DNA Replication Stress Induced by Trifluridine Determines Tumor Cell Fate According to p53 Status

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

The fluorinated thymidine analog trifluridine (FTD) is a chemotherapeutic drug commonly used to treat cancer; however, the mechanism by which FTD induces cytotoxicity is not fully understood. In addition, the effect of gain-of-function (GOF) missense mutations of the TP53 gene (encoding p53), which promote cancer progression and chemotherapeutic drug resistance, on the chemotherapeutic efficacy of FTD is unclear. Here, we revealed the mechanisms by which FTD-induced aberrant mitosis and contributed to cytotoxicity in both p53-null and p53-GOF missense mutant cells. In p53-null mutant cells, FTD-induced DNA double-stranded breaks, single-stranded DNA accumulation, and the associated DNA damage responses during the G2 phase. Nevertheless, FTD-induced DNA damage and the related responses were not sufficient to trigger strict G2/M checkpoint arrest. Thus, these features were carried over into mitosis, resulting in chromosome breaks and bridges, and subsequent cytokinesis failure. Improper mitotic exit eventually led to cell apoptosis, caused by the accumulation of extensive DNA damage and the presence of micronuclei encapsulated in the disrupted nuclear envelope. Upon FTD treatment, the behavior of the p53-GOF-missense mutant, isogenic cell lines, generated by CRISPR/Cas9 genome editing, was similar to that of p53-null mutant cells. Thus, our data suggest that FTD treatment overrode the effect on gene expression induced by p53-GOF mutants and exerted its anti-tumor activity in a manner that was independent of the p53 function.

Combination of ganciclovir and trifluridine prevents drug-resistance emergence in HSV-1

Ocular herpes simplex virus 1 (HSV-1) infections can lead to visual impairment. Long-term acyclovir (ACV) prophylaxis reduces the frequency of recurrences but is associated with drug resistance. Novel therapies are needed to treat drug-resistant HSV-1 infections. Here, we describe the effects of trifluridine (TFT) in combination with ACV or ganciclovir (GCV) on HSV-1 replication and drug-resistance emergence. Wild-type HSV-1 was grown under increasing doses of one antiviral (ACV, GCV, or TFT) or combinations thereof (ACV + TFT or GCV + TFT). Virus cultures were analyzed by Sanger sequencing and deep sequencing of the UL23 [thymidine kinase (TK)] and UL30 [DNA polymerase (DP)] genes. The phenotypes of novel mutations were determined by cytopathic effect reduction assays. TFT showed overall additive anti-HSV-1 activity with ACV and GCV. Five passages under ACV, GCV, or TFT drug pressure gave rise to resistance mutations, primarily in the TK. ACV + TFT and GCV + TFT combinatory pressure induced mutations in the TK and DP. The DP mutations were mainly located in terminal regions, outside segments that typically carry resistance mutations. TK mutations (R163H, A167T, and M231I) conferring resistance to all three nucleoside analogs (ACV, TFT, and GCV) emerged under ACV, TFT, ACV + TFT pressure and under GCV + TFT pressure initiated from suboptimal drug concentrations. However, higher doses of GCV and TFT prevented drug resistance in the resistance selection experiments. In summary, we identified novel mutations conferring resistance to nucleoside analogs, including TFT, and proposed that GCV + TFT combination therapy may be an effective strategy to prevent the development of drug resistance.

Lineage of drug discovery research on fluorinated pyrimidines: chronicle of the achievements accomplished by Professor Setsuro Fujii

Prof. Setsuro Fujii achieved significant results in the field of drug discovery research in Japan. He developed nine well-known drugs: FT, UFT, S-1 and FTD/TPI are anticancer drugs, while cetraxate hydrochloride, camostat mesilate, nafamostat mesilate, gabexate mesilate and pravastatin sodium are therapeutic drugs for various other diseases. He delivered hope to patients with various diseases across the world to improve their condition. Even now, drug discovery research based on Dr. Fujii's ideas is continuing.

Trifluridine-tipiracil plus bevacizumab versus capecitabine plus bevacizumab as first-line treatment for patients with metastatic colorectal cancer ineligible for intensive therapy (SOLSTICE): a randomised, open-label phase 3 study

BACKGROUND

Trifluridine-tipiracil plus bevacizumab has shown efficacy in previous phase 2 studies including patients with unresectable metastatic colorectal cancer. We aimed to investigate first-line trifluridine-tipiracil plus bevacizumab versus capecitabine plus bevacizumab in patients with unresectable metastatic colorectal cancer ineligible for intensive treatment.

