title: Treatment of melanoma with 5-fluorouracil or dacarbazine in vitro sensitizes cells to antigen-specific CTL lysis through perforin/granzyme- and Fas-mediated pathways.
abstract: 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.
authors.affiliation: Division of Hematology-Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Sixun
authors.initials: S
authors.lastname: Yang
authors.forename: Frank G
authors.initials: FG
authors.lastname: Haluska
mesh_terms: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D003606:Dacarbazine / Q000494:pharmacology*; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D053222:Fas Ligand Protein; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D008024:Ligands; D008545:Melanoma / Q000188:drug therapy* / Q000201:enzymology / Q000276:immunology; D058950:Melanoma-Specific Antigens; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000502:physiology*; D009363:Neoplasm Proteins / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011485:Protein Binding / Q000276:immunology; D012697:Serine Endopeptidases / Q000502:physiology*; D015398:Signal Transduction / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology / Q000276:immunology; D019014:fas Receptor / Q000276:immunology / Q000502:physiology*
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D018984:Epitopes, T-Lymphocyte; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D007106:Immune Sera; D008024:Ligands; D058950:Melanoma-Specific Antigens; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D052899:Pore Forming Cytotoxic Proteins; D019014:fas Receptor; D054353:Perforin; D003606:Dacarbazine; D012697:Serine Endopeptidases; D005472:Fluorouracil