Chemopreventive effect of leflunomide against Ehrlich's solid tumor grown in mice: Effect on EGF and EGFR expression and tumor proliferation

Leflunomide-induced cardiac injury in adult male mice and bioinformatic approach identifying Nrf2/NF-κb signaling interplay

Leflunomide (LFND) is an immunosuppressive and immunomodulatory disease-modifying antirheumatic drug (DMARD) that was approved for treating rheumatoid arthritis. LFND-induced cardiotoxicity was not fully investigated since its approval. We investigated the cardiac injury in male mice and identified the role of nuclear factor erythroid 2-related factor 2/nuclear factor-κ B (Nrf2/NF-κB) signaling. Male albino mice were assigned into five groups as control, vehicle, and LFND (2.5, 5, and 10 mg/kg). We investigated cardiac enzymes, histopathology, and the mRNA expression of Nrf2, NF-κB, BAX, and tumor necrosis factor-α (TNF-α). The bioinformatic study identified the interaction between LFND and Nrf2/NF-κB signaling; this was confirmed by amelioration in mRNA expression (0.5- to 0.34-fold decrease in Nrf2 and 2.6- to 4.61-fold increases in NF-κB genes) and increased (1.76- and 2.625-fold) serum creatine kinase (CK) and 1.38- and 2.33-fold increases in creatine kinase-MB (CK-MB). Histopathological results confirmed the dose-dependent effects of LFND on cardiac muscle structure in the form of cytoplasmic, nuclear, and vascular changes in addition to increased collagen deposits and apoptosis which were increased compared to controls especially with LFND 10 mg/kg. The current study elicits the dose-dependent cardiac injury induced by LFND administration and highlights, for the first time, dysregulation in Nrf2/NF-κB signaling.

Antitumor activity and targeting p53-PUMA mRNA expression by 5-flurouracil PLGA-lipid polymeric nanoparticles in mouse mammary carcinomas: comparison to free 5-flurouracil

Polymeric poly (lactic-co-glycolic acid) (PLGA)-lipid hybrid nanoparticles (PNPs)-based therapy are powerful carriers for various therapeutic agents. This study was conducted to evaluate the chemotherapeutic potential of free 5-flurouracil (5FU) and synthetized 5FU-PNPs and impact on p53-dependent apoptosis in mammary carcinomas (MCs) grown in mice. Breast cancer cells were injected in Swiss albino female mice and 2 bilateral masses of MC were confirmed after one week. Mice were distributed to five experimental groups; Group 1: MC control group. Groups 2 and 3: MC + free 5FU [5 or 10 mg per kg] groups. Groups 4 and 5: synthetized MC+ 5FU-PNPs [5 or 10 mg per kg] groups. Medications were administered orally, twice weekly for 3 weeks. Then, tumors were dissected, and sections were stained with hematoxylin-eosin (HE) while the other MC was used for measuring of cell death and inflammatory markers. Treatment with 5FU-PNPs suppressed the MC masses and pathologic scores based on HE-staining. Similarly, greater proapoptotic activity was recorded in 5FU-PNPs groups compared to free 5FU groups as shown by significant upregulation in tumoral p53 immunostaining. The current results encourage the utility of PNPs for improving the antitumor effect of 5FU. The chemotherapeutic potential was mediated through enhancement of tumoral p53-mediated p53 up-regulated modulator of apoptosis (PUMA) genes. Additional studies are warranted for testing the antitumor activity of this preparation in other mouse models of breast cancer.

Impact of Synthesized Indoloquinoline Analog to Isolates from Cryptolepis sanguinolenta on Tumor Growth Inhibition and Hepatotoxicity in Ehrlich Solid Tumor-Bearing Female Mice

