１．機能未知遺伝子産物の機能性解明

Elucidation of the functionality of unknown gene products

　ヒトにおいて身体を構成するタンパク質は約10万種類あり、そのうちの約半数は酵素だと考えられています。ヒトのゲノムは約20年前にすべて解読されましたが、いまだこれらの酵素の中には機能が不明なものがたくさん残されています。また、創薬研究を行う上で実験動物を用いた試験が行われますが、このような実験動物においても対応する遺伝子産物の機能の理解が不十分であることで、外挿性を正確に予想することが困難な場合が少なくありません。そのため、汎用実験動物における機能未知遺伝子産物の機能性の解明を行っています。

　In humans, approximately 100,000 proteins make up the body, and about half of them are estimated to be enzymes. Although the human genome was fully decoded approximately 20 years ago, many of these enzymes still have unknown functions. Furthermore, in drug discovery research, experiments using experimental animals are conducted. Still, understanding the functions of corresponding gene products in these experimental animals is often insufficient, making it difficult to predict extrapolation accurately. Therefore, we are working to elucidate the functionality of genes with unknown functions in common experimental animals. 

 (A) 異種臓器移植に向けたnon-human酵素の性状解析

Characterization of non-human enzymes for xenotransplantation

 【Representative Papers】

1.  Endo, S.*, Morikawa, Y., Suenami,　K., Sakai,　Y., Abe, N., Matsunaga, T., Hara, A. and Takasu, M., Involvement of porcine and human carbonyl reductases in the metabolism of epiandrosterone, 11-oxygenated steroids, neurosteroids, and corticosteroids. J. Steroid Biochem. Mol. Biol., 243, 106574 (2024)

2. Endo, S.*, Morikawa, Y., Matsunaga, T., Hara, A. and Takasu, M., Characterization of a novel porcine carbonyl reductase activated by glutathione: Relationship to carbonyl reductase 1, 3α/β-hydroxysteroid dehydrogenase and prostaglandin 9-ketoreductase. Chem. Biol. Interact., 381, 110572 (2023)

3. Endo, S.*, Morikawa, Y., Matsunaga, T., Hara, A. and Nishinaka, T., Porcine aldo-keto reductase 1C subfamily members AKR1C1 and AKR1C4: Substrate specificity, inhibitor sensitivity and activators. J. Steroid Biochem. Mol. Biol., 221, 106113 (2022)

4. Endo, S.*, Matsunaga, T. and Hara,　A., Characterization of aldo-keto reductase 1C subfamily members encoded in two rat genes (akr1c19 and RGD1564865). Relationship to 9-hydroxyprostaglandin dehydrogenase. Arch. Biochem. Biophys., 700, 108755 (2020)

２．疾患の予防医学の確立に向けた天然機能性分子や治療薬の開発

Development of natural functional molecules and therapeutics to establish preventive medicine for diseases

　我が国は超高齢化にあり、2021年には65歳以上人口が3600万人を超え、総人口に占める割合は30%に達しようとしています。さらには、2040年には約35%にまで上昇する見通しがされています。この背景には平均寿命の延伸があり、2019年には男性で81.41歳、女性で87.45歳となっています。一方で、健康寿命は男性で72.68歳、女性で75.38歳と、平均寿命との間に約10歳の開きが存在します。この10年間は病気と戦い、時には共生しながら人生を送ることになります。そこで、がん、神経変性疾患や生活習慣病の予防や再発防止を可能にする天然機能性分子や治療薬の開発を目指しています。

　Japan is experiencing a rapid increase in its aging population. In 2021, the number of people aged 65 and over exceeded 36 million, accounting for 30% of the total population. This proportion is expected to rise to about 35% by 2040. This trend is mainly due to the extension of the average lifespan, which was 81.41 years for men and 87.45 years for women in 2019. However, healthy life expectancy is significantly lower, at 72.68 years for men and 75.38 years for women, creating a gap of about 10 years. This means that many people will spend a decade battling diseases while trying to live their lives to the fullest. To address these challenges, we are focused on developing natural functional molecules and treatments that can prevent and manage diseases such as cancers, neurodegenerative disorders, and lifestyle-related diseases.

(B) がんの予防と治療に向けた天然由来成分の機能性開発

Development of functionality of natural compounds for cancer prevention and treatment

【Representative Papers】

1.  Kawai, M.#, Saka, T.# (#Equal first author contribution), Kawano, S., Kudo, Y., Nomura, T.K., Honda, R., Yoshino, Y., Kashiwagi, H., Abe, N., Oyama, M., Ikari, A. and Endo, S.*, Gnetin C Sensitizes Darolutamide-Resistant Prostate Cancer Cells by Targeting NAD+ and Energy Metabolism. Biochem. Biophys. Res. Commun., 770, 152009 (2025)

