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Figure S1: Production of eicosanoid species in tumor cell-adipocyte Transwell co-cultures and experimental bone tumors Figure S2. Bone marrow adipocyte numbers are increased in mice treated with Rosiglitazone (ROSI) and in genetically obese ob/ob mice. Figure S3. MCP-1 expression is induced in bone marrow adipocytes interacting with prostate tumor cells in vivo and in vitro. Figure S4. HFD and Rosiglitazone do not have significant effect on COX-2, mPGES and MCP-1 levels in subcutaneous tumors. Figure S5. IL-1b expression in experimental ARCaP(M) tumors and bone metastasis tissues from PCa patients. Figure S6. Tumor-induced adipocyte expression of mPGES and MCP-1 is sensitive to inhibition by IL-1RA.

Adipocyte–tumor cell cross-talk is one of the critical mediators of tumor progression and an emerging facilitator of therapy evasion. Tumor cells that metastasize to adipocyte-rich bone marrow take advantage of the interplay between metabolic and inflammatory pathways to activate prosurvival mechanisms that allow them to thrive and escape therapy. Using in vitro and in vivo models of marrow adiposity, we demonstrate that metastatic prostate carcinoma cells engage bone marrow adipocytes in a functional cross-talk that promotes IL1β expression in tumor cells. Tumor-supplied IL1β contributes to adipocyte lipolysis and regulates a proinflammatory phenotype in adipocytes via upregulation of COX-2 and MCP-1. We further show that the enhanced activity of the IL1β/COX-2/MCP-1 axis and a resulting increase in PGE2 production by adipocytes coincide with augmented hypoxia signaling and activation of prosurvival pathways in tumor cells, revealing a potential mechanism of chemoresistance. The major consequence of this interplay is the reduced response of prostate cancer cells to docetaxel, a phenomenon sensitive to the inhibition of lipolysis.Implications:Studies presented herein highlight adipocyte lipolysis as a tumor-regulated metabolic event that engages proinflammatory cross-talk in the microenvironment to promote prostate cancer progression in bone. Understanding the impact of bone marrow adipose tissue on tumor adaptation, survival, and chemotherapy response is fundamentally important, as current treatment options for metastatic prostate cancer are palliative.

We report the synthesis, photochemical and biological characterization of two new Ru(II) photoactivated complexes based on [Ru(tpy)(Me

Tumor associated macrophages (TAMs) suppress the cancer immune response and are a key target for immunotherapy. The effects of ruthenium and rhodium complexes on TAMs have not been well characterized. To address this gap in the field, a panel of 22 dirhodium and ruthenium complexes were screened against three subtypes of macrophages, triple-negative breast cancer and normal breast tissue cells. Experiments were carried out in 2D and biomimetic 3D co-culture experiments with and without irradiation with blue light. Leads were identified with cell-type-specific toxicity toward macrophage subtypes, cancer cells, or both. Experiments with 3D spheroids revealed complexes that sensitized the tumor models to the chemotherapeutic doxorubicin. Cell surface exposure of calreticulin, a known facilitator of immunogenic cell death (ICD), was increased upon treatment, along with a concomitant reduction in the M2-subtype classifier arginase. Our findings lay a strong foundation for the future development of ruthenium- and rhodium-based chemotherapies targeting TAMs.

Highlights • Mouse prostate cancer Myc-CaP cells readily form bone tumors in FVB/NJ mice. • Tumors are grossly confined to bone after intraosseous injection. • Myc-CaP bone tumors have a mixed osteolytic/osteosclerotic morphology. • Syngeneic Myc-CaP tumors model key aspects of prostate cancer bone metastases., Prostate cancer (PCa) metastasis research has been hamstrung by lack of animal models that closely resemble the disease present in most patients – that metastasize to bone, are dependent on the androgen receptor (AR), and grow in an immune competent host. Here, we adapt the Myc-CaP cell line for use as a PCa androgen dependent, immune competent bone metastases model and characterize the metastases. After injection into the left cardiac ventricle of syngeneic FVB/NJ mice, these cells formed bone metastases in the majority of animals; easily visible on H&E sections and confirmed by immunohistochemistry for Ar and epithelial cell adhesion molecule. Mediastinal tumors were also observed. We also labeled Myc-CaP cells with tdTomato, and confirmed the presence of cancer cells in bone by flow cytometry. To adapt the model to a bone predominant metastasis pattern and further examine the bone phenotype, we labeled the cells with luciferase, injected in the tibia and observed tumor formation only in tibia with a mixed osteolytic/osteoblastic phenotype. The presence of Myc-CaP tumors significantly increased tibia bone volume as compared to sham injected controls. The osteoclast marker, TRAcP-5b was not significantly changed in plasma from tibial tumor bearing animals vs. sham animals. However, conditioned media from Myc-CaP cells stimulated osteoclast formation in vitro from FVB/NJ mouse bone marrow. Overall, Myc-CaP cells injected in the left ventricle or tibia of syngeneic mice recapitulate key aspects of human metastatic PCa.

