Serum miR371 in testicular germ cell cancer before and after orchiectomy, assessed by digital-droplet PCR in a prospective study

Perioperative Serum MicroRNA 371a-3p and 372-3p Levels in Patients with Clinically Localized Testicular Masses

Background

MicroRNAs (miRNAs) show promise as blood-based tumor markers for germ cell tumors (GCTs), with miRNA-371-3p being the most studied. The marginal benefit of including other candidate miRNAs to aid with the management of testicular GCTs remains unclear.

Objective

To assess the performance of our combined miRNA assay (371a-3p and 372-3p) in patients with clinically localized testicular masses.

Design setting and participants

This was a retrospective review of patients prospectively enrolled in an ongoing protocol collecting serum miR-371a-3p and miR-372-3p levels (together, Memorial Sloan Kettering Cancer Center [MSK] miRNA assay [MMA]) in patients with a suspected or diagnosed testicular GCT.

Outcome measurements and statistical analysis

The coprimary outcomes of interest were sensitivity and specificity of miR-371a-3p and 372-3p, individually and together, to detect nonteratomatous GCTs in the orchiectomy specimen. Secondary outcomes included additional assay diagnostic parameters, the relationship of patient and disease factors with variations in miRNA levels, and temporal patterns of miRNA normalization after orchiectomy.

Results and limitations

Sixty-two patients were included, 52 had a viable GCT at orchiectomy, and ten had no cancer or a non-GCT. Forty-six patients with a GCT had positive preorchiectomy MMA (sensitivity 88.5% [95% confidence interval {CI}: 79.8, 97.2]), and one patient had positive preorchiectomy MMA but no GCT (specificity 90.0% [95% CI: 71.4, 100]). The diagnostic performance of miR-371a-3-p and miR-372-3p was similar. The time for miRNA to decrease to undetectable levels varied, with some patients having positive levels up to 3 wk after orchiectomy.

Conclusions

The biomarkers miR-371a-3p and miR-372-3p demonstrated high sensitivity and specificity for localized testicular GCTs, but causes of variation in relative miRNA levels and time to normalization for individual patients remain unclear.

Patient summary

We studied the ability of the blood-based biomarkers miR-371a-3p and miR-372-3p to detect testicular cancer (germ cell tumors) in patients with small testicular masses. We found that together and individually these were sensitive and specific for testicular cancer.

Primary Retroperitoneal Lymph Node Dissection as Treatment for Low-volume Metastatic Seminoma in a Population-based Cohort: The Swedish Norwegian Testicular Cancer Group Experience

Background and objective

There is an unmet need to avoid long-term morbidity associated with standard cytotoxic treatment for low-volume metastatic seminoma. Our aim was to assess the oncological efficacy and surgical safety of retroperitoneal lymph node dissection (RPLND) as treatment in a population-based cohort of metastatic seminoma patients with limited retroperitoneal lymphadenopathy.

Methods

Sixty-two seminoma patients in Norway and Sweden were included in the cohort from 2019 to 2022. Patients with lymphadenopathy ≤3 cm, having primary clinical stage (CS) IIA/B or CS I with a relapse, were operated with uni- or bilateral template RPLND, open or robot assisted. The outcome measures included surgical complications as per Clavien-Dindo, and Kaplan-Meier survival estimates for 24-mo progression-free survival (PFS) and overall survival (OS).

Key findings and limitations

In the cohort, 33 (53%) had CS I with a relapse during surveillance, six (10%) CS I with a relapse following adjuvant chemotherapy, and 23 (37%) initial CS IIA/B. Metastatic seminoma was verified in 58 patients (94%) with a median largest diameter of 18 mm (interquartile range [IQR] 13-24). Robot-assisted RPLND was performed in 40 patients (65%). Clavien-Dindo III complications were observed in three patients (5%); no grade ≥IV complications occurred. Eighteen patients (29%) received adjuvant chemotherapy after surgery. The median follow-up was 23 mo (IQR 16-30), and recurrence occurred in six patients (10%) after a median of 8 mo (IQR 4-14). PFS was 90% (95% confidence interval: 0.86-1) and OS was 100% at 24 mo.

