ESR1 and breast cancer: Indeed, Rac1-modulated pathways could be playing essential roles in developing resistance to different therapeutic approaches such as endocrine therapies, targeted therapies, and radiotherapy, as our enrichment analysis indicates common profiles between resistance to 5-FU-based therapies and gemcitabine and gefitinib in non-small cell lung cancer [92,93], dasatinib for breast, lung, and ovarian tumors [94], tamoxifen in estrogen receptor-positive breast cancer [95], and postradiation tumor escape of CRC [96].