The study evaluated the antitumor efficacy of APAN, “synthesized indoloquinoline analog derived from the parent neocryptolepine isolated from the roots of Cryptolepis sanguinolenta”, versus the chemotherapeutic drug etoposide (ETO) in Ehrlich solid tumor (EST)-bearing female mice as well as its protective effect against etoposide-triggered hepatic disorders. APAN showed an ameliorative activity against Ehrlich solid tumor and hepatic toxicity, and the greatest improvement was found in the combined treatment of APAN with ETO. The results indicated that EST altered the levels of tumor markers (AFP, CEA, and anti-dsDNA) and liver biomarker function (ALT, AST, ALP, ALB, and T. protein). Furthermore, EST elevated CD68 and anti-survivin proteins immuno-expressions in the solid tumor and liver tissue. Molecular docking studies were demonstrated to investigate their affinity for both TNF-α and topoisomerase II as target proteins, as etoposide is based on the inhibition of topoisomerase II, and TNF-α is quite highly expressed in the solid tumor and liver tissues of EST-bearing animals, which prompted the authors’ interest to explore APAN affinity to its binding site. Treatment of mice bearing EST with APAN and ETO nearly regularized serum levels of the altered parameters and ameliorated the impact of EST on the tissue structure of the liver better than that by treatment with each of them separately.

Lipidic cubic-phase leflunomide nanoparticles (cubosomes) as a potential tool for breast cancer management

Despite the fact of availability of several treatments for breast cancer, most of them fail to attain the desired therapeutic response due to their poor bioavailability, high doses, non-selectivity and as a result systemic toxicity. Here in an attempt made to study the transdermal effect of leflunomide (LEF) against breast cancer. In order to improve the poor physicochemical properties of LEF, it was loaded into cubosomes. Cubosomes were prepared by the emulsification method. Colloidal characteristics of cubosomes including particle size, ζ-potential, entrapment efficiency, in-vitro release profile and ex-vivo permeation were studied. In addition, morphology, stability, cytotoxicity and cell uptake in MDA-MB-231 cell line were carried out for the selected cubosomal formulation. The selected LEF loaded cubosomal formulation showed a small particle size (168 ± 1.08) with narrow size distribution (PI 0.186 ± 0.125) and negative ζ potential (–25.5 ± 0.98). Its Entrapment efficiency (EE%) was 93.2% and showed sustained release profile that extended for 24 h. The selected formulation showed stability when stored at 25 °C for three months in terms of size and EE%. TEM images illustrated the cubic structure of the cubosome. Cell culture results revealed the superiority of LEF cubosomes compared to LEF suspension in their cytotoxic effects with an IC50 close to that of doxorubicin. Furthermore, LEF cell uptake was significantly higher for LEF cubosomes. This may be attributed to the effect of nano-encapsulation on enhancing drug pharmacological effects and uptake indicating the potential usefulness of LEF cubosomes for breast cancer management.

Epigenetic landscape of drug responses revealed through large-scale ChIP-seq data analyses

Background

Elucidating the modes of action (MoAs) of drugs and drug candidate compounds is critical for guiding translation from drug discovery to clinical application. Despite the development of several data-driven approaches for predicting chemical–disease associations, the molecular cues that organize the epigenetic landscape of drug responses remain poorly understood.

Results

With the use of a computational method, we attempted to elucidate the epigenetic landscape of drug responses, in terms of transcription factors (TFs), through large-scale ChIP-seq data analyses. In the algorithm, we systematically identified TFs that regulate the expression of chemically induced genes by integrating transcriptome data from chemical induction experiments and almost all publicly available ChIP-seq data (consisting of 13,558 experiments). By relating the resultant chemical–TF associations to a repository of associated proteins for a wide range of diseases, we made a comprehensive prediction of chemical–TF–disease associations, which could then be used to account for drug MoAs. Using this approach, we predicted that: (1) cisplatin promotes the anti-tumor activity of TP53 family members but suppresses the cancer-inducing function of MYCs; (2) inhibition of RELA and E2F1 is pivotal for leflunomide to exhibit antiproliferative activity; and (3) CHD8 mediates valproic acid-induced autism.

Conclusions

Our proposed approach has the potential to elucidate the MoAs for both approved drugs and candidate compounds from an epigenetic perspective, thereby revealing new therapeutic targets, and to guide the discovery of unexpected therapeutic effects, side effects, and novel targets and actions.