Conclusions and clinical implications

RPLND as primary treatment is an option for selected low-stage seminomas with a limited burden of disease, showing low complications and low relapse rates, with the potential to reduce long-term morbidity.

Patient summary

In seminoma patients with limited metastatic spread, surgery is a treatment option offering an alternative to chemotherapy or radiation. This paper covers the first 62 patients operated in Norway and Sweden.

Evaluation of a miRNA-371a-3p Assay for Predicting Final Histopathology in Patients Undergoing Primary Nerve-sparing Retroperitoneal Lymphadenectomy for Stage IIA/B Seminoma or Nonseminoma

Patients with marker-negative clinical stage IIA/B seminoma or nonseminoma represent a therapeutic challenge, as 20-30% might harbor nonmalignant histologies. MicroRNA 371a-3p (miR371) may represent a biomarker with diagnostic and predictive properties in testicular germ cell tumors (TGCTs). We evaluated the predictive accuracy of this biomarker in identifying the presence or absence of lymph node metastases (LNMs) in clinical stage IIA/B TGCT. In a cohort of 24 consecutive patients with marker-negative clinical stage IIA/B TGCT (n = 15 seminoma, n = 9 nonseminoma) serum miR371 was assessed 1 d before nerve-sparing retroperitoneal lymphadenectomy. Histology revealed metastatic TGCT in 22/24 patients (91.7%), with positive miR371a findings for 20 of these 22 patients with metastases (90.9%). Histology revealed no malignancy in one patient and lymphoma in another, both of whom had negative miR371a findings. One additional patient with pure teratoma and one with a microscopic seminomatous LNM had false-negative miR371a findings. The miR371 assay had sensitivity of 90.9% and specificity of 50%. The positive predictive value was 100.0% and the negative predictive value was 75.0%. According to the data available, miR371a represents a highly reliable, personalized tumor marker for predicting the presence of low-volume retroperitoneal LNMs in marker-negative TGCT. miR371 has potential for inclusion in the diagnostic armamentarium for men with equivocal lymph nodes to facilitate avoidance of unnecessary treatment and the associated toxicity. PATIENT SUMMARY: Our study demonstrates that blood tests for the biomarker miR371 are highly reliable in predicting the presence of lymph node metastases in patients with stage IIA/B testicular cancer. For patients with equivocal findings, use of this test may help in avoiding unnecessary treatment.

Initial surveillance in men with marker negative clinical stage IIA non-seminomatous germ cell tumours

OBJECTIVES

To assess whether extended surveillance with repeated computed tomography (CT) scans for patients with clinical stage IIA (CS IIA; <2 cm abdominal node involvement) and negative markers (Mk-) non-seminomatous germ cell tumours (NSGCTs) can identify those with true CS I. To assess the rate of benign lymph nodes, teratoma, and viable cancer in retroperitoneal lymph node dissection (RPLND) histopathology for patients with CS IIA Mk- NSGCT.

PATIENTS AND METHODS

Observational prospective population-based study of patients diagnosed 2008-2019 with CS IIA Mk- NSGCT in the Swedish and Norwegian Testicular Cancer Group (SWENOTECA) registry. Patients were managed with surveillance, with CT scans, and tumour markers every sixth week for a maximum of 18 weeks. Patients with radiological regression were treated as CS I, if progression with chemotherapy, and remaining CS IIA Mk- disease with RPLND. The end-point was the number and percentage of patients down-staged to CS I on surveillance and rate of RPLND histopathology presented as benign, teratoma, or viable cancer.

RESULTS

Overall, 126 patients with CS IIA Mk- NSGCT were included but 41 received therapy upfront. After surveillance for a median (range) of 6 (6-18) weeks, 23/85 (27%) patients were in true CS I and four (5%) progressed. Of the remaining 58 patients with lasting CS IIA Mk- NSGCT, 16 received chemotherapy and 42 underwent RPLND. The RPLND histopathology revealed benign lymph nodes in 11 (26%), teratoma in two (6%), and viable cancer in 29 (70%) patients.

