u-0126 and Pheochromocytoma

Glial cell line-derived neurotrophic factor (GDNF) can induce neuron-like differentiation of mouse pheochromocytoma (MPC) cell lines derived from mice with a heterozygous knockout mutation of nf1, the murine counterpart of the human gene mutated in neurofibromatosis type 1 (NF1). Here, we show that GDNF-induced differentiation in the MPC 862L cell line is mediated by the MEK/extracellular signal-regulated kinase (ERK) pathway. Neurite outgrowth, increased expression of growth-associated protein 43, and decreased incorporation of bromodeoxyuridine (BrdU) were induced by treatment with GDNF, H-RasV12, or a constitutively active MEK2. GDNF also induces leukemia inhibitory factor (LIF) via the MEK/ERK pathway, and LIF itself can elicit these differentiative changes via a cell-extrinsic autocrine/paracrine pathway. Treatment with anti-LIF neutralizing antibody depleted the differentiative activity of the conditioned medium from cells stimulated for MEK/ERK signaling, while recombinant LIF could induce differentiation in MPC cells, indicating that LIF is the sole factor with differentiative activity. LIF could activate MEK1/2 and STAT3, but LIF-induced differentiation was blocked only by the MEK1/2-specific inhibitor U0126, indicating that the MEK/ERK pathway is necessary for LIF action in MPC cells. Our findings suggest that LIF may be utilized for signaling mediated by GDNF and may be important in the pathobiology of neuroendocrine tumors.

Topics: Animals; Butadienes; Cell Differentiation; GAP-43 Protein; Genes, ras; Glial Cell Line-Derived Neurotrophic Factor; Interleukin-6; Intracellular Signaling Peptides and Proteins; Leukemia Inhibitory Factor; MAP Kinase Kinase 1; MAP Kinase Kinase Kinase 2; Mice; Mice, Knockout; Mitogen-Activated Protein Kinases; Nerve Growth Factors; Neurites; Neurofibromin 1; Nitriles; Pheochromocytoma; Proteins; Tumor Cells, Cultured

Adrenergic mouse pheochromocytoma (MPC) cells from heterozygous neurofibromatosis knockout mice show little or no expression of the NGF receptor trk A and do not undergo neuronal differentiation in response to NGF. However, they express high levels of receptor tyrosine kinase, Ret, and GDNF family receptor alpha(1) (GFRalpha(1)) in vivo and in vitro and respond to glial cell line-derived neurotrophic factor (GDNF). In addition, they form short processes in response to PACAP or cyclic AMP. Morphological effects of GDNF, PACAP, or cyclic AMP are similar to those of NGF, PACAP, or cyclic AMP on PC12 cells, and all three agents cause downregulation of PNMT mRNA. The MAP kinase kinase inhibitor U0126 inhibits both baseline proliferation and stimulated process outgrowth, consistent with a model in which sustained low-level ERK activation drives proliferation, and more intense activation drives neuronal differentiation. The sensitivity of MPC cells to U0126 both may reflect mechanisms that cause pheochromocytomas in neurofibromatosis and aid in their clarification.

Topics: Animals; Butadienes; Cell Division; Cyclic AMP; Down-Regulation; Enzyme Inhibitors; Mice; Mice, Knockout; Mitogen-Activated Protein Kinases; Neurofibromatoses; Nitriles; PC12 Cells; Pheochromocytoma; Rats; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors; Tumor Cells, Cultured