Cytotoxicity of the matrix metalloproteinase–activated anthrax lethal toxin is dependent on gelatinase expression and B-RAF status in human melanoma cells

Alfano, Randall W.; Leppla, Stephen H.; Liu, Shihui; Bugge, Thomas H.; Herlyn, Meenhard; Smalley, Keiran S.M.; Bromberg-White, Jennifer L.; Duesbery, Nicholas S.; Frankel, Arthur E.

doi:10.1158/1535-7163.mct-08-0024

Cited by 16 publications

(20 citation statements)

References 28 publications

(43 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This modifed PA, designated PA-L1, is dependent upon proteolytic activation by cell surface bound MMP-2/-9. This MMP-activated LeTx is currently under development for cancer therapy (19, 20). …”

Section: Introductionmentioning

confidence: 99%

Inhibition of Tumor Angiogenesis by the Matrix Metalloproteinase–Activated Anthrax Lethal Toxin in an Orthotopic Model of Anaplastic Thyroid Carcinoma

Alfano

Leppla

Liu

et al. 2010

Molecular Cancer Therapeutics

Self Cite

View full text Add to dashboard Cite

Patients with anaplastic thyroid carcinoma (ATC) typically succumb to their disease months after diagnosis despite aggressive therapy. A large percentage of ATCs have been shown to harbor the V600E B-Raf point mutation, leading to the constitutive activation of the mitogen-activated protein kinase pathway. ATC invasion, metastasis, and angiogenesis are in part dependent on the gelatinase class of matrix metalloproteinases (MMP). The explicit targeting of these two tumor markers may provide a novel therapeutic strategy for the treatment of ATC. The MMP-activated anthrax lethal toxin (LeTx), a novel recombinant protein toxin combination, shows potent mitogen-activated protein kinase pathway inhibition in gelatinase-expressing V600E B-Raf tumor cells in vitro. However, preliminary in vivo studies showed that the MMP-activated LeTx also exhibited dramatic antitumor activity against xenografts that did not show significant antiproliferative responses to the LeTx in vitro. Here, we show that the MMP-activated LeTx inhibits orthotopic ATC xenograft progression in both toxin-sensitive and toxin-resistant ATC cells via reduced endothelial cell recruitment and subsequent tumor vascularization. This in turn translates to an improved long-term survival that is comparable with that produced by the multikinase inhibitor sorafenib. Our results also indicate that therapy with the MMP-activated LeTx is extremely effective against advanced tumors with well-established vascular networks. Taken together, these results suggest that the MMP-activated LeTx-mediated endothelial cell targeting is the primary in vivo antitumor mechanism of this novel toxin. Therefore, the MMP-activated LeTx could be used not only in the clinical management of V600E B-Raf ATC but potentially in any solid tumor. Mol Cancer Ther; 9(1); 190-201. ©2010 AACR.

show abstract

Section: Introductionmentioning

confidence: 99%

Inhibition of Tumor Angiogenesis by the Matrix Metalloproteinase–Activated Anthrax Lethal Toxin in an Orthotopic Model of Anaplastic Thyroid Carcinoma

Alfano

Leppla

Liu

et al. 2010

Molecular Cancer Therapeutics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Anthrax toxin consists of three nontoxic proteins that co-assemble to produce a series of free or cell-bound toxic complexes (1). Two of the proteins, Lethal Factor (LF) 3 and Edema Factor (EF), are enzymes that modify cytosolic targets (2,3). The third, Protective Antigen (PA), is a receptor-binding and pore-forming protein that transports LF and EF to the cytosol (4).…”

mentioning

confidence: 99%

Effects of Introducing a Single Charged Residue into the Phenylalanine Clamp of Multimeric Anthrax Protective Antigen

Janowiak¹,

Fischer²,

Collier

2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

Multimeric pores formed in the endosomal membrane by the Protective Antigen moiety of anthrax toxin translocate the enzymatic moieties of the toxin to the cytosolic compartment of mammalian cells. There is evidence that the side chains of the Phe 427 residues come into close proximity with one another in the lumen of the pore and form a structure, termed the Phe clamp, that catalyzes the translocation process. In this report we describe the effects of replacing Phe 427 in a single subunit of the predominantly heptameric pore with a basic or an acidic amino acid. Incorporating any charged residue at this position inhibited cytotoxicity >1,000-fold in our standard assay and caused strong inhibition of translocation in a planar phospholipid bilayer system. His and Glu were the most strongly inhibitory residues, ablating both cytotoxicity and translocation. Basic residues at position 427 prevented the Phe clamp from interacting with a translocation substrate to form a seal against the passage of ions and accelerated dissociation of the substrate from the pore. Acidic residues, in contrast, allowed the seal to form and the substrate to remain firmly bound, but blocked its passage, perhaps via electrostatic interactions with the positively charged N-terminal segment. Our findings are discussed in relation to the role of the Phe clamp in a Brownian ratchet model of translocation.

show abstract

“…Previous tests of the matrix metalloprotease-activated PA (PA-L1) in combination with LF found that Colo205 was sensitive to the toxin with an EC50 of 10 ng/mL, which is 10-fold higher than the EC50 of the PA-U2/LF tested here. It was previously noted that BRAF mutational status was predictive of an in vitro response to lethal toxin treatment [48,39]. This is presumably because cells harboring the B-RAF V600E mutation depend on ERK activation for survival and growth, whereas other cell types are able to survive in the presence of ERK inhibition.…”

Section: Discussionmentioning

confidence: 99%

Tumor therapy with a urokinase plasminogen activator-activated anthrax lethal toxin alone and in combination with paclitaxel

et al. 2012

Self Cite

View full text Add to dashboard Cite

PA-U2, an engineered anthrax protective antigen that is activated by urokinase was combined with wild-type lethal factor in the treatment of Colo205 colon adenocarcinoma in vitro and B16-BL6 mouse melanoma in vitro and in vivo. This therapy was also tested in combination with the small molecule paclitaxel, based on prior reports suggesting synergy between ERK1/2 inhibition and chemotherapeutics. Colo205 was sensitive to PA-U2/LF while B16-BL6 was not. For the combination treatment of B16-BL6, paclitaxel showed a dose response in vitro, but cells remained resistant to PA-U2/LF even in the presence of paclitaxel. In vivo, each therapy slowed tumor progression, and an additive effect between the two was observed. Since LF targets tumor vasculature while paclitaxel is an anti-mitotic, it is possible the agents were acting against different cells in the stroma, precluding a synergistic effect. The engineered anthrax toxin PA-U2/ LF warrants further development and testing, possibly in combination with an anti-angiogenesis therapy such as sunitinib or sorafinib.

show abstract

Cytotoxicity of the matrix metalloproteinase–activated anthrax lethal toxin is dependent on gelatinase expression and B-RAF status in human melanoma cells

Cited by 16 publications

References 28 publications

Inhibition of Tumor Angiogenesis by the Matrix Metalloproteinase–Activated Anthrax Lethal Toxin in an Orthotopic Model of Anaplastic Thyroid Carcinoma

Inhibition of Tumor Angiogenesis by the Matrix Metalloproteinase–Activated Anthrax Lethal Toxin in an Orthotopic Model of Anaplastic Thyroid Carcinoma

Effects of Introducing a Single Charged Residue into the Phenylalanine Clamp of Multimeric Anthrax Protective Antigen

Tumor therapy with a urokinase plasminogen activator-activated anthrax lethal toxin alone and in combination with paclitaxel

Contact Info

Product

Resources

About