Development of a brain metastatic canine prostate cancer cell line

Alterations in Tumor Aggression Following Androgen Receptor Signaling Restoration in Canine Prostate Cancer Cell Lines

In prostate cancer (PCa), androgens upregulate tumorigenesis, whereas in benign tissue, the revival of androgen receptor (AR) signaling suppresses aggressive behaviors, suggesting therapeutic potential. Dogs, natural PCa models, often lack AR in PCa. We restored AR in dog PCa to investigate resultant characteristics. Three AR-null canine PCa lines (1508, Leo, 1258) were transfected with canine wild-type AR and treated with dihydrotestosterone (DHT). In 1508, AR restoration decreased clonogenicity (p = 0.03), viability (p = 0.004), migration (p = 0.03), invasion (p = 0.01), and increased expression of the tumor suppressor NKX3.1, an AR transcriptional target (p = 0.001). In Leo, AR decreased clonogenicity (p = 0.04) and the expression of another AR transcriptional target FOLH1 (p < 0.001) and increased the expression of NKX3.1 (p = 0.01). In 1258, AR increased migration (p = 0.006) and invasion (p = 0.03). Epithelial-mesenchymal transition (EMT) marker (Vimentin, N-cadherin, SNAIL1) expression increased with AR restoration in Leo and 1258 but not 1508; siRNA vimentin knockdown abrogated AR-induced 1258 migration only. Overall, 1508 showed AR-mediated tumor suppression; AR affected proliferation in Leo but not migration or invasion; and EMT and AR regulated migration and invasion in 1258 but not proliferation. This study highlights the heterogeneous nature of PCa in dogs and cell line-specific effects of AR abrogation on aggressive behaviors.

Advances in organoid technology for veterinary disease modeling

Organoids are in vitro organ-like structures that faithfully recapitulate many characteristics of a specific organ. During the past decades, major progress has been accomplished in establishing three-dimensional (3D) culture systems toward stem cell-derived organoids. As a significant technological breakthrough, these amazing 3D organoid constructs bridge the conventional 2D in vitro models and in vivo animal models and provide an unprecedented opportunity to investigate the complexities of veterinary diseases ranging from their pathogenesis to the prevention, therapy, or even future organ replacement strategies. In this review, we briefly discuss several definitions used in organoid research and highlight the currently known achievements in modeling veterinary diseases, including infectious and inflammatory diseases, cancers, and metabolic diseases. The applications of organoid technology in veterinary disease modeling are still in their infancy stage but the future is promising.

mTOR pathway as a potential therapeutic target for cancer stem cells in canine mammary carcinoma

Mammary adenocarcinoma, the most common cancer in female dogs, often exhibits the lymph node and lung metastases and has a higher mortality rate. However, mammary adenocarcinoma has no established treatment, except early surgical excision. Canine mammary carcinoma has many common features with human mammary carcinoma, including clinical characteristics, heterogeneity, and genetic aberrations, making it an excellent spontaneous tumor model for human breast cancer. Diverse cancers comprised heterogeneous cell populations originating from cancer stem cells (CSCs) with self-renewal ability. Therefore, in addition to conventional therapy, therapeutic strategies targeting CSCs are essential for cancer eradication. The present study aimed to extract inhibitors of canine mammary CSCs that suppress their self-renewal ability. Sphere-formation assay, which evaluates self-renewal ability, was performed for the canine mammary cancer cell lines CTBp and CNMp. The spheres formed in this assay were used in inhibitor library screening, which identified various signaling pathways such as proteosome, stress inducer, and mammalian target of rapamycin (mTOR). The present study focused on the mTOR signaling pathway. Western blotting showed higher levels of phosphorylated mTOR in sphere-forming CTBp and CNMp cells than in adherent cells. Drug sensitivity examination using the mTOR inhibitors everolimus and temsirolimus revealed dose-dependent reductions in viability among both sphere-forming cells and adherent cells. Expression of phosphorylated mTOR in adherent and sphere-forming cells decreased by everolimus and temsirolimus treatment. In mice transplanted with CTBp-derived spheres, everolimus treatment significantly decreased tumor volume compared to control. These results reveal that the mTOR signaling pathway may be a potential to be a therapeutic target in both cancer cells and CSCs. Novel therapeutic strategies for canine mammary carcinoma are expected to benefit to human breast carcinoma as well.

