CAR-T cell expansion platforms yield distinct T cell differentiation states.

With investigators looking to expand engineered T cell therapies such as CAR-T to new tumor targets and patient populations, a variety of cell manufacturing platforms have been developed to scale manufacturing capacity using closed and/or automated systems. Such platforms are particularly useful for solid tumor targets, which typically require higher CAR-T cell doses. Although T cell phenotype and function are key attributes that often correlate with therapeutic efficacy, how manufacturing platforms influence the final CAR-T cell product is currently unknown. We compared 4 commonly used T cell manufacturing platforms (CliniMACS Prodigy, Xuri W25 rocking platform, G-Rex gas-permeable bioreactor, static bag culture) using identical media, stimulation, culture length, and donor starting material. Selected CD4+CD8+ cells were transduced with lentiviral vector incorporating a CAR targeting FGFR4, a promising target for pediatric sarcoma. We observed significant differences in overall expansion over the 14-day culture; bag cultures had the highest capacity for expansion while the Prodigy had the lowest (481-fold versus 84-fold, respectively). Strikingly, we also observed considerable differences in the phenotype of the final product, with the Prodigy significantly enriched for CCR7+CD45RA+ naïve/stem central memory (Tn/scm)-like cells at 46% compared to bag and G-Rex with 16% and 13%, respectively. Gene expression analysis also showed that Prodigy CAR-Ts are more naïve, less cytotoxic and less exhausted than bag, G-Rex, and Xuri CAR-Ts, and pointed to differences in cell metabolism that were confirmed via metabolic assays. We hypothesized that dissolved oxygen level, which decreased substantially during the final 3 days of the Prodigy culture, may contribute to the observed differences in T cell phenotype. By culturing bag and G-Rex cultures in 1% O2 from day 5 onward, we could generate >60% Tn/scm-like cells, with longer time in hypoxia correlating with a higher percentage of Tn/scm-like cells. Intriguingly, our results suggest that oxygenation is responsible, at least in part, for observed differences in T cell phenotype among bioreactors and suggest hypoxic culture as a potential strategy prevent T cell differentiation during expansion. Ultimately, our study demonstrates that selection of bioreactor system may have profound effects not only on the capacity for expansion, but also on the differentiation state of the resulting CAR-T cells.

Preclinical development of a chimeric antigen receptor T cell therapy targeting FGFR4 in rhabdomyosarcoma.

Pediatric patients with relapsed or refractory rhabdomyosarcoma (RMS) have dismal cure rates, and effective therapy is urgently needed. The oncogenic receptor tyrosine kinase fibroblast growth factor receptor 4 (FGFR4) is highly expressed in RMS and lowly expressed in healthy tissues. Here, we describe a second-generation FGFR4-targeting chimeric antigen receptor (CAR), based on an anti-human FGFR4-specific murine monoclonal antibody 3A11, as an adoptive T cell treatment for RMS. The 3A11 CAR T cells induced robust cytokine production and cytotoxicity against RMS cell lines in vitro. In contrast, a panel of healthy human primary cells failed to activate 3A11 CAR T cells, confirming the selectivity of 3A11 CAR T cells against tumors with high FGFR4 expression. Finally, we demonstrate that 3A11 CAR T cells are persistent in vivo and can effectively eliminate RMS tumors in two metastatic and two orthotopic models. Therefore, our study credentials CAR T cell therapy targeting FGFR4 to treat patients with RMS.

Preclinical Evaluation of the FGFR-Family Inhibitor Futibatinib for Pediatric Rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma. Despite decades of clinical trials, the overall survival rate for patients with relapsed and metastatic disease remains below 30%, underscoring the need for novel treatments. FGFR4, a receptor tyrosine kinase that is overexpressed in RMS and mutationally activated in 10% of cases, is a promising target for treatment. Here, we show that futibatinib, an irreversible pan-FGFR inhibitor, inhibits the growth of RMS cell lines in vitro by inhibiting phosphorylation of FGFR4 and its downstream targets. Moreover, we provide evidence that the combination of futibatinib with currently used chemotherapies such as irinotecan and vincristine has a synergistic effect against RMS in vitro. However, in RMS xenograft models, futibatinib monotherapy and combination treatment have limited efficacy in delaying tumor growth and prolonging survival. Moreover, limited efficacy is only observed in a PAX3-FOXO1 fusion-negative (FN) RMS cell line with mutationally activated FGFR4, whereas little or no efficacy is observed in PAX3-FOXO1 fusion-positive (FP) RMS cell lines with FGFR4 overexpression. Alternative treatment modalities such as combining futibatinib with other kinase inhibitors or targeting FGFR4 with CAR T cells or antibody-drug conjugate may be more effective than the approaches tested in this study.

