Toshiaki Morihiro

Abstract 4747: Novel HER2-targeted gold nanoparticles; integration of antibody therapy and nanotechnology

Targeted therapies utilizing monoclonal antibodies for malignant tumors has been increasingly developed and applied to clinical practice. Trastuzumab (Tmab) is a humanized monoclonal antibody which binds to the human epidermal growth receptor 2 (HER2), which leads to strong antitumor effects by inducing antibody-dependent cell-mediated cytotoxicity (ADCC) and inhibiting HER2 signaling pathway. While Tmab is clinically applied to HER2-positive breast and gastric cancers, there still remain some issues such as low HER2 expression (only 20%) and resistance to Tmab. Recent progress in nanotechnology has brought significant benefits to medical fields. Gold nanoparticles (AuNPs), marked by the in vivo stability and easy surface functionalization, have been developed as therapeutic and contrast agents in the medical field, and some AuNPs reportedly show some cytotoxicity by inducing autophagy and apoptosis, which indicates that AuNPs could be attractive therapeutic agents in combination with tumor-targeting antibodies. In this study, we created Tmab-conjugated AuNPs and evaluated the antitumor effects on HER2-positive but Tmab-resistant gastric cancer cells (MKN7) and HER2-negative gastric cancer cells (MKN74) in addition to HER2-positive and Tmab-sensitive esophagogastric cancer cells (NCI-N87, TE4, OE19) in vitro and in vivo. IC50 dose of Tmab-AuNPs was 6.5 times smaller than free Tmab on NCI-N87 cells. Tmab-AuNPs exhibited stronger antitumor effects on MKN7, NCI-N87, TE4 and OE19, HER2-positive cells, than the other controls on XTT assay, but not such strong effects on MKN74 and NHLF, HER2-negative cells. Notably, Tmab-AuNPs showed potent antitumor effects even on MKN7, HER2-positive but Tmab-resistant cells. Moreover, once HER2 was overexpressed on MKN74 cells by Ad-HER2/ECD, Tmab-AuNPs became effective on artificially-HER2-overexpressed MKN74 cells. More effective intracellular uptake of Tmab-AuNPs was observed by dark field microscopy and transmission electron microscopy on HER2-positive cells, which seemed to cause stronger induction of oxidative stress, autophagy and apoptosis. Finally, stronger antitumor effects of Tmab-AuNPs were also confirmed in mouse subcutaneous xenograft models using HER2-positive cells. In conclusion, Tmab-AuNPs demonstrated potent antitumor effects on Tmab-resistant cells as well as Tmab-sensitive cells, and if combined with HER2/ECD overexpression, Tmab-AuNPs became effective even on HER2-negative cells. These findings suggest that Tmab-AuNPs could be promising HER2-targeted nanodrugs which were able to overcome shortcomings in Tmab-based therapy. Citation Format: Tetsushi Kubota, Shinji Kuroda, Toshiaki Morihiro, Hiroshi Tazawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. Novel HER2-targeted gold nanoparticles; integration of antibody therapy and nanotechnology. [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 4747.

HER2-targeted gold nanoparticles potentially overcome resistance to trastuzumab in gastric cancer

An issue of concern is that no current HER2-targeted therapeutic agent is effective against Trastuzumab (Tmab)-resistant gastric cancer. Gold nanoparticles (AuNPs) are promising drug carriers with unique characteristics of a large surface area available for attachment of materials such as antibodies. Here, we created HER2-targeted AuNPs (T-AuNPs) and examined their therapeutic efficacy and cytotoxic mechanisms using HER2-postive Tmab-resistant (MKN7) or Tmab-sensitive (NCI-N87) gastric cancer cell lines. In vitro, T-AuNPs showed stronger cytotoxic effects than controls against MKN7 and NCI-N87 cells although Tmab had no effect on MKN7 cells. Autophagy played an important role in T-AuNP cytotoxic mechanisms, which was considered to be driven by internalization of T-AuNPs. Finally, T-AuNPs displayed potent antitumor effects against NCI-N87 and MKN7 subcutaneous tumors in in vivo mouse models. In conclusion, HER2-targeted AuNPs with conjugated Tmab is a promising strategy for the development of novel therapeutic agents to overcome Tmab resistance in gastric cancer.

