REV3 promotes cellular tolerance to 5-fluorodeoxyuridine by activating translesion DNA synthesis and intra-S checkpoint.

The drug floxuridine (5-fluorodeoxyuridine, FUdR) is an active metabolite of 5-Fluorouracil (5-FU). It converts to 5-fluorodeoxyuridine monophosphate (FdUMP) and 5-fluorodeoxyuridine triphosphate (FdUTP), which on incorporation into the genome inhibits DNA replication. Additionally, it inhibits thymidylate synthase, causing dTMP shortage while increasing dUMP availability, which induces uracil incorporation into the genome. However, the mechanisms underlying cellular tolerance to FUdR are yet to be fully elucidated. In this study, we explored the mechanisms underlying cellular resistance to FUdR by screening for FUdR hypersensitive mutants from a collection of DT40 mutants deficient in each genomic maintenance system. We identified REV3, which is involved in translesion DNA synthesis (TLS), to be a critical factor in FUdR tolerance. Replication using a FUdR-damaged template was attenuated in REV3-/- cells, indicating that the TLS function of REV3 is required to maintain replication on the FUdR-damaged template. Notably, FUdR-exposed REV3-/- cells exhibited defective cell cycle arrest in the early S phase, suggesting that REV3 is involved in intra-S checkpoint activation. Furthermore, REV3-/- cells showed defects in Chk1 phosphorylation, which is required for checkpoint activation, but the survival of FUdR-exposed REV3-/- cells was further reduced by the inhibition of Chk1 or ATR. These data indicate that REV3 mediates DNA checkpoint activation at least through Chk1 phosphorylation, but this signal acts in parallel with ATR-Chk1 DNA damage checkpoint pathway. Collectively, we reveal a previously unappreciated role of REV3 in FUdR tolerance.

Floxuridine supports UPS independent of germline signaling and proteostasis regulators via involvement of detoxification in C. elegans.

The ubiquitin-proteasome system (UPS) is critical for maintaining proteostasis, influencing stress resilience, lifespan, and thermal adaptability in organisms. In Caenorhabditis elegans, specific proteasome subunits and activators, such as RPN-6, PBS-6, and PSME-3, are associated with heat resistance, survival at cold (4°C), and enhanced longevity at moderate temperatures (15°C). Previously linked to improving proteostasis, we investigated the impact of sterility-inducing floxuridine (FUdR) on UPS functionality under proteasome dysfunction and its potential to improve cold survival. Our findings reveal that FUdR significantly enhances UPS activity and resilience during proteasome inhibition or subunit deficiency, supporting worms' normal lifespan and adaptation to cold. Importantly, FUdR effect on UPS activity occurs independently of major proteostasis regulators and does not rely on the germ cells proliferation or spermatogenesis. Instead, FUdR activates a distinct detoxification pathway that supports UPS function, with GST-24 appearing to be one of the factors contributing to the enhanced activity of the UPS upon knockdown of the SKN-1-mediated proteasome surveillance pathway. Our study highlights FUdR unique role in the UPS modulation and its crucial contribution to enhancing survival under low-temperature stress, providing new insights into its mechanisms of action and potential therapeutic applications.

A Modified Floxuridine Reduced-Dose Protocol for Patients with Unresectable Colorectal Liver Metastases Treated with Hepatic Arterial Infusion.

BACKGROUND: Most patients treated with the standard dosing protocol (SDP) of hepatic arterial infusion (HAI) floxuridine require dose holds and reductions, thereby limiting their HAI therapy. We hypothesized that a modified dosing protocol (MDP) with a reduced floxuridine starting dose would decrease dose holds, dose reductions, and have similar potential to convert patients with unresectable colorectal liver metastases (uCRLM) to resection. PATIENTS AND METHODS: We reviewed our institutional database of patients with uCRLM treated with HAI between 2016 and 2022. In 2019, we modified the floxuridine starting dose to 50% (0.06 mg/kg) of the SDP (0.12 mg/kg). We compared treatment related outcomes between the SDP and MDP cohorts. RESULTS: Of n = 33 patients, 15 (45%) were treated on the SDP and 18 (55%) with our new institutional MDP. The MDP cohort completed more cycles before a dose reduction (mean 4.2 vs. 2), received more overall cycles (median 7.5 vs. 5), and averaged 39 more days of treatment (all P < 0.05). The SDP experienced more dose reductions (1.4 vs. 0.61) and dose holds (1.2 vs. 0.2; both P < 0.01). Of the patients in each group potentially convertible to hepatic resection, three patients (23%) in the SDP and six patients (35%) in the MDP group converted to resection (P = 0.691). Overall, four patients (27%) in the SDP developed treatment ending biliary toxicity compared with one patient (6%) in the MDP. CONCLUSIONS: A 50% starting dose of HAI floxuridine provides fewer treatment disruptions, more consecutive floxuridine cycles, and a similar potential to convert patients with initially uCRLM for disease clearance.

