Rational Design of a Parthenolide-based Drug Regimen That Selectively Eradicates Acute Myelogenous Leukemia Stem Cells

Abstract

Although multidrug approaches to cancer therapy are common, few strategies are based on rigorous scientific principles. Rather, drug combinations are largely dictated by empirical or clinical parameters. In the present study we developed a strategy for rational design of a regimen that selectively targets human acute myelogenous leukemia (AML) stem cells. As a starting point, we used parthenolide, an agent shown to target critical mechanisms of redox balance in primary AML cells. Next, using proteomic, genomic, and metabolomic methods, we determined that treatment with parthenolide leads to induction of compensatory mechanisms that include up-regulated NADPH production via the pentose phosphate pathway as well as activation of the Nrf2-mediated oxidative stress response pathway. Using this knowledge we identified 2-deoxyglucose and temsirolimus as agents that can be added to a parthenolide regimen as a means to inhibit such compensatory events and thereby further enhance eradication of AML cells. We demonstrate that the parthenolide, 2-deoxyglucose, temsirolimus (termed PDT) regimen is a potent means of targeting AML stem cells but has little to no effect on normal stem cells. Taken together our findings illustrate a comprehensive approach to designing combination anticancer drug regimens.Numerous studies have documented the biological complexity of human tumor cell populations in which genetic, epigenetic, biochemical, and metabolic properties can often be quite heterogeneous (1, 2). As a result, complicated multidrug regimens are often employed to target various components of tumor biology and/or acquired drug resistance (3, 4). However, the rationale behind the design of multidrug regimens is usually inconsistent and often driven by pragmatism more than scientific rigor. Thus, establishing more effective means by which to identify optimal drug regimens is an important priority, particularly with the recent emergence of a broad range of targeted agents.

Indole carboxylic acid esters of melampomagnolide B are potent anticancer agents against both hematological and solid tumor cells

“…Both sesquiterpenes exhibit significantly reduced cytotoxicity against normal bone marrow stem cells when compared to their effect on AML stem cells. [13–15] The presence of the C-14 primary allylic hydroxyl group in the MMB molecule ( 3 , Figure 1) allows the medicinal chemist the opportunity to examine the biological activity of a wide variety of new MMB derivatives via conjugation and functional group transformations. Utilizing this approach, C-14 carbamate and carbonate conjugates of MMB have recently been shown to possess improved cytotoxicity against hematological and solid tumor cell lines when compared to the parent compound,[16–18] and the dimeric MMB carbamate esters ( 4 and 5, Figure 1) have been shown to possess promising anticancer activities against a wide variety of both hematological and solid human tumor cell lines.…”

“…In addition, a C-14 biotin-conjugated derivative of MMB has been prepared and used in elucidating the mechanism of action of MMB in AML stem cells[13, 14, 15]. Utilizing this probe, and carrying out subsequent streptavidine pull-down and LC/MS/MS peptide sequencing studies, the MMB-biotin probe pulls down IKKβ in both streptavidine/antibody and LC/MS/MS proteomic assays.…”

Identification of a melampomagnolide B analog as a potential lead molecule for treatment of acute myelogenous leukemia

“…1), originally isolated from the medicinal herb feverfew ( Tanacetum parthenium ), 9 has been identified as an anticancer agent that is particularly effective against both hematological and solid tumors. 10–16 PTL is a potent antileukemic agent 17 but possesses poor drug-like properties, having low water-solubility and poor oral bioavailability, 18 precluding its use as a clinical agent for the treatment of AML. Structural modification of the PTL molecule has been carried out in attempts to improve the drug-like properties of the molecule while retaining its antileukemic properties.…”

“…Utilizing this approach, C-14 carbamate conjugates of MMB have recently been shown to possess improved cytotoxicity against hematological tumor cells and solid tumor cell lines when compared to the parent compound, 22,23 and a C-14 biotin-conjugated derivative of MMB has been prepared and used in elucidating the mechanism of action of MMB in primary human AML cells 11,16,21 .…”

“…Both PTL and MMB may perturb glutathione homeostasis by a multifactorial mechanism. 11,16 Streptavidin pull-down and amino acid sequencing studies with the C-14 biotin conjugate of MMB identified key proteins involved in glutathione biosynthesis and catabolism pathways. 11 MMB appears to target the glutathione-cysteine ligase enzyme, which is the rate-limiting step in the glutathione biosynthetic pathway, as well as glutathione peroxidase (GPX1).…”