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Introduction B cell acute lymphoblastic leukemia (B-ALL) is the most commonly diagnosed pediatric cancer, with incidence peaking between the ages of 2 and 5 years (1). The success of multidrug [...], DYRK1A is a serine/threonine kinase encoded on human chromosome 21 (HSA21) that has been implicated in several pathologies of Down syndrome (DS), including cognitive deficits and Alzheimer's disease. Although children with DS are predisposed to developing leukemia, especially B cell acute lymphoblastic leukemia (B-ALL), the HSA21 genes that contribute to malignancies remain largely undefined. Here, we report that DYRK1A is overexpressed and required for B-ALL. Genetic and pharmacologic inhibition of DYRK1A decreased leukemic cell expansion and suppressed B-ALL development in vitro and in vivo. Furthermore, we found that FOXO1 and STAT3, transcription factors that are indispensable for B cell development, are critical substrates of DYRK1A. Loss of DYRK1A-mediated FOXO1 and STAT3 signaling disrupted DNA damage and ROS regulation, respectively, leading to preferential cell death in leukemic B cells. Thus, we reveal a DYRK1A/FOXO1/STAT3 axis that facilitates the development and maintenance of B-ALL.

The bradykinin receptor B1R is overexpressed in many human cancers where it might be used as a general target for cancer imaging. In this study, we evaluated the feasibility of using radiolabeled kallidin derivatives to visualize B1R expression in a preclinical model of B1R-positive tumors. Three synthetic derivatives were evaluated in vitro and in vivo for receptor binding and their ability to visualize tumors by PET. Enalaprilat and phosphoramidon were used to evaluate the impact of peptidases on tumor visualization. While we found that radiolabeled peptides based on the native kallidin sequence were ineffective at visualizing B1R-positive tumors, peptidase inhibition with phosphoramidon greatly enhanced B1R visualization in vivo. Two stabilized derivatives incorporating unnatural amino acids (68Ga-SH01078 and 68Ga-P03034) maintained receptor-binding affinities that were effective, allowing excellent tumor visualization, minimal accumulation in normal tissues, and rapid renal clearance. Tumor uptake was blocked in the presence of excess competitor, confirming that the specificity of tumor accumulation was receptor mediated. Our results offer a preclinical proof of concept for noninvasive B1R detection by PET imaging as a general tool to visualize many human cancers. [ABSTRACT FROM AUTHOR]

The chimeric transcription factor TCF3-HLF defines an incurable acute lymphoblastic leukemia subtype. Here we decipher the regulome of endogenous TCF3-HLF and dissect its essential transcriptional components and targets by functional genomics. We demonstrate that TCF3-HLF recruits HLF binding sites at hematopoietic stem cell/myeloid lineage associated (super-) enhancers to drive lineage identity and self-renewal. Among direct targets, hijacking an HLF binding site in a MYC enhancer cluster by TCF3-HLF activates a conserved MYC-driven transformation program crucial for leukemia propagation in vivo. TCF3-HLF pioneers the cooperation with ERG and recruits histone acetyltransferase p300 (EP300), conferring susceptibility to EP300 inhibition. Our study provides a framework for targeting driving transcriptional dependencies in this fatal leukemia. • TCF3-HLF remodels lineage-specific enhancers and blocks lymphoid differentiation • A dominant MYC-driven program relies on an HLF binding site in a MYC enhancer cluster • A functional genomic and proteomic approach uncovers druggable oncogenic determinants • Super-enhancer activity of TCF3-HLF confers EP300 vulnerability The presence of TCF3-HLF defines a subset of acute lymphoblastic leukemia resistant to therapy. Huang et al. show that TCF3-HLF activates the expression of genes critical for hematological malignancies, which requires EP300. Inhibition of EP300 reduces TCF3-HLF-dependent gene expression and leukemia growth. [ABSTRACT FROM AUTHOR]

