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Proliferation indices as molecular pharmacodynamic endpoints in evaluation of anticancer drug effect in human solid
1College of Pharmacy, The Ohio State University, Columbus 43210, USA.
Purpose:
The present study compared proliferative indices, i.e. incorporation of DNA precursor (i.e. thymidine or TdR, and bromodeoxyuridine or BrdU) and expression of proliferating cell nuclear antigen (PCNA), as molecular pharmacodynamic endpoints in evaluation of anticancer drug effect in human solid tumors.
Methods:
Tumor specimens obtained from patients were grown as histocultures. After treatment with doxorubicin, mitomycin C, and/or paclitaxel, cells labeled by [3H]TdR were identified using autoradiography, and cells labeled by BrdU and PCNA were identified using immunohistochemical techniques. Drug effect was measured as reduction of DNA precursor-labeled cells or PCNA-expressing cells.
Results:
The results indicate that (a) the two DNA precursors, TdR and BrdU, labeled the same cells and resulted in identical pharmacodynamics, (b) the pharmacodynamics established using inhibition of DNA precursor incorporation were qualitatively and quantitatively different from the pharmacodynamics established using inhibition of PCNA expression, (c) the inhibition of PCNA expression was erratic in some tumors, and (d) the differences in pharmacodynamics established using the two end points are drug-specific, with greater differences for paclitaxel than for mitomycin C.
Conclusions:
The erratic results measured by the PCNA labeling method suggest that this method may be less reliable than the conventional DNA precursor labeling method. The finding of identical pharmacodynamics of doxorubicin and paclitaxel established using BrdU and [3H]TdR indicates that the two precursors are interchangeable. Because the methodology for detecting BrdU incorporation requires less time and does not require the use of radioactivity, we conclude that inhibition of BrdU incorporation represents a useful endpoint for evaluating the antiproliferative activity of anticancer drugs in human solid tumors.
Insights
Bromodeoxyuridine (BrdU) incorporation is a reliable method for evaluating anticancer drug effects in solid tumors. This DNA precursor labeling method is interchangeable with thymidine (TdR) and more consistent than proliferating cell nuclear antigen (PCNA) expression.
Area of Science:
- Pharmacology
- Oncology
- Molecular Biology
Background:
- Evaluating anticancer drug efficacy requires reliable pharmacodynamic endpoints.
- Proliferative indices, including DNA precursor incorporation and PCNA expression, are used to assess drug effects.
- Human solid tumor models are crucial for preclinical drug evaluation.
Purpose of the Study:
- To compare DNA precursor incorporation (thymidine/TdR and bromodeoxyuridine/BrdU) and proliferating cell nuclear antigen (PCNA) expression as molecular pharmacodynamic endpoints.
- To evaluate the effect of anticancer drugs (doxorubicin, mitomycin C, paclitaxel) on these proliferative indices in human solid tumors.
- To determine the reliability and interchangeability of different methods for assessing antiproliferative activity.
Main Methods:
- Human solid tumor specimens were cultured and treated with anticancer drugs.
- DNA precursor incorporation was measured using [3H]TdR (autoradiography) and bromodeoxyuridine (BrdU) (immunohistochemistry).
- Proliferating cell nuclear antigen (PCNA) expression was assessed using immunohistochemical techniques.
Main Results:
- Thymidine (TdR) and bromodeoxyuridine (BrdU) labeling yielded identical pharmacodynamic results, indicating interchangeability.
- Pharmacodynamics derived from DNA precursor incorporation differed from those derived from PCNA expression.
- PCNA expression showed erratic inhibition in some tumors, suggesting potential unreliability.
- Drug-specific differences in pharmacodynamics were observed, with paclitaxel showing greater divergence than mitomycin C.
Conclusions:
- Bromodeoxyuridine (BrdU) incorporation is a reliable and interchangeable alternative to thymidine (TdR) for assessing antiproliferative activity.
- The DNA precursor labeling method is more reliable than PCNA expression due to erratic results with the latter.
- Inhibition of BrdU incorporation is a valuable endpoint for evaluating anticancer drug efficacy in human solid tumors, offering advantages in speed and avoidance of radioactivity.