Rapid in situ hybridization technique for detecting malignant mouse cell contamination in human xenograft tissue from nude mice and in vitro cultures from such xenografts

BACKGROUND. Presently, many laboratories are attempting to establish serially transplantable xenografts of human prostate cancer tissue inoculated into immune-compromised mice. Unfortunately, contamination of malignant mouse cells often occurs during the serial passage of the xenografts and can eventually outgrow the human prostate cancer cells. The purpose of this study was to develop a quick method to detect such malignant mouse cell contamination. METHODS. An in situ hybridization technique on histological tissue sections or single-cell spreads probed with commercially available human-specific genomic AIuI/II DNA oligonucleotides was used to detect human cells. RESULTS. This in situ hybridization is a rapid (i.e., <3 hr) and reproducible technique for distinguishing nonhuman neoplastic contamination from human cells in human xenografts passaged in nude mice. It is also very useful in confirming the human origin of tissue culture cells when they are established in vitro from xenografts passaged in mice. CONCLUSIONS. In order to prevent the passaging of contaminating malignant mouse cells, donor human tumor tissue can be tested with an AIuI/II in situ hybridization technique before it is used for subsequent in vivo passaging in nude mice.