Impact of heme catabolism on triple negative breast cancer metastasis via immune-suppression

摘要/项目摘要 三阴性乳腺癌（TNBC）比其他乳腺癌具有更频繁和快速的转移 (BC)亚型和>20%的患者在诊断后5年内在标准护理治疗中进展。 早期侵袭力的增加可能是上皮细胞向间质细胞转化（EMT）的结果， TNBC已经部分地经历了增加细胞运动性、诱导化疗抗性和促进细胞增殖的过程。 免疫逃避使用micro-RNA miR-200 c抑制EMT显示了几种免疫抑制性细胞因子。 与上皮细胞相比，间充质样BC中的分解代谢酶增加 对应物，例如HMOX 1（血红素加氧酶-1，HO-1）。有趣的是，HO-1在许多细胞类型中表达， 先前的研究表明，靶向免疫细胞中的HO-1可以限制肿瘤微环境， 临床前模型的进展。然而，关于乳腺肿瘤细胞的作用， HO-1及其催化剂在肿瘤转移、化疗耐药和免疫逃避中的作用 我的初步数据显示，HO-1表达在两个TNBC样肺转移瘤中增加， 乳腺肿瘤模型与其各自的原发性肿瘤相比。在另一个自发的 肺转移模型中HO-1的表达也增加。以前的研究和我 初步结果还显示化疗诱导HO-1表达。考虑到HO-1的重要作用， 在乳腺肿瘤进展中，进一步研究HO-1在转移过程中TNBC细胞中的作用是至关重要的， 化疗耐药性，我将在目标1中研究。用临床批准的HO抑制剂靶向HO-1将 也可以探索并与肿瘤细胞特异性HO-1抑制（shRNA）在临床相关的，免疫- 胜任的TNBC样小鼠模型。 HO-1降解血红素，产生抑制旁分泌中正常免疫细胞功能的catalysts 方式一种这样的分解代谢物胆红素（BR）在其他疾病中具有强大的免疫抑制作用，但具有 尚未在癌症中作为免疫抑制剂进行研究。我的初步数据进一步表明，BR是 表明BR处理通过限制表达改变了巨噬细胞的功能 M1极化基因和停止巨噬细胞吞噬死细胞。以前的研究 显示BC患者化疗后血清BR水平升高。因此必须 了解乳腺肿瘤进展过程中HO-1表达升高是否可以增强肿瘤源性 胆红素反过来又限制了免疫细胞的功能。这个想法将在目标2中评估，我将研究 胆红素对肿瘤免疫抑制影响总之，本文提出的目标将决定HO-1是否是 一种新的临床靶点，以限制转移和重新激活抗肿瘤免疫反应， 依赖的方式。这些研究可以揭示新的治疗策略，有可能提高 目前的TNBC疗法，如化疗和检查点阻断的疗效。

Abstract/Project Summary Triple negative breast cancer (TNBC) has more frequent and rapid metastasis than other breast cancer (BC) subtypes and >20% of patients progress on standard of care therapies within 5 years of diagnosis. Increased early invasiveness could be a result of epithelial to mesenchymal transition (EMT), which many TNBCs have partially undergone to increase cell motility, induce chemotherapy resistance, and promote immune evasion. Reversal of EMT using the micro-RNA miR-200c revealed several immune-suppressive catabolizing enzymes that are increased in mesenchymal-like BCs when compared to more epithelial counterparts, such as HMOX1 (heme oxygenase-1, HO-1). Interestingly, HO-1 is expressed in many cell types in the tumor microenvironment and previous studies show that targeting HO-1 in immune cells can limit tumor progression in preclinical models. However, there is a gap in knowledge regarding the role of breast tumor cell- HO-1 and its catabolites in metastasis, chemotherapy resistance, and immune evasion. My preliminary data showed that HO-1 expression was increased in lung metastases from two TNBC-like mammary tumor models when compared to their respective primary tumors. In an additional spontaneous metastasis model, HO-1 expression was also increased in lung metastases. Previous studies and my preliminary results also show that chemotherapy induces HO-1 expression. Given the important role HO-1 may have in breast tumor progression, it is critical to further investigate HO-1 in TNBC cells during metastasis and chemotherapy resistance, which I will study in Aim 1. HO-1 targeting with a clinically approved HO inhibitor will also be explored and compared to tumor cell specific HO-1 inhibition (shRNA) in clinically relevant, immune- competent TNBC-like mouse models. HO-1 degrades heme to produce catabolites that suppress normal immune cell function in a paracrine manner. One such catabolite bilirubin (BR) has powerful immune-suppressive roles in other diseases, but has not been explored in cancers as an immunosuppressant. My preliminary data further demonstrate that BR is immune-modulatory and showed that BR treatment altered the function of macrophages by limiting expression of M1 polarization genes and by halting efferocytosis, macrophage engulfment of dead cells. Previous studies show that serum BR levels increase after chemotherapy treatment in BC patients. Therefore, it is essential to understand whether elevated HO-1 expression during breast tumor progression can enhance tumor-derived bilirubin that in turn limits immune cell function. This idea will be assessed in Aim 2 where I will study the impact of bilirubin on tumor immune-suppression. Together, the aims proposed herein will determine if HO-1 is a novel clinical target to limit metastasis and reactivate the anti-tumor immune response in a non-contact dependent manner. These studies could reveal new treatment strategies with the potential to enhance the efficacy of current TNBC therapies such as chemotherapy and checkpoint blockade.