Paracrine factors produced by bone marrow stromal cells induce apoptosis and neuroendocrine differentiation in prostate cancer cells

Bone Marrow Endothelial Cells Increase Prostate Cancer Cell Apoptosis in 3D Triculture Model of Reactive Stroma

Simple Summary

Prostate cancer (PCa) metastasizes preferentially to the bone marrow where it becomes difficult to treat. PCa cells in the bone marrow may survive, dormant and undetected for many years before patients eventually relapse with metastatic disease. Bone marrow is a complex tissue that initially is hostile to the PCa cells, Understanding how cancer cells survive in the bone marrow and what changes to the bone microenvironment permit them to switch to an actively growing state could offer new therapeutic strategies to combat metastatic PCa. In this study, we describe a method to culture PCa cells with two other cell types from the bone marrow, stromal cells and endothelial cells, as a way to study the interactions among these cell types. We found that factors produced by bone marrow endothelial cells, but not endothelial cells from other tissues, trigger PCa cells to either die or enter a dormant state, similar to what has been observed in patients when PCa cells initially colonize the bone marrow. Further analysis of the cell interactions within the culture model described in this study will offer increased understanding of PCa interaction with the bone marrow environment.

Abstract

The bone marrow tumor microenvironment (BMTE) is a complex network of cells, extracellular matrix, and sequestered signaling factors that initially act as a hostile environment for disseminating tumor cells (DTCs) from the cancerous prostate. Three-dimensional (3D) culture systems offer an opportunity to better model these complex interactions in reactive stroma, providing contextual behaviors for cancer cells, stromal cells, and endothelial cells. Using a new system designed for the triculture of osteoblastic prostate cancer (PCa) cells, stromal cells, and microvascular endothelial cells, we uncovered a context-specific pro-apoptotic effect of endothelial cells of the bone marrow different from those derived from the lung or dermis. The paracrine nature of this effect was demonstrated by observations that conditioned medium from bone marrow endothelial cells, but not from dermal or lung endothelial cells, led to PCa cell death in microtumors grown in 3D BMTE-simulating hydrogels. Analysis of the phosphoproteome by reverse phase protein analysis (RPPA) of PCa cells treated with conditioned media from different endothelial cells identified the differential regulation of pathways involved in proliferation, cell cycle regulation, and apoptosis. The findings from the RPPA were validated by western blotting for representative signaling factors identified, including forkhead box M1 (FOXM1; proliferation factor), pRb (cell cycle regulator), and Smac/DIABLO (pro-apoptosis) among treatment conditions. The 3D model presented here thus presents an accurate model to study the influence of the reactive BMTE, including stromal and endothelial cells, on the adaptive behaviors of cancer cells modeling DTCs at sites of bone metastasis. These findings in 3D culture systems can lead to a better understanding of the real-time interactions among cells present in reactive stroma than is possible using animal models.

Berbamine Inhibits Cell Proliferation and Migration and Induces Cell Death of Lung Cancer Cells via Regulating c-Maf, PI3K/Akt, and MDM2-P53 Pathways

Berbamine (BBM) is a natural product isolated from Berberis amurensis Rupr. We investigated the influence of BBM on the cell viability, proliferation, and migration of lung cancer cells and explored the possible mechanisms. The cell viability and proliferation of lung cancer cells were evaluated by MTT assay, EdU assay, and colony formation assay. Migration and invasion abilities of cancer cells were determined through wound scratch assay and Transwell assay. Cell death was evaluated by cell death staining assay and ELISA. The expressions of proteins were evaluated using western blot assay. A xenograft mouse model derived from non-small-cell lung cancer cells was used to detect the effect of BBM on tumor growth and metastasis in vivo. Both colony formation and EdU assays results revealed that BBM (10 μM) significantly inhibited the proliferation of A549 cells (P < 0.001). BBM (10 μM) also significantly inhibited the migration and invasion ability of cancer cells in wound scratch and Transwell assays. Trypan blue assay and ELISA revealed that BBM (20 μM) significantly induced cell death of A549 cells. In xenograft mouse models, the tumor volume was significantly smaller in mice treated with BBM (20 mg/kg). The western blotting assay showed that BBM inhibited the PI3K/Akt and MDM2-p53 signaling pathways, and BBM downregulated the expression of c-Maf. Our results show that BBM inhibits proliferation and metastasis and induces cell death of lung cancer cells in vitro and in vivo. These effects may be achieved by BBM reducing the expression of c-Maf and regulating the PI3K/Akt and MDM2-p53 pathways.

Possible treatment for UVB-induced skin injury: Anti-inflammatory and cytoprotective role of metformin in UVB-irradiated keratinocytes

BACKGROUND

Excessive inflammation and cell death induced by ultraviolet (UV) cause skin photodamage. Metformin possesses anti-inflammatory and cytoprotective effects. However, whether metformin inhibits inflammation and cell death in UVB-induced acute skin damage is unclear.

OBJECTIVE

To evaluate the anti-inflammatory and cytoprotective effects of metformin in vitro and in vivo. Furthermore, its potential mechanism has been explored.

METHODS

Transcriptome sequencing and multiplex cytokines analysis were used to evaluate the validity of in vitro UVB-induced acute damage keratinocyte model and anti-inflammatory effects of metformin. We also determined the expression and nuclear translocation of CCAAT/enhancer-binding protein beta (C/EBPβ), an important transcriptional factor of Interleukin-1beta (IL-1β). Cell viability and cell death of keratinocytes were evaluated upon UVB irradiation in the presence or absence of metformin. 0.6% metformin cream was applied on UVB-irradiated mice to explore its pharmacological effects in vivo.

RESULTS

Transcriptional landscape of 50 mJ/cm² UVB-irradiated HaCaT cells is typical of UVB-induced acute damage keratinocyte model in vitro. Metformin alleviated transcription and secretion of IL-1β, Tumor Necrosis Factor-alpha, and Fibroblast Growth Factor 2, expression and nuclear translocation of C/EBPβ in this model. Metformin also protected keratinocytes from cell death caused by UVB-induced cellular secretions, which contributed to its cytoprotective effects. Topical administration of 0.6% metformin cream alleviated UVB-induced skin damage in mice.

