The University of Michigan Medical School, Department of Radiation Oncology, Ann Arbor, MI 48109-0010, USA.
Transl Oncol. 2008 Dec;1(4):195-201. doi: 10.1593/tlo.08151.
Angiogenesis plays an important role in pancreas cancer pathobiology. Pancreatic tumor cells secrete vascular endothelial growth factor (VEGF), activating endothelial cell protein kinase C beta (PKCbeta) that phosphorylates GSK3beta to suppress apoptosis and promote endothelial cell proliferation and microvessel formation. We used Enzastaurin (Enz) to test the hypothesis that inhibition of PKCbeta results in radiosensitization of endothelial cells in culture and in vivo.
MATERIALS/METHODS: We measured PKCbeta phosphorylation, VEGF pathway signaling, colony formation, and capillary sprout formation in primary human dermal microvessel endothelial cells (HDMECs) after Enz or radiation (RT) treatment. Microvessel density and tumor volume of human pancreatic cancer xenografts in nude mice were measured after treatment with Enz, RT, or both.
Enz inhibited PKCbeta and radiosensitized HDMEC with an enhancement ratio of 1.31 +/- 0.05. Enz combined with RT reduced HDMEC capillary sprouting to a greater extent than either agent alone. Enz prevented radiation-induced GSK3beta phosphorylation of serine 9 while having no direct effect on VEGFR phosphorylation. Treatment of xenografts with Enz and radiation produced greater reductions in microvessel density than either treatment alone. The reduction in microvessel density corresponded with increased tumor growth delay.
Enz-induced PKCbeta inhibition radiosensitizes human endothelial cells and enhances the antiangiogenic effects of RT. The combination of Enz and RT reduced microvessel density and resulted in increased growth delay in pancreatic cancer xenografts, without increase in toxicity. These results provide the rationale for combining PKCbeta inhibition with radiation and further investigating such regimens in pancreatic cancer.
血管生成在胰腺癌病理生物学中起着重要作用。胰腺肿瘤细胞分泌血管内皮生长因子（VEGF），激活内皮细胞蛋白激酶 Cβ（PKCβ），使 GSK3β磷酸化，抑制细胞凋亡，促进内皮细胞增殖和微血管形成。我们使用恩扎妥滨（Enz）来验证抑制 PKCβ可导致培养的和体内的内皮细胞放射敏化的假设。
材料/方法：我们在原代人真皮微血管内皮细胞（HDMEC）中测量了 Enz 或辐射（RT）处理后 PKCβ磷酸化、VEGF 通路信号传导、集落形成和毛细血管芽形成。用 Enz、RT 或两者联合处理裸鼠人胰腺癌细胞异种移植瘤后，测量微血管密度和肿瘤体积。
Enz 抑制了 PKCβ，并使 HDMEC 的放射增敏作用增强，增强比为 1.31±0.05。Enz 联合 RT 降低 HDMEC 毛细血管芽形成的程度大于任一单一药物。Enz 可防止辐射诱导的 GSK3β丝氨酸 9 磷酸化，而对 VEGFR 磷酸化没有直接影响。用 Enz 和 RT 处理异种移植瘤可导致微血管密度降低幅度大于任一单一药物。微血管密度的降低与肿瘤生长延迟增加相对应。
Enz 诱导的 PKCβ抑制可放射增敏人内皮细胞，并增强 RT 的抗血管生成作用。Enz 和 RT 的联合治疗降低了微血管密度，并导致胰腺癌细胞异种移植瘤生长延迟增加，而毒性没有增加。这些结果为 PKCβ抑制与放疗联合提供了依据，并进一步研究了在胰腺癌中的这种方案。
