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