c-myc和K-ras对小鼠卵巢上皮细胞体外转化和体内致瘤的研究

The mouse ovarian surface epithelium cells ( MOSE ) transformation induced by c-myc /K-ras in vitro and in vivo

目的探讨癌基因c-myc和K-ras在卵巢癌发生发展中的作用。方法用逆转录病毒转基因系统,将正常的c-myc基因和突变的K-ras基因先后导入小鼠卵巢上皮(MOSE)细胞,建立表达c-myc和K-ras基因的细胞株,分别称为MOSE-Myc细胞、MOSE-Ras细胞和MOSE-RM细胞。通过细胞增殖实验、克隆形成实验、体外侵袭实验以及体内成瘤实验,研究转基因后MOSE细胞生物学特性的改变及恶性转化。结果c-myc和K-ras基因容易被重组逆转录病毒导入MOSE细胞,转导后靶细胞内分别有相应的c-myc或K-ras mRNA转录,以及相应的c-myc(62 000)和K-ras(21 000)蛋白的表达。MOSE-Ras组和MOSE-RM(MOSE-Ras／Myc)组细胞增殖能力显著强于MOSE和MOSE-Myc组(P<0．01),MOSE-RM组细胞增殖能力显著强于MOSE-Myc组(P<0．05)。MOSE-Ras和MOSE-RM组在软琼脂培养中均能形成克隆集落,而MOSE组和MOSE-Myc组不能形成克隆集落。MOSE-Ras组和MOSE-RM组能够穿透Matrigel,具有侵袭能力。MOSE-Ras组和MOSE-RM组细胞在裸鼠体内形成肿瘤,且肿瘤组织细胞仍然可见有K-ras和c-myc蛋白的表达;而MOSE组和MOSE-Myc组无肿瘤形成。结论重组逆转录病毒载体作为转基因的工具,转导效率高,可稳定表达,可以感染正常的细胞;突变的K-ras可使MOSE发生恶性转化,在体内形成肿瘤;c-myc作为一个核转录调节因子,不能使MOSE发生恶性转化,但可协同其他因子,加强其他因子的功能。

Objective To study the function of c-myc and K-ras in tumorigenesis of ovarian cancer. Methods K-ras and/or c-myc cDNAs were introduced into mouse ovarian surface epithelium cells （MOSE） using recombinant Moloney retroviral vectors. The resulting MOSE cells were studied by cell proliferation assays, the ability to form colonies in soft agarose, matrigel invasion assays and tumorigenicity assays in nude mice. Results K-ras and c-myc can be easily delivered to the normal MOSE cells by recombinant retroviruses, mRNA and protein of the target genes can be detected by RT-PCR and Western blot. Cell proliferation assays showed that MOSE-Ras cells and MOSE-RM cells （MOSE-Ras/Myc） grew more rapidly than parental cells （MOSE） and MOSE-Myc cells （ P 〈 0.01 ）. In addtition, MOSE-RM cells grew more rapidly than MOSE-Ras cells （ P 〈 0.05 ）. Cell colony formation assays showed that while MOSE-Ras and MOSE-RM cells can form colonies in soft-agarose, the MOSE-Myc and MOSE cells did not. Matrigel invasion assays showed that MOSE-Ras and MOSE-RM cells have invasion ability, but not MOSE-Myc ascites and the control MOSE cells. Xenograft experiments showed that MOSE-Ras and MOSE-RM cells were able to form tumors in nude mice following intraperitoneal injection. Tumors were not observed in animals injected with either MOSE-Myc or MOSE cells. Conclusion The recombinant Moloney retroviral system is a highly efficient and convenient method for introducing and expressing foreign genes in murine surface epithelial cell cultures. In this model, expression of K-ras alone is sufficient to generate tumorigenic MOSE, however expression of c-myc in conjunction with K-ras results in cells with a higher index of malignancy. Based on the assays described in this report, expression of c-myc alone can not transform MOSE cultures although it does play a role in cooperation with K-ras.