DNA replication stress induced by trifluridine determines tumor cell fate according to p53 status

Abstract

words)DNA replication stress is a predominant cause of genome instability, a driver of tumorigenesis and malignant progression. Nucleoside analog-type chemotherapeutic drugs introduce DNA damage and exacerbate DNA replication stress in tumor cells. However, the mechanisms underlying tumor cytotoxicity triggered by the drugs are not fully understood.Here, we show that the fluorinated thymidine analog trifluridine (FTD), an active component of the chemotherapeutic drug trifluridine/tipiracil, delayed DNA synthesis by human replicative DNA polymerases. FTD acted as an inefficient deoxyribonucleotide triphosphate source (FTD triphosphate) and as an obstacle base (trifluorothymine) in the template DNA strand. At the cellular level, FTD decreased thymidine triphosphate in the dNTP pool and induced FTD triphosphate accumulation, resulting in replication fork stalling caused by FTD incorporation into DNA. DNA lesions involving single-stranded DNA were generated as a result of replication fork stalling, and the p53-p21 pathway was activated. Although FTD suppressed tumor cell growth irrespective of p53 status, tumor cell fate diverged at the G2/M phase transition according to p53 status; tumor cells with wild-type p53 underwent cellular senescence via mitosis skip, whereas tumor cells that lost wild-type p53 underwent apoptotic cell death via aberrant late mitosis with severely impaired separation of sister chromatids.These results suggest that DNA replication stress induced by a nucleoside analog-type chemotherapeutic drug triggers tumor cytotoxicity by determining tumor cell fate according to p53 status.Significance: This study identified a unique type of DNA replication stress induced by trifluridine, which directs tumor cell fate either toward cellular senescence or apoptotic cell death according to p53 status.

Monitoring FTD in the peripheral blood mononuclear cells of elderly patients with metastatic colorectal cancer administered FTD plus bevacizumab as first‐line treatment

“…Plasma concentrations of thymidine may affect FTD incorporation, because thymidine concentrations in culture media affect FTD incorporation into human cancer cell lines. 6,12 These variables may determine the percentage of FTDpositive PBMC during the early phase of FTD/TPI treatment and subsequently affect the occurrence of severe hematological adverse events.…”

“…3,4 When FTD is incorporated into the DNA of tumor cells during DNA replication, it exerts antitumor activity 5 and induces DNA replication stress, which suppresses tumor growth irrespective of TP53 mutations. 6,7 Furthermore, the incorporation of FTD into proliferating normal cells may trigger adverse events. In a mouse model, FTD is efficiently incorporated into bone marrow cells, 8 which is associated with hematological toxicity caused by bone marrow suppression (eg, neutropenia or leukopenia), representing the most frequent adverse event of FTD/TPI.…”

The anti-tumor effect of trifluridine via induction of aberrant mitosis is unaffected by mutations modulating p53 activity

“…Under conditions of FTD-induced DNA replication stress, tumor cells expressing wild-type p53 exhibit p53-p21 pathway activation, cyclin B1 degradation during G2 phase, mitotic skipping, and subsequently cellular senescence. However, we have previously shown that mitotic entry, aberrant chromosome segregation, and apoptosis occurred in isogenic p53-null mutant cells (7).…”

“…The triphosphate is then incorporated into DNA strands during DNA replication. Incorporation of FTD into DNA induces retarded replication fork progression (termed DNA replication stress) and the associated cellular response to stress (7,8). Although FTD-induced, p53-status-independent growth suppression has 5 been reported (7,9), its effect was typically determined by different mechanisms in a p53-status-dependent manner.…”

“…Incorporation of FTD into DNA induces retarded replication fork progression (termed DNA replication stress) and the associated cellular response to stress (7,8). Although FTD-induced, p53-status-independent growth suppression has 5 been reported (7,9), its effect was typically determined by different mechanisms in a p53-status-dependent manner. Under conditions of FTD-induced DNA replication stress, tumor cells expressing wild-type p53 exhibit p53-p21 pathway activation, cyclin B1 degradation during G2 phase, mitotic skipping, and subsequently cellular senescence.…”