Using 3D-bioprinted models to study pediatric neural crest-derived tumors

The use of three-dimensional (3D) bioprinting has remained at the forefront of tissue engineering and has recently been employed for generating bioprinted solid tumors to be used as cancer models to test therapeutics. In pediatrics, neural crest-derived tumors are the most common type of extracranial solid tumors. There are only a few tumor-specific therapies that directly target these tumors, and the lack of new therapies remains detrimental to improving the outcomes for these patients. The absence of more efficacious therapies for pediatric solid tumors, in general, may be due to the inability of the currently employed preclinical models to recapitulate the solid tumor phenotype. In this study, we utilized 3D bioprinting to generate neural crest-derived solid tumors. The bioprinted tumors consisted of cells from established cell lines and patient-derived xenograft tumors mixed with a 6% gelatin/1% sodium alginate bioink. The viability and morphology of the bioprints were analyzed via bioluminescence and immunohisto chemistry, respectively. We compared the bioprints to traditional twodimensional (2D) cell culture under conditions such as hypoxia and therapeutics. We successfully produced viable neural crest-derived tumors that retained the histology and immunostaining characteristics of the original parent tumors. The bioprinted tumors propagated in culture and grew in orthotopic murine models. Furthermore, compared to cells grown in traditional 2D culture, the bioprinted tumors were resistant to hypoxia and chemotherapeutics, suggesting that the bioprints exhibited a phenotype that is consistent with that seen clinically in solid tumors, thus potentially making this model superior to traditional 2D culture for preclinical investigations. Future applications of this technology entail the potential to rapidly print pediatric solid tumors for use in high-throughput drug studies, expediting the identification of novel, individualized therapies.

PIM3 kinase promotes tumor metastasis in hepatoblastoma by upregulating cell surface expression of chemokine receptor cxcr4

Patients presenting with metastatic hepatoblastoma have limited treatment options and survival rates as low as 25%. We previously demonstrated that Proviral Integration site in Maloney murine leukemia virus 3 (PIM3) kinase promotes tumorigenesis and cancer cell stemness in hepatoblastoma. In this study, we assessed the role of PIM3 kinase in promoting hepatoblastoma metastasis. We utilized a tail vein injection model of metastasis to evaluate the effect of CRISPR/Cas9-mediated PIM3 knockout, stable overexpression of PIM3, and pharmacologic PIM inhibition on the formation of lung metastasis. In vivo studies revealed PIM3 knockout impaired the formation of lung metastasis: 5 out of 6 mice injected with wild type hepatoblastoma cells developed lung metastasis while none of the 7 mice injected with PIM3 knockout hepatoblastoma cells developed lung metastasis. PIM3 overexpression in hepatoblastoma increased the pulmonary metastatic burden in mice and mechanistically, upregulated the phosphorylation and cell surface expression of CXCR4, a key receptor in the progression of cancer cell metastasis. CXCR4 blockade with AMD3100 decreased the metastatic phenotype of PIM3 overexpressing cells, indicating that CXCR4 contributed to PIM3's promotion of hepatoblastoma metastasis. Clinically, PIM3 expression correlated positively with CXCR4 expression in primary hepatoblastoma tissues. In conclusion, we have shown PIM3 kinase promotes the metastatic phenotype of hepatoblastoma cells through upregulation of CXCR4 cell surface expression and these findings suggest that targeting PIM3 kinase may provide a novel therapeutic strategy for metastatic hepatoblastoma.

Rapid Characterization of Solid Tumors Using Resonant Sensors

Cancer continues to be a significant cause of non-traumatic pediatric mortality. Diagnosis of pediatric solid tumors is paramount to prescribing the correct treatment regimen. Recent efforts have focused on non-invasive methods to obtain tumor tissues, but one of the challenges encountered is the ability to obtain an adequate amount of viable tissue. In this study, a wireless, inductor-capacitor (LC) sensor was employed to detect relative permittivity of pediatric tumor tissues. There is a comparison of resonant frequencies of tumor tissues between live versus dead tissues, the primary tumor tissue versus tissue from the organs of origin or metastasis, and treated versus untreated tumors. The results show significant shifts in resonant frequencies between the comparison groups. Dead tissues demonstrated a significant shift in resonant frequencies compared to alive tissues. There were significant differences between the resonant frequencies of normal tissues versus tumor tissues. Resonant frequencies were also significantly different between primary tumors compared to their respective metastases. These data indicate that there are potential clinical applications of LC technology in the detection and diagnosis of pediatric solid tumors.

