Optimized human CYP4B1 in combination with the alkylator prodrug 4-ipomeanol serves as a novel suicide gene system for adoptive T-cell therapies

There and Back Again: A Perspective on 20 Years of CYP4Z1

Cytochrome P450 (CYP)4Z1, a highly expressed CYP gene in breast cancer, was one of the last CYPs to be identified in the human genome, some 20 years ago. CYP4 enzymes typically catalyze ω-hydroxylation and metabolize ω3 and ω6 polyunsaturated fatty acids to bioactive lipid metabolites that can influence tumor growth and metastasis. These attributes of CYP4Z1 make it an attractive target for new chemotherapeutic drug design, as a potential biomarker for selection of patients that might respond favorably to drugs and for developing enzyme inhibitors as potential therapeutic agents. This review summarizes the current state of knowledge regarding the advancing biochemistry of CYP4Z1, its role in breast cancer, and the recent synthesis of selective chemical inhibitors of the enzyme. We identify gaps that need to be filled to further advance this field and present new experimental data on recombinant CYP4Z1 expression and purification of the active catalytic form. SIGNIFICANCE STATEMENT: In breast cancer, an unmet need is the availability of highly effective therapeutic agents, especially for triple negative breast cancer. The relevance of the work summarized in this mini-review is that it identifies a new potential drug target, CYP4Z1, and discusses ways in which the gene product's catalytic activity might be modulated in order to combat this malignancy and limit its spread.

Dietary factors and their influence on immunotherapy strategies in oncology: a comprehensive review

Immunotherapy is emerging as a promising avenue in oncology, gaining increasing importance and offering substantial advantages when compared to chemotherapy or radiotherapy. However, in the context of immunotherapy, there is the potential for the immune system to either support or hinder the administered treatment. This review encompasses recent and pivotal studies that assess the influence of dietary elements, including vitamins, fatty acids, nutrients, small dietary molecules, dietary patterns, and caloric restriction, on the ability to modulate immune responses. Furthermore, the article underscores how these dietary factors have the potential to modify and enhance the effectiveness of anticancer immunotherapy. It emphasizes the necessity for additional research to comprehend the underlying mechanisms for optimizing the efficacy of anticancer therapy and defining dietary strategies that may reduce cancer-related morbidity and mortality. Persistent investigation in this field holds significant promise for improving cancer treatment outcomes and maximizing the benefits of immunotherapy.

Spotlight on CYP4B1

The mammalian cytochrome P450 monooxygenase CYP4B1 can bioactivate a wide range of xenobiotics, such as its defining/hallmark substrate 4-ipomeanol leading to tissue-specific toxicities. Similar to other members of the CYP4 family, CYP4B1 has the ability to hydroxylate fatty acids and fatty alcohols. Structural insights into the enigmatic role of CYP4B1 with functions in both, xenobiotic and endobiotic metabolism, as well as its unusual heme-binding characteristics are now possible by the recently solved crystal structures of native rabbit CYP4B1 and the p.E310A variant. Importantly, CYP4B1 does not play a major role in hepatic P450-catalyzed phase I drug metabolism due to its predominant extra-hepatic expression, mainly in the lung. In addition, no catalytic activity of human CYP4B1 has been observed owing to a unique substitution of an evolutionary strongly conserved proline 427 to serine. Nevertheless, association of CYP4B1 expression patterns with various cancers and potential roles in cancer development have been reported for the human enzyme. This review will summarize the current status of CYP4B1 research with a spotlight on its roles in the metabolism of endogenous and exogenous compounds, structural properties, and cancer association, as well as its potential application in suicide gene approaches for targeted cancer therapy.

Advances in the Pharmacological Activities and Effects of Perilla Ketone and Isoegomaketone

As components of a traditional Chinese herbal medicine with many physiological activities, perilla ketone and isoegomaketone isolated from perilla essential oil are important active components of Perilla frutescens. Recent studies have shown that these two compounds have promising antitumor, antifungal, antirheumatoid arthritis, antiobesity, anti-inflammatory, healing-promoting, and other activities and can be used to combat toxicity from immunotherapy. Therefore, the multitude of pharmacological activities and effects demonstrate the broad research potential of perilla ketone and isoegomaketone. However, no reviews have been published related to the pharmacological activities or effects of perilla ketone and isoegomaketone. The purpose of this review is as follows: (1) outline the recent advances made in understanding the pharmacological activities of perilla ketone and isoegomaketone; (2) summarize their effects; and (3) discuss future research perspectives.

