A novel patient-derived intra-femoral xenograft model of bone metastatic prostate cancer that recapitulates mixed osteolytic and osteoblastic lesions

Prostate Cancer Progression Relies on the Mitotic Kinase Citron Kinase

Prostate cancer remains the second leading cause of cancer death in men in Western cultures. A deeper understanding of the mechanisms by which prostate cancer cells divide to support tumor growth could help devise strategies to overcome treatment resistance and improve survival. Here, we identified that the mitotic AGC family protein kinase citron kinase (CIT) is a pivotal regulator of prostate cancer growth that mediates prostate cancer cell interphase progression. Increased CIT expression correlated with prostate cancer growth induction and aggressive prostate cancer progression, and CIT was overexpressed in prostate cancer compared with benign prostate tissue. CIT overexpression was controlled by an E2F2-Skp2-p27 signaling axis and conferred resistance to androgen-targeted treatment strategies. The effects of CIT relied entirely on its kinase activity. Conversely, CIT silencing inhibited the growth of cell lines and xenografts representing different stages of prostate cancer progression and treatment resistance but did not affect benign epithelial prostate cells or nonprostatic normal cells, indicating a potential therapeutic window for CIT inhibition. CIT kinase activity was identified as druggable and was potently inhibited by the multikinase inhibitor OTS-167, which decreased the proliferation of treatment-resistant prostate cancer cells and patient-derived organoids. Isolation of the in vivo CIT substrates identified proteins involved in diverse cellular functions ranging from proliferation to alternative splicing events that are enriched in treatment-resistant prostate cancer. These findings provide insights into the regulation of aggressive prostate cancer cell behavior by CIT and identify CIT as a functionally diverse and druggable driver of prostate cancer progression.

SIGNIFICANCE

The poorly characterized protein kinase citron kinase is a therapeutic target in prostate cancer that drives tumor growth by regulating diverse substrates, which control several hallmarks of aggressive prostate cancer progression. See related commentary by Mishra et al., p. 4008.

Novel Dormancy Mechanism of Castration Resistance in Bone Metastatic Prostate Cancer Organoids

Advanced prostate cancer (PCa) patients with bone metastases are treated with androgen pathway directed therapy (APDT). However, this treatment invariably fails and the cancer becomes castration resistant. To elucidate resistance mechanisms and to provide a more predictive pre-clinical research platform reflecting tumor heterogeneity, we established organoids from a patient-derived xenograft (PDX) model of bone metastatic prostate cancer, PCSD1. APDT-resistant PDX-derived organoids (PDOs) emerged when cultured without androgen or with the anti-androgen, enzalutamide. Transcriptomics revealed up-regulation of neurogenic and steroidogenic genes and down-regulation of DNA repair, cell cycle, circadian pathways and the severe acute respiratory syndrome (SARS)-CoV-2 host viral entry factors, ACE2 and TMPRSS2. Time course analysis of the cell cycle in live cells revealed that enzalutamide induced a gradual transition into a reversible dormant state as shown here for the first time at the single cell level in the context of multi-cellular, 3D living organoids using the Fucci2BL fluorescent live cell cycle tracker system. We show here a new mechanism of castration resistance in which enzalutamide induced dormancy and novel basal-luminal-like cells in bone metastatic prostate cancer organoids. These PDX organoids can be used to develop therapies targeting dormant APDT-resistant cells and host factors required for SARS-CoV-2 viral entry.

Loss of microRNA-135b Enhances Bone Metastasis in Prostate Cancer and Predicts Aggressiveness in Human Prostate Samples

About 70% of advanced-stage prostate cancer (PCa) patients will experience bone metastasis, which severely affects patients' quality of life and progresses to lethal PCa in most cases. Hence, understanding the molecular heterogeneity of PCa cell populations and the signaling pathways associated with bone tropism is crucial. For this purpose, we generated an animal model with high penetrance to metastasize to bone using an intracardiac percutaneous injection of PC3 cells to identify PCa metastasis-promoting factors. Using genomic high-throughput analysis we identified a miRNA signature involved in bone metastasis that also presents potential as a biomarker of PCa progression in human samples. In particular, the downregulation of miR-135b favored the incidence of bone metastases by significantly increasing PCa cells' migratory capacity. Moreover, the PLAG1, JAKMIP2, PDGFA, and VTI1b target genes were identified as potential mediators of miR-135b's role in the dissemination to bone. In this study, we provide a genomic signature involved in PCa bone growth, contributing to a better understanding of the mechanisms responsible for this process. In the future, our results could ultimately translate into promising new therapeutic targets for the treatment of lethal PCa.

