Objective: To investigate changes of protein expression profiles between human choriocarcinoma JeG-3 cell line and its floxuridine (FUDR)-resistant sub-line.
Methods: The differentially expressed proteins were identified by using two dimension difference gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) approaches. Gene ontology (GO) analysis and Pathway analysis were used to screen the candidate proteins. The levels of the proteins in chemo-resistant sub-lines were validated by western blot. Ribonucleic acid interference (RNAi) was used to knockdown the expression of calreticulin (CALR) and (or) protein disulfide-isomerase A3 (PDIA3) respectively.
Results: Forty-six proteins spots were found to be significantly different in spot intensity by statistical analysis between chemo-resistance sub-line and parent cell line, of which 31 proteins were identified by MALDI-TOF-MS. Comparing to the parent cell lines, three endoplasmic reticulum (ER) protein folding molecular chaperones: CALR, PDIA3 and 78 000 glucose-regulated protein (GRP78) screened out were increased significantly in floxuridine-resistant sub-line and were verified by western blot. The resistance index decreased by knockdown the CALR and/or PDIA3 expression in FUDR-resistant sub-line 76.3% (36.7 ± 2.0 vs. 8.7 ± 3.1, P < 0.05) and 51.4% (36.7 ± 2.0 vs. 17.8 ± 1.2, P < 0.05) respectively.
Conclusion: These ER protein folding molecular chaperones, CALR, PDIA3 and GRP78, may involved in the mechanism of FUDR-resistance choriocarcinoma.