Abstract 268P
Background
Transforming growth factor-beta (TGF-β) was found to promote chemoresistance. Deletion of Transforming growth factor-beta receptor 2 (Tgfbr2) in mammary epithelial cells results in increased Chemokine receptor 2 (CXCR2) signaling, leading to increased recruitment of Gr-1+CD11b+cell- Myeloid derived suppressor cells (MDSCs) and levels of TGF-ß in tumor microenviroment (TME). Blockade of CXCR2 or corresponding ligands “Chemokine ligands” (CXCLs) enhanced prognosis in different disease models. Resistance to Doxorubicin is frequently evident in Triple negative breast Cancer (TNBC). AZD5069 is a selective small-molecule antagonist of human CXCR2 that has satisfactory safety and tolerability in advanced malignancies. Many clinical trials are now testing AZD5069 for its efficacy in resistant prostate cancer and other solid tumors. This study investigates the use of AZD5069 in combination with Doxorubicin in chemoresistant TNBC.
Methods
Mammosphere assay (EGF, B27, b-FGF in DMEM/F12 media) was performed to generate chemoresistant MDA-MB231 sphere-forming cells, followed by AZD5069 dose-response experiment (0.75 nM-150 μM) for 72hrs to test its inhibitory effect on CXCR2 surface expression using flow cytometry. Doxorubicin IC50 dose was calculated in MDA cells using MTT assay. Lactate dehydrogenase(LDH) cytoxicity assay and ELISA (to measure TGF-β release) were performed on mammospheres treated with doxorubicin and/or AZD5069.
Results
The Doxorubicin IC50 was ineffective on chemoresistant mammosphere compared to MDA cells (p=0.0001). Flow cytometry showed a maximum inhibition of CXCR2 at 150 nM AZD5069. TGF-β decreased in mammospheres TME at 150 nM AZD506 (p=0.0155). LDH assay showed that 50 μM AZD5069 alone & 150 nM AZD5069 alone had the same cytotoxic effect. The combination of 320 nM doxorubicin and 150 nM AZD5069 showed an additive increase in cytotoxicity than each drug alone (p=0.03 and p=0.046, respectively). Moreover, the combination of 320 nM doxorubicin and 50 μM AZD5069 showed an increase in cytotoxicity than each drug alone (p=0.006 and p=0.015, respectively).
Conclusions
This study sheds light on the novel CXCR2 antagonists as a potential therapeutic approach to decrease the fierce chemoresistance in TNBC.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Molecular Pharmacology Research Group, German University in Cairo, Egypt.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.