Kondo Takuhito, Shibamoto Yuta, Kawai Tatsuya, Sugie Chikao, Wang Zhen, Nakamura Koichi, Murai Taro, Manabe Yoshihiko, Nakashima Masahiro, Matsuo Masayuki
Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Aichi, Japan.
Drug Metabolism & Pharmacokinetics Research Laboratories, Daiichi-Sankyo Co., Ltd., Tokyo, Japan.
Transl Cancer Res. 2021 Jun;10(6):2767-2776. doi: 10.21037/tcr-21-71.
Heat shock protein 90 (HSP90) is a molecular chaperone that is responsible for the conformational maintenance of several client proteins that play important roles in DNA damage repair, apoptosis following radiation, and resistance to radiation therapy. DS-2248 (tricyclic pyrazolopyrimidine derivative) is a newly-developed, orally available inhibitor of HSP90 with low adverse effects. We investigated the combined effects of radiation and DS-2248 and .
SCCVII squamous cell carcinoma cells and tumors transplanted in C3H/HeN mice were used. In vitro combined effects of X-ray radiation and DS-2248 were investigated using a colony assay. Phosphorylated histone H2AX (γH2AX) was quantified after 2-Gy irradiation with or without 24-hour pretreatment with DS-2248. The mice bearing SCCVII tumors received oral DS-2248 10 times over 2 weeks and received local irradiation with doses of 1, 2, 3, and 4 Gy delivered 6 times over 2 weeks. Then, tumor volumes were measured.
Radiation plus pretreatment with 50 nM DS-2248 for 24 hours produced synergistic effects on SCCVII cells. γH2AX foci persisted after radiation for longer periods (6 and 24 hours) in DS-2248-treated cells than in control cells. In vivo, the combined effects appeared to be additive when 5 or 10 mg/kg DS-2248 was combined with total radiation doses of 6-18 Gy, but the effect was considered supra-additive when 15 mg/kg of DS-2248 was combined with a total dose of 24 Gy.
The combined effects of DS-2248 and radiation were additive at low drug and radiation doses, but may have been supra-additive at higher doses. Inhibition of slow repair of DNA double strand breaks (i.e., homologous recombination) was considered to contribute to this combined effect.
热休克蛋白90（HSP90）是一种分子伴侣，负责多种客户蛋白的构象维持，这些客户蛋白在DNA损伤修复、辐射后凋亡以及对放射治疗的抗性中发挥重要作用。DS - 2248（三环吡唑并嘧啶衍生物）是一种新开发的、口服可用的HSP90抑制剂，不良反应低。我们研究了辐射与DS - 2248的联合作用。
使用SCCVII鳞状细胞癌细胞和移植于C3H/HeN小鼠的肿瘤。采用集落形成试验研究X射线辐射与DS - 2248的体外联合作用。在用或不用DS - 2248预处理24小时后进行2 Gy照射，然后对磷酸化组蛋白H2AX（γH2AX）进行定量分析。携带SCCVII肿瘤的小鼠在2周内口服DS - 2248 10次，并在2周内分6次接受1、2、3和4 Gy的局部照射。然后测量肿瘤体积。
辐射加50 nM DS - 2248预处理24小时对SCCVII细胞产生协同作用。与对照细胞相比，DS - 2248处理的细胞在辐射后（照射6小时和24小时）γH2AX焦点持续时间更长。在体内，当5或10 mg/kg DS - 2248与6 - 18 Gy的总辐射剂量联合使用时，联合作用似乎是相加的，但当15 mg/kg DS - 2248与24 Gy的总剂量联合使用时，该作用被认为是超相加的。
在低药物和辐射剂量下，DS - 2248与辐射的联合作用是相加的，但在较高剂量下可能是超相加的。DNA双链断裂的缓慢修复（即同源重组）的抑制被认为有助于这种联合作用。
