Myofibroblast androgen receptor expression determines cell survival in co-cultures of myofibroblasts and prostate cancer cells in vitro

AR loss in prostate cancer stroma mediated by NF-κB and p38-MAPK signaling disrupts stromal morphogen production

Androgen Receptor (AR) activity in prostate stroma is required to maintain prostate homeostasis. This is mediated through androgen-dependent induction and secretion of morphogenic factors that drive epithelial cell differentiation. However, stromal AR expression is lost in aggressive prostate cancer. The mechanisms leading to stromal AR loss and morphogen production are unknown. We identified TGFβ1 and TNFα as tumor-secreted factors capable of suppressing AR mRNA and protein expression in prostate stromal fibroblasts. Pharmacological and RNAi approaches identified NF-κB as the major signaling pathway involved in suppressing AR expression by TNFα. In addition, p38α- and p38δ-MAPK were identified as suppressors of AR expression independent of TNFα. Two regions of the AR promoter were responsible for AR suppression through TNFα. FGF10 and Wnt16 were identified as androgen-induced morphogens, whose expression was lost upon TNFα treatment and enhanced upon p38-MAPK inhibition. Wnt16, through non-canonical Jnk signaling, was required for prostate basal epithelial cell survival. These findings indicate that stromal AR loss is mediated by secreted factors within the TME. We identified TNFα/TGFβ as two possible factors, with TNFα mediating its effects through NF-κB or p38-MAPK to suppress AR mRNA transcription. This leads to loss of androgen-regulated stromal morphogens necessary to maintain normal epithelial homeostasis.

Prognostic and therapeutic potential of senescent stromal fibroblasts in prostate cancer

The stromal component of the tumour microenvironment in primary and metastatic prostate cancer can influence and promote disease progression. Within the prostatic stroma, fibroblasts are one of the most prevalent cell types associated with precancerous and cancerous lesions; they have a vital role in the structural composition, organization and integrity of the extracellular matrix. Fibroblasts within the tumour microenvironment can undergo cellular senescence, which is a stable arrest of cell growth and a phenomenon that is emerging as a recognized hallmark of cancer. Supporting the idea that cellular senescence has a pro-tumorigenic role, a subset of senescent cells exhibits a senescence-associated secretory phenotype (SASP), which, along with increased inflammation, can promote prostate cancer cell growth and survival. These cellular characteristics make targeting senescent cells and/or modulating SASP attractive as a potential preventive or therapeutic option for prostate cancer.

Cancer Cell-Extrinsic Roles for the Androgen Receptor in Prostate Cancer

Given the central role of the androgen receptor (AR) in prostate cancer cell biology, AR-targeted therapies have been the backbone of prostate cancer treatment for over 50 years. New data indicate that AR is expressed in additional cell types within the tumor microenvironment. Moreover, targeting AR for the treatment of prostate cancer has established side effects such as bone complications and an increased risk of developing cardiometabolic disease, indicating broader roles for AR. With the advent of novel technologies, such as single-cell approaches and advances in preclinical modeling, AR has been identified to have clinically significant functions in other cell types. In this mini-review, we describe new cancer cell-extrinsic roles for AR within the tumor microenvironment as well as systemic effects that collectively impact prostate cancer progression and patient outcomes.

Fibroblasts as Turned Agents in Cancer Progression

Differentiated epithelial cells reside in the homeostatic microenvironment of the native organ stroma. The stroma supports their normal function, their G0 differentiated state, and their expansion/contraction through the various stages of the life cycle and physiologic functions of the host. When malignant transformation begins, the microenvironment tries to suppress and eliminate the transformed cells, while cancer cells, in turn, try to resist these suppressive efforts. The tumor microenvironment encompasses a large variety of cell types recruited by the tumor to perform different functions, among which fibroblasts are the most abundant. The dynamics of the mutual relationship change as the sides undertake an epic battle for control of the other. In the process, the cancer “wounds” the microenvironment through a variety of mechanisms and attracts distant mesenchymal stem cells to change their function from one attempting to suppress the cancer, to one that supports its growth, survival, and metastasis. Analogous reciprocal interactions occur as well between disseminated cancer cells and the metastatic microenvironment, where the microenvironment attempts to eliminate cancer cells or suppress their proliferation. However, the altered microenvironmental cells acquire novel characteristics that support malignant progression. Investigations have attempted to use these traits as targets of novel therapeutic approaches.

Cancer-Associated Fibroblast Heterogeneity, Activation and Function: Implications for Prostate Cancer

The continuous remodeling of the tumor microenvironment (TME) during prostate tumorigenesis is emerging as a critical event that facilitates cancer growth, progression and drug-resistance. Recent advances have identified extensive communication networks that enable tumor-stroma cross-talk, and emphasized the functional importance of diverse, heterogeneous stromal fibroblast populations during malignant growth. Cancer-associated fibroblasts (CAFs) are a vital component of the TME, which mediate key oncogenic events including angiogenesis, immunosuppression, metastatic progression and therapeutic resistance, thus presenting an attractive therapeutic target. Nevertheless, how fibroblast heterogeneity, recruitment, cell-of-origin and differential functions contribute to prostate cancer remains to be fully delineated. Developing our molecular understanding of these processes is fundamental to developing new therapies and biomarkers that can ultimately improve clinical outcomes. In this review, we explore the current challenges surrounding fibroblast identification, discuss new mechanistic insights into fibroblast functions during normal prostate tissue homeostasis and tumorigenesis, and illustrate the diverse nature of fibroblast recruitment and CAF generation. We also highlight the promise of CAF-targeted therapies for the treatment of prostate cancer.

