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Updated: Jun 14, 2026
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Published on: December 23, 2022
Direct assessment of P-glycoprotein efflux to determine tumor response to chemotherapy
Gauri Patwardhan1, Vineet Gupta, Juowen Huang
1Department of Basic Pharmaceutical Sciences, University of Louisiana at Monroe, Monroe, LA 71209, USA.
Abstract:
Multidrug resistance is a major impediment to the success of cancer chemotherapy. The overproduced P-glycoprotein that extrudes anticancer drugs from cells, is the most common mechanism detected in multidrug-resistant cancers. Direct measurement of cellular efflux of tumors in vivo, rather than estimation of MDR1 mRNA and P-glycoprotein levels in samples stored or embedded, can functionally characterize the mechanism of drug resistance and determine the choice of anticancer drugs for cancer patients. Herewith, we introduce a new approach to directly determine P-glycoprotein efflux of tumors. Employing Flutax-2 (Oregon green-488 paclitaxel) and fluorescence spectrophotometry, this method has successfully measured cellular transportability including efflux and accumulation in diverse cancer cell lines, tumors and other tissues with high reproducibility. With this method, we have quantitatively determined cellular efflux that is correlated with P-glycoprotein levels and the reversal effects of agents in cell lines of breast, ovarian, cervical and colon cancers, and in tumor-bearing mice. It has sensitively detected these alterations of P-glycoprotein efflux in approximately 5mg tumor or other tissues with high confidence. This direct and quick functional assessment has a potential to determine drug resistance in different types of cancers after surgical resection. Further validation of this method in clinic settings for the diagnosis of drug resistance purpose is needed.
Insights
This study introduces a new method to directly measure P-glycoprotein efflux in tumors, aiding in the selection of effective cancer chemotherapy drugs. This functional assessment can guide personalized cancer treatment by identifying drug resistance mechanisms.
Area of Science:
- Oncology
- Biochemistry
- Pharmacology
Background:
- Multidrug resistance (MDR) significantly hinders cancer chemotherapy efficacy.
- Overexpression of P-glycoprotein, which actively transports anticancer drugs out of cells, is a primary MDR mechanism.
- Current methods assessing MDR rely on indirect measurements like mRNA or protein levels, not direct functional efflux.
Purpose of the Study:
- To develop and validate a novel method for directly measuring P-glycoprotein-mediated drug efflux in tumors.
- To functionally characterize drug resistance mechanisms in various cancer types.
- To assess the potential of this method for guiding clinical treatment decisions.
Main Methods:
- Utilized Flutax-2 (Oregon green-488 paclitaxel) and fluorescence spectrophotometry.
- Measured cellular transport (efflux and accumulation) of Flutax-2 in cancer cell lines, tumor tissues, and other tissues.
- Quantitatively assessed P-glycoprotein efflux in diverse cancer models, including tumor-bearing mice.
Main Results:
- The method demonstrated high reproducibility in measuring cellular transportability.
- Directly measured cellular efflux correlated with P-glycoprotein levels and the efficacy of MDR reversal agents.
- Successfully detected alterations in P-glycoprotein efflux in small tissue samples (approx. 5mg) with high confidence.
- The approach was validated in breast, ovarian, cervical, and colon cancer models.
Conclusions:
- This novel approach provides a direct, rapid, and sensitive functional assessment of P-glycoprotein-mediated drug efflux.
- It has the potential to guide the selection of anticancer drugs by identifying drug resistance in various cancers post-resection.
- Further clinical validation is required to establish its utility for diagnosing drug resistance in patient care.
