Targeting GD2-positive glioblastoma by chimeric antigen receptor empowered mesenchymal progenitors

Tumor targeting by genetically modified mesenchymal stromal/stem cells (MSCs) carrying anti-cancer molecules represents a promising cell-based strategy. We previously showed that the pro-apoptotic agent tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can be successfully delivered by MSCs to cancer sites. While the interaction between TRAIL and its receptors is clear, more obscure is the way in which MSCs can selectively target tumors and their antigens. Several neuroectoderm-derived neoplasms, including glioblastoma (GBM), sarcomas, and neuroblastoma, express high levels of the tumor-associated antigen GD2. We have already challenged this cell surface disialoganglioside by a chimeric antigen receptor (CAR)-T cell approach against neuroblastoma. With the intent to maximize the therapeutic profile of MSCs delivering TRAIL, we here originally developed a bi-functional strategy where TRAIL is delivered by MSCs that are also gene modified with the truncated form of the anti-GD2 CAR (GD2 tCAR) to mediate an immunoselective recognition of GD2-positive tumors. These bi-functional MSCs expressed high levels of TRAIL and GD2 tCAR associated with a robust anti-tumor activity against GD2-positive GBM cells. Most importantly, the anti-cancer action was reinforced by the enhanced targeting potential of such bi-functional cells. Collectively, our results suggest that a truncated anti-GD2 CAR might be a powerful new tool to redirect MSCs carrying TRAIL against GD2-expressing tumors. This affinity-based dual targeting holds the promise to combine site-specific and prolonged retention of MSCs in GD2-expressing tumors, thereby providing a more effective delivery of TRAIL for still incurable cancers

Cyclic polyamines via a molybdenum(0) templated Mannich-type reaction

Reaction of [Mo(CO)₃(3-azahexane-1,6-diamine)] with formaldehyde and the carbon acid nitroethane leads to cyclisation involving one terminal amine and either the internal secondary amine (minor product) or the other terminal primary amine (major product), with zinc/acid reduction yielding new cyclic tetraamines, also characterised as their cobalt(III) complexes. This is the first example of Mannich-style formation of a pendant-arm triazamacrocycle around a molybdenum(0) template. The unexpected N-(1′-aminopropyl)-6-methyl-1,4-diazacycloheptan-6-amine minor product has been characterised by an X-ray structure as its cis-dichlorocobalt(III) complex

Palladium(II) as a versatile template for the formation of tetraaza macrocycles via Mannich-type reactions

The versatility of palladium(II) as a template for Mannich-type macrocyclization is illustrated. Reaction of (bis(3-aminopropyl)piperazine)palladium(II) with formaldehyde and nitroethane in basic aqueous solution yields the 'reinforced' macrocycle 7-methyl-7-nitro-1,5,9,13-tetraazabicyclo[11.2.2]heptadecane as its palladium(II) complex. The crystal structure shows the palladium ion lies in a slightly tetrahedrally distorted square plane of four nitrogen donors, with distances to the two tertiary donors [av. 2.059(3) angstrom] slightly shorter than those to the secondary amines [av. 2.066(3) angstrom]. The 3-methyl-3-nitro-1,5,9,13-tetraazacyclohexadecane as its palladium(II) complex was prepared by an analogous route. In a separate reaction based on the [Pd(en)(chxn)](2+) (en = ethane-1,2-diamine; chxn = cyclohexane-1,2-diamine) intermediate, an unsymmetrical macrocycle with a fused cyclohexane ring, 4,11-dimethyl-4,11-dinitro-2,6,9,13-tetraazabicyclo[12.4.0]octadecane was isolated as its palladium(II) complex. Accessibility to an isolable mixed-ligand precursor is a key to this reaction, provided by using palladium(II) as the templating metal. Reaction of (4,8-diazaundecane-1,11-diamine)palladium(II) with formaldehyde and diethyl malonate in basic aqueous solution yields, with ester hydrolysis and decarboxylation, the carboxylate-pendant macrocycle 1,5,9,13-tetraazacyclohexadecane-3-carboxylic acid as its palladium(II) complex. The crystal structure is comprised of hydrogen-bonded dimers {[Pd(L)][Pd(L-H)]}(3+) where the pair of inversion related square-planar complexes share a single proton between their pendant carboxylates. Bis(3-aminopropyl)(piperazine)palladium(II) yields the macrocyclic complex ion (1,5,9,13-tetraazabicyclo[11..2.2]heptadecane-7-carboxylic acid)palladium(II), in a similar reaction

Complexation of constrained ligands piperazine, N-substituted piperazines, and thiomorpholine

Complexation of the symmetric cyclic diamine piperazine (1,4-diazacyclohexane) has been examined in dry dimethyl formamide by spectrophotometric titrations (with Cu²⁺, Ni²⁺) to define formation constants, and by stopped-flow kinetics to define the complexation rates and reaction pathway. Initial formation of a rarely observed η¹-piperazine intermediate occurs in a rapid second-order reactions. This intermediate then undergoes two competing reactions: formation of (chelated) η²-piperazine (ML) or the formation of (bridging) μ-piperazine (in M₂L and M₂L₃, speciation depending on relative concentrations). Protonation constants and formation constants for complexation in water of N-ethylpiperazine and thiomorpholine (1-aza-4-thiocyclohexane, tm) have been determined by potentiometric titration; 1:1 complexes with first-row M²⁺ display a log K from ~4 to 6, with speciation that suggests chelation of the heterocycles may be involved. Complexation of thiomorpholine has been further probed by the synthesis of Pd¹¹ complexes. The N-monodentate coordination mode has been confirmed in trans-[Pd(tm)₂Br₂] by an X-ray crystal structure. Complexation of N-(2-aminoethyl)piperazine to Cu¹¹ as a bidentate ligand involving the primary and tertiary amines is also defined by an X-ray crystal structure