CYP11B1 has no role in mitotane action and metabolism in adrenocortical carcinoma cells.

Antonina Germano,Silvia De Francia,Ida Rapa,Alfredo Berruti,Marco Volante,Massimo Terzolo,Laura Saba,Paola Perotti,Hamidreza Montazeri Aliabadi

doi:10.1371/journal.pone.0196931

Antonina Germano, Silvia De Francia + Show 7 more

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https://doi.org/10.1371/journal.pone.0196931

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Abstract

Mitotane is the reference drug for adrenocortical carcinoma (ACC) and the metabolic activation of the drug is considered as essential for its activity. The aim of this study was to assess the role of CYP11B1 on mitotane action and metabolism in H295R ACC cells to understand whether this enzyme may influence mitotane action. The simultaneous incubation with mitotane and metyrapone, an adrenolytic molecule targeting 11-beta-hydroxylase, did not influence mitotane-mediated cytotoxic effect and metabolism in H295R ACC cells. CYP11B1 silencing confirmed the lack of a significant metyrapone effect on mitotane action. The present findings do not support the view that CYP11B1 catalyzes a crucial step in the metabolic activation of mitotane and that CYP11B1 confers the adrenal specificity to mitotane.

Highlights

Adrenocortical carcinoma (ACC) is a rare and malignant endocrine tumor with a generally poor prognosis [1, 2]
Mitotane was introduced in clinical use to treat advanced ACC in the sixties [2] but its mechanism of action remains poorly understood
The concept that a metabolic transformation of mitotane is needed for its therapeutic activity is supported by the observation of a huge inter-species variation of the adrenolytic effects of the drug that parallels the different adrenal capability to transform mitotane [11, 12, 16]

Summary

Introduction

Adrenocortical carcinoma (ACC) is a rare and malignant endocrine tumor with a generally poor prognosis [1, 2]. Mitotane acts on the adrenal glands inhibiting cell growth and impairing steroidogenesis [5]. Critical steps of the inhibitory effects on steroidogenesis may occur in mitochondria possibly involving CYP11A1, a mitochondrial enzyme that catalyzes the transformation of cholesterol to pregnenolone [6]. Metabolic activation of mitotane is considered to be essential for the therapeutic effect, through transformation into two metabolites, 1,1-(o,p’-dichlorodiphenyl)-2,2 dichloroethene (o,p’-DDE) and 1,1-(o,p’-dichlorodiphenyl) acetic acid (o,p’-DDA) by α- and β-hydroxylation, respectively [8]. Mitotane is metabolized through a reactive acyl chloride thought to bind adrenal cortical bionucleophiles as well as to serve as the intermediate in the formation of o,p’DDA, probably by means of a cytochrome P450 (CYP) enzyme [9, 10]. The metabolic activation of mitotane may take place in the tumor and be dependent on either CYP11B1 or a non-

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