CONCLUSION

We proved the protective roles of metformin in UVB-challenged keratinocytes and UVB-irradiated mice, which indicated the potential value of metformin in topical therapy against skin photodamage.

Chronic IL-1 exposure drives LNCaP cells to evolve androgen and AR independence

Chronic inflammation promotes prostate cancer (PCa) initiation and progression. We previously reported that acute intereluekin-1 (IL-1) exposure represses androgen receptor (AR) accumulation and activity, providing a possible mechanism for IL-1-mediated development of androgen- and AR-independent PCa. Given that acute inflammation is quickly resolved, and chronic inflammation is, instead, co-opted by cancer cells to promote tumorigenicity, we set out to determine if chronic IL-1 exposure leads to similar repression of AR and AR activity observed for acute IL-1 exposure and to determine if chronic IL-1 exposure selects for androgen- and AR-independent PCa cells. We generated isogenic sublines from LNCaP cells chronically exposed to IL-1α or IL-1β. Cells were treated with IL-1α, IL-1β, TNFα or HS-5 bone marrow stromal cells conditioned medium to assess cell viability in the presence of cytotoxic inflammatory cytokines. Cell viability was also assessed following serum starvation, AR siRNA silencing and enzalutamide treatment. Finally, RNA sequencing was performed for the IL-1 sublines. MTT, RT-qPCR and western blot analysis show that the sublines evolved resistance to inflammation-induced cytotoxicity and intracellular signaling and evolved reduced sensitivity to siRNA-mediated loss of AR, serum deprivation and enzalutamide. Differential gene expression reveals that canonical AR signaling is aberrant in the IL-1 sublines, where the cells show constitutive PSA repression and basally high KLK2 and NKX3.1 mRNA levels and bioinformatics analysis predicts that pro-survival and pro-tumorigenic pathways are activated in the sublines. Our data provide evidence that chronic IL-1 exposure promotes PCa cell androgen and AR independence and, thus, supports CRPCa development.

Potent Activity of an Anti-ICAM1 Antibody-Drug Conjugate against Multiple Myeloma

PURPOSE

New therapies have changed the outlook for patients with multiple myeloma, but novel agents are needed for patients who are refractory or relapsed on currently approved drug classes. Novel targets other than CD38 and BCMA are needed for new immunotherapy development, as resistance to daratumumab and emerging anti-BCMA approaches appears inevitable. One potential target of interest in myeloma is ICAM1. Naked anti-ICAM1 antibodies were active in preclinical models of myeloma and safe in patients, but showed limited clinical efficacy. Here, we sought to achieve improved targeting of multiple myeloma with an anti-ICAM1 antibody-drug conjugate (ADC).

EXPERIMENTAL DESIGN

Our anti-ICAM1 human mAb was conjugated to an auristatin derivative, and tested against multiple myeloma cell lines in vitro, orthotopic xenografts in vivo, and patient samples ex vivo. The expression of ICAM1 was also measured by quantitative flow cytometry in patients spanning from diagnosis to the daratumumab-refractory state.

RESULTS

The anti-ICAM1 ADC displayed potent anti-myeloma cytotoxicity in vitro and in vivo. In addition, we have verified that ICAM1 is highly expressed on myeloma cells and shown that its expression is further accentuated by the presence of bone marrow microenvironmental factors. In primary samples, ICAM1 is differentially overexpressed on multiple myeloma cells compared with normal cells, including daratumumab-refractory patients with decreased CD38. In addition, ICAM1-ADC showed selective cytotoxicity in multiple myeloma primary samples.

CONCLUSIONS

We propose that anti-ICAM1 ADC should be further studied for toxicity, and if safe, tested for clinical efficacy in patients with relapsed or refractory multiple myeloma.

Proteoglycans in the Pathogenesis of Hormone-Dependent Cancers: Mediators and Effectors

Hormone-dependent cancers exhibit high morbidity and mortality. In spite of advances in therapy, the treatment of hormone-dependent cancers remains an unmet health need. The tumor microenvironment (TME) exhibits unique characteristics that differ among various tumor types. It is composed of cancerous, non-cancerous, stromal, and immune cells that are surrounded and supported by components of the extracellular matrix (ECM). Therefore, the interactions among cancer cells, stromal cells, and components of the ECM determine cancer progression and response to therapy. Proteoglycans (PGs), hybrid molecules consisting of a protein core to which sulfated glycosaminoglycan chains are bound, are significant components of the ECM that are implicated in all phases of tumorigenesis. These molecules, secreted by both the stroma and cancer cells, are crucial signaling mediators that modulate the vital cellular pathways implicated in gene expression, phenotypic versatility, and response to therapy in specific tumor types. A plethora of deregulated signaling pathways contributes to the growth, dissemination, and angiogenesis of hormone-dependent cancers. Specific inputs from the endocrine and immune systems are some of the characteristics of hormone-dependent cancer pathogenesis. Importantly, the mechanisms involved in various aspects of cancer progression are executed in the ECM niche of the TME, and the PG components crucially mediate these processes. Here, we comprehensively discuss the mechanisms through which PGs affect the multifaceted aspects of hormone-dependent cancer development and progression, including cancer metastasis, angiogenesis, immunobiology, autophagy, and response to therapy.

A multifunctional dexamethasone-delivery implant fabricated using atmospheric plasma and its effects on apoptosis, osteogenesis and inflammation

Implant-based local drug delivery is a unique surgical therapy with many clinical advantages. Atmospheric pressure plasma is a novel non-thermal surface biotechnology that has only recently been applied in enhancing a surgical implant. We are the first to use this technology to successfully create a dexamethasone-delivery metallic implant. Irrespective of the loaded medication, the surface of this novel implant possesses advantageous material features including homogeneity, hydrophilicity, and optimal roughness. UV-vis spectroscopy revealed much more sustainable drug release compared to the implants produced using simple drug attachment. In addition, our drug-releasing implant was found to have multiple biological benefits. As proven by the ELISA data, this multi-layer drug complex provides differential regulation on the cell apoptosis, as well as pro-osteogenic and anti-inflammatory effects on the peri-implant tissue. Furthermore, using the pathway-specific PCR array, our study discovered 28 and 26 upregulated and downregulated genes during osteogenesis and inflammation on our newly fabricated drug-delivery implant, respectively. The medication-induced change in molecular profile serves as a promising clue for designing future implant-based therapy. Collectively, we present atmospheric pressure plasma as a potent tool for creating a surgical implant-based drug-delivery system, which renders multiple therapeutic potentials. Graphical abstract Schematic of the APP-facilitated Dex-delivery implant. This layer-by-layer drug-releasing complex consisted of bottom plasma activation layer, middle medication layer, and top absorbable polymer layer.

