Overexpression of pRB in human pancreatic carcinoma cells: function in chemotherapy-induced apoptosis.
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.
Plath
Thomas
T
T. 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.
Peters
Michael
M
Detjen
Katharina
K
Welzel
Martina
M
von Marschall
Zofia
Z
Radke
Cornelia
C
Wiedenmann
Bertram
B
Rosewicz
Stefan
S
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy / Q000235:genetics*; D018797:Cell Cycle Proteins; D002471:Cell Transformation, Neoplastic; D004268:DNA-Binding Proteins; D019008:Drug Resistance, Neoplasm; D050684:E2F Transcription Factors; D015972:Gene Expression Regulation, Neoplastic; D016161:Genes, Retinoblastoma; D019942:Genes, p16; D006801:Humans; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000235:genetics*; D014157:Transcription Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D014157:Transcription Factors