Analysis of multidrug resistant transporter expression in tumor blood vessels of urothelial carcinoma during chemotherapy.

Abstract

e23004 Background: ABCB1, a multidrug transporter, is encoded by multidrug resistance (MDR) 1 gene and plays a major role in drug resistance. Recently, we have reported that not only tumor cells, tumor vascular endothelial cells (TECs) also confer cancer drug resistance. We isolated TECs and found that they have various abnormalities such as aneuploidy or stemness characteristics. TECs showed resistance to Paclitaxel (PTX) with ABCB1 up-regulation. Furthermore, their resistance to PTX was abrogated by ABCB1 inhibition of TECs in vivo. In clinical urology, gemcitabine / cisplatin (GC) is standard 1st line chemotherapy for metastatic urothelial carcinoma (mUC). PTX is often selected in 2nd line chemotherapy for GC resistant cases, however the therapeutic outcomes are limited. We hypothesized that ABCB1 inhibitor/PTX combination would be more effective strategy for mUC, if TEC ABCB1 expression is upregulated. In this study, we investigated ABCB1 expression in tumor blood vessels of UC during 1st line chemotherapy. Methods: Paraffin-embedded samples were corrected from 50 patients who were performed tumor resection before and after 1st line chemotherapy. ABCB1 expressions were analyzed by immunohistochemical staining and the ratio of ABCB1 positive (+) vessels in total vessels were quantified. In vitro assays were performed to address how endothelial cells (ECs) are affected by change of tumor microenvironment during chemotherapy. Results: The ABCB1 (+) vessels were 0.00 – 16.80% (Median 0.00%) and 0.00-58.94% (Median 4.49%), before and after chemotherapy, respectively. In 32 of 50 cases (64%), the ratio of ABCB1 (+) vessels increased after 1st line chemotherapy. Additionally, gemcitabine induced MDR1 mRNA expression in ECs via NF-kB activation. Furthermore, gemcitabine and cisplatin induced IL-8 secretion from tumor cells, and MDR1 mRNA expression level was elevated in ECs. Conclusions: It was suggested that conventional chemotherapy may cause inflammatory change in tumor tissues, which causes in ABC transporter induction in tumor blood vessels. It was suggested that inhibition of ABC transporter in TECs is one of important new strategy to overcome cancer drug resistance.