Metastatic human hepatoblastoma cells exhibit enhanced tumorigenicity, invasiveness and a stem cell-like phenotype

BACKGROUND/PURPOSE

Metastatic hepatoblastoma continues to pose a significant treatment challenge, primarily because the precise mechanisms involved in metastasis are not fully understood, making cell lines and preclinical models that depict the progression of disease and metastasis-related biology paramount. We aimed to generate and characterize a metastatic hepatoblastoma cell line to create a model for investigation of the molecular mechanisms associated with metastasis.

MATERIALS/METHODS

Using a murine model of serial tail vein injections of the human hepatoblastoma HuH6 cell line, non-invasive bioluminescence imaging, and dissociation of metastatic pulmonary lesions, we successfully established and characterized the metastatic human hepatoblastoma cell line, HLM_3.

RESULTS

The HLM_3 cells exhibited enhanced tumorigenicity and invasiveness, both in vitro and in vivo compared to the parent HuH6 cell line. Moreover, HLM_3 metastatic hepatoblastoma cells exhibited a stem cell-like phenotype and were more resistant to the standard chemotherapeutic cisplatin.

CONCLUSION

This newly described metastatic hepatoblastoma cell line offers a novel tool to study mechanisms of tumor metastasis and evaluate new therapeutic strategies for metastatic hepatoblastoma.

CRISPR/Cas9-mediated knockout of PIM3 suppresses tumorigenesis and cancer cell stemness in human hepatoblastoma cells

Hepatoblastoma remains one of the most difficult childhood tumors to treat and is alarmingly understudied. We previously demonstrated that Proviral Insertion site in Maloney murine leukemia virus (PIM) kinases, specifically PIM3, are overexpressed in human hepatoblastoma cells and function to promote tumorigenesis. We aimed to use CRISPR/Cas9 gene editing with dual gRNAs to introduce large inactivating deletions in the PIM3 gene and achieve stable PIM3 knockout in the human hepatoblastoma cell line, HuH6. PIM3 knockout of hepatoblastoma cells led to significantly decreased proliferation, viability, and motility, inhibited cell-cycle progression, decreased tumor growth in a xenograft murine model, and increased animal survival. Analysis of RNA sequencing data revealed that PIM3 knockout downregulated expression of pro-migratory and pro-invasive genes and upregulated expression of genes involved in apoptosis and differentiation. Furthermore, PIM3 knockout decreased hepatoblastoma cancer cell stemness as evidenced by decreased tumorsphere formation, decreased mRNA abundance of stemness markers, and decreased cell surface expression of CD133, a marker of hepatoblastoma stem cell-like cancer cells. Reintroduction of PIM3 into PIM3 knockout cells rescued the malignant phenotype. Successful CRISPR/Cas9 knockout of PIM3 kinase in human hepatoblastoma cells confirmed the role of PIM3 in promoting hepatoblastoma tumorigenesis and cancer cell stemness.

Targeting High-Risk Neuroblastoma Patient-Derived Xenografts with Oncolytic Virotherapy