A stem cell epigenome is associated with primary nonresponse to CD19 CAR T cells in pediatric acute lymphoblastic leukemia.

CD19 chimeric antigen receptor T-cell therapy (CD19-CAR) has changed the treatment landscape and outcomes for patients with pre-B-cell acute lymphoblastic leukemia (B-ALL). Unfortunately, primary nonresponse (PNR), sustained CD19+ disease, and concurrent expansion of CD19-CAR occur in 20% of the patients and is associated with adverse outcomes. Although some failures may be attributable to CD19 loss, mechanisms of CD19-independent, leukemia-intrinsic resistance to CD19-CAR remain poorly understood. We hypothesize that PNR leukemias are distinct compared with primary sensitive (PS) leukemias and that these differences are present before treatment. We used a multiomic approach to investigate this in 14 patients (7 with PNR and 7 with PS) enrolled in the PLAT-02 trial at Seattle Children's Hospital. Long-read PacBio sequencing helped identify 1 PNR in which 47% of CD19 transcripts had exon 2 skipping, but other samples lacked CD19 transcript abnormalities. Epigenetic profiling discovered DNA hypermethylation at genes targeted by polycomb repressive complex 2 (PRC2) in embryonic stem cells. Similarly, assays of transposase-accessible chromatin-sequencing revealed reduced accessibility at these PRC2 target genes, with a gain in accessibility of regions characteristic of hematopoietic stem cells and multilineage progenitors in PNR. Single-cell RNA sequencing and cytometry by time of flight analyses identified leukemic subpopulations expressing multilineage markers and decreased antigen presentation in PNR. We thus describe the association of a stem cell epigenome with primary resistance to CD19-CAR therapy. Future trials incorporating these biomarkers, with the addition of multispecific CAR T cells targeting against leukemic stem cell or myeloid antigens, and/or combined epigenetic therapy to disrupt this distinct stem cell epigenome may improve outcomes of patients with B-ALL.

FGFR4-Targeted Chimeric Antigen Receptors Combined with Anti-Myeloid Polypharmacy Effectively Treat Orthotopic Rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is the most common soft tissue cancer in children. Treatment outcomes, particularly for relapsed/refractory or metastatic disease, have not improved in decades. The current lack of novel therapies and low tumor mutational burden suggest that chimeric antigen receptor (CAR) T-cell therapy could be a promising approach to treating RMS. Previous work identified FGF receptor 4 (FGFR4, CD334) as being specifically upregulated in RMS, making it a candidate target for CAR T cells. We tested the feasibility of an FGFR4-targeted CAR for treating RMS using an NSG mouse with RH30 orthotopic (intramuscular) tumors. The first barrier we noted was that RMS tumors produce a collagen-rich stroma, replete with immunosuppressive myeloid cells, when T-cell therapy is initiated. This stromal response is not seen in tumor-only xenografts. When scFV-based binders were selected from phage display, CARs targeting FGFR4 were not effective until our screening approach was refined to identify binders to the membrane-proximal domain of FGFR4. Having improved the CAR, we devised a pharmacologic strategy to augment CAR T-cell activity by inhibiting the myeloid component of the T-cell-induced tumor stroma. The combined treatment of mice with anti-myeloid polypharmacy (targeting CSF1R, IDO1, iNOS, TGFbeta, PDL1, MIF, and myeloid misdifferentiation) allowed FGFR4 CAR T cells to successfully clear orthotopic RMS tumors, demonstrating that RMS tumors, even with very low copy-number targets, can be targeted by CAR T cells upon reversal of an immunosuppressive microenvironment.

An optimized bicistronic chimeric antigen receptor against GPC2 or CD276 overcomes heterogeneous expression in neuroblastoma.