Flipping the Molecular Switch: Influence of Perlecan and Its Modifiers in the Tumor Microenvironment

The tumor microenvironment (TME) is rich in matrix components, growth factors, cytokines, and enzymatic modifiers that respond to changing conditions, to alter the fundamental properties of the tumor bed. Perlecan/HSPG2, a large, multi-domain heparan sulfate proteoglycan, is concentrated in the reactive stroma that surrounds tumors. Depending on its state in the TME, perlecan can either prevent or promote the progression of cancers to metastatic disease. Breast, prostate, lung, and renal cancers all preferentially metastasize to bone, a dense, perlecan-rich environment that is initially a "hostile" niche for cancer cells. Driven by inflammation, production of perlecan and its enzyme modifiers, which include matrix metalloproteinases (MMPs), sulfatases (SULFs), and heparanase (HPSE), increases in the reactive stroma surrounding growing and invading tumors. MMPs act upon the perlecan core protein, releasing bioactive fragments of the protein, primarily from C-terminal domains IV and V. These fragments influence cell adhesion, invasion, and angiogenesis. Sulfatases and heparanases act directly upon the heparan sulfate chains, releasing growth factors from reservoirs to reach receptors on the cancer cell surface. We propose that perlecan modifiers, by promoting the degradation of the perlecan-rich stroma, "flip the molecular switch" and convert the "hostile" stroma into a welcoming one that supports cancer dissemination and metastasis. Targeted therapies that prevent this molecular conversion of the TME should be considered as potential new therapeutics to limit metastasis.

SDF-1 induces TNF-mediated apoptosis in cardiac myocytes

Chemokines are small secreted proteins with chemoattractant properties that play a key role in inflammation. One such chemokine, Stromal cell-derived factor-1 (SDF-1) also known as CXCL12, and its receptor, CXCR4, are expressed and functional in cardiac myocytes. SDF-1 both stimulates and enhances the cellular signal which attracts potentially beneficial stem cells for tissue repair within the ischemic heart. Paradoxically however, this chemokine is known to act in concert with the inflammatory cytokines of the innate immune response which contributes to cellular injury through the recruitment of inflammatory cells during ischemia. In the present study, we have demonstrated that SDF-1 has dose dependent effects on freshly isolated cardiomyocytes. Using Tunnel and caspase 3-activation assays, we have demonstrated that the treatment of isolated adult rat cardiac myocyte with SDF-1 at higher concentrations (pathological concentrations) induced apoptosis. Furthermore, ELISA data demonstrated that the treatment of isolated adult rat cardiac myocyte with SDF-1 at higher concentrations upregulated TNF-α protein expression which directly correlated with subsequent apoptosis. There was a significant reduction in SDF-1 mediated apoptosis when TNF-α expression was neutralized which suggests that SDF-1 mediated apoptosis is TNF-α-dependent. The fact that certain stimuli are capable of driving cardiomyocytes into apoptosis indicates that these cells are susceptible to clinically relevant apoptotic triggers. Our findings suggest that the elevated SDF-1 levels seen in a variety of clinical conditions, including ischemic myocardial infarction, may either directly or indirectly contribute to cardiac cell death via a TNF-α mediated pathway. This highlights the importance of this receptor/ligand in regulating the cardiomyocyte response to stress conditions.

Identification of an IL-1-induced gene expression pattern in AR+ PCa cells that mimics the molecular phenotype of AR- PCa cells

BACKGROUND

In immunosurveillance, bone-derived immune cells infiltrate the tumor and secrete inflammatory cytokines to destroy cancer cells. However, cancer cells have evolved mechanisms to usurp inflammatory cytokines to promote tumor progression. In particular, the inflammatory cytokine, interleukin-1 (IL-1), is elevated in prostate cancer (PCa) patient tissue and serum, and promotes PCa bone metastasis. IL-1 also represses androgen receptor (AR) accumulation and activity in PCa cells, yet the cells remain viable and tumorigenic; suggesting that IL-1 may also contribute to AR-targeted therapy resistance. Furthermore, IL-1 and AR protein levels negatively correlate in PCa tumor cells. Taken together, we hypothesize that IL-1 reprograms AR positive (AR⁺ ) PCa cells into AR negative (AR^- ) PCa cells that co-opt IL-1 signaling to ensure AR-independent survival and tumor progression in the inflammatory tumor microenvironment.

METHODS

LNCaP and PC3 PCa cells were treated with IL-1β or HS-5 bone marrow stromal cell (BMSC) conditioned medium and analyzed by RNA sequencing and RT-QPCR. To verify genes identified by RNA sequencing, LNCaP, MDA-PCa-2b, PC3, and DU145 PCa cell lines were treated with the IL-1 family members, IL-1α or IL-1β, or exposed to HS-5 BMSC in the presence or absence of Interleukin-1 Receptor Antagonist (IL-1RA). Treated cells were analyzed by western blot and/or RT-QPCR.

RESULTS

Comparative analysis of sequencing data from the AR⁺ LNCaP PCa cell line versus the AR^- PC3 PCa cell line reveals an IL-1-conferred gene suite in LNCaP cells that is constitutive in PC3 cells. Bioinformatics analysis of the IL-1 regulated gene suite revealed that inflammatory and immune response pathways are primarily elicited; likely facilitating PCa cell survival and tumorigenicity in an inflammatory tumor microenvironment.

