Establishment of molecular targeting therapy against ovarian cancer using human monoclonal antibody

目的：近年来，利用单克隆抗体的抗体治疗已成为治疗癌症的新途径。方法：以人卵巢透明细胞腺癌细胞系（RMG-I）为抗原，免疫KM小鼠，用ELISA筛选法获得杂交瘤细胞上清。用MA 602 -1和MA 602 -6两种抗体筛选杂交瘤细胞，用CA 125样抗原夹心免疫分析法，有限稀释法制备人源单克隆抗体，用免疫组化法检测该抗体（HMOCC-2）与卵巢癌的反应性，用Western blotting法检测其特异性。使用各种抗体来鉴定HMOCC-2靶向的表位。结果：HMOCC-2在60%（63/105）的卵巢癌组织中呈阳性反应。RMG-1的膜组分的Western印迹显示在120 kDa至250 kDa处的几个条带。HMOCC-2识别由几种抗体鉴定的CA 125样抗原。结论：HMOCC-2通过与CA 125相似的靶抗原表位特异性地与卵巢癌细胞结合，对卵巢癌细胞也具有抗肿瘤活性。这些结果表明，它可能有潜力被用于临床的分子靶向治疗。

Objective : In recent years, antibody therapy employing monoclonal antibodies has become a new approach for treating cancer. This study was performed to establish a human monoclonal antibody recognizing an epitope related to CA125 using KM mice and to assess its reactivity with ovarian cancer cells.Methods : A human ovarian clear cell adenocarcinoma cell line (RMG-I) was used to immunize KM mice, and hybridoma supernatant was obtained by a standard method employing ELISA screening. Next, selection of hybridomas was performed with two antibodies (MA602-1 and MA602-6) and a sandwich immunoassay for CA125-like antigen, and then the limiting dilution was used to obtain a human monoclonal antibody.Immunohistochemical reactivity of this antibody (HMOCC-2) with ovarian cancer was assessed, while its specificity was analyzed by Western blotting. Various antibodies were used to identify the epitope targeted by HMOCC-2. Finally, the antitumor effect of HMOCC-2 was assessed by intraperitoneal administration to SCID mice with heterografts of RMG-I tumors.Results : HMOCC-2 showed a positive reaction with 60% (63/105) of ovarian cancer specimens. Western blotting of the membrane fraction of RMG-I revealed several bands at 120 kDa to 250 kDa. HMOCC-2 recognized the CA125-like antigens identified by several antibodies. HMOCC-2 also exhibited significant antitumor activity (p<0.01) against ovarian cancer heterografts.Conclusion : HMOCC-2 reacts specifically with ovarian cancer cells via a target epitope analogous to that of CA125, and also exhibits activity against ovarian tumors. These findings suggest that it may have the potential to be employed clinically for molecular-targeting therapy.