Loss of Fibroblast-Dependent Androgen Receptor Activation in Prostate Cancer Cells is Involved in the Mechanism of Acquired Resistance to Castration

Abstract

Loss of androgen receptor (AR) dependency in prostate cancer (PCa) cells is associated with progression to castration-resistant prostate cancer (CRPC). The tumor stroma is enriched in fibroblasts that secrete AR-activating factors. To investigate the roles of fibroblasts in AR activation under androgen deprivation, we used three sublines of androgen-sensitive LNCaP cells (E9 and F10 cells: low androgen sensitivity; and AIDL cells: androgen insensitivity) and original fibroblasts derived from patients with PCa. We performed in vivo experiments using three sublines of LNCaP cells and original fibroblasts to form homotypic tumors. The volume of tumors derived from E9 cells plus fibroblasts was reduced following androgen deprivation therapy (ADT), whereas that of F10 or AIDL cells plus fibroblasts was increased even after ADT. In tumors derived from E9 cells plus fibroblasts, serum prostate-specific antigen (PSA) decreased rapidly after ADT, but was still detectable. In contrast, serum PSA was increased even in F10 cells inoculated alone. In indirect cocultures with fibroblasts, PSA production was increased in E9 cells. Epidermal growth factor treatment stimulated Akt and p44/42 mitogen-activated protein kinase phosphorylation in E9 cells. Notably, AR splice variant 7 was detected in F10 cells. Overall, we found that fibroblast-secreted AR-activating factors modulated AR signaling in E9 cells after ADT and loss of fibroblast-dependent AR activation in F10 cells may be responsible for CRPC progression.

Heterogeneous induction of an invasive phenotype in prostate cancer cells by coculturing with patient‐derived fibroblasts

“…LNCaP cells were cocultured with each of four patient‐derived fibroblast lines (PrSC, pcPrF‐M5, pcPrF‐M28, and pcPrF‐M31) in six‐well plates using cell culture inserts (BD Falcon) as described previously 14 . LNCaP cells (16 × 10 4 /well) were seeded into six‐well plates in phenol red (+) RPMI‐1640 supplemented with 10% FBS, whereas patient‐derived fibroblasts (PrSC, pcPrF‐M5, pcPrF‐M28, and pcPrF‐M31; 2 × 10 4 /well) were seeded into cell culture inserts containing SCBM medium for 3 days.…”

“…Within a focal lesion, CAFs heterotypically communicate with PCa cells not only by direct cell–cell contact via cell adhesion molecules but also by indirect cell–cell communication via soluble factors 4 . In our experience, however, in vivo or in vitro cocultures of PCa cells and CAFs are not able to recapitulate the histopathology of PCa tissues; for example, PCa cells invade the thick stromal layer, which resembles human prostate stromal structures 8,9,14 To visualize the heterotypic interactions between PCa cells and CAFs, we focused on the contractile activity of CAFs and their clumping on a viscous substrate 15,16 Finally, we developed a novel three‐dimensional (3D) coculture protocol to simulate PCa cell invasion in the reactive stroma.…”

Fibroblast‐derived exosomal microRNA regulates NKX3‐1 expression in androgen‐sensitive, androgen receptor‐dependent prostate cancer cells

“…Our previous studies have also shown that fibroblasts from patients with advanced PCa promote proliferation in PCa cells. 12,13 However, all fibroblasts from patients with advanced PCa do not promote proliferation in PCa cells. To determine the biochemical characteristics of fibroblasts, it is necessary to understand not only the effects of growth factors and cytokines on PCa cell behavior but also the effects of other fibroblast-derived soluble factors on cancer cell differentiation.…”

“…14 Fibroblast-derived growth factors and cytokines promote the proliferation of PCa cells independent of androgen sensitivity and AR dependency. 13 In addition, ARactivating factor-secreted PCa patient-derived fibroblasts induce a cord-like infiltrating growth pattern in PCa cells. 15 These fibroblasts affect the expression levels of various genes, such as CDH2, in androgen-sensitive, ARdependent PCa cells.…”

Fibroblasts as Turned Agents in Cancer Progression

“…AR expression in PC CAFs provides a good prognosis, but a loss of AR [ 454 ] and of fibroblast-dependent androgen activation may be responsible for PC progression [ 455 ]. Spontaneously immortalized stromal fibroblasts [ 456 ] promote the growth and progression of prostate tumors in mice, and stroma can induce permanent gene expression and behavior changes in epithelial cells [ 200 ].…”