Therapeutic Targeting of Mitochondrial Plasticity and Redox Control to Overcome Cancer Chemoresistance

Abstract

Mitochondria are subcellular organelles performing essential metabolic functions contributing to cellular bioenergetics and regulation of cell growth or death. The basic mitochondrial function in fulfilling the need for cell growth and vitality is evidenced by the conditional state whereby cancer cells with depleted mitochondrial DNA (rho zero cells) are no longer capable of forming tumors until newly recruited mitochondria are internalized into the rho zero cells. Herein lies the absolute dependency on mitochondria for tumor growth. In addition, mitochondria are key regulators of cell death (by apoptosis, necroptosis, or other forms of cell death) and are therefore important targets for anticancer therapy. Mitochondrial plasticity regulating their state of fusion or fission is also key to the chemoresistance properties of cancer cells by promoting pro-survival pathways enabling the mitochondria to mitigate against the cellular stresses and extreme conditions within the tumor microenvironment caused by chemotherapy, hypoxia, or oxidative stress. This review discusses many characteristics of mitochondria, the processes and pathways controlling the dynamic changes occurring in the morphology of mitochondria, the roles of reactive oxygen species, and their relationship with mitochondrial fission or fusion. It also examines the relationship of redox to mitophagy when mitochondria become compromised and its effect on cancer cell survival, stemness and the changes accompanying malignant progression from primary tumors to metastatic disease. A challenging question that arises is whether the changes in mitochondrial dynamics and their regulation can provide opportunities for improving drug targeting during cancer treatment and enhancing survival outcomes.