library_construction_protocol: Tamoxifen treated MCF-7 cells in each week were suspended and the suspensions were dispensed into ICELL8 Chip (Takara Bio). Wells containing single cell were selected, and then reverse transcription, cDNA synthesis, cDNA amplification were carried out using ICELL8 3' DE Reagent (Takara Bio). Sequencing library were prepared with NexteraXT DNA Library Prep Kit (Illumina)