Biologic instability of pancreatic cancer xenografts in the nude mouse

Tumor transplants into nude mice (NM) may reveal abnormal biological behavi or compared with the original tumor. Despite this, human tumor xenografts i n NM have been widely used to study the biology of tumors and to establish diagnostic and therapeutic modalities. Clearly, precise differences in the biology of a given tumor in human and in NM cannot be assessed. We compared the growth kinetics, differentiation pattern and karyotype of an anaplasti c Syrian hamster pancreatic cancer cell line in NM and in allogenic hamster s. As with the original tumor, transplants in hamsters grew fast, were anap lastic and expressed markers related to tumor malignancy like galectin 3, T GF-alpha and its receptor EGFR at high levels. However, tumors in the NM we re well-differentiated adenocarcinomas, grew slower, had increased apoptoti c rate and had a high expression of differentiation markers such as blood g roup A antigen, DU-PAN-2, carbonic anhydrase II, TGF-beta(2) and mucin. Kar yotypically, the tumors in the NM acquired additional chromosomal damage. O ur results demonstrate significant differences in the morphology and biolog y of tumors grown in NM and the allogenic host, and call for caution in ext rapolating data obtained from xenografts to primary cancer.