Ablating Lgr5-expressing prostatic stromal cells activates the ERK-mediated mechanosensory signaling and disrupts prostate tissue homeostasis

Meta-analyses of mouse and human prostate single-cell transcriptomes reveal widespread epithelial plasticity in tissue regression, regeneration, and cancer

BACKGROUND

Despite extensive analysis, the dynamic changes in prostate epithelial cell states during tissue homeostasis as well as tumor initiation and progression have been poorly characterized. However, recent advances in single-cell RNA-sequencing (scRNA-seq) technology have greatly facilitated studies of cell states and plasticity in tissue maintenance and cancer, including in the prostate.

METHODS

We have performed meta-analyses of new and previously published scRNA-seq datasets for mouse and human prostate tissues to identify and compare cell populations across datasets in a uniform manner. Using random matrix theory to denoise datasets, we have established reference cell type classifications for the normal mouse and human prostate and have used optimal transport to compare the cross-species transcriptomic similarities of epithelial cell populations. In addition, we have integrated analyses of single-cell transcriptomic states with copy number variants to elucidate transcriptional programs in epithelial cells during human prostate cancer progression.

RESULTS

Our analyses demonstrate transcriptomic similarities between epithelial cell states in the normal prostate, in the regressed prostate after androgen-deprivation, and in primary prostate tumors. During regression in the mouse prostate, all epithelial cells shift their expression profiles toward a proximal periurethral (PrU) state, demonstrating an androgen-dependent plasticity that is restored to normal during androgen restoration and gland regeneration. In the human prostate, we find substantial rewiring of transcriptional programs across epithelial cell types in benign prostate hyperplasia and treatment-naïve prostate cancer. Notably, we detect copy number variants predominantly within luminal acinar cells in prostate tumors, suggesting a bias in their cell type of origin, as well as a larger field of transcriptomic alterations in non-tumor cells. Finally, we observe that luminal acinar tumor cells in treatment-naïve prostate cancer display heterogeneous androgen receptor (AR) signaling activity, including a split between AR-positive and AR-low profiles with similarity to PrU-like states.

CONCLUSIONS

Taken together, our analyses of cellular heterogeneity and plasticity provide important translational insights into the origin and treatment response of prostate cancer. In particular, the identification of AR-low tumor populations suggests that castration-resistance and predisposition to neuroendocrine differentiation may be pre-existing properties in treatment-naïve primary tumors that are selected for by androgen-deprivation therapies.

Unveiling LGR5: Prostate cancer's hidden stem cell and treatment target

Prostate cancer poses a significant risk to the well-being and way of life of countless men, with an increased likelihood of relapse recorded following modern treatment. This highlights the need for innovative approaches, specifically targeting LGR5. This systematic review aims to establish a connection between LGR5 and the various signaling pathways involved in the progression of prostate cancer. LGR5, a gene targeted by Wnt signaling, encodes a receptor protein that serves as a prognostic biomarker for stem cells and indicates the presence of cancer stem cells in colorectal and gastrointestinal cancers. The functions of LGR5 include processes such as cell proliferation, differentiation, and signaling pathways. Any modifications to the LGR5 gene, whether caused by mutations or mechanical stimuli, can lead to the development of treatment-resistant stem cell cancers. This review examines the molecular mechanisms associated with LGR5 and emphasizes methodologies aimed at targeting LGR5 to enhance understanding and promote the development of LGR5-specific therapies.

Meta-analyses of mouse and human prostate single-cell transcriptomes reveal widespread epithelial plasticity in tissue regression, regeneration, and cancer

