Dysregulation of the PRUNE2/PCA3 genetic axis in human prostate cancer: from experimental discovery to validation in two independent patient cohorts.

Background: We have previously shown that the long non-coding (lnc)RNA prostate cancer associated 3 (PCA3; formerly prostate cancer antigen 3) functions as a trans-dominant negative oncogene by targeting the previously unrecognized prostate cancer suppressor gene PRUNE2 (a homolog of the Drosophila prune gene), thereby forming a functional unit within a unique allelic locus in human cells. Here, we investigated the PCA3/PRUNE2 regulatory axis from early (tumorigenic) to late (biochemical recurrence) genetic events during human prostate cancer progression. Methods: The reciprocal PCA3 and PRUNE2 gene expression relationship in paired prostate cancer and adjacent normal prostate was analyzed in two independent retrospective cohorts of clinically annotated cases post-radical prostatectomy: a single-institutional discovery cohort (n=107) and a multi-institutional validation cohort (n=497). We compared the tumor gene expression of PCA3 and PRUNE2 to their corresponding expression in the normal prostate. We also serially examined clinical/pathological variables including time to disease recurrence. Results: We consistently observed increased expression of PCA3 and decreased expression of PRUNE2 in prostate cancer compared with the adjacent normal prostate across all tumor grades and stages. However, there was no association between the relative gene expression levels of PCA3 or PRUNE2 and time to disease recurrence, independent of tumor grades and stages. Conclusions: We concluded that upregulation of the lncRNA PCA3 and targeted downregulation of the protein-coding PRUNE2 gene in prostate cancer could be early (rather than late) molecular events in the progression of human prostate tumorigenesis but are not associated with biochemical recurrence. Further studies of PCA3/PRUNE2 dysregulation are warranted. Funding: We received support from the Human Tissue Repository and Tissue Analysis Shared Resource from the Department of Pathology of the University of New Mexico School of Medicine and a pilot award from the University of New Mexico Comprehensive Cancer Center. RP and WA were supported by awards from the Levy-Longenbaugh Donor-Advised Fund and the Prostate Cancer Foundation. EDN reports research fellowship support from the Brazilian National Council for Scientific and Technological Development (CNPq), Brazil, and the Associação Beneficente Alzira Denise Hertzog Silva (ABADHS), Brazil. This work has been funded in part by the NCI Cancer Center Support Grants (CCSG; P30) to the University of New Mexico Comprehensive Cancer Center (CA118100) and the Rutgers Cancer Institute of New Jersey (CA072720).

Survival outcomes for advanced kidney cancer patients in the era of targeted therapies.

BACKGROUND: Advanced renal cell carcinoma (RCC) results in over 14,000 deaths each year in the United States alone. The therapeutic landscape for advanced RCC changed dramatically with the approval of tyrosine kinase inhibitors (TKI) between 2006 and 2012. A large-scale analysis of survival trends has not been performed in the TKI era to determine their impact on outcomes for advanced RCC patients. METHODS: The Surveillance, Epidemiology and End-Results (SEER) database was queried for adult patients with advanced RCC diagnosed between 2000 and 2013. Patients were divided into two cohorts based on the year of diagnosis-pre-TKI cohort [2000-2006] and TKI cohort [2007-2013]. Kaplan-Meier survival and multivariate Cox proportional hazards analyses were performed. RESULTS: A total of 14,976 patients were included in our study. Median age at diagnosis was 64 years (range, 18-89 years). Median (cancer-specific) overall survival was 10.0 months in the TKI cohort compared with 8.0 months in the pre-TKI cohort, corresponding to a 13% improvement in survival in the TKI area [hazard ratio (HR) for death 0.87; 95% confidence interval (CI), 0.84-0.91, P<0.0001]. Median survival was improved by 2 months for patients with clear-cell RCC histology [HR for death 0.86; 95% CI, 0.84-0.91, P<0.0001]. Patients with non-clear cell RCC had a 25% higher risk of mortality compared with those with clear-cell RCC. Additionally, median survival for non-clear cell RCC patients was not statistically different between the two cohorts (HR for death 0.98; 95% CI, 0.88-1.09, P=0.714). Subgroup analysis showed that elderly patients (age 71 years and above) had a 45% higher risk of death from advanced RCC compared with young patients (aged 18-50 years) [HR for death 1.45; 95% CI, 1.36-1.54, P<0.0001]. Gender and racial disparities in outcomes were also noted with women having a 10% higher risk of death compared with men (HR for death 1.10; 95% CI, 1.06-1.14, P<0.001) and Black patients having a 15% higher risk of death compared with White patients (HR for death 1.15; 95% CI, 1.08-1.23, P<0.0001). CONCLUSIONS: Our study provides a largest registry-based analysis of survival outcomes in the TKI era. In majority of patients, the survival has improved significantly with the advent of TKIs as standard of care therapy. Survival for patients with non-clear cell RCC is clearly worse than clear-cell RCC and does not appear to have changed with TKIs. Elderly patients, women, and Black patients appear to have worse outcomes and these disparities merit further investigation.

