Breast cancer resistance protein-mediated topotecan resistance in ovarian cancer cells

Abstract

Overexpression of breast cancer resistance protein (BCRP) and mitoxantrone (MX) resistance protein can confer resistance to a variety of cytostatic drugs, such as MX, topotecan (TPT), doxorubicin, and daunorubicin. This study investigates the role of BCRP in resistance of ovarian cancer to TPT treatment. We have developed TPT-resistant human ovarian cancer cell line. Intracellular concentration of fluorescent dye rhodamine 123 (Rh123) was measured by flow cytometry. The expression of several membrane transporter proteins including P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), and BCRP were determined by reverse transcription-polymerase chain reaction and Western blotting. The Rh123 concentration in parental cells was approximately three times of those in TPT-resistant cells. In contrast to undetectable level of P-gp messenger RNA (mRNA) and minimal level of MRP1 expression in TPT-resistant cells, overexpression of both the BCRP mRNA and the protein was detected in these cells. Introduction of antisense-phosphorothioate oligonucleotide derived from BCRP mRNA into TPT-resistant cells resulted in a significant increase in the concentration of intracellular Rh123. These results suggested a novel mechanism in which a reduced intracellular drug concentration may be mediated by BCRP gene products in human ovarian cancer cells.

Stemness and chemoresistance are imparted to the OC cells through TGFβ1 driven EMT

“…This observation can be used to infer that in the OC cells, EMT bestows CSC‐like features along with the drug resistance. Rh123 is a known substrate of the ABC transporter family, especially ABCG2, which has an efflux property in breast, and OC tissues . Verapamil, an inhibitor of these transport pumps, binds to them and prevents their activity, thus helping in drug retention in these chemoresistant cells and sensitizing them towards cytotoxicity in response to platinum drugs like cisplatin (Figure ).…”

“…Rh123 is a known substrate of the ABC transporter family, especially ABCG2, which has an efflux property in breast, and OC tissues. 33,39,40 Verapamil, an inhibitor of these transport pumps, binds to them and prevents their activity, 41 thus helping in drug retention in these chemoresistant cells and sensitizing them towards cytotoxicity in response to platinum drugs like cisplatin ( Figure 5). Among the different EMT promoting transcription factors, we found ZEB1 to be of prime importance in the gain of stemness in the OC cells.…”

Novel ABCG2 Antagonists Reverse Topotecan-Mediated Chemotherapeutic Resistance in Ovarian Carcinoma Xenografts

“…Currently, only about 20% of recurrent tumors respond to second-line therapy. (1,2,7) Despite the fact that ABCG2 has been well described as the key mechanism for resistance of ovarian cancer to TPT,(1,13,44) relatively few attempts to develop drugs at this important target have been made. Moreover, the compounds that have been created and tested in ovarian cancer have not progressed, typically due to toxicity.…”

Metronomic Oral Topotecan with Pazopanib Is an Active Antiangiogenic Regimen in Mouse Models of Aggressive Pediatric Solid Tumor

“…Low dose metronomic (LDM) chemotherapy, which acts in part by targeting the endothelial cells of the neovasculature of tumors and blocking mobilization of endothelial progenitor cells (CEP) from the bone marrow, represents an attractive and effective antiangiogenic strategy (3–5). Drawbacks to using pulse topotecan include resistance of tumor cells and the crossresistance with topoisomerase-II inhibitors in neuroblastoma cell lines (6, 7). LDM regimens of topotecan, which may target endothelial cells and tumor cells by other mechanisms, can possibly overcome some of these limitations.…”