A critical unknown in the field of skeletal metastases is how cancer cells find a way to thrive under harsh conditions, as exemplified by metastatic colonization of adipocyte-rich bone marrow by prostate carcinoma cells. To begin understanding molecular processes that enable tumor cells to survive and progress in difficult microenvironments such as bone, we performed unbiased examination of the transcriptome of two different prostate cancer cell lines in the absence or presence of bone marrow adipocytes. Our RNAseq analyses and subsequent quantitative PCR and protein-based assays reveal that upregulation of endoplasmic reticulum (ER) stress and unfolded protein response (UPR) genes is a shared signature between metastatic prostate carcinoma cell lines of different origin. Pathway analyses and pharmacological examinations highlight the ER chaperone BIP as an upstream coordinator of this transcriptomic signature. Additional patient-based data support our overall conclusion that ER stress and UPR induction are shared, important factors in the response and adaptation of metastatic tumor cells to their micro-environment. Our studies pave the way for additional mechanistic investigations and offer new clues towards effective therapeutic interventions in metastatic disease.

Purpose This study aimed to evaluate a combination of radiation therapy (RT), androgen deprivation therapy (ADT), and pexidartinib (colony-stimulating factor 1 receptor [CSF1R]) inhibitor in men with intermediate- and high-risk prostate cancer. CSF1R signaling promotes tumor infiltration and survival of tumor-associated macrophages, which in turn promote progression and resistance. Counteracting protumorigenic actions of tumor-associated macrophages via CSF1R inhibition may enhance therapeutic efficacy of RT and ADT for prostate cancer. Methods and Materials In this phase 1 study, the treatment regimen consisted of pexidartinib (800 mg, administered as a split-dose twice daily) and ADT (both for a total of 6 months), and RT that was initiated at the start of month 3. RT volumes included the prostate and proximal seminal vesicles. The delivered dose was 7920 cGy (180 cGy per fraction) using intensity modulated RT with daily image guidance for prostate localization. The primary objective was to identify the maximum tolerated dose based on dose-limiting toxicities. Results All 4 enrolled patients who were eligible to receive RT had T1 stage prostate cancer, 2 were intermediate risk, and 2 were high risk. The median age was 62.5 years, and the prostate-specific antigen levels were in the range 6.4 to 10.7 ng/mL. The patients’ individual Gleason scores were 3 + 3, 4 + 3, 4 + 4, and 4 + 5. All 4 patients reported ≥1 adverse events before RT. Grade 1 hypopigmentation was observed in 1 patient, and grade 3 pulmonary embolus in another. One patient experienced fatigue and joint pain, and another elevated amylase and pruritus (all grade 3 toxicities). Five of the 6 adverse events noted in 3 patients were all grade 3 toxicities attributable to pexidartinib, qualifying as dose-limiting toxicities and ultimately resulting in the study closure. Conclusions The combination was not well tolerated and does not warrant further investigation in men with intermediate- and high-risk prostate cancer.

Bone is a site of metastasis from several tumor types including prostate cancer (PCa). Metastatic PCa is lethal, largely due to the complex nature of bone microenvironment, and the functional cross-talk between bone-resident cells and tumor cells that favors therapy evasion. We have shown previously that age- and obesity-induced changes in the bone microenvironment, specifically increased marrow adiposity, promote tumor adaptation in bone. Numerous studies have also linked the disruption in bone homeostasis with aggressive tumor phenotype. Whether environmental toxicants with propensity to accumulate in bone can modulate bone microenvironment to support tumor growth and progression is, however, not known. Per- and polyfluoroalkyl substances (PFAS) are “forever” chemicals with very long half-lives and ability to accumulate in bone. Limited reports have linked PFAS exposure with adipocyte differentiation and osteoclast activation, but their specific effects on bone are not known. It is also unclear whether the exposure to PFAS can directly impact metastatic tumor cells. Here, we hypothesized that PFAS contribute to metastatic progression by impacting both the tumor and its microenvironment. Specifically, we aimed to establish that exposure to PFAS promotes adipogenesis and osteoclastogenesis, creating microenvironment conducive to tumor growth. We also sought to determine whether direct effects of PFAS exposure on tumor cells lead to activation of growth and survival signaling that drives aggressive phenotype in bone. Our data show that 12-week exposure of mice to a cocktail of 5 PFAS chemicals (PFOS, PFOA, PFNA, PFHxS, and GenX) increases the number of adipocytes in the tibia and augments expression of adipogenesis-associated genes, such as FABP4 and adiponectin. RNAseq analyses of tibia from mice exposed to PFAS chemicals for 3 and 6 weeks indicate changes in bone metabolism and turnover, results supported by in vitro osteoclastogenesis assays. Mass spectrometry analyses of bone extracts from PFAS cocktail exposed mice reveal that the compound with highest concentration in bone is PFHxS. Interestingly, our in vitro assays employing bone marrow derived mesenchymal cells show that PFHxS can activate peroxisome proliferator-activated receptor (PPAR) signaling, leading to an increase in adipogenesis. Studies examining the direct impact of long term PFHxS as well as PFAS cocktail exposure on in vitro PCa cultures and progression of intratibially implanted PCa tumors are currently ongoing. Our findings to date indicate that changes in bone marrow microenvironment induced by PFAS chemicals have a potential to disrupt the balance between osteoblasts and adipocytes, promote marrow adipogenesis and osteoclastogenesis, and activate specific signaling pathways in tumor cells that support growth and survival. Citation Format: Laimar C. Garmo, Mackenzie K. Herroon, Shane Mecca, Alexis Wilson, Michael C. Petriello, Izabela Podgorski. Effects of per- and polyfluoroalkyl substances on bone marrow adipose environment: Potential implications for bone metastatic cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6318.