The ponatinib/gossypol novel combination provides enhanced anticancer activity against murine solid Ehrlich carcinoma via triggering apoptosis and inhibiting proliferation/angiogenesis

The search for new antitumor agents or combinations that are more effective and, hopefully, provide fewer health hazards is ongoing. Therefore, this study investigated the efficacy of a novel combination of ponatinib, a multi-targeted tyrosine kinase inhibitor, and the natural phytochemical gossypol against murine solid Ehrlich carcinoma. Six groups of ten mice each received vehicle (I), ponatinib in doses of 10 and 15 mg/kg (II, III) respectively, gossypol in a dose of 4 mg/kg (IV), and ponatinib (10 or 15 mg/kg) in combination with gossypol (4 mg/kg; V, VI). All treatments started on the 12th post-Ehrlich ascites carcinoma (EAC) implantation day and were administered intraperitoneally in daily doses for 3 weeks. Treatment of EAC-bearing mice with ponatinib/gossypol combination improved anticancer efficacy over either drug alone, as demonstrated by greater decreases in tumor weight and volume, and ponatinib (10 mg/kg)/gossypol combination was more efficient than ponatinib (15 mg/kg). Mechanistically, the ponatinib/gossypol combination significantly increased apoptotic markers p53, Bax, and caspase-9 while decreasing anti-apoptotic marker Bcl-2. Furthermore, it greatly decreased proliferative and angiogenic markers, FGFR4 and VEGF, respectively. Histopathology revealed a significant decline in neoplastic cells, the majority of which have necrotic changes and numerous apoptotic bodies, as well as a decrease in mitotic figures and tumor giant cells, indicating the capacity to suppress cancer proliferation/persistence. Overall, gossypol could be used as an adjuvant medication for ponatinib in cancer treatment, possibly leading to successful dose reductions and fewer side effects; however, further research is needed before a clinical application could be feasible.

Nifuroxazide Mitigates Angiogenesis in Ehlrich's Solid Carcinoma: Molecular Docking, Bioinformatic and Experimental Studies on Inhibition of Il-6/Jak2/Stat3 Signaling

Nifuroxazide is an antidiarrheal medication that has promising anticancer activity against diverse types of tumors. The present study tested the anticancer activity of nifuroxazide against Ehrlich’s mammary carcinoma grown in vivo. Furthermore, we investigated the effect of nifuroxazide on IL-6/jak2/STAT3 signaling and the possible impact on tumor angiogenesis. The biological study was supported by molecular docking and bioinformatic predictions for the possible effect of nifuroxazide on this signaling pathway. Female albino mice were injected with Ehrlich carcinoma cells to produce Ehrlich’s solid tumors (ESTs). The experimental groups were as follows: EST control, EST + nifuroxazide (5 mg/kg), and EST + nifuroxazide (10 mg/kg). Nifuroxazide was found to reduce tumor masses (730.83 ± 73.19 and 381.42 ± 109.69 mg vs. 1099.5 ± 310.83) and lessen tumor pathologies. Furthermore, nifuroxazide downregulated IL-6, TNF-α, NFk-β, angiostatin, and Jak2 proteins, and it also reduced tumoral VEGF, as indicated by ELISA and immunohistochemical analysis. Furthermore, nifuroxazide dose-dependently downregulated STAT3 phosphorylation (60% and 30% reductions, respectively). Collectively, the current experiment shed light on the antitumor activity of nifuroxazide against mammary solid carcinoma grown in vivo. The antitumor activity was at least partly mediated by inhibition of IL-6/Jak2/STAT3 signaling that affected angiogenesis (low VEGF and high angiostatin) in the EST. Therefore, nifuroxazide might be a promising antitumor medication if appropriate human studies will be conducted.

Leflunomide Induces Dose-Dependent Lung Injury in Mice via Stimulating Vimentin and NLRP3 Inflammasome Production

