Management of castrate-resistant prostate cancer in older men

Development of a High-Throughput Screening Assay for Small-Molecule Inhibitors of Androgen Receptor Splice Variants

The role of the androgen receptor (AR) in the progression of prostate cancer (PCa) is well established and competitive inhibition of AR ligand binding domain (LBD) has been the mainstay of antiandrogen therapies for advanced and metastatic disease. However, the efficacy of such drugs is often limited by the emergence of resistance, mediated through point mutations and receptor splice variants lacking the AR-LBD. As a result, the prognosis for patients with malignant, castrate-resistant disease remains poor. The amino terminal domain (NTD) of the AR has been shown to be critical for AR function. Its modular activation function (AF-1) is important for both gene regulation and participation in protein–protein interactions. However, due to the intrinsically disordered structure of the domain, its potential as a candidate for therapeutic intervention has been generally overlooked. In this article, we describe the design and development of a functional cell-based assay aimed at identifying small-molecule inhibitors of the AR-NTD. We demonstrate the suitability of the assay for high-throughput screening platforms and validate two initial hits emerging from a small, targeted, library screen in PCa cells.

Effectiveness of first-line abiraterone versus enzalutamide among patients ≥80 years of age with metastatic castration-resistant prostate cancer: A retrospective propensity score-weighted comparative cohort study

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) disproportionately affects the elderly. There is limited data assessing the efficacy and tolerability of abiraterone acetate (AA) versus enzalutamide in this population.

OBJECTIVE

To compare the clinical efficacy and tolerability of AA versus enzalutamide in patients ≥ 80 years with mCRPC.

DESIGN, SETTING AND PARTICIPANTS

A retrospective propensity-weighted comparative cohort study of first-line AA versus enzalutamide among patients with mCRPC aged ≥80 years.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Inverse probability treatment weights based on propensity scores were generated to assess the treatment effect of AA versus enzalutamide on time to PSA progression (TTPP), time to progression (TTP) (first of PSA/radiographic/clinical progression) and overall survival using a weighted Cox proportional hazards model. PSA response rate (PSA RR) was compared between groups using Χ².

RESULTS AND LIMITATIONS

One hundred fifty-three patients received AA, and 125 received enzalutamide. Enzalutamide was associated with higher PSA RR (61.6% vs 43.8%, P < 0.004), and TTP (hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.50-0.88, P = 0.01) but not TTPP (HR 0.73, 95% CI 0.53-1.01, P = 0.06). There were significantly more dose reductions with enzalutamide (22.9% vs 44.8%, P > 0.001) but there was no interaction between median proportion of full dose received and TTPP or TTP for either drug. Rates of treatment discontinuation (for reasons other than progression) were also significantly different between AA and enzalutamide (28.8% vs 40.8%, respectively, P = 0.04). The most common reason for dose reductions and discontinuation of enzalutamide was fatigue (30.4% and 5.6%, respectively).

CONCLUSIONS

Despite more dose reductions and a higher treatment discontinuation rate, enzalutamide was associated with a higher PSA RR and longer time to progression, than AA. Given that clinical outcomes were not adversely impacted by decreased treatment exposure, dose modification may be a useful treatment strategy to balance toxicity and tolerance.

New Protocol of Intermittent Androgen Deprivation Therapy for Patients With Metastatic Prostate Cancer: A Retrospective Study

BACKGROUND

The optimal points for halting and resuming treatment in intermittent androgen deprivation therapy (IADT) for metastatic prostate cancer patients are controversial.

PATIENTS AND METHODS

In the 65 metastatic prostate cancer patients in group 1, androgen deprivation therapy was stopped when prostate-specific antigen (PSA) levels reached a nadir and was resumed when PSA levels doubled and ≥ 1.0 ng/mL (new protocol). In the 62 patients in group 2, androgen deprivation therapy was stopped 3 months after PSA = 0.2 ng/mL and resumed at PSA ≥ 4.0 ng/mL (Chinese Urological Association guideline). The total IADT duration, overall on-treatment and off-treatment time, tumor clinical progression ratio, performance status improvement, and treatment-related adverse effects were retrospectively analyzed.

RESULTS

In groups 1 and 2, the median total IADT durations were 51 and 46.5 months (significant difference, P = .006), median overall on-treatment times were 28 and 27.5 months (no significant difference, P > .05), and median overall off-treatment times were 23 and 19 months (significant difference, P < .001), respectively. Multivariate Cox regression analysis indicated that patients in group 1 had significantly higher progression-free-survival (hazard ratio, 0.634; P = .014). Two cases of clinical progression occurred group 1 and 5 in group 2; there was no significant difference (P > .05). There were no significant differences between the groups in terms of performance status improvement and treatment-related adverse effects.

CONCLUSION

The new protocol was found to be beneficial, showing less biochemical/clinical progression, satisfactory performance status, and acceptable treatment-related adverse effects.

MicroRNA-124: An emerging therapeutic target in cancer

MicroRNAs (miRNAs) are noncoding single‐stranded RNAs, approximately 20‐24 nucleotides in length, known as powerful posttranscriptional regulators. miRNAs play important regulatory roles in cellular processes by changing messenger RNA expression and are widely involved in human diseases, including tumors. It has been reported in the literature that miRNAs have a precise role in cell proliferation, programmed cell death, differentiation, and expression of coding genes. MicroRNA‐124 (miR‐124) has reduced exparession in various human neoplasms and is believed to be related to the occurrence, development, and prognosis of malignant tumors. In our review, we focus on the specific molecular functions of miR‐124 and the downstream gene targets in major cancers, which provide preclinical evidence for the treatment of human cancer. Although some obstacles exist, miR‐124 is still attracting intensive research focus as a promising and effective anticancer weapon.

Human ex vivo 3D bone model recapitulates osteocyte response to metastatic prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths among American men. Unfortunately, there is no cure once the tumor is established within the bone niche. Although osteocytes are master regulators of bone homeostasis and remodeling, their role in supporting PCa metastases remains poorly defined. This is largely due to a lack of suitable ex vivo models capable of recapitulating the physiological behavior of primary osteocytes. To address this need, we integrated an engineered bone tissue model formed by 3D-networked primary human osteocytes, with conditionally reprogrammed (CR) primary human PCa cells. CR PCa cells induced a significant increase in the expression of fibroblast growth factor 23 (FGF23) by osteocytes. The expression of the Wnt inhibitors sclerostin and dickkopf-1 (Dkk-1), exhibited contrasting trends, where sclerostin decreased while Dkk-1 increased. Furthermore, alkaline phosphatase (ALP) was induced with a concomitant increase in mineralization, consistent with the predominantly osteoblastic PCa-bone metastasis niche seen in patients. Lastly, we confirmed that traditional 2D culture failed to reproduce these key responses, making the use of our ex vivo engineered human 3D bone tissue an ideal platform for modeling PCa-bone interactions.