An update on the changing indications for androgen deprivation therapy for prostate cancer

The ternary complex factor protein ELK1 is an independent prognosticator of disease recurrence in prostate cancer

BACKGROUND

Both hormone-sensitive and castration- and enzalutamide-resistant prostate cancers (PCa) depend on the ternary complex factor (TCF) protein ELK1 to serve as a tethering protein for the androgen receptor (AR) to activate a critical set of growth genes. The two sites in ELK1 required for AR binding are conserved in other members of the TCF subfamily, ELK3 and ELK4. Here we examine the potential utility of the three proteins as prognosticators of disease recurrence in PCa.

METHODS

Transcriptional activity assays; Retrospective analysis of PCa recurrence using data on 501 patients in The Cancer Genome Atlas (TCGA) database; Unpaired Wilcoxon rank-sum test and multiple comparison correction using the Holm's method; Spearman's correlations; Kaplan-Meier methods; Univariable and multivariable Cox regression analyses; LASSO-based penalized Cox regression models; Time-dependent area under the receiver operating characteristic (ROC) curve.

RESULTS

ELK4 but not ELK3 was coactivated by AR similar to ELK1. Tumor expression of neither ELK3 nor ELK4 was associated with disease-free survival (DFS). ELK1 was associated with higher clinical T-stage, pathology T-stage, Gleason score, prognostic grade, and positive lymph node status. ELK1 was a negative prognosticator of DFS, independent of ELK3, ELK4, clinical T-stage, pathology T-stage, prognostic grade, lymph node status, age, and race. Inclusion of ELK1 increased the abilities of the Oncotype DX and Prolaris gene panels to predict disease recurrence, correctly predicting disease recurrence in a unique subset of patients.

CONCLUSIONS

ELK1 is a strong, independent prognosticator of disease recurrence in PCa, underscoring its unique role in PCa growth. Inclusion of ELK1 may enhance the utility of currently used prognosticators for clinical decision making in prostate cancer.

Strategy for Tumor-Selective Disruption of Androgen Receptor Function in the Spectrum of Prostate Cancer

PURPOSE

Testosterone suppression in prostate cancer is limited by serious side effects and resistance via restoration of androgen receptor (AR) functionality. ELK1 is required for AR-dependent growth in various hormone-dependent and castration-resistant prostate cancer models. The amino-terminal domain of AR docks at two sites on ELK1 to coactivate essential growth genes. This study explores the ability of small molecules to disrupt the ELK1-AR interaction in the spectrum of prostate cancer, inhibiting AR activity in a manner that would predict functional tumor selectivity.

EXPERIMENTAL DESIGN

Small-molecule drug discovery and extensive biological characterization of a lead compound.

RESULTS

We have discovered a lead molecule (KCI807) that selectively disrupts ELK1-dependent promoter activation by wild-type and variant ARs without interfering with ELK1 activation by ERK. KCI807 has an obligatory flavone scaffold and functional hydroxyl groups on C5 and C3'. KCI807 binds to AR, blocking ELK1 binding, and selectively blocks recruitment of AR to chromatin by ELK1. KCI807 primarily affects a subset of AR target growth genes selectively suppressing AR-dependent growth of prostate cancer cell lines with a better inhibitory profile than enzalutamide. KCI807 also inhibits in vivo growth of castration/enzalutamide-resistant cell line-derived and patient-derived tumor xenografts. In the rodent model, KCI807 has a plasma half-life of 6 hours, and maintenance of its antitumor effect is limited by self-induced metabolism at its 3'-hydroxyl.

CONCLUSIONS

The results offer a mechanism-based therapeutic paradigm for disrupting the AR growth-promoting axis in the spectrum of prostate tumors while reducing global suppression of testosterone actions. KCI807 offers a good lead molecule for drug development.

Androgen-deprivation therapy and metabolic syndrome in men with prostate cancer

PURPOSE/OBJECTIVES

To examine the trajectory of changes in body composition and metabolic profile in men who receive androgen-deprivation therapy (ADT) for prostate cancer.

DESIGN

Prospective longitudinal design with repeated measures.

SETTING

Urban medical center in the southwestern United States.

SAMPLE

55 men starting radiation therapy for prostate cancer.

METHODS

Changes in the parameters of metabolic syndrome were estimated with ADT (n=31) and non-ADT (n=24) groups by repeated-measures analysis of variance implemented by general linear mixed-effects models. Models included interactions between groups and follow-up time to test differences between the groups.

MAIN RESEARCH VARIABLES

Body composition and metabolic variables.

FINDINGS

The ADT group demonstrated a transient increase in waist circumference at the nine-month time point and significant changes in measures of insulin resistance were noted at the three month point. Values for diastolic and systolic blood pressure, plasma glucose, high-density lipoprotein, and triglycerides were not altered for either group. Differences in metabolic variables or measures of body composition did not differ significantly between the groups.

CONCLUSIONS

The findings demonstrate the development of insulin resistance in men receiving ADT as early as three months after starting ADT.

IMPLICATIONS FOR NURSING

Addressing survivorship concerns can lead to the development of nursing interventions designed to reduce adverse effects associated with ADT.

Targeting the androgen receptor with steroid conjugates

The androgen receptor (AR) is a major therapeutic target in prostate cancer pharmacology. Progression of prostate cancer has been linked to elevated expression of AR in malignant tissue, suggesting that AR plays a central role in prostate cancer cell biology. Potent therapeutic agents can be precisely crafted to specifically target AR, potentially averting systemic toxicities associated with nonspecific chemotherapies. In this review, we describe various strategies to generate steroid conjugates that can selectively engage AR with high potency. Analogies to recent developments in nonsteroidal conjugates targeting AR are also evaluated. Particular focus is placed on potential applications in AR pharmacology. The review culminates with a description of future prospects for targeting AR.

The relation between age and androgen deprivation therapy use among men in the Medicare population receiving radiation therapy for prostate cancer

OBJECTIVES

Neoadjuvant and concurrent androgen deprivation therapy (ncADT) is recommended for men with high-risk prostate cancer, but not low-risk cancer or short life expectancy. It is unclear whether the use of ncADT among older men in the community setting is aligned with the potential for clinical benefit.

MATERIALS AND METHODS

We used the Surveillance, Epidemiology, and End Results–Medicare database to assess patterns of ncADT use among men diagnosed with prostate cancer during 2004–2007 who received radiation therapy. Men were stratified according to tumor risk groups and life expectancy. We used logistic regression to identify factors associated with ncADT use within each risk group.

RESULTS

There were 10,686 men in the sample (mean age 74.2 years; 83.4% white). The use of ncADT was 80.7%, 54.1%, and 27.8% in the high-, intermediate-, and low-risk groups, respectively. Men with a life expectancy<5 years had higher rates of ncADT use than men with a life expectancy≥10 years in all risk groups. Within each risk group, advancing age was associated with higher likelihood of receiving ncADT (odds ratio for men aged 80–84 compared to 67–69=1.93 (95% CI 1.37–2.70); 1.51 (95% CI 1.22–1.87); and 1.71 (95% CI 1.14–2.57) for high-, intermediate-, and low-risk groups, respectively).

CONCLUSION

ncADT use is not consistent with guideline recommendations and is more frequent among men who are older, have shorter life expectancy, and are less likely to benefit from therapy.