Cytotoxic responses and cell death mechanisms in adrenocortical carcinoma: Insights into mitotane and cisplatin treatment

Adrenocortical carcinoma (ACC) is a rare and aggressive malignancy with limited treatment options, particularly for advanced or metastatic stages. Current therapies primarily involve mitotane, often in combination with cytotoxic agents like cisplatin, yet the mechanisms by which these agents induce cell death in ACC remain poorly understood. A major challenge in elucidating these mechanisms is the reliance on monolayer cultures, which fail to replicate the complex tumour microenvironment (TME) of ACC. To address this, we present a novel three dimensional (3D) cell culture model of ACC using H295R, HAC15, and MUC-1 cell lines cultured in type I collagen matrices. This model more accurately mimics the native TME of ACC compared to 2D cultures and is designed to enhance the understanding of cytotoxic responses and improve therapeutic efficacy. This thesis demonstrate that this 3D ACC model is viable, steroidogenic, and exhibits tumour like features, including central necrosis. Importantly, resistance to mitotane was observed in the 3D culture system compared to monolayer cultures, with varying degrees of resistance to cisplatin treatment. HAC15 and MUC-1 cells exhibited greater mitotane resistance than H295R cells, and HAC15 cells also displayed resistance to cisplatin. Mitotane treatment in H295R cells predominantly induced classical caspase-3-mediated apoptosis, whereas resistant HAC15 and MUC-1 cells underwent non-apoptotic cell death involving necrosis and necroptosis. This thesis highlights the heterogeneity of ACC cell responses to treatment and underscores the limitations of apoptosis-based therapies in mitotane resistant cells. The 3D model developed herein represents a significant advancement in preclinical ACC research, providing a more physiologically relevant platform for studying ACC biology and evaluating new therapeutic strategies. By revealing the complex nature of drug-induced cell death in ACC, this work advocates for the inclusion of alternative regulated cell death pathways, such as necroptosis, in therapeutic approaches aimed at improving treatment outcomes in this aggressive malignancy.

Publisher

University of Galway

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CC BY-NC-ND

cbn

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University of Galway Theses (PhD Theses)