To rule out a cell-type specific phenotype and determine if ΔNp73 could increase the expression of iKC marker genes in non-primary cells, we infected MDA-MB-231 cells (mesenchymal triple-negative breast cancer cell line) with lentivirus encoding ΔNp73 (ΔNp73α and ΔNp73β) or empty vector control in combination with KLF4 + ΔNp63α (S5E Fig). Here, KLF4 is linked to triple-negative breast carcinoma.