Makoto Asano

Eribulin mesylate reduces tumor microenvironment abnormality by vascular remodeling in preclinical human breast cancer models

Eribulin mesylate is a synthetic macrocyclic ketone analog of the marine sponge natural product halichondrin B and an inhibitor of microtubule dynamics. Some tubulin‐binding drugs are known to have antivascular (antiangiogenesis or vascular‐disrupting) activities that can target abnormal tumor vessels. Using dynamic contrast‐enhanced MRI analyses, here we show that eribulin induces remodeling of tumor vasculature through a novel antivascular activity in MX‐1 and MDA‐MB‐231 human breast cancer xenograft models. Vascular remodeling associated with improved perfusion was shown by Hoechst 33342 staining and by increased microvessel density together with decreased mean vascular areas and fewer branched vessels in tumor tissues, as determined by immunohistochemical staining for endothelial marker CD31. Quantitative RT‐PCR analysis of normal host cells in the stroma of xenograft tumors showed that eribulin altered the expression of mouse (host) genes in angiogenesis signaling pathways controlling endothelial cell–pericyte interactions, and in the epithelial–mesenchymal transition pathway in the context of the tumor microenvironment. Eribulin also decreased hypoxia‐associated protein expression of mouse (host) vascular endothelial growth factor by ELISA and human CA9 by immunohistochemical analysis. Prior treatment with eribulin enhanced the anti‐tumor activity of capecitabine in the MDA‐MB‐231 xenograft model. These findings suggest that eribulin‐induced remodeling of abnormal tumor vasculature leads to a more functional microenvironment that may reduce the aggressiveness of tumors due to elimination of inner tumor hypoxia. Because abnormal tumor microenvironments enhance both drug resistance and metastasis, the apparent ability of eribulin to reverse these aggressive characteristics may contribute to its clinical benefits.

Radiolabeled liposome imaging determines an indication for liposomal anticancer agent in ovarian cancer mouse xenograft models

Liposomal anticancer agents can effectively deliver drugs to tumor lesions, but their therapeutic effects are enhanced in only limited number of patients. Appropriate biomarkers to identify responder patients to these liposomal agents will improve their treatment efficacies. We carried out pharmacological and histopathological analyses of mouse xenograft models bearing human ovarian cancers (Caov‐3, SK‐OV‐3, KURAMOCHI, and TOV‐112D) to correlate the therapeutic effects of doxorubicin‐encapsulated liposome (Doxil®) and histological characteristics linked to the enhanced permeability and retention effect. We next generated 111In‐encapsulated liposomes to examine their capacities to determine indications for Doxil® treatment by single‐photon emission computed tomography (SPECT)/CT imaging. Antitumor activities of Doxil® were drastically enhanced in Caov‐3, moderately in SK‐OV‐3, and minimally in KURAMOCHI and TOV‐112D when compared to doxorubicin. Microvessel density and vascular perfusion were high in Caov‐3 and SK‐OV‐3, indicating a close relation with the enhanced antitumor effects. Next, 111In‐encapsulated liposomes were given i.v. to the animals. Their tumor accumulation and area under the curve values over 72 h were high in Caov‐3, relatively high in SK‐OV‐3, and low in two other tumors. Importantly, as both Doxil® effects and liposomal accumulation varied in the SK‐OV‐3 group, we individually obtained SPECT/CT images of SK‐OV‐3‐bearing mouse (n = 11) before Doxil® treatment. Clear correlation between liposomal tumor accumulation and effects of Doxil® was confirmed (R2 = 0.73). Taken together, our experiments definitely verified that enhanced therapeutic effects through liposomal formulations of anticancer agents depend on tumor accumulation of liposomes. Tumor accumulation of the radiolabeled liposomes evaluated by SPECT/CT imaging is applicable to appropriately determine indications for liposomal antitumor agents.

Microregional antitumor activity of a small-molecule hypoxia-inducible factor 1 inhibitor.

Hypoxia-inducible factor 1 (HIF-1) activates the transcription of genes that play crucial roles in the adaptation of cancer cells to hypoxia. HIF-1α overexpression has been associated with poor prognosis in patients with various types of cancer. Here, we describe ER-400583-00 as a novel HIF-1 inhibitor. ER-400583-00 suppressed the production of HIF-1α protein in response to hypoxia, with a half-maximal inhibitory concentration value of 3.7 nM in human U251 glioma cells. The oral administration of 100 mg/kg ER-400583-00 to mice bearing U251 tumor xenografts resulted in a rapid suppression of HIF-1α that persisted for 24 h. Immunohistochemical analysis revealed that ER-400583-00 suppressed the proliferation of cancer cells most prominently in areas distal to the region of blood perfusion, where HIF-1α-expressing hypoxic cancer cells were located. These hypoxic cancer cells were resistant to radiation therapy. ER-400583-00 showed a synergistic interaction with radiation therapy in terms of antitumor activity. These data suggest that HIF-1 blockade by small compounds may have therapeutic value in cancer, especially in combination with radiation therapy.