Potential of cytochrome P450, a family of xenobiotic metabolizing enzymes, in cancer therapy

SIGNIFICANCE

Targeted cancer therapy with minimal off-target consequences has shown promise for some cancer types. Although cytochrome P450 (CYP) consists of 18 families, CYP1-4 families play key role in metabolizing xenobiotics and cancer drugs. This eventually affects the process of carcinogenesis, treatment outcome, and cancer drug resistance. Differential overexpression of CYPs in transformed cells, together with phenotypic alterations in tumors, presents a potential for therapeutic intervention.

RECENT ADVANCES

Recent advances in molecular tools and information technology have helped utilize CYPs as cancer targets. The precise expression in various tumors, X-ray crystal structures, improved understanding of the structure-activity relationship, and new approaches in the development of prodrugs have supported the ongoing efforts to develop CYPs-based drugs with a better therapeutic index.

CRITICAL ISSUES

Narrow therapeutic index, off-target effects, drug resistance, and tumor heterogeneity limit the benefits of CYP-based conventional cancer therapies. In this review, we address the CYP1-4 families as druggable targets in cancer. An emphasis is given to the CYP expression, function, and the possible mechanisms that drive expression and activity in normal and transformed tissues. The strategies that inhibit or activate CYPs for therapeutic benefits are also discussed.

FUTURE DIRECTIONS

Efforts are needed to develop more selective tools that will help comprehend molecular and metabolic alterations in tumor tissues with biological end-points in relation to CYPs. This will eventually translate to developing more specific CYP inhibitors/inducers.

Optimized NGFR-derived hinges for rapid and efficient enrichment and detection of CAR T cells in vitro and in vivo

Chimeric antigen receptor (CAR) T cell therapy has demonstrated unprecedented success with high remission rates for heavily pretreated patients with hematological malignancies. The hinge connecting the extracellular antigen recognition unit to the transmembrane domain provides the length and flexibility of the CAR constructs and ensures that the CAR can reach the target antigen and mediate recognition and killing of target cells. The hinge can also include specific amino acid sequences to improve CAR expression, influence T cell proliferation, and facilitate CAR T cell detection, enrichment, and even elimination. Here, we report the generation of two novel hinge domains derived from the low-affinity p75 chain of the human nerve growth factor receptor (NGFR), termed N3 and N4, which, when incorporated into the CAR backbone, allow detection as well as high-grade enrichment of CAR T cells with GMP-compatible immunomagnetic reagents. After optimizing the MACS protocol for excellent CAR T cell purity and yield, we demonstrated that N3- and N4-hinged CAR T cells are as efficacious as their CD8-hinged counterparts in vitro against hematological blasts and also in vivo in the control of acute monocytic leukemia in an immunodeficient mouse xenograft model. Thus, both hinges could potentially be an integral part of future CAR designs and universally applicable in clinical applications.

Genetic Engineering and Enrichment of Human NK Cells for CAR-Enhanced Immunotherapy of Hematological Malignancies

The great clinical success of chimeric antigen receptor (CAR) T cells has unlocked new levels of immunotherapy for hematological malignancies. Genetically modifying natural killer (NK) cells as alternative CAR immune effector cells is also highly promising, as NK cells can be transplanted across HLA barriers without causing graft-versus-host disease. Therefore, off-the-shelf usage of CAR NK cell products might allow to widely expand the clinical indications and to limit the costs of treatment per patient. However, in contrast to T cells, manufacturing suitable CAR NK cell products is challenging, as standard techniques for genetically engineering NK cells are still being defined. In this study, we have established optimal lentiviral transduction of primary human NK cells by systematically testing different internal promoters for lentiviral CAR vectors and comparing lentiviral pseudotypes and viral entry enhancers. We have additionally modified CAR constructs recognizing standard target antigens for acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) therapy—CD19, CD33, and CD123—to harbor a CD34-derived hinge region that allows efficient detection of transduced NK cells in vitro and in vivo and also facilitates CD34 microbead-assisted selection of CAR NK cell products to >95% purity for potential clinical usage. Importantly, as most leukemic blasts are a priori immunogenic for activated primary human NK cells, we developed an in vitro system that blocks the activating receptors NKG2D, DNAM-1, NKp30, NKp44, NKp46, and NKp80 on these cells and therefore allows systematic testing of the specific killing of CAR NK cells against ALL and AML cell lines and primary AML blasts. Finally, we evaluated in an ALL xenotransplantation model in NOD/SCID-gamma (NSG) mice whether human CD19 CAR NK cells directed against the CD19+ blasts are relying on soluble or membrane-bound IL15 production for NK cell persistence and also in vivo leukemia control. Hence, our study provides important insights into the generation of pure and highly active allogeneic CAR NK cells, thereby advancing adoptive cellular immunotherapy with CAR NK cells for human malignancies further.

