Abstract B058: Role of IL8-CXCR1/2 axis in glioblastoma cell proliferation, invasion, and vascular mimicry

Background: Glioblastoma multiforme (GBM) is the most fatal neoplasm of the central nervous system. There is an ongoing quest for improving GBM therapy owing to limited success in current treatment modalities. Chemokines are known to play a critical role in tumor cell proliferation and invasion. Previously we had studied gene expression of complete panel of chemokines and their receptors to identify pro-gliomagenic chemokine axis. Based on our gene expression study and comparison with other publicly available datasets, we identified IL-8 as most frequently upregulated chemokine in GBM as compared to low-grade astrocytoma. In the present study we aimed to elucidate the role of IL-8-CXCR1/2 axes in GBM progression. Methods: The protein expression pattern of IL-8 and its receptors, CXCR1 and CXCR2, in GBM was studied using immunohistochemistry. Furthermore, we checked the impact of targeting IL-8 in vitro in two GBM cell lines to understand its direct role in GBM cell proliferation and invasion. We first checked the expression of IL-8-CXCR1/2 axes by RT-PCR and immunocytochemistry. IL-8-CXCR1/2 axes were targeted using neutralizing antibodies as well as by pharmacologic antagonist reparixin-l-lysine. The impact on cell proliferation and viability was assessed by MTT assay and clonogenic survival assay. Spheroid invasion assay was performed to assess the impact on invasion. Results: The protein localization by immunohistochemistry revealed cytoplasmic expression of IL-8 and CXCR2 in tumor cells while CXCR1 was predominantly present in tumor-associated microvessels, suggesting both autocrine and paracrine modes of signalling. However, the exact biologic action exerted by IL-8-CXCR1/2 axes was unraveled in in vitro experiments where discernible reduction in cell proliferation and survival was observed in U-87MG and LN-18 cell lines on neutralizing IL-8 and its receptors with neutralizing antibodies. Similar effect was also observed on treatment with reparixin-l-lysine. Pharmacologic blocking of CXCR1/2 also resulted in significant reduction in spheroid invasion and clonogenic survival in U-87MG and LN-18 cell lines. Neutralizing CXCR1 alone or in combination with IL-8 resulted in disruption of tubular network in U-87MG cell line, suggesting a possible role in vascular mimicry (VM). Further comparison of CXCR1 and CD34 immunostaining conceded existence of CXCR1+/CD34- microvessels in GBM, confirming the involvement of IL-8-CXCR1 axis in VM structure formation. Conclusion: These results suggest an important role of IL-8-CXCR1/2 axes in GBM biology, which supports their mitogenic as well as angiogenic function, displaying a strong potential as candidate therapeutic target in treatment of GBM. Citation Format: Ira Sharma, Avninder Singh, Fouzia Siraj, Sunita Saxena. Role of IL8-CXCR1/2 axis in glioblastoma cell proliferation, invasion, and vascular mimicry [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B058.