Kobayashi Masanori, Onozawa Moe, Watanabe Shiho, Nagashima Tomokazu, Tamura Kyoichi, Kubo Yoshiaki, Ikeda Akiko, Ochiai Kazuhiko, Michishita Masaki, Bonkobara Makoto, Kobayashi Masato, Hori Tatsuya, Kawakami Eiichi
Laboratory of Reproduction, School of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan.
Laboratory of Veterinary Pathology, School of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan.
Vet Comp Oncol. 2023 Jun;21(2):221-230. doi: 10.1111/vco.12879. Epub 2023 Feb 20.
Canine prostate cancer (cPCa) is a malignant neoplasm with no effective therapy. The BRAF V595E mutation, corresponding to the human BRAF V600E mutation, is found frequently in cPCa. Activating BRAF mutations are recognized as oncogenic drivers, and blockade of MAPK/ERK phosphorylation may be an effective therapeutic target against BRAF-mutated tumours. The aim of this study was to establish a novel cPCa cell line and to clarify the antitumor effects of MEK inhibitors on cPCa in vitro and in vivo. We established the novel CHP-2 cPCa cell line that was derived from the prostatic tissue of a cPCa patient. Sequencing of the canine BRAF gene in two cPCa cell lines revealed the presence of the BRAF V595E mutation. MEK inhibitors (trametinib, cobimetinib and mirdametinib) strongly suppressed cell proliferation in vitro, and trametinib showed the highest efficacy against cPCa cells with minimal cytotoxicity to non-cancer COPK cells. Furthermore, we orally administered 0.3 or 1.0 mg/kg trametinib to CHP-2 xenografted mice and examined its antitumor effects in vivo. Trametinib reduced tumour volume, decreased phosphorylated ERK levels, and lowered Ki-67 expression in xenografts in a dose-dependent manner. Although no clear adverse events were observed with administration, trametinib-treated xenografts showed osteogenesis that was independent of dosage. Our results indicate that trametinib induces cell cycle arrest by inhibiting ERK activation, resulting in cPCa tumour regression in a dose-dependent manner. MEK inhibitors, in addition to BRAF inhibitors, may be a targeted agent option for cPCa with the BRAF V595E mutation.
犬前列腺癌（cPCa）是一种没有有效治疗方法的恶性肿瘤。与人类BRAF V600E突变相对应的BRAF V595E突变在cPCa中频繁出现。激活的BRAF突变被认为是致癌驱动因素，阻断MAPK/ERK磷酸化可能是针对BRAF突变肿瘤的有效治疗靶点。本研究的目的是建立一种新型的cPCa细胞系，并阐明MEK抑制剂在体外和体内对cPCa的抗肿瘤作用。我们建立了源自一名cPCa患者前列腺组织的新型CHP-2 cPCa细胞系。对两种cPCa细胞系中的犬BRAF基因进行测序，发现存在BRAF V595E突变。MEK抑制剂（曲美替尼、考比替尼和米哚妥林）在体外强烈抑制细胞增殖，曲美替尼对cPCa细胞显示出最高的疗效，对非癌性COPK细胞的细胞毒性最小。此外，我们给CHP-2异种移植小鼠口服0.3或1.0mg/kg曲美替尼，并在体内检测其抗肿瘤作用。曲美替尼以剂量依赖的方式减少肿瘤体积，降低磷酸化ERK水平，并降低异种移植物中Ki-67的表达。虽然给药后未观察到明显的不良事件，但曲美替尼治疗的异种移植物显示出与剂量无关的骨生成。我们的结果表明，曲美替尼通过抑制ERK激活诱导细胞周期停滞，从而以剂量依赖的方式导致cPCa肿瘤消退。除BRAF抑制剂外，MEK抑制剂可能是针对具有BRAF V595E突变的cPCa的一种靶向药物选择。
