Functional Study of Mucin MUC1

描述（由申请人提供）：MUC 1是一种肿瘤相关抗原，参与肿瘤发生、细胞信号传导调节和上皮表面转录及保护。除了在上皮细胞上广泛表达外，MUC 1也在造血细胞上发现;然而，MUC 1在这些细胞中的功能仍然相当未知。我们发现，与野生型（WT）C57 BL/6小鼠相比，C57 BL/6 Muc 1-/-（KO）小鼠的原代髓系祖细胞中Muc 1的缺乏导致GM-CSF和IL-4信号转导下CD 11b + Gr 1+细胞扩增增加。从KO骨髓中体外扩增的CD 11b + Gr 1+细胞在体外抑制T细胞增殖，而来自WT的那些则没有，这表明这些KO CD 11b + Gr 1+细胞是髓源性抑制细胞（MDSC）。MDSC有助于癌症中常见的免疫抑制;然而，它们从骨髓祖细胞分化的机制仍然相对未知。最有趣的是，Mu 1 KO小鼠能够更好地耐受同种异体肿瘤生长，血液和肿瘤引流淋巴结中CD 11b + Gr 1+细胞积聚。CD 11b + Gr 1 + MDSCs从KO骨髓中扩增伴随着β-catenin下调，抑制β-catenin下调可逆转CD 11b + Gr 1 + MDSCs的扩增。我们的研究结果表明，需要Muc 1调节髓系祖细胞分化为CD 11b + Gr 1 + MDSC。我们假设MUC 1在MDSC分化中起着关键的信号转导作用，以响应稳态干扰。为了进一步表征Muc 1在调节MDSC分化中的机制和功能作用，我们提出了以下具体目标：（1）确定Muc 1调节髓系祖细胞分化为CD 11b + Gr 1 + MDSC的机制，（2）为了确定在肿瘤中产生的MDSC的功能意义，通过表征产生的MDSC群体以及它们从骨髓发育并在外周中积累的过程，（3）通过使用在造血或非造血区室中缺乏或具有Muc 1的嵌合小鼠来确定Muc 1的缺乏在葡聚糖硫酸钠（DSS）诱导的结肠炎和结肠炎相关癌症（CAC）期间在骨髓发育中的影响。MUC 1是一个特别有吸引力的抗癌药物的发展目标，这将被设计为靶向MUC 1的癌，但也可能影响造血细胞表达MUC 1和我们的研究将是有用的，在继续定义MUC 1在造血中的作用。与此同时，进一步了解MDSC分化中涉及的信号通路（MUC 1调节或其他）将使药物更容易靶向癌症和炎症中的这些通路。这些研究的结果应该让我们更清楚地了解MUC 1在上皮和造血系统中在炎症和癌症信号通路中的作用。 公共卫生相关性：在这项提案中，我们将研究MUC 1的功能，一种细胞相关的信号粘蛋白，在成熟和扩增的细胞群（髓源性抑制细胞，MDSC），可以抑制免疫系统。尽管MUC 1在上皮组织中被公认为是一种致癌基因，但它在造血组织中似乎具有不同的作用。这项研究将为炎症和肿瘤中的免疫抑制微环境提供新的机制和功能见解。进一步了解MDSC分化中涉及的信号通路以及增加对MUC 1在炎症和癌症中上皮和造血系统中的作用的了解将使我们能够更有知识地靶向治疗。

DESCRIPTION (provided by applicant): MUC1 is a tumor-associated antigen involved in oncogenesis, regulation of cellular signaling and transcription and protection of epithelial surfaces. In addition to the widespread expression on epithelia, MUC1 is also found on hematopoietic cells; however, the function of MUC1 in these cells is still fairly unknown. We have found that the lack of Muc1 in primary myeloid progenitors from the C57BL/6 Muc1-/- (KO) mice resulted in an increased expansion of CD11b+Gr1+ cells under GM-CSF and IL-4 signaling, as compared to the wild type (WT) C57BL/6 mice. The CD11b+Gr1+ cells that were expanded in vitro from the KO bone marrow suppressed T cell proliferation in vitro while those from the WT did not, suggesting that these KO CD11b+Gr1+ cells were myeloid derived suppressor cells (MDSCs). MDSCs contribute to the immune suppression frequently seen in cancer; however, the mechanism by which they differentiate from myeloid progenitors is still relatively unknown. Most intriguingly, Muc1 KO mice were able to better tolerate allogeneic tumor growth, with an accumulation of CD11b+Gr1+ cells in the blood and tumor draining lymph nodes. The expansion of CD11b+Gr1+ MDSCs from KO bone marrow was accompanied by beta-catenin down regulation, and inhibition of beta-catenin down regulation could reverse the expansion of CD11b+Gr1+ MDSCs. Our findings indicate a need for Muc1 in modulating the differentiation of myeloid progenitors into CD11b+Gr1+ MDSCs. We hypothesize that MUC1 plays a critical role as a signal transducer in MDSC differentiation in response to a steady state disturbance. To further characterize the mechanistic and functional role of Muc1 in regulating MDSC differentiation, we propose the following specific aims: (1) To determine the mechanism by which Muc1 regulates the differentiation of myeloid progenitors into CD11b+Gr1+ MDSCs, (2) To determine functional significance of MDSCs generated in tumor-bearing Muc1 KO mice by characterizing MDSC populations generated as well as the process by which they develop from the bone marrow and accumulate in the periphery, (3) To determine the effect of a lack of Muc1 in myeloid development during dextran sodium sulfate (DSS)-induced colitis and colitis associated cancer (CAC) by using chimeric mice that lack or have Muc1 in the hematopoietic or non hematopoietic compartment. MUC1 is an especially attractive target for the development of anti-cancer agents, which would be designed to target MUC1 on carcinomas, but could also affect the hematopoietic cells expressing MUC1 and our studies would be useful in continuing to define the role of MUC1 in hematopoiesis. At the same time, furthering our understanding of the signaling pathways involved in MDSC differentiation (MUC1 regulated or otherwise) would enable the targeting of these pathways by drugs in cancer and inflammation more readily. Results from these studies should give us clearer insight into the role of MUC1 in the epithelium and hematopoietic system in both inflammation and cancer signaling pathways. PUBLIC HEALTH RELEVANCE: In this proposal we will study the function of MUC1, a cell-associated signaling mucin, in the maturation and expansion of a cell population (myeloid derived suppressor cells, MDSCs) that can suppress the immune system. Although MUC1 is well established as an oncogene in epithelial tissues, it appears to have different roles in hematopoietic tissues. This study will provide novel mechanistic and functional insights into the immunosuppressive microenvironment that can be found in inflammation and tumors. Further understanding of the signaling pathways involved in MDSC differentiation as well as increased insight into the role of MUC1 in the epithelium and hematopoietic systems in inflammation and cancer will enable us to target therapies more knowledgeably.