A PSMA-targeted bispecific antibody for prostate cancer driven by a small-molecule targeting ligand

Despite the development of next-generation antiandrogens, metastatic castration-resistant prostate cancer (mCRPC) remains incurable. Here, we describe a unique semisynthetic bispecific antibody that uses site-specific unnatural amino acid conjugation to combine the potency of a T cell-recruiting anti-CD3 antibody with the specificity of an imaging ligand (DUPA) for prostate-specific membrane antigen. This format enabled optimization of structure and function to produce a candidate (CCW702) with specific, potent in vitro cytotoxicity and improved stability compared with a bispecific single-chain variable fragment format. In vivo, CCW702 eliminated C4-2 xenografts with as few as three weekly subcutaneous doses and prevented growth of PCSD1 patient-derived xenograft tumors in mice. In cynomolgus monkeys, CCW702 was well tolerated up to 34.1 mg/kg per dose, with near-complete subcutaneous bioavailability and a PK profile supporting testing of a weekly dosing regimen in patients. CCW702 is being evaluated in a first in-human clinical trial for men with mCRPC who had progressed on prior therapies (NCT04077021).

Patient-derived xenografts and organoids model therapy response in prostate cancer

Therapy resistance and metastatic processes in prostate cancer (PCa) remain undefined, due to lack of experimental models that mimic different disease stages. We describe an androgen-dependent PCa patient-derived xenograft (PDX) model from treatment-naïve, soft tissue metastasis (PNPCa). RNA and whole-exome sequencing of the PDX tissue and organoids confirmed transcriptomic and genomic similarity to primary tumor. PNPCa harbors BRCA2 and CHD1 somatic mutations, shows an SPOP/FOXA1-like transcriptomic signature and microsatellite instability, which occurs in 3% of advanced PCa and has never been modeled in vivo. Comparison of the treatment-naïve PNPCa with additional metastatic PDXs (BM18, LAPC9), in a medium-throughput organoid screen of FDA-approved compounds, revealed differential drug sensitivities. Multikinase inhibitors (ponatinib, sunitinib, sorafenib) were broadly effective on all PDX- and patient-derived organoids from advanced cases with acquired resistance to standard-of-care compounds. This proof-of-principle study may provide a preclinical tool to screen drug responses to standard-of-care and newly identified, repurposed compounds.

Modeling Primary Bone Tumors and Bone Metastasis with Solid Tumor Graft Implantation into Bone

Primary bone tumors or bone metastasis from solid tumors result in painful osteolytic, osteoblastic, or mixed osteolytic/osteoblastic lesions. These lesions compromise bone structure, increase the risk of pathologic fracture, and leave patients with limited treatment options. Primary bone tumors metastasize to distant organs, with some types capable of spreading to other skeletal sites. However, recent evidence suggests that with many solid tumors, cancer cells that have spread to bone may be the primary source of cells that ultimately metastasize to other organ systems. Most syngeneic or xenograft mouse models of primary bone tumors involve intra-osseous (orthotopic) injection of tumor cell suspensions. Some animal models of skeletal metastasis from solid tumors also depend on direct bone injection, while others attempt to recapitulate additional steps of the bone metastatic cascade by injecting cells intravascularly or into the organ of the primary tumor. However, none of these models develop bone metastasis reliably or with an incidence of 100%. In addition, direct intra-osseous injection of tumor cells has been shown to be associated with potential tumor embolization of the lung. These embolic tumor cells engraft but do not recapitulate the metastatic cascade. We reported a mouse model of osteosarcoma in which fresh or cryopreserved tumor fragments (consisting of tumor cells plus stroma) are implanted directly into the proximal tibia using a minimally invasive surgical technique. These animals developed reproducible engraftment, growth, and, over time, osteolysis and lung metastasis. This technique has the versatility to be used to model solid tumor bone metastasis and can readily employ grafts consisting of one or multiple cell types, genetically-modified cells, patient-derived xenografts, and/or labeled cells that can be tracked by optical or advanced imaging. Here, we demonstrate this technique, modeling primary bone tumors and bone metastasis using solid tumor graft implantation into bone.

Canine prostatic cancer cell line (LuMa) with osteoblastic bone metastasis

BACKGROUND

Osteoblastic bone metastasis represents the most common complication in men with prostate cancer (PCa). During progression and bone metastasis, PCa cells acquire properties similar to bone cells in a phenomenon called osteomimicry, which promotes their ability to metastasize, proliferate, and survive in the bone microenvironment. The mechanism of osteomimicry resulting in osteoblastic bone metastasis is unclear.

