Glucose-regulated
protein 78 (
GRP78) is expressed as part of the molecular response to endoplasmic reticulum (ER) stress and mediates protein folding within the cell.
GRP78 is also an important
biomarker of
cancer progression and the therapeutic response of patients with different
cancer types. However, the role of
GRP78 in the cytotoxic effect of
17-DMAG in
colon cancer cells remains unclear.
GRP78 expression was knocked down by
small interfering RNA (
siRNA). The anticancer effects of
17-DMAG were assessed by an
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a flow cytometric cell-cycle analysis, and an
Annexin V-
propidium iodide (PI) apoptotic assay. We found that HT-29 cells expressed a lower level of
GRP78 compared with DLD-1 cells. The MTT assay revealed that HT-29 cells were more sensitive to
17-DMAG treatment than DLD-1 cells.
GRP78 knock down (GRP78KD) cells demonstrated an increased sensitivity to
17-DMAG treatment compared with the scrambled control cells. Based on the cell-cycle analysis and
Annexin V-PI apoptotic assay, apoptosis dramatically increased in GRP78KD cells compared with scrambled control DLD-1 cells after these cells were treated with
17-DMAG. Finally, we observed a decrease in the level of Bcl-2 and an increase in the levels of Bad and Bax in GRP78KD cells treated with
17-DMAG. These results are consistent with an increased sensitivity to
17-DMAG after knock down of
GRP78. The level of
GRP78 expression may determine the therapeutic efficacy of
17-DMAG against
colon cancer cells.