Details

Autor(en) / Beteiligte

• Calipel, Armelle
• Mouriaux, Frédéric
• Glotin, Anne-Lise
• Malecaze, François
• Faussat, Anne-Marie
• Mascarelli, Frédéric

Titel

Extracellular Signal-regulated Kinase-dependent Proliferation Is Mediated through the Protein Kinase A/B-Raf Pathway in Human Uveal Melanoma Cells

Ist Teil von

• The Journal of biological chemistry, 2006-04, Vol.281 (14), p.9238-9250

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2006

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Mutated B-Raf-mediated constitutive activation of ERK1/2 is involved in about 66% of cutaneous melanoma. By contrast, activating mutations in B-RAF are rare in ocular melanoma. This study aimed to determine the role of wild-type B-Raf (WTB-Raf) in uveal melanoma cell growth. We used cell lines derived from primary tumors of uveal melanoma to assess the role of WTB-Raf in cell proliferation and to characterize its upstream regulators and downstream effectors. Melanoma cell lines expressing WTB-Raf and WTRas grew with similar proliferation rates, showed constitutive activation of ERK1/2, and had similar levels of B-Raf expression and B-Raf kinase activity as melanoma cell lines expressing the activating V600E mutation (V600EB-Raf). They were equally as sensitive to pharmacological inhibition of MEK1/2 for cell proliferation and transformation as V600EB-Raf cells. siRNA-mediated depletion of Raf-1 did not affect either ERK1/2 activation, whereas siRNA-mediated depletion of B-Raf reduced cell proliferation by up to 65% through the inhibition of ERK1/2 activation, irrespective of the mutational status of B-Raf. Pharmacological inhibition of cAMP-dependent protein kinase (PKA) and siRNA-mediated depletion of PKA greatly reduced B-Raf activity, ERK1/2 activation, and cell proliferation in WTB-Raf cells, whereas it did not affect V600EB-Raf cells, demonstrating a key role of PKA in mediating WTB-Raf/ERK signaling for uveal melanoma cell growth. Moreover, inactivation or depletion of PKA did not affect Rap-1 activity, and Rap-1 depletion did not affect either B-Raf activity or ERK1/2 activation. This ruled out a role for Rap1 in the PKA-mediated B-Raf/ERK activation in WTB-Raf cells. Finally, we demonstrated the importance of cyclin D1 in mediating PKA/WTB-Raf signaling for cell proliferation. Altogether, our results suggest that the PKA/B-Raf pathway is a potential target for therapeutic strategies against WTB-Raf-expressing uveal melanoma.