The consequences of prostate cancer metastasis remain severe, with huge impact on the mortality and overall quality of life of affected patients. Despite the convoluted interplay and cross talk between various cell types and secreted factors in the metastatic process, cytokine and chemokines, along with their receptors and signaling axis, constitute important factors that help drive the sequence of events that lead to metastasis of prostate cancer. These proteins are involved in extracellular matrix remodeling, epithelial-mesenchymal-transition, angiogenesis, tumor invasion, premetastatic niche creation, extravasation, re-establishment of tumor cells in secondary organs as well as the remodeling of the metastatic tumor microenvironment. This review presents an overview of the main cytokines/chemokines, including IL-6, CXCL12, TGFβ, CXCL8, VEGF, RANKL, CCL2, CX3CL1, IL-1, IL-7, CXCL1, and CXCL16, that exert modulatory roles in prostate cancer metastasis. We also provide extensive description of their aberrant expression patterns in both advanced disease states and metastatic sites, as well as their functional involvement in the various stages of the prostate cancer metastatic process.

Abstract Prostate cancer (PCa) is a leading cause of cancer death among men, with greater prevalence of the disease among the African American population in the USA. Activator of G-protein signaling 3 (AGS3/G-protein signaling modulator 1) was shown to be overexpressed in prostate adenocarcinoma relative to the prostate gland. In this study, we investigated the correlation between AGS3 overexpression and PCa malignancy. Immunoblotting analysis and real-time quantitative-PCR showed increase in AGS3 expression in the metastatic cell lines LNCaP (~3-fold), MDA PCa 2b (~2-fold), DU 145 (~2-fold) and TRAMP-C1 (~20-fold) but not in PC3 (~1-fold), relative to control RWPE-1. Overexpression of AGS3 in PC3, LNCaP and MDA PCa 2b enhanced tumor growth. AGS3 contains seven tetratricopeptide repeats (TPR) and four G-protein regulatory (GPR) motifs. Overexpression of the TPR or the GPR motifs in PC3 cells had no effect in tumor growth. Depletion of AGS3 in the TRAMP-C1 cells (TRAMP-C1-AGS3-/-) decreased cell proliferation and delayed wound healing and tumor growth in both C57BL/6 (~3-fold) and nude mice xenografts, relative to control TRAMP-C1 cells. TRAMP-C1-AGS3-/- tumors also exhibited a marked increase (~5-fold) in both extracellular signal-regulated kinase (ERK) 1/2 and P38 mitogen-activated protein kinase (MAPK) activation, which correlated with a significant increase (~3-fold) in androgen receptor (AR) expression, relative to TRAMP-C1 xenografts. Interestingly, overexpression of AGS3 in TRAMP-C1-AGS3-/- cells inhibited ERK activation and AR overexpression as compared with control TRAMP-C1 cells. Taken together, the data indicate that the effect of AGS3 in prostate cancer development and progression is probably mediated via a MAPK/AR-dependent pathway.

Abnormal expression of microRNA miR-214-3p (miR-214) is associated with multiple cancers. In this study, we assessed the effects of CRISPR/Cas9 mediated miR-214 depletion in prostate cancer (PCa) cells and the underlying mechanisms. Knockdown of miR-214 promoted PCa cell proliferation, invasion, migration, epithelial-mesenchymal transition (EMT), and increased resistance to anoikis, a key feature of PCa cells that undergo metastasis. The reintroduction of miR-214 in miR-214 knockdown cells reversed these effects and significantly suppressed cell proliferation, migration, and invasion. These in vitro studies are consistent with the role of miR-214 as a tumor suppressor. Moreover, miR-214 knockout increased tumor growth in PCa xenografts in nude mice supporting its anti-oncogenic role in PCa. Knockdown of miR-214 increased the expression of its target protein, Protein Tyrosine Kinase 6 (PTK6), a kinase shown to promote oncogenic signaling and tumorigenesis in PCa. In addition, miR-214 modulated EMT as exhibited by differential regulation of E-Cadherin, N-Cadherin, and Vimentin both in vitro and in vivo. RNA-seq analysis of miR-214 knockdown cells revealed altered gene expression related to PCa tumor growth pathways, including EMT and metastasis. Collectively, our findings reveal that miR-214 is a key regulator of PCa oncogenesis and is a potential novel therapeutic target for the treatment of the disease.