Metastatic tumor cells engage the local tumor microenvironment and activate specific pro-survival mechanisms to thrive and progress in the harsh bone marrow niche. Here we show that the major contributors to the survival of carcinoma cells that have colonized the bone marrow are the adipocyte-induced oxidative stress and ER stress pathways. We demonstrate that upon exposure to adipocyte-rich environments in vitro or in vivo, bone-trophic prostate and breast tumor cells upregulate the oxidative stress enzyme, HO-1. We also show that HO-1 levels are significantly increased in human metastatic prostate cancer tissues and that stable HO-1 overexpression in tumor cells promotes growth and invasiveness. Co-incident with the adipocyte-induced expression of HO-1, there is an upregulation of ER chaperone BIP and splicing of XBP1, indicating adipocyte-driven unfolded protein response, a process that we show to be sensitive to antioxidant treatment. Importantly, we also demonstrate that triggering of the oxidative stress and ER stress responses, or HO-1 induction by adipocyte exposure result in the activation of pro-survival pathways, involving survivin. Collectively, our findings reveal a new link between HO-1 and survivin expression in tumor cells, and provide a new insight into potentially targetable survival pathways in bone-metastatic disease.

Adipocyte–tumor cell cross-talk is one of the critical mediators of tumor progression and an emerging facilitator of therapy evasion. Tumor cells that metastasize to adipocyte-rich bone marrow take advantage of the interplay between metabolic and inflammatory pathways to activate prosurvival mechanisms that allow them to thrive and escape therapy. Using in vitro and in vivo models of marrow adiposity, we demonstrate that metastatic prostate carcinoma cells engage bone marrow adipocytes in a functional cross-talk that promotes IL1β expression in tumor cells. Tumor-supplied IL1β contributes to adipocyte lipolysis and regulates a proinflammatory phenotype in adipocytes via upregulation of COX-2 and MCP-1. We further show that the enhanced activity of the IL1β/COX-2/MCP-1 axis and a resulting increase in PGE2 production by adipocytes coincide with augmented hypoxia signaling and activation of prosurvival pathways in tumor cells, revealing a potential mechanism of chemoresistance. The major consequence of this interplay is the reduced response of prostate cancer cells to docetaxel, a phenomenon sensitive to the inhibition of lipolysis. Implications: Studies presented herein highlight adipocyte lipolysis as a tumor-regulated metabolic event that engages proinflammatory cross-talk in the microenvironment to promote prostate cancer progression in bone. Understanding the impact of bone marrow adipose tissue on tumor adaptation, survival, and chemotherapy response is fundamentally important, as current treatment options for metastatic prostate cancer are palliative.

// Jonathan D. Diedrich 1,3 , Erandi Rajagurubandara 1 , Mackenzie K. Herroon 1 , Gargi Mahapatra 2 , Maik Huttemann 1,2 and Izabela Podgorski 1,3 1 Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA 2 Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI, USA 3 Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, USA Correspondence to: Izabela Podgorski, email: // Keywords : bone marrow adipocytes, bone metastasis, prostate cancer, glycolysis, Warburg effect Received : August 15, 2016 Accepted : August 21, 2016 Published : August 30, 2016 Abstract Metabolic adaptation is increasingly recognized as a key factor in tumor progression, yet its involvement in metastatic bone disease is not understood. Bone is as an adipocyte-rich organ, and a major site of metastasis from prostate cancer. Bone marrow adipocytes are metabolically active cells capable of shaping tumor metabolism via lipolysis and lipid transfer. In this study, using in vitro and in vivo models of marrow adiposity, we demonstrate that marrow fat cells promote Warburg phenotype in metastatic prostate cancer cells. We show increased expression of glycolytic enzymes, increased lactate production, and decreased mitochondrial oxidative phosphorylation in tumor cells exposed to adipocytes that require paracrine signaling between the two cell types. We also reveal that prostate cancer cells are capable of inducing adipocyte lipolysis as a postulated mechanism of sustenance. We provide evidence that adipocytes drive metabolic reprogramming of tumor cells via oxygen-independent mechanism of HIF-1α activation that can be reversed by HIF-1α downregulation. Importantly, we also demonstrate that the observed metabolic signature in tumor cells exposed to adipocytes mimics the expression patterns seen in patients with metastatic disease. Together, our data provide evidence for a functional relationship between marrow adipocytes and tumor cells in bone that has likely implications for tumor growth and survival within the metastatic niche.

