Down-regulation of the nuclear factor-κB by lidamycin in association with inducing apoptosis in human pancreatic cancer cells and inhibiting xenograft growth

Abstract

Pancreatic cancer is now one of the most common causes of cancer death worldwide. K-ras mutations are present in up to 90% of pancreatic cancer cases. The expression of mutant K-ras activates the Akt/protein kinase B pathway, resulting in the activation of the nuclear factor-κB (NF-κB) transcriptional factor. Constitutive NF-κB activity plays a key role in pancreatic carcinoma. NF-κB has been shown to inhibit apoptosis in response to chemotherapeutic agents. In the present study, the effects of lidamycin (LDM), a member of the enediyne antibiotic family, were investigated on two established pancreatic cell lines, PANC-1 and SW1990. A dose-dependent inhibition of phospho-Akt and NF-κB activation was found in the cells treated with LDM as determined by Western blot analysis. Moreover, a down-regulation of K-ras mRNA and a protein expression by LDM were observed in both cell lines as determined by reverse transcription-PCR and Western blot analysis. By MTT assay, a remarkable difference in chemosensitivity to LDM, mitomycin, adriamycin, taxol, and gemcitabine was found in both cell lines. The IC50 values of LDM for the PANC-1 or SW1990 cells were 0.955±0.414 or 0.426±0.212 nM, respectively, lower than those of the other drugs. Growth inhibition, apoptosis induction and cell cycle arrest were observed in the LDM-treated cells. LDM decreased the invasive potential of pancreatic cancer cells by reducing matrix metalloproteinase-9 activity. Furthermore, LDM was found to suppress the growth of SW1990 xenografts in nude mice. Treatment with an i.v. injection of LDM at the dose of 0.02 and 0.04 mg/kg (once a week for two weeks) inhibited the growth of xenografts by 66 and 72%, respectively. By contrast, an i.p. injection of gemcitabine at the dose of 80 mg/kg inhibited the growth of xenografts by 38%. Our findings suggest that LDM is active in the down-regulation of NF-κB and could play a positive role in relevant targeted chemotherapy for pancreatic carcinoma.