Recent advances in single-cell RNA-sequencing (scRNA-seq) technology have facilitated studies of cell states and plasticity in tissue maintenance and cancer, including in the prostate. Here we present meta-analyses of multiple new and published scRNA-seq datasets to establish reference cell type classifications for the normal mouse and human prostate. Our analyses demonstrate transcriptomic similarities between epithelial cell states in the normal prostate, in the regressed prostate after androgen-deprivation, and in primary prostate tumors. During regression in the mouse prostate, all epithelial cells shift their expression profiles towards a proximal periurethral (PrU) state, demonstrating an androgen-dependent plasticity that is restored to normal during androgen restoration and regeneration. In the human prostate, we find progressive rewiring of transcriptional programs across epithelial cell types in benign prostate hyperplasia and treatment-naïve prostate cancer. Notably, we detect copy number variants predominantly within Luminal Acinar cells in prostate tumors, suggesting a bias in their cell type of origin, as well as a larger field of transcriptomic alterations in non-tumor cells. Finally, we observe that Luminal Acinar tumor cells in treatment-naïve prostate cancer display heterogeneous androgen receptor (AR) signaling activity, including a split between high-AR and low-AR profiles with similarity to PrU-like states. Taken together, our analyses of cellular heterogeneity and plasticity provide important translational insights into the origin and treatment response of prostate cancer.

Emerging roles and mechanisms of ERK pathway mechanosensing

The coupling between mechanical forces and modulation of cell signalling pathways is essential for tissue plasticity and their adaptation to changing environments. Whilst the number of physiological and pathological relevant roles of mechanotransduction has been rapidly expanding over the last decade, studies have been mostly focussing on a limited number of mechanosensitive pathways, which include for instance Hippo/YAP/TAZ pathway, Wnt/β-catenin or the stretch-activated channel Piezo. However, the recent development and spreading of new live sensors has provided new insights into the contribution of ERK pathway in mechanosensing in various systems, which emerges now as a fast and modular mechanosensitive pathway. In this review, we will document key in vivo and in vitro examples that have established a clear link between cell deformation, mechanical stress and modulation of ERK signalling, comparing the relevant timescale and mechanical stress. We will then discuss different molecular mechanisms that have been proposed so far, focussing on the epistatic link between mechanics and ERK and discussing the relevant cellular parameters affecting ERK signalling. We will finish by discussing the physiological and the pathological consequences of the link between ERK and mechanics, outlining how this interplay is instrumental for self-organisation and long-range cell-cell coordination.

Androgen-regulated stromal complement component 7 (C7) suppresses prostate cancer growth

The complement system is a major component of the innate immune system that works through the cytolytic effect of the membrane attack complex (MAC). Complement component 7 (C7) is essential for MAC assembly and its precisely regulated expression level is crucial for the cytolytic activity of MAC. We show that C7 is specifically expressed by the stromal cells in both mouse and human prostates. The expression level of C7 inversely correlates with clinical outcomes in prostate cancer. C7 is positively regulated by androgen signaling in the mouse prostate stromal cells. The androgen receptor directly transcriptionally regulates the mouse and human C7. Increasing C7 expression in the C57Bl/6 syngeneic RM-1 and Pten-Kras allografts suppresses tumor growth in vivo. Conversely, C7 haploinsufficiency promotes tumor growth in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Interestingly, replenishing C7 in androgen-sensitive Pten-Kras tumors during androgen depletion only slightly enhances cellular apoptosis, highlighting the diverse mechanisms employed by tumors to counteract complement activity. Collectively, our research indicates that augmenting complement activity could be a promising therapeutic approach to impede the development of castration resistance in prostate cancer.

Stromal FOXF2 suppresses prostate cancer progression and metastasis by enhancing antitumor immunity

Cancer-associated fibroblasts (CAFs) mediate an immunosuppressive effect, but the underlying mechanism remains incompletely defined. Here we show that increasing prostatic stromal Foxf2 suppresses the growth and progression of both syngeneic and autochthonous mouse prostate cancer models in an immunocompetent context. Mechanistically, Foxf2 moderately attenuates the CAF phenotype and transcriptionally downregulates Cxcl5, which diminish the immunosuppressive myeloid cells and enhance T cell cytotoxicity. Increasing prostatic stromal Foxf2 sensitizes prostate cancer to the immune checkpoint blockade therapies. Augmenting lung stromal Foxf2 also mediates an immunosuppressive milieu and inhibits lung colonization of prostate cancer. FOXF2 is expressed higher in the stroma of human transition zone (TZ) than peripheral zone (PZ) prostate. The stromal FOXF2 expression level in primary prostate cancers inversely correlates with the Gleason grade. Our study establishes Foxf2 as a stromal transcription factor modulating the tumor immune microenvironment and potentially explains why cancers are relatively rare and indolent in the TZ prostate.