CONCLUSIONS

Surveillance with repeated CT scans can identify patients in true CS I, thus avoiding overtreatment. The RPLND histopathology in patients with CS IIA Mk- NSGCT had a high rate of cancer and a low rate of teratoma.

Serum Levels of MicroRNA-371a-3p for Predicting the Histology of Postchemotherapy Residual Masses of Germ Cell Tumours

BACKGROUND AND OBJECTIVE

Serum levels of microRNA-371a-3p (M371) represent a novel and sensitive biomarker of germ cell tumours (GCTs). This study analysed the utility of M371 to identify viable cancer (VC) in postchemotherapy (pc) residual masses with the underlying goal of avoiding overtreatment.

METHODS

A multicentric, prospective diagnostic study was conducted in 180 GCT patients undergoing pc resection of residual masses. A correlation of M371 measurement results with the histological presence of VC in masses was found. A receiver operating characteristic analysis was performed for exploring the performance characteristics of the test.

KEY FINDINGS AND LIMITATIONS

The sensitivity was found to be 68.9%, specificity 99.3%, area under the curve 0.813, positive predictive value 0.969, and negative predictive value 0.905; sensitivity is significantly associated with the percentage of VC in the mass. In specimens with ≤10% VC, there were 33.3% elevated M371 levels as opposed to 85.7% in specimens with >50% VC. Teratoma and somatic-type malignancy do not express M371. A lack of a central pathological review is a limitation.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The M371 test can identify 68.9% of patients with VC in pc masses. However, cases with <10% VC in the mass may escape detection. Teratoma does not express M371. The test alone cannot correctly identify patients requiring pc surgery, but it may be a tool for scheduling the extent of surgery.

PATIENT SUMMARY

The microRNA-371a-3p (M371) test can identify about two-thirds of patients with viable cancer in residual metastatic masses following chemotherapy for germ cell tumours. Only masses with high percentages of viable cancer cells can be identified, and the histological subtype teratoma remains undetected with the test.

Detection of Recurrence through microRNA-371a-3p Serum Levels in a Follow-up of Stage I Testicular Germ Cell Tumors in the DRKS-00019223 Study

PURPOSE

Surveillance of clinical stage I (CSI) testicular germ cell tumors (GCT) is hampered by low sensitivity and specificity of current biomarkers for detecting relapses. This study evaluated if serum levels of microRNA371a-3p (M371 test) can: (i) Accurately detect relapses, (ii) detect relapses earlier than conventional technology, and (iii) if elevated postoperative M371 levels may predict relapse.

EXPERIMENTAL DESIGN

In a multicentric setting, 258 patients with testicular CSI GCT were prospectively followed by surveillance for a median time of 18 months with serial measurements of serum M371 levels, in addition to standard diagnostic techniques. Diagnostic characteristics of M371 for detecting relapses were calculated using ROC curve analysis.

RESULTS

Thirty-nine patients recurred (15.1%), all with elevated M371 levels; eight without relapse had elevations, too. The test revealed the following characteristics: area under the ROC curve of 0.993, sensitivity 100%, specificity 96.3%, positive predictive value 83%, negative predictive value 100%. Earlier relapse detection with the test was found in 28%, with non-significant median time gain to diagnosis. Postoperative M371 levels did not predict future relapse.

CONCLUSIONS

The sensitivity and specificity of the M371 test for detecting relapses in CSI GCTs are much superior to those of conventional diagnostics. However, post-orchiectomy M371 levels are not predictive of relapse, and there is no significant earlier relapse detection with the test. In all, there is clear evidence for the utility of the M371 test for relapse detection suggesting it may soon be ready for implementation into routine follow-up schedules for patients with testicular GCT.

MicroRNAs for detecting occult genitourinary cancer

PURPOSE OF REVIEW

Genitourinary (GU) malignancies are a real burden in global health worldwide. Each model has its own clinical challenges, and the early screening and/or detection of occult cancer in follow-up is transversal to all of them. MicroRNAs (miRNAs) have been proposed as minimally invasive liquid biopsy cancer biomarkers, due to their stability and low degradation.