Recently, the therapeutic importance of the anti-rheumatic drug, leflunomide, has been increased after the involvement of leflunomide in treating other autoimmune diseases and its promising role in retarding human malignancies. Few studies have focused on the safety in human or animals without clear outlining of the pathologic features on target organs. One clinical study related leflunomide with significant pulmonary complications in predisposed individuals. The current study examined the dose-dependent lung injury produced by leflunomide in healthy mice. Albino mice were allocated into four different groups. Group (1): Vehicle control group, Group (2–4): mice received leflunomide (2.5, 5 or 10 mg/kg), respectively, for 8 weeks and then lungs were dissected from the mice for histopathological examination and fibrosis evaluation (Masson’s trichrome staining and α-smooth muscle actin immunohistochemistry). Enzyme linked immunosorbent assay was used to assess the vimentin and other inflammatory factors in the lung homogenate whereas Western blot analysis was employed to assess α-smooth muscle actin, vimentin and collagen 1. Results indicated that leflunomide induced dose-dependent pulmonary injury and the high dose and increased the vimentin, inflammatory markers (NLRP3 and interlukin-1β). Histologic examination showed distorted architecture, marked inflammatory cells infiltrate and increase collagen content. The findings were supported by Western blotting and the immunohistochemical study which showed greater pulmonary α-smooth muscle actin and vimentin content. In conclusion, the current results highlighted that leflunomide produced dose-dependent pulmonary toxicities that requires further investigation of the nature of injury.

Leflunomide an immunomodulator with antineoplastic and antiviral potentials but drug-induced liver injury: A comprehensive review

Leflunomide (LF) represents the prototype member of dihydroorotate dehydrogenase (DHODH) enzyme inhibitors. DHODH is a mitochondrial inner membrane enzyme responsible for catalytic conversion of dihydroorotate into orotate, a rate-limiting step in the de novo synthesis of the pyrimidine nucleotides. LF produces cellular depletion of pyrimidine nucleotides required for cell growth and proliferation. Based on the affected cells the outcome can be attainable as immunosuppression, antiproliferative, and/or the recently gained attention of the antiviral potentials of LF and its new congeners. Also, protein tyrosine kinase inhibition is an additional mechanistic benefit of LF, which inhibits immunological events such as cellular expansion and immunoglobulin production with an enhanced release of immunosuppressant cytokines. LF is approved for the treatment of autoimmune arthritis of rheumatoid and psoriatic pathogenesis. Also, LF has been used off-label for the treatment of relapsing-remitting multiple sclerosis. However, LF antiviral activity is repurposed and under investigation with related compounds under a phase-I trial as a SARS CoV-2 antiviral in cases with COVID-19. Despite success in improving patients' mobility and reducing joint destruction, reported events of LF-induced liver injury necessitated regulatory precautions. LF should not be used in patients with hepatic impairment or in combination with drugs elaborating a burden on the liver without regular monitoring of liver enzymes and serum bilirubin as safety biomarkers. This study aims to review the pharmacological and safety profile of LF with a focus on the LF-induced hepatic injury from the perspective of pathophysiology and possible protective agents.

Methanolic extracts of a selected Egyptian Vicia faba cultivar mitigate the oxidative/inflammatory burden and afford neuroprotection in a mouse model of Parkinson's disease

Vicia faba L. is a legume from the family Fabaceae. Ancient Egyptians consumed fava beans thousands of years ago and they are still one of the most popular foods in Egypt. The current study examined the anti-Parkinson effect of 80% methanolic extracts of seeds or sprouts of the fava 'Sakha 3 'cultivar which has been selected based on the total phenol content among three cultivars tested. In addition, the extracts were characterized by reversed-phase high-performance liquid chromatography coupled with diode array detection and quadrupole-time-of-flight-mass spectrometry (RP-HPLC-DAD-QTOF-MS). Three doses (200, 400, and 600 mg/kg) of 80% methanol extracts of seeds or sprouts of the Sakha 3 cultivar were evaluated in rotenone-Parkinsonian mice from behavioral, biochemical, and histopathological aspects. The extract of fava sprouts (600 mg/kg dose) showed the most beneficial effect. It improved motor activity, enhanced striatal dopamine level, and decreased the striatal malondialdehyde, as well as the expression of the inflammatory markers, compared with the rotenone control group and groups receiving lower therapeutic doses of the extracts or L-Dopa. In addition, these findings were supported by a histopathological investigation which indicated that mice treated with the 600-mg/kg dose of the sprout extract showed a low number of degenerated neurons. The application of RP-HPLC-DAD-QTOF-MS and mass/mass spectroscopy enabled the metabolic profiling of the sprouts and seeds of the 'Sakha 3' cultivar. It is obvious that germination increased the amounts of phenolic acids, saponins, and aromatic amino acids, together with a dramatic increase in flavonoids. In conclusion, the 80% methanolic extract of sprouts of the fava "Sakha 3" cultivar may be a promising candidate for treating Parkinsonism if appropriate safety data are available.

