A murine model for bone marrow metastasis established by an i.v. injection of C-1300 neuroblastoma in A/J mice

Roles of calcium signaling in cancer metastasis to bone

Bone metastasis is a frequent complication for cancers and an important reason for the mortality in cancer patients. After surviving in bone, cancer cells can cause severe pain, life-threatening hypercalcemia, pathologic fractures, spinal cord compression, and even death. However, the underlying mechanisms of bone metastasis were not clear. The role of calcium (Ca2+) in cancer cell proliferation, migration, and invasion has been well established. Interestingly, emerging evidence indicates that Ca2+ signaling played a key role in bone metastasis, for it not only promotes cancer progression but also mediates osteoclasts and osteoblasts differentiation. Therefore, Ca2+ signaling has emerged as a novel therapeutical target for cancer bone metastasis treatments. Here, the role of Ca2+ channels and Ca2+-binding proteins including calmodulin and Ca2+-sensing receptor in bone metastasis, and the perspective of anti-cancer bone metastasis therapeutics via targeting the Ca2+ signaling pathway are summarized.

The Role of Calmodulin in Tumor Cell Migration, Invasiveness, and Metastasis

Calmodulin (CaM) is the principal Ca²⁺ sensor protein in all eukaryotic cells, that upon binding to target proteins transduces signals encoded by global or subcellular-specific changes of Ca²⁺ concentration within the cell. The Ca²⁺/CaM complex as well as Ca²⁺-free CaM modulate the activity of a vast number of enzymes, channels, signaling, adaptor and structural proteins, and hence the functionality of implicated signaling pathways, which control multiple cellular functions. A basic and important cellular function controlled by CaM in various ways is cell motility. Here we discuss the role of CaM-dependent systems involved in cell migration, tumor cell invasiveness, and metastasis development. Emphasis is given to phosphorylation/dephosphorylation events catalyzed by myosin light-chain kinase, CaM-dependent kinase-II, as well as other CaM-dependent kinases, and the CaM-dependent phosphatase calcineurin. In addition, the role of the CaM-regulated small GTPases Rac1 and Cdc42 (cell division cycle protein 42) as well as CaM-binding adaptor/scaffold proteins such as Grb7 (growth factor receptor bound protein 7), IQGAP (IQ motif containing GTPase activating protein) and AKAP12 (A kinase anchoring protein 12) will be reviewed. CaM-regulated mechanisms in cancer cells responsible for their greater migratory capacity compared to non-malignant cells, invasion of adjacent normal tissues and their systemic dissemination will be discussed, including closely linked processes such as the epithelial–mesenchymal transition and the activation of metalloproteases. This review covers as well the role of CaM in establishing metastatic foci in distant organs. Finally, the use of CaM antagonists and other blocking techniques to downregulate CaM-dependent systems aimed at preventing cancer cell invasiveness and metastasis development will be outlined.

A Metastatic Mouse Model Identifies Genes That Regulate Neuroblastoma Metastasis

Metastatic relapse is the major cause of death in pediatric neuroblastoma, where there remains a lack of therapies to target this stage of disease. To understand the molecular mechanisms mediating neuroblastoma metastasis, we developed a mouse model using intracardiac injection and in vivo selection to isolate malignant cell subpopulations with a higher propensity for metastasis to bone and the central nervous system. Gene expression profiling revealed primary and metastatic cells as two distinct cell populations defined by differential expression of 412 genes and of multiple pathways, including CADM1, SPHK1, and YAP/TAZ, whose expression independently predicted survival. In the metastatic subpopulations, a gene signature was defined (MET-75) that predicted survival of neuroblastoma patients with metastatic disease. Mechanistic investigations demonstrated causal roles for CADM1, SPHK1, and YAP/TAZ in mediating metastatic phenotypes in vitro and in vivo Notably, pharmacologic targeting of SPHK1 or YAP/TAZ was sufficient to inhibit neuroblastoma metastasis in vivo Overall, we identify gene expression signatures and candidate therapeutics that could improve the treatment of metastatic neuroblastoma. Cancer Res; 77(3); 696-706. ©2017 AACR.

