Gene expression of Tamoxifen induced control (TC), dormancy-like (TD) or relapse (TR) cell samples

To generate a dormancy state in vivo, female BALB/c athymic mice with ER+MC cell (MCF7) derived xenografts were treated with Tamoxifen (TAM). Throughout the treatment period, no significant differences in the body weight of the TAM-treated groups (TD and TR) compared to the vehicle-treated groups (TC) were observed. Whereas xenografts in the vehicle-treated group (as control group: TC) continued to increase in volume, the xenograft volumes of the TAM-treated group regressed 20%-30% in the first week and then remained stable during the four-week administration of TAM. Thereafter, half of the xenografts in TAM-treated mice were resected at random and designated as a dormancy-like group (TD). For the remaining TAM treated xenografts, treatment was discontinued and xenograft volume was observed to gradually increase. This group was defined as the relapse group (TR) and would mimic relapses observed after discontinuation of anti-estrogen therapy in patients. Overall design: The TC, TD or TR cell lines were established in vitro from their corresponding xenografts for RNA-sequencing.