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Targeting Mitochondria in Tumor-Associated Macrophages using a Dendrimer-Conjugated TSPO Ligand that Stimulates Antitumor Signaling in Glioblastoma.

ABSTRACT: Mitochondria mediate critical cellular processes, including proliferation, apoptosis, and immune responses; as such, their dysfunction is pathogenic in many neurodegenerative disorders and cancers. In glioblastoma, targeted delivery of mitochondria-focused anticancer therapies has failed to translate into clinical success due to the nonspecific cellular localization, heterogeneity of receptor expression across patients, poor transport across biological barriers to reach the brain, tumor, and mitochondria, and systemic side effects. Strategies that can overcome brain and solid tumor barriers and selectively target mitochondria within specific cell types may lead to improvements in glioblastoma treatment. Developments in dendrimer-mediated nanomedicines have shown promise targeting tumor-associated macrophages (TAMs) in glioblastoma, following systemic administration. Here, we present a novel dendrimer conjugated to the translocator protein (18 kDa) (TSPO) ligand 5,7-dimethylpyrazolo[1,5-α]pyrimidin-3-ylacetamide (DPA). We developed a clickable DPA for conjugation on the dendrimer surface and demonstrated in vitro that the dendrimer-DPA conjugate (D-DPA) significantly increases dendrimer colocalization with mitochondria. Compared to free TSPO ligand PK11195, D-DPA stimulates greater antitumor immune signaling. In vivo, we show that D-DPA targets mitochondria specifically within TAMs following systemic administration. Our results demonstrate that dendrimers can achieve TAM-specific targeting in glioblastoma and can be further modified to target specific intracellular compartments for organelle-specific drug delivery.

SUBMITTER: Sharma A

PROVIDER: S-EPMC8022998 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We hypothesized that the potential ability of the 18 kDa mitochondrial translocator protein (TSPO) to regulate gene expression may underlie its numerous reported functions, ranging from mitochondrial activity till mental disorders. Therefore, we applied microarray analysis of gene expression to U118MG glioblastoma cells. Within 1 hr the TSPO ligand PK 11195 induced changes in expression of immediate early genes and transcription factors. After 24 hrs primarily gene expression for enzymes and other proteins is changed. The associated gene products are known to affect various cellular functions: programmed cell death, cell cycle, viability, proliferation, migration, differentiation, development, tumorigenesis, and inflammatory / immune responses. Our microscopic studies showed intense TSPO mitochondrial labeling but no TSPO signal in the cell nuclei. Thus, it appears that the TSPO is part of the retrograde mitochondrial-nuclear signaling pathway for modulation of gene expression and thereby may exert its numerous effects on cell function, phenotype, and disease. U118MG cells (1.255 Ã 106) were seeded in Petri dishes (i.e. 28.5 Ã 103 cells / cm2) and allowed to proliferate for 3 days in full medium. Experiments for gene expression assayed with microarray typically consisted of three experimental groups and a vehicle control group (n = 3 for each group). Serum deprived medium was applied for 24 hrs, in the experimental groups ending with the inclusion a choice of various PK 11195 exposures i.e. either 1 hr, 3 hrs, or 24 hrs. Exposure to PK 11195 implies serum deprived medium with 1% alcohol (vehicle) and PK 11195 (25 ÂµM final concentration) for the required time period. 25 ÂµM of PK 11195 is the optimal concentration for these types of experiments with U118MG cells (Kugler et al., 2008). The cells were collected by trypsinization, washed by centrifugation in phosphate buffered saline (PBS) (400 Ã g, 5 min), and lysed [RLT lysis buffer provided with the RNeasy Mini Kit diluted with Î²-mercaptoethanol (1 : 100)], according to the manufacturer's instructions. Lysates were stored at -70oC.

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Targeting Mitochondria in Tumor-Associated Macrophages using a Dendrimer-Conjugated TSPO Ligand that Stimulates Antitumor Signaling in Glioblastoma.

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