Involvement of extracellular signal-regulated kinase 2 and stress-activated protein kinase/Jun N-terminal kinase activation by transforming growth factor beta in the negative growth control of breast cancer cells.
Although transforming growth factor beta (TGF-beta) is known to be a potent growth inhibitor of breast cancer cells (BCCs), the signaling mechanisms mediating TGF-beta responses have not been defined. We have demonstrated previously that TGF-beta can activate Ras and extracellular signal-regulated kinase (ERK) 1 in untransformed epithelial cells (K. M. Mulder and S. L. Morris, J. Biol. Chem., 267: 5029-5031, 1992; M. T. Hartsough and K. M. Mulder, J. Biol. Chem., 270: 7117-7124, 1995). We have also shown that TGF-beta signaling is altered in epithelial cells when Ras activation is blocked (Hartsough et at., J. Biol. Chem., 271: 22368-22375). Here we demonstrate the ability of the TGF-beta3 isoform to activate the signaling component ERK2 in TGF-beta-sensitive BCCs but not in TGF-beta-resistant cells. The ERK2 isoform was activated by 6-fold within 10 min of TGF-beta3 addition to the TGF-beta-sensitive BCC line Hs578T. Moreover, the IC50 for inhibition of DNA synthesis by TGF-beta3 in this cell line correlated with the EC50 for TGF-beta3 activation of ERK2. In contrast, TGF-beta3 had little effect on either DNA synthesis or ERK2 activation in ZR-75 BCCs lacking the type-II TGF-beta receptors (R(II)), or in ZR-75 BCCs stably transfected with R(II) yet still TGF-beta resistant. In addition, our data demonstrate that TGF-beta3 affected a sustained activation of the stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK) type of mitogen-activated protein kinase (MAPK); maximal induction levels were 2.5-fold above basal values and were attained at 30 min after TGF-beta3 treatment. In contrast, TGF-beta3 did not increase SAPK/JNK activity in the TGF-beta-resistant ZR-75 R(II) BCCs. Our data provide the first evidence that TGF-beta activation of ERK2 and SAPK/JNK is associated with negative growth control of BCCs. This is also the first demonstration that TGF-beta can activate the SAPK/JNK type of MAPK and that the TGF-beta3 isoform can regulate MAPK activity.
Frey
R S
RS
Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Mulder
K M
KM
D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004273:DNA, Neoplasm / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D019950:Mitogen-Activated Protein Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D004273:DNA, Neoplasm; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases