Ryan J. Hansen

Autophagy is a protein and organelle degradation pathway that is involved in diverse diseases, including cancer. Recent evidence suggests that autophagy is a cell survival mechanism in tumor cells and that its inhibition, especially in combination with other therapy, could be beneficial but it remains unclear if all cancer cells behave the same way when autophagy is inhibited. We inhibited autophagy in a panel of breast cancer cell lines and found that some of them are dependent on autophagy for survival even in nutrient rich conditions without any additional stress, whereas others need autophagy only when stressed. Survival under unstressed conditions is due to cell type-specific autophagy regulation of STAT3 activity and this phenotype is enriched in triple-negative cell lines. This autophagy-dependency affects response to therapy because autophagy inhibition reduced tumor growth in vivo in autophagy-dependent but not in autophagy-independent breast tumors, whereas combination treatment with autophagy inhibitors and other agent was preferentially synergistic in autophagy-dependent cells. These results imply that autophagy-dependence represents a tumor cell-specific characteristic where autophagy inhibition will be more effective. Moreover, our results suggest that autophagy inhibition might be a potential therapeutic strategy for triple-negative breast cancers, which currently lack an effective targeted treatment.

Hydrogen sulfide is an important biological signaling molecule and an important environmental target for detection. A major challenge in developing H2S detection methods is separating the often similar reactivity of thiols and other nucleophiles from H2S. To address this need, the nucleophilic aromatic substitution (SNAr) reaction of H2S with electron-poor aromatic electrophiles was developed as a strategy to separate H2S and thiol reactivity. Treatment of aqueous solutions of nitrobenzofurazan (7-nitro-1,2,3-benzoxadiazole, NBD) thioethers with H2S resulted in thiol extrusion and formation of nitrobenzofurazan thiol (λmax = 534 nm). This reactivity allows for unwanted thioether products to be converted to the desired nitrobenzofurazan thiol upon reaction with H2S. The scope of the reaction was investigated using a Hammett linear free energy relationship study, and the determined ρ = +0.34 is consistent with the proposed SN2Ar reaction mechanism. The efficacy of the developed probes was demonstrated in buffer and in serum with associated submicromolar detection limits as low as 190 nM (buffer) and 380 nM (serum). Furthermore, the sigmoidal response of nitrobenzofurazan electrophiles with H2S can be fit to accurately quantify H2S. The developed detection strategy offers a manifold for H2S detection that we foresee being applied in various future applications.

We have recently shown that intravenous immunoglobulin (IVIG) therapy leads to an increased rate of anti-platelet antibody clearance in an animal model of immune thrombocytopenia. The present study was performed to confirm the importance of the FcRn receptor in mediating this effect of IVIG. The pharmacokinetics of an anti-platelet antibody, 7E3, were studied in mice lacking expression of FcRn and in control mice, both in the presence and absence of IVIG. IVIG increased the clearance of 7E3 in mice with functioning FcRn receptors, with an average clearance value of 14.4 +/- 1.4 ml/d/kg in IVIG treated mice vs. 5.2 +/- 0.3 ml/d/kg in controls (P <0.001). In mice lacking expression of FcRn, IVIG treatment did not increase 7E3 clearance (61.0 +/- 3.6 ml/d/kg vs. 71.5 +/- 4.0 ml/d/kg in controls). Thus, these data support the hypothesis that IVIG increases antibody elimination via saturation of FcRn.