TAp73 represses NF-κB-mediated recruitment of tumor-associated macrophages in breast cancer.

Infiltration of tumor-promoting immune cells is a strong driver of tumor progression. Especially the accumulation of macrophages in the tumor microenvironment is known to facilitate tumor growth and to correlate with poor prognosis in many tumor types. TAp73, a member of the p53/p63/p73 family, acts as a tumor suppressor and has been shown to suppress tumor angiogenesis. However, what role TAp73 has in regulating immune cell infiltration is unknown. Here, we report that low levels of TAp73 correlate with an increased NF-κB-regulated inflammatory signature in breast cancer. Furthermore, we show that loss of TAp73 results in NF-κB hyperactivation and secretion of Ccl2, a known NF-κB target and chemoattractant for monocytes and macrophages. Importantly, TAp73-deficient tumors display an increased accumulation of protumoral macrophages that express the mannose receptor (CD206) and scavenger receptor A (CD204) compared to controls. The relevance of TAp73 expression in human breast carcinoma was further accentuated by revealing that TAp73 expression correlates negatively with the accumulation of protumoral CD163+ macrophages in breast cancer patient samples. Taken together, our findings suggest that TAp73 regulates macrophage accumulation and phenotype in breast cancer through inhibition of the NF-κB pathway.

Modeling SHH-driven medulloblastoma with patient iPS cell-derived neural stem cells.

Medulloblastoma is the most common malignant brain tumor in children. Here we describe a medulloblastoma model using Induced pluripotent stem (iPS) cell-derived human neuroepithelial stem (NES) cells generated from a Gorlin syndrome patient carrying a germline mutation in the sonic hedgehog (SHH) receptor PTCH1. We found that Gorlin NES cells formed tumors in mouse cerebellum mimicking human medulloblastoma. Retransplantation of tumor-isolated NES (tNES) cells resulted in accelerated tumor formation, cells with reduced growth factor dependency, enhanced neurosphere formation in vitro, and increased sensitivity to Vismodegib. Using our model, we identified LGALS1 to be a GLI target gene that is up-regulated in both Gorlin tNES cells and SHH-subgroup of medulloblastoma patients. Taken together, we demonstrate that NES cells derived from Gorlin patients can be used as a resource to model medulloblastoma initiation and progression and to identify putative targets.

High-throughput neural stem cell-based drug screening identifies S6K1 inhibition as a selective vulnerability in sonic hedgehog-medulloblastoma.

BACKGROUND: Medulloblastoma (MB) is one of the most common malignant brain tumors in children. Current treatments have increased overall survival but can lead to devastating side effects and late complications in survivors, emphasizing the need for new, improved targeted therapies that specifically eliminate tumor cells while sparing the normally developing brain. METHODS: Here, we used a sonic hedgehog (SHH)-MB model based on a patient-derived neuroepithelial stem cell system for an unbiased high-throughput screen with a library of 172 compounds with known targets. Compounds were evaluated in both healthy neural stem cells (NSCs) and tumor cells derived from the same patient. Based on the difference of cell viability and drug sensitivity score between normal cells and tumor cells, hit compounds were selected and further validated in vitro and in vivo. RESULTS: We identified PF4708671 (S6K1 inhibitor) as a potential agent that selectively targets SHH-driven MB tumor cells while sparing NSCs and differentiated neurons. Subsequent validation studies confirmed that PF4708671 inhibited the growth of SHH-MB tumor cells both in vitro and in vivo, and that knockdown of S6K1 resulted in reduced tumor formation. CONCLUSIONS: Overall, our results suggest that inhibition of S6K1 specifically affects tumor growth, whereas it has less effect on non-tumor cells. Our data also show that the NES cell platform can be used to identify potentially effective new therapies and targets for SHH-MB.

Development of an orthotopic medulloblastoma zebrafish model for rapid drug testing.

BACKGROUND: Medulloblastoma (MB) is one of the most common malignant brain tumors in children. Current preclinical in vivo model systems for MB have increased our understanding of molecular mechanisms regulating MB development. However, they may not be suitable for large-scale studies. The aim of this study was to investigate if a zebrafish-based xenograft model can recapitulate MB growth and enable rapid drug testing. METHODS: Nine different MB cell lines or patient-derived cells were transplanted into blastula-stage zebrafish embryos. Tumor development and migration were then monitored using live imaging. RNA sequencing was performed to investigate transcriptome changes after conditioning cells in neural stem cell-like medium. Furthermore, drug treatments were tested in a 96-well format. RESULTS: We demonstrate here that transplantation of MB cells into the blastula stage of zebrafish embryos leads to orthotopic tumor growth that can be observed within 24 hours after transplantation. Importantly, the homing of transplanted cells to the hindbrain region and the aggressiveness of tumor growth are enhanced by pre-culturing cells in a neural stem cell-like medium. The change in culture conditions rewires the transcriptome towards a more migratory and neuronal phenotype, including the expression of guidance molecules SEMA3A and EFNB1, both of which correlate with lower overall survival in MB patients. Furthermore, we highlight that the orthotopic zebrafish MB model has the potential to be used for rapid drug testing. CONCLUSION: Blastula-stage zebrafish MB xenografts present an alternative to current MB mouse xenograft models, enabling quick evaluation of tumor cell growth, neurotropism, and drug efficacy.

The Tumor Microenvironment of Medulloblastoma: An Intricate Multicellular Network with Therapeutic Potential.

