Spontaneous metastasis of PC-3 cells in athymic mice after implantation in orthotopic or ectopic microenvironments

Orthotopic and metastatic tumour models in preclinical cancer research

Mouse models of disease play a pivotal role at all stages of cancer drug development. Cell-line derived subcutaneous tumour models are predominant in early drug discovery, but there is growing recognition of the importance of the more complex orthotopic and metastatic tumour models for understanding both target biology in the correct tissue context, and the impact of the tumour microenvironment and the immune system in responses to treatment. The aim of this review is to highlight the value that orthotopic and metastatic models bring to the study of tumour biology and drug development while pointing out those models that are most likely to be encountered in the literature. Important developments in orthotopic models, such as the increasing use of early passage patient material (PDXs, organoids) and humanised mouse models are discussed, as these approaches have the potential to increase the predictive value of preclinical studies, and ultimately improve the success rate of anticancer drugs in clinical trials.

MicroRNA-362 negatively and positively regulates SMAD4 expression in TGF-β/SMAD signaling to suppress cell migration and invasion

Cell migration and invasion are modulated by epithelial-to-mesenchymal transition (EMT) and the reverse MET process. Despite the detection of microRNA-362 (miR-362, both the miR-362-5p and -3p species) in cancers, none of the identified miR-362 targets is a mesenchymal or epithelial factor to link miR-362 with EMT/MET and metastasis. Focusing on the TGF-β/SMAD signaling pathway in this work, luciferase assays and western blot data showed that miR-362 targeted and negatively regulated expression of SMAD4 and E-cadherin, but not SNAI1, which is regulated by SMAD4. However, miR-362 knockdown also down-regulated SMAD4 and SNAI1, but up-regulated E-cadherin expression. Wound-healing and transwell assays further showed that miR-362 knockdown suppressed cell migration and invasion, effects which were reversed by over-expressing SMAD4 or SNAI1, or by knocking down E-cadherin in the miR-362 knockdown cells. In orthotopic mice, miR-362 knockdown inhibited metastasis, and displayed the same SMAD4 and E-cadherin expression profiles in the tumors as in the in vitro studies. A scheme is proposed to integrate miR-362 negative regulation via SMAD4, and to explain miR-362 positive regulation of SMAD4 via miR-362 targeting of known SMAD4 suppressors, BRK and DACH1, which would have resulted in SMAD4 depletion and annulment of subsequent involvement in TGF-β signaling actions. Hence, miR-362 both negatively and positively regulates SMAD4 expression in TGF-β/SMAD signaling pathway to suppress cell motility and invasiveness and metastasis, and may explain the reported clinical association of anti-miR-362 with suppressed metastasis in various cancers. MiR-362 knockdown in miR-362-positive cancer cells may be used as a therapeutic strategy to suppress metastasis.

Patterns of Vasculature in Mouse Models of Lung Cancer Are Dependent on Location

PURPOSE

Preclinical studies of hypoxia are generally done using ectopic xenograft tumors, which behave differently from human tumors. Our previous findings have shown that subcutaneously implanted lung tumors exhibit more hypoxia than their orthotopic implanted or spontaneous K-ras-induced counterparts. We hypothesize that differences in hypoxia are due to site-specific differences in vascularity and perfusion.

PROCEDURES

To compare the presence and functionality of vessels in these tumor models, we studied vascular perfusion in vivo in real time.

RESULTS

Orthotopically implanted and spontaneous K-ras-induced lung tumors showed elevated perfusion, demonstrating vasculature functionality. Little contrast agent uptake was observed within the subcutaneously implanted tumors, indicating vascular dysfunction. These findings were corroborated at the microscopic level with Hoechst 33342 and Meca-32 staining.

CONCLUSIONS

From these observations, we concluded that differences in hypoxia in experimental models is related to vessel perfusion. Thus, appropriate selection of preclinical lung tumor models is essential for the study of hypoxia, angiogenesis and therapies targeting these phenomena.

