Dihydroartemisinin is a Hypoxia-Active Anti-Cancer Drug in Colorectal Carcinoma Cells

Abstract

Tumor hypoxia is one main biological factor that drives resistance to chemotherapy and radiotherapy. To develop a novel strategy for overcoming hypoxia-induced therapy resistance, we examined the anti-neoplastic activity of the reactive oxygen donor dihydroartemisinin (DHA) in human colon cancer cell lines in normoxia and severe hypoxia. In addition, we analyzed the involvement of the intrinsic apoptosis pathway for DHA-mediated cytotoxicity in HCT116 cells in short-term and long-term in vitro assays. When applied at lower concentrations (≤25 μM), DHA induced apoptosis in Colo205, HCT15, and HCT116 cells, whereas necrotic cell death was increased when cells were treated with higher DHA concentrations (50 μM). However, no preference for DHA-induced apoptosis or necrosis could be detected between the treatment under normoxic or hypoxic conditions. Moreover, DHA potently reduced clonogenic survival of HCT116 cells in normoxia and hypoxia. Treatment of HCT116 cells with 25 μM DHA resulted in activation of Bax under normoxic and hypoxic conditions. Interestingly, cytochrome c release from the mitochondria and caspase-activation were observed only under normoxic conditions, whereas, under hypoxic conditions DHA induced a caspase-independent apoptosis-like cell death. However, under both conditions, generation of reactive oxygen species was an important mediator of DHA-induced toxicity. Further molecular analysis suggests that DHA-mediated cell death involves different sets of pro-apoptotic Bcl-2 family members. The pronounced cytotoxic activity of DHA in severe hypoxia as well as normoxia offers new perspectives for targeting the hypoxic tumor cell fraction to improve treatment outcome for cancer patients.

Dihydroartemisinin induces apoptosis preferentially via a Bim-mediated intrinsic pathway in hepatocarcinoma cells

“…6a-c) support the notion that Mcl-1 preferentially restricts the activation of Bak but not Bax [46,56]. It was demonstrated that overexpression of Mcl-1 in HCC cells enhanced cell resistance to apoptosis [57], and DHA-induced apoptosis was accompanied by a downregulation of Mcl-1 in leukemia cells [55] and in colon cancer cells [33]. Handrick et al proved that the rapid decline of Mcl-1 was associated with Bak activation during DHA-induced apoptosis in Jurkat cells [25].…”

“…Some publications also showed that DHAinduced Bax-mediated apoptosis was accompanied by a decline of Bcl-2 expression in HCC cells [15,26], pancreatic cancer cells [18] and ovarian cancer cells [19,54]. However, other reports demonstrated that DHA did not influence the expression of Bcl-2/Bcl-xl in leukemia cells [25,55], colon cancer cells [33] and HCC cells (Bcl-xl) [27]. These discrepancies may stem from the different pathways through which DHA induces apoptosis in distinct cancer cells that possess their own cellular systems to response to apoptotic stimuli [25].…”

“…which keep Bax/Bak in check [30]. Our previous work has proved that Bim played an important role in ARS-induced apoptosis in human lung cancer cells [31], and it was reported that DHA treatment increased the expression of Bim in breast cancer and colon cancer cells [32,33]. Puma was reported to be up-regulated in DHA-induced apoptosis in melanoma and colon cancer cells [33,34].…”

“…Our previous work has proved that Bim played an important role in ARS-induced apoptosis in human lung cancer cells [31], and it was reported that DHA treatment increased the expression of Bim in breast cancer and colon cancer cells [32,33]. Puma was reported to be up-regulated in DHA-induced apoptosis in melanoma and colon cancer cells [33,34]. In human lung cancer cells, our recent studies found that Bid was not involved in ART-induced apoptosis [35] but might be involved in DHA-induced apoptosis [13,24].…”

Dihydroartemisinin increases temozolomide efficacy in glioma cells by inducing autophagy

“…Dihydroartemisinin (DHA), the major active metabolite of artemisinin, has been found to inhibit the growth of cancer cells in a variety of cancers (12)(13)(14)(15). Xie et al (16) reported that the concentration of DHA was two-fold higher in the brain than in the plasma, which indicates that DHA is able to penetrate the brain-blood barrier.…”