Abstract
Acquired chemoresistance not only blunts anticancer therapy but may also promote cancer cell migration and metastasis. Our previous studies have revealed that acquired tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resistance in lung cancer cells is associated with Akt-mediated stabilization of cellular caspase 8 and Fas-associated death domain (FADD)-like apoptosis regulator-like inhibitory protein (c-FLIP) and myeloid cell leukemia 1 (Mcl-1). In this report, we show that cells with acquired TRAIL resistance have significantly increased capacities in migration and invasion. By gene expression screening, tissue transglutaminase (TGM2) was identified as one of the genes with the highest expression increase in TRAIL-resistant cells. Suppressing TGM2 dramatically alleviated TRAIL resistance and cell migration, suggesting that TGM2 contributes to these two phenotypes in TRAIL-resistant cells. TGM2-mediated TRAIL resistance is likely through c-FLIP because TGM2 suppression significantly reduced c-FLIP but not Mcl-1 expression. The expression of matrix metalloproteinase 9 (MMP-9) was suppressed when TGM2 was inhibited, suggesting that TGM2 potentiates cell migration through up-regulating MMP-9 expression. We found that EGF receptor (EGFR) was highly active in the TRAIL-resistant cells, and suppression of EGFR dramatically reduced TGM2 expression. We further determined JNK and ERK, but not Akt and NF-κB, are responsible for EGFR-mediated TGM2 expression. These results identify a novel pathway that involves EGFR, MAPK (JNK and ERK), and TGM2 for acquired TRAIL resistance and cell migration in lung cancer cells. Because TGM2 couples TRAIL resistance and cell migration, it could be a molecular target for circumventing acquired chemoresistance and metastasis in lung cancer.
Highlights
Due to its selective cytotoxicity in transformed cells, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as the most promising anticancer agent in the TNF superfamily of cytokines [11]
The results reveal a novel pathway consisting of EGF receptor (EGFR), MAPK (JNK and ERK), and TGM2 that promotes TRAIL resistance through c-FLIP and migration/invasion through matrix metalloproteinase 9 (MMP-9), and suggest TGM2 as a molecular target for circumventing acquired chemoresistance and metastasis because this protein couples TRAIL resistance and cell migration in lung cancer
We determined that a novel pathway consisting of EGFR, MAPK (JNK and ERK), and TGM2 is responsible for acquired TRAIL resistance-associated migration and invasion in lung cancer cells
Summary
Due to its selective cytotoxicity in transformed cells, TRAIL is regarded as the most promising anticancer agent in the TNF superfamily of cytokines [11]. We have recently established acquired TRAIL resistance in lung cancer cell lines by continuously exposing the TRAIL-sensitive lung cancer cells to nontoxic doses and gradually increasing the concentrations of TRAIL [19, 20]. With these cells, we have demonstrated that the acquired TRAIL resistance was associated with Akt-mediated stabilization of c-FLIP and Mcl-1 and overexpression of cyclooxygenase 2 (COX-2) [19, 20]. The results reveal a novel pathway consisting of EGFR, MAPK (JNK and ERK), and TGM2 that promotes TRAIL resistance through c-FLIP and migration/invasion through MMP-9, and suggest TGM2 as a molecular target for circumventing acquired chemoresistance and metastasis because this protein couples TRAIL resistance and cell migration in lung cancer
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