Phase II AIDS Malignancy Consortium trial of topical halofuginone in AIDS-related Kaposi sarcoma

Halofuginone for non-hospitalized adult patients with COVID-19 a multicenter, randomized placebo-controlled phase 2 trial. The HALOS trial

BACKGROUND

Halofuginone (PJS-539) is an oral prolyl-tRNA synthetase inhibitor that has a potent in vitro activity against SARS-CoV-2 virus. The safety and efficacy of halofuginone in Covid-19 patients has not been studied.

METHODS

We conducted a phase II, randomized, double-blind, placebo-controlled, dose ranging, safety and tolerability trial of halofuginone in symptomatic (≤ 7 days), mostly vaccinated, non-hospitalized adults with mild to moderate Covid-19. Patients were randomized in a 1:1:1 ratio to receive halofuginone 0.5mg, 1mg or placebo orally once daily for 10 days. The primary outcome was the decay rate of the SARS-CoV-2 viral load logarithmic curve within 10 days after randomization.

RESULTS

From September 25, 2021, to February 3, 2022, 153 patients were randomized. The mean decay rate in SARS-CoV-2 viral load log10 within 10 days was -3.75 (95% CI, -4.11; -3.19) in the placebo group, -3.83 (95% CI, -4.40; -2.27) in the halofuginone 0.5mg group and -4.13 (95% CI, -4.69; -3.57) in the halofuginone 1mg group, with no statistically significant difference in between placebo vs. halofuginone 0.5mg (mean difference -0.08; 95% CI -0.82 to 0.66, p = 0.96) and between placebo vs. halofuginone 1mg (mean difference -0.38; 95% CI, -1.11; 0.36, p = 0.41). There was no difference on bleeding episodes or serious adverse events at 28 days.

CONCLUSIONS

Among non-hospitalized adults with mild to moderate Covid-19 halofuginone treatment was safe and well tolerated but did not decrease SARS-CoV-2 viral load decay rate within 10 days.

Metabolic reprogramming in cancer: Mechanisms and therapeutics

Cancer cells characterized by uncontrolled growth and proliferation require altered metabolic processes to maintain this characteristic. Metabolic reprogramming is a process mediated by various factors, including oncogenes, tumor suppressor genes, changes in growth factors, and tumor-host cell interactions, which help to meet the needs of cancer cell anabolism and promote tumor development. Metabolic reprogramming in tumor cells is dynamically variable, depending on the tumor type and microenvironment, and reprogramming involves multiple metabolic pathways. These metabolic pathways have complex mechanisms and involve the coordination of various signaling molecules, proteins, and enzymes, which increases the resistance of tumor cells to traditional antitumor therapies. With the development of cancer therapies, metabolic reprogramming has been recognized as a new therapeutic target for metabolic changes in tumor cells. Therefore, understanding how multiple metabolic pathways in cancer cells change can provide a reference for the development of new therapies for tumor treatment. Here, we systemically reviewed the metabolic changes and their alteration factors, together with the current tumor regulation treatments and other possible treatments that are still under investigation. Continuous efforts are needed to further explore the mechanism of cancer metabolism reprogramming and corresponding metabolic treatments.

Structure-Guided Design of Halofuginone Derivatives as ATP-Aided Inhibitors Against Bacterial Prolyl-tRNA Synthetase

Aminoacyl-tRNA synthetases (aaRSs) are promising antimicrobial targets due to their essential roles in protein translation, and expanding their inhibitory mechanisms will provide new opportunities for drug discovery. We report here that halofuginone (HF), an herb-derived medicine, moderately inhibits prolyl-tRNA synthetases (ProRSs) from various pathogenic bacteria. A cocrystal structure of Staphylococcus aureus ProRS (SaProRS) with HF and an ATP analog was determined, which guided the design of new HF analogs. Compound 3 potently inhibited SaProRS at IC₅₀ = 0.18 μM and K_d = 30.3 nM and showed antibacterial activities with an MIC of 1-4 μg/mL in vitro. The bacterial drug resistance to 3 only developed at a rate similar to or slower than those of clinically used antibiotics in vitro. Our study indicates that the scaffold and ATP-aided inhibitory mechanism of HF could apply to bacterial ProRS and also provides a chemical validation for using bacterial ProRS as an antibacterial target.