Medulloblastoma (MB) is a heterogeneous disease in which survival is highly affected by the underlying subgroup-specific characteristics. Although the current treatment modalities have increased the overall survival rates of MB up to 70-80%, MB remains a major cause of cancer-related mortality among children. This indicates that novel therapeutic approaches against MB are needed. New promising treatment options comprise the targeting of cells and components of the tumor microenvironment (TME). The TME of MB consists of an intricate multicellular network of tumor cells, progenitor cells, astrocytes, neurons, supporting stromal cells, microglia, immune cells, extracellular matrix components, and vasculature systems. In this review, we will discuss all the different components of the MB TME and their role in MB initiation, progression, metastasis, and relapse. Additionally, we briefly introduce the effect that age plays on the TME of brain malignancies and discuss the MB subgroup-specific differences in TME components and how all of these variations could affect the progression of MB. Finally, we highlight the TME-directed treatments, in which we will focus on therapies that are being evaluated in clinical trials.

Targeting the FAK-Src Complex in Desmoplastic Small Round Cell Tumors, Ewing Sarcoma, and Rhabdomyosarcoma.

Desmoplastic small round cell tumors (DSRCTs), Ewing sarcoma (ES), and alveolar and embryonal rhabdomyosarcoma (ARMS and ERMS) are malignant sarcomas typically occurring at young age, with a poor prognosis in the metastatic setting. New treatment options are necessary. Src family kinase inhibitor dasatinib single-agent treatment has been investigated in a phase 2 study in patients with advanced sarcomas including ES and RMS but failed as a single agent in these subtypes. Since previous studies demonstrated high FAK and Src activities in RMS and ES tissue and cell lines, and dasatinib treatment was shown to upregulate activated FAK, we hypothesized that FAK-Src combination treatment could potentially be an interesting treatment option for these tumor types. We examined the effects of targeting the FAK-Src complex by addressing (p)FAK and (p)Src expressions in tumor sections of DSRCT (n = 13), ES (n = 68), ARMS (n = 21), and ERMS (n = 39) and by determining the antitumor effects of single and combined treatment with FAK inhibitor defactinib and multikinase (Abl/SFK) inhibitor dasatinib in vitro on cell lines of each subtype. In vivo effects were assessed in DSRCT and ERMS models. Concurrent pFAK and pSrc expressions (H-score >50) were observed in DSRCT (67%), ES (6%), ARMS (35%), and ERMS (19%) samples. Defactinib treatment decreased pFAK expression and reduced cell viability in all subtypes. Dasatinib treatment decreased pSrc expression and cell viability in each subtype. Combination treatment led to a complete reduction in pFAK and pSrc in each cell line and showed enhanced cell viability reduction, drug synergy, DNA damage induction, and a trend toward higher apoptosis induction in DSRCT, ERMS, and ARMS but not in ES cells. These promising in vitro results unfortunately do not translate into promising in vivo results as we did not observe a significant effect on tumor volume in vivo, and the combination did not show superior effects compared to dasatinib single-agent treatment.

Olaparib and temozolomide in desmoplastic small round cell tumors: a promising combination in vitro and in vivo.

PURPOSE: Desmoplastic small round cell tumors (DSRCTs) are highly malignant and very rare soft tissue sarcomas with a high unmet need for new therapeutic options. Therefore, we examined poly(ADP-ribose) polymerase 1 (PARP1) and Schlafen-11 (SLFN11) expression in DSRCT tumor tissue and the combination of PARP inhibitor olaparib with the alkylating agent temozolomide (TMZ) in a preclinical DSRCT model. METHODS: PARP1 and SLFN11 have been described as predictive biomarkers for response to PARP inhibition. Expression of PARP1 and SLFN11 was assessed in 16 and 12 DSRCT tumor tissue samples, respectively. Effects of single-agent olaparib, and olaparib and TMZ combination treatment were examined using the preclinical JN-DSRCT-1 model. In vitro, single-agent and combination treatment effects on cell viability, the cell cycle, DNA damage and apoptosis were examined. Olaparib and TMZ combination treatment was also assessed in vivo. RESULTS: PARP1 and SLFN11 expression was observed in 100% and 92% of DSRCT tumor tissues, respectively. Olaparib treatment reduced cell viability and cell migration in a dose-dependent manner in vitro. Drug synergy between olaparib and TMZ was observed in vitro and in vivo. Combination treatment led to a cell-cycle arrest and induction of DNA damage and apoptosis, even when combined at low dosages. CONCLUSION: We show high PARP1 and SLFN11 expression in DSRCT tumor material and antitumor effects following olaparib and TMZ combination treatment in a preclinical DSRCT model. This suggests that olaparib and TMZ combination treatment could be a potential treatment option for DSRCTs.

Leukocyte Bim deficiency does not impact atherogenesis in ldlr -/- mice, despite a pronounced induction of autoimmune inflammation.

Proapoptotic Bcl-2 family member Bim is particularly relevant for deletion of autoreactive and activated T and B cells, implicating Bim in autoimmunity. As atherosclerosis is a chronic inflammatory process with features of autoimmune disease, we investigated the impact of hematopoietic Bim deficiency on plaque formation and parameters of plaque stability. Bim -/- or wild type bone marrow transplanted ldlr -/- mice were fed a Western type diet (WTD) for 5 or 10 weeks, after which they were immunophenotyped and atherosclerotic lesions were analyzed. Bim -/- transplanted mice displayed splenomegaly and overt lymphocytosis. CD4+ and CD8+ T cells were more activated (increased CD69 and CD71 expression, increased interferon gamma production). B cells were elevated by 147%, with a shift towards the pro-atherogenic IgG-producing B2 cell phenotype, resulting in a doubling of anti-oxLDL IgG1 antibody titers in serum of bim -/- mice. Bim -/- mice displayed massive intraplaque accumulation of Ig complexes and of lesional T cells, although this did not translate in changes in plaque size or stability features (apoptotic cell and macrophage content). The surprising lack in plaque phenotype despite the profound pro-atherogenic immune effects may be attributable to the sharp reduction of serum cholesterol levels in WTD fed bim -/- mice.