The S100A9 (MRP14) protein is abundantly expressed in myeloid cells and has been associated with various inflammatory diseases. The S100A9-deficient mice described here were viable, fertile, and generally of healthy appearance. The myelopoietic potential of the S100A9-null bone marrow was normal. S100A8, the heterodimerization partner of S100A9 was not detectable in peripheral blood cells, suggesting that even a deficiency in both S100A8 and S100A9 proteins was compatible with viable and mature neutrophils. Surprisingly, the invasion of S100A9-deficient leukocytes into the peritoneum and into the skin in vivo was indistinguishable from that in wild-type mice. However, stimulation of S100A9-deficient neutrophils with interleukin-8 in vitro failed to provoke an up-regulation of CD11b. Migration upon a chemotactic stimulus through an endothelial monolayer was markedly diminished in S100A9-deficient neutrophils. Attenuated chemokinesis of the S100A9-deficient neutrophils was observed by using a three-dimensional collagen matrix migration assay. The altered migratory behavior was associated with a microfilament system that was highly polarized in unstimulated S100A9-deficient neutrophils. Our data suggest that loss of the calcium-binding S100A9 protein reduces the responsiveness of the neutrophils upon chemoattractant stimuli at least in vitro. Alternative pathways for neutrophil emigration may be responsible for the lack of any effect in the two in vivo models we have investigated so far.

Supplementary data are available at Bioinformatics online.

Purpose Despite significant progress in cancer research many tumor entities still have an unfavorable prognosis. Activating Transcription Factor 5 (ATF5) is up-regulated in various malignancies and promotes apoptotic resistance. We evaluated the efficacy and mechanisms of the first described synthetic cell-penetrating inhibitor of ATF5 function, CP-d/n-ATF5-S1. Experimental Design Preclinical drug testing was performed in various treatment-resistant cancer cells and in vivo xenograft models. Results CP-d/n-ATF5-S1 reduced the transcript levels of several known direct ATF5 targets. It depleted endogenous ATF5 and induced apoptosis across a broad panel of treatment refractory cancer cell lines, sparing non-neoplastic cells. CP-d/n-ATF5-S1 promoted tumor cell apoptotic susceptibility in part by reducing expression of the deubiquitinase Usp9X and lead to diminished levels of anti-apoptotic Bcl-2 family members Mcl-1 and Bcl-2. In line with this, CP-d/n-ATF5-S1 synergistically enhanced tumor cell apoptosis induced by the BH3-mimetic ABT263 and the death ligand TRAIL. In vivo, CP-d/n-ATF5-S1 attenuated tumor growth as a single compound in melanoma, glioblastoma, prostate cancer and triple-receptor-negative breast cancer xenograft models. Finally, the combination treatment of CP-d/n-ATF5-S1 and ABT263 significantly reduced tumor growth in vivo more efficiently than each reagent on its own. Conclusions Our data support the idea that CP-d/n-ATF5-S1, administered as a single reagent or in combination with other drugs, holds promise as an innovative, safe and efficient anti-neoplastic agent against treatment-resistant cancers.

Endogenous DC electric fields (EF) are present during embryogenesis and are generated in vivo upon wounding, providing guidance cues for directional cell migration (galvanotaxis) required in these processes. To understand the role of beta (beta)4 integrin in directional migration, the migratory paths of either primary human keratinocytes (NHK), beta4 integrin-null human keratinocytes (beta4-), or those in which beta4 integrin was reexpressed (beta4+), were tracked during exposure to EFs of physiological magnitude (100 mV/mm). Although the expression of beta4 integrin had no effect on the rate of cell movement, it was essential for directional (cathodal) migration in the absence of epidermal growth factor (EGF). The addition of EGF potentiated the directional response, suggesting that at least two distinct but synergistic signaling pathways coordinate galvanotaxis. Expression of either a ligand binding-defective beta4 (beta4+AD) or beta4 with a truncated cytoplasmic tail (beta4+CT) resulted in loss of directionality in the absence of EGF, whereas inhibition of Rac1 blinded the cells to the EF even in the presence of EGF. In summary, both the beta4 integrin ligand-binding and cytoplasmic domains together with EGF were required for the synergistic activation of a Rac-dependent signaling pathway that was essential for keratinocyte directional migration in response to a galvanotactic stimulus.