Differential expression of angiopoietin-2 and vascular endothelial growth factor in androgen-independent prostate cancer models

Sensitivity of magnetic resonance elastography to extracellular matrix and cell motility in human prostate cancer cell line-derived xenograft models

Prostate cancer (PCa) is a significant health problem in the male population of the Western world. Magnetic resonance elastography (MRE), an emerging medical imaging technique sensitive to mechanical properties of biological tissues, detects PCa based on abnormally high stiffness and viscosity values. Yet, the origin of these changes in tissue properties and how they correlate with histopathological markers and tumor aggressiveness are largely unknown, hindering the use of tumor biomechanical properties for establishing a noninvasive PCa staging system. To infer the contributions of extracellular matrix (ECM) components and cell motility, we investigated fresh tissue specimens from two PCa xenograft mouse models, PC3 and LNCaP, using magnetic resonance elastography (MRE), diffusion-weighted imaging (DWI), quantitative histology, and nuclear shape analysis. Increased tumor stiffness and impaired water diffusion were observed to be associated with collagen and elastin accumulation and decreased cell motility. Overall, LNCaP, while more representative of clinical PCa than PC3, accumulated fewer ECM components, induced less restriction of water diffusion, and exhibited increased cell motility, resulting in overall softer and less viscous properties. Taken together, our results suggest that prostate tumor stiffness increases with ECM accumulation and cell adhesion - characteristics that influence critical biological processes of cancer development. MRE paired with DWI provides a powerful set of imaging markers that can potentially predict prostate tumor development from benign masses to aggressive malignancies in patients. STATEMENT OF SIGNIFICANCE: Xenograft models of human prostate tumor cell lines, allowing correlation of microstructure-sensitive biophysical imaging parameters with quantitative histological methods, can be investigated to identify hallmarks of cancer.

In Situ Detection of Hydrogen Sulfide in 3D-Cultured, Live Prostate Cancer Cells Using a Paper-Integrated Analytical Device

In this study, a paper-integrated analytical device that combined a paper-based colorimetric assay with a paper-based cell culture platform was developed for the in situ detection of hydrogen sulfide (H2S) in three-dimensional (3D)-cultured, live prostate cancer cells. Two kinds of paper substrates were fabricated using a simple wax-printing methodology to form the cell culture and detection zones, respectively. LNCaP cells were seeded directly on the paper substrate and grown in the paper-integrated analytical device. The cell viability and H2S production of LNCaP cells were assessed using a simple water-soluble tetrazolium salt colorimetric assay and H2S-sensing paper, respectively. The H2S-sensing paper showed good sensitivity (sensitivity: 6.12 blue channel intensity/μM H2S, R2 = 0.994) and a limit of quantification of 1.08 μM. As a result, we successfully measured changes in endogenous H2S production in 3D-cultured, live LNCaP cells within the paper-integrated analytical device while varying the duration of incubation and substrate concentration (L-cysteine). This paper-integrated analytical device can provide a simple and effective method to investigate H2S signaling pathways and drug screening in a 3D culture model.

Tumor Microenvironment in Prostate Cancer: Toward Identification of Novel Molecular Biomarkers for Diagnosis, Prognosis, and Therapy Development

Prostate cancer (PCa) is by far the most commonly diagnosed cancer in men worldwide. Despite sensitivity to androgen deprivation, patients with advanced disease eventually develop resistance to therapy and may die of metastatic castration-resistant prostate cancer (mCRPC). A key challenge in the management of PCa is the clinical heterogeneity that is hard to predict using existing biomarkers. Defining molecular biomarkers for PCa that can reliably aid in diagnosis and distinguishing patients who require aggressive therapy from those who should avoid overtreatment is a significant unmet need. Mechanisms underlying the development of PCa are not confined to cancer epithelial cells, but also involve the tumor microenvironment. The crosstalk between epithelial cells and stroma in PCa has been shown to play an integral role in disease progression and metastasis. A number of key markers of reactive stroma has been identified including stem/progenitor cell markers, stromal-derived mediators of inflammation, regulators of angiogenesis, connective tissue growth factors, wingless homologs (Wnts), and integrins. Here, we provide a synopsis of the stromal-epithelial crosstalk in PCa focusing on the relevant molecular biomarkers pertaining to the tumor microenvironment and their role in diagnosis, prognosis, and therapy development.

