Abstract
Membrane protein claudin3 has been recently suggested as a marker for biologically aggressive tumors and a possible target for the therapeutic delivery of active anti-cancer compounds. Claudin3-binding molecules such as the Clostridium perfringens enterotoxin (CPE), CPE-related molecules, and murine and chimeric antibodies have shown promising antitumor efficacy in preclinical oncological settings. We first engineered a fully human anti-claudin3 IgG1 antibody (IgGH6) by fusing the human IgG1 Fc-domain to the anti-claudin3 scFvH6 previously isolated from a pre-immune phage display library. The construct was expressed in mammalian cells and specifically targeted claudin3 endogenously expressed on the surface of different human ovarian cancer cell lines. No detectable cross-reactivity with other homologous claudins was observed. The epitope recognized by IgGH6 is located within the minor extracellular domain of claudin3 and becomes accessible only in tumor cells characterized by incomplete junction formation. Confocal microscopy experiments demonstrated that IgGH6 was actively internalized in tumor cells after binding to native claudin3 and co-localized, likely within intracellular vesicles, with the C-CPE peptide. Preliminary results indicate that IgGH6 accumulated in vivo in free claudin3 ovarian carcinoma xenografts. For its selective uptake in tumor cells and its human nature, IgGH6 represents a valuable candidate for antibody-drug conjugate therapeutic applications in ovarian cancer patients.
Highlights
Claudins form a family of 24 transmembrane proteins that are major constituents of tight junction (TJ) complexes located at the apical end of the lateral surface of polarized epithelia
Since claudin3 is expressed at high density at the surface of ovarian tumor cells, we preferred measuring avidity rather than affinity to mimic the in situ actual conditions
The possibility of targeting neoplastic cells while sparing healthy tissues would significantly improve the tollerability of anti-cancer therapies and, there is an enormous interest in identifying biomarkers and reagents suitable for selective drug delivery
Summary
Claudins form a family of 24 transmembrane proteins that are major constituents of tight junction (TJ) complexes located at the apical end of the lateral surface of polarized epithelia. The up-regulation of claudin and 4 correlates with the progression of endometrial carcinoma [3], while the reduced expression of claudin with poor survival in stage II of colon cancer [4]. Claudin overexpression inversely correlated with the metastatic potential of pancreatic www.impactjournals.com/oncotarget cancer cells but positively with the invasiveness of ovarian carcinoma cells [5,6]. Claudin basal expression is low in normal epithelial cells, but the protein accumulates at the cell surface of several biologically aggressive human cancers, including breast, prostate, pancreatic, and epithelial ovarian tumors [8, 9]. The loss of cellular polarity and cell-cell interaction which occurs in cells during neoplastic transformation leads to the exposure of TJ components on the cell surface, making claudin accessible to extracellular antibody binding (“free” claudin3) [10]. Due to its differential overexpression and accessibility in a variety of human tumors, claudin might represent both a diagnostic biomarker and a potential therapeutic target for drug delivery
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call