Macrophage migration inhibitory factor downregulation: a novel mechanism of resistance to anti-angiogenic therapy.
Macrophage migration inhibitory factor downregulation: a novel mechanism of resistance to anti-angiogenic therapy.
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作者：
Castro BA;Flanigan P;Jahangiri A;Hoffman D;Chen W;Kuang R;De Lay M;Yagnik G;Wagner JR;Mascharak S;Sidorov M;Shrivastav S;Kohanbash G;Okada H;Aghi MK
抗血管生成治疗癌症，如VEGF中和抗体贝伐单抗的持久性有限。虽然耐药机制尚不明确，但对抗血管生成治疗的获得性耐药可能涉及肿瘤微环境的改变。我们证实，在贝伐单抗耐药胶质母细胞瘤患者标本和两种新型贝伐单抗耐药胶质母细胞瘤异种移植模型中，肿瘤相关巨噬细胞增加。微阵列分析表明，下调巨噬细胞迁移抑制因子（MIF）是巨噬细胞增加的最相关介质。贝伐单抗耐药患者胶质母细胞瘤和两种新型异种移植耐药模型的MIF均低于贝伐单抗初治肿瘤，并且含有更多特异性定位于肿瘤边缘的M2/原肿瘤巨噬细胞。表达MIF- shrna的异种移植物生长更快，血管生成更大，巨噬细胞定位到肿瘤边缘更普遍，更增殖，并表现出M2极化，而贝伐单抗耐药的MIF上调的异种移植物则表现出相反的变化。骨髓来源的巨噬细胞在贝伐单抗耐药异种移植物来源细胞的条件培养基中极化为M2表型，而重组MIF驱动M1极化。与暴露于贝伐珠单抗应答性肿瘤细胞培养基的巨噬细胞培养基相比，暴露于贝伐珠单抗耐药肿瘤细胞条件培养基的巨噬细胞培养基增加了胶质瘤细胞的增殖，这表明贝伐珠单抗耐药异种移植物中的巨噬细胞极化是其侵袭性生物学的来源，是一种分泌因子的结果。贝伐单抗诱导MIF减少的两种机制被确定：(1)贝伐单抗结合MIF并阻断MIF诱导的巨噬细胞M1极化；(2) VEGF以vegfr2依赖的方式增加胶质瘤MIF的产生，表明贝伐单抗诱导的VEGF耗竭会下调MIF。定点活检显示，在贝伐单抗初始患者中，MIF和VEGF在增强边缘富集。这种MIF富集在贝伐单抗耐药胶质母细胞瘤中消失，驱动肿瘤边缘m1到m2的转变。因此，贝伐单抗耐药是由肿瘤边缘的MIF减少导致M2巨噬细胞增殖扩张驱动的，而M2巨噬细胞增殖扩张反过来促进肿瘤生长。
Anti-angiogenic therapies for cancer such as VEGF neutralizing antibody bevacizumab have limited durability. While mechanisms of resistance remain undefined, it is likely that acquired resistance to anti-angiogenic therapy will involve alterations of the tumor microenvironment. We confirmed increased tumor-associated macrophages in bevacizumab-resistant glioblastoma patient specimens and two novel glioblastoma xenograft models of bevacizumab resistance. Microarray analysis suggested downregulated macrophage migration inhibitory factor (MIF) to be the most pertinent mediator of increased macrophages. Bevacizumab-resistant patient glioblastomas and both novel xenograft models of resistance had less MIF than bevacizumab-naive tumors, and harbored more M2/protumoral macrophages that specifically localized to the tumor edge. Xenografts expressing MIF-shRNA grew more rapidly with greater angiogenesis and had macrophages localizing to the tumor edge which were more prevalent and proliferative, and displayed M2 polarization, whereas bevacizumab-resistant xenografts transduced to upregulate MIF exhibited the opposite changes. Bone marrow-derived macrophage were polarized to an M2 phenotype in the presence of condition-media derived from bevacizumab-resistant xenograft-derived cells, while recombinant MIF drove M1 polarization. Media from macrophages exposed to bevacizumab-resistant tumor cell conditioned media increased glioma cell proliferation compared with media from macrophages exposed to bevacizumab-responsive tumor cell media, suggesting that macrophage polarization in bevacizumab-resistant xenografts is the source of their aggressive biology and results from a secreted factor. Two mechanisms of bevacizumab-induced MIF reduction were identified: (1) bevacizumab bound MIF and blocked MIF-induced M1 polarization of macrophages; and (2) VEGF increased glioma MIF production in a VEGFR2-dependent manner, suggesting that bevacizumab-induced VEGF depletion would downregulate MIF. Site-directed biopsies revealed enriched MIF and VEGF at the enhancing edge in bevacizumab-naive patients. This MIF enrichment was lost in bevacizumab-resistant glioblastomas, driving a tumor edge M1-to-M2 transition. Thus, bevacizumab resistance is driven by reduced MIF at the tumor edge causing proliferative expansion of M2 macrophages, which in turn promotes tumor growth.