Identification of diphtheria toxin via screening as a potent cell cycle and p53-Independent cytotoxin for human prostate cancer therapeutics

Ronald Rodriguez, Ho Yeong Lim, Lisa M. Bartkowski, Jonathan W. Simons

Research output: Contribution to journalArticle

Abstract

BACKGROUND. Metastatic human prostate cancer requires novel therapeutic strategies in order to overcome its low proliferative rate and its resistance to conventional chemotherapeutic agents. To identify potential cytotoxin gene products for use in experimental therapeutics such as in vivo gene therapy, an in vitro screen was designed. METHODS. Eight recombinant cellular toxins were tested for activity against a spectrum of metastatic human prostate cancer cell phenotypes. Pseudomonas exotoxin A, ricin, tumor necrosis factor alpha (TNF-α), diphtheria toxin (DT), Crotalus durissus terrificus toxin, crotalus adamenteus toxin, Naja naja toxin, and Naja mocambique toxin were evaluated. Comparative survival distinguished the relative potencies of these cytotoxins for irreparable prostate cancer cell death. RESULTS. Of the phospholipase A2 toxins, Crotalus durissus terrificus and Naja mocambique are active against the PSA secreting LNCaP cell line; however, the effect is reversible, and no other hormone refractory prostate cell line tested is sensitive. Screening identified toxin-specific differences: dose-dependent cytotoxic activity against all human prostate cancer cell lines tested was only identified for ricin and diphtheria toxin (DT) as highly potent. DT has an IC50 in the range of 20-00 pM by clonogenic survival and kills irreversibly by both apoptosis as well as nonapototic pathways. Acquisition of p53 mutant status conferred no reduction in sensitivity to DT cytotoxicity. Cell cycle arrest by aphidicolin did not protect human prostate cells from irreversible DT-induced cell death. TNF-α had modest cytostatic activity in the screen; however, the combination of TNF-α and DT resulted in marked acceleration of the time to prostate cancer cell death. CONCLUSIONS. The rational screening of cytotoxins allows the identification of cell cycle- independent agents of variable potency against human prostate cancer. DT- mediated cell death is cell cycle independent, and p53 independent, making it particularly attractive for application to cytoreductive gene therapy, targeted monoclonal antibodies, and prodrug delivery of toxins applied to human prostate cancer therapeutics.

Original languageEnglish (US)
Pages (from-to)259-269
Number of pages11
JournalProstate
Volume34
Issue number4
DOIs
StatePublished - Mar 1 1998

Fingerprint

Diphtheria Toxin
Cytotoxins
Prostatic Neoplasms
Cell Cycle
Crotalus
Elapidae
Cell Death
Ricin
Tumor Necrosis Factor-alpha
Cell Line
Genetic Therapy
Therapeutics
Prostate
Aphidicolin
Survival
Phospholipases A2
Prodrugs
Cytostatic Agents
Cell Cycle Checkpoints
Inhibitory Concentration 50

Keywords

  • Apoptosis
  • Cell cycle
  • Diphtheria toxin
  • Gene therapy
  • P53
  • Prostate cancer

ASJC Scopus subject areas

  • Urology

Cite this

Identification of diphtheria toxin via screening as a potent cell cycle and p53-Independent cytotoxin for human prostate cancer therapeutics. / Rodriguez, Ronald; Lim, Ho Yeong; Bartkowski, Lisa M.; Simons, Jonathan W.

In: Prostate, Vol. 34, No. 4, 01.03.1998, p. 259-269.

Research output: Contribution to journalArticle

Rodriguez, Ronald ; Lim, Ho Yeong ; Bartkowski, Lisa M. ; Simons, Jonathan W. / Identification of diphtheria toxin via screening as a potent cell cycle and p53-Independent cytotoxin for human prostate cancer therapeutics. In: Prostate. 1998 ; Vol. 34, No. 4. pp. 259-269.
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T1 - Identification of diphtheria toxin via screening as a potent cell cycle and p53-Independent cytotoxin for human prostate cancer therapeutics

AU - Rodriguez, Ronald

AU - Lim, Ho Yeong

AU - Bartkowski, Lisa M.

