Involvement of Arachidonic Acid metabolites in Pheochromocytoma biology

COLOMBERO, CECILIA; FERNANDEZ, MARÍA CELIA; SANSO G; VIEITES A; BARONTINI MARTA; PENNISI P; NOWICKI SUSANA

San Francisco

Congreso; 95th Annual Meeting & Expo of The Endocrine Society; 2013

The Endocrine Society

Arachidonic acid can be metabolized into 20-hydroxy and epoxide compounds byCytochrome P450 complex (CYP), CYP4A11 and 4F2 (20-hydroxylases) and CYP 2J2(epoxygenase). These metabolites have proliferative promoting actions in some normal andcancer cells, among other biological effects. Previous studies have shown an increase in theexpression of these isoforms in several types of tumors. Also, a diminished tumoralprogression has been observed after their inhibition. Pheochromocytoma and paragangliomasare rare neuroendocrine, catecholamine secreting tumors, associated with a geneticsyndrome in about 25% of patients. No data on the role of these CYP- generated metabolitesin this kind of tumor is available so far.The aim of this study was to assess the effect of 20-hydroxylated (20-HETE) andepoxygenated (11,12-EET and 14,15-EET) metabolites in the proliferation rate of MousePheochromocytoma Cells 3 (MPC3) and to analyze the expression 20-hydroxylases andepoxygenases in murine and human pheochromocytoma.CYP expression was analyzed by Western Blot and/or PCR in MPC3 cell culture, murinetumors generated by s.c. injection of MPC3 cells, and frozen human tumor samples ofsporadic (n=6) or familial [von Hippel Lindau disease (VHL) (n=5), Multiple EndocrineNeoplasia (MEN 2A) (n=3) or Paraganglioma type 4 (PGL4) (n=2)] pheochromocytomas andparagangliomas.MPC3 cells were incubated with 20-HETE (20uM) or 11,12-EET or 14,15-EET (10nM for both) in low serum medium. 48h incubation resulted in an increase in cell number (increase overcontrol: 20-HETE 64%, n.s.; 11,12-EET 99%, p<0.05; 14,15-EET 141%, p<0.01).CYP4A12 (murine 20-hydroxylase), CYP2C29, 2C38 y 2C44 (murine epoxygenases) weredetected in murine tumors; yet none of them was found in MPC3 cell culture.In human samples, isoform expression was related to the genetic background of the tumor:CYP2J2 was low in all samples except in MEN2A. CYP4A11 and 4F2 were present in allsamples, being the CYP/tubulin ratio significantly different in PGL4 vs. sporadic for CYP4A11(0.94±0.06 vs. 0.25±0.14; p<0.05) and in MEN2A vs. VHL for CYP4F2 (1.99±0.28 vs.1.19±0.18; p<0.05).Our results demonstrate that these CYP- derived arachidonic acid metabolites have an impacton proliferation in MPC3 cell culture. In addition these CYPs are expressed both in humanand murine tumors. Altogether, these results point to a contribution of these metabolites topheochromocytoma biology.