These findings collectively suggest that WNT5A may be a key gene that induces CRPC in the bone niche by recruiting and regulating macrophages through CCL2 and BMP6, respectively.

Summary Bone morphogenetic proteins (BMPs) are members of the transforming growth factor (TGF)‐β superfamily which regulates bone formation, haematopoiesis and development. While TGF‐β is known to be a negative regulator of the immune system, the effect of BMPs on the immune system is largely unknown. Herein, the effect of BMP‐6 on the innate immune system was investigated using the murine macrophage cell line RAW 264·7. BMP‐6 altered cellular morphology, inhibited cellular proliferation, increased the fraction of subG1 phase cells, and decreased the fraction of cells in the S and G2M phases, without changing the percentage of apoptotic cells. In addition, BMP‐6 induced expression of pro‐inflammatory inducible nitric oxide synthase (iNOS) and the cytokine tumour necrosis factor (TNF)‐α. Reverse transcription–polymerase chain reaction (RT‐PCR) analysis demonstrated the expression of all three known type II BMP receptors [BMP‐RII, activin (Act)‐RIIA and Act‐RIIB] and two of the three known type I receptors [activin receptor‐like kinase 2 (ALK2) and ALK3]. Over‐expression as well as knock‐down studies using short hairpin RNA (shRNA) demonstrated that BMP‐RII, ALK2 and ALK3 are the functional BMP‐6 receptors in macrophages. Finally, the effect of BMP‐6 was confirmed in murine peritoneal macrophages and the THP‐1 human monocyte cell line. Taken together, these results demonstrate that BMP‐6 regulates the proliferation and gene expression profile of macrophages.

Although second-line antiandrogen therapy (SAT) is the standard of care in men with castration-resistant prostate cancer (CRPC), resistance inevitably occurs. One major proposed mechanism of resistance to SAT involves the emergence of androgen receptor (AR) splice variant-7, AR-V7. Recently, we developed MTX-23 using the principle of proteolysis targeting chimera (PROTAC) to target both AR-V7 and AR-full length (AR-FL). MTX-23 has been designed to simultaneously bind AR's DNA binding domain (DBD) and the Von Hippel–Lindau (VHL) E3 ubiquitin ligase. Immunoblots demonstrated that MTX-23's degradation concentration 50% (DC50) for AR-V7 and AR-FL was 0.37 and 2 μmol/L, respectively. Further studies revealed that MTX-23 inhibited prostate cancer cellular proliferation and increased apoptosis only in androgen-responsive prostate cancer cells. The antiproliferative effect of MTX-23 was partially reversed when either AR-V7 or AR-FL was overexpressed and was completely abrogated when both were overexpressed. To assess the potential therapeutic value of MTX-23, we next generated 12 human prostate cancer cell lines that are resistant to the four FDA-approved SAT agents—abiraterone, enzalutamide, apalutamide, and darolutamide. When resistant cells were treated with MTX-23, decreased cellular proliferation and reduced tumor growth were observed both in vitro and in mice. These results collectively suggest that MTX-23 is a novel PROTAC small molecule that may be effective against SAT-resistant CRPC by degrading both AR-V7 and AR-FL.

Therefore, we propose that BMP-6 secreted by prostate cancer cells induces IL-6 expression in macrophages; IL-6, in turn, stimulates the NED of prostate cancer cells.

In patients with localized renal cell carcinoma the androgen receptor mRNA expression level is associated with prognosis. In addition, cell culture data suggest that enzalutamide may have an effect in limiting the growth of androgen receptor positive renal cell carcinoma.

PurposeTo investigate the relationships among the Wnt/β-catenin pathway, androgen receptor (AR), and clinicopathological factors in hormone-naïve prostate cancer.Materials and MethodsThis study was conducted with132 cases of hormone-naïve prostate cancer treated by prostatectomy and prostate needle biopsy. An immunohistochemical study using antibodies against β-catenin, matrix metalloproteinase-7 (MMP-7), and the AR was performed. For the in vitro study, PC-3, LNCaP, 22Rv1, and DU145 cell lines were used.ResultsThe clinical or pathological stage ware a localized cancer in 36 patients (27.3%), locally advanced cancer in 31 (23.5%), and metastatic cancer in 65 (49.2%). We detected increased β-catenin, AR, and MMP-7 expression with a high Gleason grade, disease progression, and increasing serum prostate-specific antigen (PSA) levels (p<0.01). In Spearman's rank correlations, the expression of cytoplasmic β-catenin, MMP-7, and the AR were found to be significantly positively correlated. In addition, the expression of β-catenin, MMP-7, and the AR were significantly correlated with clinicopathological variables indicative of a poor prognosis. Forty-nine patients with primary androgen deprivation had short response durations from hormone therapy to PSA progression with elevated MMP-7 expression on the Kaplan-Meier curve (p=0.0036).ConclusionsThese data show that an activated Wnt/β-catenin pathway and AR expression in prostate cancer are correlated with metastasis and aggressiveness. In addition, the expression of MMP-7 protein, a target of the Wnt/β-catenin pathway, is associated with PSA progression in prostate cancer patients undergoing primary hormone therapy.

In treating patients with castration resistant prostate cancer (CRPC), enzalutamide, the second-generation androgen receptor (AR) antagonist, is an accepted standard of care. However, clinical benefits are limited to a median time of 4.8 months because resistance inevitably emerges. To determine the mechanism of treatment resistance, we carried out a RNA sequence analysis and found increased expression levels of neuroendocrine markers in the enzalutamide-resistant LNCaP human prostate cancer (CaP) cell line when compared to the parental cell line. Subsequent studies demonstrated that Transcription Factor-4 (TCF4), a transcription factor implicated in WNT signaling, mediated neuroendocrine differentiation (NED) in response to enzalutamide treatment and was elevated in the enzalutamide-resistant LNCaP. In addition, we observed that PTHrP mediated enzalutamide resistance in tissue culture and inducible TCF4 overexpression resulted in enzalutamide-resistance in a mouse xenograft model. Finally, small molecule inhibitors of TCF4 or PTHrP partially reversed enzalutamide resistance in CaP cells. When tissues obtained from men who died of metastatic CaP were examined, a positive correlation was found between the expression levels of TCF4 and PTHrP. Taken together, the current results indicate that TCF4 induces enzalutamide resistance via NED in CaP.

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