Collagenolytic activity of cathepsin K is important for many physiological and pathological processes including osteoclast-mediated bone degradation, macrophage function and fibroblast-mediated matrix remodeling. Here, we report application of a light-activated inhibitor for controlling activity of cathepsin K in a 3D functional imaging assay. Using prostate carcinoma cell line engineered to overexpress cathepsin K, we demonstrate the utility of the proteolytic assay in living tumor spheroids for the evaluation and quantification of the inhibitor effects on cathepsin K-mediated collagen I degradation. Importantly, we also show that utilizing the ruthenium-caged version of a potent nitrile cathepsin K inhibitor (4), cis-[Ru(bpy)2(4)2](BF4)2 (5), offers significant advantage in terms of effective concentration of the inhibitor and especially its light-activated control in the 3D assay. Our results suggest that light activation provides a suitable, attractive approach for spatial and temporal control of proteolytic activity, which remains a critical, unmet need in treatment of human diseases, especially cancer.

Dual action agents containing a cysteine protease inhibitor and Rubased photosensitizer for photodynamic therapy (PDT) were designed, synthesized, and validated in 2D culture and 3D functional imaging assays of triple-negative human breast cancer (TNBC). These combination agents deliver and release Rubased PDT agents to tumor cells and cause cancer cell death upon irradiation with visible light, while at the same time inactivating cathespin B (CTSB), a cysteine protease strongly associated with invasive and metastatic behavior. In total five Rubased complexes were synthesized with the formula [Ru(bpy)(2)(l)](O(2)CCF(3))(2) (3), where bpy = 2,2′-bipyridine and 1 = a bipyridine-based epoxysuccinyl inhibitor; [Ru(tpy)(NN)(2)](PF(6))(2), where tpy = terpiridine, 2 = a pyridine-based epoxysuccinyl inhibitor and NN = 2,2′-bipyridine (4); 6,6′-dimethyl-2,2′-bipyridine (5); benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine (6); and 3,6-dimethylbenzo[i]-dipyrido[3,2-a:2′,3′ -c]phenazine (7). Compound 3 contains a [Ru(bpy)(3)](2+) fluorophore and was designed to track the subcellular localization of the conjugates, whereas compounds 4–7 were designed to undergo either photoactivated ligand dissociation and/or singlet oxygen generation. Photochemical studies confirmed that complexes 5 and 7 undergo photoactivated ligand dissociation, whereas 6 and 7 generate singlet oxygen. Inhibitors 1–7 all potently and irreversibly inhibit CTSB. Compounds 4–7 were evaluated against MDA-MB-231 TNBC and MCF-10A breast epithelial cells in 2D and 3D culture for effects on proteolysis and cell viability under dark and light conditions. Collectively, these data reveal that 4–7 potently inhibit dye-quenched (DQ) collagen degradation, whereas only compound 7 causes efficient cell death under light conditions, consistent with its ability to release a Ru(II)-based photosensitizer and to also generate (1)O(2).

PURPOSE OF REVIEW: Bone marrow adipocytes have emerged in recent years as key contributors to metastatic progression in bone. In this review, we focus specifically on their role as the suppliers of lipids and discuss pro-survival pathways that are closely linked to lipid metabolism, affected by the adipocyte-tumor cell interactions, and likely impacting the ability of the tumor cell to thrive in bone marrow space and evade therapy. RECENT FINDINGS: The combined in silico, pre-clinical, and clinical evidence shows that in adipocyte-rich tissues such as bone marrow, tumor cells rely on exogenous lipids for regulation of cellular energetics and adaptation to harsh metabolic conditions of the metastatic niche. Adipocyte-supplied lipids have a potential to alter the cell’s metabolic decisions by regulating glycolysis and respiration, fatty acid oxidation, lipid desaturation, and PPAR signaling. The downstream effects of lipid signaling on mitochondrial homeostasis ultimately control life vs. death decisions, providing a mechanism for gaining survival advantage and reduced sensitivity to treatment. SUMMARY: There is a need for future research directed towards identifying the key metabolic and signaling pathways that regulate tumor dependence on exogenous lipids and consequently drive the pro-survival behavior in the bone marrow niche.