Cancer is the leading cause of death by disease in children, and over 15% of pediatric cancer-related mortalities are due to neuroblastoma. Current treatment options for neuroblastoma remain suboptimal as they often have significant toxicities, are associated with long-term side effects, and result in disease relapse in over half of children with high-risk disease. There is a dire need for new therapies, and oncolytic viruses may represent an effective solution. Oncolytic viruses attack tumor cells in two ways: direct infection of tumor cells leading to cytolysis, and production of a debris field that stimulates an anti-tumor immune response. Our group has previously shown that M002, an oncolytic herpes simplex virus (oHSV), genetically engineered to express murine interleukin-12 (mIL-12), was effective at targeting and killing long term passage tumor cell lines. In the current study, we investigated M002 in three neuroblastoma patient-derived xenografts (PDXs). PDXs better recapitulate the human condition, and these studies were designed to gather robust data for translation to a clinical trial. We found that all three PDXs expressed viral entry receptors, and that the virus actively replicated in the cells. M002 caused significant tumor cell death in 2D culture and 3D bioprinted tumor models. Finally, the PDXs displayed variable susceptibility to M002, with a more profound effect on high-risk neuroblastoma PDXs compared to low-risk PDX. These findings validate the importance of incorporating PDXs for preclinical testing of oncolytic viral therapeutics and showcase a novel technique, 3D bioprinting, to test therapies in PDXs. Collectively, our data indicate that oHSVs effectively target high-risk neuroblastoma, and support the advancement of this therapy to the clinical setting.

Downregulation of PDGFRß Signaling Overcomes Crizotinib Resistance in a TYRO3 and ALK Mutated Neuroendocrine-Like Tumor

Patient-derived xenografts provide significant advantages over long-term passage cell lines when investigating efficacy of treatments for solid tumors. Our laboratory encountered a high-grade, metastatic, neuroendocrine-like tumor from a pediatric patient that presented with a unique genetic profile. In particular, mutations in TYRO3 and ALK were identified. We established a human patient-derived xenoline (PDX) of this tumor for use in the current study. We investigated the effect of crizotinib, a chemotherapeutic known to effectively target both TYRO3 and ALK mutations. Crizotinib effectively decreased viability, proliferation, growth, and the metastatic properties of the PDX tumor through downregulation of STAT3 signaling, but expression of PDGFRß was increased. Sunitinib is a small molecule inhibitor of PDGFRß and was studied in this PDX independently and in combination with crizotinib. Sunitinib alone decreased viability, proliferation, and growth in vitro and decreased tumor growth in vivo. In combination, sunitinib was able to overcome potential crizotinib-induced resistance through downregulation of ERK 1/2 activity and PDGFRß receptor expression; consequently, tumor growth was significantly decreased both in vitro and in vivo. Through the use of the PDX, it was possible to identify crizotinib as a less effective therapeutic for this tumor and suggest that targeting PDGFRß would be more effective. These findings may translate to other solid tumors that present with the same genetic mutations.

PIM447 inhibits oncogenesis and potentiates cisplatin effects in hepatoblastoma

BACKGROUND

Novel therapies are needed for patients with hepatoblastoma because of an increasing incidence of disease and poor prognosis for advanced, refractory, and recurrent disease. PIM kinases promote tumorigenesis in hepatoblastoma. A novel PIM inhibitor, PIM447, has shown promise in inhibiting oncogenesis in hematologic and lymphoid malignancies. We hypothesized that PIM inhibition with PIM447 would result in decreased tumorigenesis in hepatoblastoma.

METHODS

The effects of PIM447 on hepatoblastoma viability, proliferation, motility, apoptosis, and tumor cell stemness were assessed in HuH6, a human hepatoblastoma cell line, and COA67, a human hepatoblastoma patient-derived xenograft.

RESULTS

PIM447 significantly decreased the viability, proliferation, and motility of HuH6 and COA67 cells. Apoptosis significantly increased following PIM447 treatment. PIM447 had a significant impact on tumor cell stemness as evidenced by decreased expression of CD133 and reduced ability of HuH6 and COA67 cells to form tumorspheres. Furthermore, combining PIM447 with cisplatin resulted in a significant decrease in cell viability compared to either treatment alone.

CONCLUSION

We showed that PIM447 inhibits oncogenesis and potentiates the effects of cisplatin in hepatoblastoma and, therefore, warrants further investigation as a potential therapeutic agent for hepatoblastoma.

