Predicting Dihydropyrimidine Dehydrogenase Deficiency and Related 5-Fluorouracil Toxicity: Opportunities and Challenges of DPYD Exon Sequencing and the Role of Phenotyping Assays.

Deficiency of dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is associated with severe toxicity induced by the anti-cancer drug 5-Fluorouracil (5-FU). DPYD genotyping of four recommended polymorphisms is widely used to predict toxicity, yet their prediction power is limited. Increasing availability of next generation sequencing (NGS) will allow us to screen rare variants, predicting a larger fraction of DPD deficiencies. Genotype-phenotype correlations were investigated by performing DPYD exon sequencing in 94 patients assessed for DPD deficiency by the 5-FU degradation rate (5-FUDR) assay. Association of common variants with 5-FUDR was analyzed with the SNPStats software. Functional interpretation of rare variants was performed by in-silico analysis (using the HSF system and PredictSNP) and literature review. A total of 23 rare variants and 8 common variants were detected. Among common variants, a significant association was found between homozygosity for the rs72728438 (c.1974+75A>G) and decreased 5-FUDR. Haplotype analysis did not detect significant associations with 5-FUDR. Overall, in our sample cohort, NGS exon sequencing allowed us to explain 42.5% of the total DPD deficiencies. NGS sharply improves prediction of DPD deficiencies, yet a broader collection of genotype-phenotype association data is needed to enable the clinical use of sequencing data.

Hepatic arterial infusion pump chemotherapy combined with systemic therapy for patients with advanced colorectal liver metastases: Outcomes in a newly established program.

BACKGROUND AND OBJECTIVES: Colorectal liver metastasis (CRLM) is a leading cause of morbidity and mortality in patients with colorectal cancer. Hepatic arterial infusion (HAI) chemotherapy has been demonstrated to improve survival in patients with resected CRLM and to facilitate conversion of technically unresectable disease. METHODS: Between 2016 and 2018, n = 22 HAI pumps were placed for CRLM. All patients received systemic chemotherapy concurrently with HAI floxuridine/dexamethasone. Overall survival (OS) and progression-free survival (PFS) were assessed using the Kaplan-Meier method. RESULTS: HAI pumps were placed in seven patients with completely resected CRLM and 15 patients with unresectable disease. Twenty-one patients received HAI floxuridine with a median of 5 total HAI cycles (interquartile range: 4-7). Biliary sclerosis was the most common HAI-related complication (n = 5, 24%). Of the 13 patients treated to convert unresectable CRLM, 3 (23%) underwent hepatic resection with curative intent after a median of 7 HAI cycles (range: 4-10). For all HAI patients, the mean OS was 26.7 months from CRLM diagnosis, while the median PFS and hepatic PFS from pump placement were 9 and 13 months, respectively. CONCLUSION: Concomitant HAI and systemic therapy can be utilized at multidisciplinary programs for patients with advanced CRLM, both in the adjuvant setting and to facilitate conversion of unresectable disease.

Comparison of Hepatic Arterial Infusion Pump Chemotherapy vs Resection for Patients With Multifocal Intrahepatic Cholangiocarcinoma.

