The differential expression of micro-RNAs 21, 200c, 204, 205, and 211 in benign, dysplastic and malignant melanocytic lesions and critical evaluation of their role as diagnostic biomarkers

Katherine Quiohilag,Anca Oniscu,Peter Caie,David Harrison,Thomas Brenn

doi:10.1007/s00428-020-02817-5

Abstract

Overlapping histological features between benign and malignant lesions and a lack of firm diagnostic criteria for malignancy result in high rates of inter-observer variation in the diagnosis of melanocytic lesions. We aimed to investigate the differential expression of five miRNAs (21, 200c, 204, 205, and 211) in benign naevi (n = 42), dysplastic naevi (n = 41), melanoma in situ (n = 42), and melanoma (n = 42) and evaluate their potential as diagnostic biomarkers of melanocytic lesions. Real-time PCR showed differential miRNA expression profiles between benign naevi; dysplastic naevi and melanoma in situ; and invasive melanoma. We applied a random forest machine learning algorithm to classify cases based on their miRNA expression profiles, which resulted in a ROC curve analysis of 0.99 for malignant melanoma and greater than 0.9 for all other groups. This indicates an overall very high accuracy of our panel of miRNAs as a diagnostic biomarker of benign, dysplastic, and malignant melanocytic lesions. However, the impact of variable lesion percentage and spatial expression patterns of miRNAs on these real-time PCR results was also considered. In situ hybridisation confirmed the expression of miRNA 21 and 211 in melanocytes, while demonstrating expression of miRNA 205 only in keratinocytes, thus calling into question its value as a biomarker of melanocytic lesions. In conclusion, we have validated some miRNAs, including miRNA 21 and 211, as potential diagnostic biomarkers of benign, dysplastic, and malignant melanocytic lesions. However, we also highlight the crucial importance of considering tissue morphology and spatial expression patterns when using molecular techniques for the discovery and validation of new biomarkers.

Highlights

Malignant melanoma has seen a rapid increase in incidence in the last several decades, having risen by almost 50% in the lastElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.The Arnie Charbonneau Cancer Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada decade alone, and is the fifth most common cancer in the UK [1]
Given the significant degree of diagnostic uncertainly generated by these lesions, we aimed to investigate the role of a panel of five miRNAs as a potential diagnostic biomarker of benign naevi, dysplastic naevi, melanoma in situ, and invasive melanoma
For miRNA 211, expression was significantly reduced in melanoma in situ compared with that in dysplastic naevi (p < 0.001), though owing to a wide variation in expression in the melanoma cohort, neither of these was significantly different from melanoma

Summary

Introduction

The current gold standard method for the diagnosis of melanocytic lesions is histological examination of tissue by pathologists. This has been described as ‘one of the most challenging and controversial fields in diagnostic histopathology’ [2] due to overlapping histological features between benign and malignant lesions [3] and lack of firm diagnostic criteria for malignancy. They have overlapping features with both benign naevi at the mild end of the spectrum and melanoma at the severe end. A reliable and objective molecular marker to aid pathologists’ visual assessment of benign naevi, dysplastic naevi, and melanoma would be of great clinical value

Objectives

Results

Conclusion