Studies on Inducing Apoptosis Effects and Mechanism of CIK Cells for MGC-803 Gastric Cancer Cell Lines

Abstract

The induction of apoptosis and antiproliferation effect of cytokine-induced killer cells (CIK cells) on MGC- 803 cells and its mechanisms were studied by using a tetrazolium dye-based (MTT) assay. Morphological changes were observed by using inverted microscope, haematoxylin/eosin (HE) staining, scanning electron microscope, and transmission electron microscope. The TdT-mediated dUTP nick and labeling (TUNEL) method was used to detect the apoptosis-induced by CIK cells. The expression rate of p53, p16, C-myc, Bcl-2, and Bax proteins were studied by using immunohistochemical staining. There were significant differences according to varied effector-target ratios at the same working time (p < 0.01) and the same effector-target ratios at different working times (p < 0.01). Inverted microscope and HE staining observation showed that CIK cells were closer to the target cells and formed a typical "rose" shape. The scanning electron microscope showed that most target cells had undergone apoptosis and many "apoptotic bodies," and that transmission electron microscopy showed condensed chromatin, disintegration of the nucleolus, vacuoles in the cytoplasm, and apoptotic bodies appearing in most target cells. TUNEL analysis showed that apoptotic cells contract and turn navy blue in nuclei or perinuclei in the experimental group. The apoptotic rate was upmodulated between 5 and 14 hours and downregulated between 14 and 24 hours in the "CIK" experimental group. The expression of p53, p16, C-myc, and Bcl-2 were significantly downregulated (p < 0.01), and the expression of Bax was upregulated over the time of coculture in the "CIK" experimental group, compared to the control group. Our studies suggested that CIK cells induce apoptosis and have an antiproliferative effect on human MGC-803 gastric cancer cells. The CIK cells kill MGC-803 gastric cancer cells by inducing apoptosis in the early stage and by inducing necrosis in the late stage through the downregulating expression of p53, C-myc, and Bcl-2 and the upregulating expression of Bax.