CONCLUSIONS

Our data supports that IL-1 reprograms AR⁺ PCa cells to mimic AR^- PCa gene expression patterns that favor AR-targeted treatment resistance and cell survival.

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

Fibroblasts express androgen receptor (AR) in the normal prostate and during prostate cancer development. We have reported that loss of AR expression in prostate cancer-associated fibroblasts is a poor prognostic indicator. Here we report outcomes of direct and indirect co-cultures of immortalised AR-positive (PShTert-AR) or AR-negative (PShTert) myofibroblasts with prostate cancer cells.

In the initial co-cultures the AR-negative PC3 cell line was used so AR expression and signalling were restricted to the myofibroblasts. In both direct and indirect co-culture with PShTert-AR myofibroblasts, paracrine signalling to the PC3 cells slowed proliferation and induced apoptosis. In contrast, PC3 cells proliferated with PShTert myofibroblasts irrespective of the co-culture method. In direct co-culture PC3 cells induced apoptosis in and destroyed PShTerts by direct signalling. Similar results were seen in direct co-cultures with AR-negative DU145 and AR-positive LNCaP and C4-2B prostate cancer cell lines. The AR ligand 5α-dihydrotestosterone (DHT) inhibited the proliferation of the PShTert-AR myofibroblasts, thereby reducing the extent of their inhibitory effect on cancer cell growth.

These results suggest loss of stromal AR would favour prostate cancer cell growth in vivo, providing an explanation for the clinical observation that reduced stromal AR is associated with a poorer outcome.

Pulse frequency dependency of photobiomodulation on the bioenergetic functions of human dental pulp stem cells

Photobiomodulation (PBM) therapy contributes to pain relief, wound healing, and tissue regeneration. The pulsed wave (PW) mode has been reported to be more effective than the continuous wave (CW) mode when applying PBM to many biological systems. However, the reason for the higher effectiveness of PW-PBM is poorly understood. Herein, we suggest using delayed luminescence (DL) as a reporter of mitochondrial activity after PBM treatment. DL originates mainly from mitochondrial electron transport chain systems, which produce reactive oxygen species (ROS) and adenosine triphosphate (ATP). The decay time of DL depends on the pulse frequencies of applied light, which correlate with the biological responses of human dental pulp stem cells (hDPSCs). Using a low-power light whose wavelength is 810 nm and energy density is 38 mJ/cm², we find that a 300-Hz pulse frequency prolonged the DL pattern and enhanced alkaline phosphatase activity. In addition, we analyze mitochondrial morphological changes and their volume density and find evidence supporting mitochondrial physiological changes from PBM treatment. Our data suggest a new methodology for determining the effectiveness of PBM and the specific pulse frequency dependency of PBM in the differentiation of hDPSCs.

Identification of Fibulin-1 as a Human Bone Marrow Stromal (HS-5) Cell-Derived Factor That Induces Human Prostate Cancer Cell Death

BACKGROUND

Previous studies showed that human bone marrow stromal HS-5 cells secreted unidentified factor(s) inducing PCa cell death. Herein, the HS-5-derived factor (HS-5 DF) was characterized and identified.

METHODS

Conditioned media from confluent HS-5 cells were collected and modified for biochemical characteristic testing of HS-5 DF. Cell survival was measured by apoptosis assay and live/dead assay. Fibulin-1 was identified from gel electrophoresis and mass spectrometry. The validation of Fibulin-1 as a HS-5 DF was done by immunoprecipitation (IP) and genetic knockdown by CRISPR/Cas9 system.

RESULTS

HS-5 DF was trypsin and heat sensitive, but pH stable. The tentative size of the factor fell between 30 kDa and 100 kDa. TGF-β1 treatment led to a suppression of HS-5 DF activity, a property consistent with bone metastasis in prostate cancer. Examination of TGF-β1 down regulated proteins led to identification of fibulin-1 as a candidate for the DF. IP of Fibulin-1 from HS-5 CM and CRISPR knockdown of Fibulin-1 showed a significant reduction of HS-5 CM-derived PCa cell death. These results strongly support a role for fibulin-1 in HS-5 bone marrow stromal cell induction of PCa cell death.

CONCLUSION

Our data indicate that Fibulin-1 functions as a HS-5 bone marrow stromal cell-derived factor inducing prostate cancer cell death. Prostate 77:729-742, 2017. © 2016 Wiley Periodicals, Inc.

Antibody-drug conjugate targeting CD46 eliminates multiple myeloma cells

Multiple myeloma is incurable by standard approaches because of inevitable relapse and development of treatment resistance in all patients. In our prior work, we identified a panel of macropinocytosing human monoclonal antibodies against CD46, a negative regulator of the innate immune system, and constructed antibody-drug conjugates (ADCs). In this report, we show that an anti-CD46 ADC (CD46-ADC) potently inhibited proliferation in myeloma cell lines with little effect on normal cells. CD46-ADC also potently eliminated myeloma growth in orthometastatic xenograft models. In primary myeloma cells derived from bone marrow aspirates, CD46-ADC induced apoptosis and cell death, but did not affect the viability of nontumor mononuclear cells. It is of clinical interest that the CD46 gene resides on chromosome 1q, which undergoes genomic amplification in the majority of relapsed myeloma patients. We found that the cell surface expression level of CD46 was markedly higher in patient myeloma cells with 1q gain than in those with normal 1q copy number. Thus, genomic amplification of CD46 may serve as a surrogate for target amplification that could allow patient stratification for tailored CD46-targeted therapy. Overall, these findings indicate that CD46 is a promising target for antibody-based treatment of multiple myeloma, especially in patients with gain of chromosome 1q.

Neuronal Trans-Differentiation in Prostate Cancer Cells

BACKGROUND

Neuroendocrine (NE) differentiation in prostate cancer (PCa) is an aggressive phenotype associated with therapy resistance. The complete phenotype of these cells is poorly understood. Clinical classification is based predominantly on the expression of standard NE markers.

METHODS

We analyzed the phenotype of NE carcinoma of the prostate utilizing in vitro methods, in silico, and immunohistochemical analyses of human disease.

