ABSTRACT
Recent advances in cancer immunology revealed immune-related properties of cancer cells as novel promising therapeutic targets. The two TNF superfamily members, APRIL (TNFSF13), and BAFF (TNFSF13B), which are type II membrane proteins, released in active forms by proteolytic cleavage and are primarily involved in B-lymphocyte maturation, have also been associated with tumor growth and aggressiveness in several solid tumors, including breast cancer. In the present work we studied the effect of APRIL and BAFF on epithelial to mesenchymal transition, migration, and stemness of breast cancer cells. Our findings show that both molecules increase epithelial to mesenchymal transition and migratory capacity of breast cancer cells, as well as cancer stem cell numbers, by increasing the expression of pluripotency genes such as ALDH1A1, KLF4, and NANOG. These effects are mediated by their common receptor BCMA (TNFRSF17) and the JNK signaling pathway. Interestingly, transcriptional data analysis from breast cancer cells and patients revealed that androgens can increase APRIL transcription and subsequently, in an autocrine/paracrine manner, enhance its pluripotency effect. In conclusion, our data suggest a possible role of APRIL and BAFF in breast cancer disease progression and provide evidence for a new possible mechanism of therapy resistance, that could be particularly relevant in aromatase inhibitors-treated patients, were local androgen is increased.
ABSTRACT
BACKGROUND/AIMS: Reports regarding the role of androgen in breast cancer (BC) are conflicting. Some studies suggest that androgen could lead to undesirable responses in the presence of certain BC tumor characteristics. We have shown that androgen induces C-X-C motif chemokine 12 (CXCL12) in BC cell lines. Our aim was to identify the mechanisms regulating the phenotypic effects of androgen-induced CXCL12 on Androgen Receptor (AR) positive BC cell lines. METHODS: We analyzed the expression of CXCL12 and its receptors with qPCR and ELISA and the role of Nuclear Receptor Coactivator 1 (NCOA1) in this effect. AR effects on the CXCL12 promoter was studied via Chromatin-immunoprecipitation. We also analyzed publically available data from The Cancer Genome Atlas to verify AR-CXCL12 interactions and to identify the effect or Aromatase Inhibitors (AI) therapy on CXCL12 expression and disease progression in AR positive cases. RESULTS: CXCL12 induction occurs only in AR-positive BC cell lines, possibly via an Androgen Response Element, upstream of the CXCL12 promoter. The steroid receptor co-regulator NCOA1 is critical for this effect. Androgen only induced the motility of p53-mutant BC cells T47D cells via upregulation of CXCR4 expression while they had no effect on wild-type p53 MCF-7 cells. Loss of CXCR4 expression and depletion of CXCL12 abolished the effect of androgen in T47D cells while inhibition of p53 expression in MCF-7 cells made them responsive to androgen and increased their motility in the presence to androgen. Patients with estrogen receptor positive (ER+)/AR+ BC treated with AIs were at increased risk of disease progression compared to ER+/AR+ non-AI treated and ER+/AR- AI treated cases. CONCLUSION: AIs may lead to unfavorable responses in some ER/AR positive BC cases, especially in patients with AR+, p53 mutant tumors.
Subject(s)
Androgens/pharmacology , Aromatase Inhibitors/toxicity , Chemokine CXCL12/metabolism , Gene Expression/drug effects , Receptors, CXCR4/metabolism , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cell Line, Tumor , Cell Movement/drug effects , Cell Proliferation/drug effects , Chemokine CXCL12/analysis , Chemokine CXCL12/genetics , Female , Humans , MCF-7 Cells , Nuclear Receptor Coactivator 1/antagonists & inhibitors , Nuclear Receptor Coactivator 1/genetics , Nuclear Receptor Coactivator 1/metabolism , Promoter Regions, Genetic , RNA Interference , Receptors, Androgen/metabolism , Receptors, CXCR4/antagonists & inhibitors , Receptors, CXCR4/genetics , Receptors, Estrogen/metabolism , Testosterone/pharmacology , Tumor Suppressor Protein p53/antagonists & inhibitors , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Up-Regulation/drug effectsABSTRACT
Accumulating evidence during the last decades revealed that androgen can exert membrane initiated actions that involve signaling via specific kinases and the modulation of significant cellular processes, important for prostate cancer cell growth and metastasis. Results of the present work clearly show that androgens can specifically act at the membrane level via the GPCR oxoeicosanoid receptor 1 (OXER1) in prostate cancer cells. In fact, OXER1 expression parallels that of membrane androgen binding in prostate cancer cell lines and tumor specimens, while in silico docking simulation of OXER1 showed that testosterone could bind to OXER1 within the same grove as 5-OxoETE, the natural ligand of OXER1. Interestingly, testosterone antagonizes the effects of 5-oxoETE on specific signaling pathways and rapid effects such as actin cytoskeleton reorganization that ultimately can modulate cell migration and metastasis. These findings verify that membrane-acting androgens exert specific effects through an antagonistic interaction with OXER1. Additionally, this interaction between androgen and OXER1, which is an arachidonic acid metabolite receptor expressed in prostate cancer, provides a novel link between steroid and lipid actions and renders OXER1 as new player in the disease. These findings should be taken into account in the design of novel therapeutic approaches in prostate cancer.
