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

目的：近年来，利用单克隆抗体进行抗体治疗已成为治疗肿瘤的新途径。本研究利用KM小鼠建立识别CA125相关表位的人单克隆抗体，并评估其与卵巢癌细胞的反应性。方法：采用人卵巢透明细胞腺癌细胞系（RMG-I）免疫KM小鼠，采用ELISA筛选标准方法获得杂交瘤上清。接下来，用两种抗体（MA602-1和MA602-6）筛选杂杂瘤，并对ca125样抗原进行夹心免疫测定，然后用极限稀释获得人单克隆抗体。评估该抗体（HMOCC-2）与卵巢癌的免疫组化反应性，并通过Western blotting分析其特异性。利用多种抗体鉴定HMOCC-2靶向的表位。最后，通过对异种rmg - 1肿瘤移植的SCID小鼠腹腔注射HMOCC-2来评估其抗肿瘤作用。结果：60%（63/105）的卵巢癌标本HMOCC-2阳性。RMG-I膜组分的Western blotting在120kda至250kda范围内显示出多条条带。HMOCC-2识别了几种抗体所识别的ca125样抗原。HMOCC-2对卵巢癌异种移植物也有显著的抗肿瘤活性（p<0.01）。结论：HMOCC-2通过类似于CA125的靶表位特异性作用于卵巢癌细胞，并表现出抗卵巢肿瘤的活性。这些发现表明，它可能具有应用于临床分子靶向治疗的潜力。

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.