A novel CD34-derived hinge for rapid and efficient detection and enrichment of CAR T cells

Immunotherapy including chimeric antigen receptor (CAR) T cell therapy has revolutionized modern cancer therapy and has achieved remarkable remission and survival rates for several malignancies with historically dismal outcomes. The hinge of the CAR connects the antigen binding to the transmembrane domain and can be exploited to confer features to CAR T cells including additional stimulation, targeted elimination or detection and enrichment of the genetically modified cells. For establishing a novel hinge derived from human CD34, we systematically tested CD34 fragments of different lengths, all containing the binding site of the QBend-10 monoclonal antibody, in a FMC63-based CD19 CAR lentiviral construct. A final construct of 99 amino acids called C6 proved to be the best candidate for flow cytometry-based detection of CAR T cells and >95% enrichment of genetically modified T cells on MACS columns. The C6 hinge was functionally indistinguishable from the commonly used CD8α hinge in vitro as well as in in vivo experiments in NSG mice. We also showed that the C6 hinge can be used for a variety of different CARs and mediates high killing efficacy without unspecific activation by target antigen-negative cells, thus making C6 ideally suited as a universal hinge for CARs for clinical applications.

Epigenetic Priming of Bladder Cancer Cells With Decitabine Increases Cytotoxicity of Human EGFR and CD44v6 CAR Engineered T-Cells

Background

Treatment of B-cell malignancies with CD19-directed chimeric antigen receptor (CAR) T-cells marked a new era in immunotherapy, which yet has to be successfully adopted to solid cancers. Epigenetic inhibitors of DNA methyltransferases (DNMTi) and histone deacetylases (HDACi) can induce broad changes in gene expression of malignant cells, thus making these inhibitors interesting combination partners for immunotherapeutic approaches.

Methods

Urothelial carcinoma cell lines (UCC) and benign uroepithelial HBLAK cells pretreated with the DNMTi decitabine or the HDACi romidepsin were co-incubated with CAR T-cells directed against EGFR or CD44v6, and subsequent cytotoxicity assays were performed. Effects on T-cell cytotoxicity and surface antigen expression on UCC were determined by flow cytometry. We also performed next-generation mRNA sequencing of inhibitor-treated UCC and siRNA-mediated knockdown of potential regulators of CAR T-cell killing.

Results

Exposure to decitabine but not romidepsin enhanced CAR T-cell cytotoxicity towards all UCC lines, but not towards the benign HBLAK cells. Increased killing could neither be attributed to enhanced target antigen expression (EGFR and CD44v6) nor fully explained by changes in the T-cell ligands PD-L1, PD-L2, ICAM-1, or CD95. Instead, gene expression analysis suggested that regulators of cell survival and apoptosis were differentially induced by the treatment. Decitabine altered the balance between survival and apoptosis factors towards an apoptosis-sensitive state associated with increased CAR T-cell killing, while romidepsin, at least partially, tilted this balance in the opposite direction. Knockdown experiments with siRNA in UCC confirmed BID and BCL2L1/BCLX as two key factors for the altered susceptibility of the UCC.

Conclusion

Our data suggest that the combination of decitabine with CAR T-cell therapy is an attractive novel therapeutic approach to enhance tumor-specific killing of bladder cancer. Since BID and BCL2L1 are essential determinants for the susceptibility of a wide variety of malignant cells, their targeting might be additionally suitable for combination with immunotherapies, e.g., CAR T-cells or checkpoint inhibitors in other malignancies.

Making Potent CAR T Cells Using Genetic Engineering and Synergistic Agents

Immunotherapies are emerging as powerful weapons for the treatment of malignancies. Chimeric antigen receptor (CAR)-engineered T cells have shown dramatic clinical results in patients with hematological malignancies. However, it is still challenging for CAR T cell therapy to be successful in several types of blood cancer and most solid tumors. Many attempts have been made to enhance the efficacy of CAR T cell therapy by modifying the CAR construct using combination agents, such as compounds, antibodies, or radiation. At present, technology to improve CAR T cell therapy is rapidly developing. In this review, we particularly emphasize the most recent studies utilizing genetic engineering and synergistic agents to improve CAR T cell therapy.

