, 78,102 but this may not depend solely on miRNAs, but actually on the combination with additional epigenetic biomarkers. Recently, a method was reported that combined miR-371a-3p quantification by RT-qPCR and hypermethylated RASSF1A quantification by ddPCR in serum, which allowed detection of TGCT (including teratoma), with a combined sensitivity of 100%, in a cohort with 109 patient and 29 control samples.…”

Serum Levels of MicroRNA-371a-3p (M371) Can Predict Absence or Presence of Vital Disease in Residual Masses After Chemotherapy of Metastatic Seminoma

“…In residual masses of metastatic non-seminomatous tumors, the new marker has been shown to identify those with residual vital cancer (25,26). However, the problem was that teratoma, which is present in about 30% of non-seminoma residual masses, does not express M371 (27)(28)(29). Thus, a negative M371 test in these cases will not obviate the need for postchemotherapy RPLND.…”