Radical ring-opening polymerization of sustainably-derived thionoisochromanone.

We present the synthesis, characterization and radical ring-opening polymerization (rROP) capabilities of thionoisochromanone (TIC), a fungi-derivable thionolactone. TIC is the first reported six-membered thionolactone to readily homopolymerize under free radical conditions without the presence of a dormant comonomer or repeated initiation. Even more, the resulting polymer is fully degradable under mild, basic conditions. Computations providing molecular-level insights into the mechanistic and energetic details of polymerization identified a unique S,S,O-orthoester intermediate that leads to a sustained chain-end. This sustained chain-end allowed for the synthesis of a block copolymer of TIC and styrene under entirely free radical conditions without explicit radical control methods such as reversible addition-fragmentation chain transfer polymerization (RAFT). We also report the statistical copolymerization of ring-retained TIC and styrene, confirmed by elemental analysis and energy-dispersive X-ray spectroscopy (EDX). Computations into the energetic details of copolymerization indicate kinetic drivers for ring-retaining behavior. This work provides the first example of a sustainable feedstock for rROP and provides the field with the first six-membered monomer susceptible to rROP, expanding the monomer scope to aid our fundamental understanding of thionolactone rROP behavior.

New bisphosphomide ligands, 1,3-phenylenebis((diphenylphosphino)methanone) and (2-bromo-1,3-phenylene)bis((diphenylphosphino)methanone): synthesis, coordination behavior, DFT calculations and catalytic studies.

The bisphosphomide, 1,3-{Ph2PC(O)}2C6H4 (1), was prepared by the reaction of isophthaloyl chloride with diphenylphosphine in the presence of triethylamine. The corresponding bromo-derivative, 2-Br-1,3-{Ph2PC(O)}2C6H3 (2), was obtained by the reaction of 2-bromoisophthaloyl chloride with diphenylphosphine. The reaction of 1 with elemental sulfur or selenium yielded the bis(chalcogenides), 1,3-{Ph2P(S)C(O)}2C6H4 (3) and {1,3-Ph2P(Se)C(O)}2C6H4 (4). The reaction between 1 and [Ru(η(6)-p-cymene)Cl2]2 and [Pd(η(3)-C3H5)Cl]2 in 1 : 1 stoichiometry yielded the corresponding binuclear complexes, [Ru2(η(6)-p-cymene)2Cl4{1,3-{Ph2PC(O)}2(C6H4)}] (5) and [Pd2(η(3)-C3H5)2Cl2{1,3-{Ph2PC(O)}2(C6H4)}] (6). The reaction of 1 with AgClO4 followed by the addition of [Pd(COD)Cl2] at room temperature resulted in the formation of a pincer complex [PdCl{2,6-{Ph2PC(O)}2(C6H3)}] (9), via transmetallation. Pincer complex formation through C-H activation requires drastic conditions and yields are generally moderate. The oxidative addition reaction between 2 and [Ni(COD)2] gave a pincer complex [NiBr{2,6-{Ph2PC(O)}2(C6H3)}] (8), whereas the 2:1 reaction of 2 with [Pd2(dba)3] yielded the palladium analogue [PdBr{2,6-{Ph2PC(O)}2(C6H3)}] (9) in quantitative yield. The reaction between 1 and CuX in a 1:1 molar ratio produced binuclear complexes, [Cu2(µ-X)2{1,3-{Ph2PC(O)}2(C6H4)}2] (10, X = Cl; 11, X = Br; 12, X = I), whereas the reaction between 1 and [Cu(NCCH3)4]BF4 led to the isolation of a spirocyclic complex, [Cu(CH3CN)2{1,3-{Ph2PC(O)}2(C6H4)}]BF4 (13). The silver complexes [Ag2(µ-ClO4)2{1,3-{Ph2PC(O)}2(C6H4)}2] (14), [Ag2(µ-OTf)2{1,3-{Ph2PC(O)}2(C6H4)}2] (15) and [Ag2X2{1,3-{Ph2PC(O)}2(C6H4)}] (16, X = ClO4; 17, X = OTf) were obtained by treating 1 with AgClO4 or AgOTf in 1:1 or 1:2 molar ratios. The reactions of 1 with [AuCl(SMe2)] in 1 : 1 and 1 : 2 molar ratios afforded mono- and binuclear complexes, [AuCl{1,3-{Ph2PC(O)}2(C6H4)}2] (18) and [Au2Cl2{1,3-{Ph2PC(O)}2(C6H4)}AuCl] (19), in good yield. The structures of complexes 5, 7-10, 12 and 14a were confirmed by single-crystal X-ray diffraction studies. DFT calculations were performed in order to gain additional insights into the structure and bonding of the pincer complexes. An additional analysis of the orbital interactions in the case of palladium complex 9 is also included. The in situ generated rhodium complex of bisphosphomide 1 showed moderate to good selectivity in the hydroformylation of hex-1-ene and styrene derivatives.

Cell proliferation and cell cycle alterations in oesophageal p53-mutated cancer cells treated with cisplatin in combination with photodynamic therapy.

OBJECTIVES: The major goal of anti-cancer therapies is selective destruction of tumour cells with minimum side effects on normal cells. Towards this aim, combination of different therapeutic modalities has been evaluated for improving control of neoplastic diseases and quality of life for the patient. Photodynamic therapy (PDT) is a procedure for treatment of various types of cancer, but its combination with other established treatments has not been evaluated in detail. We have used KYSE-510 cells from a human oesophageal carcinoma as an in vitro model to investigate whether cisplatin (CDDP) could be combined with PDT to increase cell death with respect to single treatments. MATERIALS AND METHODS: p53-mutated KYSE-510 cells were treated with CDDP alone or in combination with PDT. Analyses of cell viability, cell cycle progression and apoptosis induction were carried out at specific times after treatments. RESULTS: Decrease in cell viability, cell cycle arrest at the G(2)/M- and S-phases boundary, and apoptosis induction were observed after single and combined treatments. CONCLUSIONS: Our results show that low CDDP doses (0.25-1 microm) induce cell mortality and cell cycle perturbation, which were more evident when given in combination with PDT, but in contrast to work of other authors no synergistic activity was found. Apoptosis occurred via intrinsic pathways in treated cells, although it did not represent the predominant mode of cell death.

