Ganciclovir and Its Hemocompatible More Lipophilic Derivative Can Enhance the Apoptotic Effects of Methotrexate by Inhibiting Breast Cancer Resistance Protein (BCRP)

Magdalena Markowicz-Piasecka,Ahmed Montaser,Seppo Auriola,Johanna Huttunen,Santosh Kumar Adla,Marko Lehtonen,Kristiina M Huttunen

doi:10.3390/ijms22147727

Abstract

Efflux transporters, namely ATP-binding cassette (ABC), are one of the primary reasons for cancer chemoresistance and the clinical failure of chemotherapy. Ganciclovir (GCV) is an antiviral agent used in herpes simplex virus thymidine kinase (HSV-TK) gene therapy. In this therapy, HSV-TK gene is delivered together with GCV into cancer cells to activate the phosphorylation process of GCV to active GCV-triphosphate, a DNA polymerase inhibitor. However, GCV interacts with efflux transporters that are responsible for the resistance of HSV-TK/GCV therapy. In the present study, it was explored whether GCV and its more lipophilic derivative (1) could inhibit effluxing of another chemotherapeutic, methotrexate (MTX), out of the human breast cancer cells. Firstly, it was found that the combination of GCV and MTX was more hemocompatible than the corresponding combination with compound 1. Secondly, both GCV and compound 1 enhanced the cellular accumulation of MTX in MCF-7 cells, the MTX exposure being 13–21 times greater compared to the MTX uptake alone. Subsequently, this also reduced the number of viable cells (41–56%) and increased the number of late apoptotic cells (46–55%). Moreover, both GCV and compound 1 were found to interact with breast cancer resistant protein (BCRP) more effectively than multidrug-resistant proteins (MRPs) in these cells. Since the expression of BCRP was higher in MCF-7 cells than in MDA-MB-231 cells, and the cellular uptake of GCV and compound 1 was smaller but increased in the presence of BCRP-selective inhibitor (Fumitremorgin C) in MCF-7 cells, we concluded that the improved apoptotic effects of higher MTX exposure were raised mainly from the inhibition of BCRP-mediated efflux of MTX. However, the effects of GCV and its derivatives on MTX metabolism and the quantitative expression of MTX metabolizing enzymes in various cancer cells need to be studied more thoroughly in the future.

Highlights

Multidrug resistance (MDR) is a common feature of many cancer types and a major challenge in clinical cancer treatment with chemotherapeutics [1,2,3]
The protein expression of breast cancer resistant protein (BCRP), MRP1, MRP4, and P-gp were quantified from the plasma membrane fractions of the selected human breast cancer cells, estrogen receptorpositive MCF-7 and triple-negative MDA-MB-231 (Figure 1)
The quantifications of MRP4 were close to the lowest level of quantification (LLOQ), and the numerical values of MRP4 need to be interpreted with caution

Summary

Introduction

Multidrug resistance (MDR) is a common feature of many cancer types and a major challenge in clinical cancer treatment with chemotherapeutics [1,2,3]. In MDR, cancer cells have an intrinsic or acquired resistance towards a wide variety of anticancer drugs that significantly reduces the effectiveness of chemotherapy and most often causes cancer recurrence. Other efflux transporters, such as multidrug resistance protein 1 (MRP1, ABCC1) and breast cancer resistant protein (BCRP, ABCG2), known as mitoxantrone resistant protein (MXR), were associated with clinical MDR. Despite the extensive research with efflux transporter inhibitors, their success in clinical use has been modest, mainly because of the challenge of targeting these inhibitors only into the cancer cells [2,3,4,5]

Methods

Results

Conclusion