Light-activated inhibition of cathepsin activity was demonstrated in a cell-based assay. Inhibitors of cathepsin K, Cbz-Leu-NHCH2 CN (2) and Cbz-Leu-Ser(OBn)-CN (3), were caged within the complexes cis-[Ru(bpy)2 (2)2 ]Cl2 (4) and cis-[Ru(bpy)2 (3)2 ](BF4 )2 (5) (bpy=2,2'-bipyridine) as 1:1 mixtures of Δ and Λ stereoisomers. Complexes 4 and 5 were characterized by (1) H NMR, IR, and UV/Vis spectroscopies and electrospray mass spectrometry. Photochemical experiments confirm that 4 releases two molecules of 2 upon exposure to visible light for 15 min, whereas release of 3 by 5 requires longer irradiation times. IC50 determinations against purified cathepsin K under light and dark conditions with 4 and 5 confirm that inhibition is enhanced from 35- to 88-fold, respectively, upon irradiation with visible light. No apparent toxicity was observed for 4 in the absence or presence of irradiation in bone marrow macrophage (BMM) or PC3 cells, as determined by MTT assays, at concentrations up to 10 μM. Compound 5 is well tolerated at lower concentrations (1 μM), but does show growth-inhibitory effects at higher concentrations. Confocal microscopy experiments show that 4 decreases intracellular cathepsin activity in osteoclasts with light activation. These results support the further development of caged nitrile-based inhibitors as chemical tools for investigating spatial aspects of proteolysis within living systems.

Incidence of skeletal metastases and death from prostate cancer greatly increases with age and obesity, conditions which increase marrow adiposity. Bone marrow adipocytes are metabolically active components of bone metastatic niche that modulate the function of neighboring cells; yet the mechanisms of their involvement in tumor behavior in bone have not been explored. In this study, using experimental models of intraosseous tumor growth and diet-induced obesity, we demonstrate the promoting effects of marrow fat on growth and progression of skeletal prostate tumors. We reveal that exposure to lipids supplied by marrow adipocytes induces expression of lipid chaperone FABP4, pro-inflammatory interleukin IL-1β, and oxidative stress protein HMOX-1 in metastatic tumor cells and stimulates their growth and invasiveness. We show that FABP4 is highly overexpressed in prostate skeletal tumors from obese mice and in bone metastasis samples from prostate cancer patients. In addition, we provide results suggestive of bi-directional interaction between FABP4 and PPARγ pathways that may be driving aggressive tumor cell behavior in bone. Together, our data provide evidence for functional relationship between bone marrow adiposity and metastatic prostate cancers and unravel the FABP4/IL-1β axis as a potential therapeutic target for this presently incurable disease.

Adipocytes are a major component of the bone marrow that can critically affect metastatic progression in bone. Understanding how the marrow fat cells influence growth, behavior, and survival of tumor cells requires utilization of in vitro cell systems that can closely mimic the physiological microenvironment. Herein, we present two new three-dimensional (3D) culture approaches to study adipocyte–tumor cell interactions in vitro. The first is a transwell-based system composed of the marrow-derived adipocytes in 3D collagen I gels and reconstituted basement membrane-overlayed prostate tumor cell spheroids. Tumor cells cultured under these 3D conditions are continuously exposed to adipocyte-derived factors, and their response can be evaluated by morphological and immunohistochemical analyses. We show via immunofluorescence analysis of metabolism-associated proteins that under 3D conditions tumor cells have significantly different metabolic response to adipocytes than tumor cells grown in 2D culture. We also demonstrate that this model allows for incorporation of other cell types, such as bone marrow macrophages, and utilization of dye-quenched collagen substrates for examination of proteolysis-driven responses to adipocyte- and macrophage-derived factors. Our second 3D culture system is designed to study tumor cell invasion toward the adipocytes and the consequent interaction between the two cell types. In this model, marrow adipocytes are separated from the fluorescently labeled tumor cells by a layer of collagen I. At designated time points, adipocytes are stained with BODIPY and confocal z-stacks are taken through the depth of the entire culture to determine the distance traveled between the two cell types over time. We demonstrate that this system can be utilized to study effects of candidate factors on tumor invasion toward the adipocytes. We also show that immunohistochemical analyses can be performed to evaluate the impact of direct interaction of prostate tumor cells with adipocytes. Our models underline the importance of using the appropriate culture conditions to mimic physiological interactions between marrow adipocytes and metastatic tumor cells. These systems have a potential to be utilized for analyses of various factors that may be regulated by the adipocytes in bone. Their application likely extends beyond metastatic prostate cancer to other tumors that colonize the bone marrow microenvironment.

Bone marrow macrophages (BMMs) share common progenitors with osteoclasts and are critical components of bone-tumor microenvironment; however, their function in prostate tumor growth in the skeleton has not been explored. BMMs are the major source of inflammatory factors and proteases, including cysteine protease cathepsin K (CTSK). In this study, utilizing mice deficient in CTSK, we demonstrate the critical involvement of this potent collagenase in tumor progression in bone. We present the evidence that tumor growth and progression in the bone are impaired in the absence of CTSK. Most importantly, we show for the first time that BMM-supplied CTSK may be involved in CCL2- and COX-2-driven pathways that contribute to tumor progression in bone. Together, our data unravel novel roles for CTSK in macrophage-regulated processes, and provide evidence for close interplay between inflammatory, osteolytic and tumor cell-driven events in the bone-tumor microenvironment.

