Introduction
Prostate cancer (PCa) is a common malignancy threatening the health and life of men worldwide, which is aggressive to the male genitourinary system ( Zhu et al., 2021 ). According to the 2021 cancer statistics, the estimated new PCa cases is up to 248,530, and the cancer-related deaths are about 34,130 in the USA ( Siegel et al., 2021 ). Apparently, the incidence and mortality of PCa increased year by year, accounting for more than 90% of reproductive organ cancer diseases ( Zelic et al., 2020 ). As is well known, PCa is a highly heterogeneous tumor, and the overall prognosis of PCa patients varies differentially. Prostate adenocarcinoma (PRAD), which expresses androgen receptor (AR), is the most frequent histological subtype of Pca ( Chen, Chu & Lin, 2022 ). For patients with early-stage diseases, the combined strategies of PCa were overall effective, including radical prostatectomy, androgen deprivation therapy (ADT), chemotherapy, and radiotherapy ( Gamat & McNeel, 2017 ). Nevertheless, approximately 25% of patients would develop into advanced stages with distal metastases and drug resistance. Particularly, the development of a highly aggressive castration-resistant PCa (CRPC) would result in poor survival and limited treatment strategies for patients ( Fan et al., 2021 ). As a result, there is a pressing need in developing more effective strategies and identifying potential innovative targets to improve the overall survival of PRAD patients. Owing to the remarkable heterogeneity of PCa, patients with distinct prostate-specific antigen (PSA) levels or Gleason scores may have various prognosis even at the same clinical stages. Therefore, we intended to find more effective diagnostic and prognostic markers for PRAD.

Given that the AR signaling plays an essential role in the progression of PCa, ADT, like bicalutamide and abiraterone, has become the foundation for patients with locally advanced or metastatic PRAD ( Lorente et al., 2015 ). However, the lethal CRPC state is a serious problem for patients and there are currently no effective managements ( Hong et al., 2021 ). Intensive data have indicated that aberrant activation of AR signaling and downstream targets are essential determinants for the progression of CRPC ( Chandrasekar et al., 2015 ). Enzalutamide, as a novel inhibitor of the AR pathway, directly binds to the ligand-binding domain of AR, thus suppressing nuclear translocation and transcriptional activity of AR. Nonetheless, the development of enzalutamide resistance (Enza-R) is an inevitable problem for patients with advanced disease ( Antonarakis et al., 2014 ; Annala et al., 2018 ). Significant insights into the mechanisms of Enza-R have been provided, including amplification of AR or AR-related genes, abnormal expression, generation of AR splice variants, and activation of AR bypass crosstalk or downstream targets. Genomic-wide sequencing based on large PCa samples has identified amplification and activation of AR genes, which account for nearly 50% of all CRPC patients. Particularly, various key regulators such as HOXB13, FOXM1, or FOXA1, have been found to recruit AR or its variants to specific promoters, to sustaining cell growth and promoting progression of PRAD even in the presence of enzalutamide ( Ketola et al., 2017 ; Song et al., 2019 ). These results indicate that sustained AR expression or activation of downstream targets represents a major vulnerability in the treatment of Enza-R PRAD.

Recently, single-cell genomics, such as single-cell RNA sequencing (scRNA-seq), have emerged as powerful tools for exploring the genetic or functional heterogeneity, reconstructing evolutionary lineages, and identifying rare subpopulations ( Ziegenhain et al., 2017 ). Particularly, scRNA-seq has proven effective in transcriptional classification of cell types such as breast cancer, lung adenocarcinoma, and pancreatic cancer ( Kalucka et al., 2020 ; Katzenelenbogen et al., 2020 ; Chen et al., 2021 ). Besides, scRNA-seq in human tumors has provided valuable insights into tumor heterogeneity and the existence of distinct subpopulations, which are crucial for understanding cancer-related mechanisms. For instance, a recent study on human lung cancers utilized the scRNA-seq in 49 clinical biopsies identified active T-lymphocytes and decreased macrophages in residual disease and immunosuppressive cells in progressive disease ( Maynard et al., 2020 ). Another study conducted the scRNA-seq on docetaxel-sensitive and -resistant variants of PRAD DU145 and PC3 cell lines, revealing NUPR1 as a mediator of PRAD drug resistance ( Schnepp et al., 2020 ). Given that scRNA-seq data of PRAD cells or samples are publicly available, we aimed to integrate scRNA-seq data with RNA-seq data deposited in TCGA to identify potential AR-related genes (ARGs) that contribute to progression and drug resistance in PRAD.

In the present study, we performed a re-analysis of scRNA-seq data from PRAD cells obtained from the GSE99795 dataset to explore AR-related drivers. Multiple PRAD cohorts were utilized to identify a series of ARGs with significant prognostic value. Functional experiments were conducted to highlight the role of ORC1 as a crucial factor in PRAD cell proliferation and Enza-R, thereby providing insights for individualized treatment strategies in PRAD.