Importance: Intrahepatic cholangiocarcinoma (iCCA) is often multifocal (ie, satellites or intrahepatic metastases) at presentation. Objective: To compare the overall survival (OS) of patients with multifocal iCCA after hepatic arterial infusion pump (HAIP) floxuridine chemotherapy vs resection. Design, Setting, and Participants: In this cohort study, patients with histologically confirmed, multifocal iCCA were eligible. The HAIP group consisted of consecutive patients from a single center who underwent HAIP floxuridine chemotherapy for unresectable multifocal iCCA between January 1, 2001, and December 31, 2018. The resection group consisted of consecutive patients from 12 centers who underwent a curative-intent resection for multifocal iCCA between January 1, 1990, and December 31, 2017. Resectable metastatic disease to regional lymph nodes and previous systemic therapy were permitted. Patients with distant metastatic disease (ie, stage IV), those who underwent resection before starting HAIP floxuridine chemotherapy, and those who received a liver transplant were excluded. Data were analyzed on September 1, 2021. Main Outcomes and Measures: Overall survival in the 2 treatment groups was compared using the Kaplan-Meier method and log-rank test. Results: A total of 319 patients with multifocal iCCA were included: 141 in the HAIP group (median [IQR] age, 62 [53-70] years; 79 [56.0%] women) and 178 in the resection group (median [IQR] age, 60 [50-69] years; 91 [51.1%] men). The HAIP group was characterized by a higher percentage of bilobar disease (88.0% [n = 124] vs 34.3% [n = 61]), larger tumors (median, 8.4 cm vs 7.0 cm), and a higher proportion of patients with 4 or more lesions (66.7% [94] vs 24.2% [43]). Postoperative mortality after 30 days was 0.8% (95% CI, 0.0%-2.1%) in the HAIP group vs 6.2% (95% CI, 2.3%-9.7%) in the resection group (P = .01). The median OS for HAIP was 20.3 months vs 18.9 months for resection (P = .32). Five-year OS in patients with 2 or 3 lesions was 23.7% (95% CI, 12.3%-45.7%) in the HAIP group vs 25.7% (95% CI, 17.9%-37.0%) in the resection group. Five-year OS in patients with 4 or more lesions was 5.0% (95% CI, 1.7%-14.3%) in the HAIP group vs 6.8% (95% CI, 1.8%-25.3%) in the resection group. After adjustment for tumor diameter, number of tumors, and lymph node metastases, the hazard ratio of HAIP vs resection was 0.75 (95% CI, 0.55-1.03; P = .07). Conclusions and Relevance: This cohort study found that patients with multifocal iCCA had similar OS after HAIP floxuridine chemotherapy vs resection. Resection of multifocal intrahepatic cholangiocarcinoma needs to be considered carefully given the complication rate of major liver resection; HAIP floxuridine chemotherapy may be an effective alternative option.

Efficacies of FAEV and EMA/CO regimens as primary treatment for gestational trophoblastic neoplasia.

BACKGROUND: Guidelines recommend etoposide, methotrexate, actinomycin D (EMA)/cyclophosphamide, vincristine (CO) as first-line treatment for high-risk gestational trophoblastic neoplasia (GTN). However, the floxuridine, actinomycin D, etoposide and vincristine (FAEV) regimen is commonly used to treat these patients in China. We conducted a randomised controlled trial to compare the efficacies and toxicities of FAEV and EMA/CO. METHODS: Ninety-four patients with GTN were enrolled between May 2015 and April 2019 and randomly assigned to the FAEV or EMA/CO regimen. The rates of complete remission and relapse and the toxicities were compared in August 2021. RESULTS: Five patients were excluded from the analysis. There were 46 patients in the FAEV group and 43 patients in the EMA/CO group. The complete remission rates following primary treatment were 89.1% and 79.1% (P = 0.193), respectively. The relapse rates were 8.7% and 9.3% (P = 0.604). The apparent incidences of grade 4 myelosuppression were 60.9% and 32.6% (P = 0.008), respectively; however, they became both 32.6% (P = 0.996) after granulocyte colony-stimulating factor support. Other adverse reactions were similar in the two groups. No patient died of disease. CONCLUSION: FAEV has comparable efficacy and toxicity to EMA/CO as the primary treatment for high-risk GTN, and may thus be another first-line choice of chemotherapy. CLINICAL TRIAL REGISTRATION: chictr.org.cn: ChiCTR1800017423.

Adjusting the neuron to astrocyte ratio with cytostatics in hippocampal cell cultures from postnatal rats: A comparison of cytarabino furanoside (AraC) and 5-fluoro-2'-deoxyuridine (FUdR).

Cell culture studies offer the unique possibility to investigate the influence of pharmacological treatments with quantified dosages applied for defined time durations on survival, morphological maturation, protein expression and function as well as the mutual interaction of various cell types. Cultures obtained from postnatal rat brain contain a substantial number of glial cells that further proliferate with time in culture leading to an overgrowth of neurons with glia, especially astrocytes and microglia. A well-established method to decrease glial proliferation in vitro is to apply low concentrations of cytosine arabinoside (AraC). While AraC primarily effects dividing cells, it has been reported repeatedly that it is also neurotoxic, which is the reason why most protocols limit its application to concentrations of up to 5 µM for a duration of 24 h. Here, we investigated 5-fluoro-2'-deoxyuridine (FUdR) as a possible substitute for AraC. We applied concentrations of both cytostatics ranging from 4 µM to 75 µM and compared cell composition and cell viability in cultures prepared from 0-2- and 3-4-day old rat pups. Using FUdR as proliferation inhibitor, higher ratios of neurons to glia cells were obtained with a maximal neuron to astrocyte ratio of up to 10:1, which could not be obtained using AraC in postnatal cultures. Patch-clamp recordings revealed no difference in the amplitudes of voltage-gated Na+ currents in neurons treated with FUdR compared with untreated control cells suggesting replacement of AraC by FUdR as glia proliferation inhibitor if highly neuron-enriched postnatal cultures are desired.