The KEAP1-NRF2 System and Esophageal Cancer

NRF2 (nuclear factor erythroid 2-related factor 2) is a transcription factor that regulates the expression of many cytoprotective genes. NRF2 activation is mainly regulated by KEAP1 (kelch-like ECH-associated protein 1) through ubiquitination and proteasome degradation. Esophageal cancer is classified histologically into two major types: esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). ESCC harbors more genetic alterations in the KEAP-NRF2 system than EAC does, which results in NRF2 activation in these cancers. NRF2-addicted ESCC exhibits increased malignancy and acquisition of resistance to chemoradiotherapy. Therefore, it has been recognized that the development of drugs targeting the KEAP1-NRF2 system based on the molecular dissection of NRF2 function is important and urgent for the treatment of ESCC, along with efficient clinical screening for NRF2-addicted ESCC patients. Recently, the fate of NRF2-activated cells in esophageal tissues, which was under the influence of strong cell competition, and its relationship to the pathogenesis of ESCC, was clarified. In this review, we will summarize the current knowledge of the KEAP1-NRF2 system and the treatment of ESCC. We propose three main strategies for the treatment of NRF2-addicted cancer: (1) NRF2 inhibitors, (2) synthetic lethal drugs for NRF2-addicted cancers, and (3) NRF2 inducers of the host defense system.

Halofuginone micelle nanoparticles eradicate Nrf2-activated lung adenocarcinoma without systemic toxicity

The Keap1-Nrf2 system is the master regulator of the cellular response against oxidative and xenobiotic stresses. Constitutive activation of Nrf2 is frequently observed in various types of cancers. Nrf2 hyperactivation induces metabolic reprogramming in cancer cells, which supports the increased energy demand required for rapid proliferation and confers high-level resistance against anticancer radio/chemotherapy. Hence, Nrf2 inhibition has emerged as an attractive therapeutic strategy to counter such acquired resistance in Nrf2-activated tumors. We previously identified Halofuginone (HF) as a promising Nrf2 inhibitor. In this study, we pursued preclinical characterization of HF and found that while HF markedly reduced the viability of cancer cells, it also caused severe hematopoietic and immune cell suppression in a dose-dependent manner. Hence, to overcome this toxicity, we decided to employ a nanomedicine approach to HF. We found that encapsulation of HF into a polymeric micelle (HF micelle; HFm) largely relieved the systemic toxicity exhibited by free HF while maintaining the tumor-suppressive properties of HF. LC-MS/MS analysis revealed that the reduction in the magnitude of adverse effects was the result of the ability to release HF from the HFm core in a slow and sustained manner. These results thus support the contention that HFm will potentially counteract Nrf2-activated cancers in the clinical settings.

Topical treatments for Kaposi sarcoma: A systematic review

Background

While treatment options exist for solitary or disseminated Kaposi sarcoma (KS) disease, there are currently no standardized clinical treatment guidelines for cutaneous KS.

Objective

This systematic review seeks to identify safe and effective topical treatments for cutaneous KS lesions.

Methods

We conducted a systematic review using peer-reviewed articles from January 1970 to September 2021 published in the PubMed/MEDLINE and EMBASE databases.

