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Key Points Since the 1940s, inhibitors of thymidylate biosynthesis have remained among the most effective chemotherapies used in the treatment of cancer The enzyme thymidylate synthase (TS) is a key metabolic bottleneck in the synthesis of thymidine monophosphate required for DNA replication in tumour cells and, therefore, represents an important therapeutic target The molecular consequences of TS inhibition can be complex and vary depending on the type of inhibitor, the tumour type and the expression levels of enzymes involved in drug metabolism Inhibitors of TS fall into two major classes, the fluoropyrimidines and antifolates; these TS-targeted therapies remain the foundation of many combination chemotherapies used in patients with difficult-to-treat cancers The application of existing TS-targeted agents continues to expand, with new approvals of these drugs for the treatment of solid tumours New combination therapeutic strategies have emerged and are entering clinical trials, such as those targeting dUTPase to exploit the uracil-misincorporation pathway and defective DNA repair that occurs during TS inhibition Chemotherapeutic agents targeting thymidylate biosynthesis, and particularly the enzyme thymidylate synthase, have now been key cancer therapies for 60 years. In this article, the classic and novel approaches to targeting this metabolic pathway and strategies for overcoming drug resistance mechanisms are comprehensively reviewed. Over the past 60 years, chemotherapeutic agents that target thymidylate biosynthesis and the enzyme thymidylate synthase (TS) have remained among the most-successful drugs used in the treatment of cancer. Fluoropyrimidines, such as 5-fluorouracil and capecitabine, and antifolates, such as methotrexate and pemetrexed, induce a state of thymidylate deficiency and imbalances in the nucleotide pool that impair DNA replication and repair. TS-targeted agents are used to treat numerous solid and haematological malignancies, either alone or as foundational therapeutics in combination treatment regimens. We overview the pivotal discoveries that led to the rational development of thymidylate biosynthesis as a chemotherapeutic target, and highlight the crucial contribution of these advances to driving and accelerating drug development in the earliest era of cancer chemotherapy. The function of TS as well as the mechanisms and consequences of inhibition of this enzyme by structurally diverse classes of drugs with distinct mechanisms of action are also discussed. In addition, breakthroughs relating to TS-targeted therapies that transformed the clinical landscape in some of the most-difficult-to-treat cancers, such as pancreatic, colorectal and non-small-cell lung cancer, are highlighted. Finally, new therapeutic agents and novel mechanism-based strategies that promise to further exploit the vulnerabilities and target resistance mechanisms within the thymidylate biosynthesis pathway are reviewed.

Background Despite the significant progress made in colon cancer chemotherapy, advanced disease remains largely incurable and novel efficacious chemotherapies are urgently needed. Histone deacetylase inhibitors (HDACi) represent a novel class of agents which have demonstrated promising preclinical activity and are undergoing clinical evaluation in colon cancer. The goal of this study was to identify genes in colon cancer cells that are differentially regulated by two clinically advanced hydroxamic acid HDACi, vorinostat and LBH589 to provide rationale for novel drug combination partners and identify a core set of HDACi-regulated genes. Methods HCT116 and HT29 colon cancer cells were treated with LBH589 or vorinostat and growth inhibition, acetylation status and apoptosis were analyzed in response to treatment using MTS, Western blotting and flow cytometric analyses. In addition, gene expression was analyzed using the Illumina Human-6 V2 BeadChip array and Ingenuity ® Pathway Analysis. Results Treatment with either vorinostat or LBH589 rapidly induced histone acetylation, cell cycle arrest and inhibited the growth of both HCT116 and HT29 cells. Bioinformatic analysis of the microarray profiling revealed significant similarity in the genes altered in expression following treatment with the two HDACi tested within each cell line. However, analysis of genes that were altered in expression in the HCT116 and HT29 cells revealed cell-line-specific responses to HDACi treatment. In addition a core cassette of 11 genes modulated by both vorinostat and LBH589 were identified in both colon cancer cell lines analyzed. Conclusion This study identified HDACi-induced alterations in critical genes involved in nucleotide metabolism, angiogenesis, mitosis and cell survival which may represent potential intervention points for novel therapeutic combinations in colon cancer. This information will assist in the identification of novel pathways and targets that are modulated by HDACi, providing much-needed information on HDACi mechanism of action and providing rationale for novel drug combination partners. We identified a core signature of 11 genes which were modulated by both vorinostat and LBH589 in a similar manner in both cell lines. These core genes will assist in the development and validation of a common gene set which may represent a molecular signature of HDAC inhibition in colon cancer.