Structure and Function of a Prostate Cancer Dissemination-Permissive Extracellular Matrix

Purpose: The poor prognosis of metastatic prostate cancer continues to present a major challenge in prostate cancer treatment. The tumor extracellular matrix (ECM) plays an important role in facilitating metastasis. Here, we investigated the structure and function of an ECM that facilitates prostate cancer metastasis by comparing orthotopic tumors that frequently metastasize to poorly metastatic subcutaneous tumors.Experimental Design: Both tumors were derived from a human prostate cancer PC3 cell line engineered to fluoresce under hypoxia. Second harmonic generation (SHG) microscopy was used to characterize collagen 1 (Col1) fiber patterns in the xenografts as well as in human samples. MRI was used to determine albumin-Gd-diethylenetriaminepenta-acetate (alb-GdDTPA) transport through the ECM using a saturation recovery MR method combined with fast T₁ SNAPSHOT-FLASH imaging. Cancer-associated fibroblasts (CAF) were also quantified in these tumors.Results: Significant structural and functional differences were identified in the prometastatic orthotopic tumor ECM compared to the less metastatic subcutaneous tumor ECM. The significantly higher number of CAFs in orthotopic tumors may explain the higher Col1 fiber volumes in these tumors. In vivo, alb-GdDTPA pooling was significantly elevated in metastatic orthotopic tumors, consistent with the increased Col1 fibers.Conclusions: Developing noninvasive MRI indices of macromolecular transport, together with characterization of Col1 fiber patterns and CAFs can assist in stratifying prostate cancers for aggressive treatments or active surveillance. These results highlight the role of CAFs in supporting or creating aggressive cancers, and the importance of depleting CAFs to prevent metastatic dissemination in prostate cancer. Clin Cancer Res; 23(9); 2245-54. ©2016 AACR.

Metastatic phenotype in CWR22 prostate cancer xenograft following castration

BACKGROUND

CWR22 is a human xenograft model of primary prostate cancer (PCa) that is often utilized to study castration recurrent (CR) PCa. CWR22 recapitulates clinical response to androgen deprivation therapy (ADT), in that tumors regress in response to castration, but can recur after a period of time.

METHODS

Two cohorts of mice, totaling 117 mice were implanted with CWR22, allowed to develop tumors, castrated by pellet removal and followed for a period of 32 and 50 weeks. Mice presenting with tumors >2.0 cm(3) at the primary site, moribund appearance, or palpable masses other than the primary tumor were sacrificed prior to the endpoint of the study. Tumor tissue, serum, and abnormal lesions were collected upon necropsy and analyzed by IHC, H&E, and PCR for presence of metastatic lesions arising from CWR22.

RESULTS

Herein, we report that CWR22 progresses after castration from a primary, hormonal therapy-naïve tumor to metastatic disease in 20% of castrated nude mice. Histological examination of CWR22 primary tumors revealed distinct pathologies that correlated with metastatic outcome after castration.

CONCLUSION

This is the first report and characterization of spontaneous metastasis in the CWR22 model, thus, CWR22 is a bona-fide model of clinical PCa representing the full progression from androgen-sensitive, primary PCa to metastatic CR-PCa.

TRAIL-coated leukocytes that prevent the bloodborne metastasis of prostate cancer

Prostate cancer, once it has progressed from its local to metastatic form, is a disease with poor prognosis and limited treatment options. Here we demonstrate an approach using nanoscale liposomes conjugated with E-selectin adhesion protein and Apo2L/TRAIL (TNF-related apoptosis-inducing ligand) apoptosis ligand that attach to the surface of leukocytes and rapidly clear viable cancer cells from circulating blood in the living mouse. For the first time, it is shown that such an approach can be used to prevent the spontaneous formation and growth of metastatic tumors in an orthotopic xenograft model of prostate cancer, by greatly reducing the number of circulating tumor cells. We conclude that the use of circulating leukocytes as a carrier for the anti-cancer protein TRAIL could be an effective tool to directly target circulating tumor cells for the prevention of prostate cancer metastasis, and potentially other cancers that spread through the bloodstream.