RESULTS

LNCaP cells, subjected to a variety of stressors (0.1% [v/v] fetal bovine serum, cyclic AMP) induced a reproducible phenotype consistent with neuronal trans-differentiation. Cells developed long cytoplasmic processes resembling neurons. As expected, serum deprived cells had decreased expression in androgen receptor and prostate specific antigen. A significant increase in neuronal markers also was observed. Gene array analysis demonstrated that LNCaP cells subjected to low serum or cAMP showed statistically significant manifestation of a human brain gene expression signature. In an in silico experiment using human data, we identified that only hormone resistant metastatic prostate cancer showed enrichment of the "brain profile." Gene ontology analysis demonstrated categories involved in neuronal differentiation. Three neuronal markers were validated in a large human tissue cohort.

CONCLUSION

This study proposes that the later stages of PCa evolution involves neuronal trans-differentiation, which would enable PCa cells to acquire independence from the neural axis, critical in primary tumors. Prostate 76:1312-1325, 2016. © 2016 Wiley Periodicals, Inc.

Quantitative proteomic analysis and comparison of two bone marrow stromal cell lines using the SILAC method

Two human bone marrow stromal cell lines, HS5 and HS27a, co-cultured with myeloid cells, have frequently been used in studies of cross talk between cells in the bone marrow microenvironment and hematopoietic cells. Altered expression of proteins is typically associated with cell-cell signal transduction and regulation of cellular functions. Many studies have focused on key proteins that contribute to functional differences in cell co-culture models, but global quantitative proteome analysis of HS5 and HS27a has not been performed. We employed the stable isotope labeling by amino acids in cell culture (SILAC) method using two stable isotopes each of arginine and lysine to label proteins in the two cell lines. Labeled proteins were analyzed by 2-D ultrahigh-resolution liquid chromatography- LTQ/Orbitrap mass spectrometry. Among 4,213 unique identified and annotated proteins in the cell lines, 1,462 were detected in two independent experiments. Of these, 69 exhibited significant upregulation and 48 significant downregulation (>95% confidence) in HS27a relative to HS5 cells. Gene ontology term and pathway analysis indicated that the differentially regulated proteins were involved in cellular movement, cell-to-cell signaling and interaction, and hematologic system development and function. A total of 55 items were identified in both genomic and proteomic databases. Quantitative reverse transcription polymerase chain reaction and Western blotting were performed on 7 proteins randomly selected from 28 differentially expressed proteins that were identified in both databases and were involved in the top networks/pathways. We observed a decrease in apoptosis in co-cultured KG1a cells when integrin αV was inhibited in HS27a cells, which suggested the functional role of integrin αV in the co-culture system. The integrated genomic/proteomic approach described here, and the identified proteins, will provide a useful basis for further elucidation of molecular mechanisms in the bone marrow microenvironment and for ongoing studies of cross talk among stromal cells and myeloma cells in co-culture systems.

Intracellular Elemental Patterns of Apoptosis Resistance in Transdifferentiated Androgen-Dependent Prostatic Carcinoma Cells

The acquisition of neuroendocrine (NE) characteristics by prostate cancer (PC) cells relates to tumor progression and hormone resistance. PC cells may survive and function in androgen-deprived environments, where they could establish paracrine signaling networks, providing stimuli for the propagation of local carcinoma cells. We previously demonstrated, using electron probe X-ray microanalysis (EPXMA), in LNCaP, PC-3, and Du 145 cell lines that apoptosis is associated with intracellular elemental changes, and that the NE secretory products, bombesin and calcitonin, inhibit etoposide-induced apoptosis, as well as some of these elemental changes. In this study, LNCaP cells were induced in vitro to transdifferentiate under androgen deprivation, to mimic the role of NE cells in the apoptotic activity of transdifferentiated androgen-dependent PC cells. Changes in intracellular ion content associated with apoptosis, assessed by EPXMA, demonstrate that the transdifferentiated LNCaP cells are resistant to etoposide-induced apoptosis and also to the etoposide-induced elemental changes. The aggressive malignant potential of PC with neuroendocrine differentiation, associated with hormonal independence, is partly because of the ability that most NE tumor cells have to escape apoptosis, which can enhance the malignant properties of tumor cells and may have therapeutic implications as tumor cells are usually resistant to cytotoxic drugs as etoposide.

Sequential culture on biomimetic nanoclay scaffolds forms three-dimensional tumoroids

In recent times, the limitation of two-dimensional cultures and complexity of in vivo models has paved the way for the development of three-dimensional models for studying cancer. Here we report the development of a new tumor model using PCL/HAPClay scaffolds seeded with a sequential culture of human mesenchymal stem cells (hMSCs) followed by human prostate cancer cells (HPCCs). This nanocomposite system is used as a test-bed for studying cancer metastasis and efficacy of anti-cancer drugs using a polymersome delivery method. A novel sequential cell culture system in three-dimensional in vitro bone model provides a unique bone mimetic environment. The hMSCs seeded scaffolds are seeded with prostate cancer cells after the hMSCs have differentiated into osteoblasts. Sequential culture on the scaffolds has shown formation of tumoroids or microtissue consisting of organized, densely packed round cells with hypoxic core regions similar to in vivo tumors. Such tumoroids are not observed on HPCC seeded scaffolds or when HPCCs sequentially cultured with human osteoblast cells. Clearly, the newly differentiated hMSCs play a vital role in the ability of cancer cells to grow into tumoroids and cause disease. The PCL/HAPclay scaffold system seeded with the sequential culture of hMSCs, and HPCCs presents a good model system for study of the interactions between prostate cancer cells and bone microenvironment. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1591-1602, 2016.

Transforming growth factor-β signaling induced during prostate cancer cell death and neuroendocrine differentiation is mediated by bone marrow stromal cells

INTRODUCTION

Prostate cancer that has metastasized to bone undergoes critical interactions with bone marrow stromal cells (BMSCs), ultimately promoting tumor survival. Previous studies have shown that BMSCs secrete factors that promote prostate cancer apoptosis or neuroendocrine differentiation. Because of the significance of transforming growth factor-β (TGF-β) family cytokines in cytostasis and bone metastasis, the role of TGF-β signaling in the context of prostate cancer-BMSC interactions was investigated.

