IKKβ targeting reduces KRAS-induced lung cancer angiogenesis in vitro and in vivo: A potential anti-angiogenic therapeutic target

Objectives: The ability of tumor cells to drive angiogenesis is an important cancer hallmark that positively correlates with metastatic potential and poor prognosis. Therefore, targeting angiogenesis is a rational therapeutic approach and dissecting proangiogenic pathways is important, particularly for malignancies driven by oncogenic KRAS, which are widespread and lack effective targeted therapies. Based on published studies showing that oncogenic RAS promotes angiogenesis by upregulating the proangiogenic NF-kappa B target genes IL-8 and VEGF, that NF-kappa B activation by KRAS requires the IKK beta kinase, and that targeting IKK beta reduces KRAS-induced lung tumor growth in vivo, but has limited effects on cell growth in vitro, we hypothesized that IKK beta targeting would reduce lung tumor growth by inhibiting KRAS-induced angiogenesis. Materials and methods: To test this hypothesis, we targeted IKK beta in KRAS-mutant lung cancer cell lines either by siRNA-mediated transfection or by treatment with Compound A (CmpdA), a highly specific IKK beta inhibitor, and used in vitro and in vivo assays to evaluate angiogenesis. Results and conclusions: Both pharmacological and siRNA-mediated IKK beta targeting in lung cells reduced expression and secretion of NF-kappa B-regulated proangiogenic factors IL-8 and VEGF. Moreover, conditioned media from IKK beta-targeted lung cells reduced human umbilical vein endothelial cell (HUVEC) migration, invasion and tube formation in vitro. Furthermore, siRNA-mediated IKK beta inhibition reduced xenograft tumor growth and vascularity in vivo. Finally, IKK beta inhibition also affects endothelial cell function in a cancer-independent manner, as IKK beta inhibition reduced pathological retinal angiogenesis in a mouse model of oxygen-induced retinopathy. Taken together, these results provide a novel mechanistic understanding of how the IKK beta pathway affects human lung tumorigenesis, indicating that IKK beta promotes KRAS-induced angiogenesis both by cancer cell-intrinsic and cancer cell-independent mechanisms, which strongly suggests IKK beta inhibition as a promising antiangiogenic approach to be explored for KRAS-induced lung cancer therapy.