Genomic and genetic studies of endocrine cancers

在美国，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）是增长最快的癌症诊断之一，但通过常规临床、实验室和影像学检查很难区分良性和恶性肿瘤。因此，即使是看似良性的内分泌肿瘤患者，也经常选择接受手术来获得明确的诊断，希望能排除癌症。大多数内分泌癌患者预后较好。然而，10%至40%（取决于肿瘤类型）的肿瘤具有侵袭性，在最初治疗时往往无法可靠地确定。能够可靠地对复发和死亡高风险患者进行风险分层的预后标志物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，预后标记物也可以帮助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（mRNA和microRNA表达、拷贝数变化和dna甲基化）分析方面取得了进展，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志物，并了解内分泌癌中失调的基因/途径。从这些分析中，我们已经确定了miR-30a-LOX轴在甲状腺癌进展中很重要。我们发现miR-30a表达降低和LOX过表达与更侵袭性分化甲状腺癌和更低生存率显著相关（即使在低风险的常规甲状腺乳头状癌中也是如此）。我们的后续研究表明，miR-30a-LOX通过转录调节EMT转录因子SNAI2的表达和调节TIMP4的分泌，介导其对上皮-间质转化（EMT）的影响。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的预后标志物。通过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，我们确定了肾上腺皮质癌中高甲基化和下调的候选肿瘤抑制基因，这是肿瘤发生和发展中肿瘤抑制基因沉默的共同机制。其中鉴定出的基因之一是RARRES2，该基因先前被证明可以介导对癌症的免疫反应。由于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。我们发现肾上腺皮质癌细胞系中的RARRES2在体外和体内免疫功能低下小鼠模型中抑制生长和侵袭。RARRES2在肾上腺皮质腺瘤和肾上腺皮质癌之间的表达也有显著差异，对肾上腺皮质腺瘤和肾上腺皮质癌具有较高的鉴别准确率。在原发性和转移性肾上腺皮质癌中均可见到RARRES2的缺失，这表明它是一个早期事件。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中常见的失调通路（WNT/ β -连环蛋白、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β -连环蛋白的总水平。除了上述有希望的肾上腺皮质癌标志物外，我们还分析并鉴定了区分肾上腺皮质癌和良性肾上腺皮质肿瘤的尿液代谢物。

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.