METHODS

The role of TGF-β family signaling in BMSC-induced apoptosis of lineage-related prostate cancer cells was investigated in live/dead assays. SMAD phosphorylation or activity during apoptosis and neuroendocrine differentiation was investigated using immunofluorescence, Western blotting, and luciferase reporter assays, along with the ALK-4, -5, -7 kinase inhibitor, SB-431542.

RESULTS

Treatment of castration-resistant prostate cancer cells with SB-431542 resulted in significant reduction of apoptosis mediated by HS-5 BMSCs, supporting the involvement of TGF-β/SMAD signaling during this event. Interestingly, however, pre-treatment of BMSCs with TGF-β1 (5 ng/mL) yielded a conditioned medium that elicited a marked reduction in prostate cancer death. Phosphorylated-SMAD2 (P-SMAD2) was activated in BMSC-triggered transdifferentiated prostate cancer cells, as demonstrated through immunoblotting and luciferase reporter assays. However, SB-431542 did not restore androgen receptor and prostate specific antigen levels down-regulated by BMSC-secreted factors. Prostate cancer cells induced to undergo neuroendocrine differentiation in a BMSC-independent mechanism also showed elevated levels of P-SMAD2.

DISCUSSION

Collectively, our findings indicate that: (1) TGF-β family cytokines or regulated factors secreted from BMSCs are involved in prostate cancer apoptosis; (2) TGF-β signaling in prostate cancer cells is induced during neuroendocrine differentiation; and (3) TGF-β1 stimulation of BMSCs alters paracrine signaling to create a permissive environment for prostate cancer survival, suggesting a mechanism for prostate cancer-mediated colonization of bone.

CONCLUSIONS

TGF-β signaling resulting in activation of SMAD2 in prostate cancer may be an indicator of cellular stress in the presence of toxic paracrine factors released from the bone marrow stroma, ultimately fostering prostate cancer colonization of bone.

IL-1β induces p62/SQSTM1 and represses androgen receptor expression in prostate cancer cells

Chronic inflammation is associated with advanced prostate cancer (PCa), although the mechanisms governing inflammation-mediated PCa progression are not fully understood. PCa progresses to an androgen independent phenotype that is incurable. We previously showed that androgen independent, androgen receptor negative (AR(-) ) PCa cell lines have high p62/SQSTM1 levels required for cell survival. We also showed that factors in the HS-5 bone marrow stromal cell (BMSC) conditioned medium can upregulate p62 in AR(+) PCa cell lines, leading us to investigate AR expression under those growth conditions. In this paper, mRNA, protein, and subcellular analyses reveal that HS-5 BMSC conditioned medium represses AR mRNA, protein, and nuclear accumulation in the C4-2 PCa cell line. Using published gene expression data, we identify the inflammatory cytokine, IL-1β, as a candidate BMSC paracrine factor to regulate AR expression and find that IL-1β is sufficient to both repress AR and upregulate p62 in multiple PCa cell lines. Immunostaining demonstrates that, while the C4-2 population shows a primarily homogeneous response to factors in HS-5 BMSC conditioned medium, IL-1β elicits a strikingly heterogeneous response; suggesting that there are other regulatory factors in the conditioned medium. Finally, while we observe concomitant AR loss and p62 upregulation in IL-1β-treated C4-2 cells, silencing of AR or p62 suggests that IL-1β regulates their protein accumulation through independent pathways. Taken together, these in vitro results suggest that IL-1β can drive PCa progression in an inflammatory microenvironment through AR repression and p62 induction to promote the development and survival of androgen independent PCa.

Prostate cancer and neuroendocrine differentiation: more neuronal, less endocrine?

Neuroendocrine differentiation (NED) marks a structural and functional feature of certain cancers, including prostate cancer (PCa), whereby the malignant tissue contains a significant proportion of cells displaying neuronal, endocrine, or mixed features. NED cells produce, and can secrete, a cocktail of mediators commonly encountered in the nervous system, which may stimulate and coordinate cancer growth. In PCa, NED appears during advanced stages, subsequent to treatment, and accompanies treatment resistance and poor prognosis. However, the term “neuroendocrine” in this context is intrinsically vague. This article seeks to provide a framework on which a unified view of NED might emerge. First, we review the mutually beneficial interplay between PCa and neural structures, mainly supported by cell biology experiments and neurological conditions. Next, we address the correlations between PCa and neural functions, as described in the literature. Based upon the integration of clinical and basic observations, we suggest that it is legitimate to seek for true neural differentiation, or neuromimicry, in cancer progression, most notably in PCa cells exhibiting what is commonly described as NED.

CCL5 secreted from bone marrow stromal cells stimulates the migration and invasion of Huh7 hepatocellular carcinoma cells via the PI3K-Akt pathway

Bone metastases from hepatocellular carcinoma (HCC) seem to be increasing. Previous studies showed that soluble factors secreted by host cells and direct cell-to-cell interactions contributed to the preferential metastasis and growth of cancer cells in bone, while the underlying mechanism(s) of the metastasis of HCC in the bone are poorly understood. Here, we determined the effect of HS-5 cells on Huh7 cell proliferation, and investigated the role of CCL5 from HS-5 cells on the development of Huh7 cells. In addition, the underlying mechanisms on the influence in Huh7 cells were investigated. Our results showed that HS-5 cells could promote the proliferation, migration and invasion of Huh7 cells, and inhibited apoptosis. CCL5 downregulation was able to inhibit the effects of HS-5 cells on Huh7 cell migration and invasion via the PI3K-Akt signaling pathway and reduce MMP-2 expression. Therefore, these findings suggest that CCL5 secreted from MSCs can promote the migration and invasion of Huh7 cells and could be an important factor in HCC related to occurrence of bone metastases.

p62/SQSTM1 is required for cell survival of apoptosis-resistant bone metastatic prostate cancer cell lines

BACKGROUND

Bone marrow stromal cell (BMSC) paracrine factor(s) can induce apoptosis in bone metastatic prostate cancer (PCa) cell lines. However, the PCa cells that escape BMSC-induced apoptosis can upregulate cytoprotective autophagy.

