LAUSR

The present study aimed to screen and study the roles of differentially expressed proteins in the human esophageal cancer cell line Eca‑109, in the presence and absence of gemcitabine (GEM). The 3‑(4,5)‑dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) method was used to assay the vitality of the Eca‑109 cells following treatment with GEM (1‑16 µg/ml). The cell apoptosis was measured by using fluorescence activated cell sorting. The proteins in the treated Eca‑109 cells were extracted, validated, and assayed via two‑dimensional gel electrophoresis combined with matrix‑assisted laser desorption/ionization time of flight mass spectrometry (MALDI‑TOF‑MS). The differentially expressed proteins were then determined by western blotting. Furthermore, alterations in mitochondrial ultrastructure of the treated cells were observed under a transmission electron microscope. GEM significantly inhibited the growth of the Eca‑109 cells in a concentration‑ and time‑dependent manner, and the 50% inhibition concentration (IC50) value was 3.87 µg/ml. The MALDI‑TOF‑MS analysis revealed that there were three differentially expressed proteins following the GEM treatment, compared with the control. The differential proteins were verified to be B cell lymphoma‑2 associated X, apoptosis regulator (Bax)‑α, apoptosis‑associated speck‑like protein containing a CARD (ASC) and myeloid cell leukemia sequence (Mcl)‑1. Western blotting revealed that the expression levels of ASC and Bax‑α proteins in the treated cancer cells were significantly upregulated, whereas the Mcl‑1 protein expression was markedly downregulated compared with the control. Furthermore, the GEM treatment destroyed the mitochondrial ultrastructure of the cancer cells, leaving swelled mitochondria, a fading matrix and destroyed the mitochondrial cristae. GEM significantly inhibits the growth and promotes apoptosis of the Eca‑109 cells, due to the alterations in the expression levels of the differential proteins, including ASC, Mcl‑1 and Bax‑α.