Cellular Uptake of the Antitumor Agent Dp44mT Occurs via a Carrier/Receptor-Mediated Mechanism

Merlot, Angelica M.; Pantarat, Namfon; Menezes, Sharleen V.; Sahni, Sumit; Richardson, Des R.; Kalinowski, Danuta S.

doi:10.1124/mol.113.088393

Cited by 20 publications

(30 citation statements)

References 56 publications

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“…These conditions have been previously demonstrated to efficiently induce iron depletion and increase the expression of iron-regulated molecules (Richardson et al, 1994;Yuan et al, 2004;Kovacevic et al, 2011). Furthermore, we have shown that Dp44mT uptake by cells saturates at 5-10 mM (Merlot et al, 2013b). At this concentration, the level of agent is pharmacologically relevant in humans, as the structurally related thiosemicarbazone Triapine has been observed in the serum at similar levels (Wadler et al, 2004;Chao et al, 2012).…”

Section: Resultsmentioning

confidence: 61%

Novel Thiosemicarbazones Regulate the Signal Transducer and Activator of Transcription 3 (STAT3) Pathway: Inhibition of Constitutive and Interleukin 6–Induced Activation by Iron Depletion

et al. 2015

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Pharmacologic manipulation of metal pools in tumor cells is a promising strategy for cancer treatment. Here, we reveal how the iron-binding ligands desferrioxamine (DFO), di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) inhibit constitutive and interleukin 6-induced activation of signal transducer and activator of transcription 3 (STAT3) signaling, which promotes proliferation, survival, and metastasis of cancer cells. We demonstrate that DFO, Dp44mT, and DpC significantly decrease constitutive phosphorylation of the STAT3 transcription factor at Tyr705 in the pancreatic cancer cell lines PANC-1 and MIAPaCa-2 as well as the prostate cancer cell line DU145. These compounds also significantly decrease the dimerized STAT3 levels, the binding of nuclear STAT3 to its target DNA, and the expression of downstream targets of STAT3, including cyclin D1, c-myc, and Bcl-2. Examination of upstream mediators of STAT3 in response to these ligands has revealed that Dp44mT and DpC could significantly decrease activation of the nonreceptor tyrosine kinase Src and activation of cAbl in DU145 and MIAPaCa-2 cells. In contrast to the effects of Dp44mT, DpC, or DFO on inhibiting STAT3 activation, the negative control compound di-2-pyridylketone 2-methyl-3-thiosemicarbazone, or the DFO:Fe complex, which cannot bind cellular iron, had no effect. This demonstrates the role of iron-binding in the activity observed. Immunohistochemical staining of PANC-1 tumor xenografts showed a marked decrease in STAT3 in the tumors of mice treated with Dp44mT or DpC compared with the vehicle. Collectively, these studies demonstrate suppression of STAT3 activity by iron depletion in vitro and in vivo, and reveal insights into regulation of the critical oncogenic STAT3 pathway.

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Section: Resultsmentioning

confidence: 61%

Novel Thiosemicarbazones Regulate the Signal Transducer and Activator of Transcription 3 (STAT3) Pathway: Inhibition of Constitutive and Interleukin 6–Induced Activation by Iron Depletion

et al. 2015

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“…However, studies have also demonstrated mechanisms by which albumin acts to effectively improve therapeutic use or reduce rapid clearance (Dennis et al, 2002; Merlot and Richardson, 2014). For instance, the experimental anti-cancer thiosemicarbazone, namely di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) (Merlot et al, 2013a), has been shown to be internalized by cancer cells via a putative carrier/receptor (Merlot et al, 2013b; Merlot and Richardson, 2014). Interestingly, the uptake, toxicity and apoptotic activity of Dp44mT is greatly enhanced in the presence of HSA (Merlot and Richardson, 2014).…”

Section: Albumin As a Drug Carrier In Oncologymentioning

confidence: 99%

Unraveling the mysteries of serum albuminâ€”more than just a serum protein

2014

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Serum albumin is a multi-functional protein that is able to bind and transport numerous endogenous and exogenous compounds. The development of albumin drug carriers is gaining increasing importance in the targeted delivery of cancer therapy, particularly as a result of the market approval of the paclitaxel-loaded albumin nanoparticle, Abraxane®. Considering this, there is renewed interest in isolating and characterizing albumin-binding proteins or receptors on the plasma membrane that are responsible for albumin uptake. Initially, the cellular uptake and intracellular localization of albumin was unknown due to the large confinement of the protein within the vascular and interstitial compartment of the body. Studies have since assessed the intracellular localization of albumin in order to understand the mechanisms and pathways responsible for its uptake, distribution and catabolism in multiple tissues, and this is reviewed herein.

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“…Interestingly, it has been recently demonstrated that Dp44mT binds to a saturable receptor/carrier on a variety of cell-types [ 34 ]. Other structurally-related thiosemicarbazones, such as 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT; Fig.…”

Section: Introductionmentioning

confidence: 99%

Potentiating the cellular targeting and anti-tumor activity of Dp44mTviabinding to human serum albumin: two saturable mechanisms of Dp44mT uptake by cells

et al. 2015

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Di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) demonstrates potent anti-cancer activity. We previously demonstrated that 14C-Dp44mT enters and targets cells through a carrier/receptor-mediated uptake process. Despite structural similarity, 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT) and pyridoxal isonicotinoyl hydrazone (PIH) enter cells via passive diffusion. Considering albumin alters the uptake of many drugs, we examined the effect of human serum albumin (HSA) on the cellular uptake of Dp44mT, Bp4eT and PIH. Chelator-HSA binding studies demonstrated the following order of relative affinity: Bp4eT≈PIH>Dp44mT. Interestingly, HSA decreased Bp4eT and PIH uptake, potentially due to its high affinity for the ligands. In contrast, HSA markedly stimulated Dp44mT uptake by cells, with two saturable uptake mechanisms identified. The first mechanism saturated at 5-10 μM (Bmax:1.20±0.04 × 107 molecules/cell; Kd:33±3 μM) and was consistent with a previously identified Dp44mT receptor/carrier. The second mechanism was of lower affinity, but higher capacity (Bmax:2.90±0.12 × 107 molecules/cell; Kd:65±6 μM), becoming saturated at 100 μM and was only evident in the presence of HSA. This second saturable Dp44mT uptake process was inhibited by excess HSA and had characteristics suggesting it was mediated by a specific binding site. Significantly, the HSA-mediated increase in the targeting of Dp44mT to cancer cells potentiated apoptosis and could be important for enhancing efficacy.

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Cellular Uptake of the Antitumor Agent Dp44mT Occurs via a Carrier/Receptor-Mediated Mechanism

Abstract: The chelator di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone

Cited by 20 publications

References 56 publications

Novel Thiosemicarbazones Regulate the Signal Transducer and Activator of Transcription 3 (STAT3) Pathway: Inhibition of Constitutive and Interleukin 6–Induced Activation by Iron Depletion

Novel Thiosemicarbazones Regulate the Signal Transducer and Activator of Transcription 3 (STAT3) Pathway: Inhibition of Constitutive and Interleukin 6–Induced Activation by Iron Depletion

Unraveling the mysteries of serum albuminâ€”more than just a serum protein

Potentiating the cellular targeting and anti-tumor activity of Dp44mTviabinding to human serum albumin: two saturable mechanisms of Dp44mT uptake by cells

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