2. Ota, A.#, Kawai, M.# (#Equal first author contribution), Kudo, Y., Segawa, J., Hoshi, M., Kawano, S., Yoshino, Y., Ichihara, K., Shiota, M., Fujimoto, N., Matsunaga, T., Endo, S.* and Ikari, A., Artepillin C overcomes apalutamide resistance through blocking androgen signaling in prostate cancer cells. Arch. Biochem. Biophys., 735, 109519 (2023)

3. Endo, S.*, Hoshi, M., Matsunaga, T., Inoue, T., Ichihara, K. and Ikari, A., Autophagy inhibition enhances anticancer efficacy of artepillin C, a cinnamic acid derivative in Brazilian green propolis. Biochem. Biophys. Res. Commun., 497, 437-443 (2018)

(C) 植物由来成分の機能性の開発

Development of functional properties of plant-derived ingredients

【Representative Papers】

1. Kudo, Y., Endo, S.*, Tanio, M., Saka, T., Himura, R., Abe, N., Takeda, M., Yamaguchi, E., Yoshino, Y., Arai, Y., Kashiwagi, H., Oyama, M., Itoh, A., Shiota, M., Fujimoto, N. and Ikari, A. Antiandrogenic effects of a polyphenol in Carex kobomugi through inhibition of androgen synthetic pathway and down-regulation of androgen receptor in prostate cancer cell lines. Int. J. Mol. Sci., 23, 14356 (2022)

2. Endo, S.*, Matsuoka, T., Nishiyama, T., Arai, Y., Kashiwagi, H., Abe, N., Oyama, M., Matsunaga, T. and Ikari, A., Transient decreases in intestinal barrier function by fravonol glycosides from Rosa multiflora. Nutr. Res., 72, 92-104 (2019)

(D) 選択的にオートファジーを阻害するAtg4B阻害剤の開発

Development of Atg4B inhibitors that selectively suppress autophagy

【Representative Papers】

1. Kudo, Y., Nakamura, K., Tsuzuki, H., Hirota, K., Takaya, D., Fukuzawa, K., Honma, T., Yoshino, Y., Nakamura, M., Shiota, M., Fujimoto, N., Ikari, A. and Endo, S.*, Long chain fatty acids enhance the efficacy of treatments for castration-resistant prostate cancer by autophagy inhibition via Atg4B inhibition. Arch. Biochem. Biophys., 760, 110135 (2024)

2. Kudo, Y., Endo, S.*, Fujita, M., Ota, A., Kamatari, Y.O., Tanaka, Y., Ishikawa, T., Ikeda, H., Okada, T., Toyooka, N., Fujimoto, N., Matsunaga, T. and Ikari, A., Discovery and structure-based optimization of novel Atg4B inhibitors for the treatment of castration-resistant prostate cancer. J. Med. Chem., 65, 4878-4892 (2022)

3. Endo, S.*, Uchibori, M., Suyama, M., Fujita M., Arai, Y., Hu, D., Xia, S., Ma, B., Kabir, A., Kamatari, O.Y., Kuwata, K., Toyooka, N., Matsunaga T. and Ikari, A., Novel Atg4B inhibitors potentiate cisplatin therapy in lung cancer cells through blockade of autophagy. Comput. Toxicol., 12, 100095 (2019)

３．細胞内“ごみ”の運命の理解

Understanding the fate of intracellular “unwanted materials”

　細胞の成分の約70%を占めるタンパク質の恒常性 (プロテオスタシス) の維持は老化を原因の一つとするがんや神経変性疾患の予防や治療において重要です。細胞内では常に異常タンパク質や異常オルガネラといった細胞内ごみが発生しているが、ユビキチン/プロテアソーム系 (UPS) とオートファジー/リソソーム系 (ALS) で適切に処理することで細胞内恒常性が維持されています。プロテオスタシス制御機構の低下に伴う不良タンパク質の蓄積が神経変性疾患の発症につながる一方で、がん細胞では正常細胞と比べてUPSやALSが過剰に亢進しています。そのため、がん細胞のプロテオスタシス制御機構の破綻は、積極的な“ごみ”蓄積によって効果的にがん細胞死を誘導できると期待されます。これまでに、ALS阻害剤やUPS阻害剤が、抗がん剤の作用増強効果や抗がん剤耐性克服効果を示すことを明らかにしてきましたが、『①ALSとUPSを阻害した際に、異なる“ごみ”が異なる“場所”に蓄積すると想定されるが、細胞に与える影響は同一なのか？』と『②オートファゴソーム膜形成を阻害してごみを細胞内に散乱させているAtg4B阻害剤と、“ごみ”を分解できずオートファゴソーム膜で内包させたままにしているリソソーム阻害剤の細胞毒性 (抗がん活性) 及び毒性発現機構は同一なのか？』という2つの疑問が生じました。これらを解決することによって、細胞内”ごみ”の運命を理解し、その制御を目指しています。将来的には、これらの阻害剤が臨床応用される際の主作用だけでなく副作用の理解にもつながると考えています。

