title: Development of potent autophagy inhibitors that sensitize oncogenic BRAF V600E mutant melanoma tumor cells to vemurafenib.
abstract: Autophagy is a dynamic cell survival mechanism by which a double-membrane vesicle, or autophagosome, sequesters portions of the cytosol for delivery to the lysosome for recycling. This process can be inhibited using the antimalarial agent chloroquine (CQ), which impairs lysosomal function and prevents autophagosome turnover. Despite its activity, CQ is a relatively inadequate inhibitor that requires high concentrations to disrupt autophagy, highlighting the need for improved small molecules. To address this, we screened a panel of antimalarial agents for autophagy inhibition and chemically synthesized a novel series of acridine and tetrahydroacridine derivatives. Structure-activity relationship studies of the acridine ring led to the discovery of VATG-027 as a potent autophagy inhibitor with a high cytotoxicity profile. In contrast, the tetrahydroacridine VATG-032 showed remarkably little cytotoxicity while still maintaining autophagy inhibition activity, suggesting that both compounds act as autophagy inhibitors with differential effects on cell viability. Further, knockdown of autophagy-related genes showed no effect on cell viability, demonstrating that the ability to inhibit autophagy is separate from the compound cytotoxicity profiles. Next, we determined that both inhibitors function through lysosomal deacidification mechanisms and ultimately disrupt autophagosome turnover. To evaluate the genetic context in which these lysosomotropic inhibitors may be effective, they were tested in patient-derived melanoma cell lines driven by oncogenic BRAF (v-raf murine sarcoma viral oncogene homolog B). We discovered that both inhibitors sensitized melanoma cells to the BRAF V600E inhibitor vemurafenib. Overall, these autophagy inhibitors provide a means to effectively block autophagy and have the potential to sensitize mutant BRAF melanomas to first-line therapies.
authors.affiliation: Laboratory of Systems Biology; Van Andel Research Institute; Grand Rapids, MI USA; Genetics Graduate Program; Michigan State University; East Lansing, MI USA.
authors.forename: Megan L
authors.initials: ML
authors.lastname: Goodall
authors.affiliation: Translational Drug Development (TD2); Scottsdale, AZ USA.
authors.forename: Tong
authors.initials: T
authors.lastname: Wang
authors.affiliation: Laboratory of Systems Biology; Van Andel Research Institute; Grand Rapids, MI USA.
authors.forename: Katie R
authors.initials: KR
authors.lastname: Martin
authors.affiliation: Laboratory of Systems Biology; Van Andel Research Institute; Grand Rapids, MI USA.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Kortus
authors.affiliation: Laboratory of Systems Biology; Van Andel Research Institute; Grand Rapids, MI USA.
authors.forename: Audra L
authors.initials: AL
authors.lastname: Kauffman
authors.affiliation: Translational Genomics Research Institute; Phoenix, AZ USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Trent
authors.affiliation: Translational Drug Development (TD2); Scottsdale, AZ USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Gately
authors.affiliation: Laboratory of Systems Biology; Van Andel Research Institute; Grand Rapids, MI USA.
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: MacKeigan
mesh_terms: D000166:Acridines / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000962:Antimalarials / Q000737:chemistry / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000737:chemistry; D001343:Autophagy / Q000187:drug effects*; D045744:Cell Line, Tumor; D002738:Chloroquine / Q000737:chemistry / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology*; D008247:Lysosomes / Q000187:drug effects; D008545:Melanoma / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D051379:Mice; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D013329:Structure-Activity Relationship; D013449:Sulfonamides / Q000008:administration & dosage / Q000494:pharmacology*; D057170:Translational Research, Biomedical; D014410:Tumor Stem Cell Assay; D000077484:Vemurafenib
chemical_list: D000166:Acridines; D000962:Antimalarials; D000970:Antineoplastic Agents; D007211:Indoles; D013449:Sulfonamides; D000077484:Vemurafenib; D002738:Chloroquine; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: PLX-4032; antimalarial; autophagy; chloroquine; lysosome; melanoma; quinacrine; vemurafenib