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www.sciencedaily.com 科学家们1996年第一次在袋獾中发现袋獾面部肿瘤(Devil Facial Tumor Disease，DFTD)，这种肿瘤具有传染性，可以通过活的癌细胞在动物间传播，引发袋獾面部出现肿瘤等表现，在过去10年间袋獾的数量下降将近一半，这都跟这种传染病有很大关系。而近日刊登在国际杂志PNAS上的一项研究报告中，来自塔斯马尼亚大学的研究人员通过研究发现了另外一种具有传染性的肿瘤，这种肿瘤与之前的袋獾面部肿瘤在遗传性和组织特性上并不相同，研究者将这种新型的可传染的肿瘤称之为DFT2。
研究人员将DFTD称之为DFT1，Greg Woods博士表示，一种可传播的癌症非常罕见，而两种就更是少只有少了；这项研究中我们发现，DFT2的肿瘤在解剖学上同恶性的DFT1相似，但这两者在遗传性和组织特性上并不相同，DFT1细胞是呈束状排列的，而DFT2则是聚集在一起形成特殊的结构，通过分析肿瘤基因组中的微卫星特性，研究人员表示，DFT2是一种完全不同于DFT1的肿瘤，而且这种新型肿瘤表现出了在三组染色体中的重排现象，而DFT1仅存在X和Y染色体。
DFT1肿瘤细胞可以逃避宿主的免疫系统，尽管其存在着不同的主要组织相容性复合物（MHC）基因型，但其并不会在表面表达MHC分子；在哺乳动物中，MHC可以用来鉴别外来或者疾病的细胞，比如癌细胞等；而对DFT2肿瘤进行分析则会发现其存在一种不同的MHC基因型。因此研究人员想知道为何MHC基因如何会发生较大的变化。
如今研究人员重点研究如何调节DFT2的遗传性及对其进行转录组分析，同时他们还在不断开发抵御DFT1的疫苗；然而是否可以开发出一种疫苗来有效阻断DFT1或DFT2肿瘤目前还无定论，而且研究者还希望通过深入研究来确定是否DFT2的出现是否是因为DFT1耐药性的进行而致，当然相信随着科学家们后期进行深入的研究就可以对此进行解释了。
doi:10.1073/pnas.1519691113
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A second tranissible cancer in Taanian devils
Ruth J. Pyea, David Pembertonb, Cesar Tovara, Jose M. C. Tubioc, Karen A. Dund, Samantha Foxb, Jocelyn Darbya, Dane Hayese, Graeme W. Knowlese, Alexandre Kreissa, Hannah V. T. Siddlef, Kate Swifte, A. Bruce Lyonsg, Elizabeth P. Murchisonc,1,2, and Gregory M. Woodsa,1,2
Clonally tranissible cancers are somatic cell lineages that are spread between individuals via the transfer of living cancer cells. There are only three known naturally occurring tranissible cancers, and these affect dogs, soft-shell clams, and Taanian devils, respectively. The Taanian devil tranissible facial cancer was first observed in 1996, and is threatening its host species with extinction. Until now, this disease has been consistently associated with a single aneuploid cancer cell lineage that we refer to as DFT1. Here we describe a second tranissible cancer, DFT2, in five devils located in southern Taania in 2014 and 2015. DFT2 causes facial tumors that are grossly indistinguishable but histologically distinct from those caused by DFT1. DFT2 bears no detectable cytogenetic similarity to DFT1 and carries a Y chromosome, which contrasts with the female origin of DFT1. DFT2 shows different alleles to both its hosts and DFT1 at microsatellite, structural variant, and major histocompatibility complex (MHC) loci, confirming that it is a second cancer that can be tranitted between devils as an allogeneic, MHC-discordant graft. These findings indicate that Taanian devils have spawned at least two distinct tranissible cancer lineages and suggest that tranissible cancers may arise more frequently in nature than previously considered. The discovery of DFT2 presents important challenges for the conservation of Taanian devils and raises the possibility that this species is particularly prone to the emergence of tranissible cancers. More generally, our findings highlight the potential for cancer cells to depart from their hosts and become dangerous tranissible pathogens.
