Expression Patterns of MOTS-c in Adrenal Tumors: Results from a Preliminary Study

Abstract

Adrenal tumors, such as adrenocortical carcinoma (ACC), adrenocortical adenoma (ACA), and pheochromocytoma (PCC) are complex diseases with unclear causes and treatments. Mitochondria and mitochondrial-derived peptides (MDPs) are crucial for cancer cell survival. The primary aim of this study was to analyze samples from different adrenal diseases, adrenocortical carcinoma, adrenocortical adenoma, and pheochromocytoma, and compare them with normal adrenal tissue to determine whether the expression levels of the mitochondrial open reading frame of the 12S rRNA type-c (MOTS-c) gene and protein vary between different types of adrenal tumors compared to healthy controls using qPCR, ELISA, and IHC methods. Results showed decreased MOTS-c mRNA expression in all adrenal tumors compared to controls, while serum MOTS-c protein levels increased in ACA and PCC but not in ACC. The local distribution of MOTS-c protein in adrenal tissue was reduced in all tumors. Notably, MOTS-c protein expression declined with ACC progression (stages III and IV) but was unrelated to patient age or sex. Tumor size and testosterone levels positively correlated with MOTS-c mRNA but negatively with serum MOTS-c protein. Additionally, serum MOTS-c protein correlated positively with glucose, total cholesterol, HDL, LDL, and SHGB levels. These findings suggest disrupted expression of MOTS-c in the spectrum of adrenal diseases, which might be caused by mechanisms involving increased mitochondrial dysfunction and structural changes in the tissue associated with disease progression. This study provides a detailed examination of MOTS-c mRNA and protein in adrenal tumors, indicating the potential role of MDPs in tumor biology and progression.

Keywords: MOTS-c; adrenal tumors; mitochondria homeostasis.

Figure 1

Adrenal expression of MOTS-c mRNA and correlations with demographic and laboratory features of patients with adrenal disease compared to heathy controls. MOTS-c gene expression is down-regulated in the spectrum of adrenal disease in comparison to healthy controls (normal adrenal tissue) (A). Correlations of MOTS-c mRNA expression with all clinical parameters of the patients (B), with the most significant and impactful correlations highlighted (C). Comparisons between the groups were performed using Kruskal–Wallis followed by the Dunn post hoc test. Data points are presented as dots on the corresponding boxplot. The differences between the groups are shown as letter annotations. Different letters indicate significant (p < 0.05) differences between the compared groups. Each boxplot indicates median and interquartile range (IQR) values. Correlation analysis was performed using Pearson correlation. Blue color indicates positive correlation while red indicates a negative correlation, intensity of the color reflects the strength of the correlation (R value). Dashes (“-”) signify missing patient data or when the number of patients with corresponding data is fewer than five in the respective group. p-value < 0.05 was considered statistically significant. * p < 0.05, ** p < 0.01.

Figure 2

Serum expression of MOTS-c protein and correlations with demographic and laboratory features of patients with adrenal disease compared to heathy controls. MOTS-c protein expression is up-regulated in the spectrum of adrenal disease in comparison to healthy controls (normal adrenal tissue) (A). Correlations of MOTS-c protein expression with all clinical parameters of the patients (B), with the most significant and impactful correlations highlighted (C). Comparisons between the groups were performed using Kruskal–Wallis followed by Dunn post hoc test. All groups are presented as boxplots indicating median and interquartile range (IQR) values. Each data point is displayed as a dot on the corresponding boxplot. The differences between the groups are shown as letter annotations. Different letters indicate significant (p < 0.05) differences between the compared groups. Correlation analysis was performed using Pearson correlation. Blue color indicates positive correlation and red indicates negative correlation, while intensity of the color reflects the strength of the correlation (R value). Dashes (“-”) signify missing patient data or when the number of patients with corresponding data is fewer than five in the respective group. p-value < 0.05 was considered statistically significant. * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 3

Adrenal expression of MOTS-c protein and correlations with demographic features of patients with adrenal disease compared to heathy controls. MOTS-c protein expression is down-regulated in the spectrum of adrenal disease in comparison to healthy controls (normal adrenal tissue) (A). MOTS-c protein expression is reduced within ACC progression (B). Correlations of MOTS-c protein expression with patient age (C) and gender (D) in all analyzed groups. The potential of MOTS-c protein as a diagnostic biomarker in distinguishing normal adrenal tissue from ACC (E), and ACA from ACC (F) was investigated. Comparisons between >2 groups were performed using Kruskal–Wallis followed by Dunn post hoc test. The differences between the groups are shown as letter annotations, where different letters indicate significant differences (p < 0.05) between the compared groups and presented as boxplots indicating median and interquartile range (IQR) values. Densitometric data from individual patients are displayed as dots on the corresponding graph. Correlation analysis was performed using Pearson correlation. Statistical analysis for comparison between 2 groups was performed using Mann–Whitney U test. The sensitivity, specificity, and area under curve (AUC) values are shown in both graphs of the ROC analysis.

Figure 4

Representative images of MOTS-c protein immunohistochemical reactivity in the spectrum of adrenal disease on TMA slide, including stages II–IV ACC. Brown staining, pointed out by red arrows, indicates typical cytoplasmatic localization of MOTS-c protein with hematoxylin counterstaining to distinguish cell nuclei. Original magnifications 400×.