Results

From the initial search that yielded 590 studies, 34 met the inclusion criteria and were selected. Of the 34 studies, seven were clinical trials, 26 were case reports/series and one was a multicentre study. A total of 634 patients were included in our review. The three most common topical treatments used for cutaneous KS were imiquimod, alitretinoin and timolol. Topical alitretinoin was used in three case reports and three clinical trials. Topical imiquimod was used in eight case reports, one prospective phase II cohort study and one comparative single-blinded non-controlled clinical study. Topical timolol was used in nine case reports/series. Our review also identified reports of less widely used topical treatments for cutaneous KS. These include topical diphencyprone (DPCP), all-trans-retinoic-acid, rapamycin and bleomycin-dimethylsulfoxide (BLM-DMSO) which achieved variable response rates but have not been widely studied.

Conclusion

Topical alitretinoin, imiquimod and timolol demonstrated positive responses for cutaneous KS and the treatments were well tolerated. These three topical treatment modalities could be considered by clinicians when treating cutaneous KS.

Oncologic Treatment of HIV-Associated Kaposi Sarcoma 40 Years on

The observation in 1981 of the emergence of Kaposi sarcoma (KS) among young men who had sex with men was one of the first harbingers of the HIV epidemic. With advances in HIV care, the incidence of HIV-associated KS (HIV⁺KS) has decreased over time in the United States. However, it remains a persistent malignancy among some HIV-infected populations and is one of the most common tumors in sub-Saharan Africa. Because of the relapsing and remitting nature of this cancer, patients with HIV⁺KS can experience significant, long-term, morbidity. Patients with severe HIV⁺KS may also have concurrent lymphoproliferative syndromes, malignancies, and/or infections that can contribute to mortality. Several chemotherapy agents were explored in clinical trials for HIV⁺KS during the early stage of the epidemic. As HIV⁺KS emerges with CD4 lymphopenia and immunodysregulation, T-cell-sparing options are important to consider. Here, we explore the pathogenesis of HIV⁺KS and the current evidence for immunotherapy and therapies that potentially target KS pathogenesis. This review provides the current landscape of therapies for HIV⁺KS and highlights management issues for patients with HIV and cancer.

Anticarcinogenic effects of halofuginone on lung-derived cancer cells

Malignant mesothelioma is a rare but aggressive form of malignancy, which is difficult to diagnose and is resistant to current chemotherapeutic treatment options. Molecular techniques have been used to investigate the mechanisms of action and the beneficial therapeutic effects of halofuginone (HF) in several cancers but not malignant mesotheliomas. In this study, the antiproliferative and apoptotic effects of HF were investigated through its ability to deregulate EGFR downstream signalling cascade proteins in the pathologically aggressive malignant mesothelioma and non-small-cell lung cancer cells. We showed that administration of HF at nanomolar concentrations induced a dose-dependent reduction in the viability of cancer cells, made cell cycle arrest, inhibited proliferation of cancer cells via STAT3 and ERK1/2 pathways and triggered the apoptotic cascade via p38MAPK. We demonstrated that the apoptotic cell death mechanism was mediated by enhanced activation of caspase-3 and concomitant PARP cleavage, downregulation of Bcl-2 and upregulation of Bax in both malignant mesothelioma and lung cancer cells. In particular, we demonstrated that cancer cells were more sensitive to HF treatment than normal mesothelial cells. Taken together, this study suggests that HF exerts its anticancer effects in lung-derived cancers by targeting signal transduction pathways mainly through deregulation of ERK1/2, STAT3 and p38MAPK to reduce cancer cell viability, induce cell cycle arrest and apoptotic cell death. Thus, HF might be considered as a potential agent against malignant mesothelioma and/or lung cancer cells.

