SMAD4 and Pleural effusion: While both cell lines were sourced from a pleural effusion at a metastatic site, the MDA-MB-468 cells are basal-like and have homozygous mutations in PTEN, RB1, SMAD4, and TP53 while the MDA-MB-231 are mesenchymal stem-like and have homozygous mutations in CDKN2A, NF2, TP53, and heterozygous mutations in BRAF and KRAS [41].