Mitotane enhances doxorubicin cytotoxic activity by inhibiting P-gp in human adrenocortical carcinoma cells

Abstract

Mitotane is currently employed as adjuvant therapy as well as in the medical treatment of adrenocortical carcinoma (ACC), alone or in combination with chemotherapeutic agents. It was previously demonstrated that mitotane potentiates chemotherapeutic drugs cytotoxicity in cancer cells displaying chemoresistance due to P-glycoprotein (P-gp), an efflux pump involved in cancer multidrug resistance. The majority of ACC expresses high levels of P-gp and is highly chemoresistent. The aim of our study was to explore in vitro whether mitotane, at concentrations lower than those currently reached in vivo, may sensitize ACC cells to the cytotoxic effects of doxorubicin and whether this effect is due to a direct action on P-gp. NCI-H295 and SW13 cell lines as well as 4 adrenocortical neoplasia primary cultures were treated with mitotane and doxorubicin, and cell viability was measured by MTT assay. P-gp activity was measured by calcein and P-gp-Glo assays. P-gp expression was evaluated by Western blot. We found that very low mitotane concentrations sensitize ACC cells to the cytotoxic effects of doxorubicin, depending on P-gp expression. In addition, mitotane directly inhibits P-gp detoxifying function, allowing doxorubicin cytotoxic activity. These data provide the basis for the greater efficacy of combination therapy (mitotane plus chemotherapeutic drugs) on ACC patients. Shedding light on mitotane mechanisms of action could result in an improved design of drug therapy for patients with ACC.

Measurement of Rhodamine 123 in Three‐Dimensional Organoids: A Novel Model for P‐Glycoprotein Inhibitor Screening

“…Verapamil and quinidine as the first‐generation P‐gp inhibitors were also reversibility inhibitors , whereas mitotane was the third‐generation inhibitor . In this study, both quinidine and mitotane exhibited more potent inhibition on P‐gp than verapamil, which was also consistent with the previous studies . In addition, mitotane showed the most potent inhibition on P‐gp, which may be due to its high specificity binding to P‐gp.…”

Screening of FDA-Approved Drugs for Inhibitors of Japanese Encephalitis Virus Infection

“…The CC 50 values of the hit drugs exhibited in Fig. 1B were similar to those previously published for diverse cell systems but determined using different toxicity assays (6)(7)(8)(9)(10)(11)(12)(13). Three of the hit drugs, manidipine, cilnidipine, and benidipine hydrochloride, were dihydropyridine (DHP) voltage-gated Ca 2ϩ channel (VGCC) antagonists, while pimecrolimus is an inhibitor of inflammatory cytokine secretion and nelfinavir mesylate is an HIV-1 protease blocker.…”

Outcomes of Adjuvant Mitotane after Resection of Adrenocortical Carcinoma: A 13-Institution Study by the US Adrenocortical Carcinoma Group

“…In addition, mitotane was usually given in combination with other cytotoxic chemotherapies, making it impossible to discern whether tumor response represented the effect of mitotane, chemotherapeutic agents, or the combination thereof. 25 As such, based on these studies in advanced disease, administration of mitotane as adjuvant therapy for resected disease is debatable.…”