ABSTRACT
A hallmark of prostate cancer progression is dysregulation of lipid metabolism via overexpression of fatty acid synthase (FASN), a key enzyme in de novo fatty acid synthesis. Metastatic castration-resistant prostate cancer (mCRPC) develops resistance to inhibitors of androgen receptor (AR) signaling through a variety of mechanisms, including the emergence of the constitutively active AR variant V7 (AR-V7). Here, we developed an FASN inhibitor (IPI-9119) and demonstrated that selective FASN inhibition antagonizes CRPC growth through metabolic reprogramming and results in reduced protein expression and transcriptional activity of both full-length AR (AR-FL) and AR-V7. Activation of the reticulum endoplasmic stress response resulting in reduced protein synthesis was involved in IPI-9119-mediated inhibition of the AR pathway. In vivo, IPI-9119 reduced growth of AR-V7-driven CRPC xenografts and human mCRPC-derived organoids and enhanced the efficacy of enzalutamide in CRPC cells. In human mCRPC, both FASN and AR-FL were detected in 87% of metastases. AR-V7 was found in 39% of bone metastases and consistently coexpressed with FASN. In patients treated with enzalutamide and/or abiraterone FASN/AR-V7 double-positive metastases were found in 77% of cases. These findings provide a compelling rationale for the use of FASN inhibitors in mCRPCs, including those overexpressing AR-V7.
Subject(s)
Lipogenesis , Neoplasm Proteins/metabolism , Prostatic Neoplasms, Castration-Resistant/metabolism , Receptors, Androgen/metabolism , Signal Transduction , Animals , Cell Line, Tumor , Enzyme Inhibitors/pharmacology , Fatty Acid Synthase, Type I/antagonists & inhibitors , Fatty Acid Synthase, Type I/genetics , Fatty Acid Synthase, Type I/metabolism , Humans , Male , Mice , Neoplasm Metastasis , Neoplasm Proteins/antagonists & inhibitors , Neoplasm Proteins/genetics , Prostatic Neoplasms, Castration-Resistant/drug therapy , Prostatic Neoplasms, Castration-Resistant/genetics , Prostatic Neoplasms, Castration-Resistant/pathology , Receptors, Androgen/genetics , Xenograft Model Antitumor AssaysABSTRACT
The hypoxic environment is a crucial component of the cancer stem cell niche and it is capable of eliciting stem cell features in cancer cells. We previously reported that SNAI2 up-regulates the expression of Carbonic Anhydrase iso-enzyme 9 (CA9) in hypoxic MCF7 cells. Here we show that SNAI2 down-regulates miR34a expression in hypoxic MCF7 cell-derived mammospheres. Next, we report on the capability of miR34a to decrease CA9 mRNA stability and CA9 protein expression. We also convey that the over-expression of cloned CA9-mRNA-3'UTR increases the mRNA half-life and protein levels of two miR34a targets JAGGED1 and NOTCH3. The data here reported shows that the SNAI2-dependent down-regulation of miR34a substantially contributes to the post-transcriptional up-regulation of CA9, and that CA9-mRNA-3'UTR acts as an endogenous microRNA sponge. We conclude that CA9/miR34 interplay shares in the hypoxic regulation of mammospheres and therefore, may play a relevant role in the hypoxic breast cancer stem cell niche.
Subject(s)
Antigens, Neoplasm/biosynthesis , Breast Neoplasms/genetics , Carbonic Anhydrases/biosynthesis , Cell Hypoxia/genetics , MicroRNAs/genetics , Antigens, Neoplasm/genetics , Breast Neoplasms/pathology , Calcium-Binding Proteins/biosynthesis , Carbonic Anhydrase IX , Carbonic Anhydrases/genetics , Female , Gene Expression Regulation, Neoplastic , Humans , Hypoxia/genetics , Intercellular Signaling Peptides and Proteins/biosynthesis , Jagged-1 Protein , MCF-7 Cells , Membrane Proteins/biosynthesis , MicroRNAs/biosynthesis , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/pathology , Receptor, Notch3 , Receptors, Notch/biosynthesis , Serrate-Jagged Proteins , Snail Family Transcription Factors , Transcription Factors/biosynthesisABSTRACT
Hypoxia has been long-time acknowledged as major cancer-promoting microenvironment. In such an energy-restrictive condition, post-transcriptional mechanisms gain importance over the energy-expensive gene transcription machinery. Here we show that the onset of hypoxia-induced cancer stem cell features requires the beta-catenin-dependent post-transcriptional up-regulation of CA9 and SNAI2 gene expression. In response to hypoxia, beta-catenin moves from the plasma membrane to the cytoplasm where it binds and stabilizes SNAI2 and CA9 mRNAs, in cooperation with the mRNA stabilizing protein HuR. We also provide evidence that the post-transcriptional activity of cytoplasmic beta-catenin operates under normoxia in basal-like/triple-negative breast cancer cells, where the beta-catenin knockdown suppresses the stem cell phenotype in vitro and tumor growth in vivo. In such cells, we unravel the generalized involvement of the beta-catenin-driven machinery in the stabilization of EGF-induced mRNAs, including the cancer stem cell regulator IL6. Our study highlights the crucial role of post-transcriptional mechanisms in the maintenance/acquisition of cancer stem cell features and suggests that the hindrance of cytoplasmic beta-catenin function may represent an unprecedented strategy for targeting breast cancer stem/basal-like cells.
Subject(s)
ELAV Proteins/metabolism , Hypoxia/genetics , Hypoxia/metabolism , Neoplastic Stem Cells/metabolism , RNA Processing, Post-Transcriptional , beta Catenin/metabolism , 3' Untranslated Regions , Animals , Antigens, Neoplasm/genetics , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Carbonic Anhydrase IX , Carbonic Anhydrases/genetics , Cell Dedifferentiation/genetics , Cell Line, Tumor , Cell Nucleus/metabolism , Cell Proliferation , Cell Survival/genetics , Disease Models, Animal , Epidermal Growth Factor/metabolism , Female , Gene Expression , Gene Knockdown Techniques , Heterografts , Humans , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , Mice , Neoplastic Stem Cells/pathology , Phenotype , RNA Stability , RNA, Messenger/genetics , RNA, Messenger/metabolism , Ribosome Subunits, Small, Eukaryotic/metabolism , Snail Family Transcription Factors , Transcription Factors/genetics , Transcription, Genetic , Triple Negative Breast Neoplasms/genetics , Triple Negative Breast Neoplasms/metabolismABSTRACT
BACKGROUND: Basal-like carcinoma are aggressive breast cancers that frequently carry p53 inactivating mutations, lack estrogen receptor-α (ERα) and express the cancer stem cell markers CD133 and CD44. These tumors also over-express Interleukin 6 (IL-6), a pro-inflammatory cytokine that stimulates the growth of breast cancer stem/progenitor cells. RESULTS: Here we show that p53 deficiency in breast cancer cells induces a loss of methylation at IL-6 proximal promoter region, which is maintained by an IL-6 autocrine loop. IL-6 also elicits the loss of methylation at the CD133 promoter region 1 and of CD44 proximal promoter, enhancing CD133 and CD44 gene transcription. In parallel, IL-6 induces the methylation of estrogen receptor (ERα) promoter and the loss of ERα mRNA expression. Finally, IL-6 induces the methylation of IL-6 distal promoter and of CD133 promoter region 2, which harbour putative repressor regions. CONCLUSION: We conclude that IL-6, whose methylation-dependent autocrine loop is triggered by the inactivation of p53, induces an epigenetic reprogramming that drives breast carcinoma cells towards a basal-like/stem cell-like gene expression profile.