CD44v6-targeted CAR T-cells specifically eliminate CD44 isoform 6 expressing head/neck squamous cell carcinoma cells

Immune checkpoint blockade can cause regression of recurrent and/or refractory head and neck squamous cell carcinoma (HNSCC). As a second type of immunotherapy, adoptive cellular therapy with genetically modified patient's T-cells redirected against the autologous malignant cells by expressing chimeric antigen receptors (CARs) recognizing tumor-associated antigens has been established as highly efficient personalized treatment for hematological malignancies. In solid cancers however, the application of these genetically modified immune effector cells still lacks equal response rates. CD44v6 is an isoform of the hyaluronic receptor CD44 that is almost exclusively expressed at high levels on solid cancers and has been associated with tumorigenesis, tumor cell invasion and metastasis. Here, we established a highly specific CAR against CD44v6 on HNSCC cells that can be expressed on normal T-cells with lentiviral vectors. Using primary human HNSCC cells in combination with CRISPR/Cas9 and overexpression approaches allowed us to confirm the high specificity of our CAR construct for the tumor-associated CD44v6 as target antigen and to demonstrate a direct correlation between CD44v6 expression levels and cytotoxicity of the CAR T-cells. Importantly, the design of our clinically applicable lentiviral vector facilitates to co-express a second transgene for in vivo control of CAR T-cells, if undesired side-effects or toxicities occur.

Human Family 1-4 cytochrome P450 enzymes involved in the metabolic activation of xenobiotic and physiological chemicals: an update

This is an overview of the metabolic activation of drugs, natural products, physiological compounds, and general chemicals by the catalytic activity of cytochrome P450 enzymes belonging to Families 1-4. The data were collected from > 5152 references. The total number of data entries of reactions catalyzed by P450s Families 1-4 was 7696 of which 1121 (~ 15%) were defined as bioactivation reactions of different degrees. The data were divided into groups of General Chemicals, Drugs, Natural Products, and Physiological Compounds, presented in tabular form. The metabolism and bioactivation of selected examples of each group are discussed. In most of the cases, the metabolites are directly toxic chemicals reacting with cell macromolecules, but in some cases the metabolites formed are not direct toxicants but participate as substrates in succeeding metabolic reactions (e.g., conjugation reactions), the products of which are final toxicants. We identified a high level of activation for three groups of compounds (General Chemicals, Drugs, and Natural Products) yielding activated metabolites and the generally low participation of Physiological Compounds in bioactivation reactions. In the group of General Chemicals, P450 enzymes 1A1, 1A2, and 1B1 dominate in the formation of activated metabolites. Drugs are mostly activated by the enzyme P450 3A4, and Natural Products by P450s 1A2, 2E1, and 3A4. Physiological Compounds showed no clearly dominant enzyme, but the highest numbers of activations are attributed to P450 1A, 1B1, and 3A enzymes. The results thus show, perhaps not surprisingly, that Physiological Compounds are infrequent substrates in bioactivation reactions catalyzed by P450 enzyme Families 1-4, with the exception of estrogens and arachidonic acid. The results thus provide information on the enzymes that activate specific groups of chemicals to toxic metabolites.

VEGFR2 as a target for CAR T cell therapy of Ewing sarcoma

BACKGROUND

T cells engineered to express chimeric antigen receptors (CARs) are a novel modality to treat refractory cancers. The development of CAR T cells against Ewing sarcoma (EwS) is limited by a lack of targetable surface antigens. We investigated vascular endothelial growth factor receptor 2 (VEGFR2) expressed on tumor-associated blood vessels as potential CAR target in this cancer.

METHODS

Expression of VEGFR2 was studied by immunohistochemistry in human EwS biopsies and in murine xenografts and by flow cytometry in EwS cell lines. CARs with short, medium, and long hinge domains against either human or murine VEGFR2 were generated and expressed in human T cells by retroviral gene transfer. The capacity of the individual CARs to activate T cells in response to VEGFR2-expressing cells was compared in vitro.

RESULTS

Tumor-associated endothelial cells in human EwS biopsies and in xenografts expressed VEGFR2. Tumor cells in the majority of EwS biopsies were also VEGFR2-positive. Following modification with anti-mouse or anti-human VEGFR2-specific CAR genes, T cells specifically lysed VEGFR2-expressing target cells of the respective species. CAR T cells with short-length or medium-length hinge domains were functionally superior over those with the long hinge region by in vitro parameters, including antigen-specific degranulation responses, lysis of tumor spheroids, tumor necrosis factor α secretion, sequential killing, and proliferation.

CONCLUSIONS

VEGFR2 is consistently expressed on endothelial cells of the tumor stroma in EwS and thus is a candidate target for CAR T cells in this cancer. Among various VEGFR2-specific CARs, a construct with a short hinge domain was chosen to be further developed toward clinical translation.

