title: Decreased expression and function of alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein in photodynamic therapy-resistant mouse tumor cells.
abstract: Parental and photodynamic therapy (PDT)-resistant mouse, radiation-induced fibrosarcoma cell lines were evaluated using mRNA differential display in an attempt to identify unique transcripts. We detected one transcript that was consistently present in the parental cells but absent in PDT-resistant cells. The transcript was cloned, sequenced, and identified as alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein (alpha-2 MR/LRP). Northern and Western immunoblot analysis confirmed that receptor expression was present in the parental cell line but barely detectable in PDT-resistant cells. Functionality of the receptor was evaluated by exposing cells to Pseudomonas exotoxin A. alpha-2 MR/LRP is responsible for Pseudomonas exotoxin A internalization, and only the parental cells exhibited toxin-mediated cytotoxicity. The binding and endocytosis of activated alpha-2 macroglobulin and lipoproteins by alpha-2 MR/LRP are consistent with modulating uptake and localization of photosensitizers. Our results demonstrate that PDT-resistant murine tumor cells exhibit minimal alpha-2 MR/LRP activity and suggest that this receptor plays a role in PDT sensitivity by modulating photosensitizer uptake and/or subcellular localization.
authors.affiliation: Clayton Ocular Oncology Center, Childrens Hospital Los Angeles 90027, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Luna
authors.forename: A
authors.initials: A
authors.lastname: Ferrario
authors.forename: N
authors.initials: N
authors.lastname: Rucker
authors.forename: C J
authors.initials: CJ
authors.lastname: Gomer
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins; D001483:Base Sequence; D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D004273:DNA, Neoplasm / Q000032:analysis / Q000235:genetics; D017323:Dihematoporphyrin Ether / Q000493:pharmacokinetics / Q000494:pharmacology; D004351:Drug Resistance; D005098:Exotoxins / Q000378:metabolism / Q000494:pharmacology; D005354:Fibrosarcoma / Q000188:drug therapy* / Q000378:metabolism / Q000648:ultrastructure*; D017324:Hematoporphyrin Derivative / Q000493:pharmacokinetics / Q000494:pharmacology; D006414:Hematoporphyrin Photoradiation; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D008969:Molecular Sequence Data; D010778:Photochemotherapy; D012333:RNA, Messenger / Q000032:analysis; D011838:Radiation-Sensitizing Agents / Q000493:pharmacokinetics / Q000494:pharmacology; D011971:Receptors, Immunologic / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D011973:Receptors, LDL / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D014407:Tumor Cells, Cultured; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D004273:DNA, Neoplasm; D017323:Dihematoporphyrin Ether; D005098:Exotoxins; D017324:Hematoporphyrin Derivative; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D012333:RNA, Messenger; D011838:Radiation-Sensitizing Agents; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A