Molecular causes and mechanistic underpinning of breast cancer racial disparity

 描述(申请人提供)：与高加索(CA)女性相比，非裔美国人(AA)女性更有可能患有侵袭性乳腺癌(BC)，并经历更高的死亡率。另一个令人不安的事实是，这一癌症结果差距在过去几年中继续扩大，突显了在这一领域取得进展的迫切需要。人们越来越认识到，肿瘤微环境(TME)可能在卑诗省的种族差异中起着重要作用，但其潜在的分子和机制基础尚不清楚。这个项目是建立在我们的新发现基础上的，该发现表明存在TME-肿瘤细胞相互作用驱动的调节环路，该环路在AA患者中主要活跃。我们发现：1)AA-BC患者血清中炎症细胞因子--抵抗素和IL-6水平显著高于CA-BC患者，2)AA-BC患者STAT3的表达和磷酸化水平显著高于CA-BC患者，3)抵抗素处理AA和CA患者的三阴性乳腺癌(TNBC)细胞株可促进STAT3/pSTAT3的表达和IL-6的产生，从而提示不同的TME在整个疾病转归中起主导作用。4)IL-6介导抵抗素对STAT3的磷酸化的影响，5)抵抗素促进BC细胞侵袭性肿瘤表型和治疗耐药，6)抵抗素还上调Lin28a，6)Resistn还上调Lin28a。茎的调节，并下调let-7miRNA，和7)Lin28a沉默取消抵抗素诱导的IL6，pSTAT3和STAT3的上调。基于这些发现，我们假设肿瘤生物学上的内在差异是导致BC细胞种族差异的原因，而抵抗素-Lin28a-(IL6)-STAT3/pSTAT3是控制BC细胞侵袭性和治疗耐药表型的重要调控环。这一假设将在三个具体目标上得到检验。在目标1中，我们将通过研究抵抗素诱导的Lin28a表达的调控途径，以及Lin28a是否介导抵抗素诱导的let-7下调，从而导致BC细胞中STAT3和IL6的上调，来表征Resistn-Lin28a-(IL6)-STAT3/pSTAT3调控环的分子机制。在目标2中，我们将通过使用荧光素酶标记的对照或Lin28a-/STAT3沉默的BC细胞来研究这种调控的功能意义，并在裸鼠原位模型中表征抵抗素及其下游效应对生长、转移和治疗耐药的反应。在目标3中，我们将通过检测抵抗素-Lin28a-(IL6)-STAT3/pSTAT3调节环组分在临床样本中的表达，并评估它们与TME和肿瘤细胞特征的相关性，以及与种族和患者生存的相关性，来确定抵抗素-Lin28a-(IL6)-STAT3/pSTAT3调控环组件在BC种族差异中的临床相关性。总之，这些研究将为BC种族差异的分子原因和机制基础提供新的见解，并提供一组新的生物标记物和潜在的药物靶点，以开发新的方法来缩小AA和CA BC患者日益扩大的临床结果差距。

 DESCRIPTION (provided by applicant): African American (AA) women are more likely to have aggressive breast cancer (BC) and experience greater mortality rates as compared to Caucasian (CA) women. Another upsetting fact is that this cancer outcome gap has continued to widen over past several years underscoring the immediate need to make progress in this area. It is being increasingly appreciated that tumor microenvironment (TME) may play an important role in BC racial disparity; however, underlying molecular and mechanistic basis is not clearly understood. This project is built upon our novel findings suggesting the existence of a TME-tumor cell interaction-driven regulatory loop, which is predominantly active in AA patients. We demonstrate that 1) serum levels of inflammatory cytokines, resistin and IL6, are significantly elevated in AA BC patients compared to their CA counterparts, 2) AA BCs have significantly greater expression and phosphorylation of STAT3 compared to CA BCs, 3) treatment of triple-negative breast cancer (TNBC) cell lines from both AA and CA patients with resistin promotes expression of STAT3/pSTAT3 and enhances IL6 production, thus suggesting a dominant role of differential TME in overall disease outcome, 4) IL6 mediates the effect of resistin on STAT3 phosphorylation, 5) resistin promotes aggressive tumor phenotypes and therapy-resistance in BC cells through STAT3 induction, 6) resistin also upregulates LIN28A, a regulator of stemness, and downregulates let-7 miRNA, and 7) LIN28A silencing abrogates resistin-induced upregulation of IL6, pSTAT3 and STAT3. Based on these findings, we hypothesize that intrinsic differences in tumor biology contributes to BC racial disparity and resistin-LIN28A-(IL6)- STAT3/pSTAT3 serves as an important regulatory loop controlling the aggressive and therapy-resistant phenotypes of BC cells. This hypothesis will be tested in three specific aims. In aim 1, we will characterize the molecular mechanisms underlying resistin-LIN28A-(IL6)-STAT3/pSTAT3 regulatory loop by examining the pathways regulating resistin-induced LIN28A expression, and whether LIN28A mediates resistin-induced let-7 downregulation, which then leads to STAT3 and IL6 upregulation in BC cells. In aim 2, we will examine the functional significance of this regulatory by using luciferase-tagged, control or LIN28A-/STAT3-silenced BC cell lines and characterize the response of resistin and its downstream effectors on growth, metastasis and therapy-resistance in an orthotopic nude mice model. In aim 3, we will determine the clinical relevance of the components of resistin-LIN28A-(IL6)-STAT3/pSTAT3 regulatory loop in BC racial disparity by examining their expression in clinical samples and assessing their correlation (alone and in combination) with TME and tumor cell characteristics as well as with race and patient's survival. Together, these studies will provide novel insight into molecular causes and mechanistic underpinning of BC racial disparity and provide novel set of biomarkers and potential drug-targets to develop novel ways for reducing the widening gaps in clinical outcome of AA and CA BC patients.