Solubility-Improved 10-O -Substituted SN-38 Derivatives with Antitumor Activity

Synergistic Nanomedicine Delivering Topoisomerase I Toxin (SN-38) and Inhibitors of Polynucleotide Kinase 3'-Phosphatase (PNKP) for Enhanced Treatment of Colorectal Cancer

Inhibitors of a DNA repair enzyme known as polynucleotide kinase 3'-phosphatase (PNKP) are expected to show synergistic cytotoxicity in combination with topoisomerase I (TOP1) inhibitors in cancer. In this study, the synergistic cytotoxicity of a novel inhibitor of PNKP, i.e., A83B4C63, with a potent TOP1 inhibitor, i.e., SN-38, against colorectal cancer cells was investigated. Polymeric micelles (PMs) for preferred tumor delivery of A83B4C63, developed through physical encapsulation of this compound in methoxy poly(ethylene oxide)-poly(α-benzyl carboxylate-ε-caprolactone) (mPEO-b-PBCL) micelles, were combined with SN-38 in free or PM form. The PM form of SN-38 was prepared through chemical conjugation of SN-38 to the functional end group of mPEO-b-PBCL and further assembly of mPEO-b-PBCL-SN-38 in water. Moreover, mixed micelles composed of mPEO-b-PBCL and mPEO-b-PBCL-SN-38 were used to co-load A83B4C63 and SN-38 in the same nanoformulation. The loading content (% w/w) of the SN-38 and A83B4C63 to mPEO-b-PBCL in the co-loaded formulation was 7.91 ± 0.66 and 16.13 ± 0.11% (w/w), respectively, compared to 15.67 ± 0.34 (% w/w) and 23.06 ± 0.63 (% w/w) for mPEO-b-PBCL micelles loading individual drugs. Notably, the average diameter of PMs co-encapsulating both SN-38 and A83B4C63 was larger than that of PMs encapsulating either of these compounds alone but still lower than 60 nm. The release of A83B4C63 from PMs co-encapsulating both drugs was 76.36 ± 1.41% within 24 h, which was significantly higher than that of A83B4C63-encapsulated micelles (42.70 ± 0.72%). In contrast, the release of SN-38 from PMs co-encapsulating both drugs was 44.15 ± 2.61% at 24 h, which was significantly lower than that of SN-38-conjugated PMs (74.16 ± 3.65%). Cytotoxicity evaluations by the MTS assay as analyzed by the Combenefit software suggested a clear synergy between PM/A83B4C63 (at a concentration range of 10-40 μM) and free SN-38 (at a concentration range of 0.001-1 μM). The synergistic cytotoxic concentration range for SN-38 was narrowed down to 0.1-1 or 0.01-1 μM when combined with PM/A83B4C63 at 10 or 20-40 μM, respectively. In general, PMs co-encapsulating A83B4C63 and SN-38 at drug concentrations within the synergistic range (10 μM for A83B4C63 and 0.05-1 μM for SN-38) showed slightly less enhancement of SN-38 anticancer activity than a combination of individual micelles, i.e., A83B4C63 PMs + SN-38 PMs at the same molar concentrations. This was attributed to the slower release of SN-38 from the SN-38 and A83B4C63 co-encapsulated PMs compared to PMs only encapsulating SN-38. Cotreatment of cells with TOP1 inhibitors and A83B4C63 formulation enhanced the expression level of γ-HA2X, cleaved PARP, caspase-3, and caspase-7 in most cases. This trend was more consistent and notable for PMs co-encapsulating both A83B4C63 and SN-38. The overall result from the study shows a synergy between PMs of SN-38 and A83B4C63 as a mixture of two PMs for individual drugs or PMs co-encapsulating both drugs.

Effect of 23‑hydroxybetulinic acid on lung adenocarcinoma and its mechanism of action

