Zeineldin Maged, Jensen Derek, Paranjape Smita R, Parelkar Nikhil K, Jokar Iman, Vielhauer George A, Neufeld Kristi L
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045 Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt.
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045.
Genetics. 2014 Aug;197(4):1365-76. doi: 10.1534/genetics.114.166587. Epub 2014 Jun 9.
Tumorigenicity studies often employ outbred nude mice, in the absence of direct evidence that this mixed genetic background will negatively affect experimental outcome. Here we show that outbred nude mice carry two different alleles of Pla2g2a, a genetic modifier of intestinal tumorigenesis in mice. Here, we identify previous unreported linked polymorphisms in the promoter, noncoding and coding sequences of Pla2g2a and show that outbred nude mice from different commercial providers are heterogeneous for this polymorphic Pla2g2a allele. This heterogeneity even extends to mice obtained from a single commercial provider, which display mixed Pla2g2a genotypes. Notably, we demonstrated that the polymorphic Pla2g2a allele affects orthotopic xenograft establishment of human colon cancer cells in outbred nude mice. This finding establishes a non-cell-autonomous role for Pla2g2a in suppressing intestinal tumorigenesis. Using in vitro reporter assays and pharmacological inhibitors, we show promoter polymorphisms and nonsense-mediated RNA decay (NMD) as underlying mechanisms that lead to low Pla2g2a mRNA levels in tumor-sensitive mice. Together, this study provides mechanistic insight regarding Pla2g2a polymorphisms and demonstrates a non-cell-autonomous role for Pla2g2a in suppressing tumors. Moreover, our direct demonstration that mixed genetic backgrounds of outbred nude mice can significantly affect baseline tumorigenicity cautions against future use of outbred mice for tumor xenograft studies.
致瘤性研究通常使用远交系裸鼠，而没有直接证据表明这种混合遗传背景会对实验结果产生负面影响。在此我们表明，远交系裸鼠携带Pla2g2a的两种不同等位基因，Pla2g2a是小鼠肠道肿瘤发生的一种遗传修饰因子。在此，我们鉴定出Pla2g2a启动子、非编码和编码序列中以前未报道的连锁多态性，并表明来自不同商业供应商的远交系裸鼠对于这种多态性Pla2g2a等位基因是异质的。这种异质性甚至延伸到从单个商业供应商获得的小鼠，它们表现出混合的Pla2g2a基因型。值得注意的是，我们证明多态性Pla2g2a等位基因会影响远交系裸鼠中人结肠癌细胞的原位异种移植建立。这一发现确立了Pla2g2a在抑制肠道肿瘤发生中的非细胞自主性作用。使用体外报告基因检测和药理学抑制剂，我们表明启动子多态性和无义介导的RNA衰变（NMD）是导致肿瘤敏感小鼠中Pla2g2a mRNA水平较低的潜在机制。总之，本研究提供了关于Pla2g2a多态性的机制性见解，并证明了Pla2g2a在抑制肿瘤中的非细胞自主性作用。此外，我们直接证明远交系裸鼠的混合遗传背景会显著影响基线致瘤性，这对未来将远交系小鼠用于肿瘤异种移植研究提出了警示。
