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Tumor blood vessels play important roles in tumor progression and metastasis. Targeting tumor endothelial cells (TECs) is one of the strategies for cancer therapy. We previously reported that biglycan, a small leucine-rich proteoglycan, is highly expressed in TECs. TECs utilize biglycan in an autocrine manner for migration and angiogenesis. Furthermore, TEC-derived biglycan stimulates tumor cell migration in a paracrine manner leading to tumor cell intravasation and metastasis. In this study, we explored the therapeutic effect of biglycan inhibition in the TECs of renal cell carcinoma using an in vivo siRNA delivery system known as a multifunctional envelope-type nanodevice (MEND), which contains a unique pH-sensitive cationic lipid. To specifically deliver MEND into TECs, we incorporated cyclo(Arg-Gly-Asp-D-Phe-Lys) (cRGD) into MEND because alpha(V)beta(3) integrin, a receptor for cRGD, is selective and highly expressed in TECs. We developed RGD-MEND-encapsulating siRNA against biglycan. First, we confirmed that MEND was delivered into OS-RC-2 tumor-derived TECs and induced in vitro RNAi-mediated gene silencing. MEND was then injected intravenously into OS-RC-2 tumor-bearing mice. Flow cytometry analysis demonstrated that MEND was specifically delivered into TECs. Quantitative RT-PCR indicated that biglycan was knocked down by biglycan siRNA-containing MEND. Finally, we analyzed the therapeutic effect of biglycan silencing by MEND in TECs. Tumor growth was inhibited by biglycan siRNA-containing MEND. Tumor microenvironmental factors such as fibrosis were also normalized using biglycan inhibition in TECs. Biglycan in TECs can be a novel target for cancer treatment.

Tumor blood vessels play important roles in tumor progression and metastasis. Targeting tumor endothelial cells (TECs) is one of the strategies for cancer therapy. We previously reported that biglycan, a small leucine-rich proteoglycan, is highly expressed in TECs. TECs utilize biglycan in an autocrine manner for migration and angiogenesis. Furthermore, TEC-derived biglycan stimulates tumor cell migration in a paracrine manner leading to tumor cell intravasation and metastasis. In this study, we explored the therapeutic effect of biglycan inhibition in the TECs of renal cell carcinoma using an in vivo siRNA delivery system known as a multifunctional envelope-type nanodevice (MEND), which contains a unique pH-sensitive cationic lipid. To specifically deliver MEND into TECs, we incorporated cyclo(Arg-Gly-Asp-D-Phe-Lys) (cRGD) into MEND because alpha(V)beta(3) integrin, a receptor for cRGD, is selective and highly expressed in TECs. We developed RGD-MEND-encapsulating siRNA against biglycan. First, we confirmed that MEND was delivered into OS-RC-2 tumor-derived TECs and induced in vitro RNAi-mediated gene silencing. MEND was then injected intravenously into OS-RC-2 tumor-bearing mice. Flow cytometry analysis demonstrated that MEND was specifically delivered into TECs. Quantitative RT-PCR indicated that biglycan was knocked down by biglycan siRNA-containing MEND. Finally, we analyzed the therapeutic effect of biglycan silencing by MEND in TECs. Tumor growth was inhibited by biglycan siRNA-containing MEND. Tumor microenvironmental factors such as fibrosis were also normalized using biglycan inhibition in TECs. Biglycan in TECs can be a novel target for cancer treatment.

The world-first success of lipid nanoparticle (LNP)-based siRNA therapeutics (ONPATTRO(R)) promises to accelerate developments in siRNA therapeutics/gene therapy using LNP-type drug delivery systems (DDS). In this study, we explore the optimal composition of an LNP containing a self-degradable material (ssPalmO-Phe) for the delivery of oligonucleotides. siRNA or antisense oligonucleotides (ASO) were encapsulated in LNP with different lipid compositions. The hepatic knockdown efficiency of the target genes and liver toxicity were evaluated. The optimal compositions for the siRNA were different from those for ASO, and different from those for mRNA that were reported in a previous study. Extracellular stability, endosomal escape and cellular uptake appear to be the key processes for the successful delivery of mRNA, siRNA and ASO, respectively. Moreover, the compositions of the LNPs likely contribute to their toxicity. The lipid composition of the LNP needs to be optimized depending on the type of nucleic acids under consideration if the applications of LNPs are to be further expanded.

For achieving efficient cancer treatment, it is important to elucidate the mechanism responsible for the accumulation of nanoparticles in tumor tissue. Recent studies suggest that nanoparticles are not delivered merely through gaps between tumor endothelial cells. We previously reported that the maturation of the vascular structure by the vascular endothelial cell growth factor receptor 2 (VEGFR2) using a previously developed siRNA delivery technology (RGD-MEND) significantly enhanced the accumulation of nanoparticles in types of cancers that area vessel-rich (renal cell carcinoma). This result was completely inconsistent with the generally accepted theory of the enhanced permeability and retention (EPR) effect. We hypothesized that a caveolin-1 (Cav1)-mediated transcellular route would be involved with the penetration of nanoparticles into tumor vasculature. To reveal the exact mechanism responsible for this enhancement, we observed the delivery of long-circulating liposomes (LPs) after Cav1 was co-suppressed by RGD-MEND with VEGFR2. The enhanced delivery of LPs by siRNA against VEGFR2 (siVEGFR2) was accompanied by the elevated expression of the Cav1 protein. In addition, Cav1 knockdown by siRNA against Cav1 (siCav1) canceled the enhanced delivery of LPs by siVEGFR2. The injection of siCav1 had no effect on the formation of alpha smooth muscle actin or vascular endothelial cell adhesion molecules. These results suggest that a Cav1-induced transcellular route and not a paracellular route, at least partially, contributes to the accumulation of nanoparticles in tumors. (C) 2020 Elsevier Inc. All rights reserved.

For achieving efficient cancer treatment, it is important to elucidate the mechanism responsible for the accumulation of nanoparticles in tumor tissue. Recent studies suggest that nanoparticles are not delivered merely through gaps between tumor endothelial cells. We previously reported that the maturation of the vascular structure by the vascular endothelial cell growth factor receptor 2 (VEGFR2) using a previously developed siRNA delivery technology (RGD-MEND) significantly enhanced the accumulation of nanoparticles in types of cancers that area vessel-rich (renal cell carcinoma). This result was completely inconsistent with the generally accepted theory of the enhanced permeability and retention (EPR) effect. We hypothesized that a caveolin-1 (Cav1)-mediated transcellular route would be involved with the penetration of nanoparticles into tumor vasculature. To reveal the exact mechanism responsible for this enhancement, we observed the delivery of long-circulating liposomes (LPs) after Cav1 was co-suppressed by RGD-MEND with VEGFR2. The enhanced delivery of LPs by siRNA against VEGFR2 (siVEGFR2) was accompanied by the elevated expression of the Cav1 protein. In addition, Cav1 knockdown by siRNA against Cav1 (siCav1) canceled the enhanced delivery of LPs by siVEGFR2. The injection of siCav1 had no effect on the formation of alpha smooth muscle actin or vascular endothelial cell adhesion molecules. These results suggest that a Cav1-induced transcellular route and not a paracellular route, at least partially, contributes to the accumulation of nanoparticles in tumors. (C) 2020 Elsevier Inc. All rights reserved.