Plumbagin suppresses the human large cell lung cancer cell lines by inhibiting IL-6/STAT3 signaling in vitro.

BACKGROUND: Large cell lung cancer (LCLC) patients have a poor prognosis because their tumors are highly malignant and show resistance to chemotherapy and radiotherapy. Plumbagin has anticancer activity toward several tumor types, but its effects on LCLC are unknown. This study investigated the effects of plumbagin on human L9981 and NL9980 large cell lung cancer cells and the mechanisms underlying its action.

METHODS: The effects of plumbagin on L9981 and NL9980 cells proliferative activity and invasion were analyzed using MTT and Boyden chamber assays, respectively. Exogenous IL-6 was used to detect the presence of the IL-6/STAT3 signaling pathway in LCLC cell lines. L9981 cells were harvested after plumbagin treatment at 9.0μmol/L (IC50 ), while NL9980 were harvested after treatment at 7.5μmol/L for 6, 24, and 48h, and the expression of IL-6, IL-6R, gp130, and STAT3 and the downstream genes Bcl-2, VEGF, and CycD1 was assessed by RT-PCR. ELISA was performed to determine secreted IL-6 levels, and intracellular phospho-STAT3 levels were measured by western blotting.

RESULTS: After the introduction of exogenous IL-6, the mRNA expression of signaling genes and downstream genes was significantly increased in a concentration-dependent manner. Furthermore, plumbagin significantly inhibited the expression of the above mentioned genes in a dose-dependent and time-dependent manner. The mRNA expression levels of downstream genes were correlated with those of signaling genes.

CONCLUSION: Plumbagin was found to significantly inhibit the proliferation and invasion of L9981 and NL9980 cells, and may be an effective therapy for LCLC through targeting the IL-6/STAT3 signaling pathway.