Bone metastasis is a hallmark of advanced prostate and breast cancers, yet the critical factors behind attraction of tumors to the skeleton have not been validated. Here, we investigated the involvement of cathepsin K in the progression of prostate tumors in the bone, which occurs both by direct degradation of bone matrix collagen I and by cleavage of other factors in the bone microenvironment. Our results demonstrated that bone marrow-derived cathepsin K is capable of processing and thereby modulating SPARC, a protein implicated in bone metastasis and inflammation. The coincident up-regulation of SPARC and cathepsin K occurred both in vivo in experimental prostate bone tumors, and in vitro in co-cultures of bone marrow stromal cells with PC3 prostate carcinoma cells. PC3-bone marrow stromal cell interaction increased secretion and processing of SPARC, as did co-cultures of bone marrow stromal cells with two other cancer cell lines. In addition, bone marrow stromal cells that were either deficient in cathepsin K or treated with cathepsin K inhibitors had significantly reduced secretion and cleavage of SPARC. Increases in secretion of pro-inflammatory cytokines (ie, interleukin-6, -8) coincident with overexpression of cathepsin K suggest possible mechanisms by which this enzyme contributes to tumor progression in the bone. This is the first study implicating bone marrow cathepsin K in regulation of biological activity of SPARC in bone metastasis.

Three complexes of the general formula [Ru(TPA)L2](PF6)2 [TPA = tris(2-pyridylmethyl)amine], where L = pyridine (1), nicotinamide (2), and imidazole (3), were prepared and characterized spectroscopically. X-ray crystallographic data were obtained for 1 and 3. Complexes 1–3 show strong absorption in the visible region and selective release of heterocycles upon irradiation with visible light. Time-dependent density functional theory calculations are consistent with the presence of singlet metal-to-ligand charge-transfer bands in the visible region in 1–3. Caged heterocycles 1–3 are highly stable in solution in the dark, including in cell growth media. Cell viability data show no signs of toxicity of 1–3 against PC-3 cells at concentrations up to 100 μM under light and dark conditions, consistent with Ru(TPA) acting as a nontoxic and effective photocaging group for aromatic heterocycles.

Increased bone marrow adiposity is a common feature of advanced age, obesity and associated metabolic pathologies. Augmented numbers of marrow adipocytes positively correlate with dysregulated bone remodeling, also a well-established complication of metastatic disease. We have shown previously that marrow adiposity accelerates prostate tumor progression in the skeleton and promotes extensive destruction of the bone; however, the factors behind adipocyte-driven osteolysis in the skeletal tumor microenvironment are not currently known. In this study, utilizing in vivo diet-induced models of bone marrow adiposity, we reveal evidence for positive correlation between increased marrow fat content, bone degradation by ARCaP(M) and PC3 prostate tumors, and augmented levels of host-derived CXCL1 and CXCL2, ligands of CXCR2 receptor. We show by in vitro osteoclastogenesis assays that media conditioned by bone marrow adipocytes is a significant source of CXCL1 and CXCL2 proteins. We also demonstrate that both the adipocyte-conditioned media and the recombinant CXCL1 and CXCL2 ligands efficiently accelerate osteoclast maturation, a process that can be blocked by neutralizing antibodies to each of the chemokines. We further confirm the contribution of CXCR2 signaling axis to adiposity-driven osteoclastogenesis by blocking fat cell-induced osteoclast differentiation with CXCR2 antagonist or neutralizing antibodies. Together, our results link CXCL1 and CXCL2 chemokines with bone marrow adiposity and implicate CXCR2 signaling in promoting effects of marrow fat on progression of skeletal tumors in bone.

Bone is a preferential site of metastasis from prostate cancer (PCa). Age and obesity, conditions that increase adipocyte numbers in bone marrow, are risk factors for skeletal metastases from PCa. Research in our laboratory focuses on understanding the interactions between adipocytes and tumor cells that have infiltrated the bone marrow. Specifically, we are examining how the secretion, transport, and uptake of adipocyte-supplied factors promote metastatic progression in bone. We have previously shown that bone marrow adipocytes enhance a glycolytic phenotype in PCa cells through paracrine activation of glycolytic enzymes GLUT1, HK2, PDK1, ENO2, and LDHa at both the mRNA and protein levels. This correlated with an increase in glycolytic activity as measured by higher levels of lactate secretion and decreases in oxidative phosphorylation, indicative of an enhanced Warburg-like metabolic signature. We then assessed HIF-1a activity through mRNA analysis of HIF-1a target genes carbonic anhydrase 9 (CA9) and vascular endothelial growth factor (VEGF). We found that CA9 and VEGF had elevated expression levels in tumor cells exposed to adipocytes, indicative of enhanced HIF-1a activity. Notably, PCa cells exposed to bone marrow adipocytes had significantly enhanced presence of HIF-1a in the nucleus, result further confirming HIF-1α, activation in tumor cells exposed to marrow adipocytes. Hypoxia chamber experiments revealed that these effects were observable regardless of the presence or absence of oxygen, indicating the presence of oxygen-independent HIF-1a signaling or a state of pseudohypoxia in tumor cells. These results were further validated in multiple in vitro cell culture and in vivo mouse models, where an increased production of both glycolytic genes and HIF-1α target genes was shown to correlate with marrow adiposity. Our overall hypothesis is that bone marrow adipocyte-supplied lipids within the bone microenvironment cause HIF-1a activation and metabolic switch to glycolysis in metastatic PCa cells in bone, leading to their increased aggressiveness and resistance to therapy. Citation Format: Jonathan Diedrich, Erandi Rajagurubandara, Mackenzie Herroon, Izabela Podgorski. Bone marrow adipocytes alter the metabolic phenotype of metastatic prostate cancer cells through the activation of HIF-1a. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-315.

