Novel Endoperoxides Increase Apoptosis in Cancer, but not Normal Cells, and May Involve Differences in Transferrin Receptor (TfR) Expression

Abstract

Artemisinin (ART), a common anti‐malarial drug, and its analogs are also useful as repurposed anti‐cancer drugs, but their properties are not fully elucidated. We previously synthesized novel trioxane (DMR) and dioxazanine (HSM) ART analogs and showed that: a. at low doses (5–10 μM), HSM > than DMR in inducing apoptosis in human colon and lung cancer cells, but not in normal lung cells; b. The actions involved reactive oxygen species (ROS) (Faseb J, ′18:32, 616.2). TfR expression is increased in cancer vs. normal cells. Thus, we hypothesize that, in cancer cells, TfR increases [Fe2+]i which acts on the endoperoxide to produce ROS and induce apoptosis. We examined the mechanism of action of DMR/HSM in inducing apoptosis in human breast, lung, and colon cancer cell lines as compared to normal cell lines. To increase the efficacy of the drug, we also designed and synthesized a 3rd novel analog with dual dioxazanine pharmacophores, PMW.Confluent normal (Breast: MCF10A, Lung: A549) and cancer (Breast: MCF7, Colon: T84, Lung: A549) cells were treated (18 H) with 1–50μM of DMR, HSM or PMW±Deferoxamine (DFO, iron chelator; 1–25 μM). Cells were stained with FITC‐Annexin V (apoptosis), propidium iodide (cell death) or CellRox Green (mitochondrial/nuclear ROS), imaged and quantified by flow cytometry and/or microscopy (Image J). Normal and cancer cell lysates (30 μg) were subjected to SDS‐PAGE and immunoblotting with polyclonal TfR antibody or anti‐GAPDH (control).As in other cancer cells, both DMR and HSM (5 – 50μM) induced apoptosis in breast cancer, but not normal, cells. In contrast to A549 lung cells, where HSM was more effective than DMR, in MCF7 breast cells, 50μM DMR was more efficient (~40%) in inducing apoptosis than HSM (10%). This dictates the development of novel tissue‐specific analogs. The new analog, PMW (1 – 50μM, 18H) did not induce apoptosis in the cancer cells. The larger size of PMW may have slowed entry, suggesting longer incubations.Image J analysis (mean pixel intensity; 18 H) of CellRox+ lung cells (n=3) showed that HSM dose‐dependently increased ROS in cancer A549: (DMSO: 1.5±0.2; HSM, 5 μM: 19±2; 10 μM: 48±4; 50 μM: 59±2); but not normal BEAS2B: (DMSO: 1.0±0.3; HSM, 5 μM: 1.8±1; 10 μM: 2.2±0.4; 50 μM: 2.9±2). Similarly, in breast cancer cells (n=3), DMR dose‐dependently increased ROS in MCF7 (DMSO: 1.0±0.3; DMR, 5 μM: 12±2; 10 μM: 51±5; 50 μM: 42±3); but not in MCF10A (DMSO: 1.0±0.2; DMR, 5 μM: 1.6±1; 10 μM: 3.1±1; 50 μM: 2.5±1).Immunoblotting detected a distinct 94 kDa TfR protein in colon, lung, and breast cancer, but not normal cells. The effect of DMR/HSM±DFO on apoptosis was examined to study the role of TfR. Albeit showing an inhibitory trend, DFO did not significantly alter ART analogs actions (% Annexin V+ cells,18 H: A549: HSM,10μM: 46±4; HSM+5μM DFO: 38±6; HSM +10μM DFO: 33±9; MCF7: DMR,10μM: 36±4; DMR+5μM DFO: 31±7; DMR+10μM DFO: 29±5; n≥3).Synthesizing novel ART‐analogs with improved pharmacokinetics to specifically target cancer cells and elucidating their mechanism of action will help develop new alternatives to treat cancer.Support or Funding InformationNSF ‐ MRI: DBI‐1427937 to JS; Ben U Funds to JS and DMR; UIC Funds to MCR; APS‐STRIDE to UD; APS‐UGSRF to MHThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.