Study on changes of proliferation, migration and invasion abilities of radiation-induced polyploid colon cancer SW1116 cells and their progeny and the related mechanisms / 肿瘤研究与临床

ABSTRACT

Objective:To investigate the characteristics related to proliferation, migration and invasion of radiation-induced polyploid colon cancer SW1116 cells and their progeny.Methods:Colon cancer SW1116 cells were conventionally cultured in Leibovitz's L-15 medium containing 10% fetal bovine serum. SW1116 cells at logarithmic growth stage were irradiated with 7 Gy X-ray, and the morphological changes of the cells were observed by inverted microscope on days 3, 5, 10 and 19 after radiation induction. According to the morphological changes of the cells, the cells at day 3 after radiation induction were labeled as polyploid giant cancer cell (PGCC) group, and the cells at day 19 were recorded as PGCC progeny group. SW1116 cells without radiation induction were used as control group. Flow cytometry was used to detect cell ploidy in the control, PGCC and PGCC progeny groups, CCK-8 assay was used to detect the proliferation ability of the three groups, cell migration and invasion abilities of the three groups were detected by cell scratch assay and Transwell assay, and Western blotting was used to detect the expressions of cell cycle and proliferation-related proteins and epithelial-mesenchymal transition (EMT) marker N-cadherin (N-cad) in the three groups.Results:The volume of SW1116 cells gradually became larger on days 3, 5 and 10 after radiation induction, and returned to normal on day 19. The proportions of polyploid (DNA content >4N) cell subsets in the control group, PGCC group and PGCC progeny group were (2.3±1.1)%, (23.1±8.1)% and (3.2±0.5)%, the difference was statistically significant ( F = 18.52, P < 0.05), and the proportion of polyploid cell subpopulations in the PGCC group was higher than that in the control group ( t = 5.38, P < 0.01), but the differences between the PGCC progeny group and the control group were not statistically significant ( t = 0.22, P > 0.05). After 72 h of culture, the cell proliferation rates of the control, PGCC and PGCC progeny groups were (100.0±4.1)%, (73.5±0.7)% and (123.9±3.5)%, and the difference was statistically significant ( F = 190.27, P < 0.001). After 48 h of cell scratching, the scratch healing rates in the control, PGCC and PGCC progeny groups were (38.0±2.7)%, (41.5±4.0)% and (63.7±4.2)%, and the difference was statistically significant ( F = 43.05, P < 0.001). After 24 h of culture, the number of invasive cells in the control, PGCC and PGCC progeny groups was 12.9±1.2, 3.4±0.6 and 23.7±1.5, and the difference was statistically significant ( F = 63.64, P < 0.001). The expression levels of cell cycle-related proteins P-cdc25c, cdc25c and cdc2 in the PGCC group were lower than those in the control group (all P < 0.05), and the expression levels of transcription factor-related proteins E2F-2, E2F-3 and EMT marker N-cad were downregulated compared with the control group (all P < 0.05); the expression levels of P-cdc25c, cdc25c, cdc2, E2F-2, E2F-3 and N-cad proteins in the PGCC progeny group were higher than those in the control group (all P < 0.05). Conclusions:Radiation can induce colon cancer SW1116 cells to produce polyploid, which may then generate daughter cells through asymmetric mitosis and gain new life, and then promote the recurrence and metastasis of colon cancer.