Novel advances in biotransformation and bioactivation research-2019 year in review

Biotransformation is one of the main mechanisms used by the body to eliminate drugs. As drug molecules become more complicated, the involvement of drug metabolizing enzymes increases beyond those that are typically studied, such as the cytochrome P450 enzymes. In this review, we try to capture the many outstanding articles that were published in the past year in the field of biotransformation (see Table 1). We have divided the articles into two categories of (1) metabolites and drug metabolizing enzymes, and (2) bioactivation and safety.  This annual review is the fifth of its kind since 2016 (Baillie et al. 2016; Khojasteh et al. 2017, 2018, 2019). This effort in itself also continues to evolve. We have followed the same format we used in previous years in terms of the selection of articles and the authoring of each section. I am pleased of the continued support of Rietjens, Miller, Zhang, Driscoll and Mitra to this review. We would like to welcome Klarissa D. Jackson as a new author for this year's issue. We strive to maintain a balance of authors from academic and industry settings.  We would be pleased to hear your opinions of our commentary, and we extend an invitation to anyone who would like to contribute to a future edition of this review. Cyrus Khojasteh, on behalf of the authors.

Heterologous Expression and Functional Characterization of Novel CYP2C9 Variants Identified in the Alaska Native People

CYP2C9 is a major form of human liver cytochrome P450 that is responsible for the oxidative metabolism of several widely used low-therapeutic index drugs, including (S)-warfarin and phenytoin. In a cohort of Alaska Native people, ultrarare or novel CYP2C9 protein variants, M1L (rs114071557), N218I (rs780801862), and P279T (rs182132442, CYP2C9*29), are expressed with higher frequencies than the well characterized CYP2C9*2 and CYP2C9*3 alleles. We report here on their relative expression in lentivirus-infected HepG2 cells and the functional characterization of purified reconstituted enzyme variants expressed in Escherichia coli toward (S)-warfarin, phenytoin, flurbiprofen, and (S)-naproxen. In the infected HepG2 cells, robust mRNA and protein expression were obtained for wild-type, N218I, and P279T variants, but as expected, the M1L variant protein was not translated in this liver-derived cell line. His-tagged wild-type protein and the N218I and P279T variants, but not M1L, expressed well in E. coli and were highly purified after affinity chromatography. Upon reconstitution with cytochrome P450 oxidoreductase and cytochrome b5, the N218I and P279T protein variants metabolized (S)-warfarin, phenytoin, flurbiprofen, and (S)-naproxen to the expected monohydroxylated or O-demethylated metabolites. Steady-state kinetic analyses revealed that the relative catalytic efficiency ratios of (S)-warfarin metabolism by the P279T and N218I variants were 87% and 24%, respectively, of wild-type CYP2C9 protein. A similar rank ordering was observed for metabolism of phenytoin, flurbiprofen, and (S)-naproxen. We conclude that carriers of the variant N218I and, especially, the M1L alleles would be at risk of exacerbated therapeutic effects from drugs that rely on CYP2C9 for their metabolic clearance. SIGNIFICANCE STATEMENT: Novel gene variants of CYP2C9-M1L, and N218I, along with P279T (CYP2C9*29)-are expressed in Alaska Native people at relatively high frequencies. In vitro characterization of their functional effects revealed that each variant confers reduced catalytic efficiency toward several substrates, including the low-therapeutic index drugs (S)-warfarin and phenytoin. These data provide the first functional information for new, common CYP2C9 variants in this understudied population. The data may help guide dose adjustments in allele carriers, thus mitigating potential healthcare disparities.

Cytochrome P450 4B1 (CYP4B1) as a target in cancer treatment

Cytochrome P450 4B1 (CYP4B1) plays crucial roles in biotransforming of xenobiotics. Its predominant extrahepatic expression has been associated with certain tissue-specific toxicities. However, the expressions of CYP4B1 in various cancers and hence their potential roles in cancer development were inclusive. In this work, existing knowledge on expression and regulation of CYP4B1 gene and protein, catalysis of CYP4B1, association of CYP4B1 with cancers, contradicting findings about human CYP4B1 activities as well as the employing CYP4B1 in suicide gene approach for cancer treatment were reviewed. To date, it appears that there is a wide spectrum of tissue distribution of CYP4B1 with lungs as the predominant sites. Several nuclear receptors are possibly responsible for regulating its gene expression. The involvement of CYP4B1 in cancer was considered via activation of procarcinogens and neovascularization. However, human CYP4B1 was found to be inactive due to a substitution of proline with serine at position 427. Suicide gene approach combining reengineered CYP4B1 and prodrug 4-ipomeanol (4-IPO) has shown a promising potential for targeted cancer therapy. Further studies should focus on the verification of human CYP4B1 catalytic activities. More compounds with similar structure as 4-IPO should be tested to identify more alternative agents for the suicide gene approach in cancer treatment.