Quantitative and correlative biodistribution analysis of 89Zr-labeled mesoporous silica nanoparticles intravenously injected into tumor-bearing mice

The biodistribution of ⁸⁹Zr-labeled mesoporous silica nanoparticles (MSNs) was evaluated in detail using a prostate cancer mouse model bearing LNCaP C4-2 and PC-3 tumor xenografts with focus on passive targeting. PEGylation of radiolabeled MSNs significantly improved the blood circulation times and radically enhanced the accumulation in tumors comparable to the accumulation levels previously reported for similar but actively targeted particles. The distribution of the passively targeted MSNs was related to the degree of vascularization of the tumors and did not follow the trends observed in vitro. Correlative analyses of organ-to-blood ratios revealed that little or no accumulation of the particles is observed in the lungs, heart, and brain, and that the particles detected were present in the blood pool. On the other hand, clear accumulation was observed in the liver and spleen, in addition to the uptake in the tumors. The accumulation of particles in the kidney did not correlate with the MSN concentration in the blood, but indicated a rather steady level of particles in the kidney. The results, which partly contradict previous studies, highlight the importance of correlative analyses in order to evaluate the organ accumulation of particles.

Castration resistant prostate cancer is associated with increased blood vessel stabilization and elevated levels of VEGF and Ang-2

BACKGROUND

Angiogenesis is important for the progression of prostate cancer and may be a target for treatment in castration resistant (CR) disease. This study was performed to investigate blood vessel stabilization and expression of the pro-angiogenic factors vascular endothelial growth factor (VEGF) and Angiopoietin-2 (Ang-2) in CR and hormone naïve (HN) prostate cancer. The effect of androgen deprivation therapy (ADT) on these parameters was also studied.

METHODS

VEGF and Ang-2, as well as pericyte coverage of blood vessels were studied in HN and CR prostate tumors by immunohistochemistry. The effects of ADT on VEGF expression and microvessel density (MVD) were investigated in biopsies at diagnosis, 3 months after starting ADT and at tumor relapse. Plasma was also analyzed for VEGF and Ang-2 with ELISA.

RESULTS

CR tumors had higher levels of VEGF and Ang-2 as well as increased blood vessel stabilization compared to HN tumors. Three months after initiated ADT an increase of VEGF but not MVD in the tumors was observed. In contrast, plasma levels of VEGF decreased after ADT, and increased again at time of tumor relapse. Ang-2 levels were unaffected.

CONCLUSIONS

CR prostate cancer is associated with elevated levels of VEGF and Ang-2, indicating that these factors could be used as targets for anti-angiogenic treatment. Still, the observed increase in blood vessel stabilization in CR tumors could influence the outcome of anti-angiogenic treatment. Furthermore, increased VEGF expression after 3 months of ADT justifies the use of VEGF-based anti-angiogenic drugs in combination with ADT for the treatment of advanced prostate cancer.

Multi-biomarker pattern for tumor identification and prognosis

In last decades, the basic, clinical, and translational research efforts have been directed to the identification of standard biomarkers associated with the degree of malignancy. There is an increasingly public health concern for earlier detection of cancer development at stages in which successful treatments can be achieved. To meet this urgent clinical demand, early stage cancer biomarkers supported by reliable and robust experimental data that can be readily applicable in the clinical practice, are required. In the current standard protocols, when one or two of the canonical proliferating index biomarkers are analyzed, contradictory results are frequently reached leading to incorrect cancer diagnostic and unsuccessful therapies. Therefore, the identification of other cellular characteristics or signatures present in the tumor cells either alone or in combination with the well-established proliferation markers emerge as an alternative strategy in the improvement of cancer diagnosis and treatment. Because it is well known that several pathways and processes are altered in tumor cells, the concept of "single marker" in cancer results incorrect. Therefore, this review aims to analyze and discuss the proposal that the molecular profile of different genes or proteins in different altered tumor pathways must be established to provide a better global clinical pattern for cancer detection and prognosis.

Expression profile of apoptosis related genes and radio-sensitivity of prostate cancer cells

