The Lack of Antitumor Effects of o,p′DDA Excludes Its Role as an Active Metabolite of Mitotane for Adrenocortical Carcinoma Treatment

Abstract

Mitotane (o,p'DDD) is the most effective treatment of advanced adrenocortical carcinoma (ACC) but its mechanism of action remains unknown. Previous studies suggested that o,p'DDA may represent the active metabolite of mitotane. We aimed at reevaluating the potential role and pharmacological effects of o,p'DDA. Functional consequences of o,p'DDA exposure were studied on proliferation, steroidogenesis, and mitochondrial respiratory chain in human H295R and SW13 adrenocortical cells. Mitotane and its metabolites were quantified using high-performance liquid chromatography combined to an ultraviolet detection in these cells treated with o,p'DDD or o,p'DDA and in human adrenal tissues. Dose-response curves up to 300 μM showed that, as opposed to o,p'DDD, o,p'DDA did not inhibit cell proliferation nor alter respiratory chain complex IV activity, gene expression nor induce mitochondrial biogenesis, oxidative stress, or apoptosis. However, whereas mitotane drastically decreased expression of genes involved in steroidogenesis, o,p'DDA slightly reduced expression of some steroidogenic enzymes and exerts weak anti-secretory effects only at high doses. While o,p'DDD concentration was significantly reduced by 40 % in H295R cell supernatants after 48 h incubation, o,p'DDA levels remained unchanged suggesting that o,p'DDA was not efficiently transported into the cells. o,p'DDA was not detected in cell homogenates or supernatants after 48 h exposure to o,p'DDD, consistent with the absence of o,p'DDA production in these models. Finally, unlike o'p'DDD, we found that o,p'DDA content was undetectable in two ACC and one normal adrenal gland of mitotane-treated patients, suggesting a lack of cellular uptake and in situ production. Our results demonstrate that o,p'DDD, but not o,p'DDA, induces functional alterations in adrenal cells.

Therapeutic drug monitoring of mitotane: Analytical assay and patient follow‐up

“…We chose to focus on mitotane as no correlation has clearly been established to date between the metabolites's concentrations and the treatment's efficacy (Hermsen et al, ; Hescot et al . , ).…”

“…techniques allowed quantification of its metabolites. We chose to focus on mitotane as no correlation has clearly been established to date between the metabolites's concentrations and the treatment's efficacy (Hermsen et al, 2011;Hescot et al, 2014). with cold ethanol followed with addition of potassium dihydrogen phosphate.…”

“…On the contrary, Hermsen et al, found no significant relationship between tumor response and o,p'-DDE plasma concentration but they suggested an additional benefit of combined o,p'-DDD and o,p'-DDA monitoring in ACC treatment (Hermsen et al, 2011). Several years later, Hescot et al (2014) reported a lack of antitumor effects for o,p'DDA which excluded its role as an active metabolite of mitotane for ACC treatment. Thereby, the only predictive factor of tumor response is mitotane (o,p'-DDD) plasma concentrations.…”

A simplified method for therapeutic drug monitoring of mitotane by gas chromatography‐electron ionization‐mass spectrometry

“…Mitotane, a key drug for the treatment of adrenal cortical carcinoma (ACC), has a narrow therapeutic window between 14 and 20 μg/mL; therefore, it is desirable to routinely perform therapeutic drug monitoring (TDM). Although several quantitative methods for enantiomers and major metabolites of mitotane have been developed (Cantillana, Lindström, Eriksson, Brandt, & Bergman, ; Inouye, Mio, & Sumino, ), the lack of antitumor effects of a major metabolite, 1,1‐( o , p '‐dichlorodiphenyl) acetic acid, was recently demonstrated (Hescot et al, ), suggesting the low importance of TDM of these compounds compared to mitotane. Therefore, a simplified and rapid quantitative method for TDM of mitotane is clinically desired, compared to those of metabolites and chiral bodies.…”

Biochemical mechanism of the o,p’-DDD effect on the adrenal cortex

“…Among the radiolabeled proteins, cytochrome P450 scc was detected by Western blotting. The hypothesis that o,p'-dichlorodiphenylacetic acid (o,p'-DDA) is the active metabolite of o,p'-DDD was tested [19] [19].…”