Fibroblast growth factor-inducible protein 14 (Fn14), the cell surface receptor for tumor necrosis factor-like weak inducer of apoptosis (TWEAK), is overexpressed in various human solid tumor types and can be a negative prognostic indicator. We detected Fn14 expression in ∼60% of the melanoma cell lines we tested, including both B-Raf WT and B-Raf V600E lines. Tumor tissue microarray analysis indicated that Fn14 expression was low in normal skin, but elevated in 173/190 (92%) of primary melanoma specimens and in 86/150 (58%) of melanoma metastases tested. We generated both a chemical conjugate composed of the recombinant gelonin (rGel) toxin and the anti-Fn14 antibody ITEM-4 (designated ITEM4-rGel) and a humanized, dimeric single-chain antibody of ITEM-4 fused to rGel (designated hSGZ). Both ITEM4-rGel and hSGZ were highly cytotoxic to a panel of different melanoma cell lines. Mechanistic studies showed that both immunotoxins induced melanoma cell necrosis. In addition, these immunotoxins could upregulate the cellular expression of Fn14 and trigger cell-signaling events similar to the Fn14 ligand TWEAK. Finally, treatment of mice bearing human melanoma MDA-MB-435 xenografts with either ITEM4-rGel or hSGZ showed significant tumor growth inhibition compared with controls. We conclude that Fn14 is a therapeutic target in melanoma and the hSGZ construct appears to warrant further development as a therapeutic agent against Fn14-positive melanoma.
Bibliographical noteFunding Information:
We thank Dr Lyn Duncan (Massachusetts General Hospital, Boston, MA) for providing the melanoma progression TMA. This work was conducted, in part, by the Clayton Foundation for Research (MGR), National Institutes of Health (NIH) grants R01 NS055126 (JAW), R01 CA130940 (NLT), and T32 HL007698 (EC), and Department of Defense Breast Cancer Concept Award BC086135 (JAW). MBW’s work was conducted in Dr Andrew E. Aplin’s lab under the funding of NIH grant CA125103. STR DNA fingerprinting of our melanoma cell lines was supported by MDACC Institutional Core Grant NIH CA16672.