Abstract: P>Objective To investigate the effect of curcumin on human esophageal cancer EC9706 cells and explore the role of heat shock protein(HSP70) in cell apoptosis by examining changes in the nuclear matrix and its relationship with apoptosis-related proteins. Methods Cell counting and flow cytometry were performed to probe the inhibitory effect of curcumin on cellular proliferation. Transmission electron microscopy and optical microscopy were used to observe the structural changes in EC9706 cells before and after apoptosis. Agarose gel electrophoresis was conducted to investigate the DNA structure of EC9706 cells before and after apoptosis. Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and mass spectrometry (MS) analysis were performed to investigate the presence and changes of HSP70 in the nuclear matrix of EC9706 cells before and after curcumin treatment, which was further corroborated by Western blotting assay. Laser confocal scanning microscopy was used to observe the colocalization of HSP70 with Bax and Bcl-2 during apoptosis. Results BR>The results indicated that curcumin could markedly inhibited EC9706 cell proliferation and finally induced apoptosis. Data from 2-D PAGE, MS, and Western blotting showed that HSP70 was involved in the nuclear matrix proteins and expression of HSP70 was downregulated after curcumin treatment. Laser confocal microscopy showed that HSP70 colocalized with Bax and Bcl-2, and the colocalized regions were altered by the curcumin treatment. Conclusion Our work proves that curcumin could definitely induce EC9706 cells into apoptosis. As a new found nuclear matrix protein, the expression and distribution of HSP70 are altered during the apoptosis of EC9706 cells. The colocalization of HSP70 with apoptosis-related genes evidently affects the apoptosis of EC9706 cells. BR>/P>

Key words: Curcumin, Heat shock protein70, EC9706 cell, Esophageal cancer, Flow cytometry, Agarose gel electrophoresis, Human