A novel method for caging protease inhibitors is described. The complex [Ru(II)(bpy)(2)(1)(2)](PF(6))(2) (2) was prepared from the nitrile-based peptidomimetic inhibitor Ac-Phe-NHCH(2)CN (1). (1)H NMR, UV-vis, and IR spectroscopic and mass spectrometric data confirmed that 2 equiv of inhibitor 1 bind to Ru(II) through the nitrile functional group. Complex 2 shows excellent stability in aqueous solution in the dark and fast release of 1 upon irradiation with visible light. As a result of binding to the Ru(II) center, the nitriles of complex 2 are caged, and 2 does not act as a potent enzyme inhibitor. However, when 2 is irradiated, it releases 1, which inhibits the cysteine proteases papain and cathepsins B, K and L up to 2 times more potently than 1 alone. Ratios of the IC(50) values in the dark versus in the light ranged from 6:1 to 33:1 for inhibition by 2 against isolated enzymes and in human cell lysates, confirming that a high level of photoinduced enzyme inhibition can be obtained using this method.

Bone is a very common site of metastasis from prostate cancer (PCa). Over 70% of PCa patients after radical prostatectomy show evidence of disseminated tumor cells in their bone marrow and more than 80% of patients with recurrent PCa have signs of skeletal disease. Despite numerous advancements that have been made in detection and treatment of PCa in the recent years, there has been no measurable improvement in outcome for men with metastatic disease. To design effective therapies for this devastating and incurable disease we need to understand the molecular mechanisms that drive tumor cell adaptation and survival in the bone metastatic niche. Adipocytes are a major component of bone marrow stroma and their numbers greatly increase with age and obesity. They are metabolically active cells with specialized functions of storing and secreting fatty acids and adipokines, and influencing neighboring cells by a number of mechanisms. We have shown recently that marrow adiposity is an important factor in adaptation and progression of PCa tumors in the bone marrow microenvironment. Our data demonstrated that growth and invasion of PCa cells in vitro and in vivo is driven by lipid trafficking between bone marrow adipocytes and cancer cells and involves upregulation of lipid transporter fatty acid binding protein 4 (FABP4), pro-inflammatory interleukin IL1β, and oxidative stress protein Heme Oxygenase, a process that can be blocked by FABP4 inhibition. We have also shown that FABP4 expression is high in xenograft and patient prostate bone metastasis tissues and that its interaction with PPARγ is a potential driving mechanism of metastatic tumor growth in bone. Our present investigations are based on the hypothesis that metastatic tumor cells in the bone have to adapt their metabolism to take advantage of available sources of energy provided by the host cells. Using in vitro co-culture systems of marrow adipocytes with prostate tumor cells we demonstrate that tumor cells utilize fatty acids generated by adipocyte-driven lipolysis to sustain their growth and invasiveness. Stimulation of adipocyte lipolysis with β3-adrenergic receptor agonist isoproterenol leads to further increase in FABP4 and IL1β expression in tumor cells, a result confirming involvement of those two factors in adipocyte-driven behavior in bone. Examination of RNA and protein expression of acetyl-CoA carboxylase (ACC) and carnitine palmitoyltransferase 1 (CPT1) reveals adaptation of tumor lipid metabolism via modulation of β-oxidation pathways. In addition, our results show that tumor cells upregulate their own monoacylglycerol lipase (MAGL), result suggesting lipid remodeling by tumor cells. Collectively our results demonstrate that bone marrow adipocytes serve as energy source for metastatic PCa cells. Lipidomic analyses and studies utilizing adipocyte-specific deletion of lipolytic enzymes such as ATGL are currently ongoing. These studies have a potential to reveal how marrow adipocytes influence prostate tumor metabolism and lead to unraveling of unique therapeutic targets for treatment of this presently incurable metastatic disease. Citation Format: Mackenzie K. Herroon, Erandi Rajagurubandara, Aimalie L. Hardaway, Izabela Podgorski. Exploring the roles of bone marrow adipocytes in metabolic adaptation of metastatic prostate tumors in bone. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B04. doi:10.1158/1538-7445.CHTME14-B04

