Discerning the role of semaphorin 7a in mammary tumor growth and anti-tumor immunity

项目摘要/摘要 乳腺癌的早期发现和治疗减少了乳腺癌相关死亡的数量，但仍是15-54岁女性癌症相关死亡的主要原因。在40岁以上的女性中，超过一半的BCS符合产后乳腺癌(PPBC)的定义，即在最后一次分娩后10年内诊断出的BCS，与未分娩患者诊断的BCS相比，转移的可能性高2-3倍。这些死亡通常归因于肿瘤细胞通过血管和淋巴管扩散到远处组织。淋巴管密度(LVD)、淋巴管侵袭和淋巴结阳性(LN+)常见于PPBC，且与预后不良相关。我们已经确定信号素7a(SEMA7A)-一种在癌症中激活整合素-131信号的信号分子-在PPBC中上调，并与LVD、TAMS和转移的增加有关。此外，SEMA7A+肿瘤概括了PPBC中观察到的加速肿瘤发生和转移的特征，高SEMA7A表达与总体存活率下降相关。因此，PPBC可能只代表SEMA7A+癌症的一部分；目前还没有针对SEMA7A的治疗方法。SEMA7A+BCS例证了癌症的四个关键特征：1)抵抗细胞死亡，2)血管生成和淋巴管生成，3)免疫逃避，4)侵袭和转移。肿瘤相关巨噬细胞(TAM)参与了每一种肿瘤的形成，并创造了一个有利于肿瘤的微环境(TME)。由于TAMs和LVD在SEMA7A+BC中扩增，可能与PPBC的预后不良有关。SEMA7A还可以将巨噬细胞极化成TAMs的一个子集(称为“POEMS”)，表达淋巴相关蛋白。这些POEMS嵌入淋巴管形成POEM-LEC嵌合血管，肿瘤细胞在POEM-LEC连接处与这些血管相关联，可能介导肿瘤细胞的逃逸。此外，SEMA7A还可以促进BC细胞、LECs、TAMs和POEMS上PD-L 1的表达，从而抑制抗肿瘤免疫；然而，SEMA7A对TME免疫细胞的额外作用尚未被研究。综上所述，这导致了我们的假设，即SEMA7A激活了免疫抑制POSE中的促生存信号，以促进肿瘤细胞的扩散。 这项建议的目标是：1)确定SEMA7A诱导细胞存活并将免疫TME改变为亲肿瘤状态的机制；2)研究POEMS产生的趋化物质，将肿瘤细胞招募到POEM-LEC连接并促进转移。在目标1中，我们将确定SEMA7A诱导细胞存活的机制以及对TME免疫细胞的影响。我们还将确定单抗诱导的SEMA7A抑制是否会阻碍肿瘤生长和免疫抑制。在目标2中，我们将定义将肿瘤细胞招募到POEM-LEC连接的化学诱导剂。这些研究的结果将确定SEMA7A如何促进肿瘤进展、免疫抑制和淋巴转移，并为未来针对SEMA7A+BCS的治疗提供洞察力，从而提高许多BC患者的生存率。

Project Summary/Abstract Early detection and treatment of breast cancer (BC) has reduced the number of BC-related deaths but remains the leading cause of cancer-related death in women ages 15-54. Over half of all BCs diagnosed in women <40 years of age fit the definition of postpartum breast cancer (PPBC), BCs diagnosed within 10 years of last childbirth, which are 2-3 times more likely to metastasize compared to BCs diagnosed in nulliparous patients. These deaths are generally attributed to dissemination of tumor cells to distant tissues via blood and lymphatic vessels. Increased lymphatic vessel density (LVD), lymphovascular invasion, and lymph node positivity (LN+) are frequently observed in PPBC and are associated with worse prognosis. We have identified that semaphorin 7a (SEMA7A)-a signaling molecule that activates integrin-131 signaling in cancer-is upregulated in PPBC and is associated with increased LVD, TAMs, and metastasis. Additionally, SEMA7A+ tumors recapitulate the accelerated tumorigenesis and metastatic profiles observed in PPBC and high SEMA7A expression correlates with decreased overall survival. As such, PPBCs likely only represent a subset of SEMA7A+ cancers; there are currently no therapies targeting SEMA7A. SEMA7A+ BCs exemplify four key hallmarks of cancer: 1) resistance to cell death, 2) angiogenesis and lymphangiogenesis, 3) immune evasion, and 4) invasion and metastasis. Tumor-associated macrophages (TAMs) are implicated in each and in creating a pro-tumor microenvironment (TME). As TAMs and LVD are amplified in SEMA7A+ BC, it is probable that they contribute to the worse prognosis of PPBC. SEMA7A can also polarize macrophages into a subset of TAMs (termed "PoEMs") that express lymphatic-associated proteins. These PoEMs intercalate into lymphatic vessels to form PoEM-LEC chimeric vessels and tumor cells associate with these vessels at PoEM-LEC junctions, which may mediate tumor cell escape. Moreover, SEMA7A can promote expression of PD-L 1-expression on BC cells, LECs, TAMs, and PoEMs to suppress anti-tumor immunity; however, additional effects of SEMA7A on immune cells of the TME have not been investigated. Altogether, this led us to the hypothesis that SEMA7A activates pro-survival signaling in immunosuppressive PoEMs to promote tumor cell dissemination. The goals of this proposal are to: 1) determine the mechanisms by which SEMA7A induces cell survival and alters the immune TME to a pro-tumor state, and 2) investigate the chemoattractants produced by PoEMs that recruit tumor cells to PoEM-LEC junctions and promote metastasis. In aim 1, we will define the mechanisms of SEMA7A-induced cell survival and effects on immune cells of the TME. We will also establish whether monoclonal antibody-induced inhibition of SEMA7A impedes tumor growth and immune suppression. In aim 2, we will define chemoattractants that recruit tumor cells to PoEM-LEC junctions. The results of these studies will identify how SEMA7A promotes tumor progression, immunosuppression, and lymphatic-meditated metastasis, as well as offer insight for future therapies to target SEMA7A+ BCs, thus improving survival for many BC patients.