Antitumor effects of eribulin depend on modulation of the tumor microenvironment by vascular remodeling in mouse models

We previously reported that eribulin mesylate (eribulin), a tubulin‐binding drug (TBD), could remodel tumor vasculature (i.e. increase tumor vessels and perfusion) in human breast cancer xenograft models. However, the role of this vascular remodeling in antitumor effects is not fully understood. Here, we investigated the effects of eribulin‐induced vascular remodeling on antitumor activities in multiple human cancer xenograft models. Microvessel densities (MVD) were evaluated by immunohistochemistry (CD31 staining), and antitumor effects were examined in 10 human cancer xenograft models. Eribulin significantly increased MVD compared to the controls in six out of 10 models with a correlation between enhanced MVD levels and antitumor effects (R2 = 0.54). Because of increased MVD, we next used radiolabeled liposomes to examine whether eribulin treatment would result in increased tumoral accumulation levels of these macromolecules and, indeed, we found that eribulin, unlike vinorelbine (another TBD) enhanced them. As eribulin increased accumulation of radiolabeled liposomes, we postulated that this treatment might enhance the antitumor effect of Doxil (a liposomal anticancer agent) and facilitate recruitment of immune cells into the tumor. As expected, eribulin enhanced antitumor activity of Doxil in a post‐erlotinib treatment H1650 (PE‐H1650) xenograft model. Furthermore, infiltrating CD11b‐positive immune cells were significantly increased in multiple eribulin‐treated xenografted tumors, and natural killer (NK) cell depletion reduced the antitumor effects of eribulin. These findings suggest a contribution of the immune cells for antitumor activities of eribulin. Taken together, our results suggest that vascular remodeling induced by eribulin acts as a microenvironment modulator and, consequently, this alteration enhanced the antitumor effects of eribulin.

Abstract 1413: Eribulin caused re-modeling of tumor vasculature altering gene expression profiling in angiogenesis and Epithelial Mesenchymal Transition (EMT) signaling pathway of host cells within human breast cancer cell (BCC) xenografts in nude mice.

Objective: Eribulin mesylate (ERI) is a synthetic macrocyclic ketone analog of the marine sponge natural product halichondrin B and an inhibitor of microtubule dynamics. The objective of this study was to examine the effect of ERI on tumor vasculature with immunohistchemical (IHC) analysis and gene expression profiling (GEP) in normal host cells, such as endothelial cells and vascular mural cells within tumor microenvironments in human BCC xenograft models Methods: Anti-tumor activity of ERI was examined at doses of 1.5 and 3.0 mg/kg, i.v. at day 1, in human BCC MX-1, MDA-MB-231 and MDA-MB-453 sc xenografts in nude mice. For IHC and GEP analysis, tumor tissues were collected at day 4 and day 8. IHC analysis was performed using mouse CD31 antibody to stain endothelial cells. Microvessel density (MVD) and vessel perimeter were determined by using Aperio Image Scope. GEP analysis for mouse host and human tumor cells within tumor tissues was done by using mouse and human TaqMan Low Density Arrays (TLDAs) consisting of a set of 92 genes related to angiogenesis, metastasis/EMT and cell differentiation signal pathways. Results shows % of non-treatment group (NT). Results: ERI showed significant anti-tumor activity against all three human BCC xenografts in a dose dependent manner. IHC analysis showed that ERI altered morphology of tumor vasculature day 8 after treatments and increased number of vessels with small size of perimeter ( 300um) in both MX-1 and MDA-MB-231 xenograft models (p Conclusions: ERI induced re-modeling of tumor vasculature in human BCC xenograft models. GEP related to angiogenesis and EMT/metastasis pathway was significantly affected with ERI treatment in host cells under tumor microenvironments. ERI might cause remodeling of tumor vasculature by regulating GEP in host cells. Further investigation may be warranted to examine if the activity of ERI against host cells in tumor tissues contributed to anti-tumor activity of ERI. Citation Format: Junji Matsui, Osamu Toyama, Mitsuhiro Ino, Taro Semba, Mai Uesugi, Hiroki Muto, Judith L. Oestreicher, Kentaro Takahashi, Kentaro Matsuura, Yoshiaki Sato, Taisuke Uehara, Takayuki Kimura, Hideki Watanabe, Yoichi Ozawa, Makoto Asano, Yusuke Adachi, Ken Aoshima, Yasuhiro Funahashi. Eribulin caused re-modeling of tumor vasculature altering gene expression profiling in angiogenesis and Epithelial Mesenchymal Transition (EMT) signaling pathway of host cells within human breast cancer cell (BCC) xenografts in nude mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1413. doi:10.1158/1538-7445.AM2013-1413

Abstract 344: Antimitotic effect and complex of nonmitotic effect on tumor biology of eribulin mesilate in soft tissue sarcoma model