Investigating PSMA differential expression in canine uroepithelial carcinomas to aid disease-based stratification and guide therapeutic selection

BACKGROUND

In male dogs, uroepithelial cancers include invasive urothelial carcinoma (iUC) and prostate carcinoma (PCA). The inability to distinguish iUC involving the prostate from PCA results in indiscriminate clinical management strategies that could be suboptimal as first-line chemotherapy for iUC (cisplatin) and PCA (docetaxel) differ in people. Prostate specific membrane antigen (PSMA) is a transmembrane protein, and its overexpression has been identified in human prostate carcinoma and neovasculature associated with solid tumor growth. This study investigates whether differential PSMA expression exists between presumptive canine iUC and PCA among cell lines and archived patient samples, which might allow for improved accuracy in disease-based stratification and optimal chemotherapy selection. Additionally, in vitro sensitivities of reported canine iUC and PCA cell lines to uroepithelial directed chemotherapeutic agents were characterized.

RESULTS

Normalized PSMA gene and protein expressions were not significantly different between 5 iUC and 4 PCA cell lines. PSMA protein expression was uniformly observed in uroepithelial cancers regardless of anatomic origin from archived patient samples, further confirming that PSMA cannot differentiate iUC from PCA. In vitro sensitivity of cell lines to uroepithelial directed chemotherapeutics revealed that vinblastine exerted the broadest cytotoxic activity.

CONCLUSIONS

Differential expression of PSMA was not identified between canine iUC and PCA cell lines or archived patient samples, and PSMA alone cannot be used for disease stratification. Nonetheless given its conserved overexpression, PSMA may be a targetable surface marker for both canine iUC and PCA. Lastly, in uroepithelial carcinomas, vinblastine might exert the broadest anticancer activity regardless of cellular origin.

RNA-seq of nine canine prostate cancer cell lines reveals diverse therapeutic target signatures

BACKGROUND

Canine prostate adenocarcinoma (PAC) and transitional cell carcinoma (TCC) are typically characterized by metastasis and chemoresistance. Cell lines are important model systems for developing new therapeutic strategies. However, as they adapt to culturing conditions and undergo clonal selection, they can diverge from the tissue from which they were originally derived. Therefore, a comprehensive characterization of cell lines and their original tissues is paramount.

METHODS

This study compared the transcriptomes of nine canine cell lines derived from PAC, PAC metastasis and TCC to their respective original primary tumor or metastasis tissues. Special interests were laid on cell culture-related differences, epithelial to mesenchymal transition (EMT), the prostate and bladder cancer pathways, therapeutic targets in the PI3K-AKT signaling pathway and genes correlated with chemoresistance towards doxorubicin and carboplatin.

RESULTS

Independent analyses for PAC, PAC metastasis and TCC revealed 1743, 3941 and 463 genes, respectively, differentially expressed in the cell lines relative to their original tissues (DEGs). While genes associated with tumor microenvironment were mostly downregulated in the cell lines, patient-specific EMT features were conserved. Furthermore, examination of the prostate and bladder cancer pathways revealed extensive concordance between cell lines and tissues. Interestingly, all cell lines preserved downstream PI3K-AKT signaling, but each featured a unique therapeutic target signature. Additionally, resistance towards doxorubicin was associated with G2/M cell cycle transition and cell membrane biosynthesis, while carboplatin resistance correlated with histone, m- and tRNA processing.

CONCLUSION

Comparative whole-transcriptome profiling of cell lines and their original tissues identifies models with conserved therapeutic target expression. Moreover, it is useful for selecting suitable negative controls, i.e., cell lines lacking therapeutic target expression, increasing the transfer efficiency from in vitro to primary neoplasias for new therapeutic protocols. In summary, the dataset presented here constitutes a rich resource for canine prostate and bladder cancer research.

