Identification of small molecules that sensitize resistant tumor cells to tumor necrosis factor-family death receptors.
Two major pathways for apoptosis have been identified, involving either mitochondria (intrinsic) or tumor necrosis factor (TNF)-family death receptors (extrinsic) as initiators of caspase protease activation and cell death. Because tumor resistance to TNF-family death receptor ligands is a common problem, helping malignant cells evade host immune defenses, we sought to identify compounds that selectively sensitize resistant tumor cells to death receptor ligands. We screened a 50,000-compound library for agents that enhanced anti-FAS antibody-mediated killing of FAS-resistant PPC-1 prostate cancer cell, then did additional analysis of the resulting hits to arrive at eight compounds that selectively sensitized PPC-1 cells to anti-FAS antibody (extrinsic pathway agonist) without altering sensitivity to staurosporine and etoposide (VP-16; intrinsic pathway agonists). These eight compounds did not increase Fas surface levels and also sensitized PPC-1 cells to apoptosis induced by TNF-family member TNF-related apoptosis-inducing ligand, consistent with a post-receptor mechanism. Of these, two reduced expression of c-FLIP, an intracellular antagonist of the extrinsic pathway. Characterization of the effects of the eight compounds on a panel of 10 solid tumor cell lines revealed two structurally distinct compounds that frequently sensitize to extrinsic pathway agonists. Structure-activity relation studies of one of these compounds revealed a pharmacophore from which it should be possible to generate analogues with improved potency. Altogether, these findings show the feasibility of identifying compounds that selectively enhance apoptosis via the extrinsic pathway, thus providing research tools for uncovering resistance mechanisms and a starting point for novel therapeutics aimed at restoring sensitivity of tumor cells to immune effector mechanisms.
Burnham Institute for Medical Research, La Jolla, California 92037, USA.
Aaron D
AD
Schimmer
Michael P
MP
Thomas
Rose
R
Hurren
Marcela
M
Gronda
Maurizio
M
Pellecchia
Gregory R
GR
Pond
Marina
M
Konopleva
Debbie
D
Gurfinkel
Imtiaz A
IA
Mawji
Ewan
E
Brown
John C
JC
Reed
D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology
D000906:Antibodies; D051017:Apoptosis Regulatory Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D005047:Etoposide; D020169:Caspases; D019311:Staurosporine