Roles of activated Src and Stat3 signaling in melanoma tumor cell growth.
Activation of protein tyrosine kinases is prevalent in human cancers and previous studies have demonstrated that Stat3 signaling is a point of convergence for many of these tyrosine kinases. Moreover, a critical role for constitutive activation of Stat3 in tumor cell proliferation and survival has been established in diverse cancers. However, the oncogenic signaling pathways in melanoma cells remain to be fully defined. In this study, we demonstrate that Stat3 is constitutively activated in a majority of human melanoma cell lines and tumor specimens examined. Blocking Src tyrosine kinase activity, but not EGF receptor or JAK family kinases, leads to inhibition of Stat3 signaling in melanoma cell lines. Consistent with a role of Src in the pathogenesis of melanoma, we show that c-Src tyrosine kinase is activated in melanoma cell lines. Significantly, melanoma cells undergo apoptosis when either Src kinase activity or Stat3 signaling is inhibited. Blockade of Src or Stat3 is also accompanied by down-regulation of expression of the anti-apoptotic genes, Bcl-x(L) and Mcl-1. These findings demonstrate that Src-activated Stat3 signaling is important for the growth and survival of melanoma tumor cells.
Niu
Guilian
G
Immunology Program, H Lee Moffitt Cancer Center and Research Institute, Department of Oncology, University of South Florida College of Medicine, Tampa, Florida, FL 33612, USA.
Bowman
Tammy
T
Huang
Mei
M
Shivers
Steve
S
Reintgen
Douglas
D
Daud
Adil
A
Chang
Alfred
A
Kraker
Alan
A
Jove
Richard
R
Yu
Hua
H
D017209:Apoptosis; D002455:Cell Division; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008545:Melanoma / Q000473:pathology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D011728:Pyridones / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000502:physiology*; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein; D019061:src-Family Kinases / Q000502:physiology*
C494811:BCL2L1 protein, human; D004268:DNA-Binding Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011728:Pyridones; D011743:Pyrimidines; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D051020:bcl-X Protein; D004247:DNA; D066246:ErbB Receptors; D019061:src-Family Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C410732:PD 180970