RECENT FINDINGS

The different GU tumor models are in different stages concerning miRNAs as biomarkers for cancer detection. Testicular germ cell tumors (TGCTs) already have a specific defined target, miR-371a-3p, that has shown high sensitivity and specificity in different clinical settings, and is now in final stages of preanalytical testing before entering the clinic. The other GU malignancies are in a different stage, with many liquid biopsy studies (both in urine and plasma/serum) being currently performed, but there is not an agreeable miRNA or set of miRNAs that is ready to follow the footsteps of miR-371a-3p in TGCTs.

SUMMARY

Further studies with proper molecular characterization of miRNA profiles of GU malignancies and standardization of sampling, biobanking and formal analysis may aid in the advance and choosing of specific target sets to be used for occult cancer detection.

Molecular Biomarkers With Potential Clinical Application in Testicular Cancer

Testicular germ cell tumors (TGCTs) and sex cord-stromal tumors (SCSTs) are the most common testicular neoplasms. The morphologic spectrum of such tumors is wide, with several histologic subtypes within each group. Testicular tumors often represent a diagnostic challenge, requiring proper identification of their biologic potential for accurate risk stratification and selection of therapy. In the era of precision medicine, molecular biomarkers are increasingly assuming a critical role in the management of patients with cancer. Given the overall rarity of certain types of testicular neoplasms, progress in biomarker research has been relatively slow. However, in recent years, we have witnessed a multitude of important contributions, including both tissue-based and liquid biopsy biomarkers, stemming from important discoveries of tumor pathobiology, accurate histopathological analysis, multi-institutional studies, and genome-wide molecular analyses of specific tumor subtypes. In this review, we provide an overview of the progress in molecular biomarkers of TGCTs and SCSTs, focusing on those with greatest potential for clinical application. In TGCTs, developmental biology has been the key to understanding these tumors and identifying clinically useful biomarkers (from classical serum tumor markers to pluripotency factors and circulating microRNAs of the 371-373 cluster). For SCSTs, studies have focused on tissue biomarkers only, and genome-wide investigations have recently contributed to a better understanding of rare phenotypes and the aggressive biological behavior of some tumors within this nosologic category. Several new biomarkers are moving toward clinical implementation in this field. Therefore, the practicing pathologist should be aware of their strengths and limitations in order to utilize them properly and maximize their clinical benefits.

MicroRNA-371a-3p-The Novel Serum Biomarker in Testicular Germ Cell Tumors

INTRODUCTION

Testicular germ cell tumors (TGCTs) are a paradigm for the use of serum tumor markers in clinical management. However, conventional markers such as alpha-fetoprotein (AFP), beta-human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH) have quite limited sensitivities and specificities. Within the last decade, the microRNA-371a-3p (miR371) emerged as a possible new biomarker with promising features.

AREAS COVERED

This review covers the typical features as well as possible clinical applications of miR371 in TGCT patients, such as initial diagnosis, therapy monitoring, and follow-up. Additionally, technical issues are discussed.

EXPERT OPINION

With a sensitivity of around 90% and specificity >90%, miR371 clearly outperforms the classical serum tumor markers in TGCTs. The unique features of the test involve the potential of modifying recent standards of care in TGCT. In particular, miR371 is expected to aid clinical decision-making in scenarios such as discriminating small testicular TGCT masses from benign ones prior to surgery, assessing equivocal lymphadenopathies, and monitoring chemotherapy results. Likewise, it is expected to make follow-up easier by reducing the intensity of examinations and by sparing imaging procedures. Overall, the data presently available are promising, but further prospective studies are required before the test can be implemented in standard clinical care.

Testicular neoplasms: the interrelationships of serum levels of microRNA-371a-3p (M371) and classical tumor markers with histology, clinical staging, and age-a statistical analysis

PURPOSE

In testicular neoplasms, the interrelationship of elevations of the novel serum tumor marker microRNA-371a-3p (M371) and traditional markers with other clinical features is still incompletely understood. The present study evaluated marker expression rates in relation to various other clinical parameters.

