Nuclear and non-nuclear functions of NKX3.1 in suppression of prostate cancer - Project Summary/Abstract Our studies will investigate mechanisms associated with aging-related prostate cancer progression through our investigations of the prostate-specific homeobox gene NKX3.1. Work by us and others has shown that NKX3.1 is essential for normal prostate differentiation, whereas its loss promotes prostate cancer during aging. NKX3.1 serves as a gatekeeper to protect the prostate epithelium from cancer-promoting insults including oxidative stress and inflammation. Conversely, NKX3.1 loss abrogates such protection, thereby accelerating cancer progression. Our recent studies and new Preliminary data show that the traditional functions of NKX3.1 as a nuclear transcription factor are augmented by non-nuclear functions that are also required for suppression of prostate cancer. Thus, in normal contexts, NKX3.1 is localized to the nucleus where it regulates nuclear target genes. However, in conditions of oxidative stress, NKX3.1 also becomes localized to mitochondria, where it regulates mitochondrial genes essential for oxidative phosphorylation (OXPHOS). Our Preliminary data further show that the consequences of NKX3.1 loss are compounded as cells acquire mitochondrial mutations, leading to aging-associated acceleration of prostate cancer. In particular, our analyses of mouse models having loss of function of Nkx3.1 combined with a defective PolgA gene that renders mutated mitochondrial DNA (Nkx3.1; PolgA mutant mice) reveals aging-related acceleration of prostate cancer with evident mitochondrial dysfunction, reduced OXPHOS activity, and hallmarks of aging, including cellular senescence and telomere attrition. Thus, our studies will examine the hypothesis that suppression of prostate cancer by NKX3.1 requires its nuclear and non-nuclear functions, and that NKX3.1 loss synergizes with mitochondrial dysfunction to promote prostate cancer during aging. Aim 1 will investigate the nuclear and non-nuclear functions of NKX3.1 in prostate cancer by leveraging a toolkit of NKX3.1 variants that do or do not bind to DNA, and that selectively localize to or are excluded from the nucleus or mitochondria to investigate the functions of nuclear and mitochondrial NKX3.1 target genes. Aim 2 will study the synergy of NKX3.1 loss and mitochondrial dysfunction for prostate cancer in Nkx3.1; PolgA mutant mice. We will evaluate the functions of selected mitochondrial mutations by base editing mitochondrial DNA in human prostate cancer cells. Aim 3 will investigate mechanistic determinants of aging-related prostate cancer progression by identifying master regulators (MRs) of NKX3.1 loss and mitochondrial dysfunction. Leveraging our biobank of human patient-derived organoid models, we will establish organoid models having perturbation of selected MRs together with NKX3.1 loss and mitochondrial mutations to investigate their functions. Altogether, these studies will provide a unique opportunity to investigate communication between the nucleus and mitochondria, and the role of NKX3.1 in these processes, as well as mechanistic insights regarding the roles of NKX3.1 loss and mitochondrial dysfunction for aging-related prostate cancer, and novel mouse and human patient-derived models to study these mechanisms.
