Preparation and Preliminary Evaluation of 68Ga-Acridine: An Attempt to Study the Potential of Radiolabeled DNA Intercalator as a PET Radiotracer for Tumor Imaging

In situ administration of temperature-sensitive hydrogel composite loading paclitaxel microspheres and cisplatin for the treatment of melanoma

Chemotherapy is one of the main therapeutic strategies for the treatment of malignant melanoma. Conventional chemotherapeutic agents often lack targeting abilities, and efficacy is hampered by their high toxic effects to normal tissues and rapid clearance from the circulation. In this study, porous paclitaxel (PTX)-loaded polylactide (PLA) microspheres (PPMSs) were prepared by a modified double-emulsion-solvent evaporation method. In addition, PPMSs and cisplatin (DDP) were co-embedded in a thermosensitive hydrogel to construct a dual-drug co-delivery hydrogel system (PPMSs/DDP@Gel) for in-situ chemotherapy to treat melanoma by means of an intra-tumoral injection. The system allows for the sustained release of two drugs and exhibits good temperature-sensitive properties. In vitro antitumor activity showed that this hydrogel composite can induce B16 cell apoptosis and inhibit its migration. In vivo, anti-tumor studies have shown that the PPMSs/DDP@Gel significantly inhibited tumor growth, prolonged the survival of tumor-bearing mice, and had no obvious toxic side effects on major organs. Furthermore, immunohistochemical analysis revealed that PPMSs/DDP@Gel significantly inhibited tumor cell proliferation and promoted apoptosis of tumor cells. Taken together, the injectable temperature-sensitive PPMSs/DDP@Gel is a promising candidate for the local treatment of melanoma.

Targeted Tumor Therapy with Radiolabeled DNA Intercalator: A Possibility? Preclinical Investigations with 177Lu-Acridine

Objective

A DNA intercalating agent reversibly stacks between the adjacent base pairs of DNA and thus is expected to exhibit preferential localization in the tumorous lesions as tumors are associated with enhanced DNA replication. Therefore, radiolabeled DNA intercalators are supposed to have potential to be used in targeted tumor therapy. Working in this direction, an attempt was made to radiolabel 9-aminoacridine, a DNA intercalator, with ¹⁷⁷Lu, one of the most useful therapeutic radionuclides, and study the potential of ¹⁷⁷Lu-acridine in targeted tumor therapy. Experiments. 9-Aminoacridine was coupled with p-NCS-benzyl-DOTA to facilitate radiolabeling, and the conjugate was radiolabeled with ¹⁷⁷Lu. Different reaction parameters were optimized in order to obtain ¹⁷⁷Lu-acridine complex with maximum radiochemical purity. In vitro stability of the radiolabeled complex was studied in normal saline and human blood serum. Biological behavior of the radiolabeled agent was studied both in vitro and in vivo using the Raji cell line and fibrosarcoma tumor-bearing Swiss mice, respectively.

Results

¹⁷⁷Lu-acridine complex was obtained with ~100% radiochemical purity under the optimized reaction conditions involving incubation of 1.5 mg/mL of ligand with ¹⁷⁷Lu (1 mCi, 37 MBq) at 100°C at pH ~5 for 45 minutes. The complex maintained a radiochemical purity of >85% in saline at 6 d and >70% in human serum at 2 d postpreparation. In vitro cellular study showed uptake of the radiotracer (5.3 ± 0.13%) in the Raji cells along with significant cytotoxicity (78.06 ± 2.31% after 6 d). Biodistribution study revealed considerable accumulation of the radiotracer in tumor 9.98 ± 0.13 %ID/g within 1 h postadministration and retention therein till 6 d postadministration 4.00 ± 0.16 %ID/g with encouraging tumor to nontarget organ uptake ratios.

Conclusions

The present study, although preliminary, indicates the potential of ¹⁷⁷Lu-acridine and thus radiolabeled DNA intercalators in targeted tumor therapy. However, further detailed evaluation is required to explore the actual potential of such agents in targeted tumor therapy.