New models of hematogenous ovarian cancer metastasis demonstrate preferential spread to the ovary and a requirement for the ovary for abdominal dissemination

Emerging evidence suggest that many high-grade serous "ovarian" cancers (HGSOC) start in the fallopian tube. Cancer cells are then recruited to the ovary and then spread diffusely through the abdomen. The mechanism of ovarian cancer spread was thought to be largely due to direct shedding of tumor cells into the peritoneal cavity with vascular spread being of limited importance. Recent work challenges this dogma, suggesting hematogenous spread of ovarian cancer may play a larger role in ovarian cancer cell metastasis than previously thought. One reason the role of vascular spread of ovarian cancer has not been fully elucidated is the lack of easily accessible models of vascular ovarian cancer metastasis. Here, we present 3 metastatic models of ovarian cancer which confirm the ability of ovarian cancer to hematogenously spread. Strikingly, we observe a high rate of metastasis to the ovary with the development of ascites in these models. Interestingly, oophorectomy resulted in a complete loss of peritoneal metastases and ascites. Taken together, our data indicate that hematogenously disseminated HGSOC cells have a unique tropism for the ovary and that hematogenous spread in ovarian cancer may be more common than appreciated. Furthermore, our studies support a critical role for the ovary in promoting HGSOC cell metastasis to the abdomen. The models developed here represent important new tools to evaluate both the mechanism of cancer cell recruitment to the ovary and understand and target key steps in ovarian cancer metastasis.

Whole-body optical imaging in animal models to assess cancer development and progression

Different optical-based imaging models were used to investigate tumor progression and metastasis with particular emphasis on metastasis to bone and bone marrow. We describe how optical imaging can be used to follow important processes in tumor development and treatment response, including angiogenesis, apoptosis, and proteolysis. Finally, we discuss the translation of one optical imaging modality, near-IR fluorescence, from animal validation studies to applications in the clinic related to cancer management.

In vivoechographic evidence of tumoral vascularization and microenvironment interactions in metastatic orthotopic human neuroblastoma xenografts

Human neuroblastoma (NB) is the second most frequent solid tumor of childhood and represents a highly heterogeneous disease at clinical and biologic levels. Little progress has been made to improve the poor prognosis of patients with high-stage NB. Tumor progression and metastatic dissemination still represent major obstacles to the successful treatment of advanced stage disease. In order to develop and evaluate new, targeted, therapeutic strategies, fully defined and biologically relevant in vivo models of NB are strongly needed. We have developed an orthotopic model of metastatic human NB in the nude mouse, using 2 well-characterized NB cell lines. Tumor growth, vascular properties and metastatic patterns were investigated using a sensitive and newly developed in vivo echographic technology in addition to immunohistochemistry and PCR analyses. Results show that implantation of low numbers of NB cells directly into the adrenal gland of nude mice resulted in rapid and homogeneous tumor growth without tumor morbidity. Nude mice were shown to rapidly develop highly vascularized adrenal tumors that selectively metastasized to the liver and bone marrow. In addition, the newly formed mouse vessels in orthotopic but not in heterotopic tumors, were found to express the highly angiogenic alphavbeta3 integrin marker, indicating the development of a truly malignant neovasculature in orthotopic conditions only. This observation confirms the impact of the regional microenvironment on tumor biology and suggests the existence of cross-talk with the tumor cells. In conclusion, such model faithfully reproduces the growth, vascular and metastatic patterns as observed in patients. It therefore represents a powerful and biologically relevant tool to improve our understanding of the biology of NB and to develop and assess new antiangiogenic and metastasis-targeted therapies.

A murine model of bone marrow micrometastasis in breast cancer

Bone marrow (BM) is one of the most common sites and often the first clinical indication of metastatic progression of breast cancer. Multivariate analyses have shown that the presence of cytokeratin positive tumor cells in the marrow of women with newly diagnosed stage I, II or III breast cancer is an independent predictor of survival. The objective of this study was to develop an orthotopic model of spontaneous BM metastasis to facilitate studies of this process. A murine mammary adenocarcinoma cell line, Clone 66, was transduced with the neomycin resistance gene (Cl66neo) and injected orthotopically into female Balb/c mice. Polymerase chain reaction (PCR) for the neo gene performed on BM cells harvested from tumor bearing mice demonstrated as few as 10(2) injected tumor cells produced BM micrometastases at 4 weeks postinjection. Small foci of tumor cells were identified in the mammary fatpad (mfp) without gross evidence of primary tumors. Higher doses of tumor cells produced BM micrometastases, detectable by PCR, at one week post-injection. Constructs containing green fluorescent protein (GFP) and the neomycin resistance gene (neo) were also transduced into Clone 66 cells (Cl66-GFPneo) and injected into the mfp. GFP transduced tumor cells were identified in multiple tissues in addition to BM by flow cytometric analysis (FACS) but less 13% of the animals developed gross metastases. This model is a clinically relevant tool for the analysis of organ specificity of metastasis.

Murine models for experimental therapy of pediatric solid tumors with poor prognosis

Novel therapeutic strategies are required for pediatric solid tumors with poor prognosis such as metastasizing neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma. A prerequisite for the development of such new therapies is the availability of murine models. To be useful for therapeutic studies, these models should not only recapitulate the genetic alterations characteristic of the human disease but should also mimic the metastatic process and the response to current therapy, both of which ultimately determine the fate of children with these tumors. This review scrutinizes the utility of existing murine models of neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma for investigating novel therapies. Much experience has been gained with both syngeneic and xenogeneic transplantable models of these tumors, while transgenic and knockout mice are just beginning to be available for therapeutic investigations. Modeling the genetic aberrations characterizing these tumors may provide faithful models for therapeutic studies in the future.