Tumor models for prostate cancer exemplified by fibroblast growth factor 8-induced tumorigenesis and tumor progression

Prostate cancer is a very common malignancy among Western males. Although most tumors are indolent and grow slowly, some grow and metastasize aggressively. Because prostate cancer growth is usually androgen-dependent, androgen ablation offers a therapeutic option to treat post-resection tumor recurrence or primarily metastasized prostate cancer. However, patients often relapse after the primary response to androgen ablation therapy, and there is no effective cure for cases of castration-resistant prostate cancer (CRPC). The mechanisms of tumor growth in CRPC are poorly understood. Although the androgen receptors (ARs) remain functional in CRPC, other mechanisms are clearly activated (e.g., disturbed growth factor signaling). Results from our laboratory and others have shown that dysregulation of fibroblast growth factor (FGF) signaling, including FGF receptor 1 (FGFR1) activation and FGF8b overexpression, has an important role in prostate cancer growth and progression. Several experimental models have been developed for prostate tumorigenesis and various stages of tumor progression. These models include genetically engineered mice and rats, as well as induced tumors and xenografts in immunodeficient mice. The latter was created using parental and genetically modified cell lines. All of these models greatly helped to elucidate the roles of different genes in prostate carcinogenesis and tumor progression. Recently, patient-derived xenografts have been studied for possible use in testing individual, specific responses of tumor tissue to different treatment options. Feasible and functional CRPC models for drug responsiveness analysis and the development of effective therapies targeting the FGF signaling pathway and other pathways in prostate cancer are being actively investigated.

Longitudinal anatomical and metabolic MRI characterization of orthotopic xenograft prostate tumors in nude mice

PURPOSE

To assess anatomic and functional magnetic resonance imaging (MRI) for monitoring of tumor volume and metabolism of orthotopic xenograft prostate cancer tumors.

MATERIALS AND METHODS

Human-derived PC-3M cells were implanted into the prostate in 22 nude mice. Tumor volume and MRI appearance were monitored for up to 29 days. Histology was performed to detect metastases. Hyperpolarized [1-(13) C]pyruvate MRI was used to measure tumor metabolism on day 22.

RESULTS

Tumors were visible by MRI 9 days after tumor cell implantation. Tumor volume increased to 720 ± 190 mm(3) on day 29 of imaging. Metastasis was seen in the iliac lymph nodes at all timepoints, and in more distant lymph nodes at later timepoints, but was not detectable by MRI. Regions with low pyruvate uptake corresponded to regions with necrosis and had a higher lactate/pyruvate ratio (0.98 ± 0.4 vs. 1.6 ± 1.1).

CONCLUSION

MRI using the balanced steady-state free precession (bSSFP) sequence can be used to monitor tumor growth in orthotopic PC-3M tumors as early as 9 days post-injection. Hyperpolarized pyruvate MRI has potential to assess tumor metabolism and necrosis.

New cast for a new era: preclinical cancer drug development revisited

Molecularly targeted agents promise to revolutionize therapeutics by reducing morbidity and mortality in patients with cancer. However, despite an urgent need for more effective anticancer compounds, current preclinical drug evaluations largely fail to satisfy the demand. New preclinical strategies, including the improvement of sophisticated mouse models and co-clinical study designs, are being used to augment the predictive value of animal-based translational cancer research. Here, we review the development of successful preclinical antineoplastic agents, their associated limitations, and alternative methods to predict clinical outcomes.

Noninvasive multiparametric imaging of metastasis-permissive microenvironments in a human prostate cancer xenograft

Metastasis continues to be one of the major causes of mortality from prostate cancer. Because human malignant cell lines metastasize more readily from orthotopic sites than from heterotopic sites, to identify metastasis-permissive tumor microenvironments, we used noninvasive imaging to compare the in vivo vascular, metabolic, and physiologic characteristics of a human prostate cancer xenograft implanted orthotopically in the prostate or s.c. in the flank. Hypoxia was detected in these xenografts by placing an enhanced green fluorescence protein optical reporter under the control of a hypoxia response element. A multiparametric analysis of hypoxia, extracellular pH, vascularization, and metabolism provided a characterization of environments that are permissive for metastasis to occur. We found that orthotopic tumors, which metastasized more easily, were characterized by higher vascular volume, permeability, and total choline and a more acidic extracellular pH. Interestingly, metastatic deposits in the lymph nodes as well as cancer cells in ascites fluid were found to be hypoxic, explaining, in part, the refractory nature of metastatic disease. These results also provide the basis for clinically translatable noninvasive imaging markers for predicting metastatic risk in prostate cancer.