METHODS

C4-2, C4-2B, MDA PCa 2a, MDA PCa 2b, VCaP, PC3, or DU145 PCa cell lines were grown in BMSC conditioned medium and analyzed for mRNA and/or protein accumulation of p62 (also known as sequestome-1/SQSTM1), Microtubule-associated protein 1 light chain 3B (LC3B), or lysosomal-associated membrane protein 1 (LAMP1) using quantitative polymerase chain reaction (QPCR), Western blot, or immunofluorescence. Small interfering RNA (siRNA) was used to determine if p62 is necessary PCa cell survival.

RESULTS

BMSC paracrine signaling upregulated p62 mRNA and protein in a subset of the PCa cell lines. The PCa cell lines that were insensitive to BMSC-induced apoptosis and autophagy induction had elevated basal p62 mRNA and protein. In the BMSC-insensitive PCa cell lines, siRNA knockdown of p62 was cytotoxic and immunostaining showed peri-nuclear clustering of autolysosomes. However, in the BMSC-sensitive PCa cell lines, p62 siRNA knockdown was not appreciably cytotoxic and did not affect autolysosome subcellular localization.

CONCLUSIONS

A pattern emerges wherein the BMSC-sensitive PCa cell lines are known to be osteoblastic and express the androgen receptor, while the BMSC-insensitive PCa cell lines are characteristically osteolytic and do not express the androgen receptor. Furthermore, BMSC-insensitive PCa may have evolved a dependency on p62 for cell survival that could be exploited to target and kill these apoptosis-resistant PCa cells in the bone.

The role of vascular endothelial growth factor in metastatic prostate cancer to the skeleton

Despite the clinical implication and high incidence of bone and spinal metastases, the molecular mechanisms behind prostate cancer metastasis to bone and spine are not well understood. In this review the molecular mechanisms that may contribute to the highly metastatic phenotype of prostate cancer are discussed. Proangiogenic factors such as vascular endothelial growth factor (VEGF) have been shown to not only aid in the metastatic capabilities of prostate cancer but also encourage the colonization and growth of prostate tumour cells in the skeleton. The importance of VEGF in the complex process of prostate cancer dissemination to the skeleton is discussed, including its role in the development of the bone premetastatic niche, metastatic tumour cell recognition of bone, and bone remodeling. The expression of VEGF has also been shown to be upregulated in prostate cancer and is associated with clinical stage, Gleason score, tumour stage, progression, metastasis, and survival. Due to the multifaceted effect VEGF has on tumour angiogenesis, tumour cell proliferation, and bone destruction, therapies targeting the VEGF pathways have shown promising clinical application and are being investigated in clinical trials.

The osteoblastic and osteoclastic interactions in spinal metastases secondary to prostate cancer

Prostate cancer (PC) is one of the most common cancers arising in men and has a high propensity for bone metastasis, particularly to the spine. At this stage, it often causes severe morbidity due to pathological fracture and/or metastatic epidural spinal cord compression which, if untreated, inevitably leads to intractable pain, neurological deficit, and paralysis. Unfortunately, the underlying molecular mechanisms driving growth of secondary PC in the bony vertebral column remain largely unknown. Further investigation is warranted in order to identify therapeutic targets in the future. This review summarizes the current understanding of PC bone metastasis in the spine, highlighting interactions between key tumor and bone-derived factors which influence tumor progression, especially the functional roles of osteoblasts and osteoclasts in the bone microenvironment through their interactions with metastatic PC cells and the critical pathway RANK/RANKL/OPG in bone destruction.

Bone-stromal cells up-regulate tumourigenic markers in a tumour-stromal 3D model of prostate cancer

Background

The cellular and molecular mechanisms that mediate interactions between tumour cells and the surrounding bone stroma are to date largely undetermined in prostate cancer (PCa) progression. The purpose of this study was to evaluate the role of alpha 6 and beta 1 integrin subunits in mediating tumour-stromal interactions.

Methods

Utilising 3D in vitro assays we evaluated and compared 1. Monocultures of prostate metastatic PC3, bone stromal derived HS5 and prostate epithelial RWPE-1 cells and 2. Tumour-stromal co-cultures (PC3 + HS5) to ascertain changes in cellular phenotype, function and expression of metastatic markers.

Results

In comparison to 3D monocultures of PC3 or HS5 cells, when cultured together, these cells displayed up-regulated invasive and proliferative qualities, along with altered expression of epithelial-to-mesenchymal and chemokine protein constituents implicated in metastatic dissemination. When co-cultured, HS5 cells were found to re-express N-Cadherin and chemokine receptor CXCR7. Alterations in N-Cadherin expression were found to be mediated by soluble factors secreted by PC3 tumour cells, while chemokine receptor re-expression was dependent on direct cell-cell interactions. We have also shown that integrins beta 1 and alpha 6 play an integral role in maintaining cell homeostasis and mediating expression of E-Cadherin, N-Cadherin and vimentin, in addition to chemokine receptor CXCR7.

Conclusions

Collectively our results suggest that both PC3 and HS5 cells provide a “protective” and reciprocal milieu that promotes tumour growth. As such 3D co-cultures may serve as a more complex and valid biological model in the drug discovery pipeline.

Upregulation of SATB1 is associated with prostate cancer aggressiveness and disease progression

Disease aggressiveness remains a critical factor to the progression of prostate cancer. Transformation of epithelial cells to mesenchymal lineage, associated with the loss of E-cadherin, offers significant invasive potential and migration capability. Recently, Special AT-rich binding protein (SATB1) has been linked to tumor progression. SATB1 is a cell-type restricted nuclear protein, which functions as a tissue-specific organizer of DNA sequences during cellular differentiation. Our results demonstrate that SATB1 plays significant role in prostate tumor invasion and migration and its nuclear localization correlates with disease aggressiveness. Clinical specimen analysis showed that SATB1 was predominantly expressed in the nucleus of high-grade tumors compared to low-grade tumor and benign tissue. A progressive increase in the nuclear levels of SATB1 was observed in cancer tissues compared to benign specimens. Similarly, SATB1 protein levels were higher in a number of prostate cancer cells viz. HPV-CA-10, DU145, DUPro, PC-3, PC-3M, LNCaP and C4-2B, compared to non-tumorigenic PZ-HPV-7 cells. Nuclear expression of SATB1 was higher in biologically aggressive subclones of prostate cancer cells with their respective parental cell lines. Furthermore, ectopic SATB1 transfection conferred increased cell motility and invasiveness in immortalized human prostate epithelial PZ-HPV-7 cells which correlated with the loss of E-cadherin expression. Consequently, knockdown of SATB1 in highly aggressive human prostate cancer PC-3M cells inhibited invasiveness and tumor growth in vivo along with increase in E-cadherin protein expression. Our findings demonstrate that SATB1 has ability to promote prostate cancer aggressiveness through epithelial-mesenchymal transition.

