Abstract 5617: A core fucose-deficient anti-podocalyxin antibody exhibits antitumor activity via augmented antibody-dependent cellular cytotoxicity in oral squamous cell carcinoma
Authors: Itai Shunsuke , Kaneko Mika K. , Yamada Shinji , Kato Yukinari 
Published: August 2018

Background: Podocalyxin is a mucin-like type I transmembrane protein that is highly glycosylated with O- and N-glycans. It was originally found in renal podocytes and is also expressed in many kinds of cancers such as colorectal, breast and oral cancers. In addition, it was reported that podocalyxin overexpression is associated with progression, metastasis and poor outcomes; consequently, it is known as a diagnostic marker. However, the function of podocalyxin in oral cancers, including oral squamous cell carcinomas (OSCCs), has not been fully elucidated because there are few monoclonal antibodies (mAbs) suitable for analyzing podocalyxin expression in OSCCs. We recently produced sensitive and specific anti-podocalyxin mAb PcMab-47, which reacts with endogenous podocalyxin-expressing cancer cell lines. Furthermore, we have produced a mouse-human chimeric PcMab-47 (chPcMab-47) and demonstrated its antitumor activity against podocalyxin-expressing xenograft models using HCT-15 colon cancer cells and Chinese hamster ovary (CHO)/podocalyxin cells.Methods: We first engineered PcMab-47 into a mouse IgG2a-type mAb (47-mG2a) to add antibody-dependent cellular cytotoxicity (ADCC) activity and further developed a core fucose-deficient 47-mG2a (47-mG2a-f) to augment its ADCC activity using a fucosyltransferase 8-knockout CHO-S cell line. The binding affinity was determined using flow cytometric analysis. Using PcMab-47, 47-mG2a, and 47-mG2a-f, immunohistochemical analysis was performed against 201 cases of oral cancer tissues, and the sensitivity was compared. ADCC and complement-dependent cytotoxicity (CDC) activities were investigated using the 51Cr release assay. Finally, antitumor activity in OSCC xenograft models was compared using 100 or 500 μg /mouse, three times injection of 47-mG2a and 47-mG2a-f. Results: Both 47-mG2a and 47-mG2a-f exhibited higher binding affinity than PcMab-47 for podocalyxin-expressing OSCC cells such as SAS and HSC-2 cells. In immunohistochemical analysis of OSCCs using PcMab-47 and 47-mG2a, it was revealed that 47-mG2a showed high-sensitivity for staining OSCC cells in a cytoplasmic pattern at a much lower concentration. PcMab-47 detected podocalyxin in 163 cases (81.1%); in contrast, 47-mG2a did in 197 cases (98.0%). 47-mG2a-f exhibited the similar sensitivity as 47-mG2a, indicating that 47-mG2a and 47-mG2a-f are useful for immunohistochemical analyses of podocalyxin expression in OSCCs. In vitro analysis revealed that 47-mG2a-f exhibited much stronger ADCC than 47-mG2a, whereas these mAbs did not display CDC. Furthermore, 47-mG2a-f exerted antitumor activity in SAS and HSC-2 xenograft models, whereas 47-mG2a did not. Conclusions: A core fucose-deficient anti-podocalyxin mAb could be useful for antibody-based therapy against podocalyxin-expressing OSCCs.

Citation Format: Shunsuke Itai, Mika K. Kaneko, Shinji Yamada, Yukinari Kato. A core fucose-deficient anti-podocalyxin antibody exhibits antitumor activity via augmented antibody-dependent cellular cytotoxicity in oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5617.