Parasympathetic modulation of tumor cell lines biology

EIJAN ANA; DAVEL LILIA; JASNIS MARÍA; MAZZONI ESTEBAN; ESPAÑOL ALEJANDRO; LUSTIG EUGENIA; SALES MARÍA

Creta, Grecia

Congreso; 3 International Symposium on Molecular Medicina and 5 Mundial Congress of Advances in Oncology; 2000

The autonomic nervous system modulates the biological activity of different cell types. Recently it has been described that neurotransmitter receptors are present in tumor cell lines and it would be important to connect the activation of these receptor with the biological behavior of those cells. Our previous results indicated that different murine mammary adenocarcinomas cell lines (LM2, LM3) produced distinct amounts of nitric oxide (NO) measured as nitrites (NO2-) (nmol/106 cell) (LM2:0.11±0.02; LM3:10.0±0.5) and showed different sensitivity to exogenous NO. We investigate if NO production could be related to muscarinic receptor activation by the agonist carbachol (CARB) (10-7M). In LM2 basal nitric oxide synthase (NOS) activity (measured as U14C-citrulline production) (pmol/106 cell) (22.4±5.9)(n=4) is stimulated in 19±2% by CARB. While in LM3 basal NOS activity (8.3±1.4)(n=5) was increased in 35±3% by CARB. The effects of CARB were blunted by 10 uM atropine. In addition preincubation of cells with LPS (50 ug/ml) plus IFNg (20U/ml) (LI) failed to induce NOS activity in LM2 but a 41±3% (n=3) increment in U14C-citrulline production was observed in LM3. Saturation binding assays with the tritiated muscarinic antagonist (3H)-QNB indicate that both LM2 and LM3 express muscarinic acethylcholinr receptors (mAchR). Thus, LM3 shows greater values of maximal number of binding sites /Bmax) (fmol/106 cell) than LM2 (LM·: 5.26±0.05; LM2: 2.55±0.05)(n=4) witch is in accordance with the distinct biological response to the agonist. We carried out in parallel control experiments with the normal mammary epithelial cell line NmuMG. These cells produce basal detectable amounts of NO measured as NO2- (2.7±0.3 nmol/106 cell) (n=3) but they do not respond neither to CARB (2.45±0.32 nmol/106cell) (n=3) nor to LI treatment. Binding experiments with (3H)-QNB do not show specific bound radioligant, pointing to the absence of mAchR in NMuMG cell. Our results let us conclude that malignant phenotype depends in a great extent of changes in the expression of different molecules as neurotransmitter receptors that activate signaling pathways which are probably involved in different processes of cell transformation.