Prostate cancer: an enzalutamide antiandrogen withdrawal syndrome

Androgen Receptor Signaling Inhibitor Withdrawal Syndrome After Castration-resistant Prostate Cancer

Androgen-deprivation therapy is an extremely effective treatment for progressive prostate cancer. Previously, the first-line treatment for progressive prostate cancer was combined androgen blockade (CAB). If the disease progressed to castration-resistant prostate cancer, the administration of androgen receptor signaling inhibitors (ARSIs) was recommended. When elevated serum prostate-specific antigen (PSA) levels are seen during CAB treatment, it is important to suspect antiandrogen withdrawal syndrome (AWS), discontinue CAB, and monitor the changes in the serum PSA levels. If a reduction in the patient's PSA levels is subsequently observed, antiandrogens should be discontinued and the patient should be followed, but if their PSA level rises they should be transitioned to ARSI treatment. Recently, there have been reports of withdrawal syndrome (WS) after ARSI treatment. With the increased use of ARSIs, such as abiraterone acetate, enzalutamide, apalutamide, and dalorutamide, it is necessary to consider ARSI WS when a patient's serum PSA level increases during ARSI treatment. Unnecessary treatment can be avoided if the confirmation of ARSI WS is prioritized. Conversely, if it is not confirmed there is a risk that second-line treatment will be delayed. This is a review of recent studies of ARSI WS. It also discusses future prospects in this field.

Combination therapies with Wnt signaling inhibition: A better choice for prostate cancer treatment

The intractability and high mortality rate of castration-resistant prostate cancer (CRPC) remain the most challenging problems in the field of prostate cancer (PCa). Emerging evidence has shown that the dysregulation of Wnt signaling pathways, which are highly conserved cascades that regulate embryonic development and maintain tissue homeostasis, is involved in various stages of PCa occurrence and progression. In this review, we systemically discuss the mechanisms by which the androgen receptor (AR) signaling pathway and Wnt signaling pathways participate in the occurrence of PCa and its progression to CRPC. Specifically, we elaborate on how Wnt signaling pathways induce the malignant transformation of prostate cells, promote the malignant progression of PCa and establish an immunosuppressive prostate tumor microenvironment through interaction with the AR pathway or in an AR-independent manner. We also discuss how Wnt signaling pathways enhances the stemness characteristics of prostate cancer stem cells (PCSCs) to induce the occurrence and metastasis of CPPC. Additionally, we discuss the latest progress in the use of different types of drugs that inhibit the Wnt signaling pathways in the treatment of PCa. We believe that the combination of Wnt signaling-based drugs with endocrine and other therapies is necessary and may enhance the clinical efficacy in the treatment of all types of PCa.

TET2 repression by androgen hormone regulates global hydroxymethylation status and prostate cancer progression

Modulation of epigenetic patterns has promising efficacy for treating cancer. 5-Hydroxymethylated cytosine (5-hmC) is an epigenetic mark potentially important in cancer. Here we report that 5-hmC is an epigenetic hallmark of prostate cancer (PCa) progression. A member of the ten-eleven translocation (TET) proteins, which catalyse the oxidation of methylated cytosine (5-mC) to 5-hmC, TET2, is repressed by androgens in PCa. Androgen receptor (AR)-mediated induction of the miR-29 family, which targets TET2, are markedly enhanced in hormone refractory PCa (HRPC) and its high expression predicts poor outcome of PCa patients. Furthermore, decreased expression of miR-29b results in reduced tumour growth and increased TET2 expression in an animal model of HRPC. Interestingly, global 5-hmC modification regulated by miR-29b represses FOXA1 activity. A reduction in 5-hmC activates PCa-related key pathways such as mTOR and AR. Thus, DNA modification directly links the TET2-dependent epigenetic pathway regulated by AR to 5-hmC-mediated tumour progression.

An update on enzalutamide in the treatment of prostate cancer

Enzalutamide is an oral androgen receptor inhibitor that targets multiple steps in the androgen receptor signaling pathway. In the randomized phase III AFFIRM study, significant improvements in survival versus placebo were observed when enzalutamide was used as a treatment for patients with metastatic castration-resistant prostate cancer (mCRPC) following prior treatment with docetaxel. Additional benefits included significant delay in time to first skeletal-related event, and improvement in several measures of pain and health-related quality of life. Treatment effects were consistent across all prespecified subgroups. The phase III PREVAIL study evaluated enzalutamide versus placebo in patients with mCRPC who had not received chemotherapy. Enzalutamide significantly decreased the risk of radiographic progression and death. There were also significant improvements in all secondary and prespecified exploratory endpoints, including delayed initiation of chemotherapy, reduction in risk of first skeletal-related event and a high percentage of patients with objective response compared with placebo. Enzalutamide was also studied in hormone naïve patients (as monotherapy) in a small, open-label phase II study in patients with prostate cancer who were eligible for androgen-deprivation therapy. A prostate-specific antigen (PSA) response, defined as ⩾80% decline in PSA level from baseline at week 25, was achieved in 92.5% of patients. Long-term follow up is ongoing. Despite differences between these three trials, enzalutamide displayed a favorable safety profile in all three patient populations. Similar rates of adverse events between the enzalutamide and placebo groups were observed in AFFIRM and PREVAIL, with fatigue, diarrhea, back pain and hot flashes being more common with enzalutamide than with placebo. Hypertension was reported at a higher rate in the enzalutamide group than in the placebo group in PREVAIL. Breast-related disorders associated with enzalutamide treatment were also reported in the Monotherapy trial. Few seizures were reported in any trial. Enzalutamide is being studied in several early disease state populations.