Synthesis and Antitumor Activity of Doxycycline Polymeric Nanoparticles: Effect on Tumor Apoptosis in Solid Ehrlich Carcinoma

Objectives: The aim of this study was to prepare doxycycline polymeric nanoparticles (DOXY-PNPs) with hope to enhance its chemotherapeutic potential against solid Ehrlich carcinoma (SEC). Methods: Three DOXY-PNPs were formulated by nanoprecipitation method using hydroxypropyl methyl cellulose (HPMC) as a polymer. The prepared DOXY-PNPs were evaluated for the encapsulation efficiency (EE%), the drug loading capacity, particle size, zeta potential (ZP) and the in-vitro release for selection of the best formulation. PNP number 3 was selected for further biological testing based on the best pharmaceutical characters. PNP3 (5 and 10 mg/kg) was evaluated for the antitumor potential against SEC grown in female mice by measuring the tumor mass as well as the expression and immunohistochemical staining for the apoptosis markers; caspase 3 and BAX. Results: The biological study documented the greatest reduction in tumor mass in mice treated with PNP3. Importantly, treatment with 5 mg/kg of DOXY-PNPs produced a similar chemotherapeutic effect to that produced by 10 mg/kg of free DOXY. Further, a significant elevation in mRNA expression and immunostaining for caspase 3 and BAX was detected in mice group treated with DOXY-PNPs. Conclusions: The DOXY-PNPs showed greater antitumor potential against SEC grown in mice and greater values for Spearman’s correlation coefficients were detected when correlation with tumor mass or apoptosis markers was examined; this is in comparison to free DOXY. Hence, DOXY-PNPs should be tested in other tumor types to further determine the utility of the current technique in preparing chemotherapeutic agents and enhancing their properties.

Leflunomide Inhibits Proliferation and Induces Apoptosis via Suppressing Autophagy and PI3K/Akt Signaling Pathway in Human Bladder Cancer Cells

INTRODUCTION

Bladder cancer is a lethal human malignancy. Currently, treatment for bladder cancer is limited. The anti-tumor effects of leflunomide have attracted much more concern in multiple human cancers.

MATERIALS AND METHODS

This study evaluated the anti-tumor effects of leflunomide on cell viability, colony formation, apoptosis, and cell cycle in two human bladder carcinoma cell lines, 5637 and T24. Meanwhile, the underlying mechanism including PI3K/Akt signaling pathway and autophagy modulation was also identified.

RESULTS

Leflunomide markedly inhibited the growth of both bladder cancer cell lines and induced apoptosis and cell cycle arrest in S phase. The phosphorylation levels of Akt and P70S6K in both cell lines were significantly down-regulated with leflunomide treatment. Furthermore, the deceased formation of autophagosomes and the accumulation of LC3II and P62 suggested the blockade of autophagy by leflunomide. Modulation of autophagy with rapamycin and chloroquine markedly attenuated and enhanced the cytostatic effects of leflunomide, respectively.

CONCLUSION

Leflunomide significantly reduced the cell viability of bladder cancer cells via inducing apoptosis and cell cycle arrest and suppressing the PI3K/Akt signaling pathway. In addition, the blockade of autophagy was observed, and autophagy inhibition enhanced leflunomide-mediating anti-tumor effects. Our data presented here offer novel ideas for comprehensive therapeutic regimes on bladder cancer.

Salvianolic Acid B Slows the Progression of Breast Cancer Cell Growth via Enhancement of Apoptosis and Reduction of Oxidative Stress, Inflammation, and Angiogenesis

