American Association for Cancer Research
10780432ccr170528-sup-179434_2_supp_4007119_jp362y.png (1.04 MB)

Supplementary Figure 4. RET and p70S6 kinase signaling in prostate cancer. from RET Signaling in Prostate Cancer

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posted on 2023-03-31, 19:22 authored by Kechen Ban, Shu Feng, Longjiang Shao, Michael Ittmann

A. Knockdown of RET with a second siRNA results in decreased p70S6 kinase phosphorylation in response to GFRα1. B and C. Knockdown of p70S6K with a second siRNA completely blocks increased proliferation (B) and invasion (C). The p values for significant differences by t-test are shown.


Department of Defense Prostate Cancer Research

Department of Veterans Affairs Merit Review program

Dan L. Duncan Cancer



Purpose: Large diameter perineural prostate cancer is associated with poor outcomes. GDNF, with its coreceptor GFRα1, binds RET and activates downstream pro-oncogenic signaling. Because both GDNF and GFRα1 are secreted by nerves, we examined the role of RET signaling in prostate cancer.Experimental Design: Expression of RET, GDNF, and/or GFRα1 was assessed. The impact of RET signaling on proliferation, invasion and soft agar colony formation, perineural invasion, and growth in vivo was determined. Cellular signaling downstream of RET was examined by Western blotting.Results: RET is expressed in all prostate cancer cell lines. GFRα1 is only expressed in 22Rv1 cells, which is the only line that responds to exogenous GDNF. In contrast, all cell lines respond to GDNF plus GFRα1. Conditioned medium from dorsal root ganglia contains secreted GFRα1 and promotes transformation-related phenotypes, which can be blocked by anti-GFRα1 antibody. Perineural invasion in the dorsal root ganglion assay is inhibited by anti-GFRα antibody and RET knockdown. In vivo, knockdown of RET inhibits tumor growth. RET signaling activates ERK or AKT signaling depending on context, but phosphorylation of p70S6 kinase is markedly increased in all cases. Knockdown of p70S6 kinase markedly decreases RET induced transformed phenotypes. Finally, RET is expressed in 18% of adenocarcinomas and all three small-cell carcinomas examined.Conclusions: RET promotes transformation associated phenotypes, including perineural invasion in prostate cancer via activation of p70S6 kinase. GFRα1, which is secreted by nerves, is a limiting factor for RET signaling, creating a perineural niche where RET signaling can occur. Clin Cancer Res; 23(16); 4885–96. ©2017 AACR.