Liposomal gemcitabine (GemLip)-efficient drug against hormone-refractory Du145 and PC-3 prostate cancer xenografts

BACKGROUND

Gemcitabine (Gemc) is an efficient chemotherapeutic drug in various cancer types (e.g., pancreas) but has only limited effects on hormone-refractory prostate cancer (HRPCa). Since HRPCa cells are highly sensitive to even low doses of Gemc in vitro, the lack of clinical effects might be due to rapid degradation of Gemc by deaminases combined with impaired accumulation in tumor tissue and PCa cells. Liposomal formulation (GemLip) is expected to protect the entrapped cytotoxic substance from enzymatic degradation and furthermore augment its accumulation within tumor tissues due to an enhanced permeability of the tumor vessels.

METHODS

Anti-tumoral and anti-metastatic activity of GemLip and Gemc were investigated in two luciferase-expressing, human hormone-refractory PC-3 and Du145 HRPCa xenograft models in immunodeficient mice. Tumor growth was monitored by in vivo luminescence imaging (orthotopic) or callipering (subcutaneous). Anti-metastatic effects of treatment were determined by in vitro luciferase assay of the tissues.

RESULTS

Tumor growth of subcutaneous Du145 xenografts was significantly inhibited only by GemLip (8 mg/kg: P = 0.014 and 6 mg/kg: P = 0.011) but not by conventional Gemc (360 mg/kg). In contrast, growth of orthotopic PC-3 xenografts was significantly inhibited by both, GemLip (P = 0.041) and Gemc (P = 0.002). The drugs furthermore strongly reduced spleen and liver metastases in this model.

CONCLUSIONS

As shown by the very low efficient concentration of GemLip, liposomal entrapment of Gemc greatly enhances its activity. GemLip has, even at very low doses, a significant anti-tumoral and anti-metastatic therapeutic effect in HRPCa xenografts in vivo and was beneficial even when the conventional Gemc failed.

Targeting of pericytes diminishes neovascularization and lymphangiogenesis in prostate cancer

BACKGROUND

The walls of capillaries in prostate cancer are composed of endothelial cells, and pericytes. NG2 is a transmembrane proteoglycan on nascent pericytes with a functional role in neovascularization.

METHODS

The anti-angiogenic effect of hydron pellets containing NG2 neutralizing antibody was quantified in intracorneal PC-3 and LNCaP xenografts. TRAMP and TRAMP-C1 tumors grafted in NG2 knockout mice represented intrinsic pericyte targeting. TRAMP and TRAMP-C1 grafts were analyzed with confocal microscope for microvascular density (MVD) and lymphatic vascular density (LVD).

RESULTS

NG2 neutralizing antibody decreased corneal neovascularization in PC3 (P<0.0001), and LNCaP (P=0.0079) xenografts. Mean MVD in TRAMP and TRAMP-C1 tumors in NG2 knockout mice were 71% (P=0.0006) and 63% (P=0.0011) lower than wild type controls, respectively. Mean LVD in TRAMP and TRAMP-C1 tumors in NG2 knockout mice were 73% (P=0.0003) and 84% (P<0.0001) lower than wild type controls, respectively.

CONCLUSIONS

Targeting of pericyte-NG2 decreases neovascularization and lymphangiogenesis in prostate cancer significantly.

Practices and Pitfalls of Mouse Cancer Models in Drug Discovery

Mouse models of cancer are critical tools for elucidating mechanisms of cancer development, as well as for assessment of putative cancer therapies. However, there are ongoing concerns about the value of mouse cancer models for predicting therapeutic efficacy in humans. This chapter reviews the most commonly used transplanted tumor models, including subcutaneous and orthotopic tumors in mice. It also reviews commonly utilized in vivo study endpoints. Even small improvements in predictive value achieved through careful selection of models and endpoints have the potential to have large impacts on productivity and overall drug development costs.

Comparison of two in vivo models for prostate cancer: orthotopic and intratesticular inoculation of LNCaP or PC-3 cells

BACKGROUND

The critical events in the clinical course of prostate cancer are the occurrence of metastasis and the induction of the hormone-refractory status of the disease. In order to investigate the factors responsible for these events, we need appropriate in vivo models.