METHODS

The following data were retrospectively registered from 641 consecutive patients with testicular neoplasms: histology, such as seminoma (n = 365), nonseminoma (n = 179), benign tumor (n = 79), other malignant tumor (n = 18); patients age (years); clinical stage (CS1, CS2a/b, CS2c, CS3); and preoperative elevation of beta HCG, AFP, LDH, M371 (yes/no). Descriptive statistical methods were employed with comparisons of various subgroups to disclose associations of marker expression rates with age, histology and CS, and of age with histology.

RESULTS

The histologic subgroups revealed significantly different expression rates of tumor markers. M371 performed best with expression rates of 82.69% and 93.58% in seminoma and in nonseminoma, respectively. In germ cell tumors, all markers had significantly higher expression rates in metastasized stages than in localized disease. All markers except LDH have significantly higher expression rates in younger than in older patients. Nonseminoma is most prevalent in the youngest age category, seminoma predominates in patients > 40 years, other malignancies were restricted to patients > 50 years.

CONCLUSION

The study documented significant associations of serum marker expression rates with histology, age and clinical staging, with highest rates in nonseminomas, young age and advanced clinical stages. M371 showed significantly higher expression rates than other markers suggesting its superior clinical usefulness.

Refining the serum miR-371a-3p test for viable germ cell tumor detection

Circulating miR-371a-3p has excellent performance in the detection of viable (non-teratoma) germ cell tumor (GCT) pre-orchiectomy; however, its ability to detect occult disease is understudied. To refine the serum miR-371a-3p assay in the minimal residual disease setting we compared performance of raw (Cq) and normalized (∆Cq, RQ) values from prior assays, and validated interlaboratory concordance by aliquot swapping. Revised assay performance was determined in a cohort of 32 patients suspected of occult retroperitoneal disease. Assay superiority was determined by comparing resulting receiver-operator characteristic (ROC) curves using the Delong method. Pairwise t-tests were used to test for interlaboratory concordance. Performance was comparable when thresholding based on raw Cq vs. normalized values. Interlaboratory concordance of miR-371a-3p was high, but reference genes miR-30b-5p and cel-miR-39-3p were discordant. Introduction of an indeterminate range of Cq 28-35 with a repeat run for any indeterminate improved assay accuracy from 0.84 to 0.92 in a group of patients suspected of occult GCT. We recommend that serum miR-371a-3p test protocols are updated to (a) utilize threshold-based approaches using raw Cq values, (b) continue to include an endogenous (e.g., miR-30b-5p) and exogenous non-human spike-in (e.g., cel-miR-39-3p) microRNA for quality control, and (c) to re-run any sample with an indeterminate result.

Refining the serum miR-371a-3p test for viable germ cell tumor detection: identification and definition of an indeterminate range

Circulating miR-371a-3p has excellent performance in the detection of viable (non-teratoma) GCT pre-orchiectomy; however, its ability to detect occult disease is understudied. To refine the serum miR-371a-3p assay in the minimal residual disease setting we compared performance of raw (Cq) and normalized (∆Cq, RQ) values from prior assays, and validated interlaboratory concordance by aliquot swapping. Revised assay performance was determined in a cohort of 32 patients suspected of occult retroperitoneal disease. Assay superiority was determined by comparing resulting receiver-operator characteristic (ROC) curves using the Delong method. Pairwise t-tests were used to test for interlaboratory concordance. Performance was comparable when thresholding based on raw Cq vs. normalized values. Interlaboratory concordance of miR-371a-3p was high, but reference genes miR-30b-5p and cel-miR-39-3p were discordant. Introduction of an indeterminate range of Cq 28-35 with a repeat run for any indeterminate improved assay accuracy from 0.84 to 0.92 in a group of patients suspected of occult GCT. We recommend that serum miR-371a-3p test protocols are updated to a) utilize threshold-based approaches using raw Cq values, b) continue to include an endogenous (e.g., miR-30b-5p) and exogenous non-human spike-in (e.g., cel-miR-39-3p) microRNA for quality control, and c) to re-run any sample with an indeterminate result.