Comparative pathology of dog and human prostate cancer

Though relatively rare in dogs, prostate cancer (PCa) is the most common non-cutaneous cancer in men. Human and canine prostate glands share many functional, anatomical and physiological features. Due to these similarities, canine PCa has been proposed as a model for PCa in men. PCa is typically androgen-dependent at diagnosis in men and for this reason, androgen deprivation therapies (ADT) are important treatments for advanced PCa in men. In contrast, there is some evidence that PCa is diagnosed more commonly in castrate dogs, at which point, limited therapeutic options are available. In men, a major limitation of current ADT is that progression to a lethal and incurable form of PCa, termed castrate-resistant prostate cancer (CRPC), is common. There is, therefore, an urgent need for a better understanding of the mechanism of PCa initiation and progression to CRPC to enable the development of novel therapeutic approaches. This review focuses on the functional, physiological, endocrine and histopathological similarities and differences in the prostate gland of these species. In particular, we focus on common physiological roles for androgen signalling in the prostate of men and dogs, we review the short- and longer-term effects of castration on PCa incidence and progression in the dog and relate how this knowledge may be relevant to understanding the mechanisms of CRPC in men.

An Overview of Current Alternative Models for Use in the Context of Prostate Cancer Research

Prostate cancer is one of the most commonly diagnosed cancers worldwide, particularly in elderly populations. To mitigate the expected increase in prostate cancer-related morbidity and mortality as a result of an expanding aged population, safer and more effective therapeutics are required. To this end, plenty of research is focusing on the mechanisms underlying cancer initiation and development, the metastatic process and on the discovery of new therapies. While animal models are used (mainly rats and mice) for the study of prostate cancer, alternative models and methods are increasingly being considered to replace, or at least reduce, the number of animals used in this particular field of research. In this review, we cover some of the alternative models that are currently available for use in the study of prostate cancer, including: mathematical models; 2-D and 3-D cell cultures; microfluidic devices; the chicken egg chorioallantoic membrane-based model; and zebrafish embryo-based models. The main advantages and limitations, as well as some examples of applications, are given for each type of model. According to our analysis, immortalised cell lines are still the most commonly used models in the field of prostate cancer research. However, the use of alternative models for prostate cancer research will likely become more prevalent in the coming years partly because of the increasing societal pressure to reduce the numbers of laboratory animals. In this context, the development and dissemination of effective non-animal alternative models assumes particular relevance and will be instrumental in leveraging their success. Taking these perspectives into account, we believe that technological advances will lead to more effective cell culture systems, namely 3-D cultures or organ-on-a-chip devices, which can be used to replace animal-based models in prostate cancer research.

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.

Establishment and characterization of stable red, far-red (fR) and near infra-red (NIR) transfected canine prostate cancer cell lines

Background

Canine prostate cancer represents a unique model for human prostate cancer. In vitro systems offer various possibilities but Xenograft in vivo imaging allows studying complex tasks as tumor progression and drug intervention longitudinal. Herein, we established three canine prostate carcinoma cell lines stably expressing fluorescent proteins allowing deep tissue in vivo imaging.

Methods

Three canine prostate carcinoma (cPC) cell lines were stably transfected with fluorescent proteins in red, far-red and near infra-red spectrum, followed by G418 selection. Fluorescent protein expression was demonstrated by microscopy, flow cytometry and a NightOWL LB 983 in vivo imaging system. Cellular and molecular characteristics of the generated cell lines were compared to the parental cell line CT1258. Cell proliferation, metabolic activity and sphere formation capacity were analyzed. Stem cell marker expression was examined by qPCR and genomic copy number variation by genomic DNA whole genome sequencing.

Results

Three stably fluorescent protein transfected cPC cell lines were established and characterized. Compared to the parental cell line, no significant difference in cell proliferation and metabolic activity were detected. Genomic copy number variation analyses and stem cell marker gene expression revealed in general no significant changes. However, the generated cell line CT1258-mKate2C showed uniquely no distal CFA16 deletion and an elevated metabolic activity. The introduced fluorescencent proteins allowed highly sensitive detection in an in vivo imaging system starting at cell numbers of 0.156 × 10⁶. Furthermore, we demonstrated a similar sphere formation capacity in the fluorescent cell lines. Interestingly, the clone selected CT1258-mKate2C, showed increased sphere formation ability.

Discussion

Starting from a well characterized cPC cell line three novel fluorescent cell lines were established showing high cellular and molecular similarity to the parental cell line. The introduction of the fluorescent proteins did not alter the established cell lines significantly. The red fluorescence allows deep tissue imaging, which conventional GFP labeling is not able to realize.

Conclusion

As no significant differences were detected between the established cell lines and the very well characterized parental CT1258 the new fluorescent cell lines allow deep tissue in vivo imaging for perspective in vivo evaluation of novel therapeutic regimens.

