Antisense oligonucleotides specific to mutated K-ras genes inhibit invasiveness of human pancreatic cancer cell lines.

BACKGROUND/AIMS: Point mutations of the K-ras gene are detected in > 90% of human pancreatic cancers and may play an important role in tumorigenesis. However, correlations between mutant K-ras and the invasive activity of the tumor have remained unclarified. METHODS: 17-merphosphorothioate antisense oligonucleotides targeting K-ras point mutations were transfected into three kinds of human pancreatic cancer cell lines (MIAPaCa-2, PANC-1, and BxPC-3), and the invasive activity was investigated using an in vitro chemoinvasion assay. RESULTS: Antisense oligonucleotides strongly inhibited the invasive activity of the cell lines with mutant K-ras genes (MIAPaCa-2, PANC-1), but not in that with a wild-type K-ras (BxPC-3). CONCLUSION: Antisense oligonucleotides specific to mutated K-ras genes inhibited the invasiveness of human pancreatic cancer cell lines. Specific antisense therapy to the point mutation of K-ras might be a new anticancer strategy for pancreatic cancer.

Homologous orthotopic implantation models of pancreatic ductal cancer in Syrian golden hamsters: which is better for metastasis research--cell implantation or tissue implantation?

With a nitrosamine induced hamster pancreatic cancer cell line (HaP-T1), survival time and metastatic rates were compared between orthotopic cell implantation (OCI; n = 5) and orthotopic tissue implantation (OTI; n = 5) models. All the tumors were palpable (100% tumor take) after 1 week in both groups. Hamsters in the OCI group survived 71 +/- 2.17 days (range, 69-75 days), and in the OTI group, 73.8 +/- 4.03 days (range, 58-80 days). After necropsy, spontaneous metastases were noted in 100% of the animals. Direct invasion to adjacent organs was observed in four animals, and liver metastases, in three in the OTI group, which were significantly higher compared with the OCI group. On the other hand, peritoneal dissemination was observed only in the OCI group. Other metastatic sites showed no significant difference between the groups. All the histologically noted metastases had K-ras point mutation confirmed by polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) analysis. We conclude that the homologous OTI model may be more useful than the OCI model. The OTI model may contribute to the development of therapeutic strategies in the field of pancreatic cancer research because of the capacity for invasion to adjacent organs, higher liver metastatic rate, and similarity to the clinical picture of the disease.

Subcutaneously inoculated cells and implanted pancreatic cancer tissue show different patterns of metastases in Syrian golden hamsters.

CONTEXT: We studied behavior of the subcutaneously implanted pancreatic tumors and the process of metastasis using syngeneic Syrian golden hamsters. DESIGN: HaP-T1, a cell line derived from nitrosamine-induced pancreatic cancer in Syrian golden hamsters was used for this experiment. Thirty-five animals were divided into two groups: subcutaneous cell inoculation and subcutaneous tissue implantation. The tumor tissue was obtained from subcutaneously implanted cancer cells. One month after implantation, the tumors were resected and studied histopathologically. The animals were followed-up weekly by palpation of the peripheral lymph nodes in order to identify local recurrence. After death, necropsy was performed. Liver, lungs and pancreas specimens were taken for histopathogical study and detection of K-ras point mutation using the PCR/RFLP method. RESULTS: The mean survival time in the subcutaneous cell inoculation group was 151+/-17.5 days, and in the subcutaneous tissue implantation group was 137 +/-12.9 days. During the follow-up, 13 subcutaneously cell inoculated hamsters (86.7%) had right axillary lymph node metastasis while subcutaneously tissue implanted hamsters did not show any palpable lymph nodes. After necropsy, 10 of the 20 subcutaneously tissue implanted animals (50%) showed metastases in the lungs at the histopathological level. However, 16 of the 20 subcutaneously tissue implanted animals (80%) showed K-ras point mutation in the lung specimens. The lungs of the animals of the subcutaneous cell inoculation group did not show any metastases. No metastases were found in the liver or the pancreas in either group. CONCLUSION: This study suggests that homologous subcutaneous cell inoculation and subcutaneous tissue implantation models showed completely different patterns of metastasis. These models may aid further research to clarify the mechanisms of metastasis in pancreatic cancer.