METHODS

We developed and characterized a novel canine prostatic cancer cell line (LuMa) that will be useful to investigate the relationship between osteoblastic bone metastasis and osteomimicry in PCa. The LuMa cell line was established from a primary prostate carcinoma of a 13-year old mixed breed castrated male dog. Cell proliferation and gene expression of LuMa were measured and compared to three other canine prostatic cancer cell lines (Probasco, Ace-1, and Leo) in vitro. The effect of LuMa cells on calvaria and murine preosteoblastic (MC3T3-E1) cells was measured by quantitative reverse-transcription polymerase chain reaction and alkaline phosphatase assay. LuMa cells were transduced with luciferase for monitoring in vivo tumor growth and metastasis using different inoculation routes (subcutaneous, intratibial [IT], and intracardiac [IC]). Xenograft tumors and metastases were evaluated using radiography and histopathology.

RESULTS

After left ventricular injection, LuMa cells metastasized to bone, brain, and adrenal glands. IT injections induced tumors with intramedullary new bone formation. LuMa cells had the highest messenger RNA levels of osteomimicry genes (RUNX2, RANKL, and Osteopontin [OPN]), CD44, E-cadherin, and MYOF compared to Ace-1, Probasco, and Leo cells. LuMa cells induced growth in calvaria defects and modulated gene expression in MC3T3-E1 cells.

CONCLUSIONS

LuMa is a novel canine PCa cell line with osteomimicry and stemness properties. LuMa cells induced osteoblastic bone formation in vitro and in vivo. LuMa PCa cells will serve as an excellent model for studying the mechanisms of osteomimicry and osteoblastic bone and brain metastasis in prostate cancer.

A Novel Small Molecule Inhibits Tumor Growth and Synergizes Effects of Enzalutamide on Prostate Cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death for men in the United States. Approximately 35% of PCa recurs and is often transformed to castration-resistant prostate cancer (CRPCa), the most deadly and aggressive form of PCa. However, the CRPCa standard-of-care treatment (enzalutamide with abiraterone) usually has limited efficacy. Herein, we report a novel molecule (PAWI-2) that inhibits cellular proliferation of androgen-sensitive and androgen-insensitive cells (LNCaP and PC-3, respectively). In vivo studies in a PC-3 xenograft model showed that PAWI-2 (20 mg/kg per day i.p., 21 days) inhibited tumor growth by 49% compared with vehicle-treated mice. PAWI-2 synergized currently clinically used enzalutamide in in vitro inhibition of PCa cell viability and resensitized inhibition of in vivo PC-3 tumor growth. Compared with vehicle-treated mice, PC-3 xenograft studies also showed that PAWI-2 (20 mg/kg per day i.p., 21 days) and enzalutamide (5 mg/kg per day i.p., 21 days) inhibited tumor growth by 63%. Synergism was mainly controlled by the imbalance of prosurvival factors (e.g., Bcl-2, Bcl-xL, Mcl-1) and antisurvival factors (e.g., Bax, Bak) induced by affecting mitochondrial membrane potential/mitochondria dynamics. Thus, PAWI-2 utilizes a distinct mechanism of action to inhibit PCa growth independently of androgen receptor signaling and overcomes enzalutamide-resistant CRPCa. SIGNIFICANCE STATEMENT: Castration-resistant prostate cancer (CRPCa) is the most aggressive human prostate cancer (PCa) but standard chemotherapies for CRPCa are largely ineffective. PAWI-2 potently inhibits PCa proliferation in vitro and in vivo regardless of androgen receptor status and uses a distinct mechanism of action. PAWI-2 has greater utility in treating CRPCa than standard-of-care therapy. PAWI-2 possesses promising therapeutic potency in low-dose combination therapy with a clinically used drug (e.g., enzalutamide). This study describes a new approach to address the overarching challenge in clinical treatment of CRPCa.

Development of patient-derived xenograft models of prostate cancer for maintaining tumor heterogeneity

Prostate cancer (Pca) is a heterogeneous disease with multiple morphological patterns. Thus, the establishment of a patient-derived xenograft (PDX) model that retains key features of the primary tumor is of great significance. This review demonstrates the characteristics and advantages of the Pca PDX model and summarizes the main factors affecting the establishment of the model. Because this model well recapitulates the diverse heterogeneity observed in the clinic, it was extensively utilized to discover new therapeutic targets, screen drugs, and explore metastatic mechanisms. In the future, clinical phenotype and different stages of the Pca patient might be faithfully reflected by PDX model, which provides tremendous potential for understanding Pca biology and achieving individualized treatment.