Characterization of six canine prostate adenocarcinoma and three transitional cell carcinoma cell lines derived from primary tumor tissues as well as metastasis

Canine prostate adenocarcinoma (PAC) and transitional cell carcinoma (TCC) of prostate and urinary bladder are highly invasive and metastatic tumors of closely neighbored organs. Cell lines are valuable tools to investigate tumor mechanisms and therapeutic approaches in vitro. PAC in dogs is infrequent, difficult to differentiate from TCC and usually characterized by poor prognosis, enhancing the value of the few available cell lines. However, as cell lines adapt to culturing conditions, a thorough characterization, ideally compared to original tissue, is indispensable. Herein, six canine PAC cell lines and three TCC cell lines were profiled by immunophenotype in comparison to respective original tumor tissues. Three of the six PAC cell lines were derived from primary tumor and metastases of the same patient. Further, two of the three TCC cell lines were derived from TCCs invading into or originating from the prostate. Cell biologic parameters as doubling times and chemoresistances to commonly used drugs in cancer treatment (doxorubicin, carboplatin and meloxicam) were assessed. All cell lines were immunohistochemically close to the respective original tissue. Compared to primary tumor cell lines, metastasis-derived cell lines were more chemoresistant to doxorubicin, but equally susceptive to carboplatin treatment. Two cell lines were multiresistant. COX-2 enzyme activity was demonstrated in all cell lines. However, meloxicam inhibited prostaglandin E2 production in only seven of nine cell lines and did neither influence metabolic activity, nor proliferation. The characterized nine cell lines represent excellent tools to investigate PAC as well as TCC in prostate and urinary bladder of the dog. Furthermore, the profiled paired cell lines from PAC primary tumor and metastasis provide the unique opportunity to investigate metastasis-associated changes PAC cells undergo in tumor progression. The combination of nine differently chemoresistant PAC and TCC cell lines resembles the heterogeneity of canine lower urinary tract cancer.

Malignant invasion of the central nervous system: the hidden face of a poorly understood outcome of prostate cancer

Malignancies of the central nervous system include primary brain tumors and brain metastases, the latter being the major cause of intracranial neoplasms in adults. Although prostate cancer (PCa) brain metastases are not the most common source, recent data show that the relevance of prostate cancer brain metastases (PCBM) cannot be neglected. In this review, we focus on the molecular repertory as well as on the phenotypical similarities between PCBM and primary PCa, such as the cellular evolution and the maintenance of androgen-receptor expression. Moreover, the simultaneous occurrence of PCBM with other PCa metastatic sites and the significance of the clinical heterogeneity of the disease are also discussed. In addition, a potential relationship between the heterogeneous behavior exhibited by PCBM and the co-occurrence of malignant cell clusters with distinct genetic profiles is also hypothesized, as well as the prominent role of astrocytes in the establishment of PCBM.

Canine REIC/Dkk-3 interacts with SGTA and restores androgen receptor signalling in androgen-independent prostate cancer cell lines

Background

The pathological condition of canine prostate cancer resembles that of human androgen-independent prostate cancer. Both canine and human androgen receptor (AR) signalling are inhibited by overexpression of the dimerized co-chaperone small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), which is considered to cause the development of androgen-independency. Reduced expression in immortalised cells (REIC/Dkk-3) interferes with SGTA dimerization and rescues AR signalling. This study aimed to assess the effects of REIC/Dkk-3 and SGTA interactions on AR signalling in the canine androgen-independent prostate cancer cell line CHP-1.

Results

Mammalian two-hybrid and Halo-tagged pull-down assays showed that canine REIC/Dkk-3 interacted with SGTA and interfered with SGTA dimerization. Additionally, reporter assays revealed that canine REIC/Dkk-3 restored AR signalling in both human and canine androgen-independent prostate cancer cells. Therefore, we confirmed the interaction between canine SGTA and REIC/Dkk-3, as well as their role in AR signalling.

Conclusions

Our results suggest that this interaction might contribute to the development of a novel strategy for androgen-independent prostate cancer treatment. Moreover, we established the canine androgen-independent prostate cancer model as a suitable animal model for the study of this type of treatment-refractory human cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1094-4) contains supplementary material, which is available to authorized users.

