Enzalutamide (Xtandi) for patients with metastatic, resistant prostate cancer

Glucocorticoid receptor upregulation increases radioresistance and triggers androgen independence of prostate cancer

BACKGROUND

Despite the overall success of radiotherapy, a significant number of patients develop radioresistance, which leads to local regional recurrence and distant metastasis. We studied whether repeated radiation treatment promotes androgen-independent survival of prostate cancer (PCa) cells and their metastatic potential. We also studied whether glucocorticoid receptor (GR) increase in radioresistant cells is associated with acquisition of these aggressive characteristics.

METHODS

Radioresistant LNCaP (LNCaPR18) and C4-2 (C4-2R26) PCa sublines were developed by repeated radiation treatments of parental cells. Levels and activations of androgen receptor (AR) and GR in radioresistant PCa cells and respective parental cells were investigated in quantitative real-time polymerase chain reaction/Western blot analyses and immunofluorescence staining. Androgen-independent survival of radioresistant cells was tested in in vitro cell growth assays and the castration-resistant survival of these cell-derived tumors were investigated in mouse xenografts.

RESULTS

Higher GR levels, but lower AR levels were detected in radioresistant cells than in parental cells. Radiation-induced GR upregulation was associated with increased intracellular cyclic adenosine monophosphate. As a consequence of GR activation, LNCaPR18 cells survived well in an androgen-depleted culture condition while parental cells could not. Results of in vivo mouse studies showed survival of LNCaPR18 cell-derived tumors in castrated mice while parental cell-derived tumors regressed. The growth of LNCaPR18 cell-derived tumors in castrated mice was impaired when treated with the anti-GR agent mifepristone. In experiments with C4-2/C4-2R26 cell sets, GR activation in C4-2R26 cells increased their metastatic potential.

CONCLUSION

GR activation in radioresistant cells mediates androgen independence and facilitates PCa progression.

Treatment with the WNT5A-mimicking peptide Foxy-5 effectively reduces the metastatic spread of WNT5A-low prostate cancer cells in an orthotopic mouse model

Prostate cancer patients with high WNT5A expression in their tumors have been shown to have more favorable prognosis than those with low WNT5A expression. This suggests that reconstitution of Wnt5a in low WNT5A-expressing tumors might be an attractive therapeutic approach. To explore this idea, we have in the present study used Foxy-5, a WNT5A mimicking peptide, to investigate its impact on primary tumor and metastasis in vivo and on prostate cancer cell viability, apoptosis and invasion in vitro. We used an in vivo orthotopic xenograft mouse model with metastatic luciferase-labeled WNT5A-low DU145 cells and metastatic luciferase-labeled WNT5A-high PC3prostate cancer cells. We provide here the first evidence that Foxy-5 significantly inhibits the initial metastatic dissemination of tumor cells to regional and distal lymph nodes by 90% and 75%, respectively. Importantly, this effect was seen only with the WNT5A-low DU145 cells and not with the WNT5A-high PC3 cells. The inhibiting effect in the DU145-based model occurred despite the fact that no effects were observed on primary tumor growth, apoptosis or proliferation. These findings are consistent with and supported by the in vitro data, where Foxy-5 specifically targets invasion without affecting apoptosis or viability of WNT5A-low prostate cancer cells. To conclude, our data indicate that the WNT5A-mimicking peptide Foxy-5, which has been recently used in a phase 1 clinical trial, is an attractive candidate for complimentary anti-metastatic treatment of prostate cancer patients with tumors exhibiting absent or low WNT5A expression.

ACK1/TNK2 Regulates Histone H4 Tyr88-phosphorylation and AR Gene Expression in Castration-Resistant Prostate Cancer

The androgen receptor (AR) is critical for the progression of prostate cancer to a castration-resistant (CRPC) state. AR antagonists are ineffective due to their inability to repress the expression of AR or its splice variant, AR-V7. Here, we report that the tyrosine kinase ACK1 (TNK2) phosphorylates histone H4 at tyrosine 88 upstream of the AR transcription start site. The WDR5/MLL2 complex reads the H4-Y88-phosphorylation marks and deposits the transcriptionally activating H3K4-trimethyl marks promoting AR transcription. Reversal of the pY88-H4 epigenetic marks by the ACK1 inhibitor (R)-9bMS-sensitized naive and enzalutamide-resistant prostate cancer cells and reduced AR and AR-V7 levels to mitigate CRPC tumor growth. Thus, a feedforward ACK1/pY88-H4/WDR5/MLL2/AR epigenetic circuit drives CRPC and is necessary for maintenance of the malignant state.

Hormonal therapy in oncology: a primer for the radiologist

OBJECTIVE

The purpose of this article is to provide a comprehensive imaging review of the common hormonal therapies used in oncology and the side effects associated with them.

CONCLUSION

Commonly used hormones in oncology include corticosteroids, somatostatin analogues, progestins, gonadotropin-releasing hormone agonists and antagonists, antiandrogens, aromatase inhibitors, and selective estrogen receptor modulators. Familiarity with these hormones and their side effects can help radiologists to be vigilant for the side effects and complications of these agents.

Advanced prostate cancer - patient survival and potential impact of enzalutamide and other emerging therapies

The advent of exponential growth of novel agents tested and approved for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC) has brought about a need for understanding of the mechanism of action, side-effects, and clinical efficacy of these drugs as they relate to these patients. This review will provide a synopsis of the treatment landscape in mCRPC as varying agents such as abiraterone acetate, cabazitaxel, sipuleucel-T, radium, and selected emerging agents are presented. A distinct focus on the utilization of enzalutamide, its mechanism of action, key pivotal trials that brought about its US Food and Drug Administration approval, as well as patient-focused perspectives and clinical implications are discussed herein.