Macrophages are the front soldiers of the innate immune system and are vital for immune defense, tumor surveillance, and tissue homeostasis. In chronic diseases, including cancer and liver fibrosis, macrophages can be forced into an immunosuppressive and profibrotic M2 phenotype. M2-type macrophages overexpress the mannose receptor CD206. Targeting these cells via CD206 and macrophage repolarization towards an immune stimulating and antifibrotic M1 phenotype through RNA interference represents an appealing therapeutic approach. We designed nanohydrogel particles equipped with mannose residues on the surface (ManNP) that delivered siRNA more efficiently to M2 polarized macrophages compared to their untargeted counterparts (NonNP) in vitro. The ManNP were then assessed for their in vivo targeting potential in mice with experimental liver fibrosis that is characterized by increased profibrotic (and immunosuppressive) M2-type macrophages. Double-labelled siRNA-loaded ManNP carrying two different near infrared labels for siRNA and ManNP showed good biocompatibility and robust uptake in fibrotic livers as assessed by in vivo near infrared imaging. siRNA–ManNP were highly colocalized with CD206⁺ M2-type macrophages on a cellular level, while untargeted NP (NonNP) showed little colocalization and were non-specifically taken up by other liver cells. ManNP did not induce hepatic inflammation or kidney dysfunction, as demonstrated by serological analysis. In conclusion, α-mannosyl-functionalized ManNP direct NP towards M2-type macrophages in diseased livers and prevent unspecific uptake in non-target cells. ManNP are promising vehicles for siRNA and other drugs for immunomodulatory treatment of liver fibrosis and liver cancer.

Aim: The semisynthetic derivatives MePip-SF5 and isogarcinol, which are aligned with the natural products curcumin and garcinol, were tested for their antitumor effects in a preclinical model of pulmonary melanoma metastasis. Methods and results: MePip-SF5 was almost five times more effective in inhibiting B16F10 melanoma cell proliferation than its original substance of curcumin (IC₅₀ MePip-SF5 2.8 vs. 13.8 µM). Similarly, the melanoma cytotoxicity of isogarcinol was increased by 40% compared to garcinol (IC₅₀ 3.1 vs. 2.1 µM). The in vivo toxicity of both drugs was assessed in healthy C57BL/6 mice challenged with escalating doses. Isogarcinol induced toxicity above a dose of 15 mg/kg, while MePip-SF5 showed no in vivo toxicity up to 60 mg/kg. Both drugs were tested in murine pulmonary metastatic melanoma. C57BL/6 mice (n = 10) received 500,000 B16F10 melanoma cells intravenously. After intraperitoneal injection of MePip-SF5 (60 mg/kg) or isorgarcinol (15 mg/kg) at days 8, 11 and 14 and sacrifice at day 16, the MePip-SF5-treated mice showed a significantly (p < 0.05) lower pulmonary macroscopic and microscopic tumor load than the vehicle-treated controls, whereas isogarcinol was ineffective. The pulmonary RNA levels of the mitosis marker Bub1 and the inflammatory markers TNFα and Ccl3 were significantly (p < 0.05) reduced in the MePip-SF5-treated mice. Both drugs were well tolerated, as shown by an organ inspection and normal liver- and kidney-related serum parameters. Conclusions: The novel curcuminoid MePip-SF5 showed a convincing antimetastatic effect and a lack of systemic toxicity in a relevant preclinical model of metastasized melanoma.

New 2-(thien-2-yl)-acrylonitriles with putative kinase inhibitory activity were prepared and tested for their antineoplastic efficacy in hepatoma models. Four out of the 14 derivatives were shown to inhibit hepatoma cell proliferation at (sub-)micromolar concentrations with IC₅₀ values below that of the clinically relevant multikinase inhibitor sorafenib, which served as a reference. Colony formation assays as well as primary in vivo examinations of hepatoma tumors grown on the chorioallantoic membrane of fertilized chicken eggs (CAM assay) confirmed the excellent antineoplastic efficacy of the new derivatives. Their mode of action included an induction of apoptotic capsase-3 activity, while no contribution of unspecific cytotoxic effects was observed in LDH-release measurements. Kinase profiling of cancer relevant protein kinases identified the two 3-aryl-2-(thien-2-yl)acrylonitrile derivatives 1b and 1c as (multi-)kinase inhibitors with a preferential activity against the VEGFR-2 tyrosine kinase. Additional bioinformatic analysis of the VEGFR-2 binding modes by docking and molecular dynamics calculations supported the experimental findings and indicated that the hydroxy group of 1c might be crucial for its distinct inhibitory potency against VEGFR-2. Forthcoming studies will further unveil the underlying mode of action of the promising new derivatives as well as their suitability as an urgently needed novel approach in HCC treatment.