Genomic and genetic studies of endocrine cancers

背景内分泌恶性肿瘤(包括甲状腺、肾上腺、甲状旁腺和胰腺神经内分泌肿瘤)是美国增长最快的癌症诊断之一，但通过常规的临床、实验室和影像检查很难区分良、恶性肿瘤。因此，即使是看似良性的内分泌肿瘤患者，也往往选择接受手术以获得明确的诊断，希望排除癌症。大多数内分泌癌患者预后相对较好。然而，任何地方都有10%到40%(取决于肿瘤类型)患有侵袭性疾病，这在最初治疗时往往无法可靠地确定。预后标志物可以可靠地对复发和死亡风险较高的患者进行风险分层，这将有助于确定哪些患者应该接受积极的初始治疗和密切随访。此外，如果确定了不同的分子表型，预后标记物也可能有助于确定哪些患者可能对标准治疗有反应，哪些患者对标准治疗没有反应。我们在内分泌肿瘤的泛基因组分析(mRNA和microRNA表达、拷贝数变化和DNA甲基化)方面正在取得进展，以确定内分泌恶性肿瘤(甲状腺、肾上腺、神经内分泌胰腺)的候选诊断和预后标记物，并了解内分泌癌的异常基因/通路。从这些分析中，我们已经确定了一个在甲状腺癌进展中重要的miR-30a-LOX轴。我们发现miR-30a表达降低和LOX过度表达与更具侵袭性的分化甲状腺癌和较低的生存率显著相关(即使在低风险的传统乳头状甲状腺癌中也是如此)。我们的后续研究表明，miR-30a-LOX通过转录调控EMT转录因子SNAI2的表达和调节TIMP4的分泌来介导其在上皮向间充质转化(EMT)中的作用。基于这些发现，我们目前正在评估miR-30a-LOX-SNAI2轴作为分化型甲状腺癌预后标志物的作用。从我们对人类肾上腺皮质肿瘤全基因组基因表达和CpG甲基化状态的综合分析中，我们发现了在肾上腺皮质癌中高甲基化和下调表达的候选抑癌基因，这是肿瘤抑制基因沉默在癌症发生和发展中的常见机制。已确定的基因之一是RARRES2，这是一种先前被证明介导对癌症的免疫反应的基因。因为肾上腺皮质癌是相对非免疫原性的，我们假设RARRES2可能具有直接的肿瘤抑制功能。我们发现RARRES2在肾上腺皮质癌细胞系中抑制了体外和体内免疫低下小鼠模型的生长和侵袭。RARRES2在肾上腺皮质腺瘤和肾上腺癌中的表达也有显著差异，对区分这两种肿瘤的准确率较高。RARRES2的缺失在原发癌和转移性肾上腺皮质癌中都可以看到，这表明这是一个早期事件。为了了解RARRES2作为肿瘤抑制基因的作用机制，我们研究了它在肾上腺皮质癌常见的失调通路(WNT/β-catenin、TP53和IGF)中的作用。我们发现，RARRES2通过增加β-连环蛋白的磷酸化和降解来降低总的β-连环蛋白水平。除了上述有希望的肾上腺皮质癌标志物外，我们还分析和鉴定了区分肾上腺皮质癌和良性肾上腺皮质肿瘤的尿代谢物。

Background Endocrine malignancies (including thyroid, adrenal, parathyroid, and pancreatic neuroendocrine tumors) are among the fastest growing cancer diagnoses in the United States, but it is difficult to distinguish benign from malignant tumors by routine clinical, laboratory, and imaging studies. So, even patients who have seemingly benign endocrine tumors often choose to undergo surgery to get a definitive diagnosis in the hopes of ruling out cancer. Most patients with endocrine cancers have a relatively good prognosis. However, anywhere from 10% to 40% (depending on tumor type) have aggressive disease which often cannot be reliably determined at the time of initial treatment. Prognostic markers which can reliably risk stratify patients with high risk of recurrence and death would help determine which patients should receive aggressive initial treatment and close follow up. Furthermore, prognostic markers may also help identify which patients are likely to respond to standard therapy and which patients do not respond to standard therapy if a distinct molecular phenotype is identified. Summary We are making progress with our pan-genomic (mRNA and microRNA expression, copy number changes, and DNA-methylation) analysis of endocrine neoplasms to identify candidate diagnostic and prognostic markers for endocrine malignancies (thyroid, adrenal, neuroendocrine pancreas), and to understand the dysregulated genes/pathways in endocrine cancers. From these analyses, we have identified a miR-30a-LOX axis important in thyroid cancer progression. We found that reduced miR-30a expression and LOX overexpression are significantly associated with more aggressive differentiated thyroid cancer and lower survival rates (even in low-risk conventional papillary thyroid cancer). Our follow up studies have shown that miR-30a-LOX mediates its effect on epithelial-to-mesenchymal transition (EMT) through transcriptionally regulating SNAI2 expression, an EMT transcription factor, and by regulating TIMP4 secretion. Based on these findings, we are currently evaluating the miR-30a-LOX-SNAI2 axis as a prognostic marker in differentiated thyroid cancer. From our integrated analysis of genome-wide gene expression and CpG methylation status in human adrenocortical tumors, we identified candidate tumor suppressor genes that were hypermethylated and downregulated in adrenocortical carcinoma, a common mechanism of tumor suppressor gene silencing in cancer initiation and progression. One of the genes identified is RARRES2, a gene previously shown to mediate an immune response to cancer. Because adrenocortical carcinomas are relatively non-immunogenic, we hypothesized that RARRES2 may have a direct tumor suppressive function. We found that RARRES2 in adrenocortical carcinoma cell lines inhibited growth and invasion in vitro and in vivo in immunocompromised mouse models. RARRES2 was also significantly differentially expressed between adrenal cortical adenoma and carcinoma, and distinguished these tumors with high accuracy. Loss of RARRES2 was seen in both primary and metastatic adrenocortical carcinoma suggesting it is an early event. To understand the mechanism by which RARRES2 functions as a tumor suppressor gene, we investigated its effect on common dysregulated pathways in adrenocortical carcinoma (WNT/beta-catenin, TP53, and IGF). We found that RARRES2 reduced total beta-catenin levels by increasing the phosphorylation and degradation of beta-catenin. In addition to the above promising markers of adrenocortical carcinoma, we have also analyzed and identified urinary metabolites that distinguish between adrenocortical carcinoma and benign adrenocortical tumors.