Glutathione catabolism by Enterobacteriaceae species to hydrogen sulphide adversely affects the viability of host systems in the presence of 5'fluorodeoxyuridine.

Reduced glutathione (GSH) plays an essential role in relieving oxidative insult from the generation of free radicals via normal physiological processes. However, GSH can be exploited by bacteria as a signalling molecule for the regulation of virulence. We describe findings arising from a serendipitous observation that when GSH and Escherichia coli were incubated with 5'fluorodeoxyuridine (FUdR)-synchronised populations of Caenorhabditis elegans, the nematodes underwent rapid death. Death was mediated by the production of hydrogen sulphide mainly through the action of tnaA, a tryptophanase-encoding gene in E. coli. Other Enterobacteriaceae species possess similar cysteine desulfhydrases that can catabolise l-cysteine-containing compounds to hydrogen sulphide and mediate nematode killing when worms had been pre-treated with FUdR. When colonic epithelial cell lines were infected, hydrogen sulphide produced by these bacteria in the presence of GSH was also able to inhibit ATP synthesis in these cells particularly when cells had been treated with FUdR. Therefore, bacterial production of hydrogen sulphide could act in concert with a commonly used genotoxic cancer drug to exert host cell impairment. Hydrogen sulphide also increases bacterial adhesion to the intestinal cells. These findings could have implications for patients undergoing chemotherapy using FUdR analogues that could result in intestinal damage.

Hepatic Arterial Infusion Pump Chemotherapy for Unresectable Intrahepatic Cholangiocarcinoma: A Systematic Review and Meta-Analysis.

BACKGROUND: Patients with unresectable intrahepatic cholangiocarcinoma (iCCA) have poor survival. This systematic review describes the survival outcomes of hepatic arterial infusion pump (HAIP) chemotherapy with floxuridine for patients with unresectable iCCA. PATIENTS AND METHODS: A literature search was conducted using the electronic databases PubMed, Medline (Ovid), Embase, Web of Science, Google Scholar, and Cochrane to find studies that reported data on the survival of patients with unresectable iCCA treated with HAIP chemotherapy using floxuridine. The quality of the studies was assessed using the Newcastle-Ottawa quality assessment Scale (NOS). Overall survival (OS) was the primary outcome measure, and progression-free survival (PFS), response rates, resection rates, and toxicity were defined as secondary outcome measures. RESULTS: After removing duplicates, 661 publications were assessed, of which nine studies, representing a total of 478 patients, met the inclusion criteria. Three out of nine studies were phase II clinical trials, one study was a prospective dose-escalation study, and the remaining five studies were retrospective cohort studies. After accounting for overlapping cohorts, 154 unique patients were included for pooled analysis. The weighted median OS of patients with unresectable iCCA treated with HAIP chemotherapy with floxuridine was 29.0 months (range 25.0-39 months). The pooled 1-, 2-, 3-, and 5-year OS were 86.4, 55.5, 39.5, and 9.7%, respectively. CONCLUSION: HAIP chemotherapy with floxuridine for patients with unresectable iCCA was associated with a 3-year OS of 39.5%, which is favorable compared with systemic chemotherapy for which no 3-year survivors were reported in the Advanced Biliary Cancer (ABC) trials.

DNA-Damage-Response-Targeting Mitochondria-Activated Multifunctional Prodrug Strategy for Self-Defensive Tumor Therapy.