Murine model for skeletal metastases of Ewing's sarcoma

Ewing's sarcoma shows a strong tendency to metastasize to the lungs or the skeleton, or both. A peculiar feature of the secondary involvement of bone with this tumor is that it may also appear in the absence of clinically evident lung metastases, both at clinical presentation and during the course of the disease. Although osseous metastases are critically relevant for prognosis, the pathogenesis of this peculiar feature of Ewing's sarcoma is poorly understood, partly due to the lack of appropriate experimental in vivo models. We show that the intravenous injection of TC-71 Ewing's sarcoma cells into athymic 4-5-week-old Crl/nu/nu (CD1) BR mice reproducibly colonizes specific sites of the skeleton in addition to the lungs and lymph nodes. The distribution and the morphologic appearance of these experimental bone metastases mimic the pattern of skeletal involvement observed in humans. This experimental model of bone metastasis of Ewing's sarcoma may be the basis for future studies aimed at understanding the pathophysiology and treatment of Ewing's sarcoma.

N-methylformamide induces changes on adhesive properties and lung-colonizing potential of M14 melanoma cells

We have studied whether N-methylformamide can affect the expression pattern of adhesion molecules and the attachment behaviour of M14 human melanoma cells. The role of N-methylformamide on experimental and spontaneous pulmonary metastases from M14 cells in nude mice was also investigated. We demonstrate that N-methylformamide in vitro pretreatment of M14 cells, although inducing a significant increase in the expression of alpha2beta1, alpha6beta1 and alpha(v)beta3 integrin receptors, slightly modifies alpha5beta1 heterodimer and beta1 subunit expression. After this modulation, enhancement of cell adhesion to laminin, collagen I, vitronectin and fibrinogen, which is blocked by specific anti-integrin antibodies, also occurs. No changes in binding to fibronectin are observed. In vitro N-methylformamide pretreatment also results in an increased number of experimental nodules and in a decrease in spontaneous metastases. Moreover, in vivo treatment with N-methylformamide significantly reduces the number of spontaneous metastases. Collectively, these data show that N-methylformamide modulates the expression of some adhesion receptors, cell adhesion to laminin, collagen I, vitronectin and fibrinogen as well as the metastatic behaviour of M14 cells. Our data also suggest that the effect of N-methylformamide might be evaluated in combination with antineoplastic agents for the treatment of human melanoma.

Targeted interleukin-2 therapy for spontaneous neuroblastoma metastases to bone marrow

BACKGROUND

Advanced (stage 4) cases of neuroblastoma, a childhood cancer of the nervous system, are associated with high relapse rates, even after intensive chemotherapy, radiotherapy, and autologous bone marrow transplantation. Therefore, the use of monoclonal antibodies directed against the neuroblastoma tumor marker disialoganglioside GD2 (GD2), in combination with recombinant human interleukin 2 (rhIL-2), is under clinical investigation. We hypothesize that targeted cytokine immunotherapy with a recombinant anti-GD2 antibody-interleukin 2 fusion protein (ch14.18-IL-2) is superior to a combination of ch14.18 and rhIL-2. Our purpose was as follows: 1) to develop a syngeneic model for murine neuroblastoma that expresses GD2 and features both experimental and spontaneous metastases to bone marrow and liver, and 2) to assess anti-GD2-targeted IL-2 therapy in this mode.

METHODS

A hybrid neuroblastoma cell line was used to generate the GD2-positive NXS2 cell line. Bone marrow and liver metastases were quantified by reverse transcription-polymerase chain reaction for tyrosine hydroxylase and by organ weight or counts of macroscopic tumor foci, respectively. All P values reported are two-sided.

RESULTS

Injection of NXS2 cells resulted in disseminated bone marrow and liver metastases exhibiting stable, but heterogeneous expression of GD2. Treatment with fusion protein (10 microg/day for 6 days) effectively suppressed growth of both experimental and spontaneous metastases to bone marrow and liver (P<.001). In contrast, a mixture of rhIL-2 and ch14.18 at equivalent dose levels was inefficient. Only mice treated with ch14.18-IL-2 showed a twofold prolongation in life span (P<.001).

CONCLUSION

Targeted IL-2 therapy with a ch14.18-IL-2 fusion protein elicits an effective antitumor response. Our data suggest that a study of ch14.18-IL-2 as an adjuvant treatment in patients with minimal residual disease may be of value.

