First, we validated the reduction in ETV4 mRNA found after GPR55 stable knockdown by silencing the receptor transiently in MDA-MB-231 cells and an additional triple-negative breast cancer cell line (MDA-MB-468, Figure 4B), which ruled out the possibility that reduced ETV4 mRNA levels were a consequence of adaptive mechanisms to the chronic lack of GPR55 or a cell line-specific event. This evidence concerns the gene GPR55 and triple-negative breast carcinoma.