MATERIALS AND METHODS

Orthotopic and intratesticular models were created by the injection of LNCaP cells or PC-3 cells into the prostate or testis of severe combined immunodeficient mice.

RESULTS

LNCaP cells in the intratesticular model showed a higher incidence of tumor formation and lymph node metastasis when compared with those in the orthotopic model, while PC-3 cells were highly tumorigenic and metastastic in both models. A high concentration of androgens might play a role in tumor aggressiveness of LNCaP cells, given that enhanced mRNA expressions of integrin alphaV and vascular endothelial growth factor was induced by dehydrotestosterone administration in vitro. The high expression of metastasis-related genes, including the urokinase plasminogen activator system, metalloproteinases and vascular endothelial growth factor-C, might be attributed to the high metastatic potential in both models. Interestingly, testicular xenografts of LNCaP cells were able to survive on the subcutis back of castrated male mice as well female mice.

CONCLUSIONS

Intratesticular models of prostate cancer appear to be suitable for studying the mechanisms of metastasis and for evaluating various treatment strategies.

Effect of Tumor Host Microenvironment on Photodynamic Therapy in a Rat Prostate Tumor Model

Purpose: Tumor host microenvironment plays an important role in tumor growth, metastasis, and response to cancer therapy. In this study, the influence of tumor host environment on tumor pathophysiology, photosensitizer distribution, and photodynamic therapy (PDT) treatment effect was examined in the metastatic at lymph node and lung (MatLyLu) rat prostate tumor.

Experimental Design: MatLyLu tumors implanted in different host environment [i.e., orthotopically (in the prostate) or s.c.] were compared for difference in vessel density, average vessel size, vascular permeability, tumor vascular endothelial growth factor production, and tumor oxygenation. Uptake of photosensitizer verteporfin in tumors in both sites was determined by fluorescence microscopy. To compare tumor response to PDT, both orthotopic and s.c. MatLyLu tumors were given the same doses of verteporfin and laser light treatment, and PDT-induced tumor necrotic area was measured histologically.

Results: Orthotopic MatLyLu tumors were found to grow faster, have higher vessel density and more permeable vasculature, have higher vascular endothelial growth factor protein levels, and have lower tumor hypoxic fraction than the s.c. tumors. Uptake of photosensitizer verteporfin in the orthotopic tumor was higher than in the s.c. tumors at 15 minutes after injection (1 mg/kg, i.v.), and became similar at 3 hours after injection. For the vascular targeting PDT treatment (0.25 mg/kg verteporfin, 50 J/cm2 at 50 mW/cm2, 15 minutes drug-light interval), there was no significant difference in PDT-induced tumor necrotic area between the orthotopic and s.c. tumors, with 85% to 90% necrosis in both types of tumors. However, tumor necrosis induced by the cellular targeting PDT (1 mg/kg verteporfin, 50 J/cm2 at 50 mW/cm2, 3 hours drug-light interval) was significantly different in the orthotopic (64%) versus the s.c. (29%) tumors.

Conclusions: Tumor host environment can significantly affect photosensitizer verteporfin distribution and PDT treatment effect. Verteporfin-PDT regimen targeting tumor cells is more sensitive to such influence than the vascular targeting PDT. Our study showed the importance of tumor host environment in determining tumor physiologic properties and tumor response to PDT. To obtain clinically relevant information, orthotopic tumor model should be used in the experimental studies.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

A Nod Scid mouse model to study human prostate cancer

Prostate cancer is the second cause of cancer mortality in men in Western countries. To study new therapeutic approaches such as gene therapy, animal models of human prostate cancer with metastatic behavior are mandatory. We used the Nod Scid mouse strain to develop an orthotopic animal model. Two androgen-independent cell lines (PC-3 and DU 145) were used. Local tumor growth and metastases were analyzed. The tumor take rates were close to those reported in the literature. However, a high frequency of various metastatic sites has been observed (liver, lung, spleen, adrenal, kidney, lymph node, and diaphragm). It can be concluded that the Nod Scid mouse is a relevant preclinical animal model to study human prostate cancer. Metastatic sites seem more numerous in comparison to other orthotopic mice models described.