Breast cancer is the current leading cause of cancer death in females worldwide. Although current chemotherapeutic drugs effectively reduce the progression of breast cancer, most of these drugs have many unwanted side effects. Salvianolic acid B (Sal-B) is a bioactive compound isolated from the root of Danshen Radix with potent antioxidant and anti-inflammatory properties. Since free radicals play a key role in the initiation and progression of tumor cells growth and enhance their metastatic potential, the current study was designed to investigate the antitumor activity of Sal-B and compare it with the antitumor activity of the traditional anticancer drug, cisplatin. In vitro, Sal-B decreased the human breast cancer adenocarcinoma (MCF-7) cells proliferation in a concentration and time dependent manner. In vivo and similar to cisplatin treatment, Sal-B significantly reduced tumor volume and increased the median survival when compared to tumor positive control mice group injected with Ehrlich solid carcinoma cell line (ESC). Sal-B decreased plasma level of malondialdehyde as a marker of oxidative stress and increased plasma level of reduced glutathione (GSH) as a marker of antioxidant defense when compared to control ESC injected mice. Either Sal-B or cisplatin treatment decreased tumor tissue levels of tumor necrosis factor (TNF-α), matrix metalloproteinase-8 (MMP-8), and Cyclin D1 in ESC treated mice. Contrary to cisplatin treatment, Sal-B did not decrease tumor tissue Ki-67 protein in ESC injected mice. Immunohistochemical analysis revealed that Sal-B or cisplatin treatment increased the expression of the apoptotic markers caspase-3 and P53. Although Sal-B or cisplatin significantly reduced the expression of the angiogenic factor vascular endothelial growth factor (VEGF) in ESC injected mice, only Sal-B reduced expression level of COX-2 in ESC injected mice. Our data suggest that Sal-B exhibits antitumor features against breast cancer cells possibly via enhancing apoptosis and reducing oxidative stress, inflammation, and angiogenesis.

Neuroprotective effect of levetiracetam in mouse diabetic retinopathy: Effect on glucose transporter-1 and GAP43 expression

AIMS

Retinopathy is a neurodegenerative complication associating diabetes mellitus. Diabetic retinopathy (DR) is the primary reason of visual loss during early adulthood. DR has a complicated multifactorial pathophysiology initiated by hyperglycaemia-induced ischaemic neurodegenerative retinal changes, followed by vision-threatening consequences. The main therapeutic modalities for DR involve invasive delivery of intravitreal antiangiogenic agents as well as surgical interventions. The current work aimed to explore the potential anti-inflammatory and retinal neuroprotective effects of levetiracetam.

MAIN METHODS

This study was performed on alloxan-induced diabetes in mice (n: 21). After 10 weeks, a group of diabetic animals (n: 7) was treated with levetiracetam (25 mg/kg) for six weeks. Retinal tissues were dissected and paraffin-fixed for examination using (1) morphometric analysis with haematoxylin and eosin (HE), (2) immunohistochemistry (GLUT1, GFAP and GAP43), and (3) RT-PCR-detected expression of retinal inflammatory and apoptotic mediators (TNF-α, IL6, iNOS, NF-κB and Tp53).

KEY FINDINGS

Diabetic mice developed disorganized and debilitated retinal layers with upregulation of the gliosis marker GFAP and downregulation of the neuronal plasticity marker GAP43. Additionally, diabetic retinae showed increased transcription of NF-κB, TNF-α, IL6, iNOS and Tp53. Levetiracetam-treated mice showed downregulation of retinal GLUT1 with relief and regression of retinal inflammation and improved retinal structural organization.

SIGNIFICANCE

Levetiracetam may represent a potential neuroprotective agent in DR. The data presented herein supported an anti-inflammatory role of levetiracetam. However, further clinical studies may be warranted to confirm the effectiveness and safety of levetiracetam in DR patients.

Sericin hydrogels promote skin wound healing with effective regeneration of hair follicles and sebaceous glands after complete loss of epidermis and dermis

Full-thickness skin injury affects millions of people worldwide each year. It often leads to scar formation and loss of skin appendages even after clinical treatment. The majority of wound dressings currently used cannot achieve scarless skin regeneration with complete recovery of appendages such as hair follicles and sebaceous glands. Functional regeneration of these skin appendages is a great challenge. However, we achieved this goal by the successful development and utilization of a photo-crosslinkable sericin hydrogel (SMH) as a new type of wound dressing for repairing full-thickness skin injury. SMH implanted in a mouse full-thickness skin injury model promoted scarless wound healing with effective regeneration of hair follicles and sebaceous glands. By employing techniques of molecular biology, biochemistry, and in vivo cell tracing, we revealed the underlying repair mechanisms: SMH inhibited inflammation, stimulated angiogenesis during healing process, prevented scar tissue formation via regulating the expressions of TGF-β1 and TGF-β3, and recruited mesenchymal stem cells to injury sites for regeneration of skin appendages. Collectively, in this study, we developed a sericin-based hydrogel as a wound dressing for full-thickness skin injury repair, uncovered the functional roles of sericin hydrogels in promoting scarless skin regeneration along with effective recovery of skin appendages, and thus unveiled sericin's potential for skin wound healing.