Liposome-encapsulated plasmid DNA of telomerase-specific oncolytic adenovirus with stealth effect on the immune system

Oncolytic virotherapy has the disadvantage of being unsuitable for systemic delivery due to immune elimination. Liposomal encapsulation is well-recognized to reduce immune elimination and enhance the stability of drugs in the bloodstream. In the present study, the potential of liposome-encapsulated plasmid DNA of telomerase-specific oncolytic adenovirus (TelomeScan) expressing GFP (Lipo-pTS) as an oncolytic adenoviral agent suitable for systemic delivery was investigated. Lipo-pTS, which has a diameter of 40–50 nm, showed potent antitumor effects on HCT116 colon carcinoma cells in vitro and in vivo. Tumor selectivity of Lipo-pTS was independent of coxsackie and adenovirus receptor (CAR). Importantly, Lipo-pTS reduced production of adenovirus-neutralizing antibodies (AdNAbs) after intravenous administration into immune-competent mice compared to TelomeScan, and even in the presence of AdNAbs, Lipo-pTS maintained strong cytotoxicity. In conclusion, Lipo-pTS has the potential to become an oncolytic adenoviral agent suitable for systemic delivery with the characteristics of CAR-independent antitumor activity and a stealth effect on the immune system.

Abstract 4717: Combination of PD-L1 expression and microsatellite instability status is a useful prognostic factor in gastric cancer

Interaction of programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) induces functional impairment of antigen-specific T cells, which leads to immune evasion of tumors. Immune checkpoint therapy including PD-1/PD-L1 blockade is an emerging treatment strategy which brings great improvement in patient’s prognosis. Microsatellite instability (MSI) is a condition of genomic instability caused by the loss of DNA mismatch repair activity, which has recently received a lot of attention from the standpoint of cancer immunotherapy. While the TNM classification system is commonly used on various malignant tumors for prediction of prognosis and planning of treatment strategy, establishment of prognostic factors related to cancer immune system is considered important as cancer immunotherapy has recently become more and more popular. Thus, we investigated the usefulness of PD-L1 expression and MSI status in addition to histological type as prognostic factors in gastric cancer. In this study, 255 gastric cancer cases which had curative surgical resection at Okayama University Hospital between 2002 and 2009 were analyzed retrospectively. PD-L1 expression level was classified into 4 groups according to PD-L1 positive rate on tumors on immunohistochemical staining (0: Citation Format: Toshiaki Morihiro, Shinji Kuroda, Nobuhiko Kanaya, Hiroshi Tazawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. Combination of PD-L1 expression and microsatellite instability status is a useful prognostic factor in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4717. doi:10.1158/1538-7445.AM2017-4717

Abstract 2649: PD-L1 expression as a predictive factor for recurrence pattern and prognosis in curatively resected gastric cancer

Interaction of programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) induces functional impairment of antigen-specific T cells, which leads to immune evasion of tumors. Immune checkpoint therapy including PD-1/PD-L1 blockade is an emerging treatment strategy which brings great improvement in patient9s prognosis. Many reports have mentioned that PD-L1 expression on tumors correlates with poor prognosis in various types of cancers. While there is a few report about correlation between PD-L1 expression and prognosis in gastric cancer, one of the most common cancers in the world especially in Asia, it still remains controversial. In addition, almost no report has referred to the correlation of PD-L1 expression with metastatic or recurrence pattern of cancers. Thus, we investigated the correlation of PD-L1 expression with prognosis and recurrence pattern in gastric cancer patients. In this study, 255 gastric cancer cases which had curative surgical resection at Okayama University Hospital between 2002 and 2009 were analyzed retrospectively in terms of correlation of PD-L1 expression on tumors with patient9s prognosis and recurrence pattern in addition to clinicophathological features. When PD-L1 expression was classified into 4 groups according to PD-L1 positive rate on tumors on immunohistochemical staining (0: Citation Format: TOSHIAKI MORIHIRO, Shinji Kuroda, Tetsushi Kubota, Hiroshi Tazawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. PD-L1 expression as a predictive factor for recurrence pattern and prognosis in curatively resected gastric cancer. [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 2649.