Chimeric antigen receptor (CAR) T cell therapies targeting single antigens have performed poorly in clinical trials for solid tumors due to heterogenous expression of tumor-associated antigens (TAAs), limited T cell persistence, and T cell exhaustion. Here, we aimed to identify optimal CARs against glypican 2 (GPC2) or CD276 (B7-H3), which were highly but heterogeneously expressed in neuroblastoma (NB), a lethal extracranial solid tumor of childhood. First, we examined CAR T cell expansion in the presence of targets by digital droplet PCR. Next, using pooled competitive optimization of CAR by cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq), termed P-COCC, we simultaneously analyzed protein and transcriptome expression of CAR T cells to identify high-activity CARs. Finally, we performed cytotoxicity assays to identify the most effective CAR against each target and combined the CARs into a bicistronic "OR" CAR (BiCisCAR). BiCisCAR T cells effectively eliminated tumor cells expressing GPC2 or CD276. Furthermore, the BiCisCAR T cells demonstrated prolonged persistence and resistance to exhaustion when compared with CARs targeting a single antigen. This study illustrated that targeting multiple TAAs with BiCisCAR may overcome heterogenous expression of target antigens in solid tumors and identified a potent, clinically relevant CAR against NB. Moreover, our multimodal approach integrating competitive expansion, P-COCC, and cytotoxicity assays is an effective strategy to identify potent CARs among a pool of candidates.

Immunohistochemical detection of PAX-FOXO1 fusion proteins in alveolar rhabdomyosarcoma using breakpoint specific monoclonal antibodies.

Alveolar Rhabdomyosarcoma (ARMS) is an aggressive pediatric cancer with about 80% of cases characterized by either a t(1;13)(p36;q14) or t(2;13)(q35;q14), which results in the formation of the fusion oncogenes PAX7-FOXO1 and PAX3-FOXO1, respectively. Since patients with fusion-positive ARMS (FP-RMS) have a poor prognosis and are treated with an aggressive therapeutic regimen, correct classification is of clinical importance. Detection of the translocation by different molecular methods is used for diagnostics, including fluorescence in situ hybridization and RT-PCR or NGS based approaches. Since these methods are complex and time consuming, we developed specific monoclonal antibodies (mAbs) directed to the junction region on the PAX3-FOXO1 fusion protein. Two mAbs, PFM.1 and PFM.2, were developed and able to immunoprecipitate in vitro-translated PAX3-FOXO1 and cellular PAX3-FOXO1 from FP-RMS cells. Furthermore, the mAbs recognized a 105 kDa band in PAX3-FOXO1-transfected cells and in FP-RMS cell lines. The mAbs did not recognize proteins in fusion-negative embryonal rhabdomyosarcoma cell lines, nor did they recognize PAX3 or FOXO1 alone when compared to anti-PAX3 and anti-FOXO1 antibodies. We next evaluated the ability of mAb PFM.2 to detect the fusion protein by immunohistochemistry. Both PAX3-FOXO1 and PAX7-FOXO1 were detected in HEK293 cells transfected with the corresponding cDNAs. Subsequently, we stained 26 primary tumor sections and a rhabdomyosarcoma tissue array and detected both fusion proteins with a positive predictive value of 100%, negative predictive value of 98%, specificity of 100% and a sensitivity of 91%. While tumors are stained homogenously in PAX3-FOXO1 cases, the staining pattern is heterogenous with scattered positive cells only in tumors expressing PAX7-FOXO1. No staining was observed in stromal cells, embryonal rhabdomyosarcoma, and fusion-negative rhabdomyosarcoma. These results demonstrate that mAbs specific for the chimeric oncoproteins PAX3-FOXO1 and PAX7-FOXO1 can be used efficiently for simple and fast subclassification of rhabdomyosarcoma in routine diagnostics via immunohistochemical detection.

CLPTM1L promotes growth and enhances aneuploidy in pancreatic cancer cells.