Triple-negative breast cancer (TNBC) remains the most lethal breast cancer subtype with poor response rates to the current chemotherapies and a lack of additional effective treatment options. We have identified deoxyuridine 5′-triphosphate nucleotidohydrolase (dUTPase) as a critical gatekeeper that protects tumour DNA from the genotoxic misincorporation of uracil during treatment with standard chemotherapeutic agents commonly used in the FEC regimen. dUTPase catalyses the hydrolytic dephosphorylation of deoxyuridine triphosphate (dUTP) to deoxyuridine monophosphate (dUMP), providing dUMP for thymidylate synthase as part of the thymidylate biosynthesis pathway and maintaining low intracellular dUTP concentrations. This is crucial as DNA polymerase cannot distinguish between dUTP and deoxythymidylate triphosphate (dTTP), leading to dUTP misincorporation into DNA. Targeting dUTPase and inducing uracil misincorporation during the repair of DNA damage induced by fluoropyrimidines or anthracyclines represents an effective strategy to induce cell lethality. dUTPase inhibition significantly sensitised TNBC cell lines to fluoropyrimidines and anthracyclines through imbalanced nucleotide pools and increased DNA damage leading to decreased proliferation and increased cell death. These results suggest that repair of treatment-mediated DNA damage requires dUTPase to prevent uracil misincorporation and that inhibition of dUTPase is a promising strategy to enhance the efficacy of TNBC chemotherapy.

Summary Despite compelling preclinical data in colorectal cancer (CRC), the efficacy of HDACIs has been disappointing in the clinic. The goal of this study was to evaluate the effectiveness of vorinostat and panobinostat in a dose- and exposure-dependent manner in order to better understand the dynamics of drug action and antitumor efficacy. In a standard 72 h drug exposure MTS assay, notable concentration-dependent antiproliferative effects were observed in the IC 50 range of 1.2–2.8 μmol/L for vorinostat and 5.1–17.5 nmol/L for panobinostat. However, shorter clinically relevant exposures of 3 or 6 h failed to elicit any significant growth inhibition and in most cases a >24 h exposure to vorinostat or panobinostat was required to induce a sigmoidal dose–response. Similar results were observed in colony formation assays where ≥24 h of exposure was required to effectively reduce colony formation. Induction of acetyl-H3, acetyl-H4 and p21 by vorinostat were transient and rapidly reversed within 12 h of drug removal. In contrast, panobinostat-induced acetyl-H3, acetyl-H4, and p21 persisted for 48 h after an initial 3 h exposure. Treatment of HCT116 xenografts with panobinostat induced significant increases in acetyl-H3 and downregulation of thymidylate synthase after treatment. Although HDACIs exert both potent growth inhibition and cytotoxic effects when CRC cells were exposed to drug for ≥24 h, these cells demonstrate an inherent ability to survive HDACI concentrations and exposure times that exceed those clinically achievable. Continued efforts to develop novel HDACIs with improved pharmacokinetics/phamacodynamics, enhanced intratumoral delivery and class/isoform-specificity are needed to improve the therapeutic potential of HDACIs and HDACI-based combination regimens in solid tumors.

Lymphedema is mainly caused by lymphatic obstruction and manifested as tissue swelling, often in the arms and legs. Lymphedema is one of the most common post-surgical complications in breast cancer patients and presents a painful and disfiguring chronic illness that has few treatment options. Here, we evaluated the therapeutic potential of interleukin (IL)-8 in lymphatic regeneration independent of its pro-inflammatory activity. We found that IL-8 promoted proliferation, tube formation, and migration of lymphatic endothelial cells (LECs) without activating the VEGF signaling. Additionally, IL-8 suppressed the major cell cycle inhibitor CDKN1C/p57 KIP2 by downregulating its positive regulator PROX1, which is known as the master regulator of LEC-differentiation. Animal-based studies such as matrigel plug and cornea micropocket assays demonstrated potent efficacy of IL-8 in activating lymphangiogenesis in vivo. Moreover, we have generated a novel transgenic mouse model (K14-hIL8) that expresses human IL-8 in the skin and then crossed with lymphatic-specific fluorescent (Prox1-GFP) mouse. The resulting double transgenic mice showed that a stable expression of IL-8 could promote embryonic lymphangiogenesis. Moreover, an immunodeficient IL-8-expressing mouse line that was established by crossing K14-hIL8 mice with athymic nude mice displayed an enhanced tumor-associated lymphangiogenesis. Finally, when experimental lymphedema was introduced, K14-hIL8 mice showed an improved amelioration of lymphedema with an increased lymphatic regeneration. Together, we report that IL-8 can activate lymphangiogenesis in vitro and in vivo with a therapeutic efficacy in post-surgical lymphedema.