Robotic Biliary Stricturoplasty and Roux-en-Y Hepaticojejunostomy After Hepatic Artery Infusion Pump Injury.

BACKGROUND: Hepatic artery infusion pump (HAIP) with floxuridine/dexamethasone and systemic chemotherapy is an established treatment regimen, which had been reported about converting 47% of patients with stage 4 colorectal liver metastasis from unresectable to resectable.1,2 To this effect, HAIP chemotherapy contributes to prolonged survival of many patients, which otherwise may not have other treatment options. Biliary sclerosis, however, is a known complication of the HAIP treatment, which occurs in approximately 5.5% of patients receiving this modality as an adjuvant therapy after hepatectomy and in 2% of patients receiving HAIP treatment for unresectable disease.3 While biliary sclerosis diffusely affects the perihilar and intrahepatic biliary tree, a dominant stricture maybe found in select cases, which gives an opportunity for a local surgical treatment after failure of endoscopic stenting/dilations. While the use of minimally invasive approach to biliary surgery is gradually increasing,4 there have been no descriptions of its application in this scenario. In this video, we demonstrate the use of minimally invasive robotic technique for biliary stricturoplasty and Roux-en-Y (RY) hepaticojejunostomy to treat persistent right hepatic duct stricture after HAIP chemotherapy. PATIENT: A 68-year-old woman with history of multifocal bilobar stage 4 colorectal liver metastasis presented to our office with obstructive jaundice and recurrent cholangitis that required nine endoscopic retrograde cholangiopancreatographies (ERCPs) and a placement of internal-external percutaneous transhepatic biliary drain (PTBD) by interventional radiology within the past 2 years. Her past surgical history was consistent with laparoscopic right hemicolectomy 3 years prior, followed by a left lateral sectorectomy with placement of an HAIP for adjuvant treatment. The patient had more than ten metastatic liver lesions within the right and left lobe, ranging from 2 to 3 cm in size at the time of HAIP placement. The patient had a histologically normal background liver parenchyma before the HAIP chemotherapy treatment. The patient did not have any history of alcohol use, diabetes mellitus, metabolic syndrome, nonalcoholic steatohepatitis, or other underlying intrinsic liver disorders, which are known to contribute to the development of hepatic fibrosis. Despite a radiologically disease-free status, the patient started to have episodes of acute cholangitis 1 year after the placement of HAIP that required multiple admissions to a local hospital. The HAIP was subsequently removed once the diagnosis of biliary sclerosis was made despite dose reductions and treatment with intrahepatic dexamethasone for almost 1 year. In addition to this finding, the known liver metastases have shown complete radiological resolution. Therefore further treatment with HAIP was deemed unnecessary, and pump removal was undertaken. Magnetic resonance imaging showed a dominant stricture at the junction of the right anterior and right posterior sectoral hepatic duct. The location of the dominant stricture was confirmed by an ERCP and cholangioscopy. Absence of neoplasia was confirmed with multiple cholangioscopic biopsies. Multiple endoscopic and percutaneous attempts with stent placement failed to dilate the area of stricture. Postprocedural cholangiographies showed a persistent significant narrowing, which led to multiple recurrent obstructive jaundice and severe cholangitis. While the use of surgical approach is rarely needed in the treatment of biliary sclerosis, a decision was made after extensive multidisciplinary discussions to perform a robotic stricturoplasty and RY hepaticojejunostomy with preservation of the native common bile duct. TECHNIQUE: The operation began with a laparoscopic adhesiolysis to allow for identification of HAIP tubing (which was later removed) and placement of robotic ports. A peripheral liver biopsy was obtained to evaluate the degree of hepatic parenchymal fibrosis. Porta hepatic area was carefully exposed without causing an inadvertent injury to the surrounding hollow organs. Biopsy of perihepatic soft tissues was taken as appropriate to rule out any extrahepatic disease. The common bile duct and common hepatic duct with ERCP stents within it were identified with the use of ultrasonography. Anterior wall of the common hepatic duct was then opened, exposing the two plastic stents. Cephalad extension of the choledochotomy was made toward the biliary bifurcation and the right hepatic duct. The distal common bile duct was preserved for future endoscopic access to the biliary tree. After lowering the right-sided hilar plate, dense fibrosis around the right hepatic duct was divided sharply with robotic scissors, achieving a mechanical release of the dominant stricture. An intraoperative cholangioscopy was performed to confirm adequate openings of the right hepatic duct secondary and tertiary radicles, as well as patency of the left hepatic duct. A 4-Fr Fogarty catheter was used to sweep the potential biliary debris from within the right and left hepatic lobe. Finally, a confirmatory choledochoscopy was performed to ensure patency and clearance of the right-sided intrahepatic biliary ducts and the left hepatic duct before fashioning the hepaticojejunostomy. A 40-cm antecolic roux limb was next prepared for the RY hepaticojejunostomy. A side-to-side double staple technique was utilized to create the jejunojejunostomy. The common enterotomy was closed in a running watertight fashion. Once the roux limb was transposed to the porta hepatic in a tension-free manner, a side-to-side hepaticojejunostomy was constructed in a running fashion by using absorbable barbed sutures. The index suture was placed at 9 o'clock location, and the posterior wall of the anastomosis was run toward 3 o'clock location. This stabilized the roux limb to the bile duct. The anterior wall of the anastomosis was next fashioned by using a running technique from both corners of the anastomosis toward the middle (12 o'clock), where both sutures were tied together. This completed a wide side-to-side hepaticojejunostomy anastomosis encompassing the upper common hepatic duct, biliary bifurcation, and the right hepatic duct. A closed suction drain was placed before closing.5 RESULTS: The operative time was approximately 4 hr with 60 ml of blood loss. The postoperative course was uneventful. The patient was discharged home on postoperative Day 5 after removal of the closed suction drain, confirming the absence of bile leak. The patient had developed periportal/periductal fibrosis, cholestasis, and moderate-severe parenchymal fibrosis (F3-F4) based on liver biopsy, often seen in patients treated with a long course of floxuridine HAIP chemotherapy. The patient is clinically doing well at 1 year outpatient follow-up without any evidence of recurrent cholangitis at the time of this manuscript preparation. CONCLUSIONS: Robotic biliary stricturoplasty with RY hepaticojejunostomy for treatment of biliary sclerosis after HAIP chemotherapy is safe and feasible. Appropriate experience in minimally invasive hepatobiliary surgery is necessary to achieve this goal.