Hypoxia-induced PIM kinase and laminin-activated integrin α6 mediate resistance to PI3K inhibitors in bone-metastatic CRPC

Bone-metastatic castration-resistant prostate cancer (CRPC) is lethal due to inherent resistance to androgen deprivation therapy, chemotherapy, and targeted therapies. Despite the fact that a majority of CRPC patients (approximately 70%) harbor a constitutively active PI3K survival pathway, targeting the PI3K/mTOR pathway has failed to increase overall survival in clinical trials. Here, we identified two separate and independent survival pathways induced by the bone tumor microenvironment that are hyperactivated in CRPC and confer resistance to PI3K inhibitors. The first pathway involves integrin α6β1-mediated adhesion to laminin and the second involves hypoxia-induced expression of PIM kinases. In vitro and in vivo models demonstrate that these pathways transduce parallel but independent signals that promote survival by reducing oxidative stress and preventing cell death. We further demonstrate that both pathways drive resistance to PI3K inhibitors in PTEN-negative tumors. These results provide preclinical evidence that combined inhibition of integrin α6β1 and PIM kinase in CRPC is required to overcome tumor microenvironment-mediated resistance to PI3K inhibitors in PTEN-negative tumors within the hypoxic and laminin-rich bone microenvironment.

Generation of Prostate Cancer Patient-Derived Xenografts to Investigate Mechanisms of Novel Treatments and Treatment Resistance

Treatment advances lead to survival benefits of patients with advanced prostate cancer. These treatments are highly efficacious in a subset of patients; however, similarly to other cancers, after initial responses the tumors develop resistance (acquired resistance) and the patients succumb to the disease. Furthermore, there is a subset of patients who do not respond to the treatment at all (de novo resistance). Preclinical testing using patient-derived xenografts (PDXs) has led to successful drug development, and PDXs will continue to provide valuable resources to generate clinically relevant data with translational potential. PDXs demonstrate tumor heterogeneity observed in patients, preserve tumor-microenvironment architecture, and provide clinically relevant treatment responses. In view of the evolving biology of the advanced prostate cancer associated with new treatments, PDXs representing these new tumor phenotypes are urgently needed for the study of treatment responses and resistance. In this chapter, we describe methodologies used to establish prostate cancer PDXs and use of these PDXs to study de novo and acquired resistance.

Analysis of Tim-3 as a therapeutic target in prostate cancer

Tim-3 (T-cell immunoglobulin domain and mucin domain-containing molecule 3) is a newly discovered immunomodulatory protein, which plays an important role in immunity regulation. Recent evidence suggests that Tim-3 is differentially regulated in a variety of tumors and has potential as a therapeutic target. The aim of this study was to investigate the effect of Tim-3 on the development of prostate cancer. Tim-3 expressing on peripheral CD4+ T and CD8+ T cells was analyzed by flow cytometry. The relationships between Tim-3 expression and clinicopathological features were analyzed. Immunohistochemical expression of Tim-3 was examined in our large numbers of paraffin-fixed prostate tissues. Flow cytometry revealed that expression of Tim-3 was significantly increased on both CD4+ and CD8+ T cells in prostate cancer patients than that in benign prostate hyperplasia patients. Also, the level of Tim-3 on CD4+ T cells was positively correlated with CD8+ T cells in patients. Further analyses revealed that the levels of Tim-3 on CD4+ T cells and CD8+ T cells exhibited different expression patterns in terms of localization depending on pathological category of prostate cancer and metastasis. Immunohistochemical analysis revealed that positive staining of Tim-3 in prostate cancer but little or no staining of Tim-3 was observed in benign prostate hyperplasia epithelium. Tim-3 may affect the development and progression of prostate cancer, which may provide knowledge for using Tim-3 as a novel therapy for effective prostate cancer management.

Specific bone region localization of osteolytic versus osteoblastic lesions in a patient-derived xenograft model of bone metastatic prostate cancer

Objective

Bone metastasis occurs in up to 90% of men with advanced prostate cancer and leads to fractures, severe pain and therapy-resistance. Bone metastases induce a spectrum of types of bone lesions which can respond differently to therapy even within individual prostate cancer patients. Thus, the special environment of the bone makes the disease more complicated and incurable. A model in which bone lesions are reproducibly induced that mirrors the complexity seen in patients would be invaluable for pre-clinical testing of novel treatments. The microstructural changes in the femurs of mice implanted with PCSD1, a new patient-derived xenograft from a surgical prostate cancer bone metastasis specimen, were determined.

