Significant antitumor effect of an antibody against TMEM180, a new colorectal cancer‐specific molecule

Abstract

The present state of therapy for colorectal cancer (CRC) is far from satisfactory, highlighting the need for new targets for this disease. We identified a new CRC‐specific molecule, TMEM180, a predicted 11‐pass transmembrane protein that apparently functions as a cation symporter. We developed an anti‐TMEM180 mAb and then succeeded in humanizing the mAb. Immunohistochemistry (IHC) in CRC with the mAb showed a similar positivity rate as compared with anti‐epidermal growth factor receptor mAb, and IHC with anti‐TMEM180 mAb did not show staining in major organs used in this study. Immune electron microscopy clearly indicated that TMEM180 was present on the tumor exosome. The TMEM180 promoter region contains 10 hypoxia‐responsive element consensus sequences; accordingly, SW480 cells upregulated TMEM180 under low‐oxygen conditions. Anti‐TMEM180 mAb has in vitro antibody‐dependent cell‐mediated cytotoxicity and complement‐dependent cytotoxicity activity, and SW480 CRC xenografts were eradicated by the mAb. These data indicate that TMEM180 may be a new CRC marker and that a mAb against this protein could be used as antibody‐based therapy against CRC.

Topological analysis of TMEM180, a newly identified membrane protein that is highly expressed in colorectal cancer cells

“…Previously, we reported that TMEM180 is upregulated under low-oxygen conditions, and that TMEM180 may play an important role in the uptake or metabolism of glutamine and arginine in cancer cell proliferation [2]. We also showed that expression of TMEM180 is not essential for mouse development, as Tmem180-knockout mice do not exhibit embryonic, neonatal, or postnatal lethality [2].…”

“…Previously, we reported that TMEM180 is upregulated under low-oxygen conditions, and that TMEM180 may play an important role in the uptake or metabolism of glutamine and arginine in cancer cell proliferation [2]. We also showed that expression of TMEM180 is not essential for mouse development, as Tmem180-knockout mice do not exhibit embryonic, neonatal, or postnatal lethality [2]. During the preparation of this manuscript, a group from Huazhong University of Science and Technology reported that SNP rs2001389 is significantly associated with pancreatic cancer risk, weakens the binding activity of the transcriptional repressor CCCTC-binding factor (CTCF), and is associated with the lower expression of MFSD13A/TMEM180.…”

“…Previously, in our laboratory, we subjected 100% pure normal colonocytes obtained from lavage solution after colonoscopy to comprehensive expression analysis along with colorectal cancer cell lines [26]. Following this analysis, we performed RT-PCR and in-situ hybridization; as a result, we identified TMEM180, a CRC-specific multi-pass membrane protein of unknown function [2]. In this study, we analyzed protein structure, including topology, to elucidate the molecular function of TMEM180.…”

“…4A). We chose to use the HA-Tag to confirm expression rather than the anti-TMEM180 mAb that we developed previously [2] because the location of the epitope for this mAb remains unknown. HEK293T cells transfected with a TMEM180 gene with FLAG inserted into five predicted loops (79FLAG, 153FLAG, 236FLAG, 329FLAG, and 398FLAG) were stained by both anti-HA pAb and anti-FLAG mAb regardless of permeabilization ( Fig.…”

“…Consequently, there is a considerable incentive to identify new target molecules for diagnosis of and drug development for this disease. We previously identified a new CRC-specific protein, TMEM180, and developed the anti-TMEM180 monoclonal antibody (mAb) for use in diagnosing and treating CRC [2].…”