Low doses of cisplatin or gemcitabine plus Photofrin/photodynamic therapy: Disjointed cell cycle phase-related activity accounts for synergistic outcome in metastatic non-small cell lung cancer cells (H1299).

We compared the effects of monotherapy (photodynamic therapy or chemotherapy) versus combination therapy (photodynamic therapy plus a specific drug) on the non-small cell lung cancer cell line H1299. Our aim was to evaluate whether the additive/synergistic effects of combination treatment were such that the cytostatic dose could be reduced without affecting treatment efficacy. Photodynamic therapy was done by irradiating Photofrin-preloaded H1299 p53/p16-null cells with a halogen lamp equipped with a bandpass filter. The cytotoxic drugs used were cis-diammine-dichloroplatinum [II] (CDDP or cisplatin) and 2',2'-difluoro-2'-deoxycytidine (gemcitabine). Various treatment combinations yielded therapeutic effects (trypan blue dye exclusion test) ranging from additive to clearly synergistic, the most effective being a combination of photodynamic therapy and CDDP. To gain insight into the cellular response mechanisms underlying favorable outcomes, we analyzed the H1299 cell cycle profiles and the expression patterns of several key proteins after monotherapy. In our conditions, we found that photodynamic therapy with Photofrin targeted G0-G1 cells, thereby causing cells to accumulate in S phase. In contrast, low-dose CDDP killed cells in S phase, thereby causing an accumulation of G0-G1 cells (and increased p21 expression). Like photodynamic therapy, low-dose gemcitabine targeted G0-G1 cells, which caused a massive accumulation of cells in S phase (and increased cyclin A expression). Although we observed therapeutic reinforcement with both drugs and photodynamic therapy, reinforcement was more pronounced when the drug (CDDP) and photodynamic therapy exert disjointed phase-related cytotoxic activity. Thus, if photodynamic therapy is appropriately tuned, the dose of the cytostatic drug can be reduced without compromising the therapeutic response.

ErbB2 degradation mediated by the co-chaperone protein CHIP.

ErbB2 overexpression contributes to the evolution of a substantial group of human cancers and signifies a poor clinical prognosis. Thus, down-regulation of ErbB2 signaling has emerged as a new anti-cancer strategy. Ubiquitinylation, mediated by the Cbl family of ubiquitin ligases, has emerged as a physiological mechanism of ErbB receptor down-regulation, and this mechanism appears to contribute to ErbB2 down-regulation induced by therapeutic anti-ErbB2 antibodies. Hsp90 inhibitory ansamycin antibiotics such as geldanamycin (GA) induce rapid ubiquitinylation and down-regulation of ErbB2. However, the ubiquitin ligase(s) involved has not been identified. Here, we show that ErbB2 serves as an in vitro substrate for the Hsp70/Hsp90-associated U-box ubiquitin ligase CHIP. Overexpression of wild type CHIP, but not its U-box mutant H260Q, induced ubiquitinylation and reduction in both cell surface and total levels of ectopically expressed or endogenous ErbB2 in vivo, and this effect was additive with that of 17-allylamino-geldanamycin (17-AAG). The CHIP U-box mutant H260Q reduced 17-AAG-induced ErbB2 ubiquitinylation. Wild type ErbB2 and a mutant incapable of association with Cbl (ErbB2 Y1112F) were equally sensitive to CHIP and 17-AAG, implying that Cbl does not play a major role in geldanamycin-induced ErbB2 down-regulation. Both endogenous and ectopically expressed CHIP and ErbB2 coimmunoprecipitated with each other, and this association was enhanced by 17-AAG. Notably, CHIP H260Q induced a dramatic elevation of ErbB2 association with Hsp70 and prevented the 17-AAG-induced dissociation of Hsp90. Our results demonstrate that ErbB2 is a target of CHIP ubiquitin ligase activity and suggest a role for CHIP E3 activity in controlling both the association of Hsp70/Hsp90 chaperones with ErbB2 and the down-regulation of ErbB2 induced by inhibitors of Hsp90.

[3H]taurine and D-[3H]aspartate release from astrocyte cultures are differently regulated by tyrosine kinases.

Volume-dependent anion channels permeable for Cl- and amino acids are thought to play an important role in the homeostasis of cell volume. Astrocytes are the main cell type in the mammalian brain showing volume perturbations under physiological and pathophysiological conditions. We investigated the involvement of tyrosine phosphorylation in hyposmotic medium-induced [3H]taurine and D-[3H]aspartate release from primary astrocyte cultures. The tyrosine kinase inhibitors tyrphostin 23 and tyrphostin A51 partially suppressed the volume-dependent release of [3H]taurine in a dose-dependent manner with half-maximal effects at approximately 40 and 1 microM, respectively. In contrast, the release of D-[3H]aspartate was not significantly affected by these agents in the same concentration range. The inactive analog tyrphostin 1 had no significant effect on the release of both amino acids. The data obtained suggest the existence of at least two volume-dependent anion channels permeable to amino acids in astrocyte cultures. One of these channels is permeable to taurine and is under the control of tyrosine kinase(s). The other is permeable to both taurine and aspartate, but its volume-dependent regulation does not require tyrosine phosphorylation.