Expression profiles of voltage-gated Na(+) channel alpha-subunit genes in rat and human prostate cancer cell lines

BACKGROUND

Voltage-gated Na(+) channel (VGSC) activity has been implicated in prostate cancer (PC) metastasis. Although VGSCs can occur as multiple-subunit assemblies, the alpha-subunits (VGSCalphas) alone can encode functional channels. The VGSCalpha gene(s) responsible for the functional VGSCalpha expression in strongly metastatic PC cell lines is not known.

METHODS

Two reverse transcription-PCR (RT-PCR) methods, degenerate primer screening and a novel semi quantitative PCR (SQT-PCR) technique, were used. These methods enabled a detailed qualitative and quantitative investigation of VGSCalpha mRNA expression in rat (MAT-LyLu/AT-2) and human (PC-3/LNCaP) PC cells of markedly different metastatic potential.

RESULTS

Expression of eight different VGSCalpha genes (SCN1A-4A, SCN7A-9A, and SCN11A) was determined in the PC cell lines. Most were expressed as multiple splice variants. SQT-PCR results were consistent with a basal level of VGSCalpha mRNA expression occurring in weakly metastatic (AT-2/LNCaP) cells, and this being greatly elevated in cells of stronger metastatic potential (MAT-LyLu/PC-3), primarily due to the elevated expression of the SCN9A gene (also termed PN1/hNe-Na).

CONCLUSIONS

(1) Several VGSCalpha genes and their splice variants are expressed similarly in both rat and human PC cell lines. (2) Expression levels are much higher in the strongly metastatic (MAT-LyLu/PC-3) cells. (3) Levels of SCN9A mRNA specifically are predominant in MAT-LyLu and PC-3 cells; thus, SCN9A is highly likely to be the main source of the functional VGSC detected.

Transrectal ultrasound for monitoring murine orthotopic prostate tumor

BACKGROUND

The mouse orthotopic prostate tumor model has been recognized as an ideal preclinical animal model simulating the anatomical and biological milieu of the prostate. In comparison with the subcutaneous tumor model, the only disadvantage of this model is the difficulty of chronological tumor growth monitoring. We have applied recent endoluminal ultrasound technology, transrectal ultrasonography (TRUS), to the monitoring of mouse orthotopic prostate tumors.

METHODS

A 6 Fr. 20 MHz catheter-based radial scan probe was used and TRUS was performed without any prior preparation including anesthesia. Orthotopic tumors were initiated by inoculation of 5000 RM-9 cells into the dorsal prostate of 12-week-old C57BL/6 male mice. The tumor growth was monitored by TRUS from day 3 to day 21. In addition, TRUS was performed to detect tumor growth suppression after intraperitoneal administration of cis-diamminedichloroplatinum (CDDP).

RESULTS

By ultrasound, tumors became detectable 7 days after tumor cell inoculation. TRUS images were clear and parallel to actual tumor growth. The tumor volume (X) calculated by TRUS correlated significantly with the actual tumor weight (Y) measured at autopsy; Y = 101.653 + 1.174X (R = 0.930, P < 0.001). Similarly, tumor growth suppression induced by CDDP was clearly detected by TRUS with reasonable accuracy.

CONCLUSIONS

A high resolution TRUS allows simple and reliable monitoring of in situ tumor growth and growth suppression, making the mouse orthotopic prostate tumor model more efficient.

Vascular differences detected by MRI for metastatic versus nonmetastatic breast and prostate cancer xenografts

Several studies have linked vascular density, identified in histologic sections, to "metastatic risk." Functional information of the vasculature, not readily available from histologic sections, can be obtained with contrast-enhanced MRI to exploit for therapy or metastasis prevention. Our aims were to determine if human breast and prostate cancer xenografts preselected for differences in invasive and metastatic characteristics established correspondingly different vascular volume and permeability, quantified here with noninvasive MRI of the intravascular contrast agent albumin-GdDTPA. Tumor vascular volume and permeability of human breast and prostate cancer xenografts were characterized using MRI. Parallel studies confirmed the invasive behavior of these cell lines. Vascular endothelial growth factor (VEGF) expression in the cell lines was measured using ELISA and Western blots. Metastasis to the lungs was evaluated with spontaneous as well as experimental assay. Metastatic tumors formed vasculature with significantly higher permeability or vascular volume (P<.05, two-sided unpaired t test). The permeability profile matched VEGF expression. Within tumors, regions of high vascular volume usually exhibited low permeability whereas regions of low vascular volume exhibited high permeability. We observed that although invasion was necessary, without adequate vascularization it was not sufficient for metastasis to occur.