Early pathological signs in young dysf-/- mice are improved by halofuginone

Dysferlinopathies are a non-lethal group of late-onset muscular dystrophies. Here, we evaluated the fusion ability of primary myoblasts from young dysf^-/- mice and the muscle histopathology prior to, and during early stages of disease onset. The ability of primary myoblasts of 5-week-old dysf^-/- mice to form large myotubes was delayed compared to their wild-type counterparts, as evaluated by scanning electron microscopy. However, their fusion activity, as reflected by the presence of actin filaments connecting several cells, was enhanced by the antifibrotic drug halofuginone. Early dystrophic signs were already apparent in 4-week-old dysf^-/- mice; their collagen level was double that in wild-type mice and continued to rise until 5 months of age. Continuous treatment with halofuginone from 4 weeks to 5 months of age reduced muscle fibrosis in a phosphorylated-Smad3 inhibition-related manner. Halofuginone also enhanced myofiber hypertrophy, reduced the percentage of centrally nucleated myofibers, and increased muscle performance. Together, the data suggest an inhibitory effect of halofuginone on the muscle histopathology at very early stages of dysferlinopathy, and enhancement of muscle performance. These results offer new opportunities for early pharmaceutical treatment in dysferlinopathies with favorable outcomes at later stages of life.

Nanosecond pulsed electric fields induce the integrated stress response via reactive oxygen species-mediated heme-regulated inhibitor (HRI) activation

The integrated stress response (ISR) is one of the most important cytoprotective mechanisms and is integrated by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α). Four eIF2α kinases, heme-regulated inhibitor (HRI), double-stranded RNA-dependent protein kinase (PKR), PKR-like endoplasmic reticulum kinase (PERK), and general control nonderepressible 2 (GCN2), are activated in response to several stress conditions. We previously reported that nanosecond pulsed electric fields (nsPEFs) are a potential therapeutic tool for ISR activation. In this study, we examined which eIF2α kinase is activated by nsPEF treatment. To assess the responsible eIF2α kinase, we used previously established eIF2α kinase quadruple knockout (4KO) and single eIF2α kinase-rescued 4KO mouse embryonic fibroblast (MEF) cells. nsPEFs 70 ns in duration with 30 kV/cm electric fields caused eIF2α phosphorylation in wild-type (WT) MEF cells. On the other hand, nsPEF-induced eIF2α phosphorylation was completely abolished in 4KO MEF cells and was recovered by HRI overexpression. CM-H₂DCFDA staining showed that nsPEFs generated reactive oxygen species (ROS), which activated HRI. nsPEF-induced eIF2α phosphorylation was blocked by treatment with the ROS scavenger N-acetyl-L-cysteine (NAC). Our results indicate that the eIF2α kinase HRI is responsible for nsPEF-induced ISR activation and is activated by nsPEF-generated ROS.

Amino acid response by Halofuginone in Cancer cells triggers autophagy through proteasome degradation of mTOR

Background

In the event of amino acid starvation, the cell activates two main protective pathways: Amino Acid starvation Response (AAR), to inhibit global translation, and autophagy, to recover the essential substrates from degradation of redundant self-components. Whether and how AAR and autophagy (ATG) are cross-regulated and at which point the two regulatory pathways intersect remain unknown. Here, we provide experimental evidence that the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) specifically located at the lysosome level links the AAR with the autophagy pathway.

Methods

As an inducer of the AAR, we used halofuginone (HF), an alkaloid that binds to the prolyl-tRNA synthetase thus mimicking the unavailability of proline (PRO). Induction of AAR was determined assessing the phosphorylation of the eukaryotic translation initiation factor (eIF) 2α. Autophagy was monitored by assessing the processing and accumulation of microtubule-associated protein 1 light chain 3 isoform B (LC3B) and sequestosome-1 (p62/SQSTM1) levels. The activity of mTORC1 was monitored through assessment of the phosphorylation of mTOR, (rp)S6 and 4E-BP1. Global protein synthesis was determined by puromycin incorporation assay. mTORC1 presence on the membrane of the lysosomes was monitored by cell fractionation and mTOR expression was determined by immunoblotting.

Results

In three different types of human cancer cells (thyroid cancer WRO cells, ovarian cancer OAW-42 cells, and breast cancer MCF-7 cells), HF induced both the AAR and the autophagy pathways time-dependently. In WRO cells, which showed the strongest induction of autophagy and of AAR, global protein synthesis was little if any affected. Consistently, 4E-BP1 and (rp)S6 were phosphorylated. Concomitantly, mTOR expression and activation declined along with its detachment from the lysosomes and its degradation by the proteasome, and with the nuclear translocation of transcription factor EB (TFEB), a transcription factor of many ATG genes. The extra supplementation of proline rescued all these effects.

