Signal transducer and activator of transcription 3 activation up-regulates interleukin-6 autocrine production: a biochemical and genetic study of established cancer cell lines and clinical isolated human cancer cells.
BACKGROUND
Spontaneous interleukin-6 (IL-6) production has been observed in various tumors and implicated in the pathogenesis, progression and drug resistance in cancer. However, the regulation of IL-6 autocrine production in cancer cells is not fully understood. IL-6 is auto-regulated in many types of cell. Two of the three major downstream pathways of IL-6, MEK/extracellular signal-related kinase (Erk) pathway and phosphatidylinositol 3-kinase (PI3-K)/Akt pathway, have been shown to regulate IL-6 expression through the activation of AP-1 and NF-κB. However, it is not clear what the role of Janus kinase (Jak) 2/signal transducer and activator of transcription (Stat) 3 pathway. This study was designed to determine the role of Jak2/Stat3 pathway in the regulation of IL-6 autocrine production in cancer cells.


RESULTS
Inhibitors of Jak2/Stat3, MEK/Erk and PI3-K/Akt pathways down-regulated IL-6 secretion in the lung adenocarcinoma PC14PE6/AS2 (AS2) cells, which spontaneously secreted IL-6 and possessed constitutively activated Stat3. Transfection with dominant-negative Stat3, Stat3 siRNA, or Stat3 shRNA decreased IL-6 expression in AS2 cells. Conversely, transfection with constitutively-activated Stat3 increased the production of IL-6. In AS2 derived cells, resistance to paclitaxel was positively correlated with Stat3 activation status and the expression of IL-6, which is commonly secreted in drug resistant cancer cells. The pharmacological inhibition of NF-κB, PI3-K/Akt and MEK/Erk and the pharmacological inhibition and genetic inhibition (Stat3 siRNA) of Jak2/Stat3 pathway decreased IL-6 autocrine production in various drug resistant cancer cell lines and similarly decreased IL-6 autocrine production in clinically isolated lung cancer cells.


CONCLUSIONS
This study is the first to directly address the role Stat3 plays on the autocrine production of IL-6, which occurs through a positive-feedback loop. Our biochemical and genetic studies clearly demonstrated that Jak2/Stat3, in combination with other IL-6 downstream pathways, contributed frequently and substantially to IL-6 autocrine production in a broad spectrum of cancer cell lines as well as in clinical cancer samples. Our findings suggest that Stat3 could potentially be regulated to suppress IL-6 autocrine production in cancer cells to inhibit the progression of cancer and reduce drug resistance.
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 704, Taiwan.
Wei-Lun
WL
Huang
Hsuan-Heng
HH
Yeh
Chien-Chung
CC
Lin
Wu-Wei
WW
Lai
Jang-Yang
JY
Chang
Wen-Tsan
WT
Chang
Wu-Chou
WC
Su
D000230:Adenocarcinoma / Q000378:metabolism; D000077192:Adenocarcinoma of Lung; D015153:Blotting, Western; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000235:genetics; D014407:Tumor Cells, Cultured
D015850:Interleukin-6; D050796:STAT3 Transcription Factor; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D017239:Paclitaxel