Tumor-associated macrophages and individual chemo-susceptibility are influenced by iron chelation in human slice cultures of gastric cancer.

Purpose: Presence of tumor-associated macrophages (TAM) and high levels of ferritin and lipocalin 2 (Lcn2) in the tumor microenvironment are associated with poor prognosis in many types of cancer. Here we investigate whether iron deprivation influences TAM phenotype and chemotherapy resistance in tumor slice cultures (TSC) of gastric cancer. Results: TAM remained morphologically and functionally stable for four DIV. DFO treatment for 72 h decreased ferritin expression in TAM and in the tumor stroma but did not alter Lcn2 expression. TAM phenotype was altered after 72 h of cisplatin or DFO treatment compared with control conditions. Single DFO treatment and combined treatment with cytotoxic drugs significantly increased tumor cell apoptosis in TSC of gastric cancer. Methods: TSC were manufactured by cutting tissue of gastric cancer resection specimens in 350 µm thick slices and cultivating them under standard conditions on a filter membrane, at an air-liquid interface. After 24 h ex vivo, TSC were treated with irinotecan (100 nM) or cisplatin (10 µM) alone and in combination with deferoxamine (DFO; 10 µM, 100 µM), respectively, for 72 h. After four days in vitro (DIV) the TSC were fixated with paraformaldehyde, paraffin embedded and analyzed by immunohistochemistry for apoptosis (cPARP), proliferation (Ki67), TAM (CD68, CD163), ferritin, and Lcn2 expression. Conclusions: TAM are well preserved and can be studied in TSC of gastric cancer. Iron deprivation significantly increased tumor cell apoptosis.

Functional role of the extracellular N-terminal domain of neuropeptide Y subfamily receptors in membrane integration and agonist-stimulated internalization.

The N terminus is the most variable element in G protein-coupled receptors (GPCRs), ranging from seven residues up to approximately 5900 residues. For family B and C GPCRs it is described that at least part of the ligand binding site is located within the N terminus. Here we investigated the role of the N terminus in the neuropeptide Y receptor family, which belongs to the class A of GPCRs. We cloned differentially truncated Y receptor mutants, in which the N terminus was partially or completely deleted. We found, that eight amino acids are sufficient for full ligand binding and signal transduction activity. Interestingly, we could show that no specific amino acids but rather the extension of the first transmembrane helix by any residues is sufficient for receptor activity but also for membrane integration in case of the hY(1) and the hY(4) receptors. In contrast, the complete deletion of the N terminus in the hY(2) receptors resulted in a mutant that is fully integrated in the membrane but does not bind the ligand very well and internalizes much slower compared to the wild type receptor. Interestingly, also these effects could be reverted by any N-terminal extension. Accordingly, the most important function of the N termini seems to be the stabilization of the first transmembrane helix to ensure the correct receptor structure, which obviously is essential for ligand binding, integration into the cell membrane and receptor internalization.