Revisiting the role of dihydroorotate dehydrogenase as a therapeutic target for cancer

Identified as a hallmark of cancer, metabolic reprogramming allows cancer cells to rapidly proliferate, resist chemotherapies, invade, metastasize, and survive a nutrient-deprived microenvironment. Rapidly growing cells depend on sufficient concentrations of nucleotides to sustain proliferation. One enzyme essential for the de novo biosynthesis of pyrimidine-based nucleotides is dihydroorotate dehydrogenase (DHODH), a known therapeutic target for multiple diseases. Brequinar, leflunomide, and teriflunomide, all of which are potent DHODH inhibitors, have been clinically evaluated but failed to receive FDA approval for the treatment of cancer. Inhibition of DHODH depletes intracellular pyrimidine nucleotide pools and results in cell cycle arrest in S-phase, sensitization to current chemotherapies, and differentiation in neural crest cells and acute myeloid leukemia (AML). Furthermore, DHODH is a synthetic lethal susceptibility in several oncogenic backgrounds. Therefore, DHODH-targeted therapy has potential value as part of a combination therapy for the treatment of cancer. In this review, we focus on the de novo pyrimidine biosynthesis pathway as a target for cancer therapy, and in particular, DHODH. In the first part, we provide a comprehensive overview of this pathway and its regulation in cancer. We further describe the relevance of DHODH as a target for cancer therapy using bioinformatic analyses. We then explore the preclinical and clinical results of pharmacological strategies to target the de novo pyrimidine biosynthesis pathway, with an emphasis on DHODH. Finally, we discuss potential strategies to harness DHODH as a target for the treatment of cancer.

Antitumor activity of a molecularly imprinted nanopreparation of 5-flurouracil against Ehrlich's carcinoma solid tumors grown in mice: Comparison to free 5-flurouracil

Recently, nanotechnology has received great attention in war against cancer. The present study investigated the antitumor efficacy of molecularly imprinted nanopreparation of 5-fluorouracil (nano-5-FU) against Ehrlich ascites carcinoma (EAC) solid tumors grown in mice. Tumor cells were transplanted into female albino mice. Mice were allocated into 5 groups; Group 1: control EAC bearing mice. Groups 2&3: EAC-bearing mice treated orally with 5-FU (5 and 10 mg/kg) twice weekly. Groups 4&5: EAC bearing mice treated with nano-5-FU (5 and 10 mg/kg) twice weekly. Treatment with nano-5-FU showed higher antitumor effect compared to free 5-FU as indicated by enhanced apoptosis and reduction in tumor weight. Additionally, lower number of mitotic figures and greater area for necrosis were observed in the tumor specimens alongside with a decline in the number of intratumoral proliferating nuclei in comparison to free 5-FU. Furthermore, the results showed a significant down-regulation in tumoral expression of caspase-3 and vascular endothelial growth factor. Together, these results further support the potential of using nanotechnology to enhance anticancer efficacy of 5-FU.

Inhibition of canonical WNT/β-catenin signaling is involved in leflunomide (LEF)-mediated cytotoxic effects on renal carcinoma cells

Leflunomide (LEF), an inhibitor of dihydroorotate dehydrogenase (DHODH) in pyrimidine biosynthetic pathway, is an immunomodulatory agent approved for the treatment of rheumatoid arthritis. In this study, we show that LEF significantly reduced cell proliferation of renal carcinoma cells in a concentration-dependent manner. LEF at 50 μM induced S-phase arrest and autophagy. Higher doses of LEF (>50 μM) effectively induced cell apoptosis. Modulating the concentration of LEF resulted in distinct effects on the expression of regulatory proteins associated with cell cycle, apoptosis, and autophagy. In particular, high concentrations of LEF inhibited canonical WNT signaling by promoting nucleo-cytoplasmic shuttling and proteasome-dependent degradation of β-catenin. Mechanistic studies showed that the repression of AKT activation partly accounted for LEF-mediated WNT inhibition. Gene expression microarray revealed that LEF treatment greatly inhibited the expression of FZD10 gene, a receptor mediating WNT/β-catenin activation. In vivo xenograft study in NOD/SCID mice further validated the inhibitory effects of LEF on tumor growth and Wnt/β-catenin signaling. However, LEF treatment also triggered cell autophagy and elevated the expression of WNT3a, which ameliorated its cytotoxic effects. The combination of LEF with a WNT inhibitor IWP-2 or autophagy inhibitor HCQ could yield an enhanced anti-tumor outcome. Taken together, these results identify the potential utility and pharmacological feature of LEF in the chemotherapy of renal cell carcinoma (RCC).

