Table6_The MexTAg collaborative cross: host genetics affects asbestos related disease latency, but has little influence once tumours develop.docx

Objectives: This study combines two innovative mouse models in a major gene discovery project to assess the influence of host genetics on asbestos related disease (ARD). Conventional genetics studies provided evidence that some susceptibility to mesothelioma is genetic. However, the identification of host modifier genes, the roles they may play, and whether they contribute to disease susceptibility remain unknown. Here we report a study designed to rapidly identify genes associated with mesothelioma susceptibility by combining the Collaborative Cross (CC) resource with the well-characterised MexTAg mesothelioma mouse model.
Methods: The CC is a powerful mouse resource that harnesses over 90% of common genetic variation in the mouse species, allowing rapid identification of genes mediating complex traits. MexTAg mice rapidly, uniformly, and predictably develop mesothelioma, but only after asbestos exposure. To assess the influence of host genetics on ARD, we crossed 72 genetically distinct CC mouse strains with MexTAg mice and exposed the resulting CC-MexTAg (CCMT) progeny to asbestos and monitored them for traits including overall survival, the time to ARD onset (latency), the time between ARD onset and euthanasia (disease progression) and ascites volume. We identified phenotype-specific modifier genes associated with these traits and we validated the role of human orthologues in asbestos-induced carcinogenesis using human mesothelioma datasets.
Results: We generated 72 genetically distinct CCMT strains and exposed their progeny (2,562 in total) to asbestos. Reflecting the genetic diversity of the CC, there was considerable variation in overall survival and disease latency. Surprisingly, however, there was no variation in disease progression, demonstrating that host genetic factors do have a significant influence during disease latency but have a limited role once disease is established. Quantitative trait loci (QTL) affecting ARD survival/latency were identified on chromosomes 6, 12 and X. Of the 97-protein coding candidate modifier genes that spanned these QTL, eight genes (CPED1, ORS1, NDUFA1, HS1BP3, IL13RA1, LSM8, TES and TSPAN12) were found to significantly affect outcome in both CCMT and human mesothelioma datasets.
Conclusion: Host genetic factors affect susceptibility to development of asbestos associated disease. However, following mesothelioma establishment, genetic variation in molecular or immunological mechanisms did not affect disease progression. Identification of multiple candidate modifier genes and their human homologues with known associations in other advanced stage or metastatic cancers highlights the complexity of ARD and may provide a pathway to identify novel therapeutic targets.

研究目的：本研究在一项大型基因发现项目中结合两种创新性小鼠模型，以探究宿主遗传学对石棉相关疾病（asbestos related disease, ARD）的影响。既往经典遗传学研究已证实，间皮瘤（mesothelioma）的部分易感性具有遗传基础。然而，宿主修饰基因的鉴定、其潜在作用机制，以及其是否参与疾病易感性调控，目前仍不明确。本研究通过整合协同杂交（Collaborative Cross, CC）小鼠资源与特征明确的MexTAg间皮瘤小鼠模型，构建了可快速鉴定间皮瘤易感相关基因的研究体系。
研究方法：协同杂交小鼠资源是一款强大的小鼠模型体系，其涵盖了小鼠物种中超过90%的常见遗传变异，可实现复杂性状介导基因的快速鉴定。MexTAg小鼠仅在暴露于石棉后，可快速、一致且可预测地发生间皮瘤。为探究宿主遗传学对ARD的影响，本研究将72种遗传背景各异的CC小鼠品系与MexTAg小鼠进行杂交，将获得的CC-MexTAg（CCMT）子代小鼠暴露于石棉，并对其多项表型进行监测：包括总生存期、石棉相关疾病发病时间（潜伏期）、从发病至安乐死的时间（疾病进展时长）以及腹水体积。本研究鉴定了与上述表型相关的表型特异性修饰基因，并通过人类间皮瘤数据集，验证了人类直系同源基因在石棉诱导癌变过程中的作用。
研究结果：本研究共构建了72种遗传背景各异的CCMT品系，并将其共计2562只子代小鼠暴露于石棉。正如CC资源的遗传多样性特征所示，受试小鼠的总生存期与疾病潜伏期存在显著差异。但令人意外的是，疾病进展时长并无明显差异，这表明宿主遗传因素在疾病潜伏期阶段发挥了显著调控作用，但在疾病确诊后仅具有有限影响。本研究在6号、12号及X号染色体上，鉴定到了影响ARD总生存期与潜伏期的定量性状位点（Quantitative Trait Locus, QTL）。在跨越这些QTL区域的97个蛋白编码候选修饰基因中，有8个基因（CPED1、ORS1、NDUFA1、HS1BP3、IL13RA1、LSM8、TES及TSPAN12）在CCMT数据集与人类间皮瘤数据集中均被证实可显著影响疾病结局。
研究结论：宿主遗传因素可影响石棉相关疾病的发病易感性。但在间皮瘤确诊后，分子或免疫机制层面的遗传变异并不会对疾病进展产生影响。本研究鉴定出的多个候选修饰基因及其人类同源基因，在其他晚期或转移性癌症中已被证实存在关联，这凸显了ARD的发病复杂性，同时也为新型治疗靶点的发掘提供了潜在方向。