Radio-resistant or recurrent prostate cancer represents a serious health risk for approximately 20%-30% of patients treated with primary radiation therapy for clinically localized prostate cancer. In the present study, we investigated the expression profiles of 84 genes involved in various apoptosis pathways in two prostate cancer cell lines LNCaP (P53+ and AR+) and PC3 (P53- and AR-). We also studied the effect of monensin, an apoptosis inducing reagent, in X-ray-induced cell killing. Comparison of gene expressions between unirradiated LNCaP and PC3 cells revealed distinguished gene expression patterns. The data showed a significantly higher expression level of genes involved in the caspase/card family and the TNF ligand/receptor family in PC3 cells, whereas, LNCaP cells exhibited higher expressions in the p53 related genes. At 2 and 4 hrs post a 10 Gy X-ray exposure, changes of gene expressions were detected in a significant fraction of the genes in LNCaP cells, but no significant changes were found in PC3 cells. There was no significant apoptosis-inducing effect of X-rays (up to 10 Gy) in both cell lines; however, monensin was shown to be effective in inducing apoptosis in LNCaP, but not in PC3 cells. In addition, the effect of combined treatment of monensin and X-rays in LNCaP cells appeared to be synergistic. Our results suggest that monensin may be effective for both cancer cell killing and radiosensitizing, and the different expression profiles in apoptosis related genes in cancer cells may be correlated with their sensitivity to apoptosis inducing reagents.

Specifically targeting angiopoietin-2 inhibits angiogenesis, Tie2-expressing monocyte infiltration, and tumor growth

PURPOSE

Angiopoietin-1 (Ang1) plays a key role in maintaining stable vasculature, whereas in a tumor Ang2 antagonizes Ang1's function and promotes the initiation of the angiogenic switch. Specifically targeting Ang2 is a promising anticancer strategy. Here we describe the development and characterization of a new class of biotherapeutics referred to as CovX-Bodies, which are created by chemical fusion of a peptide and a carrier antibody scaffold.

EXPERIMENTAL DESIGN

Various linker tethering sites on peptides were examined for their effect on CovX-Body in vitro potency and pharmacokinetics. Ang2 CovX-Bodies with low nmol/L IC(50)s and significantly improved pharmacokinetics were tested in tumor xenograft studies alone or in combination with standard of care agents. Tumor samples were analyzed for target engagement, via Ang2 protein level, CD31-positive tumor vasculature, and Tie2 expressing monocyte penetration.

RESULTS

Bivalent Ang2 CovX-Bodies selectively block the Ang2-Tie2 interaction (IC(50) < 1 nmol/L) with dramatically improved pharmacokinetics (T(½) > 100 hours). Using a staged Colo-205 xenograft model, significant tumor growth inhibition (TGI) was observed (40%-63%, P < 0.01). Ang2 protein levels were reduced by approximately 50% inside tumors (P < 0.01), whereas tumor microvessel density (P < 0.01) and intratumor proangiogenic Tie2(+)CD11b(+) cells (P < 0.05) were significantly reduced. When combined with sunitinib, sorafenib, bevacizumab, irinotecan, or docetaxel, Ang2 CovX-Bodies produced even greater efficacy (∼80% TGI, P < 0.01).

CONCLUSION

CovX-Bodies provide an elegant solution to overcome the pharmacokinetic-pharmacodynamic problems of peptides. Long-acting Ang2 specific CovX-Bodies will be useful as single agents and in combination with standard-of-care agents.

Inhibition of angiopoietin-2 in LuCaP 23.1 prostate cancer tumors decreases tumor growth and viability

BACKGROUND

Angiopoietin-2 is expressed in prostate cancer (PCa) bone, liver, and lymph node metastases, whereas, its competitor angiopoietin-1 has limited expression in these tissues. Therefore, we hypothesized that the inhibition of angiopoietin-2 activity in PCa will impede angiogenesis, tumor growth, and alter bone response in vivo.

METHODS

To test our hypothesis we used L1-10, a peptide-Fc fusion that inhibits interactions between angiopoietin-2 and its receptor tie2. We blocked angiopoietin-2 activity using L1-10 in established subcutaneous and intra-tibial LuCaP 23.1 xenografts. We then determined the effect of L1-10 on survival, tumor growth, serum PSA, proliferation, microvessel density, and angiogenesis-associated gene expression in subcutaneous tumors. We also determined serum PSA, tumor area, and bone response in intra-tibial tumors.

RESULTS

The administration of L1-10 decreased tumor volume and serum PSA, and increased survival in SCID mice bearing subcutaneous LuCaP 23.1 tumors. Histomorphometric analysis, showed a further significant decrease in tumor epithelial area within the L1-10 treated LuCaP 23.1 subcutaneous tumors (P=0.0063). There was also a significant decrease in cell proliferation (P=0.012), microvessel density (P=0.012), and a significant increase in ANGPT-2 and HIF-1α mRNA expression (P≤0.05) associated with L1-10 treatment. Alternatively, in LuCaP 23.1 intra-tibial tumors L1-10 treatment did not significantly change serum PSA, tumor area or bone response.

