Genetic Modifiers of Initiation and Progression of Mammary Cancer

乳腺癌仍然是最常见的恶性肿瘤，也是美国妇女癌症相关死亡的第二大原因。据估计，2018年美国有超过26.6万例新发乳腺癌病例，其中4.1万名患者死于这种疾病。虽然那些被诊断为局部疾病的患者的5年生存率接近100%，但被诊断为远处转移性疾病的患者的5年生存率仅为27%，这突出了转移过程在患者死亡率中的关键重要性。对于那些诊断为局限性疾病的患者，广泛应用辅助化疗可使晚期复发和长期死亡率降低约19%。然而，尽管做出了这些努力，25%接受辅助化疗的患者仍然进展为转移性疾病。尽管治疗策略发生了变化，但观察到这些患者的生存率几乎没有改善。目前，美国估计有15.5万名妇女患有转移性疾病，这凸显了这种疾病的重大公共卫生负担。因此，全面了解转移的病因和生物学，以制定更有效的临床干预措施，进一步降低晚期乳腺癌的发病率和死亡率，是至关重要的。在FY22中，我们执行了两个平行的策略来进一步研究乳腺癌转移的病因。第一种策略研究了可能作为转移进展驱动突变的体细胞突变和拷贝数变异的获得。我们扩展了之前在MMTV-PyMT小鼠模型中的分析，在我们的数据集中增加了额外的原发转移对，并分析了另外三种转移性乳腺癌模型，MMTV-Myc， MMTV-Her2和C3(1)-TAg。令人惊讶的是，与原发肿瘤转化不同，由单核苷酸变异（snv）诱导的转移中富集的激活突变相对罕见，这表明点突变不是肿瘤进展的主要驱动因素。相反，与原发肿瘤相比，复发性拷贝数变异（CNVs）往往以基因型特异性的方式富集转移瘤，这表明基因组不稳定性可能是转移性疾病的主要体细胞驱动因素。然而，尽管有这些复发性CNVs， RNAseq显示匹配的原发和转移性病变之间的转录差异很小。这些数据表明，在转移过程中，短暂的相互作用和细胞反应可能比稳定的差异更重要，并且在转移级联过程中，在多重细胞损伤和挑战中，可能需要基因组的不稳定性来实现细胞的可塑性。第二个策略是继续我们对转移易感性病因的遗传研究。在2022财年，我们发表了一项关于核孔蛋白NUP210在转移进展中的作用的研究结果。这些研究表明，NUP210介导从细胞外环境到迁移和侵袭基因启动子的机械信号传导，诱导肿瘤从原发肿瘤块扩散。有趣的是，蛋白质组学分析显示，先前发现的其他转移易感基因也参与了这种机械反应机制。这些独立鉴定的转移相关因子在单一多蛋白复合体上的聚合表明，我们的遗传策略正在询问转移级联的关键组成部分。重要的是，这些基因在转移的实验模型系统和人类临床样本中都不经常发生突变。因此，我们的基因易感性筛选似乎突出了传统癌症研究策略难以获得的重要细胞和分子机制。目前的工作集中在更详细的机制分析和可能有助于肿瘤播散机械转导反应的其他转移易感基因的潜在整合。

Breast cancer remains the most commonly diagnosed malignancy and is the second leading cause of cancer-related death in American women. It is estimated that there were more than 266,000 new cases of breast cancer in the United States in 2018, with 41,000 patients succumbing to the disease. Although the 5-year survival approaches 100% for those patients diagnosed with localized disease, the 5-year survival rate for patients diagnosed with distant metastatic disease in only 27%, highlighting the critical importance of the metastatic process in patient mortality. For those patients diagnosed with localized disease, the widespread application of adjuvant chemotherapy has reduced late relapse and long-term mortality by an estimated 19%. However, despite these efforts, 25% of patients receiving adjuvant chemotherapy still progress to metastatic disease. Despite changes in therapeutic strategies little improvement in the survival of these patients has been observed . At present it is estimated that 155,000 women are currently living with metastatic disease in the United States, highlighting the significant public health burden of this disease. It is therefore critically important to obtain a comprehensive understanding of the etiology and biology of metastases to develop more effective clinical interventions to further reduce the morbidity and mortality of advanced breast cancer. In FY22 we have performed two parallel strategies for further investigations into the etiology of breast cancer metastasis. The first strategy investigated the acquisition of somatic mutations and copy number variations that might function as driver mutations for metastatic progression. Extending our previous analysis in the MMTV-PyMT mouse model, we have added additional primary-metastasis pairs to our data set, as well as analyzing three additional models of metastatic mammary cancer, MMTV-Myc, MMTV-Her2 and C3(1)-TAg. Surprisingly, unlike the in primary tumor transformation, activation mutations enriched in metastases, induced by single nucleotide variants (SNVs), were relatively rare suggesting that point mutations are not a major driver of tumor progression. In contrast, recurrent copy number variations (CNVs) were frequently enriched metastases compared to primary tumors in a genotype-specific manner, suggesting that genomic instability may be the primary somatic driver of metastatic disease. Despite these recurrent CNVs, however, RNAseq revealed little transcriptional variation between matched primary and metastatic lesions. These data imply that transient interactions and cellular responses may be more important in metastatic progression than the stable differences, and that genomic instability may be required to enable cellular plasticity during the multiple cellular insults and challenges faced during the metastatic cascade. The second strategy pursued is the continuation of our genetic studies into the etiology of metastasis susceptibility. In FY2022 we published the results of a study of the role of the nuclear pore protein, NUP210, in metastatic progression. These studies demonstrated that NUP210 mediates mechanical signaling from the extracellular environment to poised promoters of migration and invasion genes, inducing tumor dissemination from the primary tumor mass. Intriguingly, proteomics analysis has revealed that additional, previously identified, metastasis susceptibility genes also participate in this mechanical response mechanism. The convergence of these independently identified metastasis-associated factors on a single multiprotein complex suggests that our genetic strategy is interrogating a critical component of the metastatic cascade. Importantly, these genes are not frequently mutated in either experimental model systems of metastasis nor in human clinical samples. Thus, our gene susceptibility screen appears to be highlighting important cellular and molecular mechanisms that would be difficult to access by conventional cancer research strategies. Current efforts are focused on more detailed analysis of the mechanisms and potential integration of additional metastasis susceptibility genes that may contribute to the tumor dissemination mechanotransduction response.