Min Thura1,†, Abdul Qader Omer Al-Aidaroos1,†, Wei Peng Yong2,3, Koji Kono3,4, Abhishek Gupta1, You Bin Lin1 Kousaku Mimura3, Jean Paul Thiery1,3, Boon Cher Goh2,3, Patrick Tan5, Ross Soo2,3, Cheng William Hong6, Lingzhi Wang3, Suling Joyce Lin5, Elya Chen4, Sun Young Rha7, Hyun Cheol Chung7, Jie Li1, Sayantani Nandi1, Hiu Fung Yuen1, Shu-Dong Zhang8, Yeoh Khay Guan9, Jimmy So9.10, and Qi Zeng1,*
1 Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore
2 Department of Haematology-Oncology, National University Cancer Institute, Singapore
3 Cancer Science Institute of Singapore, National University of Singapore, Singapore
4 Division of General Surgery (Upper Gastrointestinal Surgery), National University Hospital, Singapore
5 Genome Institute of Singapore (GIS), A*STAR, Singapore
6 Cleveland Clinic Lerner College of Medicine, Cleveland, OH, USA
7 Department of Internal Medicine, Yonsei Cancer Research Institute, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea
8 Northern Ireland Centre for Stratified Medicine, Ulster University, C-TRIC, Londonderry, United Kingdom
9 Yong Loo Lin School of Medicine, National University of Singapore, Singapore
10 Division of Surgical Oncology (Upper Gastrointestinal Surgery), National University Cancer Institute, Singapore
† These authors contributed equally to this work.
* Corresponding author.
Published in JCI Insight on 16 June 2016.
Novel, tumor-specific drugs are urgently needed for a breakthrough in cancer therapy. Herein, we generated a first-in-class humanized antibody (PRL3-zumab) against PRL-3, an intracellular tumor-associated phosphatase upregulated in multiple human cancers, for unconventional cancer immunotherapies. We focused on gastric cancer (GC), wherein elevated PRL-3 mRNA levels significantly correlated with shortened overall survival of GC patients. PRL-3 protein was overexpressed in 85% of fresh-frozen clinical gastric tumor samples examined, but not in patient-matched normal gastric tissues. Using human GC cell lines, we demonstrated that PRL3-zumab specifically blocked PRL-3-positive, but not PRL-3-negative orthotopic gastric tumors. In this setting, PRL-3-zumab had better therapeutic efficacy as a monotherapy rather than in combination with 5-fluorouracil, or 5-fluorouracil alone. PRL3-zumab could also prevent PRL-3-positive tumor recurrence. Mechanistically, we found that intracellular PRL-3 antigens could be externalized to become ‘extracellular oncotargets’, serving as bait for PRL3-zumab binding to potentially bridge and recruit immunocytes into tumor microenvironments for killing effects on cancer cells. In summary, our results document a comprehensive, novel cancer therapeutic approach to specific antibody-targeted therapy against PRL-3 oncotarget as a case study for developing antibodies against other intracellular targets in drug discovery.
Figure Legend : PRL3-zumab blocks PRL-3-positive (but not PRL-3-negative) orthotopic gastric tumors.
(A) Western blot for endogenous PRL-3 in 22 human gastric cancer (GC) cell lines. Tumorigenic PRL-3-positive (PRL-3+) or PRL-3-negative (PRL-3–) cell lines selected for subsequent animal models are indicated with a red asterisk (*). Mr, relative molecular mass (kDa).
(B) Outline of the experimental orthotopic GC model in BALB/c nude mice.
(C) PRL3-zumab inhibits PRL-3+ SNU-484 orthotopic gastric tumor growth. Upper panels, mice appearance at the end of the experiment (Day 28). Arrows highlight abdominal distention in untreated mice. Lower panels, excised stomachs with tumor areas framed in black lines. Bar, 10 mm.
(D) Mean gastric tumor volumes in untreated and treated groups at Day 28. n = 8 per group; p = 0.01, t-test; data representing mean ± SEM.
(E) Kaplan Meier survival analysis of untreated (red lines) and treated (black lines) groups of mice. n = 4 per group; p = 0.006, log-rank test.
(F) Summary of PRL3-zumab treatment outcomes in orthotopic models of 5 human GC cell lines. Data presented as mean tumor volume ± SEM at the end of the experiments. The Student’s t-test was used to determine statistical significance between treated and untreated groups.
For more information on Qi ZENG's lab, please click here.