Prostate cancer constitutes a serious health challenge and remains one of the main causes of cancer-related death among men. The more aggressive form of the disease has been attributed to androgen independence; resulting in lack of response to androgen deprivation therapy and sustained activation of other growth pathways. The scaffold proteins β-arrestin 1 and 2 (βarr1 and βarr2) which are known to mediate G protein-coupled receptor desensitization and internalization, were also shown to modulate prostate tumorigenesis. βarr1 is significantly overexpressed (>4 fold) in prostate cancer cells relative to βarr2. In this study, we investigated the effect of βarr1 overexpression in prostate cancer development and progression using the mouse and human PCa cell xenografts, and autochthonous transgenic adenocarcinoma mouse prostate (TRAMP) models deficient in β-arrestins Depletion of βarr1 in TRAMP mice (TRAMP/βarr1 -/-) increased PCa growth and decreased overall survival relative to control TRAMP or TRAMP/βarr2 -/- animals. Prostate tissues from TRAMP/βarr1 -/- tumors displayed an increase in androgen receptor expression whereas overexpression of βarr1 in TRAMP-C1 (TRAMP-C1-βarr1-GFP) which derived from TRAMP decreased AR expression, cell proliferation and tumor growth in nude mice xenografts, relative to control TRAMP-C1-GFP. Knockdown of βarr1 expression in human MDA PCa 2b cells (MDA PCa 2b-βarr1 -/-) also decreased AR expression cell proliferation and tumor growth relative to control (MDA PCa 2b-Sham) cells. Interestingly, both TRAMP-C1-βarr1-GFP and MDA PCa 2b-βarr1 -/- xenografts showed a decrease in AKT phosphorylation, but an increase MAPK activation. Altogether, the data indicate that the effect of βarr1 in modulating AR signaling to regulate prostate cancer aggressiveness is cell and host autonomous.

Ginger active components are widely known for being a potent antioxidant and recently as a potential anticancer agent. [6]-Gingerol, the most abundant and pungent bioactive component of ginger, was shown to inhibit angiogenesis and tumorigenesis in xenograph models of both prostate cancer (PCa) and melanoma. To date, the precise mechanism(s) for the antitumor effect of ginger is not well understood. The adaptor proteins, β-arrestins, have been shown to modulate tumor development and metastasis in both PCa and melanoma. In this study, we sought to determine the role of [6]-gingerol in β-arrestin (βarr) 1 and 2-mediated PCa and melanoma development, progression, and metastasis. To that end, the PCa cells PC-3 and the melanoma B16-F10 cells were treated with different concentrations of [6]-gingerol for 48 hours. Cell lysates were assayed by Western blot analysis for βarr-1 and βarr-2, CXCR1, and CXCR2 expression, as well as MAP kinase and transcription factors activation. The data demonstrated that pretreatment with [6]-gingerol caused a dose-dependent inhibition of βarr-2, but not βarr-1, in both cell lines, which correlated with significant decrease in Akt and NF-κB activation. [6]-Gingerol pretreatment decreased CXCR1 and CXCR2 expression, CXCL-8-induced intracellular calcium mobilization; and delayed wound closure. [6]-Gingerol exposure also decreased PC-3 and B16 metastasis in zebrafish. Altogether the data indicated that the protective effect of [6]-gingerol in tumorigenesis is likely mediated via a βarr-2-dependent mechanism. Citation Format: Tonelia A. Mowart, Timothy Adekoya, Nikia Smith, Tonya S. Lane, Ricardo M. Richardson. Ginger consumption inhibits β-arrestin-2 expression and functions in melanoma and prostate cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B005.

