Treatment of Melanoma with 5-Fluorouracil or Dacarbazine In Vitro Sensitizes Cells to Antigen-Specific CTL Lysis through Perforin/Granzyme- and Fas-Mediated Pathways

• Published in: The Journal of immunology (1950) 2004-04, Vol.172 (7), p.4599-4608
• Main Authors: Yang, Sixun, Haluska, Frank G
• Format: Article
• Language: English
• Subjects: Antigens, Neoplasm; Antineoplastic Agents - pharmacology; Cell Line, Tumor; Cytotoxicity, Immunologic - drug effects; Dacarbazine - pharmacology; Epitopes, T-Lymphocyte - immunology; Fas Ligand Protein; fas Receptor - immunology; fas Receptor - physiology; Fluorouracil - pharmacology; Humans; Immune Sera - pharmacology; Ligands; Melanoma - drug therapy; Melanoma - enzymology; Melanoma - immunology; Melanoma-Specific Antigens; Membrane Glycoproteins - biosynthesis; Membrane Glycoproteins - physiology; Neoplasm Proteins - immunology; Peptide Fragments - immunology; Peptide Fragments - metabolism; Perforin; Pore Forming Cytotoxic Proteins; Protein Binding - immunology; Serine Endopeptidases - physiology; Signal Transduction - immunology; T-Lymphocytes, Cytotoxic - enzymology; T-Lymphocytes, Cytotoxic - immunology
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.172.7.4599

Several factors may influence sensitivity of melanoma cells to CTL lysis. One is the avidity of the CTL TCR. A second is that certain cytotoxic drugs have been reported to sensitize cancer cells to CTL lysis through Fas-mediated apoptosis. In this study, we examined whether antineoplastic agents 5-fluorouracil (5-FU) and dacarbazine (DTIC) sensitize melanoma cells to lysis of G209 peptide-specific CTL. Our results show that CTL generated from PBMC are HLA-A2 restricted and gp100 specific. Treatment with 5-FU or DTIC sensitized melanoma cells to lysis of G209-specific CTL. Most importantly, 5-FU- or DTIC-treated melanoma cells also became sensitive to low-avidity CTL, which per se are less cytolytic to melanomas. We sought to identify apoptotic pathways mediating this effect. The enhanced cytolysis was mediated through the perforin/granzyme pathway. Although 5-FU up-regulated FasR expression on melanoma cells, sensitization was not blocked by anti-Fas Ab, and the G209-specific CTL was Fas ligand (FasL) negative. However, when G209-specific CTL were stimulated to express FasL, FasL signaling also contributed to enhanced cytolysis. DTIC treatment, which did not increase FasR expression, also sensitized FasL-mediated killing induced by neutralizing anti-Fas Ab. For CD95L-positive G209-specific CTL, the sensitization was primarily mediated through the perforin/granzyme pathway regardless of up-regulation of FasR. The findings demonstrate that cytotoxic drug-mediated sensitization primes both perforin/granzyme and Fas-mediated killing by melanoma-specific CTL. Considering that most of autoreactive antitumor CTL are low avidity, the findings provide experimental basis for understanding cytotoxic and immunologic therapeutic synergy in melanoma.