Defining the role of macropinocytosis in solid tumor growth and therapeutic resistance

摘要 癌细胞需要源源不断的营养物质来支持癌基因驱动的生长。但血 供应这些营养物质的血管通常是曲折和渗漏的。结缔组织增生也可导致 间质压力使肿瘤血管塌陷，进一步损害营养输送。癌细胞 通过从微环境中清除大分子来克服这些供应方面的限制。一 肿瘤所采用的清除策略是巨胞饮作用，这是一种细胞外物质非- 特别是吞噬，然后在溶酶体中降解产生营养物质。RAS中的致癌突变， PI 3 K途径的激活以及EGFR和WNT信号传导驱动胰腺，前列腺， 肺癌、结肠癌、膀胱癌和乳腺癌细胞系。当提供巨胞饮细胞燃料时，这些癌细胞 能够在营养有限的条件下繁殖。但目前尚不清楚数量和 存在于肿瘤微环境中的物质的质量足以使巨胞饮作用产生 对肿瘤抑制有显著贡献。所有已发表的研究都依赖于EIPA进行体内研究 巨胞饮抑制EIPA是Na+/H+交换剂的抑制剂，具有多效性抗肿瘤作用。 独立于巨胞饮抑制的作用。目前缺乏的是一种有选择地扰乱 体内巨胞饮作用。因此，不可能准确地界定 因此，本发明的方法可用于预测巨胞饮对肿瘤生长的影响或靶向该途径的潜在治疗价值。鉴于 通过自噬的营养再循环在肿瘤进展和治疗抗性中起主要作用， 通过巨胞饮作用清除营养物质可能也会起到同样重要的作用。目标1 该提案将评估选择性巨胞饮抑制限制肿瘤生长的程度。目标2将 评估巨胞饮作用在治疗抵抗中的作用。目标3将剖析促进 肿瘤细胞中的巨胞饮体形成。完成这些研究将填补我们知识的主要空白， 可能导致新的单一药物和/或联合治疗癌症。因为一些最难做到的 治疗癌症是巨胞饮细胞性的（例如胰腺、KRAS+结肠直肠、三阴性乳腺和去势- 耐药前列腺癌），这些研究有可能对患者生存产生重大影响。

ABSTRACT Cancer cells require a steady stream of nutrients to support their oncogene-driven growth. However, the blood vessels that supply these nutrients are often tortuous and leaky. Desmoplasia can also lead to elevated interstitial pressure that collapses tumor blood vessels, further compromising nutrient delivery. Cancer cells overcome these supply-side limitations by scavenging macromolecules from the microenvironment. One scavenging strategy employed by tumors is macropinocytosis, a process by which extracellular material is non- specifically engulfed and then degraded in the lysosome to produce nutrients. Oncogenic mutations in RAS, activation of the PI3K pathway, and EGFR and WNT signaling drive macropinocytosis in pancreatic, prostate, lung, colon, bladder, and breast cancer cell lines. When provided with macropinocytic fuel, these cancer cells are able to proliferate in nutrient-limiting conditions. However, is not currently clear whether the quantity and quality of material present in the tumor microenvironment is sufficient for macropinocytosis to make a significant contribution to tumor anabolism. All published studies have depended upon EIPA for in vivo macropinocytosis inhibition. EIPA is an inhibitor of Na+/H+ exchangers that has pleiotropic anti-neoplastic effects independent of macropinocytosis inhibition. What is currently lacking is a strategy to selectively disrupt macropinocytosis in vivo. As a result, it has not been possible to accurately define the contribution of macropinocytosis to tumor growth or the potential therapeutic value of targeting this pathway. Given that nutrient recycling via autophagy plays a major role in both tumor progression and therapeutic resistance, it is likely that nutrient scavenging through macropinocytosis will play a similarly important role. Aim 1 of this proposal will assess the extent to which selective macropinocytosis inhibition limits tumor growth. Aim 2 will evaluate the role of macropinocytosis in therapeutic resistance. Aim 3 will dissect the signals that promote macropinosome formation in tumor cells. Completing these studies will fill major gaps in our knowledge and could lead to new single-agent and/or combination therapies for cancer. Because some of the most difficult to treat cancers are macropinocytic (e.g. pancreas, KRAS+ colorectal, triple-negative breast, and castration- resistant prostate cancers), these studies have the potential to make a significant impact on patient survival.