Blocking tryptophan catabolism reduces triple-negative breast cancer invasive capacity.

Anchorage-independent triple-negative breast cancer (TNBC) cells exhibit elevated levels of the tryptophan (TRP) catabolizing enzyme tryptophan 2,3-dioxygenase 2 (TDO2) compared to the same cells grown in two-dimensional culture. Tracing of 13C11-TRP demonstrated that anchorage-independent culture and/or inflammatory cytokines that activate nuclear factor kappa-light-chain-enhancer of activated B (NFκB) increase TRP catabolism and production of downstream catabolites such as kynurenine (KYN), which activate the aryl hydrocarbon receptor (AhR). TDO2 expression is heterogeneous within TNBC cell lines. To determine the function of TDO2, both pharmacologic inhibition and genetic manipulation were conducted. TDO2 knockdown revealed a compensatory increase in indoleamine 2,3-dioxygenase 1 (IDO1), a non-homologous TRP catabolizing enzyme, indicating that dual inhibition of these two enzymes is necessary to reliably block TRP catabolism. Thus, we tested a newly developed TDO2/IDO1 dual inhibitor, AT-0174, and found that it effectively inhibits TNBC TRP catabolism. Furthermore, AT-0174 treatment or AhR inhibitor significantly decreased TNBC anchorage-independent survival, invasive capacity, and expression of mesenchymal genes and protein, while exogenous KYN increased invasion through AhR-mediated ZEB1 expression. Thus, dual inhibition of TDO2/IDO1 may prove efficacious against TNBC progression.

Platelet releasates mitigate the endotheliopathy of trauma.

BACKGROUND: Platelets are well known for their roles in hemostasis, but they also play a key role in thromboinflammatory pathways by regulating endothelial health, stimulating angiogenesis, and mediating host defense through both contact dependent and independent signaling. When activated, platelets degranulate releasing multiple active substances. We hypothesized that the soluble environment formed by trauma platelet releasates attenuates thromboinflammation via mitigation of trauma induced endothelial permeability and metabolomic reprogramming. METHODS: Blood was collected from injured and healthy patients to generate platelet releasates and plasma in parallel. Permeability of endothelial cells when exposed to trauma platelet releasates (TPR) and plasma (TP) was assessed via resistance measurement by Electric Cell-substrate Impedance Sensing (ECIS). Endothelial cells treated with TPR and TP were subjected to mass spectrometry-based metabolomics. RESULTS: TP increased endothelial permeability, whereas TPR decreased endothelial permeability when compared to untreated cells. When TP and TPR were mixed ex vivo, TPR mitigated TP-induced permeability, with significant increase in AUC compared to TP alone. Metabolomics of TPR and TP demonstrated disrupted redox reactions and anti-inflammatory mechanisms. CONCLUSION: TPRs provide endothelial barrier protection against TP-induced endothelial permeability. Our findings highlight a potential beneficial action of activated platelets on the endothelium in injured patients through disrupted redox reactions and increased antioxidants. Our findings support that soluble signaling from platelet degranulation may mitigate the endotheliopathy of trauma. The clinical implications of this are that activated platelets may prove a promising therapeutic target in the complex integration of thrombosis, endotheliopathy, and inflammation in trauma. LEVEL OF EVIDENCE: Prognostic/Epidemiological, Level III.