Impact of differing methodologies for serum miRNA-371a-3p assessment in stage I testicular germ cell cancer recurrence

Introduction

Current evidence shows that serum miR-371a-3p can identify disease recurrence in testicular germ cell tumour (TGCT) patients and correlates with tumour load. Despite convincing evidence showing the advantages of including miR-371a-3p testing to complement and overcome the classical serum tumour markers limitations, the successful introduction of a serum miRNA based test into clinical practice has been impeded by a lack of consensus regarding optimal methodologies and lack of a universal protocol and thresholds. Herein, we investigate two quantitative real-time PCR (qRT-PCR) based pipelines in detecting disease recurrence in stage I TGCT patients under active surveillance, and compare the sensitivity and specificity for each method.

Methods

Sequential serum samples collected from 33 stage I TGCT patients undergoing active surveillance were analysed for miR-371a-3p via qRT-PCR with and without an amplification step included.

Results

Using a pre-amplified protocol, all known recurrences were detected via elevated miR-371a-3p expression, while without pre-amplification, we failed to detect recurrence in 3/10 known recurrence patients. For pre-amplified analysis, sensitivity and specificity was 90% and 94.4% respectively. Without amplification, sensitivity dropped to 60%, but exhibited 100% specificity.

Discussion

We conclude that incorporating pre-amplification increases sensitivity of miR-371a-3p detection, but produces more false positive results. The ideal protocol for quantification of miR-371a-3p still needs to be determined. TGCT patients undergoing active surveillance may benefit from serum miR-371a-3p quantification with earlier detection of recurrences compared to current standard methods. However, larger cross-institutional studies where samples are processed and data is analysed in a standardised manner are required prior to its routine clinical implementation.

cfDNA methylation in liquid biopsies as potential testicular seminoma biomarker

Background: Seminoma is a testicular tumor type, routinely diagnosed after orchidectomy. As cfDNA represents a source of minimally invasive seminoma patient management, this study aimed to investigate whether cfDNA methylation of six genes from liquid biopsies, have potential as novel seminoma biomarkers. Materials & methods: cfDNA methylation from liquid biopsies was assessed by pyrosequencing and compared with healthy volunteers' samples. Results: Detailed analysis revealed specific CpGs as possible seminoma biomarkers, but receiver operating characteristic curve analysis showed modest diagnostic performance. In an analysis of panels of statistically significant CpGs, two DNA methylation panels emerged as potential seminoma screening panels, one in blood CpG8/CpG9/CpG10 (KITLG) and the other in seminal plasma CpG1(MAGEC2)/CpG1(OCT3/4). Conclusion: The presented data promote the development of liquid biopsy epigenetic biomarkers in the screening of seminoma patients.

Advances in diagnosis and treatment of testicular cancer

Testicular cancer is a curable cancer. The success of physicians in curing the disease is underpinned by multidisciplinary advances. Cisplatin-based combination chemotherapy and the refinement of post-chemotherapy surgical procedures and diagnostic strategies have greatly improved long term survival in most patients. Despite such excellent outcomes, several controversial dilemmas exist in the approaches to clinical stage I disease, salvage chemotherapy, post-chemotherapy surgical procedures, and implementing innovative imaging studies. Relapse after salvage chemotherapy has a poor prognosis and the optimal treatment is not apparent. Recent research has provided insight into the molecular mechanisms underlying cisplatin resistance. Phase 2 studies with targeted agents have failed to show adequate efficacy; however, our understanding of cisplatin resistant disease is rapidly expanding. This review summarizes recent advances and discusses relevant issues in the biology and management of testicular cancer.