Methods

Quantitative micro-computed tomography (micro-CT) and histological analyses were performed to evaluate the effects of direct injection of PCSD1 cells or media alone (Control) into the right femurs of Rag2^−/−γc^−/− male mice.

Results

Bone lesions formed only in femurs of mice injected with PCSD1 cells. Bone volume (BV) was significantly decreased at the proximal and distal ends of the femurs (p < 0.01) whereas BV (p < 0.05) and bone shaft diameter (p < 0.01) were significantly increased along the femur shaft.

Conclusion

PCSD1 cells reproducibly induced bone loss leading to osteolytic lesions at the ends of the femur, and, in contrast, induced aberrant bone formation leading to osteoblastic lesions along the femur shaft. Therefore, the interaction of PCSD1 cells with different bone region-specific microenvironments specified the type of bone lesion. Our approach can be used to determine if different bone regions support more therapy resistant tumor growth, thus, requiring novel treatments.

Advances in prostate cancer research models: From transgenic mice to tumor xenografting models

The identification of the origin and molecular characteristics of prostate cancer (PCa) has crucial implications for personalized treatment. The development of effective treatments for PCa has been limited; however, the recent establishment of several transgenic mouse lines and/or xenografting models is better reflecting the disease in vivo. With appropriate models, valuable tools for elucidating the functions of specific genes have gone deep into prostate development and carcinogenesis. In the present review, we summarize a number of important PCa research models established in our laboratories (PSA-Cre-ER^T2/PTEN transgenic mouse models, AP-OX model, tissue recombination-xenografting models and PDX models), which represent advances of translational models from transgenic mouse lines to human tumor xenografting. Better understanding of the developments of these models will offer new insights into tumor progression and may help explain the functional significance of genetic variations in PCa. Additionally, this understanding could lead to new modes for curing PCa based on their particular biological phenotypes.

The future of patient-derived tumor xenografts in cancer treatment

Over the last decades, major technological advancements have led to a better understanding of the molecular drivers of human malignancies. Nonetheless, this progress only marginally impacted the cancer therapeutic approach, probably due to the limited ability of experimental models to predict efficacy in clinical trials. In an effort to offset this limitation, there has been an increasing interest in the development of patient-derived xenograft (PDX) models where human tumors are xenotransplanted into immunocompromised mice. Considering their high resemblance to human tumors and their stability, PDX models are becoming the preferred translational tools in preclinical studies. Nonetheless, several limitations hamper a wider use of PDX models and tarnish the concept that they might represent the missing piece in the personalized medicine puzzle.

An improved intrafemoral injection with minimized leakage as an orthotopic mouse model of osteosarcoma

Osteosarcoma, the most common type of primary bone cancer, is the second highest cause of cancer-related death in pediatric patients. To understand the mechanisms behind osteosarcoma progression and to discover novel therapeutic strategies for this disease, a reliable and appropriate mouse model is essential. For this purpose, osteosarcoma cells need to be injected into the bone marrow. Previously, the intratibial and intrafemoral injection methods were reported; however, the major drawback of these methods is the potential leakage of tumor cells from the injection site during or after these procedures. To overcome this, we have established an improved method to minimize leakage in an orthotopic mouse model of osteosarcoma. By taking advantage of the anatomical benefits of the femur with less bowing and larger medullary cavity than those of the tibia, osteosarcoma cells are injected directly into the femoral cavity following reaming of its intramedullary space. To prevent potential leakage of tumor cells during and after the surgery, the injection site is sealed with bone wax. This method requires a minor surgery of approximately 15min under anesthesia. Our established orthotopic osteosarcoma model could serve as a valuable and reliable tool for examining progression of various types of bone tumors.

Drug discovery in prostate cancer mouse models

INTRODUCTION

The mouse is an important, though imperfect, organism with which to model human disease and to discover and test novel drugs in a preclinical setting. Many experimental strategies have been used to discover new biological and molecular targets in the mouse, with the hopes of translating these discoveries into novel drugs to treat prostate cancer in humans. Modeling prostate cancer in the mouse, however, has been challenging, and often drugs that work in mice have failed in human trials.

