Association of miR-146a-5p and miR-21-5p with Prognostic Features in Melanomas

Abstract

Background: Cutaneous melanoma (CM) is one of the most lethal tumors among skin cancers and its incidence is rising worldwide. Recent data support the role of microRNAs (miRNAs) in melanoma carcinogenesis and their potential use as disease biomarkers.

Methods: We quantified the expression of miR-146a-5p and miR-21-5p in 170 formalin-fixed paraffin embedded (FFPE) samples of CM, namely 116 superficial spreading melanoma (SSM), 26 nodular melanoma (NM), and 28 lentigo maligna melanoma (LMM). We correlated miRNA expression with specific histopathologic features including Breslow thickness (BT), histological subtype, ulceration and regression status, and mitotic index.

Results: miR-146a-5p and miR-21-5p were significantly higher in NM compared to SSM and LMM. The positive correlation between miR-146a-5p and miR-21-5p expression and BT was confirmed for both miRNAs in SSM. Considering the ulceration status, we assessed that individual miR-21-5p expression was significantly higher in ulcerated CMs. The increased combined expression of the two miRNAs was strongly associated with ulceration (p = 0.0093) and higher mitotic rate (≥1/mm²) (p = 0.0005). We demonstrated that the combination of two-miRNA expression and prognostic features (BT and ulceration) can better differentiate cutaneous melanoma prognostic groups, considering overall survival and time-to-relapse clinical outcomes. Specifically, miRNA expression can further stratify prognostic groups among patients with BT ≥ 0.8 mm but without ulceration. Our findings provide further insights into the characterization of CM with specific prognostic features. The graphical abstract was created with BioRender.com.

Keywords: Breslow thickness; histopathology; melanoma; miRNA; prognosis; ulceration.

Figure 1

Association of the combined and individual miR-21-5p and miR-146a-5p expression with melanoma histotypes. Figures show the scatter plot distribution of combined miRNA expression (A) and individual miR-21-5p (B) and miR-146a-5p (C) in all cutaneous melanomas (CM) and in the three main histological subtypes, namely superficial spreading melanoma (SSM), nodular melanoma (NM), and lentigo maligna melanoma (LMM). miRNA expression was also tested in three benign nevi (BN) as a reference. Combined and individual miRNA expression is higher in NM compared to SSM and LMM.

Figure 2

Correlation of combined and individual miRNA expression with Breslow thickness (BT) in all melanomas (CM) and superficial spreading melanoma (SSM) subtype. Figures show the correlation plot of the combined and individual miRNA values and BT values from the same tumor. A significant positive correlation in all CMs (A) and SSM subtype (B) is reported (Pearson r). Simple linear regression line is shown in the graphs.

Figure 3

Association of combined and individual miR-21-5p and miR-146a-5p expression with Breslow thickness (BT). Figures show the scatter plot distribution of the combined miRNA expression (A) and individual miR-21-5p (B) and miR-146a-5p (C) in all cutaneous melanomas (CMs) grouped based on BT: CMs with BT < 0.8 mm and CMs with BT ≥ 0.8 mm. Combined and individual miRNA expression was significantly higher in CMs with BT ≥ 0.8 mm compared to CMs with BT < 0.8 mm.

Figure 4

Association of combined and individual miR-21-5p and miR-146a-5p expression with ulceration status. Figures show the scatter plot distribution of the combined miRNA expression (A) and individual miR-21-5p (B) and miR-146a-5p (C) in all cutaneous melanomas (CMs) grouped based on ulceration status: CMs without ulceration and CMs with ulceration. Combined and individual miR-21-5p expression was significantly higher in ulcerated CMs.

Figure 5

Association of combined and individual miR-21-5p and miR-146a-5p expression with mitotic rate. Figures show the scatter plot distribution of the combined miRNA expression (A) and individual miR-21-5p (B) and miR-146a-5p (C) in all cutaneous melanomas (CMs) grouped based on mitotic rate: CMs with <1 mitosis/mm² and CMs with ≥1 mitosis/mm². Combined and individual miRNA expression was higher in CMs with ≥1 mitosis/mm² compared to CMs with <1 mitosis/mm².

Figure 6

Association of combined and individual miR-21-5p and miR-146a-5p expression in lentigo maligna melanoma (LMM) based on regression status. Figures show the scatter plot distribution of the combined miRNA expression (A) and individual miR-21-5p (B) and miR-146a-5p (C) LMMs grouped based on regression status: LMMs without regression and LMMs with regression. Combined and individual miRNA expression was significantly higher in LMMs with regression.

Figure 7

Kaplan-–Meier plots for overall survival (OS) and time-to-relapse (TTR) in CM prognostic groups. (A) The plots show worse OS and TTR curves in patients with nodular melanoma (NM) histotype compared to superficial spreading melanoma (SSM) and lentigo maligna melanoma (LMM). (B) The plots show significantly worse OS and TTR curves in patients with BT ≥ 0.8 mm versus those with BT < 0.8 mm. (C) The plots show significantly worse OS and TTR curves in patients with miRNA expression ≥1.5 versus those with miRNA < 1.5. (D) The plots show significantly worse OS and TTR curves in patients with ulceration compared to patients without ulceration.

Figure 8

Kaplan–Meier plots for overall survival (OS) and time-to-relapse (TTR) in patients grouped according to miRNA expression, Breslow thickness (BT), and ulceration status. (A) The plots show significantly worse OS and TTR curves in patients with BT ≥ 0.8 mm versus those with BT < 0.8 mm. Among melanomas with BT ≥ 0.8 mm, those with miRNA expression ≥1.5 have a worse TTR compared to those with miRNA expression < 1.5. (B) Among patients with BT ≥ 0.8 mm, ulcerated melanomas have the worst prognosis in terms of OS and TTR. Among patients with BT ≥ 0.8 mm and without ulceration, a worse prognosis is showed by patients with miRNA expression ≥1.5 compared to those with miRNA expression < 1.5.