MUC1c regulates cell survival in pancreatic cancer by preventing lysosomal permeabilization.
BACKGROUND
MUC1 is a type I transmembrane glycoprotein aberrantly overexpressed in various cancer cells including pancreatic cancer. The cytosolic end of MUC1 (MUC1-c) is extensively involved in a number of signaling pathways. MUC1-c is reported to inhibit apoptosis in a number of cancer cells, but the mechanism of inhibition is unclear.


METHODS
Expression of MUC1-c was studied in the pancreatic cancer cell line MIAPaCa-2 at the RNA level by using qRTPCR and at the protein level by Western blotting. MUC1-c expression was inhibited either by siRNA or by a specific peptide inhibitor, GO-201. Effect of MUC1-c inhibition on viability and proliferation and lysosomal permeabilization were studied. Association of MUC1-c with HSP70 was detected by co-immunoprecipitation of MUC1-c and HSP70. Localization of MUC1-c in cellular organelles was monitored by immunofluorescence and with immuno- blotting by MUC1-c antibody after subcellular fractionation.


RESULTS
Inhibition of MUC1-c by an inhibitor (GO-201) or siRNA resulted in reduced viability and reduced proliferation of pancreatic cancer cells. Furthermore, GO-201, the peptide inhibitor of MUC1-c, was effective in reducing tumor burden in pancreatic cancer mouse model. MUC1-c was also found to be associated with HSP70 in the cytosol, although a significant amount of MUC1 was also seen to be present in the lysosomes. Inhibition of MUC1 expression or activity showed an enhanced Cathepsin B activity in the cytosol, indicating lysosomal permeabilization. Therefore this study indicates that MUC1-c interacted with HSP70 in the cytosol of pancreatic cancer cells and localized to the lysosomes in these cells. Further, our results showed that MUC1-c protects pancreatic cancer cells from cell death by stabilizing lysosomes and preventing release of Cathepsin B in the cytosol.
Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, Minnesota, United States of America.
Sulagna
S
Banerjee
Nameeta
N
Mujumdar
Vikas
V
Dudeja
Tiffany
T
Mackenzie
Tara K
TK
Krosch
Veena
V
Sangwan
Selwyn M
SM
Vickers
Ashok K
AK
Saluja
D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D018396:Mucin-1 / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000503:physiopathology*; D010455:Peptides / Q000494:pharmacology; D010539:Permeability; D021122:Protein Subunits / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*
C549568:GO 201; D018840:HSP70 Heat-Shock Proteins; D018396:Mucin-1; D010455:Peptides; D021122:Protein Subunits; C577056:muc1 protein, mouse