Although these characteristics may explain why HEK293 can behave like a cancer cell, deregulation of the p53 pathway does not explain the ability of HEK293, Huh7, T47D and MCF7 to utilise ammonia as alternative nitrogen source, as Huh7 and T47D harbour p53 mutations resulting in a high level of p53 protein, while MCF7 cells does not harbour p53 mutations35,36 (Table 1). This evidence concerns the gene TP53 and cancer.