Prostate cancer (PCa) is the second leading cause of cancer-related deaths among men. Although PCa is slow to progress, patients eventually develop metastases at distant sites, predominantly bone. Once established in the bone marrow, PCa becomes a devastating and incurable disease. The emerging evidence suggests that overweight and obesity are associated with shorter time to disease recurrence and poor patient survival. One major consequence of obesity is the accumulation of adipocytes within the bone marrow, a process which we have previously shown to accelerate tumor progression in the skeletal sites. We demonstrated that prostate tumor cells exposed to bone marrow adipocyte-derived factors (Adipo CM) exhibit lipid accumulation, increased invasiveness, and changes in cell morphology that promote an invasive phenotype. We have also shown that increased marrow adiposity results in augmented levels of tumor-promoting inflammatory factors in bone. Therefore, in the present study, we investigated the effects of adiposity on bone marrow macrophage (BMM) function, phenotype, and differentiation to mature osteoclasts. Utilizing a co-culture system of BMMs and PCa cells, we demonstrate that BMMs exposed to Adipo CM have increased expression and secretion of osteopontin (OPN), a key regulator of macrophage function that has been implicated in prostate tumor progression. We also observed that BMMs are more invasive toward PCa cells exposed to Adipo CM. Our studies show that IL-10 expression, a chemokine regulated by OPN, is suppressed in BMMs co-cultured with Adipo CM and PCa cells. Conversely, arginase-1 and CD163, markers of M2 macrophage phenotype, are highly induced by macrophage-tumor cell interactions. Our results suggest a direct role for OPN in regulation of BMM phenotype in the bone-tumor microenvironment. Furthermore, our investigations of adiposity-driven bone remodeling in tumor progression in bone reveal that adipocyte-derived factors accelerate BMM differentiation into osteoclasts as evidenced by TRAcP staining, overexpression of osteoclastogenesis-associated genes, and increased proteolytic cleavage of DQ-collagen I. Utilizing functional fluorescence-based assays and western blotting approaches we also show that expression and proteolytic activity of cathepsin K, a bone-degrading cysteine protease, is upregulated in osteoclasts differentiating in the presence of Adipo CM. This further supports the involvement of adipocyte-derived factors in tumor-induced bone disease. In summary, our work highlights novel roles of adipocyte-derived factors in macrophage function, behavior, and osteoclastogenesis in the bone marrow niche. Studies are currently underway to determine how lipid uptake affects their function and tumor-promoting activities in bone. Citation Format: Aimalie Lynnette Hardaway, Mackenzie K. Herroon, Erandi N. Rajagurubandara, Izabela Podgorski. Investigating the role of bone marrow adiposity on macrophage function and osteoclast differentiation. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A18. doi:10.1158/1538-7445.CHTME14-A18

Prostate cancer (PCa) is the second leading cause of cancer deaths among men in the United States. Obesity, adipocyte-derived signals, and adipose tissue inflammation are major contributors to development of aggressive PCa, with higher recurrence and higher mortality rates. Bone is a primary site of metastasis of PCa and obese and overweight men have a three-fold higher risk of progression to metastatic disease compared to normal-weight men receiving the same treatment. Experimental and clinical evidence indicate that bone marrow adipocyte numbers increase with age and obesity and their increased presence affects homeostasis in the bone microenvironment. It is not, however, currently known how adipocyte-derived factors influence tumor growth and survival in bone. Heme oxygenase 1 (HO-1) is a stress-responsive protein induced by hypoxia and inflammation, and it has been shown to play a role in prostate carcinogenesis and cell survival. Its role in tumor cell aggressiveness and survival in response to adipocyte-derived signals has not been previously explored. Here, we investigated the effects of bone marrow adipocyte-derived factors on HO-1/IL-1α pathway in PCa cells. Our study was driven by hypothesis that adipocytes increase invasiveness and survival of PCa cells via upregulation of HO-1. We utilized Taqman RT PCR analyses and western blotting approaches to demonstrate that levels of HO-1 and its inducer IL-1α increase in PC3, DU145 and C42B prostate cancer cell lines in response to treatment with adipocyte conditioned media (Adipo CM). Immunofluorescence analyses and subcellular fractionation methods were used to demonstrate a translocation of HO-1 from the cytoplasm to nucleus upon exposure to Adipo CM. Invasiveness of PCa cells in response to adipocyte-derived factors in the absence and presence of IL-1α neutralizing antibody and HO-1 inhibitor Zinc protoporphyrin IX was assessed using Boyden chamber assays. Studies are currently underway to determine the significance of HO-1/IL-1α upregulation in tumor cells survival and response to chemotherapy. Collectively, the results of our studies demonstrate that adipocyte-induced upregulation of HO-1/IL-1α pathways may be playing a significant role in promoting prostate tumor aggressiveness and survival. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1489. doi:1538-7445.AM2012-1489