The canine prostate cancer cell line CHP-1 shows over-expression of the co-chaperone small glutamine-rich tetratricopeptide repeat-containing protein α

Although androgen therapy resistance and poor clinical outcomes are seen in most canine prostate cancer cases, there are only a few tools for analysing canine prostate cancer by using a cell biological approach. Therefore, to evaluate androgen-independent neoplastic cell growth, a new canine prostate cancer cell line (CHP-1) was established in this study. CHP-1 over-expressed the co-chaperone small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), which is over-expressed in human androgen-independent prostate cancer. The CHP-1 xenograft also showed SGTA over-expression. Although CHP-1 shows poor androgen receptor (AR) signalling upon dihydrotestosterone stimulation, forced expression of AR enabled evaluation of AR signalling. Taken together, these results suggest that CHP-1 will be a useful model for investigating the pathogenesis of androgen-dependent and androgen-independent canine prostate cancer.

Detection of BRAF Mutation in Urine DNA as a Molecular Diagnostic for Canine Urothelial and Prostatic Carcinoma

Urothelial carcinoma (UC) of the lower urinary tract and prostatic carcinoma (PC) are aggressive genitourinary cancers in dogs, characterized by invasion to surrounding tissues and high metastatic potential. Current diagnosis of canine UC and PC requires histopathological examination of a biopsy. Such specimens require specialized medical equipment and are invasive procedures, limiting the availability of diagnosis by histopathology for many canine patients. Access to a non-invasive means to confirm diagnosis is currently an unmet need. Recently, the canine BRAF V595E mutation was detected in ~80% of canine UCs and PCs. In this study, we developed a droplet digital PCR (ddPCR) assay for detection of the canine BRAF V595E mutation in canine urogenital tumors. The assay was evaluated in DNA samples prepared from biopsy specimens of UC (n = 48) and PC (n = 27), as well and non-neoplastic bladder epithelium (n = 38). In addition the assay was assessed for use with DNA isolated from free catch urine samples derived from canine patients with UC (n = 23), PC (n = 3), as well as from dogs with cystitis and healthy controls (n = 37). In all cases the sensitivity to detect the mutant allele was compared with conventional Sanger sequencing. ddPCR had superior sensitivity for detection of the V595E mutation: 75% of UC, 85% of PC, and 0% of control samples were mutation positive, respectively, and the V595E mutation was detected at a level as low as just 1 in 10,000 alleles (~0.01%). Furthermore, the ddPCR assay identified the mutation in free catch urine samples from 83% of canine UC and PC patients, demonstrating its utility as a non-invasive means of diagnosis. We have shown that ddPCR is a sensitive molecular technique with the potential to facilitate accurate and non-invasive means of canine UC and PC diagnosis.

Heptamethine carbocyanine dye-mediated near-infrared imaging of canine and human cancers through the HIF-1α/OATPs signaling axis

Near-infrared (NIR) fluorescence imaging agents are promising tools for noninvasive cancer imaging. This study explored the specific uptake and retention of a NIR heptamethine carbocyanine MHI-148 dye by canine cancer cells and tissues and human prostate cancer (PCa) specimens and also the dye uptake mechanisms. The accumulation of MHI-148 was detected specifically in canine cancer cells and tissues and freshly harvested human PCa tissues xenografted in mice by NIR fluorescence microscopy and whole-body NIR optical imaging. Specific dye uptake in canine spontaneous tumors was further confirmed by PET imaging. Higher hypoxia-inducible factor-1α (HIF-1α) and organic anion-transporting polypeptide (OATP) protein and mRNA expression was demonstrated by multiplex quantum dots labeling and qPCR in tumors over that of normal tissues. Treating cancer cells with HIF-1α stabilizers activated HIF-1α downstream target genes, induced OATP superfamily gene expression and enhanced cellular uptake and retention of NIR dyes. Moreover, silencing HIF-1α by siRNA significantly decreased OATP mRNA expression and blocked NIR dye uptake in cancer cells. Together, these results demonstrated the preferential uptake of NIR dyes by canine and human cancer cells and tissues via the HIF-1α/OATPs signaling axis, which provides insights into future application of these dyes for cancer detection and treatment.