Hyaluronan (HA) interacting proteins RHAMM and hyaluronidase impact prostate cancer cell behavior and invadopodia formation in 3D HA-based hydrogels

To study the individual functions of hyaluronan interacting proteins in prostate cancer (PCa) motility through connective tissues, we developed a novel three-dimensional (3D) hyaluronic acid (HA) hydrogel assay that provides a flexible, quantifiable, and physiologically relevant alternative to current methods. Invasion in this system reflects the prevalence of HA in connective tissues and its role in the promotion of cancer cell motility and tissue invasion, making the system ideal to study invasion through bone marrow or other HA-rich connective tissues. The bio-compatible cross-linking process we used allows for direct encapsulation of cancer cells within the gel where they adopt a distinct, cluster-like morphology. Metastatic PCa cells in these hydrogels develop fingerlike structures, “invadopodia”, consistent with their invasive properties. The number of invadopodia, as well as cluster size, shape, and convergence, can provide a quantifiable measure of invasive potential. Among candidate hyaluronan interacting proteins that could be responsible for the behavior we observed, we found that culture in the HA hydrogel triggers invasive PCa cells to differentially express and localize receptor for hyaluronan mediated motility (RHAMM)/CD168 which, in the absence of CD44, appears to contribute to PCa motility and invasion by interacting with the HA hydrogel components. PCa cell invasion through the HA hydrogel also was found to depend on the activity of hyaluronidases. Studies shown here reveal that while hyaluronidase activity is necessary for invadopodia and inter-connecting cluster formation, activity alone is not sufficient for acquisition of invasiveness to occur. We therefore suggest that development of invasive behavior in 3D HA-based systems requires development of additional cellular features, such as activation of motility associated pathways that regulate formation of invadopodia. Thus, we report development of a 3D system amenable to dissection of biological processes associated with cancer cell motility through HA-rich connective tissues.

Interleukin-6: a bone marrow stromal cell paracrine signal that induces neuroendocrine differentiation and modulates autophagy in bone metastatic PCa cells

Autophagy reallocates nutrients and clears normal cells of damaged proteins and organelles. In the context of metastatic disease, invading cancer cells hijack autophagic processes to survive and adapt in the host microenvironment. We sought to understand how autophagy is regulated in the metastatic niche for prostate cancer (PCa) cells where bone marrow stromal cell (BMSC) paracrine signaling induces PCa neuroendocrine differentiation (NED). In PCa, this transdifferentiation of metastatic PCa cells to neuronal-like cells correlates with advanced disease. Because autophagy provides a survival advantage for cancer cells and promotes cell differentiation, we hypothesized that autophagy mediates PCa NED in the bone. Thus, we determined the ability of paracrine factors in conditioned media (CM) from two separate BMSC subtypes, HS5 and HS27a, to induce autophagy in C4-2 and C4-2B bone metastatic PCa cells by characterizing the autophagy marker, LC3. Unlike HS27a CM, HS5 CM induced LC3 accumulation in PCa cells, suggesting autophagy was induced and indicating that HS5 and HS27a secrete a different milieu of paracrine factors that influence PCa autophagy. We identified interleukin-6 (IL-6), a cytokine more highly expressed in HS5 cells than in HS27a cells, as a paracrine factor that regulates PCa autophagy. Pharmacological inhibition of STAT3 activity did not attenuate LC3 accumulation, implying that IL-6 regulates NED and autophagy through different pathways. Finally, chloroquine inhibition of autophagic flux blocked PCa NED; hence autophagic flux maintains NED. Our studies imply that autophagy is cytoprotective for PCa cells in the bone, thus targeting autophagy is a potential therapeutic strategy.

PC3 is a cell line characteristic of prostatic small cell carcinoma

BACKGROUND

The majority of the prostatic cancers are adenocarcinomas characterized by glandular formation and the expression of luminal differentiation markers androgen receptor (AR) and prostate-specific antigen (PSA). Most adenocarcinomas are indolent and androgen-dependent. Hormonal therapy that inhibits AR signaling produces symptomatic relief in patients with advanced and metastatic adenocarcinomas. Prostatic small cell neuroendocrine carcinoma (SCNC) is a variant form of prostate cancer (PC). In contrast to adenocarcinoma, the tumor cells of SCNC do not form glands and are negative for AR and PSA. SCNC is extremely aggressive and does not respond to hormonal therapy. The purpose of this study was to compare the important and relevant features of two most commonly used PC cell lines, LNCaP and PC3, with prostatic adenocarcinoma and SCNC.

METHODS

Xenograft tumors of LNCaP and PC3 were prepared and compared with human prostatic adenocarcinoma and SCNC for the expression of key signaling molecules by immunohistochemistry and Western blot analysis.

RESULTS

LNCaP cells express AR and PSA and their growth is inhibited by androgen withdrawal, similar to human prostatic adenocarcinoma. PC3 cells do not express AR and PSA and their proliferation is independent of androgen, similar to SCNC. Adenocarcinoma cells and LNCaP cells are negative for neuroendocrine markers and stem cell-associated marker CD44 while SCNC and PC3 cells are positive. LNCaP cells have identical cytokeratin profiles to adenocarcinoma while PC3 cells have cytokeratin profiles similar to SCNC.

CONCLUSION

LNCaP cells share common features with adenocarcinoma while PC3 cells are characteristic of SCNC.