Novel second-generation rexinoid induces growth arrest and reduces cancer cell stemness in human neuroblastoma patient-derived xenografts

INTRODUCTION

The poor therapeutic efficacy seen with current treatments for neuroblastoma may be attributed to stem cell-like cancer cells (SCLCCs), a subpopulation of cancer cells associated with poor prognosis and disease recurrence. Retinoic acid (RA) is a differentiating agent used as maintenance therapy for high-risk neuroblastoma but nearly half of children treated with RA relapse. We hypothesized that 6-Methyl-UAB30 (6-Me), a second-generation rexinoid recently developed with a favorable toxicity profile compared to RA, would reduce cancer cell stemness in human neuroblastoma patient-derived xenografts (PDXs).

METHODS

Cells from three neuroblastoma PDXs were treated with 6-Me and proliferation, viability, motility, and cell-cycle progression were assessed. CD133 expression, sphere formation, and mRNA abundance of stemness and differentiation markers were evaluated using flow cytometry, in vitro extreme limiting dilution analysis, and real-time PCR, respectively.

RESULTS

Treatment with 6-Me decreased proliferation, viability, and motility, and induced cell-cycle arrest and differentiation in all three neuroblastoma PDXs. In addition, 6-Me treatment led to decreased CD133 expression, decreased sphere-forming ability, and decreased mRNA abundance of Oct4, Nanog, and Sox2, indicating decreased cancer cell stemness.

CONCLUSIONS

6-Me decreased oncogenicity and reduced cancer cell stemness of neuroblastoma PDXs, warranting further exploration of 6-Me as potential novel therapy for neuroblastoma.

The effects of focal adhesion kinase and platelet-derived growth factor receptor beta inhibition in a patient-derived xenograft model of primary and metastatic Wilms tumor

Aggressive therapies for patients with metastatic Wilms tumor (WT) with subsequent severe late effects warrant the search for novel therapies. The role of focal adhesion kinase (FAK), a non-receptor tyrosine kinase important in pediatric solid tumor development and progression, has not been examined in metastatic WT. Using a novel patient-derived xenograft (PDX) of a primary and matched, isogenic, metastatic WT, the hypothesis of the current study was that FAK would contribute to metastatic WT and small molecule inhibition would decrease tumor growth. Immunohistochemical staining, immunoblotting, cell viability and proliferation assays, cell cycle analysis, and cellular motility and attachment-independent growth assays were performed. FAK was present and phosphorylated in both WT PDXs and in the human samples from which they were derived. FAK inhibition decreased cellular survival, proliferation, and cell cycle progression in both PDXs but only significantly decreased migration, invasion, and attachment-independent growth in the primary WT PDX. Kinomic profiling revealed that platelet-derived growth factor receptor beta (PDGFRβ) may be affected by FAK inhibition in WT. Pharmacologic inhibition of FAK and PDGFRβ was synergistic in primary WT PDX cells. These findings broaden the knowledge of metastatic WT and support further investigations on the potential use of FAK and PDGFRβ inhibitors.

Focal Adhesion Kinase Inhibition Contributes to Tumor Cell Survival and Motility in Neuroblastoma Patient-Derived Xenografts

Patient-derived xenografts (PDXs) provide an opportunity to evaluate the effects of therapies in an environment that more closely resembles the human condition than that seen with long-term passage cell lines. In the current studies, we investigated the effects of FAK inhibition on two neuroblastoma PDXs in vitro. Cells were treated with two small molecule inhibitors of FAK, PF-573,228 (PF) and 1,2,4,5-benzentetraamine tetrahydrochloride (Y15). Following FAK inhibition, cell survival and proliferation decreased significantly and cell cycle arrest was seen in both cell lines. Migration and invasion assays were used to determine the effect of FAK inhibition on cell motility, which decreased significantly in both cell lines in the presence of either inhibitor. Finally, tumor cell stemness following FAK inhibition was evaluated with extreme limiting dilution assays as well as with immunoblotting and quantitative real-time PCR for the expression of stem cell markers. FAK inhibition decreased formation of tumorspheres and resulted in a corresponding decrease in established stem cell markers. FAK inhibition decreased many characteristics of the malignant phenotype, including cancer stem cell like features in neuroblastoma PDXs, making FAK a candidate for further investigation as a potential target for neuroblastoma therapy.