MUC1c regulates cell survival in pancreatic cancer by preventing lysosomal permeabilization.

Abstract

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.

METHOD:

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.

• Authors: Sulagna Banerjee, Nameeta Mujumdar, Vikas Dudeja, Tiffany Mackenzie, Tara K Krosch, Veena Sangwan, Selwyn M Vickers, Ashok K Saluja
• Journal: PloS one (PLoS One) Vol. 7 Issue 8 Pg. e43020 ( 2012) ISSN: 1932-6203 [Electronic] United States
• PMID: 22912777 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• GO 201
• HSP70 Heat-Shock Proteins
• Mucin-1
• Peptides
• Protein Subunits
• muc1 protein, mouse

Topics

• Animals
• Blotting, Western
• Cell Line, Tumor
• Cell Survival (physiology)
• HSP70 Heat-Shock Proteins (metabolism)
• Immunoprecipitation
• Lysosomes (metabolism)
• Mice
• Mucin-1 (metabolism)
• Pancreatic Neoplasms (physiopathology)
• Peptides (pharmacology)
• Permeability
• Protein Subunits (metabolism)
• Real-Time Polymerase Chain Reaction
• Signal Transduction (physiology)