The results from the in vivo lung metastasis assay showing that DMT1 silencing promotes the growth of metastatic nodules upon lung colonization and the data obtained from PDXs triple-negative breast cancer models as well as a comprehensive database comparing normal, tumor, and metastatic tissue, strongly support 3D cell culture as a representative readout to evaluate cancer-related processes. The gene discussed is SLC11A2; the disease is triple-negative breast carcinoma.