We report a novel multifunctional construct, M1, designed explicitly to target the DNA damage response in cancer cells. M1 contains both a floxuridine (FUDR) and protein phosphatase 2A (PP2A) inhibitor combined with a GSH-sensitive linker. Further conjugation of the triphenylphosphonium moiety allows M1 to undergo specific activation in the mitochondria, where mitochondria-mediated apoptosis is observed. Moreover, M1 has enormous effects on genomic DNA ascribed to FUDR's primary function of impeding DNA/RNA synthesis combined with diminishing PP2A-activated DNA repair pathways. Importantly, mechanistic studies highlight the PP2A obtrusion in FUDR/5-fluorouracil (5-FU) therapy and underscore the importance of its inhibition to harbor therapeutic potential. HCT116 cell xenograft-bearing mice that have a low response rate to 5-FU show a prominent effect with M1, emphasizing the importance of DNA damage response targeting strategies using tumor-specific microenvironment-activatable systems.

Aptamers Entirely Built from Therapeutic Nucleoside Analogues for Targeted Cancer Therapy.

Owing to the specific and high binding affinity of aptamers to their targets, aptamer-drug conjugates (ApDCs) have emerged as a promising drug delivery system for targeted cancer therapy. However, in a conventional ApDC, the aptamer segment usually just serves as a targeting moiety, and only a limited number of drug molecules are sequentially conjugated to the oligonucleotide, giving a relatively low drug loading capacity. To address this challenge, herein we employ four clinically approved nucleoside analogues, including clofarabine (Clo), ara-guanosine (AraG), gemcitabine (Ge), and floxuridine (FdU), to replace all natural nucleosides in aptamer sequences, generating a series of whole drug-constituted DNA-like oligomers that are termed drugtamers. Similar to their parent aptamers, the obtained drugtamers maintain the targeting capability and can specifically bind to the target receptors overexpressed on the cancer cell surface. With 100% drug loading ratio, active targeting capability, and enzyme-mediated release of active therapeutics, our drugtamers can strongly induce the apoptosis of cancer cells and inhibit the tumor progression, which enables a new potential for a better targeted cancer therapy.

Utilizing the various forms of the gastrocnemius muscle in fix & flap protocol: a reliable remedy for open proximal tibial fractures with accompanying soft tissue defect.

BACKGROUND: Open proximal tibial fractures accompanied by soft tissue loss are substantially challenging to accomplish both bony consolidation and wound healing. The authors retrospectively delineated the utility of the various forms of the gastrocnemius muscle in fix & flap regimen for management of such complicated injuries. METHODS: Thirty-one patients with open fracture accompanied by soft tissue loss of proximal tibia were managed by the protocol of fix & gastrocnemius flap. The collected data included implant for fixation, form of the gastrocnemius flap, postoperative complications, union time, and clinical assessment. RESULTS: According to fixation devices, lateral anatomical locking compression plates were selected in 28 cases, dual plates in 1, and interlocking nails in 2. According to the forms of the gastrocnemius flap, medial gastrocnemius flap was utilized in 22 cases, medial hemigastrocnemius flap in 2, medial myocutaneous gastrocnemius flap in 2, lateral gastrocnemius flap in 3, and combined medial and lateral gastrocnemius flaps in 2. All flaps completely survived without any flap-related complications. Fracture consolidation was established in all patients with an average period of 19.9 weeks (range 16-26). Surgical site infection occurred in 3 cases, and delayed union in 1. By functional score of Puno, 3 cases were determined to be excellent, 27 to be good, and 1 to be fair. CONCLUSION: Concurrent use of internal fixation and gastrocnemius flap reconstruction is a reliable and efficient protocol in managing open fractures with accompanying soft tissue defect of proximal tibia.

Construction of synergistic pH/H2O2-responsive prodrug for prolonging blood circulation and accelerating cellular internalization.

We have developed a real-time and multifunctional doxifluridine-conjugate prodrug (LYX), which involved the preliminary methylfluorescein with 5-fluorouracil linker as protecting group, the targeting biotin unit, and a model therapeutic drug (doxifluridine). The shielding group (5'-DFUR) was found to be effective in prolonging circulation at physiological pH 7.4 and improving accumulation in the acidic microenvironment of the tumor. Based on this strategy, the stability and stimulus responsive properties of prodrug could enhance drug release efficiency and exhibit fewer side effects, thereby providing a unique opportunity for diagnosis and imaging additional analytes or enzymatic activities.

A novel near-infrared theranostic probe for accurate cancer chemotherapy in vivo by a dual activation strategy.