AREAS COVERED

The authors discuss the similarities and differences between mice and men; the types of mouse models that exist to model prostate cancer; practical questions one must ask when using a mouse as a model; and potential reasons that drugs do not often translate to humans. They also discuss the current value in using mouse models for drug discovery to treat prostate cancer and what needs are still unmet in field.

EXPERT OPINION

With proper planning and following practical guidelines by the researcher, the mouse is a powerful experimental tool. The field lacks genetically engineered metastatic models, and xenograft models do not allow for the study of the immune system during the metastatic process. There remain several important limitations to discovering and testing novel drugs in mice for eventual human use, but these can often be overcome. Overall, mouse modeling is an essential part of prostate cancer research and drug discovery. Emerging technologies and better and ever-increasing forms of communication are moving the field in a hopeful direction.

PCSD1, a new patient-derived model of bone metastatic prostate cancer, is castrate-resistant in the bone-niche

Introduction

Prostate cancer bone metastasis occurs in 50-90% of men with advanced disease for which there is no cure. Bone metastasis leads to debilitating fractures and severe bone pain. It is associated with therapy resistance and rapid decline. Androgen deprivation therapy (ADT) is standard of care for advanced prostate cancer, however, bone metastatic prostate cancer (PCa) often becomes resistant to ADT. There are few pre-clinical models to understand the interaction between the bone microenvironment and prostate cancer. Here we report the castrate resistant growth in the bone niche of PCSD1, a patient-derived intra-femoral xenograft model of prostate bone metastatic cancer treated with the anti-androgen, bicalutamide.

Methods

PCSD1 bone-niche model was derived from a human prostate cancer femoral metastasis resected during hemiarthroplasty and serially transplanted into Rag2^−/−;γ_c^−/− mice intra-femorally (IF) or sub-cutaneously (SC). At 5 weeks post-transplantation mice received bicalutamide or vehicle control for 18 days. Tumor growth of PCSD1 was measured with calipers. PSA expression in PCSD1 xenograft tumors was determined using quantitative RT-PCR and immunohistochemistry. Expression of AR and PSMA, were also determined with qPCR.

Results

PCSD1 xenograft tumor growth capacity was 24 fold greater in the bone (intra-femoral, IF) than in the soft tissue (sub-cutaneous, SC) microenvironment. Treatment with the anti-androgen, bicalutamide, inhibited tumor growth in the sub-cutaneous transplantation site. However, bicalutamide was ineffective in suppressing PCSD1 tumor growth in the bone-niche. Nevertheless, bicalutamide treatment of intra-femoral tumors significantly reduced PSA expression (p < =0.008) and increased AR (p < =0.032) relative to control.

Conclusions

PCSD1 tumors were castrate resistant when growing in the bone-niche compared to soft tissue. Bicalutamide had little effect on reducing tumor burden in the bone yet still decreased tumor PSA expression and increased AR expression, thus, this model closely recapitulated castrate-resistant, human prostate cancer bone metastatic disease. PCSD1 is a new primary prostate cancer bone metastasis-derived xenograft model to study bone metastatic disease and for pre-clinical drug development of novel therapies for inhibiting therapy resistant prostate cancer growth in the bone-niche.

Analysis of Tim-3 as a therapeutic target in prostate cancer

T cell immunoglobulin domain and mucin domain-containing molecule 3 (Tim-3) is a newly discovered immunomodulatory, which plays an important role in immunity regulation. Recent evidence suggests that Tim-3 is differentially regulated in a variety of tumors and has a potential as a therapeutic target. The aim of this study was to investigate the effect of Tim-3 on the development of prostate cancer (PCa). Tim-3 expressing on peripheral CD4+ T and CD8+ T cells was analyzed by flow cytometry. The relationships between Tim-3 expression and clinicopathological features were analyzed. Immunohistochemical expression of Tim-3 was examined in our large numbers of paraffin-fixed prostate tissues. Flow cytometry revealed that expression of Tim-3 was significantly increased on both CD4+ and CD8+ T cells in PCa patients than that in benign prostate hyperplasia (BPH) patients. Also, the level of Tim-3 on CD4+ T cells was positively correlated with CD8+ T cells in patients. Further analyses revealed that the levels of Tim-3 on CD4+ T cells and CD8+ T cells exhibited different expression patterns in terms of localization depending on pathological category of PCa and metastasis. Immunohistochemical analysis revealed that positive staining of Tim-3 in PCa but little or no staining of Tim-3 was observed in BPH epithelium. Tim-3 may affect the development and progression of PCa, which may provide knowledge for using Tim-3 as a novel therapy for effective PCa management.