The Role of Androgen Receptor in Cross Talk Between Stromal Cells and Prostate Cancer Epithelial Cells

Prostate cancer (PCa) lists as the second most lethal cancer for men in western countries, and androgen receptor (AR) plays a central role in its initiation and progression, which prompts the development of androgen deprivation therapy (ADT) as the standard treatment. Prostate tumor microenvironment, consisting of stromal cells and extracellular matrix (ECM), has dynamic interactions with PCa epithelial cells and affects their growth and invasiveness. Studies have shown that both genomic and non-genomic AR signaling pathways are involved in the biological regulation of PCa epithelial cells. In addition, AR signaling in prostate stroma is also involved in PCa carcinogenesis and progression. Loss of AR in PCa stroma is clinically observed as PCa progresses to advanced stage. Especially, downregulation of AR in stromal fibroblasts dysregulates the expression levels of ECM proteins, thus creating a suitable environment for PCa cells to metastasize. Importantly, ADT treatment enhances this reciprocal interaction and predisposes stromal cells to promote cell invasion of PCa cells. During this process, AR in PCa epithelium actively responds to various stimuli derived from the surrounding stromal cells and undergoes enhanced degradation while elevating the expression of certain genes such as MMP9 responsible for cell invasion. AR reduction in epithelial cells also accelerates these cells to differentiate into cancer stem-like cells and neuroendocrine cells, which are AR-negative PCa cells and inherently resistant to ADT treatments. Overall, understanding of the cross talk between tumor microenvironment and PCa at the molecular level may assist the development of novel therapeutic strategies against this disease. This review will provide a snapshot of AR's action when the interaction of stromal cells and PCa cells occurs.

Stereoselective Anti-Cancer Activities of Ginsenoside Rg3 on Triple Negative Breast Cancer Cell Models

Ginsenoside Rg3 (Rg3) has two epimers, 20(S)-ginsenoside Rg3 (SRg3) and 20(R)-ginsenoside Rg3 (RRg3), and while Rg3 itself has been reported to have anti-cancer properties, few studies have been reported on the anti-cancer effects of the different epimers. The aim was to investigate the stereoselective effects of the Rg3 epimers on triple negative breast cancer (TNBC) cell lines, tested using cell-based assays for proliferation, apoptosis, cell cycle arrest, migration and invasion. Molecular docking showed that Rg3 interacted with the aquaporin 1 (AQP1) water channel (binding score -9.4 kJ mol-1). The Xenopus laevis oocyte expression system was used to study the effect of Rg3 epimers on the AQP1 water permeability. The AQP1 expression in TNBC cell lines was compared with quantitative-polymerase chain reaction (PCR). The results showed that only SRg3 inhibited the AQP1 water flux and inhibited the proliferation of MDA-MB-231 (100 μM), due to cell cycle arrest at G0/G1. SRg3 inhibited the chemoattractant-induced migration of MDA-MB-231. The AQP1 expression in MDA-MB-231 was higher than in HCC1143 or DU4475 cell lines. These results suggest a role for AQP1 in the proliferation and chemoattractant-induced migration of this cell line. Compared to SRg3, RRg3 had more potency and efficacy, inhibiting the migration and invasion of MDA-MB-231. Rg3 has stereoselective anti-cancer effects in the AQP1 high-expressing cell line MDA-MB-231.

Steroid Receptor Signallings as Targets for Resveratrol Actions in Breast and Prostate Cancer

Extensive research over the past 25 years in hormone-dependent cancers, such as breast cancer and prostate cancer, has identified the molecular mechanisms driven by steroid receptors, elucidating the interplay between genomic and non-genomic steroid receptors mechanism of action. Altogether, these mechanisms create the specific gene expression programs that contribute to endocrine therapy resistance and cancer progression. These findings, on the bidirectional molecular crosstalk between steroid and growth factor receptors pathways in endocrine resistance, suggest the use of multi-target inhibitors together with endocrine therapies, for treating resistant disease. In this review we will discuss the novel understanding on the chemopreventive and anti-cancer activities of Resveratrol (3,5,4′-trihydroxy-stilbene) (RSV), a phytoalexin found in grapes acting on a plethora of targets. We will highlight Resveratrol effect on steroid receptors signalling and its potential use in the treatment of hormone-dependent cancer. Understanding the molecular mechanisms by which the bioactive compound influences cancer cell behaviour, by interfering with steroid receptors functional activity, will help to advance the design of combination strategies to increase the rate of complete and durable clinical response in patients.