Purpose: Children with Down syndrome (constitutive trisomy 21) that develop acute lymphoblastic leukemia (DS-ALL) have a 3-fold increased likelihood of treatment-related mortality coupled with a higher cumulative incidence of relapse, compared with other children with B-cell acute lymphoblastic leukemia (B-ALL). This highlights the lack of suitable treatment for Down syndrome children with B-ALL., Experimental Design: To facilitate the translation of new therapeutic agents into clinical trials, we built the first preclinical cohort of patient-derived xenograft (PDX) models of DS-ALL, comprehensively characterized at the genetic and transcriptomic levels, and have proven its suitability for preclinical studies by assessing the efficacy of drug combination between the MEK inhibitor trametinib and conventional chemotherapy agents., Results: Whole-exome and RNA-sequencing experiments revealed a high incidence of somatic alterations leading to RAS/MAPK pathway activation in our cohort of DS-ALL, as well as in other pediatric B-ALL presenting somatic gain of the chromosome 21 (B-ALL+21). In murine and human B-cell precursors, activated KRAS G12D functionally cooperates with trisomy 21 to deregulate transcriptional networks that promote increased proliferation and self renewal, as well as B-cell differentiation blockade. Moreover, we revealed that inhibition of RAS/MAPK pathway activation using the MEK1/2 inhibitor trametinib decreased leukemia burden in several PDX models of B-ALL+21, and enhanced survival of DS-ALL PDX in combination with conventional chemotherapy agents such as vincristine., Conclusions: Altogether, using novel and suitable PDX models, this study indicates that RAS/MAPK pathway inhibition represents a promising strategy to improve the outcome of Down syndrome children with B-cell precursor leukemia., (©2020 American Association for Cancer Research.)

Apoptosis is a complex multi-step process driven by caspase-dependent proteolytic cleavage cascades. Dysregulation of apoptosis promotes tumorigenesis and limits the efficacy of chemotherapy. To assess the complex interactions among caspases during apoptosis, we disrupted caspase-8, -9, -3, -7, or -6 and combinations thereof, using CRISPR-based genome editing in living human leukemia cells. While loss of apical initiator caspase-8 or -9 partially blocked extrinsic or intrinsic apoptosis, respectively, only combined loss of caspase-3 and -7 fully inhibited both apoptotic pathways, with no discernible effect of caspase-6 deficiency alone or in combination. Caspase-3/7 double knockout cells exhibited almost complete inhibition of caspase-8 or -9 activation. Furthermore, deletion of caspase-3 and -7 decreased mitochondrial depolarization and cytochrome c release upon apoptosis activation. Thus, activation of effector caspase-3 or -7 sets off explosive feedback amplification of upstream apoptotic events, which is a key feature of apoptotic signaling essential for efficient apoptotic cell death.

The cystine transporter (system x C - ) is an antiporter of cystine and glutamate. It has relatively low basal expression in most tissues and becomes upregulated in cells under oxidative stress (OS) as one of the genes expressed in response to the antioxidant response element promoter. We have developed 18 F-5-fluoroaminosuberic acid (FASu), a PET tracer that targets system x C - The goal of this study was to evaluate 18 F-FASu as a specific gauge for system x C - activity in vivo and its potential for breast cancer imaging. Methods: 18 F-FASu specificity toward system x C - was studied by cell inhibition assay, cellular uptake after OS induction with diethyl maleate, with and without anti-xCT small interfering RNA knockdown, in vitro uptake studies, and in vivo uptake in a system x C - -transduced xenograft model. In addition, radiotracer uptake was evaluated in 3 breast cancer models: MDA-MB-231, MCF-7, and ZR-75-1. Results: Reactive oxygen species-inducing diethyl maleate increased glutathione levels and 18 F-FASu uptake, whereas gene knockdown with anti-xCT small interfering RNA led to decreased tracer uptake. 18 F-FASu uptake was robustly inhibited by system x C - inhibitors or substrates, whereas uptake was significantly higher in transduced cells and tumors expressing xCT than in wild-type HEK293T cells and tumors ( P < 0.0001 for cells, P = 0.0086 for tumors). 18 F-FASu demonstrated tumor uptake in all 3 breast cancer cell lines studied. Among them, triple-negative breast cancer MDA-MB-231, which has the highest xCT messenger RNA level, had the highest tracer uptake ( P = 0.0058 when compared with MCF-7; P < 0.0001 when compared with ZR-75-1). Conclusion: 18 F-FASu as a system x C - substrate is a specific PET tracer for functional monitoring of system x C - and OS imaging. By enabling noninvasive analysis of x C - responses in vivo, this biomarker may serve as a valuable target for the diagnosis and treatment monitoring of certain breast cancers., (© 2017 by the Society of Nuclear Medicine and Molecular Imaging.)