Establishment and characterization of the growth and pulmonary metastasis of a highly lung metastasizing cell line from canine osteosarcoma in nude mice

Highly lung metastasizing model of canine osteosarcoma in nude mice was established from five subcutaneous implantation cycles of lung tumor deposits. The selection of cells with increased metastatic properties from the parent POS canine osteosarcoma cell line recovered medium sized and polygonal Highly Metastasizing POS cells (HMPOS). The doubling time of HMPOS and POS in culture averaged 30 +/- 1.2 hr and 32 +/- 1.3 hr respectively, and their cell growth patterns in vitro were comparable to their in vivo growth patterns. HMPOS cells produced more tumor deposits (> 20 nodules, > 1 -mm in diameter) of various sizes with replacement of lung tissues at 12 weeks after implantation. POS cells produced fewer and smaller lung deposits (< 10 nodules, 1-mm in diameter). Tumor size and number of metastatic tumor deposits showed a regular association. HMPOS cells developed an osteoblastic type of cellular differentiation subcutaneously and in the lungs. HMPOS micrometastasis along the alveolar walls and blood vessels at 4 weeks averaged 6-7 small tumor locus. Each micrometastatic locus contained an average of 5-7 tumor cells, and developed a pleomorphic osteoblastic type of cellular differentiation. An average of 4 macrometastatic nodules could be seen at 6 weeks, composed of an average of 23 tumor cells, 10 nodules at 8 weeks, 12 nodules at 10 weeks and 20 nodules at 12 weeks. These model provides an opportunity for the evaluation of new treatments against canine lung metastatic osteosarcoma in a nude mice model.

Role of alphaII(b)beta3 integrin in prostate cancer metastasis

BACKGROUND

Integrins participate in cell-cell and cell-matrix interactions. In this study we determined whether alphaII(b)beta3 integrin is involved in metastasis of human prostate adenocarcinoma cells.

METHODS

Prostate adenocarcinoma PC-3 and DU-145 cell lines express alphaII(b)beta3. Northern blotting, 5'-RACE, and immunofluorescent localization confirmed expression of alphaIIb integrin in prostate adenocarcinoma cells. We used orthotopic/ectopic site of implantation and lung colonization assays in SCID mice to determine whether alphaII(b)beta3 participates in metastatasis of tumor cells.

RESULTS

Immunofluorescent localization of alphaIIb integrin in fibronectin-adherent DU-145 and PC-3 cells is remarkably different. In DU-145 cells the integrin localizes to focal contact sites, whereas it is predominantly intracellular in PC-3 cells. Both tumor cell lines are tumorigenic when implanted subcutaneously or intraprostatically in SCID mice, but only DU-145 cells injected intraprostatically metastasize. Flow cytometry with a mAb directed to alphaII(b)beta3 revealed higher expression of alphaII(b)beta3 in DU-145 tumor cell suspensions isolated from the prostate when compared to DU-145 tumor cells from the subcutis. Function-blocking mAbs to alphaII(b)beta3 inhibit lung colonization of tail vein-injected DU-145 cells.

CONCLUSIONS

Altogether, the data suggest that alphaII(b)beta3 integrin participates in the metastatic progression of prostatic adenocarcinoma.

Surgical orthotopic implantation allows high lung and lymph node metastatic expression of human prostate carcinoma cell line PC-3 in nude mice

BACKGROUND

Prostate cancer is the second leading cause of male death in the United States. When diagnosed, nearly half the cases have metastatic lesions. An animal model of human prostate cancer demonstrating spontaneous metastasis from the orthotopic site after tumor implantation should be of great help for us to understand the disease and to formulate treatment strategy. We report here a high metastatic model of human prostate cancer PC-3.