Organ-specific adhesion of neuroblastoma cells in vitro: correlation with their hepatic metastasis potential

Neuroblastoma (NB) is the most common solid malignant tumor found in pediatric patients and the liver is one of the major sites of metastasis. To investigate the organ specificity of metastatic distribution, the adherence behavior of tumor cells was studied. The data presented are based on studies using a metastatic murine cell line C1300. In vivo, not only intrasplenic but also intravascular injection of C1300 NB cells consistently results in hepatic metastasis formation in syngeneic A/J mice. An in vitro assay was used in which C1300 NB cell attachment to cryostat sections of liver, spleen, brain, kidney and lung obtained from normal A/J mice was measured to compare organ-specific adhesion. A good correlation was found between their metastatic potential in the liver and the adhesion to the liver sections; C1300 NB cells adhered preferentially to liver cryostat sections. Enzyme assays indicated that cell surface glycoproteins were involved in cell adhesion. An adhesion assay with extracellular matrix proteins demonstrated that C1300 NB cells adhered preferentially to vitronectin and fibronectin, and the adherence was strongly inhibited by Arg-Gly-Asp (RGD)-containing peptides. Furthermore, adhesion of C1300 NB cells to liver cryostat sections could be blocked by the synthetic peptide GRGDS. This indicates that the interaction between RGD-containing matrix adhesion protein and cells has an important role for the specific adhesion of C1300 NB cells. The results suggested that tumor cell adhesion to liver cryostat sections could provide a useful tool in the study of host-tumor interactions in the metastasis of NB.

Histopathologic analysis of bone marrow and bone metastasis in murine neuroblastoma

To elucidate the development of bone metastasis in human neuroblastoma, bone marrow and bone metastases were analysed histologically in a hematogeneous metastasis model of murine neuroblastoma. The bone marrow metastasis occurred initially in the bone marrow sinusoid where tumor cells adhered and extravasated to bone marrow parenchyma, resulting in the formation of nodular lesions in the medullary cavity. The nodular lesions eventually progressed to diffuse lesions segmentally occupying the medullary cavity. During the establishment of the diffuse lesions, tumor cells invaded cancellous bone and/or bone cortex, resulting in bone metastasis. Such nodular or diffuse bone marrow metastatic lesions occurred sporadically in a variety of bones. To improve the results of treatment for neuroblastoma, the characteristics of the bone marrow and the bone metastases demonstrated in this study should be considered in the diagnosis and treatment of this disease.

Disseminated neuroblastoma in the nude rat. A xenograft model of human malignancy

BACKGROUND

The overall survival of children with neuroblastoma remains less than 30% due to disease dissemination at the time of diagnosis. An animal model of neuroblastoma, with characteristics similar to those observed clinically in children, would be beneficial to investigations into the diverse biology of this tumor. The purpose of this study was (1) to develop a model of disseminated neuroblastoma in the nude rat by intracardiac injection of neuroblastoma cells derived from cell lines with different N-myc copy numbers; (2) to investigate the effect of age on tumor growth and dissemination; and (3) to assess progression of disease radiologically and correlate with autopsy findings.

METHODS

Nude rats (n = 38), 5-13 weeks of age, underwent intracardiac injection of the human neuroblastoma cell lines IMR-32 with amplified N-myc oncogene and SKNSH with 1 N-myc copy. The animals were observed for at least six weeks for the development of tumor. Twelve rodents injected with IMR-32 cells underwent imaging studies including magnetic resonance imaging (MRI), skeletal radiographs, and indium-111(IN-111)-diethylenetriamine penta-acetic acid-D-Phe1-octreotide scintigraphy. Autopsies with standardized microscopic examinations were performed on all animals.

RESULTS

Most of the nude rats (95%) developed neuroblastoma following intracardiac injection of neoplastic cells. Disseminated tumor was evident in 66% of animals. Anatomic sites of neuroblastoma growth were similar to those observed clinically in children, including adrenal glands, paraspinal ganglia, bone, bone marrow, and skin, but no tumor was identified in the liver. Disseminated disease occurred in more animals injected with IMR-32 (78% of animals) than with SKNSH cells (34% of animals) (P < 0.05). Tumor spread appeared to be age dependent; only rodents 5-8 weeks old at the time of injection developed disseminated disease when compared with animals 9 weeks of age or older (P < 0.0001). Radioreceptor scintigraphy demonstrated only pericardial tumor; MRI identified pericardial, adrenal gland, and subcutaneous neoplasms; only skeletal radiographs detected neuroblastoma in cortical bone.

CONCLUSIONS

(1) Following intracardiac injection of human neuroblastoma cell lines into nude rats, a xenograft model of disseminated disease develops that closely parallels the malignant process in children. (2) Tumor dissemination is associated with the cell line that demonstrates N-myc amplification and with young age of the recipient at the time of injection. (3) Tumor growth and dissemination may be assessed radiologically. (4) This model of human malignancy may offer an opportunity to investigate the pathophysiologic mechanisms underlying tumor development and dissemination in advanced stage neuroblastoma.