Photodynamic effect of chlorin e6 on cytoskeleton protein of human colon cancer SW480 cells.

BACKGROUND: Photodynamic therapy (PDT) is based on photochemical and photobiological reactions mediated by photosensitizers to achieve a killing effect on diseased cells. It is used in the treatment of malignant tumors, precancerous lesions and infections. OBJECTIVE: In order to provide theoretical data for further study of the mechanism of PDT for colorectal cancer, SW480 cells were treated with Ce6-PDT and effect of photodynamic therapy (Ce6-PDT) on cytoskeleton and E-cadherin protein were observed. METHODS: The survival of SW480 cells was detected by MTT assay. The morphological changes of SW480 cells after Ce6-PDT were observed by scanning electron microscope (ESM). The migration ability was determined by wound healing assay. The distribution of F-actin in the cytoplasm was observed with confocal laser scanning microscope. Western blot analysis was used to detect the expression of cytoskeleton proteins in SW480 cells after Ce6-PDT. RESULTS: Compared with the control group, there was significant difference in cell viability of cells treated with Ce6-PDT (F = 78753.78, P < 0.05). The pseudopodia almost disappeared and cellular atrophy was clearly visible in the cells of Ce6-PDT group. The migration ability of cells treated with Ce6-PDT for 48 h was significantly lower than the control group (F = 11.794, P<0.001). The result of Western blot analysis showed that the expression of F-actin, α-tubulin, ß-tubulin and Vimentin in the cells treated with Ce6-PDT were significantly higher than that in the control group (F = 22.251,8.109, 5.840, 4.685 and 18.754, P < 0.05). The expression of E-cadherin in cells of Ce6-PDT group was significantly higher than that in control group (F = 30.882, P < 0.001). Perhaps Ce6-PDT inhibits the proliferation and migration of colon cancer SW480 cells by enhancing the expression of E-cadherin, causing the disappearance of cell pseudopodia and the destruction of cytoskeleton. CONCLUSIONS: The destruction of cytoskeleton might be one of the reasons for the inhibition of cell proliferation and migration by Ce6-PDT.

Downregulation of Rac1/PAK1/LIMK1/cofilin signaling pathway in colon cancer SW620 cells treated with Chlorin e6 photodynamic therapy.

BACKGROUND: Colorectal cancer is one of the most common gastrointestinal malignancies. Photodynamic therapy (PDT) is a novel and non-invasive treatment for tumors as PDT features small trauma, good applicability, andaccurate targeting. PDT may also be a potential treatment for colon cancer as itmay may induce suppressive effects on metastatic potential.. However, the molecular mechanism of the Chlorin e6 Photodynamic therapy (Ce6-PDT) inhibiting the migration of human colon cancer SW620 cells remains unclear. METHODS: Scratch wound healing assay, scanning electron microscope, MTT, immunofluorescence and laser confocal technique were used to investigate the suppressive effects of Ce6-PDT on the SW620 cells migration, pseudopodia, viability and the actin cytoskeleton. The effect of Ce6-PDT on actin-Filaments and signaling molecules of the Rac1/PAK1/LIMK1/cofilin signaling pathway in SW620 cells were examined by western blot analysis. RNA interference (RNAi) technology was used to establish siRNA-Rac1/SW620 cells. The combined effects of Ce6-PDT and RNAi on colon cancer SW620 cells was investigated by the same technology and methods mentioned above to clarify the signal transduction effect of Rac1/PAK1/LIMK1/cofilin signaling pathway in Ce6-PDT caused inhibition of SW620 cell migration. RESULTS: The healing and migration rate of the SW620 cells was significantly reduced and the cell pseudopodia were reduced or disappeared by Ce6-PDT. The Immunofluorescence and western blot analysis results showed that Ce6-PDT destroy microfilament's original structure and significantly downregulated F-actin protein expression. The Rac1/PAK1/LIMK1/cofilin signaling pathway was downregulated by Ce6-PDT. Furthermore, the RNAi significantly strengthened the effect of Ce6-PDT on colon cancer SW620 cells migration. CONCLUSIONS: Actin cytoskeleton and protrusions of SW620 cells correlate with its migration ability. Ce6-PDT suppresses SW620 cells migration by downregulating the Rac1/PAK1/LIMK1/cofilin signaling pathway, and its suppressive effect was enhanced by knocking down Rac1 gene expression.