NADPH oxidase promotes pancreatic cancer cell survival via inhibiting JAK2 dephosphorylation by tyrosine phosphatases.
OBJECTIVE
Growth factors, such as insulin-like growth factor-1 (IGF-I), protect pancreatic cancer (PaCa) cells from death. We recently showed that reactive oxygen species (ROS) produced by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase Nox4 mediate the antiapoptotic effect of growth factors. Here, we examine the mechanisms of the antiapoptotic role of NADPH oxidase. We hypothesized that ROSs produced by NADPH oxidase inhibit key protein tyrosine phosphatases (PTPs) and thus sustain the activation of kinases mediating antiapoptotic pathways in PaCa cells.


METHODS
Transfections and pharmacologic inhibition were used to assess the effects of NADPH oxidase on Janus kinase 2 (JAK2) kinase, the low molecular weight-protein tyrosine phosphatase (LMW-PTP), and apoptosis.


RESULTS
We found that 1 target of ROSs is JAK2, an important antiapoptotic kinase in PaCa cells. Both serum-induced and IGF-I biphasic JAK2 phosphorylation, with a rapid (minutes) and transient first phase, and a slow and sustained (24-72 hours) second phase. Nox4 mediated the sustained phase of JAK2 phosphorylation, which was required for the antiapoptotic effects of IGF-I and serum. Transfection experiments identified the LMW-PTP as a negative regulator of sustained JAK2 phosphorylation. Growth factors inhibited LMW-PTP through its oxidation by NADPH oxidase. LMW-PTP colocalizes with Nox4 both in PaCa cells and in human pancreatic adenocarcinoma.


CONCLUSIONS
The results suggest a novel signaling pathway, in which NADPH oxidase activation results in inhibition of PTPs, such as LMW-PTP, leading, in turn, to enhanced and sustained phosphorylation of kinases, such as JAK2, and suppression of apoptosis. This pathway mediates the prosurvival effect of ROSs and suggests new targets for pancreatic cancer treatment.
Lee
Jong Kyun
JK
Veterans Affairs Greater Los Angeles Healthcare System and University of California at Los Angeles, Los Angeles, CA, USA.
Edderkaoui
Mouad
M
Truong
Patrick
P
Ohno
Izumi
I
Jang
Kee-Taek
KT
Berti
Andrea
A
Pandol
Stephen J
SJ
Gukovskaya
Anna S
AS
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001798:Blood Proteins / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D053614:Janus Kinase 2 / Q000378:metabolism*; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection
D001798:Blood Proteins; D036341:Intercellular Signaling Peptides and Proteins; D017382:Reactive Oxygen Species; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D007334:Insulin-Like Growth Factor I; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D017027:Protein Tyrosine Phosphatases