Prostate cancer (PCa) is a leading cause of cancer death among men, with greater prevalence of the disease among the African American population in the US. AGS3, a receptor-independent activator of G-protein signaling has been shown to affect different cellular processes and cell cycle activity. The aim of this study is to assess the role of AGS3 on the development and progression of prostate cancer as well as to understand the molecular dynamics involved. Preliminary results indicate a differential in the level of expression of AGS3 in PCa cells with the African American cell line (MDA PCa 2b) expressing high amount of AGS3 while the Caucasian cell lines (PC3 and LNCAP) do not. Overexpression of AGS3 in PC3 augmented tumor development in nude mice xenografts whereas depletion of AGS3 in MDA PCa 2b decreased tumor size. Interestingly, a xenograft model of Lewis Lung Carcinoma (LLC) cells in AGS3 conditional knockout (AGS3−/−) mice resulted in a significant increase in tumor progression when compared with the wild-type (AGS3+/+) mice. Taken together, these results indicate that AGS3 expression modulates tumor development and progression and may play a role in PCa health disparity.

Chemokines and their receptors are important proteins that promote growth of various malignant tumors. In prostate cancer, some members of the CXC chemokine receptor have been shown to enhance angiogenesis, proliferation and metastasis. In this study we assess the roles of the interleukin-8 (IL-8/CXCL8) receptors CXCR1 and CXCR2 in prostate cancer development, using the African American MDA PCa 2b cell line. Our results show that overexpression of CXCR2 enhanced in-vitro cell proliferation, soft agar growth and in-vivo tumor xenograft in nude mice, whereas overexpression of CXCR1 inhibited cell proliferation and tumor growth, relative to control cells. Interestingly, cells overexpressing CXCR1 exhibited a more mesenchymal phenotype, characterized by reduced E-Cadherin but increased N-Cadherin and vimentin protein expression. CXCR1 overexpression also blocked AKT activation and signal transduction. CXCR2 overexpression, however, resulted in a neuroendocrine phenotype, characterized by reduced androgen (AR) receptor expression and altered chromogranin A expression. In conclusion, these results indicate that CXCR1 and CXCR2 overexpression may play alternate roles on prostate tumorigenesis. Citation Format: Timothy O. Adekoya, Nikia Smith, Parag Kothari, Ricardo M. Richardson. Differential effects of CXCR1 and CXCR2 receptors on prostate tumorigenesis [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-134.

Activator of G-protein Signaling 3 (AGS3) is a receptor-independent activator of G-protein signaling which comprises seven tetratricopeptide (TPR) motifs and four GPR motifs joined by a linker sequence. Previous studies have demonstrated that the TPR domain of AGS3 is important for determining the positioning of AGS3 within the cell, whereas the GPR domain serves as a docking site for Gαi-GDP leading to AGS3-Gαi signaling. We have recently shown that GRK6 complexes with AGS3-Gαi to regulate CXCR2-mediated cellular functions including Ca2+ mobilization, mitogen-activated protein kinase (MAPK) activation, receptor desensitization and down-regulation. In the current study, mutants from the GPR and TPR domains were used to determine which motif(s) of AGS3 interact with GRK6 to modulate CXCR2-mediated inflammatory responses. Co-immunoprecipitation studies in transiently transfected HEK 293 cells, and RBL-2H3 cells stably expressing wild-type and mutants AGS3 demonstrated that interleukin 8 (IL-8/CXCL8) activation increases GRK6 interaction with the GPR domain not the TPR. Interestingly, the TPR motif displayed a robust agonist-independent association with GRK6 which was prevented by CXCL8 activation of the receptor. Overexpression of AGS3 and the GPR motif, not the TPR, inhibited CXCR2 mediated intracellular Ca2+ mobilization and MAPK activation. Taken together, these results indicate that GRK6 interacts with the GPR domain of AGS3 to modulate CXCR2/Gai interaction and signal transduction.