A novel theranostic probe called CX-B-DF is constructed for precise chemotherapy guided by near-infrared (NIR) fluorescence imaging. Moreover, the theranostic probe shows high cytotoxicity to cancer cells under dual activation (H2O2 and TP), which causes the accuracy of drug release to be improved and the toxic side effects to be reduced.

Supramolecular Amphiphiles Based on Pillar[5]arene and Meroterpenoids: Synthesis, Self-Association and Interaction with Floxuridine.

In recent years, meroterpenoids have found wide biomedical application due to their synthetic availability, low toxicity, and biocompatibility. However, these compounds are not used in targeted drug delivery systems due to their high affinity for cell membranes, both healthy and in cancer cells. Using the approach of creating supramolecular amphiphiles, we have developed self-assembling systems based on water-soluble pillar[5]arene and synthetic meroterpenoids containing geraniol, myrtenol, farnesol, and phytol fragments. The resulting systems can be used as universal drug delivery systems. It was shown by turbidimetry that the obtained pillar[5]arene/synthetic meroterpenoid systems do not interact with the model cell membrane at pH = 7.4, but the associates are destroyed at pH = 4.1. In this case, the synthetic meroterpenoid is incorporated into the lipid bilayer of the model membrane. The characteristics of supramolecular self-assembly, association constants and stoichiometry of the most stable pillar[5]arene/synthetic meroterpenoid complexes were established by UV-vis spectroscopy and dynamic light scattering (DLS). It was shown that supramolecular amphiphiles based on pillar[5]arene/synthetic meroterpenoid systems form monodisperse associates in a wide range of concentrations. The inclusion of the antitumor drug 5-fluoro-2'-deoxyuridine (floxuridine) into the structure of the supramolecular associate was demonstrated by DLS, 19F, 2D DOSY NMR spectroscopy.

Results with Floxuridine, Actinomycin D, Etoposide, and Vincristine in Gestational Trophoblastic Neoplasias with International Federation of Gynecology and Obstetrics Scores ≥5.

BACKGROUND: 5-fluorouracil-based multiagent chemotherapy has been used as the primary treatment for high-risk gestational trophoblastic neoplasia (GTN) in China for a few decades. This study aims to assess the efficacy and toxicity of floxuridine, actinomycin D, etoposide, and vincristine (FAEV) as a primary treatment for patients with GTN who had International Federation of Gynecology and Obstetrics (FIGO) scores ≥5. MATERIALS AND METHODS: A total of 207 patients with GTN who had FIGO scores ≥5 were treated with FAEV as first-line chemotherapy at Peking Union Medical College Hospital between January 2002 and December 2017. Complete remission (CR), resistance, survival, toxicity, and reproductive outcomes were analyzed. RESULTS: Of the 207 patients treated with FAEV, 9 (4.3%) required a change of chemotherapy owing to toxicity and 1 (0.5%) died of cerebral hernia 5 weeks after commencing treatment. The remaining 197 patients were assessable to determine the response to FAEV; among them, 168 (85.3%) achieved CR with FAEV and 29 (14.7%) developed resistance to FAEV. The 5-year overall survival rate of the entire cohort was 97.4%. Grade 3-4 neutropenia, thrombocytopenia, and anemia occurred in 28.4%, 6.8%, and 6.2% of cycles, respectively. No acute toxicity-related deaths occurred. Five patients developed acute myeloid leukemia 10-50 months after exposure to chemotherapy; another patient developed duodenal cancer 2 years after completing therapy. Sixty-one patients who preserved fertility wanted to become pregnant; 56 of them conceived. CONCLUSION: The FAEV regimen is an effective primary treatment for patients with GTN who have FIGO scores ≥5 and has predictable and manageable toxicity. IMPLICATIONS FOR PRACTICE: The most commonly used multiagent chemotherapy for high-risk gestational trophoblastic neoplasia (GTN) is etoposide, methotrexate and actinomycin D/cyclophosphamide and vincristine (EMA/CO) worldwide. However, 5-fluorouracil-based multiagent chemotherapy has been used as a primary treatment for high-risk GTN in China for a few decades. This study evaluated the efficacy and toxicity of floxuridine, actinomycin D, etoposide, and vincristine (FAEV) as a primary treatment for patients with GTN who have International Federation of Gynecology and Obstetrics (FIGO) scores ≥5. The study's data demonstrated that FAEV as a primary treatment achieved favorable outcomes for patients with FIGO scores ≥5. Toxicities that result from the FAEV regimen are predictable and manageable. The FAEV regimen may provide another option for the treatment of GTN.

