Human Cancer Xenografts in Outbred Nude Mice Can Be Confounded by Polymorphisms in a Modifier of Tumorigenesis

Abstract

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.

Modeling of Patient-Derived Xenografts in Colorectal Cancer

“…Rodent GEMM models typically examine a single gene or limited series of genetic lesions that in many cases do not capture the complexity or diversity of the human heterogenous CRC disease state. As another simplistic main stay human/rodent model by contrast, subcutaneous or orthotopic injection of CRC tumor cells has long been used for preclinical drug testing (42,43) but as mentioned lacks the molecular and genetic complexity found in colon tumors (6–14). Orthotopic studies in CRC have been limited by reproducibility and complexity of the cecal injections, and are rarely used in qualifying novel therapies for clinical trial development.…”

Immune Relevant and Immune Deficient Mice: Options and Opportunities in Translational Research

“…An internet search for commercially available immunodeficient mice bearing the Prkdc scid (scid) or Foxn1 nu (nude or nu) mutations returns more than 20 strains of each on inbred or non-inbred backgrounds, some with quite similar names but with immune variations relevant to their genetic backgrounds (and with quite different costs that can influence purchasing decisions). [91][92][93] Variation in "leakiness" in scid mice on different genetic backgrounds is a well-known example. Leakiness refers to the tendency of scid mice to produce some functional B and T cells as they age and are increasingly exposed to environmental antigenic stimuli.…”

Exosomes infl uence the engraftment of tumor cell lines in athymic mice BALB/c nude

“…In cancer research a large number of various tumor cell lines are used for inoculation hence, it is comparatively easy to engraft a tumor being studied in the mice just inoculating the host-animal with the tumor cells. It is believed that BALB/c Nude mice can host even immunologically incompatible, xenogneic for mice human tumors, (Liebman, 2007;Zeineldin, 2014;Conrad, 2015).…”