Novel insights into oxidation of fatty acids and fatty alcohols by cytochrome P450 monooxygenase CYP4B1

CYP4B1 is an enigmatic mammalian cytochrome P450 monooxygenase acting at the interface between xenobiotic and endobiotic metabolism. A prominent CYP4B1 substrate is the furan pro-toxin 4-ipomeanol (IPO). Our recent investigation on metabolism of IPO related compounds that maintain the furan functionality of IPO while replacing its alcohol group with alkyl chains of varying structure and length revealed that, in addition to cytotoxic reactive metabolite formation (resulting from furan activation) non-cytotoxic ω-hydroxylation at the alkyl chain can also occur. We hypothesized that substrate reorientations may happen in the active site of CYP4B1. These findings prompted us to re-investigate oxidation of unsaturated fatty acids and fatty alcohols with C9-C16 carbon chain length by CYP4B1. Strikingly, we found that besides the previously reported ω- and ω-1-hydroxylations, CYP4B1 is also capable of α-, β-, γ-, and δ-fatty acid hydroxylation. In contrast, fatty alcohols of the same chain length are exclusively hydroxylated at ω, ω-1, and ω-2 positions. Docking results for the corresponding CYP4B1-substrate complexes revealed that fatty acids can adopt U-shaped bonding conformations, such that carbon atoms in both arms may approach the heme-iron. Quantum chemical estimates of activation energies of the hydrogen radical abstraction by the reactive compound 1 as well as electron densities of the substrate orbitals led to the conclusion that fatty acid and fatty alcohol oxidations by CYP4B1 are kinetically controlled reactions.

Deficiency of the Fanconi anemia E2 ubiqitin conjugase UBE2T only partially abrogates Alu-mediated recombination in a new model of homology dependent recombination

The primary function of the UBE2T ubiquitin conjugase is in the monoubiquitination of the FANCI-FANCD2 heterodimer, a central step in the Fanconi anemia (FA) pathway. Genetic inactivation of UBE2T is responsible for the phenotypes of FANCT patients; however, a FANCT patient carrying a maternal duplication and a paternal deletion in the UBE2T loci displayed normal peripheral blood counts and UBE2T protein levels in B-lymphoblast cell lines. To test whether reversion by recombination between UBE2T AluYa5 elements could have occurred in the patient's hematopoietic stem cells despite the defects in homologous recombination (HR) in FA cells, we constructed HeLa cell lines containing the UBE2T AluYa5 elements and neighboring intervening sequences flanked by fluorescent reporter genes. Introduction of a DNA double strand break in the model UBE2T locus in vivo promoted single strand annealing (SSA) between proximal Alu elements and deletion of the intervening color marker gene, recapitulating the reversion of the UBE2T duplication in the FA patient. To test whether UBE2T null cells retain HR activity, the UBE2T genes were knocked out in HeLa cells and U2OS cells. CRISPR/Cas9-mediated genetic knockout of UBE2T only partially reduced HR, demonstrating that UBE2T-independent pathways can compensate for the recombination defect in UBE2T/FANCT null cells.

Carbohydrate Targets for CAR T Cells in Solid Childhood Cancers

Application of the CAR targeting strategy in solid tumors is challenged by the need for adequate target antigens. As a consequence of their tissue origin, embryonal cancers can aberrantly express membrane-anchored gangliosides. These are carbohydrate molecules consisting of a glycosphingolipid linked to sialic acids residues. The best-known example is the abundant expression of ganglioside G_D2 on the cell surface of neuroblastomas which derive from G_D2-positive neuroectoderm. Gangliosides are involved in various cellular functions, including signal transduction, cell proliferation, differentiation, adhesion and cell death. In addition, transformation of human cells to cancer cells can be associated with distinct glycosylation profiles which provide advantages for tumor growth and dissemination and can serve as immune targets. Both gangliosides and aberrant glycosylation of proteins escape the direct molecular and proteomic screening strategies currently applied to identify further immune targets in cancers. Due to their highly restricted expression and their functional roles in the malignant behavior, they are attractive targets for immune engineering strategies. G_D2-redirected CAR T cells have shown activity in clinical phase I/II trials in neuroblastoma and next-generation studies are ongoing. Further carbohydrate targets for CAR T cells in preclinical development are O-acetyl-G_D2, NeuGc-GM3 (N-glycolyl GM3), G_D3, SSEA-4, and oncofetal glycosylation variants. This review summarizes knowledge on the role and function of some membrane-expressed non-protein antigens, including gangliosides and abnormal protein glycosylation patterns, and discusses their potential to serve as a CAR targets in pediatric solid cancers.