Maintaining the homeostasis of proteins, which account for about 70% of cell components, known as proteostasis, is crucial for preventing and treating cancer and neurodegenerative diseases, which are considered causes of aging. Cells constantly generate intracellular unwanted materials, such as abnormal proteins and organelles, which are appropriately processed by the ubiquitin-proteasome system (UPS) and autophagy-lysosome system (ALS) to maintain intracellular homeostasis. The accumulation of damaged proteins due to the decline in proteostasis control mechanisms is linked to the onset of neurodegenerative diseases. In contrast, in cancer cells, UPS and ALS are excessively stimulated compared to normal cells. Therefore, the disruption of proteostasis control mechanisms in cancer cells is expected to effectively induce cancer cell death through the active accumulation of unwanted materials.

Previously, it has been shown that ALS and UPS inhibitors enhance the effects of anticancer drugs and overcome resistance to them. However, two questions have arisen: First, when ALS and UPS are inhibited, different unwanted materials are expected to accumulate in different locations, but do they have the same effect on cells? Second, is the cytotoxicity (anticancer activity) and toxicity mechanism of an Atg4B inhibitor, which inhibits autophagosome membrane formation and scatters unwanted materials in the cell, and a lysosome inhibitor, which prevents the degradation of unwanted materials and keeps them enclosed in autophagosome membranes, the same?

By addressing these questions, we seek not only to understand the fate of unwanted products in the cell but also to control them. Such an understanding will not only contribute to the clinical application of these inhibitors, but will also greatly enhance our knowledge of their side effects. Such studies are critical to these inhibitors' safe and effective use in cancer therapy.

(E) 各種プロテオスタシス制御化合物の創製と “ごみ”の種類や分布、毒性の理解

Development of various proteostasis-regulating compounds and understanding of the types, distribution, and toxicity of “unwanted substances

【Representative Papers】

1. Kudo, Y., Hirota, K., Tsuzuki, H., Kawano, S., Saka, T., Hayashi, R., Yoshino, Y., Ikari, A. and Endo, S.*, Inhibition of autophagy by Atg7 knockdown enhances chemosensitivity in gemcitabine/paclitaxel-resistant pancreatic cancer. J. Biochem., (2025)

2. Himura, R.#, Kawano, S.# (#Equal first author contribution), Nagata, Y., Kawai, M., Ota, A., Kudo, Y., Yoshino, Y., Fujimoto, N., Miyamoto, H., Endo, S.*, Ikari, A., Inhibition of aldo-keto reductase 1C3 overcomes gemcitabine/cisplatin resistance in bladder cancer cells. Chem. Biol. Interact., 388, 110840 (2024)

3. Endo, S.*, Kawai, M., Hoshi, M., Segawa, J., Fujita, M., Matsukawa, T., Fujimoto, N., Matsunaga, T. and Ikari, A., Targeting Nrf2-antioxidant signaling reverses acquired cabazitaxel resistance in prostate cancer cells. J. Biochem., 170, 89-96 (2021)

4. Endo, S.*, Oguri, H., Segawa, J., Kawai, M., Hu, D., Xia, S., Okada, T., Irie, K., Fujii, S., Gouda, H., Iguchi, K., Matsukawa, T., Fujimoto, N., Nakayama, T., Toyooka, N., Matsunaga, T. and Ikari, A., Development of novel AKR1C3 inhibitors as new potential treatment for castration-resistant prostate cancer. J. Med. Chem., 63, 10396-10411 (2020)

現在は、これらに加えて以下のような研究課題にも取り組んでいます。

• プロテアソームを標的とした難治性固形がんの新規補助療法の開発

• アミロイド線維の戦略的蓄積による画期的がん治療戦略の確立

• がん細胞における液-液相分離を介した積極的翻訳抑制による細胞老化抑制戦略の解明

•  過酸化脂質由来細胞死の積極的誘導による新規がん克服戦略の確立

• ホルモン依存性がんの治療効果に喫煙習慣が与える影響の解析

• 女性におけるアンドロゲンシグナル制御の再考とその制御による新規トリプルネガティブ乳がんの予防・治療戦略の確立

• 肝細胞老化抑制戦略の確立

In addition to these, we are currently working on the following research projects...

• Development of novel adjuvant therapies for refractory solid tumors targeting the proteasome

• Strategic accumulation of amyloid fibrils as an innovative cancer therapy strategy

• Elucidation of strategies to inhibit cellular senescence by active translational repression through liquid-liquid phase separation in cancer cells.

• Establishment of a novel strategy to overcome cancer by active induction of lipid peroxide-derived cell death

• Analysis of the effect of smoking habit on the therapeutic efficacy of hormone-dependent cancers.

• Rethinking the regulation of androgen signaling in women and establishment of novel strategies for prevention and treatment of triple-negative breast cancer by the regulation of androgen signaling.

• Establishment of strategies to inhibit hepatocyte senescence