No abstract

Delivery of anticancer drugs into tumor cores comprised of malignant cancer cells can result in potent therapeutic effects. However, conventional nanoparticle-based drug delivery systems used for cancer therapy often exhibit inefficient tumor-penetrating properties, thus, suggesting the need to improve the functional design of such systems. Herein, we focus on the interactions between cancer cells and the extracellular matrix (ECM) and demonstrate that liposomes modified with slightly acidic pH-sensitive peptide (SAPSp-lipo) can penetrate in vivo tumor tissue and in vitro spheroids comprised of cancer cells and ECM. We previously reported SAPSp-lipo, tumor microenvironment-sensitive liposomes, are effectively delivered to tumor tissue (Hama et al. J Control Release 2015, 206, 67-74). Compared with conventional liposomes, SAPSp-lipo could be delivered to deeper regions within both spheroids and tumor tissues. Furthermore, tumor penetration was found to be promoted at regions where actin depolymerization was induced by SAPSp-lipo and inhibited by the polymerization of actin. In addition, SAPSp-lipo attenuated the interaction between cancer cells and ECM, contributing to the penetration of SAPSp-lipo. These results suggest that SAPSp-lipo penetrates tumors via the interspace route and is accompanied by actin depolymerization. Taken together, SAPSp-lipo demonstrates potential as a novel tumor-penetrable drug carrier for induction of therapeutic effects against malignant cells that comprise tumor cores.

Intraperitoneal administration of anticancer nanoparticles is a rational strategy for preventing peritoneal dissemination of colon cancer due to the prolonged retention of nanoparticles in the abdominal cavity. However, instability of nanoparticles in body fluids causes inefficient retention, reducing its anticancer effects. We have previously developed anticancer nanoparticles containing tocopheryl succinate, which showed high in vivo stability and multifunctional anticancer effects. In the present study, we have demonstrated that peritoneal dissemination derived from colon cancer was prevented by intraperitoneal administration of tocopheryl succinate nanoparticles. The biodistribution of tocopheryl succinate nanoparticles was evaluated using inductively coupled plasma mass spectroscopy and imaging analysis in mice administered quantum dot encapsulated tocopheryl succinate nanoparticles. Intraperitoneal administration of tocopheryl succinate nanoparticles showed longer retention in the abdominal cavity than by its intravenous (i.v.) administration. Moreover, due to effective biodistribution, tumor growth was prevented by intraperitoneal administration of tocopheryl succinate nanoparticles. Furthermore, the anticancer effect was attributed to the inhibition of cancer cell proliferation and improvement of the intraperitoneal microenvironment, such as decrease in the levels of vascular endothelial growth factor A, interleukin 10, and M2‐like phenotype of tumor‐associated macrophages. Collectively, intraperitoneal administration of tocopheryl succinate nanoparticles is expected to have multifaceted antitumor effects against colon cancer with peritoneal dissemination.

The level of lipocalin 2 (LCN2), a secreted protein of the lipocalin superfamily, increases in various tumors. Moreover, LCN2 is known to promote tumor progression with the hypoxia inducible factor-1α (HIF-1α)-mediated epithelial mesenchymal transition and angiogenesis. However, the mechanism of LCN2-induced HIF-1α activation is not fully understood. In the present study, we examined the effect of LCN2 on HIF-1α activation in the normoxic cancer cells that HIF-1α is immediately degraded. A mouse melanoma cell line, B16-F1, was treated with recomninant LCN2 protein under normoxic condition. After the treatment, the protein level and nuclear translocation of HIF-1α were examined by western blot and immunohistochemical staining, respectively. Moreover, the activation of HIF-1α was evaluated by reporter gene assay in the cells transfected with the plasmid DNA containing HIF-1α response element. The intracellular iron was quantified by iron colorimetric assay kit. In the B16-F1 cells treated with LCN2, HIF-1α protein was not degraded and its nuclear translocation was observed even under normoxic condition, suggesting that LCN2 stabilizes HIF-1α in normoxic cancer cells. Moreover, the HIF-1α-mediated transcriptional activity in the B16-F1 cells treated with LCN2 was significantly higher than those with non-treatment, suggesting that LCN2 activates HIF-1α in normoxic cancer cells. Next, to clarify the mechanism of LCN2-mediated HIF-1α activation, we hypothesized that LCN2, which is an Fe3+ transport protein, stabilizes HIF-1α by preventing the activity of proline hydroxylase (PHD) as a primary enzyme of HIF-1α degradation, because the increase of intracellular Fe3+ is known to inhibit PHD activity. As a result, the intracellular iron increased in the cells treated with LCN2 protein. Moreover, the level of HIF-1α by co-treatment of LCN2 with FeCl3 was higher than that only by LCN2 treatment. Collectively, LCN2-mediated Fe3+ influx stabilizes HIF-1α in normoxic cancer cells. Citation Format: Susumu Hama, Ibuki Nakamura, Akinori Nishimoto, Takayuki Nishi, Shoko Itakura, Kentaro Kogure. Lipocalin2 stabilizes hypoxia inducible factor-1α through the iron delivery into normoxic cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A202.