Evaluation of Floxuridine Oligonucleotide Conjugates Carrying Potential Enhancers of Cellular Uptake.

Conjugation of small molecules such as lipids or receptor ligands to anti-cancer drugs has been used to improve their pharmacological properties. In this work, we studied the biological effects of several small-molecule enhancers into a short oligonucleotide made of five floxuridine units. Specifically, we studied adding cholesterol, palmitic acid, polyethyleneglycol (PEG 1000), folic acid and triantennary N-acetylgalactosamine (GalNAc) as potential enhancers of cellular uptake. As expected, all these molecules increased the internalization efficiency with different degrees depending on the cell line. The conjugates showed antiproliferative activity due to their metabolic activation by nuclease degradation generating floxuridine monophosphate. The cytotoxicity and apoptosis assays showed an increase in the anti-cancer activity of the conjugates related to the floxuridine oligomer, but this effect did not correlate with the internalization results. Palmitic and folic acid conjugates provide the highest antiproliferative activity without having the highest internalization results. On the contrary, cholesterol oligomers that were the best-internalized oligomers had poor antiproliferative activity, even worse than the unmodified floxuridine oligomer. Especially relevant is the effect induced by palmitic and folic acid derivatives generating the most active drugs. These results are of special interest for delivering other therapeutic oligonucleotides.

Effects of FUdR on gene expression in the C. elegans bacterial diet OP50.

OBJECTIVE: Many C. elegans aging studies use the compound 5-fluro-2'-deoxyuridine (FUdR) to produce a synchronous population of worms. However, the effects of FUdR on the bacterial gene expression of OP50 E. coli, the primary laboratory C. elegans food source, is not fully understood. This is particularly relevant as studies suggest that intestinal microbes can affect C. elegans physiology. Therefore, it is imperative that we understand how exposure to FUdR can affect gene expression changes in OP50 E. coli. RESULTS: An RNAseq dataset comprised of expression patterns of 2900 E. coli genes in the strain OP50, which were seeded on either nematode growth media (NGM) plates or on FUdR (50 µM) supplemented NGM plates, was analyzed. Analysis showed differential gene expression in genes involved in general transport, amino acid biosynthesis, transcription, iron transport, and antibiotic resistance. We specifically highlight metabolic enzymes in the L-histidine biosynthesis pathway as differentially expressed between NGM and FUdR exposed OP50. We conclude that OP50 exposed to FUdR results in differential expression of many genes, including those in amino acid biosynthetic pathways.

A Randomized Phase II Trial of Adjuvant Hepatic Arterial Infusion and Systemic Therapy With or Without Panitumumab After Hepatic Resection of KRAS Wild-type Colorectal Cancer.

OBJECTIVE/BACKGROUND: The purpose was to determine whether adding Pmab versus no Pmab to an adjuvant regimen of hepatic arterial infusion (HAI) of floxuridine (FUDR) plus systemic (SYS) leucovorin, fluorouracil, and irinotecan (FOLFIRI) improves 15-month recurrence-free survival for patients with RAS wild-type colorectal cancer. Secondary endpoints included overall survival, toxicity, and influence of predictive biomarkers. METHODS: This phase II trial randomized patients with KRAS wild-type resected colorectal liver metastases to adjuvant HAI FUDR + SYS FOLFIRI +/- Pmab (NCT01312857). Patients were stratified by clinical risk score and previous chemotherapy. Based on an exact binomial design, if one arm had ≥24 patients alive and disease-free at 15 months that regimen was considered promising for further investigation. RESULTS: Seventy-five patients were randomized. Patient characteristics and toxicity were not different in the 2 arms, except for rash in +Pmab arm. Grade 3/4 elevation in bilirubin or alkaline phosphatase did not differ in the 2 arms. Twenty-five (69%; 95% CI, 53-82) patients in the Pmab arm versus 18 (47%; 95% CI, 32-63) patients in the arm without Pmab were alive and recurrence-free at 15 months. Only the Pmab arm met the decision rule, while the other arm did not. After median follow-up of 56.6 months, 3-year recurrence-free survival was 57% (95% CI, 43-76) and 42% (95% CI, 29-61), and 3-year overall survival was 97% (95% CI, 90-99) and 91% (95% CI, 83-99), +/- Pmab, respectively. CONCLUSIONS: The addition of Pmab to HAI FUDR + SYS FOLFIRI showed promising activity without increased biliary toxicity and should be further investigated in a larger trial.

