To evaluate the gene expression of stem cells associated molecules, MDA-MB-231 and SKBR3 cells were overexpressed CD44 and then treated with the exosomes from CAFs with or without circHIF1A downregulation, the stem cell markers including OCT4, SOX2, ALDHA1, CD44, and Nanog in the presence of H-CAFs-exo with circHIF1A downregulation decreased and CD44 overexpression could rescue the decrease partially in breast cancer cells on transcriptional levels (Fig. 6F, G) and post-transcriptional levels (Fig. 6H). This evidence concerns the gene CD44 and breast cancer.