Related Experiment Videos
Pyrazoloacridine is active in multidrug-resistant neuroblastoma cell lines with nonfunctional p53
Nino Keshelava1, Denice Tsao-Wei, C Patrick Reynolds
1Department of Pediatrics, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA.
Purpose:
The purpose of this study was to determine the activity of pyrazoloacridine (PZA) in neuroblastomas that have acquired high-level resistance to multiple drugs (not associated with multidrug resistance-associated protein or P-glycoprotein) during therapy, including those with loss of p53 function.
Experimental Design:
We determined the activity of PZA in 12 drug-sensitive and 10 multidrug-resistant (MDR) neuroblastoma cell lines. Six of the MDR cell lines lacked functional p53. Drug cytotoxicity was measured using the DIMSCAN fluorescence/digital imaging microscopy assay with a 4-log dynamic range.
Results:
LC(90) (i.e., the drug concentration that was lethal for 90% of the cell population) values ranged from 0.01 to 1.1 microM for the drug-sensitive cell lines, from 0.8 to 2.4 microM for the MDR cell lines with functional p53, and from 0.9 to 2.1 microM for the MDR cell lines that lacked functional p53. To confirm that PZA cytotoxicity is independent of p53 function, we compared two neuroblastoma cell lines in which p53 function was abrogated via human papilloma virus-16 E6 transduction (which mediates increased degradation of p53) to the mock-transduced (LXSN) controls. LC(90) values for human papilloma virus-16 E6 clones (abrogated p53) ranged from 0.2 to 2.04 micro M, whereas LC(90) values for LXSN controls (functional p53) were 0.1 and 0.5 microM. PZA was active with 72-h in vitro exposures against p53-nonfunctional MDR cells at drug levels (2-3 microM) obtained for shorter periods (1-3 h) in Phase I and II clinical trials. Washout experiments showed that 3 micro M PZA achieved 0.5-1 log of cell kill with 1-3-h exposures versus 3 logs at 24 h.
Conclusions:
These data suggest that expanding the time of PZA systemic exposure, which may be clinically tolerable with hematopoietic stem cell support, should be tested in clinical trials. Prolonged systemic exposure to PZA with hematopoietic stem cell support may be effective against recurrent neuroblastomas that have failed conventional chemotherapeutic regimens, including those neuroblastomas with loss of p53 function.
Insights
Pyrazoloacridine (PZA) demonstrates activity against multidrug-resistant neuroblastomas, even those lacking p53 function. Prolonged exposure may offer a new therapeutic strategy for recurrent neuroblastoma. Keywords: Pyrazoloacridine, PZA, neuroblastoma, drug resistance, p53 function, cancer therapy.
Area of Science:
- Oncology
- Pharmacology
- Molecular Biology
Background:
- Neuroblastomas often develop high-level multidrug resistance (MDR) during therapy.
- This resistance can occur independently of common mechanisms like P-glycoprotein or MRP.
- Loss of p53 tumor suppressor function is frequently observed in aggressive neuroblastomas.
Purpose of the Study:
- To evaluate the efficacy of pyrazoloacridine (PZA) against drug-resistant neuroblastoma cell lines.
- To determine if PZA activity is affected by the loss of p53 function in these resistant cells.
Main Methods:
- Assessed PZA cytotoxicity in 12 drug-sensitive and 10 MDR neuroblastoma cell lines using DIMSCAN digital imaging microscopy.
- Included MDR lines with and without functional p53, and used HPV-16 E6 transduction to abrogate p53 function.
Main Results:
- PZA exhibited significant cytotoxicity across sensitive and resistant neuroblastoma lines (LC90 values 0.01–2.4 µM).
- PZA activity was independent of p53 function, with similar efficacy in cell lines with and without functional p53.
- Effective concentrations against p53-nonfunctional MDR cells were achievable with prolonged exposure (72h) compared to shorter clinical trial exposures (1-3h).
Conclusions:
- Pyrazoloacridine (PZA) shows promise as a therapeutic agent for multidrug-resistant neuroblastomas, including those with p53 loss.
- Extending PZA exposure time, potentially with hematopoietic stem cell support, warrants clinical investigation for recurrent or refractory neuroblastoma.