Preclinical evaluation of the antitumoral efficacy of Wee1 inhibitor AZD1775 in adrenocortical carcinoma

Current therapy for advanced adrenocortical carcinoma (ACC) is represented by EDP-M (etoposide, doxorubicin, cisplatin + mitotane), but its efficacy is limited and new approaches are needed. Our previous in vitro findings showed that AZD1775, an inhibitor of the G2/M checkpoint gatekeeper Wee1, reduces proliferation and increases apoptosis in ACC cell models. The compensatory upregulation of Myt1, a Wee1-redundant kinase, has been involved in the onset of AZD1775 resistance in other tumour types. Aim of this study was to investigate in vitro and in vivo the effects of AZD1775 alone or combined with EDP-M, and to explore the onset of molecular mechanisms of resistance. In vitro experiments in human ACC cell line NCI-H295R demonstrated that coincubation of AZD1775 and EDP-M exerted synergistic effects in reducing cell viability and proliferation and additive effects in inhibiting cortisol secretion. In NCI-H295R xenografts in nude mice, AZD1775 demonstrated an antitumor efficacy comparable to EDP-M, without synergistic effects. Myt1 upregulation was observed after Wee1 silencing or inhibition by AZD1775 in NCI-H295R and patient-derived ACC cells, but not in mice tumours after 22-days treatment with AZD1775 and/or EDP-M. Interestingly, Myt1 increase after AZD1775 treatment in primary ACC cells was reverted by EDP-M cotreatment. Overall, our data in in vitro and in vivo preclinical ACC models support AZD1775 as a promising ACC therapeutic option, and its combination with EDP-M as a useful strategy to enhance drug efficacy, reduce cortisol secretion, prevent drug resistance and minimize side effects by reducing the therapeutic dosage.