Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine, originally discovered for its eponymous effect and now known for pleiotropic biologic properties in immunology and oncology. Circulating MIF levels are elevated in several types of human cancer including prostate cancer. MIF is released presumably by both stromal and tumor cells and enhances malignant growth and metastasis by diverse mechanisms, such as stimulating tumor cell proliferation, suppressing apoptotic death, facilitating invasion of the extracellular matrix, and promoting angiogenesis. Recently described fully human anti-MIF antibodies were tested in vitro and in vivo for their ability to influence growth rate and invasion of the human PC3 prostate cancer cell line. In vitro, the selected candidate antibodies BaxG03, BaxB01, and BaxM159 reduced cell growth and viability by inhibiting MIF-induced phosphorylation of the central kinases p44/42 mitogen-activated protein kinase [extracellular signal-regulated kinase-1 and -2 (ERK1/2)] and protein kinase B (AKT). Incubation of cells in the presence of the antibodies also promoted activation of caspase-3/7. The antibodies furthermore inhibited MIF-promoted invasion and chemotaxis as transmigration through Matrigel along a MIF gradient was impaired. In vivo, pharmacokinetic parameters (half-life, volume of distribution, and bioavailability) of the antibodies were determined and a proof-of-concept was obtained in a PC3-xenograft mouse model. Treatment with human anti-MIF antibodies blunted xenograft tumor growth in a dose-dependent manner. We therefore conclude that the anti-MIF antibodies described neutralize some of the key tumor-promoting activities of MIF and thus limit tumor growth in vivo.

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3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1107-1114.

Background: The A2A receptor is known to accumulate in the endoplasmic reticulum.Results: Mass spectrometry identified molecular chaperones (HSP90 and HSP70) bound to the A2A receptor.Conclusion: Sequential recruitment of chaperones to the cytosolic face of the A2A receptor is consistent with a heat-shock protein relay assisting folding.Significance: The observations are consistent with a chaperone/COPII exchange model, where heat-shock proteins bound to the receptor preclude its premature ER export.

Ibogaine is a psychoactive indole alkaloid. Its use as an antiaddictive agent has been accompanied by QT prolongation and cardiac arrhythmias, which are most likely caused by human ether a go-go-related gene (hERG) potassium channel inhibition. Therefore, we studied in detail the interaction of ibogaine with hERG channels heterologously expressed in mammalian kidney tsA-201 cells. Currents through hERG channels were blocked regardless of whether ibogaine was applied via the extracellular or intracellular solution. The extent of inhibition was determined by the relative pH values. Block occurred during activation of the channels and was not observed for resting channels. With increasing depolarizations, ibogaine block grew and developed faster. Steady-state activation and inactivation of the channel were shifted to more negative potentials. Deactivation was slowed, whereas inactivation was accelerated. Mutations in the binding site reported for other hERG channel blockers (Y652A and F656A) reduced the potency of ibogaine, whereas an inactivation-deficient double mutant (G628C/S631C) was as sensitive as wild-type channels. Molecular drug docking indicated binding within the inner cavity of the channel independently of the protonation of ibogaine. Experimental current traces were fit to a kinetic model of hERG channel gating, revealing preferential binding of ibogaine to the open and inactivated state. Taken together, these findings show that ibogaine blocks hERG channels from the cytosolic side either in its charged form alone or in company with its uncharged form and alters the currents by changing the relative contribution of channel states over time.

Background: The A2A receptor engages Gs by restricted collision coupling and lacks a palmitoyl moiety in its C terminus.Results: Engineering palmitoylated cysteine into the C terminus relieved restricted collision coupling and resulted in accelerated diffusion of the agonist-liganded A2A receptor.Conclusion: Restricted collision coupling arises from limits imposed on receptor diffusion.Significance: Agonist induced confinement of the A2A receptor in a structure consistent with a lipid raft.

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Background: Agonist activation slows diffusion of the A2A receptor in the lipid bilayer.Results: In hippocampal neurons, the agonist-induced decrease in mobility was accounted for by both the hydrophobic receptor core and its extended C terminus, which recruited SAP102.Conclusion: The observations are consistent with two diffusion states of the A2A receptor in neurons.Significance: SAP102 regulates access of the A2A receptor to a compartment with restricted mobility.