title: A peptide nucleic acid targeting nuclear RAD51 sensitizes multiple myeloma cells to melphalan treatment.
abstract: RAD51-mediated recombinational repair is elevated in multiple myeloma (MM) and predicts poor prognosis. RAD51 has been targeted to selectively sensitize and/or kill tumor cells. Here, we employed a peptide nucleic acid (PNA) to inhibit RAD51 expression in MM cells. We constructed a PNA complementary to a unique segment of the RAD51 gene promoter, spanning the transcription start site, and conjugated it to a nuclear localization signal (PKKKRKV) to enhance cellular uptake and nuclear delivery without transfection reagents. This synthetic construct, (PNArad51_nls), significantly reduced RAD51 transcripts in MM cells, and markedly reduced the number and intensity of de novo and melphalan-induced nuclear RAD51 foci, while increasing the level of melphalan-induced γH2AX foci. Melphalan alone markedly induced the expression of 5 other genes involved in homologous-recombination repair, yet suppression of RAD51 by PNArad51_nls was sufficient to synergize with melphalan, producing significant synthetic lethality of MM cells in vitro. In a SCID-rab mouse model mimicking the MM bone marrow microenvironment, treatment with PNArad51_nls ± melphalan significantly suppressed tumor growth after 2 weeks, whereas melphalan plus control PNArad4µ_nls was ineffectual. This study highlights the importance of RAD51 in myeloma growth and is the first to demonstrate that anti-RAD51 PNA can potentiate conventional MM chemotherapy.
authors.affiliation: a McClellan Veterans Medical Center; Central Arkansas Veterans Healthcare System ; Little Rock , AR USA.
authors.forename: David Abasiwani
authors.initials: DA
authors.lastname: Alagpulinsa
authors.forename: Shmuel
authors.initials: S
authors.lastname: Yaccoby
authors.forename: Srinivas
authors.initials: S
authors.lastname: Ayyadevara
authors.forename: Robert Joseph
authors.initials: RJ
authors.lastname: Shmookler Reis
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000187:drug effects; D004195:Disease Models, Animal; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D019398:Genes, BRCA1; D006801:Humans; D008558:Melphalan / Q000494:pharmacology*; D051379:Mice; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020135:Peptide Nucleic Acids / Q000494:pharmacology*; D051135:Rad51 Recombinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects; D014158:Transcription, Genetic; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D020135:Peptide Nucleic Acids; D051135:Rad51 Recombinase; D008558:Melphalan
keywords: PNA, peptide nucleic acid.; RAD51; homologous recombination; melphalan; myeloma; peptide nucleic acid; γH2AX