METHODS

In this open-label, randomised, phase 3 study, we enrolled patients aged 18 years and older with histologically confirmed metastatic colorectal cancer, ineligible for full-dose doublet or triplet chemotherapy and curative resection across 25 countries and regions. Participants were randomly allocated (1:1) to trifluridine-tipiracil plus bevacizumab or capecitabine plus bevacizumab until disease progression or unacceptable toxicity using an interactive web response system, stratified by Eastern Cooperative Oncology Group (ECOG) performance status (0 vs 1 vs 2), primary tumour location (right vs left colon), and the main reason for not being a candidate for intensive therapy (clinical condition vs non-clinical condition). The primary endpoint was investigator-assessed progression-free survival, defined as the time from randomisation to radiological progression or death from any cause, in the intention-to-treat population. Safety was assessed in all patients having taken at least one dose of the study drug. The trial is ongoing, findings presented here are those of the primary analysis of progression-free survival, conducted after 629 events had occurred. This study is registered with ClinicalTrials.gov, NCT03869892.

FINDINGS

Between March 21, 2019, and Sept 14, 2020, 856 patients (54% male, 46% female) were randomly assigned to trifluridine-tipiracil plus bevacizumab (n=426) or capecitabine plus bevacizumab (n=430). After a median follow-up of 16·6 months (95% CI 16·5-17·1), the hazard ratio for progression-free survival for trifluridine-tipiracil plus bevacizumab versus capecitabine plus bevacizumab was 0·87 (0·75-1·02; p=0·0464; protocol-defined significance level of p=0·021 not met). Investigator-assessed median progression-free survival was 9·4 months (95% CI 9·1-10·9) with trifluridine-tipiracil plus bevacizumab versus 9·3 months (8·9-9·8) with capecitabine plus bevacizumab. The most common grade 3 and higher treatment-emergent adverse events were neutropenia (220 [52%] of 423 patients in the trifluridine-tipiracil plus bevacizumab group vs six [1%] of 427 in the capecitabine plus bevacizumab group), decreased neutrophil count (78 [18%] vs four [<1%]), anaemia (60 [14%] vs 16 [4%]), and hand-foot syndrome (none vs 61 [15%]). Nine deaths (five in the trifluridine-tipiracil plus bevacizumab group and four in the capecitabine plus bevacizumab group) were treatment related.

INTERPRETATION

First-line trifluridine-tipiracil plus bevacizumab was not superior to capecitabine plus bevacizumab in this population. As expected, the safety profile differed between the two treatments, but there were no new safety concerns. Trifluridine-tipiracil plus bevacizumab represents a feasible alternative to capecitabine plus bevacizumab in this population.

FUNDING

Servier International Research Institute, Suresnes, France.

Single-cell transcriptional pharmacodynamics of trifluridine in a tumor-immune model

Understanding the immunological effects of chemotherapy is of great importance, especially now that we have entered an era where ever-increasing pre-clinical and clinical efforts are put into combining chemotherapy and immunotherapy to combat cancer. Single-cell RNA sequencing (scRNA-seq) has proved to be a powerful technique with a broad range of applications, studies evaluating drug effects in co-cultures of tumor and immune cells are however scarce. We treated a co-culture comprised of human colorectal cancer (CRC) cells and peripheral blood mononuclear cells (PBMCs) with the nucleoside analogue trifluridine (FTD) and used scRNA-seq to analyze posttreatment gene expression profiles in thousands of individual cancer and immune cells concurrently. ScRNA-seq recapitulated major mechanisms of action previously described for FTD and provided new insight into possible treatment-induced effects on T-cell mediated antitumor responses.

Replication Stress: A Review of Novel Targets to Enhance Radiosensitivity-From Bench to Clinic

DNA replication is a process fundamental in all living organisms in which deregulation, known as replication stress, often leads to genomic instability, a hallmark of cancer. Most malignant tumors sustain persistent proliferation and tolerate replication stress via increasing reliance to the replication stress response. So whilst replication stress induces genomic instability and tumorigenesis, the replication stress response exhibits a unique cancer-specific vulnerability that can be targeted to induce catastrophic cell proliferation. Radiation therapy, most used in cancer treatment, induces a plethora of DNA lesions that affect DNA integrity and, in-turn, DNA replication. Owing to radiation dose limitations for specific organs and tumor tissue resistance, the therapeutic window is narrow. Thus, a means to eliminate or reduce tumor radioresistance is urgently needed. Current research trends have highlighted the potential of combining replication stress regulators with radiation therapy to capitalize on the high replication stress of tumors. Here, we review the current body of evidence regarding the role of replication stress in tumor progression and discuss potential means of enhancing tumor radiosensitivity by targeting the replication stress response. We offer new insights into the possibility of combining radiation therapy with replication stress drugs for clinical use.