Purpose We conducted a phase I/II clinical trial to determine the safety and feasibility of combining vorinostat with 5-fluorouracil (5-FU) in patients with metastatic colorectal cancer (mCRC) and elevated intratumoral thymidylate synthase (TS). Methods Patients with mCRC who had failed all standard therapeutic options were eligible. Intratumoral TS mRNA expression and peripheral blood mononuclear cell (PBMC) histone acetylation were measured before and after 6 consecutive days of vorinostat treatment at 400 mg PO daily. 5-FU/LV were given on days 6 and 7 and repeated every 2 weeks, along with continuous daily vorinostat. Dose escalation occurred in cohorts of three to six patients. Results Ten patients were enrolled. Three dose levels were explored in the phase I portion of the study. Two dose-limiting toxicities (DLTs) were observed at the starting dose level, which resulted in dose de-escalation to levels −1 and −2. Given the occurrence of two DLTs at each of the dose levels, we were unable to establish a maximum tolerated dose (MTD). Two patients achieved significant disease stabilization for 4 and 6 months. Grade 3 and 4 toxicities included fatigue, thrombocytopenia and mucositis. Intratumoral TS downregulation ≥50% was observed in one patient only. Acetylation of histone 3 was observed in PBMCs following vorinostat treatment. Conclusions The study failed to establish a MTD and was terminated. The presence of PBMC histone acetylation indicates biological activity of vorinostat, however, consistent reductions in intratumoral TS mRNA were not observed. Alternate vorinostat dose-scheduling may alleviate the toxicity and achieve optimal TS downregulation.

Survival and response rates in metastatic colorectal cancer remain poor, despite advances in drug development. There is increasing evidence to suggest that gender-specific differences may contribute to poor clinical outcome. We tested the hypothesis that genomic profiling of metastatic colorectal cancer is dependent on gender. A total of 152 patients with metastatic colorectal cancer who were treated with oxaliplatin and continuous infusion 5-fluorouracil were genotyped for 21 polymorphisms in 13 cancer-related genes by PCR. Classification and regression tree analysis tested for gender-related association of polymorphisms with overall survival, progression-free survival and tumor response. Classification and regression tree analysis of all polymorphisms, age and race resulted in gender-specific predictors of overall survival, progression-free survival and tumor response. Polymorphisms in the following genes were associated with gender-specific clinical outcome: estrogen receptor , EGF receptor, xeroderma pigmentosum group D, voltage-gated sodium channel and phospholipase A2. Genetic profiling to predict the clinical outcome of patients with metastatic colorectal cancer may depend on gender.

Lymphedema is mainly caused by lymphatic obstruction and manifested as tissue swelling, often in the arms and legs. Lymphedema is one of the most common post-surgical complications in breast cancer patients and presents a painful and disfiguring chronic illness that has few treatment options. Here, we evaluated the therapeutic potential of interleukin (IL)-8 in lymphatic regeneration independent of its pro-inflammatory activity. We found that IL-8 promoted proliferation, tube formation, and migration of lymphatic endothelial cells (LECs) without activating the VEGF signaling. Additionally, IL-8 suppressed the major cell cycle inhibitor CDKN1C/p57KIP2 by downregulating its positive regulator PROX1, which is known as the master regulator of LEC-differentiation. Animal-based studies such as matrigel plug and cornea micropocket assays demonstrated potent efficacy of IL-8 in activating lymphangiogenesis in vivo. Moreover, we have generated a novel transgenic mouse model (K14-hIL8) that expresses human IL-8 in the skin and then crossed with lymphatic-specific fluorescent (Prox1-GFP) mouse. The resulting double transgenic mice showed that a stable expression of IL-8 could promote embryonic lymphangiogenesis. Moreover, an immunodeficient IL-8-expressing mouse line that was established by crossing K14-hIL8 mice with athymic nude mice displayed an enhanced tumor-associated lymphangiogenesis. Finally, when experimental lymphedema was introduced, K14-hIL8 mice showed an improved amelioration of lymphedema with an increased lymphatic regeneration. Together, we report that IL-8 can activate lymphangiogenesis in vitro and in vivo with a therapeutic efficacy in post-surgical lymphedema.

