Different pattern of metastasis in liver implanted pancreatic cancer between young and old Syrian golden hamsters

We have previously reported on the "return trip" metastases from the liver to the pancreas in a hamster experimental pancreatic cancer model. Because the pancreas is the main metastatic site of liver-implanted pancreatic tumors, our aim was to clarify whether the metastatic sites differ in young and old tumor-bearing animals. HaP-T1, a continuous tissue-cultured cell line, derived from BHP-induced pancreatic adenocarcinoma, was implanted into the liver. The animals were divided into two groups: A) younger than 26 weeks and B) older than 26 weeks. Three animals from each group were sacrificed on Days 35, 42, 49, 56, 63, 70, 77, 84, 91 and 98, to study the metastatic sites. Survival was also studied. After death, necropsy was performed. Resected and necropsied specimens were analyzed histopathologically and by PCR/RFLP analysis to confirm the presence of K-ras point mutation. The success rate of implantation was 100%. Survival was 102.3+/-2.5 days in group A and 95.3+/-1.5 days in group B. Animals of group A, sacrificed weekly until Day 70, showed metastases only to the pancreas ("return trip"), while this phenomenon happened only in animals sacrificed on Day 35 in group B. In group A, on Days 77, 84, 91 and 98, metastases were also found in the kidneys, lymph nodes, ovary and testis. In hamsters of group B, metastases were found in multiple sites such as the pancreas, vas deferens, ovary and testis ("multiple journeys"). All intra-hepatically-implanted tumor and metastatic sites showed the K-ras point mutation. This homologous implantation model may be helpful for further research into the process of metastasis and its relationship with the immunological response.