Metabolomic studies of human gastric cancer: Review

Metabolomics is a field of study in systems biology that involves the identification and quantification of metabolites present in a biological system. Analyzing metabolic differences between unperturbed and perturbed networks, such as cancerous and non-cancerous samples, can provide insight into underlying disease pathology, disease prognosis and diagnosis. Despite the large number of review articles concerning metabolomics and its application in cancer research, biomarker and drug discovery, these reviews do not focus on a specific type of cancer. Metabolomics may provide biomarkers useful for identification of early stage gastric cancer, potentially addressing an important clinical need. Here, we present a short review on metabolomics as a tool for biomarker discovery in human gastric cancer, with a primary focus on its use as a predictor of anticancer drug chemosensitivity, diagnosis, prognosis, and metastasis.

Docetaxel-carboxymethylcellulose nanoparticles display enhanced anti-tumor activity in murine models of castration-resistant prostate cancer

Docetaxel (DTX) remains the only effective drug for prolonging survival and improving quality of life of metastatic castration resistant prostate cancer (mCRPC) patients. Despite some clinical successes with DTX-based therapies, advent of cumulative toxicity and development of drug resistance limit its long-term clinical application. The integration of nanotechnology for drug delivery can be exploited to overcome the major intrinsic limitations of DTX therapy for mCRPC. We evaluated whether reformulation of DTX by facile conjugation to carboxymethylcellulose nanoparticles (Cellax) can improve the efficacy and safety of the drug in s.c. and bone metastatic models of CRPC. A single dose of the nanoparticles completely regressed s.c. PC3 tumor xenografts in mice. In addition, Cellax elicited fewer side effects compared to native DTX. Importantly, Cellax did not increase the expression of drug resistance molecules in androgen-independent PC3 prostate cancer cells in comparison with DTX. Lastly, in a bone metastatic model of CRPC, Cellax treatment afforded a 2- to 3-fold improvement in survival and enhancements in quality-of-life of the animals over DTX and saline controls. These results demonstrate the potential of Cellax in improving the treatment of mCRPC.

Osteoblasts stimulate the osteogenic and metastatic progression of castration-resistant prostate cancer in a novel model for in vitro and in vivo studies

Castration-resistant prostate cancer (CRPC) is strongly associated with sclerotic bone metastases and poor prognosis. Models that mimic human CRPC are needed to identify the mechanisms for prostate cancer (PC) growth in bone and to develop new therapeutic strategies. We characterize a new model, LNCaP-19, and investigate the interaction between tumor cells and osteoblasts in the sclerotic tumor response of CRPC. Osteogenic profiling of PC cell lines (LNCaP-19, LNCaP, C4-2B₄, and PC-3) was performed by gene expression arrays and mineral staining. Conditioned medium from MC3T3-E1 was used for osteoblast stimulation of CRPC cells. The capacity of LNCaP-19 cells to induce sclerotic lesions was assessed in intratibial xenografts and verified by serum markers, histological analysis and bone mineral density (BMD) measurements. The CRPC cell line LNCaP-19 expresses a pronounced osteogenic profile compared to its parental androgen-dependent cell line LNCaP. Osteoblast-derived factors further increase the expression of genes known to enhance metastatic progression of PC. LNCaP-19 forms sclerotic tumors in tibia of castrated mice as evident by increased total BMD (P < 0.01). There was a strong correlation between serum osteocalcin and BMD (total: R² 0.811, P < 0.01, trabecular: R² 0.673, P < 0.05). For the first time we demonstrate that a CRPC cell line generated in vitro has osteogenic capacity and that osteomimicry can be an inherent feature of these cells. Osteoblast-derived factors further promote the osteogenic and metastatic phenotype in CRPC cells. Altogether, our model demonstrates that both tumor cells and osteoblasts are mediators of the bone forming process of CRPC.

