Over-expression of the folate receptor (FR) has been shown on the vascular side of cancerous cells including those of the breast, ovaries, testes, and cervix. However, FR over-expression has not yet been explored fully in melanoma. We hypothesized that folate receptor is over-expressed on melanoma and that a novel folate-conjugated immunoglobulin G (F-IgG) would bind the FR to target melanoma cells for lysis by natural killer (NK) cells.
Folate receptor expression was confirmed in the Mel-39 (human melanoma) cell line by flow cytometry and immunoblot analysis, using KB (human oral epithelial) and F01 (human melanoma) as a positive and negative control, respectively. FR positive and negative cell lines were coated with F IgG or control immunoglobulin G (C-IgG) in the presence or absence of cytokines in order to determine NK cell ability to lyse FR-positive cell lines. NK cell activation was significantly upregulated and lysis of Mel 39 tumor cells enhanced following treatment with F IgG, as compared to C-IgG at all effector:target (E:T) ratios (p<0.01). This trend was further enhanced by the addition of interleukin-12 (IL-12). NK cell production of cytokines such as interferon-gamma (IFN-γ), macrophage inflammatory protein 1 alpha (MIP-1α), and regulated on activation normal T-cell expressed and secreted (RANTES) were also significantly increased in response to IL 12 stimulation and F IgG coated Mel 39 target cells, as compared to controls (p<0.01). In contrast, F-IgG did not bind to F01 (FR-negative cell line) and had no significant effect on NK cell lysis or cytokine production. This research indicates the potential use of F-IgG for its ability to induce an immune response from NK cells against FR-positive melanoma tumor cells which can be further enhanced by the addition of cytokines.Arts and Sciences Undergraduate Research Scholarship. The Ohio State University, Columbus, Ohio 43210Undergraduate Student Government Academic Enrichment Grant. The Ohio State University, Columbus, Ohio 43210Pelotonia Undergraduate Fellowship. The Ohio State University, Columbus, Ohio 43210A one-year embargo was granted for this item