Targeted molecular-genetic imaging and ligand-directed therapy in aggressive variant prostate cancer.

Aggressive variant prostate cancers (AVPC) are a clinically defined group of tumors of heterogeneous morphologies, characterized by poor patient survival and for which limited diagnostic and treatment options are currently available. We show that the cell surface 78-kDa glucose-regulated protein (GRP78), a receptor that binds to phage-display-selected ligands, such as the SNTRVAP motif, is a candidate target in AVPC. We report the presence and accessibility of this receptor in clinical specimens from index patients. We also demonstrate that human AVPC cells displaying GRP78 on their surface could be effectively targeted both in vitro and in vivo by SNTRVAP, which also enabled specific delivery of siRNA species to tumor xenografts in mice. Finally, we evaluated ligand-directed strategies based on SNTRVAP-displaying adeno-associated virus/phage (AAVP) particles in mice bearing MDA-PCa-118b, a patient-derived xenograft (PDX) of castration-resistant prostate cancer bone metastasis that we exploited as a model of AVPC. For theranostic (a merging of the terms therapeutic and diagnostic) studies, GRP78-targeting AAVP particles served to deliver the human Herpes simplex virus thymidine kinase type-1 (HSVtk) gene, which has a dual function as a molecular-genetic sensor/reporter and a cell suicide-inducing transgene. We observed specific and simultaneous PET imaging and treatment of tumors in this preclinical model of AVPC. Our findings demonstrate the feasibility of GPR78-targeting, ligand-directed theranostics for translational applications in AVPC.

PRUNE2 is a human prostate cancer suppressor regulated by the intronic long noncoding RNA PCA3.

Prostate cancer antigen 3 (PCA3) is the most specific prostate cancer biomarker but its function remains unknown. Here we identify PRUNE2, a target protein-coding gene variant, which harbors the PCA3 locus, thereby classifying PCA3 as an antisense intronic long noncoding (lnc)RNA. We show that PCA3 controls PRUNE2 levels via a unique regulatory mechanism involving formation of a PRUNE2/PCA3 double-stranded RNA that undergoes adenosine deaminase acting on RNA (ADAR)-dependent adenosine-to-inosine RNA editing. PRUNE2 expression or silencing in prostate cancer cells decreased and increased cell proliferation, respectively. Moreover, PRUNE2 and PCA3 elicited opposite effects on tumor growth in immunodeficient tumor-bearing mice. Coregulation and RNA editing of PRUNE2 and PCA3 were confirmed in human prostate cancer specimens, supporting the medical relevance of our findings. These results establish PCA3 as a dominant-negative oncogene and PRUNE2 as an unrecognized tumor suppressor gene in human prostate cancer, and their regulatory axis represents a unique molecular target for diagnostic and therapeutic intervention.

Drug design strategies for the treatment of prostate cancer.

INTRODUCTION: While metastatic prostate cancer remains an incurable tumor, remarkable progress has been made with novel drug design strategies for this incurable disease. Several new agents, including hormonal analogues, cytotoxic chemotherapy drugs, radionuclides and innovative targeted therapies, have recently been approved by the FDA for use in advanced and/or metastatic castrate-resistant prostate cancer. Furthermore, a growing number of new diagnostic or predictive genetic tests have also been incorporated into the management of this disease. Immunotherapy-based approaches have shown promise and have led to drug approvals. Other experimental approaches such as vascular targeting are in early translational clinical trials. AREAS COVERED: Herein, the authors outline select state-of-the-art approaches in the field. They also discuss the current challenges and future opportunities in the medical care of prostate cancer patients. EXPERT OPINION: An inherent challenge in the treatment of prostate cancer is to determine which patients need immediate aggressive treatment versus active surveillance. For patients needing aggressive treatment, integrating the sequence of therapeutic interventions, to provide the most benefit, remains a challenge that clinicians face. Recently, several genetic tests have been approved, facilitating early treatment decisions. Innovative targeted therapies are moving towards clinical applications, providing treatment options for tumors previously considered refractory to androgen ablation treatment.