Systemic sclerosis is a rare disabling autoimmune disease with few treatment options. The efficacy and safety of tocilizumab, an interleukin 6 receptor-α inhibitor, was assessed in the faSScinate phase 2 trial in patients with systemic sclerosis. We did this double-blind, placebo-controlled study at 35 hospitals in Canada, France, Germany, the UK, and the USA. We enrolled adults with progressive systemic sclerosis of 5 or fewer years' duration from first non-Raynaud's sign or symptom. Patients were randomly assigned (1:1) to weekly subcutaneous tocilizumab 162 mg or placebo. The primary endpoint was the difference in mean change from baseline in modified Rodnan skin score at 24 weeks. This study is registered with ClinicalTrials.gov, number NCT01532869. We enrolled 87 patients: 43 assigned to tocilizumab and 44 assigned to placebo. The least squares mean change in modified Rodnan skin score at 24 weeks was −3·92 in the tocilizumab group and −1·22 in the placebo group (difference −2·70, 95% CI −5·85 to 0·45; p=0·0915). The least squares mean change at 48 weeks was −6·33 in the tocilizumab group and −2·77 in the placebo group (treatment difference −3·55, 95% CI −7·23 to 0·12; p=0·0579). In one of several exploratory analyses, fewer patients in the tocilizumab group than in the placebo group had a decline in percent predicted forced vital capacity at 48 weeks (p=0·0373). However, we detected no significant difference in disability, fatigue, itching, or patient or clinician global disease severity. 42 (98%) of 43 patients in the tocilizumab group versus 40 (91%) of 44 in the placebo group had adverse events. 14 (33%) versus 15 (34%) had serious adverse events. Serious infections were more common in the tocilizumab group (seven [16%] of 43 patients) than in the placebo group (two [5%] of 44). One patient died in relation to tocilizumab treatment. Tocilizumab was not associated with a significant reduction in skin thickening. However, the difference was greater in the tocilizumab group than in the placebo group and we found some evidence of less decline in forced vital capacity. The efficacy and safety of tocilizumab should be investigated in a phase 3 trial before definitive conclusions can be made about its risks and benefits. F Hoffmann-La Roche, Genentech.

To update the European League Against Rheumatism (EULAR) recommendations for vaccination in adult patients with autoimmune inflammatory rheumatic diseases (AIIRD) published in 2011. Four systematic literature reviews were performed regarding the incidence/prevalence of vaccine-preventable infections among patients with AIIRD; efficacy, immunogenicity and safety of vaccines; effect of anti-rheumatic drugs on the response to vaccines; effect of vaccination of household of AIIRDs patients. Subsequently, recommendations were formulated based on the evidence and expert opinion. The updated recommendations comprise six overarching principles and nine recommendations. The former address the need for an annual vaccination status assessment, shared decision-making and timing of vaccination, favouring vaccination during quiescent disease, preferably prior to the initiation of immunosuppression. Non-live vaccines can be safely provided to AIIRD patients regardless of underlying therapy, whereas live-attenuated vaccines may be considered with caution. Influenza and pneumococcal vaccination should be strongly considered for the majority of patients with AIIRD. Tetanus toxoid and human papilloma virus vaccination should be provided to AIIRD patients as recommended for the general population. Hepatitis A, hepatitis B and herpes zoster vaccination should be administered to AIIRD patients at risk. Immunocompetent household members of patients with AIIRD should receive vaccines according to national guidelines, except for the oral poliomyelitis vaccine. Live-attenuated vaccines should be avoided during the first 6 months of life in newborns of mothers treated with biologics during the second half of pregnancy. These 2019 EULAR recommendations provide an up-to-date guidance on the management of vaccinations in patients with AIIRD.