Background and objectives: Eribulin mesilate (Eribulin), a first-in-class halichondrin B-based microtubule dynamics inhibitor, has been shown to have novel mechanism of actions (reversion of epithelial-mesenchymal transition of tumor cell and promotion of vascular remodeling) beyond its established antimitotic activity in breast cancer models, leading to decrease of tumor metastatic potency. Recently, eribulin showed trends towards greater overall survival compared to Dacarbazine in subjects with leiomyosarcoma and liposarcoma patients in phase 3 trial. The objective of this study was to investigate the effect of eribulin on tumor cell proliferation of soft tissue sarcoma (STS). Furthermore, the effects of eribulin on morphology and gene expression of differentiation markers against STS and tumor blood perfusion in a leiomyosarcoma xenograft model were examined. Methods: Anti-proliferation activity of eribulin was examined in 6 human STS cell lines. Anti-tumor activity of eribulin was examined in xenografts of A-673 (Ewing9s sarcoma), SK-LMS-1 (leiomyosarcoma), SW 872 (liposarcoma), and HT-1080 (fibrosarcoma) at several doses. To analyze the effect of eribulin on in vitro morphological change, 3 human STS cell lines were treated with eribulin at 1, 3, and 10 nmol/L for 7 days. Gene expression change was analyzed by microarray and differentiation marker genes in 2 cell lines were confirmed by qPCR analysis. For tumor blood perfusion analysis, eribulin was administered at doses of 0.38, 0.75, and 1.5 mg/kg one shot in SK-LMS-1 xenografts, and tumor blood perfusion was calculated as Hoechst-positive areas in tumor cryosections 5 days after the administration. Results: Eribulin showed anti-proliferation activity in vitro against all 6 cell lines in a dose dependent manner with 50% inhibitory concentration values of around 1 nmol/L. Eribulin showed significant antitumor activity against 4 xenografts in a dose dependent manner. Eribulin treatment for 7 days induced apparent morphological change in 3 cell lines. Of these, expression level of smooth muscle differentiation marker gene CNN1 was 7.1-fold upregulated in SK-UT-1 and adipocyte differentiation marker genes MYLK, C/EBPβ, and KIF23 were 1.9-, 1.4-, and 1.3-fold upregulated in SW 872, respectively, by 10 nmol/L treatment compared to vehicle control. In addition, eribulin significantly enhanced tumor blood perfusion compared to vehicle control 5 days after the administration in SK-LMS-1 xenografts at all doses.Conclusions: Eribulin showed anti-proliferation activity against all of STS cell lines we tested in vitro and in vivo. Furthermore, eribulin might cause differentiation of STS cells and remodeling of tumor vasculature to enhance tumor blood perfusion. These data supported that eribulin showed mitotic effect and non-mitotic effect, which may decrease tumor metastatic potency in STS, as well in breast cancer. Citation Format: Satoshi Kawano, Makoto Asano, Yusuke Adachi, Junji Matsui. Antimitotic effect and complex of nonmitotic effect on tumor biology of eribulin mesilate in soft tissue sarcoma model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 344.

Abstract 4543: Characterization of the liposomal formulation of eribulin mesylate (E7389) in mice

E7389 (eribulin mesylate, Halaven, Eisai) is a fully synthetic analog of the marine sponge natural product halichondrin B. It has been approved in US and more than 50 countries worldwide for treatment of advanced breast cancer. To improve the therapeutic index of E7389, a liposomal formulation of E7389, E7389-LF is under development. In this study, we characterized the pharmacokinetics of E7389-LF and E7389 (aqueous formulation) in mice and evaluated the anti-tumor activity of E7389-LF and E7389 in mouse xenograft model. In general the pharmacokinetics of E7389-LF was characterized by a small volume of distribution, slow clearance, and slow elimination in all liposomal formulations tested. Plasma AUC of E7389-LF was more than 600 fold larger than that of E7389 in tumor bearing mice. Tumor AUC of E7389-LF was also observed. Moreover, free E7389 (not liposome encapsulated and not protein bound) was measured in mouse plasma by ultracentrifugation method. The concentration ratio of E7389 in ultracentrifuged mouse plasma (UCM) vs E7389 in plasma after a 2 mg/kg i.v. of E7389 ranged from 54.19% to 65.41%, which was similar to the free fraction in the mouse plasma. The respective concentration ratio of E7389 in UCM vs E7389 in plasma after a 2 mg/kg i.v. of E7389-LF ranged from 0.07% to 0.59%, and the exposure, expressed as AUC, of UCM/plasma ratio was determined to be 0.2%. The free E7389 exposure, measured by UCM, after E7389-LF administration was about 1.5 fold of that after E7389 administration. Anti-tumor activity of E7389-LF and E7389 was evaluated in a human pharynx carcinoma, FaDu, xenograft model. E7389-LF showed dose-dependent anti-tumor effect with regression of tumors at 2.5 mg/kg dose, which was significantly better than that after E7389 administration in this model. These findings suggest that E7389-LF showed better anti-tumor activity than that of E7389 in human FaDu xenograft mouse model. Citation Format: Makoto Asano, Kenji Hyodo, Yanke Yu, Edgar Schuck, Junji Matsui, Hiroshi Ishihara, Hiroshi Kikuchi, Kenichi Nomoto. Characterization of the liposomal formulation of eribulin mesylate (E7389) in mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4543. doi:10.1158/1538-7445.AM2015-4543