The neuropeptide Y 1 receptor (Y1R) is overexpressed in many human cancers, particularly breast cancer. Due to stability issues, limited success has been achieved for Y1R imaging agents, including full length and truncated neuropeptide Y (NPY) analogues. The goal of this study was to evaluate the possibility of using radiolabeled truncated NPY analogues to visualize Y1R expression in a preclinical model of Y1R-positive tumor. Four truncated NPY analogues were synthesized based on the sequence of [Pro 30 , Tyr 32 , Leu 34 ]NPY(28-36), also known as BVD15. We substituted Tyr 5 and Arg 6 with unnatural amino acids aiming to enhance plasma stability while maintaining good receptor binding affinity to Y1R. In addition, we substituted Leu 4 to Lys 4 in order to conjugate via an optional linker the DOTA chelator for 68 Ga labeling. Receptor binding affinity and plasma stability of these compounds were evaluated. Positron emission tomography/computed tomography (PET/CT) imaging and biodistribution studies were performed using immune-compromised mice bearing HEK293T::WT and HEK293T::hY1R tumors. [Lys(Ga-DOTA) 4 , Bip 5 ]BVD15 (CCZ01035), [Lys(Ahx-Ga-DOTA) 4 , Bip 5 ]BVD15 (CCZ01053), and [Lys(Pip-Ga-DOTA) 4 , Bip 5 ]BVD15 (CCZ01055) demonstrated good binding affinity to Y1R (K i = 23.4-32.3 nM), while [Lys(Ga-DOTA) 4 , Har 6 ]BVD15 (P05067) showed poor binding affinity (K i > 1000 nM). In addition, CCZ01055 exhibited low binding affinity (K i > 1000 nM) to Y2R and Y4R, demonstrating its selectivity to Y1R. The former three peptides showed improved in vitro plasma stability of 7-16% remaining intact after 1 h incubation. PET/CT imaging and biodistribution studies for 68 Ga-labeled CCZ01053, CCZ01035, and CCZ01055 showed that radioactivity was mainly cleared by the renal pathway, and HEK293T::hY1R tumors were clearly visualized with minimal background activity with the latter two. Of these two tracers, [ 68 Ga]CCZ01055 provided lower kidney accumulation and higher contrast, i.e., average uptake ratios of Y1R tumor to wild type tumor, blood, and muscle are 3.87 ± 0.83, 4.12 ± 1.14, and 17.6 ± 4.64, respectively. Furthermore, Y1R tumor uptake with [ 68 Ga]CCZ01055 was significantly reduced with coinjection of 100 μg of peptide YY, confirming the specificity of tumor accumulation was receptor mediated. We successfully developed the first Y1R-targeting truncated NPY analogues for PET imaging in a preclinical model, and [ 68 Ga]CCZ01055 is a critical template for designing improved imaging agents to detect Y1R expressing cancers.