Influence of Stereochemistry on the Bioactivation and Glucuronidation of 4-Ipomeanol

A potential CYP4B1 suicide gene application in engineered T-cell treatment of blood cancers has revived interest in the use of 4-ipomeanol (IPO) in gene-directed enzyme prodrug therapy, in which disposition of the administered compound may be critical. IPO contains one chiral center at the carbon bearing a secondary alcohol group; it was of interest to determine the effect of stereochemistry on 1) CYP4B1-mediated bioactivation and 2) (UGT)-mediated glucuronidation. First, (R)-IPO and (S)-IPO were synthesized and used to assess cytotoxicity in HepG2 cells expressing rabbit CYP4B1 and re-engineered human CYP4B1, where the enantiomers were found to be equipotent. Next, a sensitive UPLC-MS/MS assay was developed to measure the IPO-glucuronide diastereomers and product stereoselectivity in human tissue microsomes. Human liver and kidney microsomes generated (R)- and (S)-IPO-glucuronide diastereomers in ratios of 57:43 and 79:21, respectively. In a panel of 13 recombinantly expressed UGTs, UGT1A9 and UGT2B7 were the major isoforms responsible for IPO glucuronidation. (R)-IPO-glucuronide diastereoselectivity was apparent with each recombinant UGT, except UGT2B15 and UGT2B17, which favored the formation of (S)-IPO-glucuronide. Incubations with IPO and the UGT1A9-specific chemical inhibitor niflumic acid significantly decreased glucuronidation in human kidney, but only marginally in human liver microsomes, consistent with known tissue expression patterns of UGTs. We conclude that IPO glucuronidation in human kidney is mediated by UGT1A9 and UGT2B7. In human liver, it is mediated primarily by UGT2B7 and, to a lesser extent, UGT1A9 and UGT2B15. Overall, the lack of pronounced stereoselectivity for IPO's bioactivation in CYP4B1-transfected HepG2 cells, or for hepatic glucuronidation, suggests the racemate is an appropriate choice for use in suicide gene therapies.

"Therapeutic applications of the 'NPGP' family of viral 2As"

Oligopeptide "2A" and "2A-like" sequences ("2As"; 18-25aa) are found in a range of RNA virus genomes controlling protein biogenesis through "recoding" of the host-cell translational apparatus. Insertion of multiple 2As within a single open reading frame (ORF) produces multiple proteins; hence, 2As have been used in a very wide range of biotechnological and biomedical applications. During translation, these 2A peptide sequences mediate a eukaryote-specific, self-"cleaving" event, termed "ribosome skipping" with very high efficiency. A particular advantage of using 2As is the ability to simultaneously translate a number of proteins at an equal level in all eukaryotic systems although, naturally, final steady-state levels depend upon other factors-notably protein stability. By contrast, the use of internal ribosome entry site elements for co-expression results in an unbalanced expression due to the relative inefficiency of internal initiation. For example, a 1:1 ratio is of particular importance for the biosynthesis of the heavy-chain and light-chain components of antibodies: highly valuable as therapeutic proteins. Furthermore, each component of these "artificial polyprotein" systems can be independently targeted to different sub-cellular sites. The potential of this system was vividly demonstrated by concatenating multiple gene sequences, linked via 2A sequences, into a single, long, ORF-a polycistronic construct. Here, ORFs comprising the biosynthetic pathways for violacein (five gene sequences) and β-carotene (four gene sequences) were concatenated into a single cistron such that all components were co-expressed in the yeast Pichia pastoris. In this review, we provide useful information on 2As to serve as a guide for future utilities of this co-expression technology in basic research, biotechnology, and clinical applications.

Antitumor activity of CD56-chimeric antigen receptor T cells in neuroblastoma and SCLC models

The CD56 antigen (NCAM-1) is highly expressed on several malignancies with neuronal or neuroendocrine differentiation, including small-cell lung cancer and neuroblastoma, tumor types for which new therapeutic options are needed. We hypothesized that CD56-specific chimeric antigen receptor (CAR) T cells could target and eliminate CD56-positive malignancies. Sleeping Beauty transposon-generated CD56R-CAR T cells exhibited αβT-cell receptors, released antitumor cytokines upon co-culture with CD56⁺ tumor targets, demonstrated a lack of fratricide, and expression of cytolytic function in the presence of CD56⁺ stimulation. The CD56R-CAR⁺ T cells are capable of killing CD56⁺ neuroblastoma, glioma, and SCLC tumor cells in in vitro co-cultures and when tested against CD56⁺ human xenograft neuroblastoma models and SCLC models, CD56R-CAR⁺ T cells were able to inhibit tumor growth in vivo. These results indicate that CD56-CARs merit further investigation as a potential treatment for CD56⁺ malignancies.

