The Efficacy of Mitotane in Human Primary Adrenocortical Carcinoma Cultures

Abstract

Context Patients with adrenocortical carcinoma (ACC) often fail mitotane treatment and deal with severe toxicity, marking the relevance of predictive parameters for treatment outcome. Objective Determine the effects of mitotane in primary ACC cultures, and correlate sensitivity with patient and tumor characteristics. Methods In 32 primary ACC cultures, the effects of mitotane on cell growth and cortisol production were determined. RRM1, SOAT1, and CYP2W1 expression were assessed using reverse transcription-polymerase chain reaction and immunohistochemistry. Results The median percentage cell amount inhibition in primary ACC cultures at 50 µM mitotane was 57%. Seven patients were classified as nonresponders, 14 as partial responders, and 11 as responders. The mean median effective concentration (EC50) value of mitotane for inhibition of cell amount in responders was 14.2 µM (95% CI, 11.3–17.9), in partial responders 41.6 µM (95% CI, 33.5–51.8), and could not be calculated in nonresponders. The percentage cortisol-producing ACC was 14%, 43%, and 73% for nonresponders, partial responders, and responders (P = 0.068). Mitotane inhibited cortisol production with a mean EC50 of 1.4 µM (95% CI, 0.9–2.1), which was considerably lower than the EC50 on cell growth. RRM1, SOAT1, and CYP2W1 expression levels were not predictive for mitotane sensitivity in vitro. Conclusion Direct antitumor effects of mitotane on human primary ACC cultures are highly variable between patients, reflecting heterogeneous responses in patients. Cortisol was inhibited at lower concentrations, compared with its effect on cell amount. Cortisol secretion by ACC might be associated with enhanced mitotane sensitivity due to increased direct antitumor effects of mitotane.

Effects of Germline CYP2W1*6 and CYP2B6*6 Single Nucleotide Polymorphisms on Mitotane Treatment in Adrenocortical Carcinoma: A Multicenter ENSAT Study

“…For that reason, the achievement of the target range should be considered as the goal of the mitotane treatment [9]. Currently, no one of the proposed biomarkers, which were previously described to predict response and attainment of therapeutic plasma concentrations [14][15][16][17], is used in clinical practice since they have not been validated. In this multicenter study, we evaluated SNPs of CYP2W1 and CYP2B6 as potential predictive markers of response to mitotane in a large cohort of patients treated with mitotane monotherapy as first pharmacological therapy either after radical resection (group A) or in not completely resectable, recurrent or advanced ACC (group B).…”

“…We previously showed that ACC patients having high CYP2W1 immunostaining at tumor level present a better response to mitotane therapy in comparison to those with low CYP2W1 staining [15]. These results were very recently confirmed in primary ACC cell culture [16]. Currently, it is unclear whether SNPs of CYP2W1 might affect the metabolic function of the enzyme [23].…”

“…So far, only few molecular markers have been proposed for predicting the response to mitotane treatment, including ribonucleotide reductase M1 (RRM1) [14] and the cytochrome P450 (CYP) 2W1 [15,16]. Moreover, single nucleotide polymorphism (SNP) of another member of the CYP superfamily, CYP2B6*6, has been proposed to correlate with mitotane plasma levels [17].…”

Recovery of Adrenal Insufficiency Is Frequent After Adjuvant Mitotane Therapy in Patients with Adrenocortical Carcinoma

“…Boulate et al recently demonstrated a potentiating effect of rosuvastatin on mitotane cell toxicity in vitro [21]. Van Koetsveld et al showed that mitotane could have an increased in vitro sensitivity on cortisol-producing ACC tumors [13]. Cusato et al hypothesized that mitotane blood levels and dosage could be affected by body fat and seasonal variations in white and brown adipose tissue [22].…”

“…In vitro studies showed that mitotane causes interference with cholesterol metabolism and with mitochondrial activity in adrenocortical cells, which often leads to an increase in the apoptosis rate. It also reduces adrenal steroidogenesis by inhibiting key mitochondrial enzymes like CYP11B, which reduces the conversion of hormone precursors into active hormones such as cortisol [11][12][13][14]. It was also found that mitotane could potentially interfere with pituitary function by comparing adrenocorticotropic hormone (ACTH) levels between patients treated with mitotane for ACC and patients with primary adrenal insufficiency (autoimmune or post-adrenalectomy) [15].…”