Direct observation of DNA alterations induced by a DNA disruptor

DNA alterations, such as base modifications and mutations, are closely related to the activity of transcription factors and the corresponding cell functions; therefore, detection of DNA alterations is important for understanding their relationships. Particularly, DNA alterations caused by exposure to exogenous molecules, such as nucleic acid analogues for cancer therapy and the corresponding changes in cell functions, are of interest in medicine for drug development and diagnosis purposes. However, detection of comprehensive direct evidence for the relationship of DNA modifications/mutations in genes, their effect on transcription factors, and the corresponding cell functions have been limited. In this study, we utilized a single-molecule electrical detection method for the direct observation of DNA alterations on transcription factor binding motifs upon exposure to a nucleic acid analogue, trifluridine (FTD), and evaluated the effects of the DNA alteration on transcriptional activity in cancer cell line cells. We found ~ 10% FTD incorporation at the transcription factor p53 binding regions in cancer cells exposed to FTD for 5 months. Additionally, through single-molecule analysis of p53-enriched DNA, we found that the FTD incorporation at the p53 DNA binding regions led to less binding, likely due to weaken the binding of p53. This work suggests that single-molecule detection of DNA sequence alterations is a useful methodology for understanding DNA sequence alterations.

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

Trifluridine/tipiracil (FTD/TPI) is an orally administrated anticancer drug with efficacy validated for patients with metastatic colorectal cancer (mCRC) or gastric cancer. FTD, a key component of FTD/TPI, exerts antitumor effects via its incorporation into DNA. Using specific antibodies against bromodeoxyuridine, FTD incorporation into DNA is detected in tumors and peripheral blood mononuclear cells (PBMC) of patients with mCRC who are administered FTD/TPI. The proportion of FTD‐positive PBMC fluctuates according to the schedule of treatment, although the association between the proportion of FTD‐positive PBMC and the clinical outcomes of patients is unknown. To answer this question, here we monitored the FTD‐positive PBMC of 39 elderly patients with mCRC enrolled in KSCC1602, a single‐arm phase 2 trial of FTD/TPI plus bevacizumab as a first‐line treatment, for 1 month, during the first cycle of treatment. The median values and interquartile ranges of the percentage of FTD‐positive PBMC on days 8, 15, and 29 were 39.3% (30.7%‐52.2%), 66.9% (40.0%‐75.3%), and 13.5% (5.7%‐26.0%), respectively. Receiver operating characteristic analysis revealed that the percentage of FTD‐positive PBMC on day 8 (the end of the first week of treatment) had moderate ability to accurately diagnose the occurrence of severe neutropenia and leukopenia within 1 month (area under the curve = 0.778 [95% confidence interval, 0.554‐0.993]). This result suggests that excess FTD incorporation into PBMC at the initial phase of FTD/TPI plus bevacizumab treatment is a risk factor for early onset of severe hematological adverse events.

Efficacy of Combination Chemotherapy Using a Novel Oral Chemotherapeutic Agent, FTD/TPI, with Ramucirumab Murine Version DC101 in a Mouse Syngeneic Cancer Transplantation Model

Trifluridine/tipiracil (FTD/TPI) (a.k.a. TAS-102) is a combination drug for metastatic colorectal cancer (CRC) and severely pretreated metastatic gastric/gastroesophageal junction (GEJ) cancers, comprising FTD, a thymidine-based antineoplastic nucleoside analog, and TPI, which enhances FTD bioavailability. Herein, in KRAS mutant murine colorectal cancer CT26 syngeneic models, we investigate whether combination therapy with DC101 (a surrogate ramucirumab antibody, rat antimouse vascular endothelial growth factor receptor (VEGFR)-2 monoclonal antibody (mAb)) improves FTD/TPI efficacy. Tumor growth inhibition (TGI) on day 15 was 38.0% and 30.6% upon DC101 monotherapy and FTD/TPI monotherapy respectively, and 60.3% upon combination therapy. Tumor volume was significantly lower (p < 0.001) upon combination treatment than upon FTD/TPI or DC101 monotherapy, indicating the additive effects of FTD/TPI and DC101. DNA-incorporated FTD levels on Day 8 were significantly higher in combination therapy with FTD/TPI (for 5 consecutive days) and DC101 (on alternate days for 7days) than in FTD/TPI monotherapy. Furthermore, vascular endothelial cell-specific marker CD31 was downregulated in DC101-treated tumors on day 8. These results indicate that combination therapy with FTD/TPI and DC101 is a promising treatment alternative regardless of KRAS mutations.