Abstract: Background and purpose: Diallyl disulfide (DADS) could inhibit the growth of cancer cells. This study aimed to investigate the effect of DADS and overexpression of RORα on EMT in human gastric cancer MGC803 cells with upregulation of RORα by DADS. Methods: The morphological effect on MGC803 cells was observed by phase-contrast microscope. The correlative molecules with EMT were detected by RT-PCR, Western blot, immunofluorescence and immunohistochemistry. The influence on xenograft tumor growth in nude mice was observed in MGC803 cells. Results: Phase-contrast microscope showed that MGC803 cells were of identical size, round or oval with decreased spindle cells and lower level of heteromorphism in DADS group and RORα/MGC803 group. The above-mentioned alterations were more obvious in RORα/MGC803+DADS group. Western blot exhibited obviously the downregulation of Snail protein in DADS group and RORα/MGC803 group (P<0.05). RT-PCR and Western blot disclosed that the expression of Vimentin was downregulated notably and E-cadherin was upregulated in DADS group, RORα/MGC803 group, and RORα/MGC803+DADS group more obviously (P<0.05). Immunofluorescence revealed that the positive expression of Snail and Vimentin protein was attenuate, while E-cadherin was strengthened in DADS group, RORα/MGC803 group and RORα/MGC803+DADS group compared with MGC803 cells. Moreover, the xenograft tumor growth was markedly decreased, and body weight of transplanted tumor was visibly reduced with the inhibition ratio of 15.07%, 26.55 % and 49.27%, respectively (P<0.05). The positive expression of Ki-67, CD34 and Vimentin were obviously decreased, while the positive expression of E-cadherin was increased. Conclusion: Overexpression of RORα can remarkably enhance inhibition of EMT in MGC803 cells by DADS in vivo and in vivo.

Key words: Diallyl disulfide, RORα, Human gastric cancer MGC803 cells, Epithelial-mesenchymal transformation, Snail, Vimentin, E-cadherin