One mouse, one patient paradigm: New avatars of personalized cancer therapy

Over the last few decades, study of cancer in mouse models has gained popularity. Sophisticated genetic manipulation technologies and commercialization of these murine systems have made it possible to generate mice to study human disease. Given the large socio-economic burden of cancer, both on academic research and the health care industry, there is a need for in vivo animal cancer models that can provide a rationale that is translatable to the clinic. Such a bench-to-bedside transition will facilitate a long term robust strategy that is economically feasible and clinically effective to manage cancer. The major hurdles in considering mouse models as a translational platform are the lack of tumor heterogeneity and genetic diversity, which are a hallmark of human cancers. The present review, while critical of these pitfalls, discusses two newly emerging concepts of personalized mouse models called "Mouse Avatars" and Co-clinical Trials. Development of "Mouse Avatars" entails implantation of patient tumor samples in mice for subsequent use in drug efficacy studies. These avatars allow for each patient to have their own tumor growing in an in vivo system, thereby allowing the identification of a personalized therapeutic regimen, eliminating the cost and toxicity associated with non-targeted chemotherapeutic measures. In Co-clinical Trials, genetically engineered mouse models (GEMMs) are used to guide therapy in an ongoing human patient trial. Murine and patient trials are conducted concurrently, and information obtained from the murine system is applied towards future clinical management of the patient's tumor. The concurrent trials allow for a real-time integration of the murine and human tumor data. In combination with several molecular profiling techniques, the "Mouse Avatar" and Co-clinical Trial concepts have the potential to revolutionize the drug development and health care process. The present review outlines the current status, challenges and the future potential of these two new in vivo approaches in the field of personalized oncology.

SATB1 is overexpressed in metastatic prostate cancer and promotes prostate cancer cell growth and invasion

Background

Special AT-rich sequence binding protein 1 (SATB1) is a nuclear factor that functions as the global chromatin organizer to regulate chromatin structure and gene expression gene expression. SATB1 has been shown to be abnormally expressed in various types of cancer. However, the expression and role of SATB1 in prostate cancer remain unclear.

Methods

120 cases of prostatic carcinoma and 60 cases of benign prostate hyperplasia were analyzed for SATB1 expression by immunohistochemistry. LNCaP, DU-145, and PC3 prostate cancer cells were examined for SATB1 expression by Western blot analysis. Cell proliferation and invasion was evaluated by CCK8 and transwell invasion assay, respectively.

Results

SATB1 staining was stronger in prostatic carcinomas with metastasis than in those without metastasis, but was absent in benign prostate hyperplasia. Furthermore, SATB1 expression was positively correlated with bone metastasis and the Gleason score. SATB1 overexpression promoted the proliferation and invasion of LNCaP cells while SATB1 knockdown inhibited the proliferation and invasion of DU-145 cells.

Conclusions

These findings provide novel insight into oncogenic role of SATB1 in prostate cancer, suggesting that SATB1 is a promising biomarker and therapeutic target for prostate cancer.

A preclinical xenograft model of prostate cancer using human tumors

Most cases of prostate cancer are now diagnosed as moderate-grade localized disease. These tumor specimens are important tools in the discovery and translation of prostate cancer research; however, unlike more advanced tumors, they are notoriously difficult to grow in the laboratory. We developed a system for efficiently xenografting localized human prostate cancer tissue, and we adapted this protocol to study the interactions between the specific subsets of epithelial and stromal cells. Fresh prostate tissues or isolated epithelial cells are recombined with mouse seminal vesicle mesenchyme (SVM) and grafted under the renal capsule of immunodeficient mice for optimum growth and survival. Alternatively, mouse mesenchyme can be replaced with human prostate fibroblasts in order to determine their contribution to tumor progression. Grafts can be grown for several months to determine the effectiveness of novel therapeutic compounds when administered to host mice, thereby paving the way for personalizing the treatment of individual prostate cancers.

Development of a locally advanced orthotopic prostate tumor model in rats for assessment of combined modality therapy

The purpose of this study was to develop an aggressive locally advanced orthotopic prostate cancer model for assessing high-dose image-guided radiation therapy combined with biological agents. For this study, we used a modified human prostate cancer (PCa) cell line, PC3, in which we knocked down a tumor suppressor protein, DAB2IP (PC3‑KD). These prostate cancer cells were implanted into the prostate of nude or Copenhagen rats using either open surgical implantation or a minimally invasive procedure under ultrasound guidance. We report that: i) these DAB2IP-deficient PCa cells form a single focus of locally advanced aggressive tumors in both nude and Copenhagen rats; ii) the resulting tumors are highly aggressive and are poorly controlled after treatment with radiation alone; iii) ultrasound-guided tumor cell implantation can be used successfully for tumor development in the rat prostate; iv) precise measurement of the tumor volume and the treatment planning for radiation therapy can be obtained from ultrasound and MRI, respectively; and v) the use of a fiducial marker for enhanced radiotherapy localization in the rat orthotopic tumor. This model recapitulates radiation-resistant prostate cancers which can be used to demonstrate and quantify therapeutic response to combined modality treatments.