Heterozygous mutations in p97 and resistance to p97 inhibitors

In recent years, multiple studies including ours have reported on the mechanism of resistance towards p97 inhibitors. While all these studies outline target alteration via mutations in p97 as the primary mechanism of resistance, discrepancies persist in the current literature due to the occurrence of both heterozygous and homozygous mutations when using HCT116 cells. Here, we report a pre-existing heterozygous frameshift mutation at codon 616 (N616fs*) in one of the p97 alleles in HCT116 cells and show that this mutant allele is subjected to nonsense-mediated decay. Furthermore, we independently generated p97 inhibitor (CB-5083) resistant HCT116 cells, and we observed a single heterozygous mutation at codon 526 (L526S) in genomic DNA sequencing but a homozygous L526S mutation in complementary DNA sequencing, indicating that the missense mutation (L526S) occurs in the allele that does not harbor the frameshift N616fs* mutation. Our results underscore the importance of performing simultaneous genomic and complementary DNA sequencing when confirming mutations in p97.