Introduction: Androgen receptor (AR) blockade using antiandrogens is a mainstay for the treatment of castration resistant prostate cancer (CRPC). Unfortunately, drug resistance occurs frequently due to mechanisms that are not completely understood. Wnt5a, a representative ligand of non-canonical Wnt signaling, is expressed in circulating tumor cells from CRPC patients treated with enzalutamide. FZD2, the cognate frizzled receptor for Wnt5a, is the most commonly co-upregulated non-canonical Wnt receptor in prostate cancer. Here we determine the contribution of non-canonical Wnt5a/FZD2 to enzalutamide treatment resistance, and explore the potential of targeting Wnt5a/FZD2 to overcome antiandrogen resistance in castration resistant prostate cancer.
Methods: Wnt5a/FZD2 expression was examined in enzalutamide resistant C4-2B MDVR cells. Wnt5a and FZD2 expression were modulated using specific siRNAs. Cell growth, colony formation, migration and invasion were determined in vitro. RNA sequencing was analyzed on C4-2B MDVR cells with WNT5a/FZD2 knocked down; gene expression of non-canonical Wnt signaling, AR and AR-V7 signature genes were analyzed. A novel RNA bioengineered Wnt5a siRNA (tRNA-siWnt5A) was developed to target Wnt5a/FZD2 signaling. The effect of tRNA-siWnt5a on tumor growth and sensitivity to enzalutamide was evaluated in vitro and in vivo.
Results: Wnt5a and FZD2 are highly co-upregulated in CRPC patients and enzalutamide resistant C4-2B MDVR cells compared to parental C4-2B cells. Knocking down Wnt5a and FZD2 abrogates the increase of full-length AR and AR variant expression and diminishes the enrichment of genes involved in the non-canonical Wnt signaling pathway. Blocking Wnt5a and FZD2 using specific siRNAs suppresses prostate cancer cell growth, colony formation, migration and invasion. Wnt5a and FZD2 knockdown with siRNA resensitized C4-2B MDVR cells to enzalutamide treatment. Targeting Wnt5a using the bioengineered tRNA-siWnt5A inhibited the growth of enzalutamide resistant prostate cancer cells and resensitized cells to enzalutamide in vitro, and resistant CRPC LuCaP35CR PDX tumor growth in vivo.
Conclusions: Our studies suggest that Wnt5a/FZD2 confers enzalutamide resistance and prostate cancer survival and proliferation. Targeting the non-canonical Wnt5a/FZD2 pathway suppresses tumors expressing high level of Wnt5a and FZD2, not only overcoming resistance but potentiating anti-tumor effects of enzalutamide in CRPC patients.
Source of Funding: CA250082, CA 225836, DOD PC180180.
.jpg)
.jpg)
