Replication-dependent γ-H2AX formation is involved in docetaxel-induced apoptosis in NSCLC A549 cells.

Department of Pharmacology, School of Pharmacy, The Fourth Military Medical University, Xi'an 710032, PR China.
Oncology Reports (Impact Factor: 2.3). 11/2010; 24(5):1297-305.
Source: PubMed


Docetaxel is a member of the taxane anti-microtubule class of chemotherapeutic agents, which are currently widely used in clinical cancer therapy. However, the anti-tumor mechanisms of docetaxel are not fully understood. Herein we show that docetaxel induces dose-dependent apoptosis in non-small cell lung cancer A549 cells, as detected by Annexin-V positive cells and PARP cleavage, which is via mitochondrial pathway and dependent on caspase-3 activation. Our study on the mechanisms confirms that docetaxel induces dose-dependent accumulation of cells in M phase and acetylation of α-tubulin, marker of tubulin stablization. Furthermore, docetaxel induces replication-dependent γ-H2AX formation which plays a crucial role in docetaxel-triggered apoptosis. The DNA polymerase inhibitor aphidicolin dose-dependently prevents docetaxel-induced γ-H2AX formation, as well as apoptosis. Notably, 0.6 µM APC almost completely blocked docetaxel-induced γ-H2AX formation and apoptosis. In addition, wortmannin pretreatment caused elevated γ-H2AX level, which was accompanied with increased apoptosis. This effect was due to the inhibition of DNA repair process by wortmannin, as down regulation of p21Waf1/Cip1 and DNA repair proteins such as Ku70, Ku80, DNA-PKcs and Rad50, were detected. These data show, for the first time, that the induction of apoptosis by docetaxel requires DNA replication, and replication-mediated DSBs are critical triggers of docetaxel-induced apoptosis.

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    • "In general, the tumor suppression mechanisms of current chemotherapeutic drugs are mainly based on disruption of cell cycle processes, resulting in cell apoptosis. For example, well-studied chemotherapeutic drugs such as the alkylating agents, cisplatin, and carboplatin inhibit DNA synthesis in tumor cell growth by forming DNA adducts [8] [9], whereas plant alkaloids, such as the taxanes, block tumor cell mitosis by stabilizing tubulin [10] [11]. Other common drugs such as doxorubicin function as topoisomerase II inhibitors and interfere with DNA/RNA synthesis in tumor cells [12] [13]. "
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    ABSTRACT: Colorectal cancer is a common cancer worldwide, and chemotherapy is a mainstream approach for advanced and recurrent cases. Development of effective complementary drugs could help improve tumor suppression efficiency and control adverse effects from chemotherapy. The aqueous extract of Solanum nigrum leaves (AE-SN) is an essential component in many traditional Chinese medicine formulas for treating cancer, but there is a lack of evidence verifying its tumor suppression efficacy in colorectal cancer. The purpose of this study is to evaluate the tumor suppression efficacy of AE-SN using DLD-1 and HT-29 human colorectal carcinoma cells and examine the combined drug effect when combined with the chemotherapeutic drugs cisplatin, doxorubicin, docetaxel, and 5-fluorouracil. The results indicated that AE-SN induced autophagy via microtubule-associated protein 1 light chain 3 A/B II accumulation but not caspase-3-dependent apoptosis in both cell lines. The IC50s after 48 hours of treatment were 0.541 and 0.948 mg/ml AE-SN in DLD-1 and HT-29, respectively. AE-SN also demonstrated a combined drug effect with all tested drugs by enhancing cytotoxicity in tumor cells. Our results suggest that AE-SN has potential in the development of complementary chemotherapy for colorectal cancer.
    Evidence-based Complementary and Alternative Medicine 06/2013; 2013(3):514719. DOI:10.1155/2013/514719 · 1.88 Impact Factor
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    • "Since AE-SN activates apoptotic and autophagic cell death in cancer cells, it may achieve a synergistic or additive effect with chemotherapeutic regimens which induce cancer cell death in other pathways. For example, the anti-tumor efficacy of docetaxel, which is mainly achieved by stabilizing microtubules followed by cell cycle arrest and caspase-associated cell apoptosis [20, 21], may be further enhanced by cotreatment with AE-SN. The aim of the present study therefore is first to examine the antitumor effects of AE-SN in human endometrial cancer cells and also clarify whether AE-SN is capable of further enhancing the antitumor effects of docetaxel in human endometrial cancer cells or not. "
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    ABSTRACT: Chemotherapy is the main approach in dealing with advanced and recurrent endometrial cancer. An effective complementary ingredient can be helpful in improving the clinical outcome. Aqueous extract of Solanum nigrum leaf (AE-SN) is a principal ingredient for treating cancer patients in traditional Chinese medicinal practice but lacks sufficient evidence to verify its tumor suppression efficacy. This study evaluated the antitumor effects of AE-SN and also assessed the synergistic effects of AE-SN with docetaxel On the human endometrial cancer cell lines, HEC1A, HEC1B, and KLE. The activation of apoptotic markers, caspase-3 and poly-ADP-ribose polymerase, and autophagic marker, microtubule-associated protein 1 light chain 3 A/B, wAS determined to clarify the cell death pathways responsible for AE-SN induced tumor cell death. Results indicated that AE-SN-treatment has significant cytotoxicity on the tested endometrial cancer cells with accumulation of LC3 A/B II and demonstrated a synergistic effect of AE-SN and docetaxel in HEC1A and HEC1B cells, but not KLE cells. In conclusion, AE-SN treatment was effective in suppressing endometrial cancer cells via the autophagic pathway and was also capable of enhancing the cytotoxicity of docetaxel in human endometrial cancer cells. Our results provide meaningful evidence for integrative cancer therapy in the future.
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