CONCLUSIONS

Our results demonstrate that inhibiting angiopoietin-2 activity impedes angiogenesis and growth of LuCaP 23.1 PCa xenografts. Based on these data, we hypothesize that angiopoietin-2 inhibition in combination with other therapies may represent a potential therapy for patients with metastatic disease.

Angiogenesis as a strategic target for prostate cancer therapy

It is becoming increasingly clear that angiogenesis plays a crucial role in prostate cancer (CaP) survival, progression, and metastasis. Tumor angiogenesis is a hallmark of advanced cancers and an attractive treatment target in multiple solid tumors. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in CaP, the rational design of targeted therapeutics is possible. This review summarizes the recent advancements that have improved our understanding of the role of angiogenesis in CaP metastasis and the potential therapeutic efficacy of inhibiting angiogenesis in this disease. Current therapeutic options for patients with metastatic hormone-refractory CaP are very limited. Targeting vasculature is a developing area, which shows promise for the control of late stage and recurrent CaP disease and for overcoming drug resistance. We discuss angiogenesis and its postulated mechanisms and focus on the regulation of angiogenesis in CaP progression and the therapeutic beneficial effects associated with targeting of the CaP vasculature to overcome the resistance to current treatments and CaP recurrence.

The prostatic environment suppresses growth of androgen-independent prostate cancer xenografts: an effect influenced by testosterone

BACKGROUND

Interactions between prostate cancer cells and their surrounding stroma play an important role in the growth and maintenance of prostate tumors. To elucidate this further, we investigated how growth of androgen-dependent (AD) LNCaP and androgen-independent (AI) LNCaP-19 prostate tumors was affected by different microenvironments and androgen levels.

METHODS

Tumor cells were implanted subcutaneously and orthotopically in intact and castrated immunodeficient mice. Orthotopic tumor growth was followed by magnetic resonance imaging (MRI). Gene expression in the tumors was evaluated by means of microarray analysis and microvessel density (MVD) was analyzed using immunohistochemistry.

RESULTS

The results showed that LNCaP-19 tumors grew more rapidly at the subcutaneous site than in the prostate, where tumors were obviously inhibited. Castration of the mice did not affect ectopic tumors but did result in increased tumor growth in the prostatic environment. This effect was reversed by testosterone treatment. In contrast to LNCaP-19, the LNCaP cells grew rapidly in the prostate and castration reduced tumor development. Gene expression analysis of LNCaP-19 tumors revealed an upregulation of genes, inhibiting tumor growth (including ADAMTS1, RGS2 and protocadherin 20) and a downregulation of genes, promoting cell adhesion and metastasis (including N-cadherin and NRCAM) in the slow-growing orthotopic tumors from intact mice.

CONCLUSIONS

The results show that the prostatic environment has a varying impact on AD and AI tumor xenografts. Data indicate that the androgen-stimulated prostatic environment limits growth of orthotopic AI tumors through induction of genes that inhibit tumor growth and suppression of genes that promote cell adhesion and metastasis.

Unique patterns of molecular profiling between human prostate cancer LNCaP and PC-3 cells

BACKGROUND

Human prostate cancer LNCaP and PC-3 cell lines have been extensively used to study prostate cancer progression and to develop therapeutic agents. Although LNCaP and PC-3 cells are generally assumed to represent early and late stages of prostate cancer, respectively, there is limited information regarding gene expression patterns between these two cell lines and its relationship to prostate cancer.

METHODS

Comprehensive gene expression analysis was performed. Total RNA was isolated from cultured cells and hybridized to Illumina human BeadChips representing 24,526 transcripts. Bioinformatics analysis was applied to identify cell line specific genes as well as biological mechanisms, pathways, and functions related to the genes.

RESULTS

A total of 2,198 genes were differentially expressed between LNCaP and PC-3 cells. Using a robust statistical analysis and high significance criteria, 115 and 188 genes were identified to be unique to LNCaP and PC-3 cells, respectively. LNCaP cells maintained various metabolic pathways including a gene cluster that encodes UDP-glucuronosyltransferases. Several transcription factors including Tal alpha/beta, GATA-1, and c-Myc/Max may be responsible for regulating LNCaP cell specific genes. By contrast, PC-3 cells were characterized by their unique expression of cytoskeleton-related genes and other genes including VEGFC, IL8, and TGF beta 2.

CONCLUSIONS

This study showed that LNCaP and PC-3 cells represent two distinct prostate cancer cell lineages. LNCaP cells retain many prostate cell specific properties, whereas PC-3 cells have acquired a more aggressive phenotype. Future studies for prostate cancer research need to consider similarities and differences between these two cells and their relationship to prostate cancer.