Department of Pathology and Laboratory Medicine, Raymond and Ruth Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States of America.
Illumina, San Diego, CA, United States of America.
PLoS One. 2017 Nov 30;12(11):e0188667. doi: 10.1371/journal.pone.0188667. eCollection 2017.
Angiosarcomas (AS) are rare in humans, but they are a deadly subtype of soft tissue sarcoma. Discovery sequencing in AS, especially the visceral form, is hampered by the rarity of cases. Most diagnostic material exists as archival formalin fixed, paraffin embedded tissue which serves as a poor source of high quality DNA for genome-wide sequencing. We approached this problem through comparative genomics. We hypothesized that exome sequencing a histologically similar tumor, hemangiosarcoma (HSA), that occurs in approximately 50,000 dogs per year, may lead to the identification of potential oncogenic drivers and druggable targets that could also occur in angiosarcoma.
Splenic hemangiosarcomas are common in dogs, which allowed us to collect a cohort of archived matched tumor and normal tissue samples suitable for whole exome sequencing. Mapping of the reads to the latest canine reference genome (Canfam3) demonstrated that >99% of the targeted exomal regions were covered, with >80% at 20X coverage and >90% at 10X coverage.
Sequence analysis of 20 samples identified somatic mutations in PIK3CA, TP53, PTEN, and PLCG1, all of which correspond to well-known tumor drivers in human cancer, in more than half of the cases. In one case, we identified a mutation in PLCG1 identical to a mutation observed previously in this gene in human visceral AS. Activating PIK3CA mutations present novel therapeutic targets, and clinical trials of targeted inhibitors are underway in human cancers. Our results lay a foundation for similar clinical trials in canine HSA, enabling a precision medicine approach to this disease.
血管肉瘤（AS）在人类中较为罕见，但它是软组织肉瘤的一种致命亚型。AS 的发现测序，尤其是内脏形式的测序，受到病例罕见的阻碍。大多数诊断材料为存档的福尔马林固定、石蜡包埋组织，其作为全基因组测序的高质量 DNA 来源较差。我们通过比较基因组学来解决这个问题。我们假设对每年约有 50,000 只狗发生的组织学上相似的肿瘤——血管内皮肉瘤（HSA）进行外显子组测序，可能会发现潜在的致癌驱动因子和可用药靶点，这些也可能存在于血管肉瘤中。
脾血管肉瘤在狗中很常见，这使我们能够收集一组存档的匹配肿瘤和正常组织样本，适合进行全外显子组测序。将读取映射到最新的犬参考基因组（Canfam3）表明，靶向外显子区域的覆盖率>99%，其中>80%的区域达到 20X 覆盖度，>90%的区域达到 10X 覆盖度。
对 20 个样本的序列分析确定了 PIK3CA、TP53、PTEN 和 PLCG1 的体细胞突变，这些突变在超过一半的病例中与人类癌症中的已知肿瘤驱动因子相对应。在一个病例中，我们鉴定出 PLCG1 中的一个突变与之前在人类内脏 AS 中观察到的该基因中的突变相同。激活的 PIK3CA 突变提供了新的治疗靶点，针对这些靶点的靶向抑制剂的临床试验正在进行中。我们的研究结果为犬 HSA 中的类似临床试验奠定了基础，使针对这种疾病的精准医疗方法成为可能。
