Original Article

Chloroquine potentiates the anti-cancer effect of lidamycin on non-small cell lung cancer cells in vitro

Authors: Fang Liu, Yue Shang, Shu-zhen Chen
DOI: 10.1038/aps.2014.3

Abstract

Fang LIU, Yue SHANG, Shu-zhen CHEN*
Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China

Aim: To assess the synergistic actions of lidamycin (LDM) and chloroquine (CQ), a lysosomal enzyme inhibitor, in human non-small cell lung cancer (NSCLC) cells, and to elucidate the potential mechanisms.
Methods: Both LDM and CQ concentration-dependently suppressed the proliferation of A549 and H460 cells in vitro (the IC50 values of LDM were 1.70±0.75 and 0.043±0.026 nmol/L, respectively, while the IC50 values of CQ were 71.3±6.1 and 55.6±12.5 μmol/L, respectively). CQ sensitized both NSCLC cell lines to LDM, and the majority of the coefficients of drug interaction (CDIs) for combination-doses were less than 1. The ratio of apoptosis of H460 cells induced by a combined treatment of CQ and LDM (77.0%±5.2%) was significantly higher than those caused by CQ (23.1%±4.2%) or by LDM (65.1%±4.1%) alone. Furthermore, the combined treatment markedly increased the cleaved PARP and cleaved caspase 3 in H460 cells, which were partly reversed by pretreatment with the caspase inhibitor zVAD.fmk. zVAD.fmk also partially reversed the inhibitory effect of the combination treatment on the proliferation of H460 cells. The combination therapy group had a notable increase in expression of Bax and a very slight decrease in expression of Bcl-2 and p53 protein. LDM alone scarcely affected the level of LC3-II in H460 cells, but slightly reduced CQ-induced LC3-II expression. 3-MA, an autophagy inhibitor also sensitized H460 cells to LDM. In nude mice bearing H460 cell xenograft, administration of LDM (25 μg/kg, iv) and CQ (60 mg/kg, ip) suppressed tumor growth by 57.14% and 73.02%, respectively.

Results: The four GSTP1 haplotype-tagging SNPs rs1695, rs4891, rs762803 and rs749174, but not the MPO tagSNP rs7208693, exhibited an association with lung cancer susceptibility in smokers in the overall population and in the studied subgroups. When Phase 2 software was used to reconstruct the haplotype for GSTP1, the haplotype CACA (rs749174+rs1695 + rs762803+rs4891) exhibited an increased risk of lung cancer among smokers (adjust odds ratio 1.53; 95%CI 1.04–2.25, P=0.033). Furthermore, diplotype analyses demonstrated that the significant association between the risk haplotype and lung cancer. The risk haplotypes co-segregated with one or more biologically functional polymorphisms and corresponded to a recessive inheritance model.

Conclusion: The synergistic anticancer effect of LDM and CQ in vitro results from activation of a caspase-dependent and p53-independent apoptosis pathway as well as inhibition of cytoprotective autophagy.


Keywords: lung cancer; anticancer drug; lidamycin; chloroquine; drug interaction; synergism; apoptosis; autophagy

This investigation received support from the National Natural Science foundation of China (No 81072664 and 81373437) and the National Science and Technology Major Project of China (Grant No 2012ZX09301002-001-022-01).
* To whom correspondence should be addressed.
E-mail bjcsz@imb.pumc.edu.cn
Received 2013-10-08 Accepted 2014-01-16
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