NR2E3 and cancer: 1997) (Fig. 1). These results are similar to that found in human cancer cells, which also arrest in G1 phase when treated with an iron chelator (Brodie et al. 1993). These human cancer cells arrest after production of the G1/S‐phase cyclin E, but before production of the S‐phase cyclin A (Siriwardana and Seligman 2013). The human cancer cells grown under iron starvation also exhibited a second arrest point in S phase as a result of the inhibition of RNR (ribonucleotide reductase), which is needed to produce deoxynucleotides (Siriwardana and Seligman 2013).