Bradykinin B1 receptor (B1R), which is upregulated in a variety of malignancies, is an attractive cancer imaging biomarker. In this study we optimized the selection of radiolabel-chelator complex to improve tumor uptake and tumor-to-background contrast of radiolabeled analogues of B9958 (Lys-Lys-Arg-Pro-Hyp-Gly-Cpg-Ser-d-Tic-Cpg), a potent B1R antagonist. Peptide sequences were assembled on solid phase. Cold standards were prepared by incubating DOTA-/NODA-conjugated peptides with GaCl3, and by incubating AlOH-NODA-conjugated peptide with NaF. Binding affinities were measured via in vitro competition binding assays. (68)Ga and (18)F labeling experiments were performed in acidic buffer and purified by HPLC. Imaging/biodistribution studies were performed in mice bearing both B1R-positive (B1R+) HEK293T::hB1R and B1R-negative (B1R-) HEK293T tumors. Z02176 (Ga-DOTA-Pip-B9958; Pip: 4-amino-(1-carboxymethyl)piperidine), Z02137 (Ga-NODA-Mpaa-Pip-B9958; Mpaa: 4-methylphenylacetic acid), and Z04139 (AlF-NODA-Mpaa-Pip-B9958) bound hB1R with high affinity (Ki = 1.4-2.5 nM). (68)Ga-/(18)F-labeled peptides were obtained on average in ≥32% decay-corrected radiochemical yield with >99% radiochemical purity and 100-261 GBq/μmol specific activity. Biodistribution/imaging studies at 1 h postinjection showed that all tracers cleared rapidly from background tissues (except kidneys) and were excreted predominantly via the renal pathway. Only kidneys, bladders, and B1R+ tumors were clearly visualized in PET images. Uptake in B1R+ tumor was higher by using (68)Ga-Z02176 (28.9 ± 6.21 %ID/g) and (18)F-Z04139 (22.6 ± 3.41 %ID/g) than (68)Ga-Z02137 (14.0 ± 4.86 %ID/g). The B1R+ tumor-to-blood and B1R+ tumor-to-muscle contrast ratios were also higher for (68)Ga-Z02176 (56.1 ± 17.3 and 167 ± 57.6) and (18)F-Z04139 (58.0 ± 20.9 and 173 ± 42.9) than (68)Ga-Z02137 (34.3 ± 15.2 and 103 ± 30.2). With improved target-to-background contrast (68)Ga-Z02176 and (18)F-Z04139 are promising for imaging B1R expression in cancers with PET.

Carbonic anhydrase IX (CA-IX) is a HIF-1-inducible enzyme that is overexpressed in many cancer subtypes to promote survival and invasion in hypoxic niches. Pharmacologic inhibition of CA-IX is achievable through sulfonamide-based inhibitors and has been shown to reduce primary growth of cancers and distant metastasis in preclinical models. We explored a multivalent approach for targeting CA-IX in vivo, noninvasively, with positron emission tomography. Three (68)Ga-polyaminocarboxylate chelator complex-conjugated tracers containing one, two, or three 4-(2-aminoethyl)benzenesulfonamide moieties were synthesized and evaluated for protein binding and imaging properties. Binding affinity to CA-I, -II, -IX, and -XII were determined using a stopped-flow CA catalyzed CO2 hydration assay. Biodistribution and PET/CT imaging were performed using immunocompromised mice bearing CA-IX expressing HT-29 colorectal tumors. Compounds demonstrated good binding affinity to CA-IX (Ki: 7.7-25.4 nM). (68)Ga-labeled sulfonamides were obtained in 64-91% decay-corrected average radiochemical yields with 50-536 GBq/μmol specific activity and >97% average radiochemical purity. All three tracers allowed for the visualization of tumor xenografts at 1 h postinjection, with the monomer displaying the highest contrast. Tumor uptake of the monomer was blockable in the presence of acetazolamide, confirming target specificity. The monomer was excreted predominantly through the kidneys, while the dimer and trimer were cleared by both renal and hepatobiliary pathways. According to biodistribution analysis, tumor uptake (%ID/g) of the monomeric, dimeric, and trimeric tracers were 0.81 ± 0.15, 1.93 ± 0.26, and 2.30 ± 0.53 at 1 h postinjection. This corresponded to tumor-to-muscle ratios of 5.02 ± 0.22, 4.07 ± 0.87, and 4.18 ± 0.84, respectively. Our data suggest that (68)Ga-polyaminocarboxylate chelator-conjugated sulfonamides can be used to noninvasively image CA-IX. These CA-IX targeting PET tracers may be used to identify patients who can benefit from treatments targeting this protein or serve as surrogate imaging agents for tumor hypoxia.

