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Overexpression of pRB in human pancreatic carcinoma cells: function in chemotherapy-induced apoptosis
Thomas Plath1, Michael Peters, Katharina Detjen
1T. Plath, M. Peters, K. Detjen, M. Welzel, Z. von Marschall, B. Wiedenmann, S. Rosewicz (Department of Hepatology and Gastroenterology), C. Radke (Department of Pathology), Charité, Campus Virchow-Klinikum, Humboldt-University, Berlin, Germany.
Background:
Human pancreatic adenocarcinomas are highly resistant to chemotherapy. The p16 tumor-suppressor protein is inactivated in more than 90% of human pancreatic cancers. The p16 protein transcriptionally inhibits expression of retinoblastoma tumor-suppressor gene pRB. The pRB protein transcriptionally inhibits expression of the p16 gene. Because pRB normally prevents apoptosis, we investigated whether pRB is involved in resistance to chemotherapy-induced apoptosis in pancreatic cancer cells.
Methods:
pRB expression was examined by immunohistochemistry in 106 human pancreatic tissue specimens. The human pancreatic tumor cell line Capan-1 (pRB+/p16-) was stably transfected with p16 to functionally inactivate pRB. pRB gene expression was examined by western and northern blot analyses, and pRB function was assessed by electrophoretic mobility shift assays and promoter transactivation studies for the transcription factor E2F. Changes in cell sensitivity to chemotherapy were measured by assays for cytotoxicity and apoptosis.
Results:
pRB was overexpressed in pancreatic ductal adenocarcinomas but was hardly detectable in other pancreatic malignancies, chronic pancreatitis, or nontransformed human pancreatic tissue. Expression of p16 in Capan-1 cells resulted in the loss of pRB gene and protein expression concomitant with increased activity of the transcription factor E2F, which was not detected in wild-type or control-transfected Capan-1 cells. Wild-type and control-transfected Capan-1 cells were resistant to chemotherapy-induced apoptosis, but pRB-depleted (i.e., p16-transfected) Capan-1 cells were highly sensitive. The effect was specific to pRB depletion because two other human pancreatic cancer cell lines that retained high pRB expression after p16 transfection were resistant to chemotherapy-induced apoptosis.
Conclusions:
Overexpression of pRB is associated with human pancreatic duct-cell cancer and may allow pancreatic cancer cells to evade chemotherapy-induced apoptosis.
Insights
Overexpression of the retinoblastoma tumor-suppressor protein (pRB) is linked to pancreatic cancer resistance to chemotherapy. Depleting pRB in cancer cells increased their sensitivity to chemotherapy-induced apoptosis.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Human pancreatic adenocarcinomas exhibit significant resistance to chemotherapy.
- The p16 tumor suppressor is inactivated in over 90% of pancreatic cancers, affecting pRB expression.
- pRB normally prevents apoptosis, prompting investigation into its role in chemotherapy resistance.
Purpose of the Study:
- To investigate the role of the retinoblastoma tumor-suppressor protein (pRB) in chemotherapy-induced apoptosis resistance in pancreatic cancer cells.
- To determine the association between pRB overexpression and pancreatic ductal adenocarcinoma.
- To explore the therapeutic potential of targeting pRB in pancreatic cancer treatment.
Main Methods:
- Examined pRB expression via immunohistochemistry in 106 human pancreatic tissue specimens.
- Utilized Capan-1 cell line, transfecting with p16 to functionally inactivate pRB.
- Assessed pRB gene/protein expression, E2F transcription factor activity, and cell sensitivity to chemotherapy-induced cytotoxicity and apoptosis.
Main Results:
- pRB was overexpressed in pancreatic ductal adenocarcinomas but not in other pancreatic tissues.
- p16 transfection led to loss of pRB expression and increased E2F activity in Capan-1 cells.
- pRB-depleted cells showed high sensitivity to chemotherapy-induced apoptosis, unlike control cells.
Conclusions:
- pRB overexpression is associated with human pancreatic ductal cancer.
- pRB may enable pancreatic cancer cells to evade chemotherapy-induced apoptosis.
- Targeting pRB could be a strategy to overcome chemotherapy resistance in pancreatic cancer.
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