Feeding on lactic acid bacteria isolated from food extends the lifespan of Caenorhabditis elegans.

Lactic acid bacteria (LAB) contribute to human health, and LAB functionality has been studied using Caenorhabditis elegans as an alternative host. However, many studies have focused on the efficacy of a single strain of LAB, and few reports have compared various LAB strains. In this study, we examined the effects of 15 strains of LAB isolated from vegetables, meat, and fermented foods on nematode longevity and healthy lifespan. To reduce the frequency of laborious survival observations, we performed a lifespan assay on agar plates containing 2'-deoxy-5-fluorouridine (FUdR), which inhibits egg hatching and prevents generation mixing. Four beneficial strains showed significant lifespan extension and increased spontaneous nematode mobility, regardless of treatment with or without FUdR and the frequency of survival observation. These results suggested increased longevity and an extended healthy lifespan, confirming the reliability of our method. The four strains are expected to show anti-ageing effects besides longevity and have effects on age-related degenerative diseases. Our labor-saving method can be used as an alternative to conventional methods and enable simultaneous screening of multiple strains. Future research could explore factors contributing to lifespan regulation by comparing and verifying differential strain effects on lifespan.

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.

Enhancing or Quenching of a Mitochondria-Targeted AIEgens-Floxuridine Sensor by the Regulation of pH-Dependent Self-assembly, Efficient Recognition of Hg2+, and Stimulated Response of GSH.

Biocompatible fluorescent probes have emerged as essential tools in life sciences for visualizing subcellular structures and detecting specific analytes. Herein, we report the synthesis and characterization of a novel fluorescent probe (TPE-FdU), incorporated with hydrophilic 2'-fluoro-substituted deoxyuridine and hydrophobic ethynyl tetraphenylethene moieties, which possessed typical aggregation-induced emission (AIE) behavior. In comparison to the TPE-FdU (pKa 7.68) treated in neutral conditions, it performed well at pH 4, exhibiting an enhanced 450 nm emission signal of approximately four times stronger. As the pH value was increased to 10, the fluorescence intensity was completely quenched. The TEM images of TPE-FdU in an acidic environment (nanospherical morphology, AIE enhance, pH = 4) and in a basic environment (microrods, fluorescence quenching, pH = 9) revealed that it was a pH-dependent self-assembled probe, which was also illustrated by the interpretation of the NMR spectrum. Furthermore, the TPE-FdU probe exhibited a specific response to trace Hg2+ ions. Interestingly, the quenched fluorescence of the TPE-FdU probe caused by Hg2+ can be recovered by the addition of GSH due to the formation of the Hg-S bond being released away. MTT assay and CLSM images demonstrated that TPE-FdU was nontoxic and selectively visualized in the intracellular mitochondria. These results contributed to the development of advanced fluorescent probes with diverse applications in cell imaging, environment protection, and biomedical research.

