Numerous antiangiogenic agents are approved for the treatment of oncological diseases. However, almost all patients develop evasive resistance mechanisms against antiangiogenic therapies. Currently no predictive biomarker for therapy resistance or response has been established. Therefore, the aim of our study was to identify biomarkers predicting the development of therapy resistance in patients with hepatocellular cancer (n = 11), renal cell cancer (n = 7) and non-small cell lung cancer (n = 2). Thereby we measured levels of angiogenic growth factors, tumor perfusion, circulating endothelial cells (CEC), circulating endothelial progenitor cells (CEP) and tumor endothelial markers (TEM) in patients during the course of therapy with antiangiogenic agents, and correlated them with the time to antiangiogenic progression (aTTP). Importantly, at disease progression, we observed an increase of proangiogenic factors, upregulation of CEC/CEP levels and downregulation of TEMs, such as Robo4 and endothelial cell-specific chemotaxis regulator (ECSCR), reflecting the formation of torturous tumor vessels. Increased TEM expression levels tended to correlate with prolonged aTTP (ECSCR high = 275 days vs. ECSCR low = 92.5 days; p = 0.07 and for Robo4 high = 387 days vs. Robo4 low = 90.0 days; p = 0.08). This indicates that loss of vascular stabilization factors aggravates the development of antiangiogenic resistance. Thus, our observations confirm that CEP/CEC populations, proangiogenic cytokines and TEMs contribute to evasive resistance in antiangiogenic treated patients. Higher TEM expression during disease progression may have clinical and pathophysiological implications, however, validation of our results is warranted for further biomarker development.
Background/aims The present study was designed to investigate whether the acute phase protein alpha-1-antitrypsin (α1-AT), which has an inhibitory effect on transferrin (tf) receptor-mediated iron uptake in K562 and THP1 cells, has a similar effect in PLC/PRF/5 cells. This hepatic cell line is of specific interest because it is infected with hepatitis B virus (HBV). Therefore, we addressed the additional question whether α1-AT has any effect on cellular protein synthesis and replication of HBV in PLC/PRF/5 cells. Methods Cells were incubated with various concentrations of α1-AT, dexamethasone, IL-6 and desferrioxamine. HBs-AG, alpha-fetoprotein and albumin concentrations in culture media were measured using commercially available methods. For equilibrium inhibition binding experiments, cells were incubated with 85–182 pmol/l [125l]tf. To study the potential effect of α1-AT on DMA synthesis we measured the incorporation of [3H]thymidine into DNA. Results In equilibrium saturation binding experiments, [125l]tf bound to PLC/PRF/5 cells with KD 17.45 ± 4.57 nM and a maximum density of binding sites of 267 285 ± 39 915 sites/cell. In inhibition studies α1-AT demonstrated an apparently monophasic inhibition of [125l]tf to its receptor. At concentrations > 30 μmo\/\ α1AT inhibited the growth of PLC/PRF/5 cells up to approximately 50%. The inhibitory effect of α1-AT on DNA synthesis was not as potent as that on growth. At the highest concentration of 100 μmol/l, α1-AT produced a 35% maximum inhibition of [3H]thymidine incorporation. Incubating PLC/PRF/5 cells with corticosteroids enhanced HBs-AG release significantly. Interestingly, α1-AT showed the same pattern of effects on cell metabolism and HBs-AG release as the corticosteroids. When we incubated the cells with 50 μmol/1 α1-AT, alpha-fetoprotein production increased significantly and HBs-AG release almost doubled. Conclusion We have to assume that there is a specific mechanism inducing HBs-AG release by α1AT, as has been shown to be the case with steroids.
