Doxazolidine Induction of Apoptosis by a Topoisomerase II Independent Mechanism

Abstract

The mechanism of doxorubicin is compared with that of doxazolidine, a doxorubicinformaldehyde conjugate. The IC 50 for growth inhibition of 67 human cancer cell lines, but not cardiomyocytes, is 32-fold lower with doxazolidine than with doxorubicin. Growth inhibition by doxazolidine correlates better with growth inhibition by DNA crosslinking agents than with growth inhibition by doxorubicin. Doxorubicin induces G2/M arrest in HCT-116 colon cancer cells and HL-60 leukemia cells through a well-documented topoisomerase II-dependent mechanism. Doxazolidine fails to induce a G2/M arrest in HCT-116 cells, but induces apoptosis 4-fold better than doxorubicin. The IC 50 for doxazolidine growth inhibition of HL-60/MX2 cells, a topoisomerase II-deficient derivative of HL-60 cells, is 1420-fold lower than the IC 50 for doxorubicin, and doxazolidine induces apoptosis 15-fold better. Further, Doxazolidine has little effect in a topoisomerase II activity assay. These data indicate that doxorubicin and doxazolidine induce apoptosis via different mechanisms and doxazolidine cytotoxicity is topoisomerase IIindependent.

Photoactivatable Prodrug of Doxazolidine Targeting Exosomes

“…Interestingly, l -MARCKS–ED–photodox 4 (IC 50 : with UV = 1.2 μM, without UV = 6.5 μM) was 80-fold less toxic than 1 under UV light even though they differ by only a single carbon. This result supports the oxazolidine ring of doxaz being essential for high cellular growth inhibition . The IC 50 values of 1 and 2 are comparable to PPD and GaFK–PABC–doxaz with enzymatic activation. − …”

“…However, dose-dependent cardiotoxicity and acquisition of a multidrug-resistance phenotype including elevated expression of p-170 glycoprotein (P-170gp) hamper clinical efficacy. − Doxaz is a dox–formaldehyde conjugate at the 3′-NH 2 and 4′-OH groups. The IC 50 values of doxaz to cancer cells are 1–4 orders of magnitude lower than dox, and its potency is not affected by P-170gp because doxaz is an uncharged DNA alkylating agent at sites of 5′-GC-3′ , whereas dox is a cation at a physiological pH that inhibits the function of topoisomerase II. , However, the half-life of doxaz is approximately 3 min with respect to hydrolysis to dox under physiological conditions because of the unstable oxazolidine ring. ,, Therefore, prodrugs with stable carbamylated amino groups, the p -aminobenzyloxycarbonyl (PABC) groups, have been investigated for therapeutic applications of doxaz. We have reported two types of enzymatically cleavable prodrugs of doxaz: pentyl PABC–doxaz (PPD) and GaFK–PABC–doxaz (see abbreviations for definitions of acronyms). − PPD was designed to be activated by carboxylesterase 2 (CES2) expressed in the liver, nonsmall-cell lung, colon, pancreatic, renal, and thyroid cancer cells.…”

Transcription Factor Ets1 Cooperates with Estrogen Receptor α to Stimulate Estradiol-Dependent Growth in Breast Cancer Cells and Tumors

“…Apoptosis was measured as previously described [39] with minor modifications. Cells were plated at a density of 500,000 cells per well of a 6 well plate.…”

Differential in vitro activity of the DNA topoisomerase inhibitor idarubicin against Trypanosoma rangeli and Trypanosoma cruzi

“…No difference in cell cycle distribution compared to control cells was seen with 0.1 µM idarubicin (data not shown). This is reminiscent of the observation for doxazolidinetreated mammalian cells where apoptosis is induced and DNA is degraded (Kalet et al 2007). These data suggest that idarubicin's mechanism of cytotoxicity is probably topoisomerase II independent.…”