The present study aimed to investigate the effect and mechanism of Pulsatilla compounds on lung adenocarcinoma. The representative drug chosen was the compound 23-HBA. GeneCards, Swiss target prediction, DisGeNET and TCMSP were used to screen out related genes, and MTT and flow cytometry assays were used to verify the inhibitory effect of Pulsatilla compounds on the proliferation of lung adenocarcinoma cells. Subsequently, the optimal target, peroxisome proliferator-activated receptor (PPAR)-γ, was selected using bioinformatics analysis, and its properties of low expression in lung adenocarcinoma cells and its role as a tumor suppressor gene were verified by western blot assay. The pathways related to immunity and inflammation, vascular function, cell proliferation, differentiation, development and apoptosis with the highest degree of enrichment and the mechanisms were explored through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Finally, the clinical prognosis in terms of the survival rate of patients in whom the drug is acting on the target was analyzed using the GEPIA database. The results indicated that Pulsatilla compounds can inhibit the proliferation of lung adenocarcinoma cells by blocking the cell cycle at the G1 phase. Subsequently, the related PPAR-γ gene was verified as a tumor suppressor gene. Further analysis demonstrated that this finding was related to the PPAR signaling pathway and mitochondrial reactive oxygen species (ROS) production. Finally, the clinical prognosis was found to be improved, as the survival rate of patients was increased. In conclusion, Pulsatilla compounds were indicated to inhibit the viability and proliferation of lung adenocarcinoma H1299 cells, and the mechanism of action was related to PPAR-γ, the PPAR signaling pathway and mitochondrial ROS. The present study provides novel insight to further explore the treatment of lung adenocarcinoma.

Structural Modification Endows Small-Molecular SN38 Derivatives with Multifaceted Functions

As a camptothecin derivative, 7-ethyl-10-hydroxycamptothecin (SN38) combats cancer by inhibiting topoisomerase I. SN38 is one of the most active compounds among camptothecin derivatives. In addition, SN38 is also a theranostic reagent due to its intrinsic fluorescence. However, the poor water solubility, high systemic toxicity and limited action against drug resistance and metastasis of tumor cells of SN38 indicates that there is great space for the structural modification of SN38. From the perspective of chemical modification, this paper summarizes the progress of SN38 in improving solubility, increasing activity, reducing toxicity and possessing multifunction and analyzes the strategies of structure modification to provide a reference for drug development based on SN38.

Gold nanorods-loaded chitosan-based nanomedicine platform enabling an effective tumor regression in vivo

The clinical utility of 7-ethyl-10-hydroxycamptothecin (SN-38) is hampered by its low water solubility and reduced bioactivity at neutral or alkaline conditions. The rational design of an effective drug delivery system that can significantly enhance the therapeutic index of SN-38 and achieve complete tumor regression still remains a challenge. Herein, chitosan-based hybrid nanoparticles system co-loading with chemotherapeutic drug SN-38 and gold nanorods (AuNRs) was engineered for effective combinational photothermal-chemotherapy. To increase the solubility of SN-38, soluble polymeric prodrug poly (l-glutamic acid)-SN38 (l-PGA-SN38) was firstly synthesized and then complexed with chitosan to form stable nanomedicine via a mild and facile way without using any organic solvent or surfactant. Upon introducing AuNRs into chitosan-based nanomedicine by coordination interaction between the amine group of chitosan and AuNRs, the hybrid nanoparticles exhibited distinct synergistic therapeutic effect compared with single chemotherapy or photothermal treatment in vitro and in vivo. Almost complete tumor regression was achieved after 21-day treatment of the developed hybrid nanoparticles and showed no recurrence for at least 60 days.

Synthesis and biological evaluation of novel SN38-glucose conjugate for colorectal cancer treatment

7-Ethyl-10-hydroxycamptothecin (SN38), the bioactive metabolite of irinotecan (CPT-11), has been shown to be 100-1000 times more effective than CPT-11. However, the poor water solubility and bioavailability of SN38 constrained its clinical application. In this study, we synthesized a novel SN38-glucose conjugate (FSY04) to address this issue. Our in vitro studies indicated that FSY04 had a potent inhibitory ability against colorectal cancer (CRC) cell lines of SW-480 and HCT-116 compared to the inhibitory capacity of CPT-11. Interestingly, FSY04 possessed lower cytotoxicity against normal cell lines of LO2 and 293T in contrast with CPT-11. Moreover, FSY04 is more active than CPT-11 in inducing apoptosis, inhibiting migration, and invasion. In vivo experiments suggested that half of the equivalent of FSY04 inhibited the growth of SW480 in the xenograft tumor model better than one equivalent of CPT-11. Our data demonstrated FSY04 to be a promising agent in CRC therapy.