Animal Models of Bone Metastasis

Bone is one of the most common sites of cancer metastasis in humans and is a significant source of morbidity and mortality. Bone metastases are considered incurable and result in pain, pathologic fracture, and decreased quality of life. Animal models of skeletal metastases are essential to improve the understanding of the molecular pathways of cancer metastasis and growth in bone and to develop new therapies to inhibit and prevent bone metastases. The ideal animal model should be clinically relevant, reproducible, and representative of human disease. Currently, an ideal model does not exist; however, understanding the strengths and weaknesses of the available models will lead to proper study design and successful cancer research. This review provides an overview of the current in vivo animal models used in the study of skeletal metastases or local tumor invasion into bone and focuses on mammary and prostate cancer, lymphoma, multiple myeloma, head and neck squamous cell carcinoma, and miscellaneous tumors that metastasize to bone.

Canine prostate cancer cell line (Probasco) produces osteoblastic metastases in vivo

BACKGROUND

In 2012, over 240,000 men were diagnosed with prostate cancer and over 28,000 died from the disease. Animal models of prostate cancer are vital to understanding its pathogenesis and developing therapeutics. Canine models in particular are useful due to their similarities to late-stage, castration-resistant human disease with osteoblastic bone metastases. This study established and characterized a novel canine prostate cancer cell line that will contribute to the understanding of prostate cancer pathogenesis.

METHODS

A novel cell line (Probasco) was derived from a mixed breed dog that had spontaneous prostate cancer. Cell proliferation and motility were analyzed in vitro. Tumor growth in vivo was studied by subcutaneous, intratibial, and intracardiac injection of Probasco cells into nude mice. Tumors were evaluated by bioluminescent imaging, Faxitron radiography, µCT, and histology. RT-PCR and genome-wide DNA copy number profiling were used to characterize the cell line.

RESULTS

The Probasco cells grew in vitro (over 75 passages) and were tumorigenic in nude mice. Probasco cells expressed high levels of BMP2, CDH1, MYOF, FOLH1, RUNX2, and SMAD5 modest CXCL12, SLUG, and BMP, and no PTHrP mRNA. Following intracardiac injection, Probasco cells metastasized primarily to the appendicular skeleton, and both intratibial and intracardiac injections produced osteoblastic tumors in bone. Comparative genomic hybridization demonstrated numerous DNA copy number aberrations throughout the genome, including large losses and gains in multiple chromosomes.

CONCLUSIONS

The Probasco prostate cancer cell line will be a valuable model to investigate the mechanisms of prostate cancer pathogenesis and osteoblastic bone metastases.

Biochemical characterization of prostate-specific membrane antigen from canine prostate carcinoma cells

BACKGROUND

Prostate-specific membrane antigen (PSMA) remains an important target for diagnostic and therapeutic application for human prostate cancer. Model cell lines have been recently developed to study canine prostate cancer but their PSMA expression and enzymatic activity have not been elucidated. The present study was focused on determining PSMA expression in these model canine cell lines and the use of fluorescent small-molecule enzyme inhibitors to detect canine PSMA expression by flow cytometry.

METHODS

Western blot and RT-PCR were used to determine the transcriptional and translational expression of PSMA on the canine cell lines Leo and Ace-1. An endpoint HPLC-based assay was used to monitor the enzymatic activity of canine PSMA and the potency of enzyme inhibitors. Flow cytometry was used to detect the PSMA expressed on Leo and Ace-1 cells using a fluorescently tagged PSMA enzyme inhibitor.

RESULTS

Canine PSMA expression on the Leo cell line was confirmed by Western blot and RT-PCR, the enzyme activity, and flow cytometry. Kinetic parameters Km and Vmax of PSMA enzymatic activity for the synthetic substrate (PABGγG) were determined to be 393 nM and 220 pmol min(-1)  mg protein(-1) , respectively. The inhibitor core 1 and fluorescent inhibitor 2 were found to be potent reversible inhibitors (IC50  = 13.2 and 1.6 nM, respectively) of PSMA expressed on the Leo cell line. Fluorescent labeling of Leo cells demonstrated that the fluorescent PSMA inhibitor 2 can be used for the detection of PSMA-positive canine prostate tumor cells. Expression of PSMA on Ace-1 was low and not detectable by flow cytometry.

CONCLUSIONS

The results described herein have demonstrated that PSMA is expressed on canine prostate tumor cells and exhibits similar enzymatic characteristics as human PSMA. The findings show that the small molecule enzyme inhibitors currently being studied for use in diagnosis and therapy of human prostate cancer can also be extended to include canine prostate cancer. Importantly, the findings demonstrate that the potential of the inhibitors for use in diagnosis and therapy can be evaluated in an immunocompetent animal model that naturally develops prostate cancer before use in humans.