METHODS

We developed microsurgical techniques, termed surgical orthotopic implantation (SOI), to implant histologically intact tumor tissues orthotopically in immunodeficient mice. In this study intact tissue of the human prostate cancer cell line PC-3, harvested from a subcutaneous tumor in a nude mouse, was implanted to the ventral lateral lobes of the prostate gland in a series of nude mice. Mice were sacrificed when found moribund, and autopsy and histology were performed subsequently.

RESULTS

A high frequency of lymph node and lung metastasis was noted upon histological examination. The extensive and widespread lung metastasis following orthotopic implantation of PC-3 is, to the best of our knowledge, the first report in the literature.

CONCLUSIONS

In contrast to orthotopic injection of cell suspensions, no multiple metastatic cell selection was necessary after SOI for significant expression of the metastatic potential of PC-3. We conclude that the stromal tissue architecture maintained in the implanted tumor played a critical role in tumor growth and progression.

Human prostate tumor angiogenesis in nude mice: metalloprotease and plasminogen activator activities during tumor growth and neovascularization of subcutaneously injected matrigel impregnated with human prostate tumor cells

BACKGROUND

A critical aspect for growth of solid tumors is the development of a blood supply. Our objective was to establish a model for the study of angiogenesis of human prostate tumors by examining the growth of microvessels into Matrigel containing human prostate tumor cells implanted subcutaneously in nude mice.

METHODS

Human prostate tumor cell lines PC-3 and LNCaP were injected in Matrigel under the abdominal skin of nude mice and were harvested at 4, 8, and 14 days post-injection. The growth of tumor cells and blood vessels was examined histologically and by immunohistochemical localization of von Willibrand Factor VIII (vWF). Since plasminogen activators and matrix metalloproteases are associated with angiogenesis, the activities and molecular forms of these proteases were determined in Matrigel control and Matrigel-tumor cell subcutaneous implants.

RESULTS

Blood vessel formation in the Matrigel implants containing LNCaP and PC-3 cells was demonstrable at 8 days post-injection. However, the pattern of blood vessel formation by the two tumor cell lines was different; PC-3 tumors showed a more invasive phenotype and smaller diameter blood vessels, whereas LNCaP tumors grew as large cellular spheroids surrounded by large, dilated blood vessels. Many blood vessels of PC-3 tumors expressed vWF by day 14 of growth, whereas most blood vessels in LNCaP tumors were immunohistochemically negative for this antigen. Mouse skin blood vessels in the same PC-3 and LNCaP tumor histological sections were positive for vWF. Matrigel contained both plasminogen activator and metalloprotease activities. The plasminogen activator activity in Matrigel control implants was totally inhibited by 4 days post-injection, indicating the presence of an inhibitor provided by the host mouse. LNCaP tumor cells injected did not have appreciable plasminogen activator activity, nor did LNCaP tumors develop plasminogen activator activity with tumor growth post-injection. PC-3 cells did have plasminogen activator activities, which were partially negated after subcutaneous injection (4 days), but then increased again by 8 days post-injection. This increase in plasminogen activator activity was due to urokinase (about 54 kDa) produced by the tumor and not by the mouse host (mouse urine urokinase about 44 kDa). Matrigel alone demonstrated gelatinase B (about 95 kDa) activity in zymograms, and gained considerable gelatinase A (about 70 and 74 kDa) activity after subcutaneous implantation. No metalloprotease activity from the tumor cells could be distinguished over that contributed by the mouse host cells in the Matrigel. Matrigel also contains caseinolytic activities of approximately 56, 80, 85, and 89 kDa. After subcutaneous injection of Matrigel, the 89 kDa form increases considerably in activity and the others are diminished. This pattern is also observed in LNCaP and PC-3 tumors post-injection, except the PC-3 tumors demonstrate increased 56 kDa activity.

CONCLUSION

The subcutaneous growth of LNCaP and PC-3 prostate tumor cells in Matrigel in nude mice can be used to study tumor-induced angiogenesis. However, the organization of LNCaP and PC-3 tumor growth and the pattern of microvessels associated with each tumor are different in this system, implying that each tumor has unique influences on the pattern of microvessel development. The mode of action by which this is brought about is not known, but may be due to specific factors produced/ released by the tumor cells.