EGF activates an inducible survival response via the RAS-> Erk-1/2 pathway to counteract interferon-alpha-mediated apoptosis in epidermoid cancer cells.
The mechanisms of tumor cell resistance to interferon-alpha (IFNalpha) are at present mostly unsolved. We have previously demonstrated that IFNalpha induces apoptosis on epidermoid cancer cells and EGF antagonizes this effect. We have also found that IFNalpha-induced apoptosis depends upon activation of the NH(2)-terminal Jun kinase-1 (Jnk-1) and p(38) mitogen-activated protein kinase, and that these effects are also antagonized by EGF. At the same time, IFNalpha increases the expression and function of the epidermal growth factor receptor (EGF-R). Here we report that the apoptosis induced by IFNalpha occurs together with activation of caspases 3, 6 and 8 and that EGF also antagonizes this effect. On the basis of these results, we have hypothesized that the increased EGF-R expression and function could represent an inducible survival response that might protect tumor cells from apoptosis caused by IFNalpha via extracellular signal regulated kinase 1 and 2 (Erk-1/2) cascades. We have found an increased activity of Ras and Raf-1 in IFNalpha-treated cells. Moreover, IFNalpha induces a 50% increase of the phosphorylated isoforms and enzymatic activity of Erk-1/2. We have also demonstrated that the inhibition of Ras activity induced by the transfection of the dominant negative Ras plasmid RASN17 and the inhibition of Mek-1 with PD098059 strongly potentiates the apoptosis induced by IFNalpha. Moreover, the selective inhibition of this pathway abrogates the counteracting effect of EGF on the IFNalpha-induced apoptosis. All these findings suggest that epidermoid tumor cells counteract the IFNalpha-induced apoptosis through a survival pathway that involves the hyperactivation of the EGF-dependent Ras->Erk signalling. The selective targeting of this pathway appears to be a promising approach in order to enhance the antitumor activity of IFNalpha.
Caraglia
M
M
Dipartimento di Biochimica e Biofisica, Seconda Universitá di Napoli, Naples, Italy.
Tagliaferri
P
P
Marra
M
M
Giuberti
G
G
Budillon
A
A
Gennaro
E Di
ED
Pepe
S
S
Vitale
G
G
Improta
S
S
Tassone
P
P
Venuta
S
S
Bianco
A R
AR
Abbruzzese
A
A
D017209:Apoptosis / Q000187:drug effects*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism / Q000494:pharmacology*; D007624:KB Cells; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000032:analysis / Q000187:drug effects; D018631:ras Proteins / Q000378:metabolism*
D004791:Enzyme Inhibitors; D005419:Flavonoids; D016898:Interferon-alpha; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases; D018631:ras Proteins; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one