A rat model of metastatic spinal cord compression using human prostate adenocarcinoma: histopathological and functional analysis

BACKGROUND CONTEXT

Cancer is a major global public health problem responsible for one in every four deaths in the United States. Prostate cancer alone accounts for 29% of all cancers in men and is the sixth leading cause of death in men. It is estimated that up to 30% of patients with cancer will develop metastatic disease, the spine being one of the most frequently affected sites in patients with prostate cancer.

PURPOSE

To study this condition in a preclinical setting, we have created a novel animal model of human metastatic prostate cancer to the spine and have characterized it histologically, functionally, and via bioluminescence imaging.

STUDY DESIGN

Translational science investigation of animal model of human prostate cancer in the spine.

METHODS

Luciferase-positive human prostate tumor cells PC3 (PC3-Luc) were injected in the flank of athymic male rats. PC3-Luc tumor samples were then implanted into the L5 vertebral body of male athymic rats (5 weeks old). Thirty-two rats were randomized into three surgical groups: experimental, control, and sham. Tumor growth was assessed qualitatively and noninvasively via bioluminescence emission, upon luciferin injection. To determine the functional impact of tumor growth in the spine, rats were evaluated for gait abnormalities during gait locomotion using video-assisted gait analysis. Rats were euthanized 22 days after tumor implantation, and spines were subjected to histopathological analyses.

RESULTS

Twenty days after tumor implantation, the tumor-implanted rats showed distinct signs of gait disturbances: dragging tail, right- or left-hind limb uncoordination, and absence of toe clearance during forward limb movement. At 20 days, all rats experienced tumor growth, evidenced by bioluminescent signal. Locomotion parameters negatively affected in tumor-implanted rats included stride length, velocity, and duration. At necropsy, all spines showed evidence of tumor growth, and the histological analysis found spinal cord compression and peritumoral osteoblastic reaction characteristic of bony prostate tumors. None of the rats in the sham or control groups demonstrated any evidence of bioluminescence signal or signs of gait disturbances.

CONCLUSIONS

In this project, we have developed a novel animal model of metastatic spine cancer using human prostate cancer cells. Tumor growth, evaluated via bioluminescence and corroborated by histopathological analyses, affected hind limb locomotion in ways that mimic motor deficits present in humans afflicted with metastatic spine disease. Our model represents a reliable method to evaluate the experimental therapeutic approaches of human tumors of the spine in animals. Gait locomotion and bioluminescence analyses can be used as surrogate noninvasive methods to evaluate tumor growth in this model.

Tumor microenvironment regulates metastasis and metastasis genes of mouse MMTV-PymT mammary cancer cells in vivo

Metastasis is the primary cause of death in breast cancer patients, yet there are challenges to modeling this process in vivo. The goal of this study was to analyze the effects of injection site on tumor growth and metastasis and gene expression of breast cancer cells in vivo using the MMTV-PymT breast cancer model (Met-1 cells). Met-1 cells were injected into 5 sites (subcutaneous, mammary fat pad, tail vein, intracardiac, and intratibial), and tumors and metastases were monitored using bioluminescent imaging and confirmed with gross necropsy and histopathology. Met-1 tumors were analyzed based on morphology and changes in gene expression in each tissue microenvironment. There were 6 permissible sites of Met-1 tumor growth (mammary gland, subcutis, lung, adrenal gland, ovary, bone). Met-1 cells grew faster in the subcutis compared to mammary fat pad tumors (highest Ki-67 index). Morphologic differences were evident in each tumor microenvironment. Finally, 7 genes were differentially expressed in the Met-1 tumors in the 6 sites of growth or metastasis. This investigation demonstrates that breast cancer progression and metastasis are regulated by not only the tumor cells but also the experimental model and unique molecular signals from the tumor microenvironment.

Brain metastases from prostate cancer: an emerging clinical problem with implications for the future therapeutic scenario

Brain metastases from prostate cancer (PC) seem to be more frequent than in the past, possibly because advances in the treatment of patients with castration-resistant PC have prolonged their survival. Furthermore, docetaxel (the drug of choice for the first-line treatment of castration-resistant PC) cannot cross the blood-brain barrier and control metastatic foci. However, this problem may be overcome by new active drugs such as cabazitaxel.

