Background: It is becoming increasingly recognised that opioids are responsible for tumour growth. However, the effects of opioids on tumour growth have been controversial.Methods:The effects of-opioid receptor (KOR) agonist on the growth of non-small cell lung cancer (NSCLC) cells were assessed by a cell proliferation assay. Western blotting was performed to ascertain the mechanism by which treatment with KOR agonist suppresses tumour growth. Results: Addition of the selective KOR agonist U50,488H to gefitinib-sensitive (HCC827) and gefitinib-resistant (H1975) NSCLC cells produced a concentration-dependent decrease in their growth. These effects were abolished by co-treatment with the selective KOR antagonist nor-BNI. Furthermore, the growth-inhibitory effect of gefitinib in HCC827 cells was further enhanced by co-treatment with U50,488H. With regard to the inhibition of tumour growth, the addition of U50, 488H to H1975 cells produced a concentration-dependent decrease in phosphorylated- glycogen synthase kinase 3Β (p-GSK3Β).Conclusion:The present results showed that stimulation of KOR reduces the growth of gefitinib-resistant NSCLC cells through the activation of GSK3Β.
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