Genome-wide association studies (GWAS) of 10 different cancers have identified pleiotropic cancer predisposition loci across a region of chromosome 5p15.33 that includes the TERT and CLPTM1L genes. Of these, susceptibility alleles for pancreatic cancer have mapped to the CLPTM1L gene, thus prompting an investigation of the function of CLPTM1L in the pancreas. Immunofluorescence analysis indicated that CLPTM1L localized to the endoplasmic reticulum where it is likely embedded in the membrane, in accord with multiple predicted transmembrane domains. Overexpression of CLPTM1L enhanced growth of pancreatic cancer cells in vitro (1.3-1.5-fold; PDAY7 < 0.003) and in vivo (3.46-fold; PDAY68 = 0.039), suggesting a role in tumor growth; this effect was abrogated by deletion of two hydrophilic domains. Affinity purification followed by mass spectrometry identified an interaction between CLPTM1L and non-muscle myosin II (NMM-II), a protein involved in maintaining cell shape, migration, and cytokinesis. The two proteins colocalized in the cytoplasm and, after treatment with a DNA-damaging agent, at the centrosomes. Overexpression of CLPTM1L and depletion of NMM-II induced aneuploidy, indicating that CLPTM1L may interfere with normal NMM-II function in regulating cytokinesis. Immunohistochemical analysis revealed enhanced staining of CLPTM1L in human pancreatic ductal adenocarcinoma (n = 378) as compared with normal pancreatic tissue samples (n = 17; P = 1.7 × 10(-4)). Our results suggest that CLPTM1L functions as a growth-promoting gene in the pancreas and that overexpression may lead to an abrogation of normal cytokinesis, indicating that it should be considered as a plausible candidate gene that could explain the effect of pancreatic cancer susceptibility alleles on chr5p15.33.

Targeting wild-type and mutationally activated FGFR4 in rhabdomyosarcoma with the inhibitor ponatinib (AP24534).

Rhabdomyosarcoma (RMS) is the most common childhood soft tissue sarcoma. Despite advances in modern therapy, patients with relapsed or metastatic disease have a very poor clinical prognosis. Fibroblast Growth Factor Receptor 4 (FGFR4) is a cell surface tyrosine kinase receptor that is involved in normal myogenesis and muscle regeneration, but not commonly expressed in differentiated muscle tissues. Amplification and mutational activation of FGFR4 has been reported in RMS and promotes tumor progression. Therefore, FGFR4 is a tractable therapeutic target for patients with RMS. In this study, we used a chimeric Ba/F3 TEL-FGFR4 construct to test five tyrosine kinase inhibitors reported to specifically inhibit FGFRs in the nanomolar range. We found ponatinib (AP24534) to be the most potent FGFR4 inhibitor with an IC50 in the nanomolar range. Ponatinib inhibited the growth of RMS cells expressing wild-type or mutated FGFR4 through increased apoptosis. Phosphorylation of wild-type and mutated FGFR4 as well as its downstream target STAT3 was also suppressed by ponatinib. Finally, ponatinib treatment inhibited tumor growth in a RMS mouse model expressing mutated FGFR4. Therefore, our data suggests that ponatinib is a potentially effective therapeutic agent for RMS tumors that are driven by a dysregulated FGFR4 signaling pathway.

Massively parallel sequencing reveals an accumulation of de novo mutations and an activating mutation of LPAR1 in a patient with metastatic neuroblastoma.

Neuroblastoma is one of the most genomically heterogeneous childhood malignances studied to date, and the molecular events that occur during the course of the disease are not fully understood. Genomic studies in neuroblastoma have showed only a few recurrent mutations and a low somatic mutation burden. However, none of these studies has examined the mutations arising during the course of disease, nor have they systemically examined the expression of mutant genes. Here we performed genomic analyses on tumors taken during a 3.5 years disease course from a neuroblastoma patient (bone marrow biopsy at diagnosis, adrenal primary tumor taken at surgical resection, and a liver metastasis at autopsy). Whole genome sequencing of the index liver metastasis identified 44 non-synonymous somatic mutations in 42 genes (0.85 mutation/MB) and a large hemizygous deletion in the ATRX gene which has been recently reported in neuroblastoma. Of these 45 somatic alterations, 15 were also detected in the primary tumor and bone marrow biopsy, while the other 30 were unique to the index tumor, indicating accumulation of de novo mutations during therapy. Furthermore, transcriptome sequencing on the 3 tumors demonstrated only 3 out of the 15 commonly mutated genes (LPAR1, GATA2, and NUFIP1) had high level of expression of the mutant alleles, suggesting potential oncogenic driver roles of these mutated genes. Among them, the druggable G-protein coupled receptor LPAR1 was highly expressed in all tumors. Cells expressing the LPAR1 R163W mutant demonstrated a significantly increased motility through elevated Rho signaling, but had no effect on growth. Therefore, this study highlights the need for multiple biopsies and sequencing during progression of a cancer and combinatorial DNA and RNA sequencing approach for systematic identification of expressed driver mutations.

