Yongsheng Jia

Guaianolide Sesquiterpene Lactones, a Source To Discover Agents That Selectively Inhibit Acute Myelogenous Leukemia Stem and Progenitor Cells

Small molecules that can selectively target cancer stem cells (CSCs) remain rare currently and exhibit no common structural features. Here we report a series of guaianolide sesquiterpene lactones (GSLs) and their derivatives that can selectively eradicate acute myelogenous leukemia (AML) stem or progenitor cells. Natural GSL compounds arglabin, an anticancer clinical drug, and micheliolide (MCL), are able to reduce the proportion of AML stem cells (CD34⁺CD38⁻) in primary AML cells. Targeting of AML stem cells is further confirmed by a sharp reduction of colony-forming units of primary AML cells upon MCL treatment. Moreover, DMAMCL, the dimethylamino Michael adduct of MCL, slowly releases MCL in plasma and in vivo and demonstrates remarkable therapeutic efficacy in the nonobese diabetic/severe combined immunodeficiency AML models. These findings indicate that GSL is an ample source for chemical agents against AML stem or progenitor cells and that GSL is potentially highly useful to explore anti-CSC approaches.

Micheliolide overcomes KLF4-mediated cisplatin resistance in breast cancer cells by downregulating glutathione.

Micheliolide (MCL) is a promising novel compound with broad-spectrum anticancer activity. However, little is known regarding its action and mechanism in breast cancer. To explore the potential therapeutic application of MCL as a chemosensitivity modulator, this study investigated the effects of MCL on cisplatin sensitivity in breast cancer and the underlying mechanisms. In the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity assay and a xenograft tumor model, MCL enhanced the cisplatin sensitivity of the breast cancer cell line MCF-7 both in vitro and in vivo. Treatment of MCF-7 cells with low-dose cisplatin (10 µM) was sufficient to enrich the proportion of ALDH+ cells and upregulate Krüppel-like factor 4 (KLF4) expression. The results obtained from knockdown and overexpression experiments demonstrate that KLF4 is both necessary and sufficient to induce a cisplatin resistance phenotype in breast cancer cells. Furthermore, the glutathione (GSH) content was elevated in MCF-7 cells after overexpression of KLF4. KLF4-mediated resistance to cisplatin was found to be abrogated by treatment with buthionine sulfoximine, an inhibitor of GSH synthesis. MCL induced GSH depletion and severe cell death in KLF4-overexpressing MCF-7 cells following exposure to cisplatin. Therefore, these results suggest that MCL-mediated direct depletion of GSH represents a major mechanism in reversing KLF4-induced cisplatin resistance in MCF-7 cells.

Dynamin-related protein 1 is involved in micheliolide-induced breast cancer cell death

Dynamin-related protein 1 (Drp1) is a newly discovered therapeutic target for tumor initiation, migration, proliferation, and chemosensitivity. Thus, therapeutic strategies that focus on targeting Drp1 and its related signaling pathway pave a new way to address the ineffectiveness of traditional cancer therapies. Micheliolide (MCL), a guaianolide sesquiterpene lactone, can selectively eradicate acute myeloid leukemia stem or progenitor cells. But the effect of MCL on the mitochondrial dynamics of cancer cells is still not well demonstrated. In this study, we show that MCL inhibited the growth of MCF-7 human breast cancer cells, accompanied by increased mitochondrial fission and upregulation of Drp1. The results obtained from overexpression experiments of wild or dominant-negative mutant type of Drp1 demonstrate that Drp1 is both necessary and sufficient to induce MDA-MB-231 and MCF-7 cell death. Furthermore, mitochondrial membrane potential decreased, whereas reactive oxygen species (ROS) generation, cytochrome c release, and PARP cleavage were enhanced after overexpression of Drp1 wild type. On the other hand, overexpression of Drp1-K38A (a dominant-negative mutant of Drp1) rescued cells from increased apoptosis, confirming the role of MCL-induced Drp1 in the observed apoptosis. Finally, MCL-induced Drp1-mediated cell death could be reversed by N-acetyl-L-cysteine (the ROS scavenger) in breast cancer cells. Taken together, the present study shows a novel role for Drp1 in MCL-induced breast cancer cell death, potentially through regulation of ROS–mitochondrial apoptotic pathway.