Annual Report 2017

Koji Okamoto, Daisuke Shiokawa, Yuki Obata, Hirokazu Ohata, Toshiaki Miyazaki, Kaoru Yamawaki, Ai Sato, Hiroaki Sakai, Seiko Ogawa, Katsuya Yokoyama, Mayu Fukami, Masahiro Takahashi

Introduction

 Cancer stem cells (CSCs) are regarded to be responsible for the refractory nature of cancer, such as the capability for metastasis or chemoresistance. In order to understand biology of CSCs from solid tumors, we have established the in vitro 3D culture of colon and ovarian CSCs, and try to find out weakness of CSCs that can be targeted for therapeutic purposes. We also use the established CSCs to generate a patient-derived xenograft tumor to elucidate mechanism of chemoresistance. By integrating data from genomic and gene expression analyses and sensitivity data for chemotherapy compounds, we are in the process of establishing a comprehensive panel of the 3D culture cells, which will be instrumental for stratifying the clinical cases and devise the strategy for the personalized medicine.

Our team and what we do

 We perform basic research to understand the refractory nature of cancer and to devise the effective diagnosis and therapy. We mainly use the 3D culture from clinical specimens and its PDX models.

Research activities

1. Identification of essential pathways of CSC proliferation

 Using the cultivated CSCs under in vitro spheroid culture derived from clinical specimens of colon cancer, we demonstrated that activation of mTORC1 by reactive oxygen species (ROS) is crucial for the proliferation and maintenance of colon CSCs, and that ROS is produced by NADPH

oxidase. Furthermore, we demonstrated that ROS-dependent activation of mTORC1 was

mediated by several calcium binding proteins. In addition, we performed metabolome analyses of the spheroid culture from different clinical samples, and identified some metabolites that are abundant in CSCs from liver metastasis.

2. Stratification of colon cancer spheroids via OMICS and systemic chemosensitivity analyses

 We performed several OMICS analyses (RNA-seq, NCC Oncopanel, and metabolome analyses) as well as chemosensitivity analyses using more than hundred chemotherapeutic compounds. Through integrative analyses of these data, we stratified the above-mentioned spheroids into several groups. This information will be invaluable for predicting efficacy of chemotherapeutic compounds.

3. Understanding cancer heterogeneity via single cell analyses of colon PDX tumors

 Through the transplantation of the in vitro cultivated CSCs into immuno-deficient NOG mice, we established in vivo models of colon and ovarian cancer (PDX models). We utilized these models to study chemoresistance by treating

tumor-transplanted mice with chemotherapeutic compounds. By applying single-cell gene expression analyses, cellular heterogeneity of xenograft tumors and identity of chemo-resistant cells were examined. A similar approach to study cellular heterogeneity of cancer was applied for mouse models of inflammation-associated colon cancer in ApcMin/+ mice.

Education

 Teaching students (one undergraduate students, two graduate students) was conducted.

Future prospects

 We intend to translate the acquired information on CSCs into clinical practice by targeting "Achelles' Heel" of CSCs to eradicate refractory cancer.

List of papers published in January 2017 - March 2018

Journal

1. Ishiguro T, Ohata H, Sato A, Yamawaki K, Enomoto T, Okamoto K. Tumor-derived spheroids: Relevance to cancer stem cells and clinical applications. Cancer Sci, 108:283-289, 2017

2. Shiokawa D, Okamoto K. Heterogeneity among Lgr5-positive colon stem cells. Molecular & cellular oncology, 4:e1335271, 2017

3. Shiokawa D, Sato A, Ohata H, Mutoh M, Sekine S, Kato M, Shibata T, Nakagama H, Okamoto K. The Induction of Selected Wnt Target Genes by Tcf1 Mediates Generation of Tumorigenic Colon Stem Cells. Cell Rep, 19:981-994, 2017

4. Nishiumi S, Kobayashi T, Kawana S, Unno Y, Sakai T, Okamoto K, Yamada Y, Sudo K, Yamaji T, Saito Y, Kanemitsu Y, Okita NT, Saito H, Tsugane S, Azuma T, Ojima N, Yoshida M. Investigations in the possibility of early detection of colorectal cancer by gas chromatography/triple-quadrupole mass spectrometry. Oncotarget, 8:17115-17126, 2017

5. Yamawaki K, Ishiguro T, Mori Y, Yoshihara K, Suda K, Tamura R, Yamaguchi M, Sekine M, Kashima K, Higuchi M, Fujii M, Okamoto K, Enomoto T. Sox2-dependent inhibition of p21 is associated with poor prognosis of endometrial cancer. Cancer Sci, 108:632-640, 2017

6. Okumura T, Ikeda K, Ujihira T, Okamoto K, Horie-Inoue K, Takeda S, Inoue S. Proteasome 26S subunit PSMD1 regulates breast cancer cell growth through p53 protein degradation. J Biochem, 163:19-29, 2018