Testicular Neoplasms: Primary Tumour Size Is Closely Interrelated with Histology, Clinical Staging, and Tumour Marker Expression Rates-A Comprehensive Statistical Analysis

The role of primary tumour size (TS) in the clinical course of testicular tumours is incompletely understood. We retrospectively evaluated 641 consecutive patients with testicular neoplasms with regard to TS, histology, clinical stage (CS), serum tumour marker (STM) expression and patient age using descriptive statistical methods. TS ≤ 10 mm was encountered in 13.6% of cases. Median TS of 10 mm, 30 mm, 35 mm, and 53 mm were found in benign tumours, seminomas, nonseminomas, and other malignant tumours, respectively. In cases with TS ≤ 10 mm, 50.6% had benign tumours. Upon receiver operating characteristics analysis, TS of > 16 mm revealed 81.5% sensitivity and 81.0% specificity for detecting malignancy. In subcentimeter germ cell tumours (GCTs), 97.7% of cases had CS1, and CS1 frequency dropped with increasing TS. Expression rates of all STMs significantly increased with TS. MicroRNA-371a-3p (M371) serum levels had higher expression rates than classical STMs, with a rate of 44.1% in subcentimeter GCTs. In all, TS is a biologically relevant factor owing to its significant associations with CS, STM expression rates and histology. Importantly, 50% of subcentimeter testicular neoplasms are of benign nature, and M371 outperforms the classical markers even in subcentimeter tumours.

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

BACKGROUND

Specific cancer types face specific clinical management challenges. Owing to their stability, robustness and fast, easy, and cost-effective detection, microRNAs (miRNAs) are attractive candidate biomarkers to the clinic.

OBJECTIVES

Based on a comprehensive review of the relevant literature in the field, we explore the potential of miRNAs as biomarkers to answer relevant clinical dilemmas inherent to cancers of the male reproductive tract (prostate (PCa), testis (TGCTs) and penis (PeCa)) and identify some of the challenges/limitations hampering their widely application.

RESULTS AND DISCUSSION

We conclude that the use of miRNAs as biomarkers is at different stages for these distinct cancer types. While for TGCTs, miRNA-371a-3p is universally accepted to fill in important clinicals gaps and is moving fast towards clinical implementation, for PCa almost no overlap of miRNAs exists between studies, denoting the absence of a consistent miRNA biomarker, and for PeCa the field of miRNAs has just recently started, with only a few studies attempting to explore their clinical usefulness.

CONCLUSION

Technological advances influencing miRNA detection and quantification will be instrumental to continue to move forward with implementation of miRNAs in the clinic as biomarkers for non-invasive diagnosis, risk stratification, treatment monitoring and follow-up. This article is protected by copyright. All rights reserved.

DigiMir Test: Establishing a Novel Pipeline for MiR-371a Quantification Using Droplet Digital PCR in Liquid Biopsies From Testicular Germ Cell Tumor Patients

Testicular germ cell tumors (TGCTs) are the most common cancers in young-adult male patients aged between 15 and 39 years. Hsa-miR-371a-3p is currently the most reliable biomarker for diagnosis and monitoring of these patients non-invasively in liquid biopsies, and it is destined to be introduced in the clinic due to improved performance compared to the classical serum tumor markers available. Current studies have focused on real-time quantitative PCR (RT-qPCR) protocols for its determination; still, some challenges remain, since these protocols often require preamplification steps (costly and time-consuming), and report relative levels normalized to a housekeeping microRNA, not always performed the same way. Droplet digital PCR (ddPCR) shows the promise to overcome these challenges, skipping normalization and preamplifications, but has hardly been explored in the field of TGCTs. In this work, we provide a report of a ddPCR-based pipeline for the quantification of hsa-miR-371a-3p (the DigiMir pipeline) and compare it with two RT-qPCR protocols. A total of 107 plasma samples were investigated in the validation setting. The DigiMir pipeline detected TGCTs in a manner representative of tumor burden, with a sensitivity and specificity of 94% and 100%, respectively, outperforming the combined sensitivity of all three classical serum tumor markers (61.5%). Therefore, in this proof-of-concept investigation, we have shown that the DigiMir pipeline constitutes a new promising methodology to accurately report hsa-miR-371a-3p in the clinical setting.

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

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.