Targeting CXCR4 abrogates resistance to trastuzumab by blocking cell cycle progression and synergizes with docetaxel in breast cancer treatment

Abstract

Background Although trastuzumab and other HER2-targeted therapies have significantly improved survival in patients with HER2 overexpressed or amplified (HER2+) breast cancer, a significant proportion of patients do not respond or eventually develop clinical resistance. Strategies to reverse trastuzumab resistance remain a high clinical priority. We were the first to report the role of CXCR4 in trastuzumab resistance. The present study aims to explore the therapeutic potential of targeting CXCR4 and better understand the associated mechanisms. Methods Immunofluorescent staining, confocal microscopy analysis, and immunoblotting were used to analyze CXCR4 expression. BrdU incorporation assays and flow cytometry were used to analyze dynamic CXCR4 expression. Three-dimensional co-culture (tumor cells/breast cancer-associated fibroblasts/human peripheral blood mononuclear cells) or antibody-dependent cellular cytotoxicity assay was used to mimic human tumor microenvironment, which is necessary for testing therapeutic effects of CXCR4 inhibitor or trastuzumab. The FDA-approved CXCR4 antagonist AMD3100, trastuzumab, and docetaxel chemotherapy were used to evaluate therapeutic efficacy in vitro and in vivo. Reverse phase protein array and immunoblotting were used to discern the associated molecular mechanisms. Results Using a panel of cell lines and patient breast cancer samples, we confirmed CXCR4 drives trastuzumab resistance in HER2+ breast cancer and further demonstrated the increased CXCR4 expression in trastuzumab-resistant cells is associated with cell cycle progression with a peak in the G2/M phases. Blocking CXCR4 with AMD3100 inhibits cell proliferation by downregulating mediators of G2-M transition, leading to G2/M arrest and abnormal mitosis. Using a panel of trastuzumab-resistant cell lines and an in vivo established trastuzumab-resistant xenograft mouse model, we demonstrated that targeting CXCR4 with AMD3100 suppresses tumor growth in vitro and in vivo, and synergizes with docetaxel. Conclusions Our findings support CXCR4 as a novel therapeutic target and a predictive biomarker for trastuzumab resistance in HER2+ breast cancer.

Integrative Bioinformatics Analysis of CXCR-4 (C-X-C motif chemokine receptor 4): Expression Pattern and Role in Breast Cancer Progression

“…T regulatory cells (Tregs) play a crucial role in modulating the immune response of the host to both infections and neoplastic growth [40]. Tumor cells employ regulatory T cells (Tregs) as a mechanism for evading anti-tumor immune responses [40]. The ndings of our study indicate a strong correlation between CXCR4 and an immunosuppressive tumor microenvironment.…”

“…Furthermore, the TIMER 2.0 analysis revealed a signi cant association between cancer-associated broblasts (CAFs), regulatory T cells (Tregs), and CXCR4 expression, suggesting that CXCR4 plays a crucial role in sustaining an immunosuppressive milieu within the tumor. T regulatory cells (Tregs) play a crucial role in modulating the immune response of the host to both infections and neoplastic growth [40]. Tumor cells employ regulatory T cells (Tregs) as a mechanism for evading anti-tumor immune responses [40].…”

Proliferating CLL cells express high levels of CXCR4 and CD5

“…Direct regulation of the cell cycle by CXCR4 has yet to be established in CLL although previous studies have implicated CXCR4 signalling in cell cycle regulation in solid tumours. CXCR4 silencing inhibits cell growth in human carcinoma cell lines 33 and increased expression of CXCR4 in G2/M phases has been reported in breast cancer cell lines where proteomic analysis revealed crosstalk between CXCR4 and G2-M transition proteins such as PLK1 and Cyclin B1 34 . This suggests that rather than a surrogate marker for cell division, active CXCR4 signalling in CLL cells may be an important regulator of the mitotic process.…”

Tumorigenic effects of human mesenchymal stromal cells and fibroblasts on bladder cancer cells

“…Tripathy et al. could demonstrate that blocking CXCR-4 with a specific antibody (AMD3100) synergizes with docetaxel and led to abnormal mitosis in resistant cell lines ( 87 ). Thus, our results may indicate that AMD3100 could also be suitable for synergistic therapy in UC.…”