Longitudinal MRI contrast enhanced monitoring of early tumour development with manganese chloride (MnCl2) and superparamagnetic iron oxide nanoparticles (SPIOs) in a CT1258 based in vivo model of prostate cancer

Background

Cell lines represent a key tool in cancer research allowing the generation of neoplasias which resemble initial tumours in in-vivo animal models. The characterisation of early tumour development is of major interest in order to evaluate the efficacy of therapeutic agents. Magnetic resonance imaging (MRI) based in-vivo characterisation allows visualisation and characterisation of tumour development in early stages prior to manual palpation. Contrast agents for MRI such as superparamagnetic iron oxide nanoparticles (SPIOs) and manganese chloride (MnCl₂) represent powerful tools for the in-vivo characterisation of early stage tumours. In this experimental study, we labelled prostate cancer cells with MnCl₂ or SPIOs in vitro and used 1 T MRI for tracing labelled cells in-vitro and 7 T MRI for tracking in an in-vivo animal model.

Methods

Labelling of prostate cancer cells CT1258 was established in-vitro with MnCl₂ and SPIOs. In-vitro detection of labelled cells in an agar phantom was carried out through 1 T MRI while in-vivo detection was performed using 7 T MRI after subcutaneous (s.c.) injection of labelled cells into NOD-Scid mice (n = 20). The animals were scanned in regular intervals until euthanization. The respective tumour volumes were analysed and corresponding tumour masses were subjected to histologic examination.

Results

MnCl₂in-vitro labelling resulted in no significant metabolic effects on proliferation and cell vitality. In-vitro detection-limit accounted 10⁵ cells for MnCl₂ as well as for SPIOs labelling. In-vivo 7 T MRI scans allowed detection of 10³ and 10⁴ cells. In-vivo MnCl₂ labelled cells were detectable from days 4–16 while SPIO labelling allowed detection until 4 days after s.c. injection. MnCl₂ labelled cells were highly tumourigenic in NOD-Scid mice and the tumour volume development was characterised in a time dependent manner. The amount of injected cells correlated with tumour size development and disease progression. Histological analysis of the induced tumour masses demonstrated characteristic morphologies of prostate adenocarcinoma.

Conclusions

To the best of our knowledge, this is the first study reporting direct in-vitro MnCl₂ labelling and 7 T based in-vivo MRI tracing of cancer cells in a model of prostate cancer. MnCl₂ labelling was found to be suitable for in-vivo tracing allowing long detection periods. The labelled cells kept their highly tumourigenic potential in-vivo. Tumour volume development was visualised prior to manual palpation allowing tumour characterisation in early stages of the disease.

Refining the orthotopic dog prostate cancer (DPC)-1 model to better bridge the gap between rodents and men

BACKGROUND

Rodent models are often suboptimal for translational research on human prostate cancer (PCa). To better fill the gap with human, we refined the previously described orthotopic dog prostate cancer (DPC)-1 model.

METHODS

Cyclosporine (Cy) A was used for immune suppression at varying doses and time-periods prior and after orthotopic DPC-1 cell implantation in the dog prostate (n = 12). Follow up included digital rectal examination, ultrasound prostate imaging and biopsies of hypoechoic areas. At necropsy, the prostate, iliosacral lymph nodes (LN), lung nodules, and suspicious bone segments were collected for histopathology.

RESULTS

15 mg CyA/kg daily for 10 days was optimal for tumor take. Maintaining these conditions post-implantation resulted in a rapid tumor development within and beyond the prostate and in iliosacral LNs. To minimize tumor burden, 10 times less DPC-1 cells were implanted. A series of dogs was next followed for 3-4 months, under continuous immune suppression (n = 3) or with CyA interruption at 8.5 weeks (n = 2). In all instances, multifocal tumors were found within the prostate. Predominant patterns were micropapillary and cribriform. Metastases were present in iliosacral LNs and lungs. Moreover, pelvic bone metastases producing a mixed osteoblastic/osteolytic reaction were confirmed in two dogs, one per group. Lastly, the release of CyA 1-2 weeks post-implantation (n = 3) did not prevent tumor growth and spreading to LNs.

CONCLUSIONS

The continuing growth of DPC-1 tumors despite the release of CyA and, for the first time, spreading to bones renders this refined model closer to the spontaneous canine and hormone-refractory phase of human PCa.