Leflunomide: A promising drug with good antitumor potential

Leflunomide, an inhibitor of dihydroorotase dehydrogenase and thereby pyrimidine synthesis, was approved for treatment of rheumatoid arthritis in 1998. During the following years, leflunomide was used in various preclinical studies as a potential cancer treatment; at the same time, more mechanisms underlying the anticancer effect of leflunomide were identified. Thus, leflunomide has been identified as a potent anticancer drug. This article summarizes the mechanisms as well as results of leflunomide in the evolving field of cancer therapy.

Inhibition of angiogenesis by leflunomide via targeting the soluble ephrin-A1/EphA2 system in bladder cancer

Angiogenesis plays an important role in bladder cancer (BCa). The immunosuppressive drug leflunomide has attracted worldwide attention. However, the effects of leflunomide on angiogenesis in cancer remain unclear. Here, we report the increased expression of soluble ephrin-A1 (sEphrin-A1) in supernatants of BCa cell lines (RT4, T24, and TCCSUP) co-cultured with human umbilical vein endothelial cells (HUVECs) compared with that in immortalized uroepithelial cells (SV-HUC-1) co-cultured with HUVECs. sEphrin-A1 is released from BCa cells as a monomeric protein that is a functional form of the ligand. The co-culture supernatants containing sEphrin-A1 caused the internalization and down-regulation of EphA2 on endothelial cells and dramatic functional activation of HUVECs. This sEphrin-A1/EphA2 system is mainly functional in regulating angiogenesis in BCa tissue. We showed that leflunomide (LEF) inhibited angiogenesis in a N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN)-induced bladder carcinogenesis model and a tumor xenograft model, as well as in BCa cell and HUVEC co-culture systems, via significant inhibition of the sEphrin-A1/EphA2 system. Ephrin-A1 overexpression could partially reverse LEF-induced suppression of angiogenesis and subsequent tumor growth inhibition. Thus, LEF has a significant anti-angiogenesis effect on BCa cells and BCa tissue via its inhibition of the functional angiogenic sEphrin-A1/EphA2 system and may have potential for treating BCa beyond immunosuppressive therapy.

Oxamate potentiates taxol chemotherapeutic efficacy in experimentally-induced solid ehrlich carcinoma (SEC) in mice

Several human cancers including the breast display elevated expression of Lactate dehydrogenase-A (LDH-A), the enzyme that converts pyruvate to lactate and oxidizes NADH to NAD⁺. Indeed, tumor lactate levels correlate with increased metastasis, tumor recurrence, and poor outcome. Lactate also plays roles in promoting tumor inflammation and as a signaling molecule that stimulates tumor angiogenesis. Because of its essential role in cancer metabolism, LDH-A has been considered as a potential target for combination cancer therapy. Therefore, the current study investigated the possible anti-tumor effect of LDH inhibitor (oxamate) in a murine model of breast cancer [Solid Ehrlich Carcinoma (SEC)], alone and in combination with Taxol chemotherapy. The potential underlying mechanisms were also investigated. The results indicated that oxamate induced significant anti-tumor activity against the SEC. Mechanistically, the combination treatment was more efficient than paclitaxel monotherapy in reducing ATP, MDA, TNF-α and Il-17 contents in SEC. Moreover, the apoptotic and anti-angiogenic effects of the combination treatment were triggered more efficiently as compared to paclitaxel monotherapy, Therefore, oxamate may represent a promising agent that enhance the antitumor activity of paclitaxel.