Integrating pharmacogenomics data-driven prediction with bulk and single-cell RNAseq to demonstrate the efficacy of an NAMPT inhibitor against aggressive, taxane-resistant, and stem-like cells in lethal prostate cancer

Metastatic prostate cancer is the second leading cause of cancer deaths in US men. Resistance to standard medical castration and secondary taxane-based chemotherapy is nearly universal. Further, presence of cancer stem-like cells (EMT/epithelial to mesenchymal transdifferentiation) and neuroendocrine PCa (NEPC) subtypes significantly contribute to aggressive/advanced/lethal variants of PCa (AVPC).In this study, first we used single-cell RNA sequencing (scRNAseq) analysis to demonstrate that ARlow PCa cells in metastatic prostate cancer, including castration-sensitive tumors, harbored signatures of EMT, and ‘cancer stemness’. Next, we introduced a novel pharmacogenomics data-driven computational approach and identified several potential agents that can be re-purposed as novel secondary drugs (“secDrugs”) to treat advance variants of Prostate cancer. Using scRNAseq as a biomarker-based drug screen, we demonstrated that a majority of the single-cell subclones in mCRPC and mCSPC cell lines also showed significantly high expression of the NAMPT pathway genes, indicating that the secDrug FK866, which targets NAMPT, is potentially effective against drug-resistant and stem-cell-like subpopulation cluster. Next, we showed significant in vitro cytotoxicity of FK866 as single-agent and in combination with the taxanes or Enzalutamide against models of clinically-advanced PCa. We performed bulk- and single-cell RNAseq to identify several pathways underlining FK866 mechanism of action and found that in addition to NAMPT inhibition, FK866 regulates tumor metastasis, cell migration, invasion, DNA repair machinery, redox homeostasis, autophagy, as well as cancer stemness–related genes HES1 and CD44. Further, we performed a microfluidic chip-based cell migration assay that demonstrated that FK866 reduces cancer cell invasion and motility, indicating abrogation of metastasis. Finally, using multiple PCa patient datasets, we showed that FK866 is potentially capable of reversing expression of several genes associated with biochemical recurrence and inter-ethnic differences, including IFITM3 and LTB4R.Thus, using FK866 as a proof-of-concept drug, we introduced a novel, universally applicable preclinical drug development pipeline to circumvent subclonal aggressiveness, drug resistance, and stemness in lethal PCa.