Inhibition of Human Uracil DNA Glycosylase Sensitizes a Large Fraction of Colorectal Cancer Cells to 5-Fluorodeoxyuridine and Raltitrexed but Not Fluorouracil.

Previous short-hairpin RNA knockdown studies have established that depletion of human uracil DNA glycosylase (hUNG) sensitizes some cell lines to 5-fluorodeoxyuridine (FdU). Here, we selectively inhibit the catalytic activity of hUNG by lentiviral transduction of uracil DNA glycosylase inhibitor protein into a large panel of cancer cell lines under control of a doxycycline-inducible promoter. This induced inhibition strategy better assesses the therapeutic potential of small-molecule targeting of hUNG. In total, 6 of 11 colorectal lines showed 6- to 70-fold increases in FdU potency upon hUNG inhibition ("responsive"). This hUNG-dependent response was not observed with fluorouracil (FU), indicating that FU does not operate through the same DNA repair mechanism as FdU in vitro. Potency of the thymidylate synthase inhibitor raltitrexed (RTX), which elevates deoxyuridine triphosphate levels, was only incrementally enhanced upon hUNG inhibition (<40%), suggesting that responsiveness is associated with incorporation and persistence of FdU in DNA rather than deoxyuridine. The importance of FU/A and FU/G lesions in the toxicity of FdU is supported by the observation that dT supplementation completely rescued the toxic effects of U/A lesions resulting from RTX, but dT only increased the IC50 for FdU, which forms both FU/A and FU/G mismatches. Contrary to previous reports, cellular responsiveness to hUNG inhibition did not correlate with p53 status or thymine DNA glycosylase expression. A model is suggested in which the persistence of FU/A and FU/G base pairs in the absence of hUNG activity elicits an apoptotic DNA damage response in both responsive and nonresponsive colorectal lines. SIGNIFICANCE STATEMENT: The pyrimidine base 5-fluorouracil is a mainstay chemotherapeutic for treatment of advanced colorectal cancer. Here, this study shows that its deoxynucleoside form, 5-fluorodeoxyuridine (FdU), operates by a distinct DNA incorporation mechanism that is strongly potentiated by inhibition of the DNA repair enzyme human uracil DNA glycosylase. The hUNG-dependent mechanism was present in over 50% of colorectal cell lines tested, suggesting that a significant fraction of human cancers may be sensitized to FdU in the presence of a small-molecule hUNG inhibitor.

Molecular Mechanisms and Tumor Biological Aspects of 5-Fluorouracil Resistance in HCT116 Human Colorectal Cancer Cells.

5-Fluorouracil (5-FU) is a cornerstone drug used in the treatment of colorectal cancer (CRC). However, the development of resistance to 5-FU and its analogs remain an unsolved problem in CRC treatment. In this study, we investigated the molecular mechanisms and tumor biological aspects of 5-FU resistance in CRC HCT116 cells. We established an acquired 5-FU-resistant cell line, HCT116RF10. HCT116RF10 cells were cross-resistant to the 5-FU analog, fluorodeoxyuridine. In contrast, HCT116RF10 cells were collaterally sensitive to SN-38 and CDDP compared with the parental HCT16 cells. Whole-exome sequencing revealed that a cluster of genes associated with the 5-FU metabolic pathway were not significantly mutated in HCT116 or HCT116RF10 cells. Interestingly, HCT116RF10 cells were regulated by the function of thymidylate synthase (TS), a 5-FU active metabolite 5-fluorodeoxyuridine monophosphate (FdUMP) inhibiting enzyme. Half of the TS was in an active form, whereas the other half was in an inactive form. This finding indicates that 5-FU-resistant cells exhibited increased TS expression, and the TS enzyme is used to trap FdUMP, resulting in resistance to 5-FU and its analogs.