Renal cell carcinoma tumors induce T cell apoptosis through receptor-dependent and receptor-independent pathways.
Tumors can promote their own progressive growth by inducing T cell apoptosis. Though previous studies suggested that tumor-mediated T cell killing is receptor dependent, we recently showed that tumor gangliosides also participate, a notion consistent with reports indicating that, in some cell types, gangliosides can activate the intrinsic apoptotic pathway by stimulating reactive oxygen species production, cytochrome c release, and caspase-9 activation. In this study, we used normal peripheral blood T cells, as well as caspase-8-, caspase-9-, and Fas-associated death domain protein-deficient Jurkat cells, to assess whether the death ligands and gangliosides overexpressed by the renal cell carcinoma (RCC) cell line SK-RC-45 can independently stimulate T cell apoptosis as a mechanism of immune escape. Anti-FasL Abs and the glycosylceramide synthase inhibitor 1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol (PPPP) each partially inhibited the ability of SK-RC-45 to kill cocultured activated T cells; together, as purified molecules, RCC gangliosides and rFasL induced a more extensive mitochondrial permeability transition and greater levels of apoptosis than either agent alone, equivalent to that induced by the FasL- and ganglioside-expressing RCC line itself. rFasL-mediated apoptosis was completely inhibited in caspase-8- and Fas-associated death domain protein-negative Jurkat cells, though apoptosis induced by purified gangliosides remained intact, findings that correlate with the observed partial inhibition of SK-RC-45-induced apoptosis in the Jurkat lines with defective death receptor signaling. Western blot analysis performed on lysates made from wild-type and mutant Jurkat cells cocultured with SK-RC-45 revealed caspase activation patterns and other biochemical correlates which additionally supported the concept that tumor-associated gangliosides and FasL independently activate the caspase cascade in T cells through the intrinsic and extrinsic pathways, respectively.
Das
Tanya
T
Department of Immunology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
Sa
Gaurisankar
G
Paszkiewicz-Kozik
Ewa
E
Hilston
Cynthia
C
Molto
Luis
L
Rayman
Patricia
P
Kudo
Daisuke
D
Biswas
Kaushik
K
Bukowski
Ronald M
RM
Finke
James H
JH
Tannenbaum
Charles S
CS
D017209:Apoptosis; D002292:Carcinoma, Renal Cell / Q000378:metabolism*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D004789:Enzyme Activation; D053222:Fas Ligand Protein / Q000378:metabolism; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D005732:Gangliosides / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D053218:Receptors, Death Domain / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology* / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism
C505533:FADD protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D005732:Gangliosides; D053218:Receptors, Death Domain; D019014:fas Receptor; D053181:Caspase 8; D053453:Caspase 9