γ-分泌酶抑制剂对人多发性骨髓瘤细胞系RPMI8226细胞小鼠移植瘤的抑制作用

Inhibitory effects of gamma secretase inhibitor on human multiple myeloma xenograft mouse model

目的探讨通过γ-分泌酶抑制剂MRK003抑制Notchl及蛋白激酶B（AKT）表达，观察其对人多发性骨髓瘤（MM）小鼠移植瘤生长的抑制作用。方法将MM细胞系RPMl8226细胞皮下注射给NOD／SCID小鼠，建立人MM小鼠移植瘤模型。将成瘤小鼠分为两组，实验组小鼠瘤体内每日注射丫一分泌酶抑制剂MRK0035mg·kg-1·d-1（0．2m1），连续注射14d；对照组小鼠瘤体内注射等量的生理盐水，观察肿瘤生长情况。于末次注射第2天颈椎脱臼法处死小鼠后取瘤组织制作石蜡切片，应用免疫组织化学和Westernblot方法检测Notchl、AKT表达。结果RPMl8226细胞小鼠皮下注射后5～7d成瘤，10-12d肿瘤生长明显。注射MRK003前两组小鼠肿瘤平均体积分别为509．2和511．2mm3（P〉0．05）；连续给药第9天测量实验组、对照组肿瘤平均体积分别为636．6和691．2mm3（p，0．01）；末次给药后的第2天实验组肿瘤体积为683．5mm3，明显小于对照组的1798．7mm3（P〈0．01）；免疫组织化学染色显示实验组小鼠肿瘤组织Notchl及AKT阳性率为11．1％和13．3％，明显低于对照组的95．6％和93．3％（P值均〈0．01）；Westernblot结果显示实验组小鼠肿瘤组织Notchl及AKT蛋白的表达明显低于对照组。结论γ-分泌酶抑制剂MRK003可抑制人MM小鼠移植瘤的生长，其作用可能是通下调Notcbl信号通路蛋白的表达实现的。

Objective To explore the tumor growth inhibition of gamma secretase inhibitor MRK003 on human multiple myeloma xenograft mice by inhibition of AKT and Notchl expression. Methods NOD/SCID mice were injected with human multiple myeloma cell lines RPMI8226 to establish a xenograft mouse model. Mice were randomized into two groups： the experimental group were injected with MRK003 at a dose of 5 mg- kg-1. d -1 for 14 days; the inhibitor was replaced by an equal saline in the control group. Mice were sacrificed by cervical dislocation on the next day after the last injection and tumor tissue was removed to detect the expression of Notch 1 and AKT by immunohistochemistry. Results After subcutaneous injection with RPMI8226, mice had tumor formation in 5-7 days and the largest tumor block in 10- 12 days. Before RPMI8226 injection, the mean sizes of tumor block in the experimental and the control groups were 509.2 mm3, 511.2 mm3 （P〉0.05）. 9 days after injection, the mean sizes of tumor tissue in the experimental and the control groups were 636.6 mm3, 691.2 mm3 （P〈0.01） . On the next day after the last injection, the tumor sizes of the experimental and the control groups were 683.5 mm3 and 1798.7 mm3 （P〈0.01 ）. The size of tumor block in the experimental group was significantly smaller than that of the control group （P〈0.01）. Immunohistochemistrical staining showed that the positive expression rates of Notchl （11.1%, P〈0.01） and AKT （13.3%, P〈0.01） in experimental group were significantly decreased compared with the control group （Notchl： 95.6%; AKT： 93.3%）. Western blot results showed that Notchl and AKT protein in experimental group were significantly lower than those in the control group. Conclusion MRK003 could inhibit the tumor growth of human multiple myeloma xenograft mice by down-regulated expression of Notch 1 signaling pathway.