title: Coherence between cellular responses and in vitro splicing inhibition for the anti-tumor drug pladienolide B and its analogs.
abstract: Pladienolide B (PB) is a potent cancer cell growth inhibitor that targets the SF3B1 subunit of the spliceosome. There is considerable interest in the compound as a potential chemotherapeutic, as well as a tool to study SF3B1 function in splicing and cancer development. The molecular structure of PB, a bacterial natural product, contains a 12-member macrolide ring with an extended epoxide-containing side chain. Using a novel concise enantioselective synthesis, we created a series of PB structural analogs and the structurally related compound herboxidiene. We show that two methyl groups in the PB side chain, as well as a feature of the macrolide ring shared with herboxidiene, are required for splicing inhibition in vitro. Unexpectedly, we find that the epoxy group contributes only modestly to PB potency and is not absolutely necessary for activity. The orientations of at least two chiral centers off the macrolide ring have no effect on PB activity. Importantly, the ability of analogs to inhibit splicing in vitro directly correlated with their effects in a series of cellular assays. Those effects likely arise from inhibition of some, but not all, endogenous splicing events in cells, as previously reported for the structurally distinct SF3B1 inhibitor spliceostatin A. Together, our data support the idea that the impact of PB on cells is derived from its ability to impair the function of SF3B1 in splicing and also demonstrate that simplification of the PB scaffold is feasible.
authors.affiliation: From the Department of Molecular Cell and Developmental Biology.
authors.forename: Kerstin A
authors.initials: KA
authors.lastname: Effenberger
authors.forename: David D
authors.initials: DD
authors.lastname: Anderson
authors.forename: Walter M
authors.initials: WM
authors.lastname: Bray
authors.forename: Beth E
authors.initials: BE
authors.lastname: Prichard
authors.forename: Nianchun
authors.initials: N
authors.lastname: Ma
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Adams
authors.forename: Arun K
authors.initials: AK
authors.lastname: Ghosh
authors.forename: Melissa S
authors.initials: MS
authors.lastname: Jurica
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D004852:Epoxy Compounds / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D018942:Macrolides / Q000737:chemistry*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D010750:Phosphoproteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D011714:Pyrans / Q000737:chemistry / Q000494:pharmacology; D012326:RNA Splicing / Q000187:drug effects*; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D013141:Spiro Compounds / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004852:Epoxy Compounds; D018942:Macrolides; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D011714:Pyrans; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear; C112491:SF3B1 protein, human; D013141:Spiro Compounds; C522342:pladienolide B; C553684:spliceostatin A
keywords: Alternative Splicing; Drug Action; Enzyme Inhibitors; Nucleus; RNA Splicing