Redox responsive 7-ethyl-10-hydroxycamptothecin (SN38) lysophospholipid conjugate: synthesis, assembly and anticancer evaluation

7-Ethyl-10-hydroxycamptothecin (SN38), a potent camptothecin derivative specifically targeting DNA topoisomerase I cleavage complexes, has shown great potential in the treatment of solid tumors. Because of its poor solubility and chemical and metabolic stability, the clinical application of SN38 is highly limited. To address these problems, a novel redox-responsive SN38 conjugate based liposomal formulation is developed in this report. First, SN38 was conjugated with lysophospholipid by using a cleavable disulfide bond linker. After that, the conjugate (SN38-SS-PC) was assembled into liposomes by thin film method. Dynamic lightscattering(DLS) characterization indicated that SN38-SS-PC liposomes possessed a narrow size distribution (172.8 ± 10.5 nm) and negative charged zeta potential (-8.9 ± 0.3 mV). The results of storage and physiological stabilities showed that SN38-SS-PC liposomes was stable under different conditions. More importantly, a reduction responsive release of parent drug SN38 was observed in the medium containing glutathione (GSH). In addition, SN38-SS-PC liposomes had a much more rapid cellular uptake behavior against cancer cells. The enhanced anti-cancer efficacy of SN38-SS-PC liposomes was further demonstrated by in vitro cytotoxicity assay against MCF-7 and A549 cells. Under in vivo evaluation in 4 T1 xenograft tumor model, SN38-SS-PC liposomes were observed to have lower systemic toxicity and higher tumor inhibition rate of 53.3% compared with the commercialized SN38 prodrug Irinotecan (Ir). In summary, SN38-SS-PC liposomes could be a promising redox responsive delivery system of SN38 for cancer therapy.

Synthesis and Biological Evaluation of 10-Substituted Camptothecin Derivatives with Improved Water Solubility and Activity

Despite remarkable clinical achievements, camptothecin (CPT) still suffers from poor solubility and severe toxicity. Therefore, it is necessary to redevelop CPT derivatives as supplementary antitumor agents with good water solubility and small side effects. In this work, 27 camptothecin derivatives were synthesized and screened for their cytotoxicity against A549 (lung) and HCT-116 (colon) cancer cell lines. Among them, compound B7, 7-ethyl-10-(2-oxo-2-(4-methylpiperidin-1-yl)ethoxy)camptothecin,was demonstrated in vitro to be a more potent antitumor agent than SN-38 by comparison of their inhibitory activities against cell proliferation and colony formation and interference effect on process of cell cycle and cell apoptosis. Additionally, a molecular docking model revealed that B7 can interact with the topoisomerase I-DNA complex, and that the solubility of B7 reached 5.73 μg/mL in water. Moreover, B7 significantly inhibited tumor growth in an A549 xenograft model at dosages of 0.4 and 2.0 mg/kg, and exhibited minimum lethal doses comparable to those of irinotecan. These results indicated that B7, with improved solubility, enhanced activity and acceptable acute toxicity, can be used as a lead compound for the development of novel anticancer agents.

F10, a new camptothecin derivative, was identified as a new orally-bioavailable, potent antitumor agent

Topoisomerases are interesting targets for drug discovery. In the present study, we attached saturated carbon atoms to the 10-position of camptothecin and synthesized 10 new camptothecin derivatives from 10-HCPT or SN-38. The activities of new compounds were evaluated both in vitro and in vivo. The most promising compound F10, 7-ethyl-10-(2-oxo-2-(piperidin-1-yl)ethoxy)camptothecin, inhibited cancer cells growth with the IC₅₀ of 0.002, 0.003, 0.011 and 0.081 μM on Raji, HCT116, A549 and Lovo cells, respectively. Meanwhile, oral administration of F10 remarkably suppressed the HCT116-xenograft tumor growth in the nude-mice model at the dosage of 0.5, 2.0 and 8.0 mg/kg in vivo. Intraperitoneal administration of F10 can completely inhibit Raji-xenograft tumor growth in established NPG mouse model at 2.0 and 4.0 mg/kg. In addition, the minimum lethal doses of F10 and SN-38 in mice by intravenous administration were 80 and 40 mg/kg (or 0.155, 0.102 mmol/kg), respectively. The solubility of F10 reached 9.86 μg/mL in a buffer solution of pH 4.5. The oral bioavailability of F10 achieved 22.4% in mice. The molecular docking model revealed that F10 can interact with topoisomerase I-DNA complex. Our findings indicate that F10 is a new orally-oavailable antitumor agent with potent anticancer effect. Furthermore, attaching a ring hydrophobic moiety to the 10-position of camptothecin provides a favorable approach in the optimization of camptothecin.

Solvent-dependent regioselectivity of 2′-deoxyadenosine alkylation by 9-aminomethyl derivatives of SN38

The investigated compounds in DMSO solution unexpectedly alkylate the N9 nitrogen of 2′-deoxyadenosine, whereas the N6 nitrogen atom is alkylated in water solution.