Synthetic lethal screen identifies NF-κB as a target for combination therapy with topotecan for patients with neuroblastoma.

BACKGROUND: Despite aggressive multimodal treatments the overall survival of patients with high-risk neuroblastoma remains poor. The aim of this study was to identify novel combination chemotherapy to improve survival rate in patients with high-risk neuroblastoma. METHODS: We took a synthetic lethal approach using a siRNA library targeting 418 apoptosis-related genes and identified genes and pathways whose inhibition synergized with topotecan. Microarray analyses of cells treated with topotecan were performed to identify if the same genes or pathways were altered by the drug. An inhibitor of this pathway was used in combination with topotecan to confirm synergism by in vitro and in vivo studies. RESULTS: We found that there were nine genes whose suppression synergized with topotecan to enhance cell death, and the NF-κB signaling pathway was significantly enriched. Microarray analysis of cells treated with topotecan revealed a significant enrichment of NF-κB target genes among the differentially altered genes, suggesting that NF-κB pathway was activated in the treated cells. Combination of topotecan and known NF-κB inhibitors (NSC 676914 or bortezomib) significantly reduced cell growth and induced caspase 3 activity in vitro. Furthermore, in a neuroblastoma xenograft mouse model, combined treatment of topotecan and bortezomib significantly delayed tumor formation compared to single-drug treatments. CONCLUSIONS: Synthetic lethal screening provides a rational approach for selecting drugs for use in combination therapy and warrants clinical evaluation of the efficacy of the combination of topotecan and bortezomib or other NF-κB inhibitors in patients with high risk neuroblastoma.

Systematic proteome analysis identifies transcription factor YY1 as a direct target of miR-34a.

MicroRNA 34a (miR-34a) is a potential tumor suppressor gene and has been identified as a miRNA component of the p53 network. To better understand the biological pathways involved in miR-34a action, a parallel global protein and mRNA expression profiling on miR-34a treated neuroblastoma cells (IMR32) was performed using isotope-coded affinity tags (ICAT) and Affymetrix U133plus2 microarray, respectively. Global profiling showed that miR-34a causes much smaller mRNA expression changes compared to changes at the protein level. A total of 1495 proteins represented by two or more peptides were identified from the quantitative ICAT analysis, of which 143 and 192 proteins are significantly up- or down-regulated by miR-34a, respectively. Pathway analysis of these differentially expressed proteins showed the enrichment of apoptosis and cell death processes in up-regulated proteins but DNA replication and cell cycle processes in the down-regulated proteins. Ribosomal proteins are the most significant set down-regulated by miR-34a. Additionally, biological network analysis to identify direct interactions among the differentially expressed proteins demonstrated that the expression of the ubiquitous transcription factor YY1, as well as its downstream proteins, is significantly reduced by miR-34a. We further demonstrated that miR-34a directly targets YY1 through a miR-34a-binding site within the 3' UTR of YY1 using a luciferase reporter system. YY1 is a negative regulator of p53, and it plays an essential role in cancer biology. Therefore, YY1 is another important direct target of miR-34a which closely regulates TP53 activities.

Screening a panel of drugs with diverse mechanisms of action yields potential therapeutic agents against neuroblastoma.

Neuroblastoma (NB) is the most common extracranial solid tumor in children. Despite current aggressive therapy, the survival rate for high risk NB remains less than 40%. To identify novel effective chemo-agents against NB, we screened a panel of 96 drugs against two NB cell lines, SK-N-AS and SH-SY5Y. We found 30 compounds that were active against NB cell lines at < or =10 microM concentration. More interestingly, 17 compounds are active at < or =1 microM concentration, and they act through a wide spectrum of diverse mechanisms such as mitotic inhibition, topoisomerase inhibition, targeting various biological pathways, and unknown mechanisms. The majority of these active compounds also induced caspase 3/7 by more than 2-fold. Of these 17 active compounds against NB cell lines at sub-micromolar concentration, eleven compounds are not currently used to treat NB. Among them, nine are FDA approved compounds, and three agents are undergoing clinical trials for various malignancies. Furthermore, we identified four agents active against these NB cell lines that have not yet been tested in the clinical setting. Finally we demonstrated that Cucurbitacin I inhibits neuroblastoma cell growth through inhibition of STAT3 pathway. These drugs thus represent potential novel therapeutic agents for patients with NB, and further validation studies are needed to translate them to the clinic.