Evaluation of biliary toxicity in patients with hepatic artery infusion pumps.

PURPOSE: Identify risk factors for biliary toxicity in patients with colorectal liver metastases who received floxuridine (FUDR) via a surgically implanted hepatic artery infusion pump (HAIP). Describe the incidence of biliary toxicity and evaluate relevant patterns in the biliary toxicity cohort. METHODS: A single center, retrospective, case-control study included adult colorectal cancer patients with liver metastases who received at least one cycle of FUDR via a surgically implanted HAIP from 1 January 2017, to 1 October 2021. Patients were excluded if they had incomplete records, cholangiocarcinoma diagnosis, or received concurrent mitomycin and FUDR. Biliary toxicity criteria derived from existing HAIP literature were utilized to determine whether patients experienced biliary toxicity. Multiple variables were compared by univariate statistical analysis between the biliary toxicity and non-biliary toxicity cohorts to identify potential risk factors for development of FUDR-induced biliary toxicity. RESULTS: Out of 50 patients who had a HAIP implanted, 39 met the inclusion criteria. Five of the 39 patients (12.7%) included in the analysis met the pre-specified biliary toxicity criteria. No risk factors for biliary toxicity were identified. All five patients who developed biliary toxicity demonstrated elevations in alkaline phosphatase (ALP) prior to meeting the toxicity criteria. CONCLUSION: Biliary toxicity remains a significant and therapy-limiting consequence of FUDR administration. Rising ALP may be an early indicator of subsequent biliary toxicity. Future studies with more patients may identify risk factors that can facilitate risk mitigation strategies.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Floxuridine Oligomers Activated under Hypoxic Environment.

Floxuridine oligomers are anticancer oligonucleotide drugs composed of a number of floxuridine residues. They show enhanced cytotoxicity per floxuridine monomer because the nuclease degradation of floxuridine oligomers directly releases highly active floxuridine monophosphate in cells. However, their clinical use is limited by the low selectivity against cancer cells. To address this limitation, we herein report floxuridine oligomer prodrugs that are active under hypoxia conditions, which is one of the distinguishing features of the microenvironment of all solid tumors. We designed and synthesized two types of floxuridine oligomer prodrugs that possess hypoxia-responsive moieties on nucleobases. The floxuridine oligomer prodrugs showed lower cytotoxicity under normoxia conditions (O2 = 20%), while the parent floxuridine oligomer showed similar anticancer effects under hypoxia conditions (O2 = 1%). The floxuridine oligomer prodrug enabled tumor growth suppression in live mice. This would be the first example demonstrating the conditional control of the medicinal efficacy of oligomerized nucleoside anticancer drugs.

dUTPase inhibition confers susceptibility to a thymidylate synthase inhibitor in DNA-repair-defective human cancer cells.

Deficiency in DNA repair proteins confers susceptibility to DNA damage, making cancer cells vulnerable to various cancer chemotherapies. 5-Fluorouracil (5-FU) is an anticancer nucleoside analog that both inhibits thymidylate synthase (TS) and causes DNA damage via the misincorporation of FdUTP and dUTP into DNA under the conditions of dTTP depletion. However, the role of the DNA damage response to its antitumor activity is still unclear. To determine which DNA repair pathway contributes to DNA damage caused by 5-FU and uracil misincorporation, we examined cancer cells treated with 2'-deoxy-5-fluorouridine (FdUrd) in the presence of TAS-114, a highly potent inhibitor of dUTPase that restricts aberrant base misincorporation. Addition of TAS-114 increased FdUTP and dUTP levels in HeLa cells and facilitated 5-FU and uracil misincorporation into DNA, but did not alter TS inhibition or 5-FU incorporation into RNA. TAS-114 showed synergistic potentiation of FdUrd cytotoxicity and caused aberrant base misincorporation, leading to DNA damage and induced cell death even after short-term exposure to FdUrd. Base excision repair (BER) and homologous recombination (HR) were found to be involved in the DNA repair of 5-FU and uracil misincorporation caused by dUTPase inhibition in genetically modified chicken DT40 cell lines and siRNA-treated HeLa cells. These results suggested that BER and HR are major pathways that protect cells from the antitumor effects of massive incorporation of 5-FU and uracil. Further, dUTPase inhibition has the potential to maximize the antitumor activity of fluoropyrimidines in cancers that are defective in BER or HR.

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.