Bradykinin B1 receptor (B1R) that is overexpressed in cancers but minimally expressed in normal healthy tissues represents an attractive biomarker for the development of cancer imaging agents. The goal of this study was to evaluate the effect of different linkers on the pharmacokinetics and tumor uptake of a B1R-targeting radio-peptide sequence, 68Ga-DOTA-linker-Lys-Arg-Pro-Hyp-Gly-Cha-Ser-Pro-Leu. Four peptides, SH01078, P03034, P04115, and P04168, with 6-aminohexanoic acid, 9-amino-4,7-dioxanonanoic acid, Gly-Gly, and 4-amino-(1-carboxymethyl)piperidine, respectively, as the linker were synthesized and evaluated. In vitro competition binding assays showed that the Ki values of SH01078, P03034, P04115, and P04168 were 27.8±4.9, 16.0±1.9, 11.4±2.5, and 3.6±0.2 nM, respectively. Imaging and biodistribution studies were performed in mice bearing both B1R-positive HEK293T::hB1R and B1R-negative HEK293T tumors. All tracers showed mainly renal excretion with excellent tumor visualization and minimal background activity except for kidneys and bladder. The average uptake of 68Ga-labeled SH01078, P03034, and P04115 in HEK293T::hB1R tumor was similar (1.96-2.17%ID/g) at 1 h postinjection. 68Ga-P04168 generated higher HEK293T::hB1R tumor uptake (4.15±1.13%ID/g) and lower background activity, leading to a >2-fold improvement in HEK293T::hB1R tumor-to-background (HEK293T tumor, blood, muscle, and liver) contrasts over those of 68Ga-labeled SH01078, P03034, and P04115. Our results indicate that the choice of linker affects binding affinity, pharmacokinetics, and tumor targeting. The use of the cationic 4-amino-(1-carboxymethyl)piperidine linker improved tumor visualization, and the resulting 68Ga-P04168 might be promising for clinical application for imaging B1R-expressing tumors with positron emission tomography.

Unlabelled: Bradykinin B1 receptor (B1R) is a G-protein-coupled receptor that is overexpressed in a variety of cancers. B1R is not expressed in healthy tissues, making it an attractive cancer imaging marker. Previously, we reported selective uptake of (68)Ga-P03034 ((68)Ga-DOTA-dPEG2-Lys-Arg-Pro-Hyp-Gly-Cha-Ser-Pro-Leu) in B1R-positive (B1R+) HEK293T::hB1R tumor xenografts in mice. In this study, we compare (68)Ga-P03034 with (68)Ga-labeled P04158 ((68)Ga-DOTA-dPEG2-Lys-Lys-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic) and Z02090 ((68)Ga-DOTA-dPEG2-Lys-Lys-Arg-Pro-Hyp-Gly-Cpg-Ser-D-Tic-Cpg) derived from 2 potent B1R antagonists, B9858 and B9958, respectively, for imaging B1R expression with PET., Methods: Peptide sequences were assembled on solid-phase. Cold standards were prepared by incubating DOTA-conjugated peptides with GaCl3. Binding affinity was measured via competition binding assays using hB1R-expressing Chinese hamster ovary-K1 cell membranes. (68)Ga labeling was performed in N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) buffer with microwave heating and purified by high-performance liquid chromatography. Imaging/biodistribution studies were performed in mice bearing wild-type HEK293T (B1R-) and B1R+ HEK293T::hB1R tumors., Results: P03034, P04158, and Z02090 bound B1R with high affinity, with Ki values at 16.0 ± 2.9, 1.5 ± 1.9, and 1.1 ± 0.8 nM, respectively. (68)Ga-labeled P03034, P04159, and Z02090 were obtained in greater than 50% decay-corrected radiochemical yields with more than 99% radiochemical purity. Biodistribution studies showed that all three (68)Ga-labeled tracers cleared rapidly from the blood and normal tissues, with excretion mainly via the renal pathway. At 1 h after injection, only the kidneys, bladders, and B1R+ HEK293T::hB1R tumors were clearly visualized in PET images. Uptake values of (68)Ga-labeled P03034, P04158, and Z02090 in B1R+ tumors were 2.17 ± 0.49, 19.6 ± 4.50, and 14.4 ± 1.63 percentage injected dose per gram, respectively. Uptake ratios of B1R+ to B1R- tumor, blood, and muscle were 6.23 ± 1.69, 5.72 ± 2.20, and 25.5 ± 13.1 for (68)Ga-P03034; 34.5 ± 10.5, 19.2 ± 8.21, and 66.1 ± 17.0 for (68)Ga-P04158; and 29.3 ± 9.68, 29.9 ± 5.58, and 124 ± 28.1 for (68)Ga-Z02090, respectively., Conclusion: All three (68)Ga-labeled B1R-targeting peptides generated specific and high-contrasted images of B1R+ tumors xenografted in mice. With significantly higher tumor uptake and target-to-nontarget ratios, (68)Ga-labeled P04158 and Z02090 are superior to P03034 for imaging B1R expression with PET., (© 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)