Identification of FGFR4-activating mutations in human rhabdomyosarcomas that promote metastasis in xenotransplanted models.

Rhabdomyosarcoma (RMS) is a childhood cancer originating from skeletal muscle, and patient survival is poor in the presence of metastatic disease. Few determinants that regulate metastasis development have been identified. The receptor tyrosine kinase FGFR4 is highly expressed in RMS tissue, suggesting a role in tumorigenesis, although its functional importance has not been defined. Here, we report the identification of mutations in FGFR4 in human RMS tumors that lead to its activation and present evidence that it functions as an oncogene in RMS. Higher FGFR4 expression in RMS tumors was associated with advanced-stage cancer and poor survival, while FGFR4 knockdown in a human RMS cell line reduced tumor growth and experimental lung metastases when the cells were transplanted into mice. Moreover, 6 FGFR4 tyrosine kinase domain mutations were found among 7 of 94 (7.5%) primary human RMS tumors. The mutants K535 and E550 increased autophosphorylation, Stat3 signaling, tumor proliferation, and metastatic potential when expressed in a murine RMS cell line. These mutants also transformed NIH 3T3 cells and led to an enhanced metastatic phenotype. Finally, murine RMS cell lines expressing the K535 and E550 FGFR4 mutants were substantially more susceptible to apoptosis in the presence of a pharmacologic FGFR inhibitor than the control cell lines expressing the empty vector or wild-type FGFR4. Together, our results demonstrate that mutationally activated FGFR4 acts as an oncogene, and these are what we believe to be the first known mutations in a receptor tyrosine kinase in RMS. These findings support the potential therapeutic targeting of FGFR4 in RMS.

microRNA profiling identifies cancer-specific and prognostic signatures in pediatric malignancies.

PURPOSE: microRNAs have been shown to be involved in different human cancers. We therefore have performed expression profiles on a panel of pediatric tumors to identify cancer-specific microRNAs. We also investigated if microRNAs are coregulated with their host gene. EXPERIMENTAL DESIGN: We performed parallel microRNAs and mRNA expression profiling on 57 tumor xenografts and cell lines representing 10 different pediatric solid tumors using microarrays. For those microRNAs that map to their host mRNA, we calculated correlations between them. RESULTS: We found that the majority of cancer types clustered together based on their global microRNA expression profiles by unsupervised hierarchical clustering. Fourteen microRNAs were significantly differentially expressed between rhabdomyosarcoma and neuroblastoma, and 8 of them were validated in independent patient tumor samples. Exploration of the expression of microRNAs in relationship with their host genes showed that the expression for 43 of 68 (63%) microRNAs located inside known coding genes was significantly correlated with that of their host genes. Among these 43 microRNAs, 5 of 7 microRNAs in the OncomiR-1 cluster correlated significantly with their host gene MIRHG1 (P < 0.01). In addition, high expression of MIRHG1 was significantly associated with high stage and MYCN amplification in neuroblastoma tumors, and the expression level of MIRHG1 could predict the outcome of neuroblastoma patients independently from the current neuroblastoma risk-stratification in two independent patient cohorts. CONCLUSION: Pediatric cancers express cancer-specific microRNAs. The high expression of the OncomiR-1 host gene MIRHG1 correlates with poor outcome for patients with neuroblastoma, indicating important oncogenic functions of this microRNA cluster in neuroblastoma biology.

Anti-tumor immunity in a model of acute myeloid leukemia.

