Polyaldol Synthesis by Direct Organocatalyzed Crossed Polymerization of Bis(ketones) and Bis(aldehydes)

Synthesis of polyaldols consisting of β-keto alcohol monomer units is described. These polymers were obtained by direct step-growth polymerization of purposely designed bifunctional enolizable bis­(ketone) monomers playing the role of nucleophilic donors, and activated nonenolizable bis­(aldehyde)­s serving as electrophilic acceptors. Monofunctional ketone and aldehyde homologues were first synthesized as models to establish the aldol reaction conditions using reaction partners at stoichiometry. A bifunctional organocatalytic system consisting of pyrrolidine in conjunction with acetic acid allowed performing polyaldolizations of stoichiometric amounts of the bis­(aldehyde) and the bis­(ketone) in solution in THF, DMSO, or DMF, at room temperature. However, polar solvents and/or prolonged reaction time induced further aldol reactions between aldol units of polymer chains, as indicated by the relatively broad molecular weight distribution of related polyaldols observed by size exclusion chromatography. Analysis by NMR spectroscopy confirmed the formation of β-keto alcohol units, but also evidenced that the latter were also partly dehydrated into conjugated ketones via a crotonization reaction (from 20 to 33% depending on the structure of the initial monomers)

Resistance to sunitinib in renal clear cell carcinoma results from sequestration in lysosomes and inhibition of the autophagic flux

<p>Metastatic renal cell carcinomas (mRCC) are highly vascularized tumors that are a paradigm for the treatment with antiangiogenesis drugs targeting the vascular endothelial growth factor (VEGF) pathway. The available drugs increase the time to progression but are not curative and the patients eventually relapse. In this study we have focused our attention on the molecular mechanisms leading to resistance to sunitinib, the first line treatment of mRCC. Because of the anarchic vascularization of tumors the core of mRCC tumors receives only suboptimal concentrations of the drug. To mimic this in vivo situation, which is encountered in a neoadjuvant setting, we exposed sunitinib-sensitive mRCC cells to concentrations of sunitinib below the concentration of the drug that gives 50% inhibition of cell proliferation (IC50). At these concentrations, sunitinib accumulated in lysosomes, which downregulated the activity of the lysosomal protease CTSB (cathepsin B) and led to incomplete autophagic flux. Amino acid deprivation initiates autophagy enhanced sunitinib resistance through the amplification of autolysosome formation. Sunitinib stimulated the expression of ABCB1 (ATP-binding cassette, sub-family B [MDR/TAP], member 1), which participates in the accumulation of the drug in autolysosomes and favor its cellular efflux. Inhibition of this transporter by elacridar or the permeabilization of lysosome membranes with Leu-Leu-O-methyl (LLOM) resensitized mRCC cells that were resistant to concentrations of sunitinib superior to the IC50. Proteasome inhibitors also induced the death of resistant cells suggesting that the ubiquitin-proteasome system compensates inhibition of autophagy to maintain a cellular homeostasis. Based on our results we propose a new therapeutic approach combining sunitinib with molecules that prevent lysosomal accumulation or inhibit the proteasome.</p