Abstract C171: Human anti-Nucleolin recombinant immunoagents as new potential tools for melanoma treatment

Immunotherapy and immune-based anti-cancer molecules represent a valid strategy to fight cancer. However, the choice of tumor-specific surface molecules for the selective targeting of cancer cells still represents a critical step in the study design for the development of new therapeutic approaches. Notably, the development of phage-display technology for the selection of fully human single chain antibody fragments (scFvs) and complete antibodies directed toward tumor-associated antigens has represented a significant advancement for immunotherapy. Nucleolin (NCL) is one of the most abundant non-ribosomal proteins in the nucleolus. NCL is frequently up-regulated in cancer and in cancer-associated endothelial cells compared to normal tissues, where it is also present on the cell surface. Altered NCL expression and localization results in oncogenic effects such as stabilization of oncogenic mRNAs and microRNAs (miRNAs). Particularly, we demonstrated that NCL enhances the maturation of specific miRNAs (including miR-21, miR-221 and miR-222) causally involved in cancer pathogenesis, aggressiveness, metastatic potential and resistance to several anti-neoplastic treatments. Because of its oncogenic role and specific expression on cancer cell surface, NCL represents an attractive target for anti-neoplastic therapies. To produce a new anti-NCL molecule with significant potential for clinical applications, we took advantage of phage-display technology to isolate a fully human single chain Fragment variable (scFv), named 4LB5, which binds with high affinity to the RNA binding domain (RBD) of NCL. In our previous study we demonstrated that 4LB5 binds NCL on the surface of aggressive breast cancer cells and inhibits their proliferation both in vitro and in vivo, representing the prototype of a new class of immune-based anti-NCL compounds. Since NCL expression has been previously reported on the cell surface of skin cancer cell lines and up-regulation of NCL-dependent microRNAs was described in human melanomas, the objective of this project was the assessment of 4LB5 as a potential tool for melanoma therapy. To this aim, the recombinant scFv was expressed as His6-fusion protein in E.Coli and purified by affinity chromatography, as previously described. By using Enzyme-Linked Immunosorbent Assays (ELISA), we demonstrated a significant binding of 4LB5 to the cell surface of different melanoma cell lines of both human and mouse origins. Notably, inhibition of NCL expression by siRNA transfection reduced the binding of 4LB5 to the cell surface of these cell lines, further supporting its specificity against NCL. Then, we assessed the potential effects of 4LB5 treatment on cell proliferation. Colony formation assays demonstrated that 4LB5 significantly affected cell proliferation of both human and mouse melanoma cell lines. Our results, in agreement with previously reported data, further support the potential activity of 4LB5 as a tool for cancer therapy, paving the way for additional investigations aimed to fully elucidate the molecular mechanisms affected by this scFv and resulting in its anti-neoplastic therapy in human melanomas. Furthermore, this study supports the idea that anti-NCL immunoagents might represent a class of new anti-cancer compounds with a strong clinical relevance for a wide range of human tumors. Citation Format: Ashley Braddom, Timothy Richmond, Tyler Sheetz, Erika Reese, Anna Tessari, Kathleen Tober, Christin E. Burd, Claudia De Lorenzo, Edward W. Martin, Jr., Vincenzo Coppola, Michael F. Tweedle, Tatiana Oberyszyn, Carlo M. Croce, Dario Palmieri. Human anti-Nucleolin recombinant immunoagents as new potential tools for melanoma treatment. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C171.