Abstract 265: Inhibiting proteasome in extracellular matrix (ECM) detached cells promotes anoikis

Abstract

Abstract The underlying mediators for altered cell-extracellular matrix (ECM) communication in tumors remain to be understood and are likely to be multifactorial. Detached cells from the ECM are often cleared by a death process called ‘anoikis’. Anoikis is critical for health and homeostasis maintenance. However, aggressive cancer cells acquire anoikis resistance to promote invasion and metastasis in new sites. We previously identified metabolic reprogramming and upregulation of Vacuolar-ATPase members responsible for anoikis resistance while the manipulation of these pathways induced anoikis. However, the mechanisms underlying anoikis resistance and subsequent metastasis are yet to be fully elucidated, thus limiting anoikis-targeting drug exploration for metastasis control. Herein, our RNA-seq data revealed upregulated genes associated with proteasome activity (such as PSMA, PSMB, PSMD, and POMP) in ECM detached cancer cells compared to adherent cancer cells. Targeting this, using proteasome inhibitors (MG132 or bortezomib) in breast cancer, cervical, and melanoma cell lines sensitized cancer cells to anoikis through increased cellular, mitochondrial stress, and misfolded protein accumulation. Moreover, Bortezomib treatment in vivo in melanoma tumor model repressed metastasis. These data demonstrate proteasome activity is hijacked by ECM detached cancer cells to maintain proteostasis thus promoting anoikis resistance and metastasis. Regardless of the impressive outcome in treating hematological malignancies, proteasome inhibitors show little effect against solid tumors in several clinical trials that utilized selective and more potent inhibitors either as a single or in combinatory therapy. In this sense, our finding suggests proteasome inhibitors may be more attractive for metastasis control rather than local tumor treatment. Altogether, our findings demonstrate enhanced proteasome activity within the tumor cells is critical for anoikis resistance, and targeting this can markedly overcome resistance and control tumor metastasis. Citation Format: Funmilayo Adeshakin, Guizhong Zhang, Adeleye Adeshakin, Xiaochun Wan. Inhibiting proteasome in extracellular matrix (ECM) detached cells promotes anoikis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 265.