Abstract 2046: Investigation of MDR1 in ovarian cancer using biodynamic imaging
Authors: Narayanan Gayatri , Nolte David D. , Matei Daniela , An Ran , Turek John J. 
Published: July 2017

Multidrug resistance is one of the main causes of ineffective treatment of ovarian cancer. Almost 80% of advanced cases have recurring malignancies after treatment, even after initial responsiveness to the usual platinum-based chemotherapeutics. One of the many mechanisms for resistance is the transmembrane drug efflux pump p-glycoprotein, encoded by the gene MDR1. It has been shown that overexpression of this protein in ovarian cancer is associated with poor chemotherapeutic response and multidrug resistance due to low intracellular accumulation of the drug. Its wide substrate specificity allows it to pump out several common drugs such as vincristine, paclitaxel, doxorubicin, and etoposide. Biodynamic imaging (BDI) is a low-coherence form of digital holography that provides deep 3D functional information on intratumor subcellular motility and provides spectral signatures related to drug mode of action and for mitosis, apoptosis, and necrosis. BDI is currently being used in clinical trials to identify drug resistance in patient tumor biopsies. It was hypothesized that ovarian cancer spheroids with varying degrees of platinum resistance and p-glycoprotein would have identifiable p-glycoprotein signatures that could serve as a spectral biomarker for drug resistance.

Ovarian cancer tumor spheroids from the A2780 and SKOV3 cell lines were cultured with varying degrees of cisplatin to select for increasing platinum resistance and p-glycoprotein as detected by immunofluorescence and western blot analysis. Cells were grown as 3D spheroids and treated with anticancer drugs that are known p-glycoprotein substrates such as doxorubicin and paclitaxel. Treatments were used in combination with and without p-glycoprotein inhibitors such as verapamil and zosuquidar. For BDI, background spectral data was collected for 3 hrs and then for 9 hrs after drug treatment. Parallel experiments were done in 2D cultured cells in 96-well plates and cell viability was assessed with the XTT assay.

A suppression of average intracellular motion in the low-frequency range (0.01 Hz) was observed when 20 µM verapamil was used in combination with 10 µM paclitaxel in A2780 cells. This result may be due to the microtubule stabilizing effect of paclitaxel. SKOV3 spheroids were treated with verapamil plus 10 µM doxorubicin. Doxorubicin treated spheroids have increased high (10 Hz) and low (0.01 Hz) spectral signatures indicative of apoptosis. Addition of MDR1 modulators resulted in frequency changes associated with a greater apoptotic response in SKOV3 spheroids.

Modulation of p-glycoprotein alters the spectral response to drugs in a manner associated with the drug mode of action. A specific MDR1 spectral signature was not observed in these experiments but experiments with MDR1 silenced spheroids are underway to identify a possible signature.

Citation Format: Gayatri Narayanan, David D. Nolte, Daniela Matei, Ran An, John J. Turek. Investigation of MDR1 in ovarian cancer using biodynamic imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2046. doi:10.1158/1538-7445.AM2017-2046