Insig2 is associated with colon tumorigenesis and inhibits Bax-mediated apoptosis.
Insulin-induced gene 2 (Insig2) was recently identified as a putative positive prognostic biomarker for colon cancer prognosis. Insig2 has been previously reported to be an endoplasmic reticulum (ER) membrane protein, and a negative regulator of cholesterol synthesis. Here we report that Insig2 was validated as a gene with univariate negative prognostic capacity to discriminate human colon cancer survivorship. To investigate the functional roles it plays in tumor development and malignancy, Insig2 was over-expressed in colon cancer cells resulting in increased cellular proliferation, invasion, anchorage independent growth and inhibition of apoptosis. Over-expression of Insig2 appeared to suppress chemotherapeutic drug treatment-induced Bcl2 associated X protein (Bax) expression and activation. Insig2 was also found to localize to the mitochondria/heavy membrane fraction and associate with conformationally changed Bax. Moreover, Insig2 altered the expression of several additional apoptosis genes located in mitochondria, further supporting its new functional role in regulating mitochondrial mediated apoptosis. Our findings show that Insig2 is a novel colon cancer biomarker, and suggest, for the first time, a reasonable connection between Insig2 and Bax-mediated apoptosis through the mitochondrial pathway.
Li
Chang Gong
CG
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
Gruidl
Mike
M
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
Eschrich
Steven
S
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
McCarthy
Susan
S
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
Wang
Hong-Gang
HG
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
Alexandrow
Mark G
MG
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
Yeatman
Timothy J
TJ
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL.
D017209:Apoptosis / Q000235:genetics; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D018076:DNA, Complementary / Q000138:chemical synthesis; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D053208:Kaplan-Meier Estimate; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D016133:Polymerase Chain Reaction; D040081:Protein Array Analysis; D034622:RNA Interference; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
D014408:Biomarkers, Tumor; D018076:DNA, Complementary; C467727:INSIG2 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c