AU - Simons, Jonathan W.

PY - 1998/3/1

Y1 - 1998/3/1

N2 - BACKGROUND. Metastatic human prostate cancer requires novel therapeutic strategies in order to overcome its low proliferative rate and its resistance to conventional chemotherapeutic agents. To identify potential cytotoxin gene products for use in experimental therapeutics such as in vivo gene therapy, an in vitro screen was designed. METHODS. Eight recombinant cellular toxins were tested for activity against a spectrum of metastatic human prostate cancer cell phenotypes. Pseudomonas exotoxin A, ricin, tumor necrosis factor alpha (TNF-α), diphtheria toxin (DT), Crotalus durissus terrificus toxin, crotalus adamenteus toxin, Naja naja toxin, and Naja mocambique toxin were evaluated. Comparative survival distinguished the relative potencies of these cytotoxins for irreparable prostate cancer cell death. RESULTS. Of the phospholipase A2 toxins, Crotalus durissus terrificus and Naja mocambique are active against the PSA secreting LNCaP cell line; however, the effect is reversible, and no other hormone refractory prostate cell line tested is sensitive. Screening identified toxin-specific differences: dose-dependent cytotoxic activity against all human prostate cancer cell lines tested was only identified for ricin and diphtheria toxin (DT) as highly potent. DT has an IC50 in the range of 20-00 pM by clonogenic survival and kills irreversibly by both apoptosis as well as nonapototic pathways. Acquisition of p53 mutant status conferred no reduction in sensitivity to DT cytotoxicity. Cell cycle arrest by aphidicolin did not protect human prostate cells from irreversible DT-induced cell death. TNF-α had modest cytostatic activity in the screen; however, the combination of TNF-α and DT resulted in marked acceleration of the time to prostate cancer cell death. CONCLUSIONS. The rational screening of cytotoxins allows the identification of cell cycle- independent agents of variable potency against human prostate cancer. DT- mediated cell death is cell cycle independent, and p53 independent, making it particularly attractive for application to cytoreductive gene therapy, targeted monoclonal antibodies, and prodrug delivery of toxins applied to human prostate cancer therapeutics.

AB - BACKGROUND. Metastatic human prostate cancer requires novel therapeutic strategies in order to overcome its low proliferative rate and its resistance to conventional chemotherapeutic agents. To identify potential cytotoxin gene products for use in experimental therapeutics such as in vivo gene therapy, an in vitro screen was designed. METHODS. Eight recombinant cellular toxins were tested for activity against a spectrum of metastatic human prostate cancer cell phenotypes. Pseudomonas exotoxin A, ricin, tumor necrosis factor alpha (TNF-α), diphtheria toxin (DT), Crotalus durissus terrificus toxin, crotalus adamenteus toxin, Naja naja toxin, and Naja mocambique toxin were evaluated. Comparative survival distinguished the relative potencies of these cytotoxins for irreparable prostate cancer cell death. RESULTS. Of the phospholipase A2 toxins, Crotalus durissus terrificus and Naja mocambique are active against the PSA secreting LNCaP cell line; however, the effect is reversible, and no other hormone refractory prostate cell line tested is sensitive. Screening identified toxin-specific differences: dose-dependent cytotoxic activity against all human prostate cancer cell lines tested was only identified for ricin and diphtheria toxin (DT) as highly potent. DT has an IC50 in the range of 20-00 pM by clonogenic survival and kills irreversibly by both apoptosis as well as nonapototic pathways. Acquisition of p53 mutant status conferred no reduction in sensitivity to DT cytotoxicity. Cell cycle arrest by aphidicolin did not protect human prostate cells from irreversible DT-induced cell death. TNF-α had modest cytostatic activity in the screen; however, the combination of TNF-α and DT resulted in marked acceleration of the time to prostate cancer cell death. CONCLUSIONS. The rational screening of cytotoxins allows the identification of cell cycle- independent agents of variable potency against human prostate cancer. DT- mediated cell death is cell cycle independent, and p53 independent, making it particularly attractive for application to cytoreductive gene therapy, targeted monoclonal antibodies, and prodrug delivery of toxins applied to human prostate cancer therapeutics.

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