Efficient substrate screening and inhibitor testing of human CYP4Z1 using permeabilized recombinant fission yeast

We have established a protocol for the preparation of permeabilized fission yeast cells (enzyme bags) that recombinantly express human cytochrome P450 enzymes (CYPs). A direct comparison of CYP3A4 activity gave an eightfold higher space-time yield for enzyme bag-catalyzed biotransformation as compared to whole-cell biotransformation, even though the total number of cells employed was lower by a factor of 150. Biotransformation of the luminogenic substrate Luciferin-H using CYP2C9-containing enzyme bags proceeded efficiently and stably for 24h. CYP4Z1 is of interest because it is strongly overexpressed both in breast cancer cells and in breast cancer metastases; however, current knowledge about its catalytic properties is very limited. Screening of CYP4Z1-containing enzyme bags with 15 luminogenic substrates enabled us to identify two new hydroxylations and eleven ether cleavage reactions that are catalyzed by CYP4Z1. By far the best substrate found in this study was Luciferin benzyl ether (Luciferin-BE). On the basis of the recently published crystal structure of CYP4B1 we created a new homology model of CYP4Z1 and performed molecular docking experiments, which indicate that all active substrates show a highly similar binding geometry compared to the endogenous substrates. The model predicts that Ser113, Ser222, Asn381, and Ser383 are key hydrogen bonding residues. We also identified five new inhibitors of CYP4Z1: miconazole, econazole, aminobenzotriazole, tolazoline, and 1-benzylimidazole respectively, with the last compound being the most potent giving an IC₅₀ value of 180nM in our test system.

Development of novel target modules for retargeting of UniCAR T cells to GD2 positive tumor cells

As the expression of a tumor associated antigen (TAA) is commonly not restricted to tumor cells, adoptively transferred T cells modified to express a conventional chimeric antigen receptor (CAR) might not only destroy the tumor cells but also attack target-positive healthy tissues. Furthermore, CAR T cells in patients with large tumor bulks will unpredictably proliferate and put the patients at high risk of adverse side effects including cytokine storms and tumor lysis syndrome. To overcome these problems, we previously established a modular CAR technology termed UniCAR: UniCAR T cells can repeatedly be turned on and off via dosing of a target module (TM). TMs are bispecific molecules which cross-link UniCAR T cells with target cells. After elimination of the respective TM, UniCAR T cells automatically turn off. Here we describe novel TMs against the disialoganglioside GD2 which is overexpressed in neuroectodermal but also many other tumors. In the presence of GD2-specific TMs, we see a highly efficient target-specific and -dependent activation of UniCAR T cells, secretion of pro-inflammatory cytokines, and tumor cell lysis both in vitro and experimental mice. According to PET-imaging, anti-GD2 TM enrich at the tumor site and are rapidly eliminated thus fulfilling all prerequisites of a UniCAR TM.

Ligand characterization of CYP4B1 isoforms modified for high-level expression in Escherichia coli and HepG2 cells

Human CYP4B1, a cytochrome P450 monooxygenase predominantly expressed in the lung, inefficiently metabolizes classical CYP4B1 substrates, such as the naturally occurring furan pro-toxin 4-ipomeanol (4-IPO). Highly active animal forms of the enzyme convert 4-IPO to reactive alkylating metabolite(s) that bind(s) to cellular macromolecules. By substitution of 13 amino acids, we restored the enzymatic activity of human CYP4B1 toward 4-IPO and this modified cDNA is potentially valuable as a suicide gene for adoptive T-cell therapies. In order to find novel pro-toxins, we tested numerous furan analogs in in vitro cell culture cytotoxicity assays by expressing the wild-type rabbit and variants of human CYP4B1 in human liver-derived HepG2 cells. To evaluate the CYP4B1 substrate specificities and furan analog catalysis, we optimized the N-terminal sequence of the CYP4B1 variants by modification/truncation and established their heterologous expression in Escherichia coli (yielding 70 and 800 nmol·l-1 of recombinant human and rabbit enzyme, respectively). Finally, spectral binding affinities and oxidative metabolism of the furan analogs by the purified recombinant CYP4B1 variants were analyzed: the naturally occurring perilla ketone was found to be the tightest binder to CYP4B1, but also the analog that was most extensively metabolized by oxidative processes to numerous non-reactive reaction products.