Whole-cell vaccines allow the induction of anti-tumor immune responses without the need to define tumor antigens. We wished to directly compare, for the first time, the capacity of B7-1, B7-2 and 4-1BB ligand (4-1BBL) costimulatory molecules to convert murine and human acute myeloid leukemia (AML) cells into whole vaccines. 32Dc-kit is a murine myeloid cell line, which develops an AML-like disease over a protracted period, emulating human AML disease development. 32Dc-kit cells were modified to express elevated levels of B7-1, B7-2 or 4-1BBL, and each led to tumor rejection, although only mice injected with 32Dc-kit/B7-2 cells were able to reject subsequent parental tumor cell challenge. T-cell deficient nude mice were able to reject the 32Dc-kit variants, but they could not reject parental cell challenge; however, we found no evidence of cytotoxic T lymphocyte or natural killer (NK) activity ex vivo suggesting that tumor cell killing was mediated by an immune response that could not be recapitulated using purified NK or T cells as lone effectors. In human allogeneic mixed lymphocyte reactions (MLRs), we found no single costimulatory molecule was more effective, suggesting that the induction of a universal anti-tumor response will require a combination of costimulatory molecules.

Human neuroblastoma cells rapidly enter cell cycle arrest and apoptosis following exposure to C-28 derivatives of the synthetic triterpenoid CDDO.

Synthetic triterpenoids, such as 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) and its derivatives, are an extremely potent class of new anti-cancer therapeutic agents, characterized by high anti-tumor potency and low toxicity to normal tissues. This report is the first to investigate the effects of C-28 derivatives of CDDO on 22 pediatric solid tumor cell lines, including neuroblastoma, rhabdomyosarcoma, osteosarcoma, and Ewing's sarcoma. We determined IC(50)s in the range of 5-170 nM for inhibition of colony formation and DNA synthesis, and 110-630 nM for metabolic cell death and decrease in cell number, using the C-28 CDDO analogs, CDDO methyl ester (CDDO-Me), CDDO imidazolide (CDDO-Im), CDDO ethyl amide (CDDO-EA), CDDO trifluoroethyl amide (CDDO-TFEA), and CDDO diethylamide (CDDO-DE). After treatment of human neuroblastoma cells with CDDO-Me, cell cycle studies show depletion of the S-phase, while apoptosis studies show conformational activation and mitochondrial translocation of Bax protein, as well as activation of caspases -3 and -8. These data demonstrate the potential utility of CDDO analogs as promising novel therapeutic agents for high-risk pediatric solid tumors.

Immunotherapy of acute myeloid leukaemia: development of a whole cell vaccine.

Acute myeloid leukaemia (AML) is a difficult to treat disease and strategies, such as immunotherapy, which have the potential to eliminate residual tumour cells at first remission are required to reduce the incidence of relapse with its high associated mortality rates. T cells play an important role in tumor immunity and two signals are traditionally thought to be required to activate naive T cells; signal one through the major histocompatibility:antigen:T-cell receptor complex and signal two through costimulation. Many tumor associated antigens have been identified in AML suggesting it may be possible to target the immune system of AML patients; however AML develops due to tumour and immune editing, two systems by which AML cells can escape immune surveillance. By genetically modifying AML cells to express costimulatory molecules and/or cytokines, it has been possible to transform AML cells into antigen presenting cells and this has the potential to re-activate the immune system in patients. Here we summarize the rationale for using a whole cell vaccine approach to treat AML, and discuss current progress in the field of whole cell vaccine development against AML.

Development of a whole cell vaccine for acute myeloid leukaemia.

We describe the modification of tumour cells to enhance their capacity to act as antigen presenting cells with particular focus on the use of costimulatory molecules to do so. We have been involved in the genetic modification of tumour cells to prepare a whole cell vaccine for nearly a decade and we have a particular interest in acute myeloid leukaemia (AML). AML is an aggressive and difficult to treat disease, especially, for patients for whom haematopoietic stem cell (HSC) transplant is not an option. AML patients who have a suitable donor and meet HSC transplant fitness requirements, have a 5-year survival of 50%; however, for patients with no suitable donor or for who age is a factor, the prognosis is much worse. It is particularly poor prognosis patients, who are not eligible for HSC transplant, who are likely to benefit most from immunotherapy. It would be hoped that immunotherapy would be used to clear residual tumour cells in these patients in the first remission following standard chemotherapy treatments and this will extend the remission and reduce the risk of a second relapse associated with disease progression and poor mortality rates. In this symposia report, we will focus on whole cell vaccines as an immunotherapeutic option with particular reference to their use in the treatment of AML. We will aim to provide a brief overview of the latest data from our group and considerations for the use of this treatment modality in clinical trials for AML.