The invention discloses application of gap junction 
protein and coding 
gene thereof in preparing medicament for reversing 
malignant phenotype of a 
cancer stem cell, and investigates the functional state of gap junction communication in the 
tumor stem cell, expression condition of the gap junction 
protein and relation between the gap junction 
protein and special biological characteristics of 
tumor stem cells. Results prove that compared with differentiated 
tumor cells, gap junction communication obstacle exists in the 
tumor stem cell, no clear gap junction like structure is found among the cells, and expressions of various gap junction protein, particularly gap junction protein 43(Cx43), is down regulated; the down regulation of the expression of the Cx43 is related to 
promoter methylation of coding 
gene GJA1 thereof and expression of micro 
RNA; recovering of the expression of the Cx43 in the 
tumor stem cell can remarkably reduce the self-renew ability, tumor forming ability and invasion ability of the 
tumor stem cells, which is related to partial 
recovery of the gap junction communication function, up regulation of E-
cadherin expression and inactivity of SDF-1 / CXCR4 downstream 
signal path (AKT and ERK1 / 2); and the gap junction protein and coding 
gene thereof can be used for preparing the medicament for reversing 
malignant phenotype of the 
cancer stem cell.