Conclusions

We demonstrate that the AAR and autophagy are mechanistically linked at the level of mTORC1, and that the lysosome is the central hub of the cross-talk between these two metabolic stress responses.

Cancer-Associated Fibroblasts Build and Secure the Tumor Microenvironment

Tumor cells reside in a highly complex and heterogeneous tumor microenvironment (TME), which is composed of a myriad of genetically stable non-cancer cells, including fibroblasts, immune cells, endothelial cells, and epithelial cells, and a tumor-specific extracellular matrix (ECM). Cancer-associated fibroblasts (CAFs), as an abundant and active stromal cell population in the TME, function as the signaling center and remodeling machine to aid the creation of a desmoplastic tumor niche. Although there is no denial that the TME and CAFs may have anti-tumor effects as well, a great deal of findings reported in recent years have convincingly revealed the tumor-promoting effects of CAFs and CAF-derived ECM proteins, enzymes, chemical factors and other downstream effectors. While there is growing enthusiasm for the development of CAF-targeting therapies, a better understanding of the complexities of CAF-ECM and CAF-cancer cell interactions is necessary before novel therapeutic strategies targeting the malignant tumor “soil” can be successfully implemented in the clinic.

miR-31 shuttled by halofuginone-induced exosomes suppresses MFC-7 cell proliferation by modulating the HDAC2/cell cycle signaling axis

Traditional Chinese medicine (TCM) are both historically important therapeutic agents and important source of new drugs. Halofuginone (HF), a small molecule alkaloid derived from febrifugine, has been shown to exert strong antiproliferative effects that differ markedly among various cell lines. However, whether HF inhibits MCF-7 cell growth in vitro and underlying mechanisms of this process are not yet clear. Here, we offer the strong evidence of the connection between HF treatment, exosome production and proliferation of MCF-7 cells. Our results showed that HF inhibits MCF-7 cell growth in both time- and dose-dependent manner. Further microRNA (miRNA) profiles analysis in HF treated and nontreated MCF-7 cell and exosomes observed that six miRNAs are particularly abundant and sorted in exosomes. miRNAs knockdown experiment in exosomes and the MCF-7 growth inhibition assay showed that exosomal microRNA-31 (miR-31) modulates MCF-7 cells growth by specially targeting the histone deacetylase 2 (HDAC2), which increases the levels of cyclin-dependent kinases 2 (CDK2) and cyclin D1 and suppresses the expression of p21. In conclusion, these data indicate that inhibition of exosome production reduces exosomal miR-31, which targets the HDAC2 and further regulates the level of cell cycle regulatory proteins, contributing to the anticancer functions of HF. Our data suggest a new role for HF and the exosome production in tumorigenesis and may provide novel insights into prevention and treatment of breast cancer.

Halofuginone Attenuates Osteoarthritis by Rescuing Bone Remodeling in Subchondral Bone Through Oral Gavage

Osteoarthritis (OA) is a common debilitating joint disorder worldwide without effective medical therapy. Articular cartilage and subchondral bone act in concert as a functional unit with the onset of OA. Halofuginone is an analog of the alkaloid febrifugine extracted from the plant Dichroa febrifuga, which has been demonstrated to exert inhibition of SMAD 2/3 phosphorylation downstream of the TGF-β signaling pathway and osteoclastogenesis. To investigate whether halofuginone (HF) alleviates OA after administration by oral gavage, 3-month-old male mice were allocated to the Sham group, vehicle-treated anterior cruciate ligament transection (ACLT) group, and HF-treated ACLT group. The immunostaining analysis indicated that HF reduced the number of matrix metalloproteinase 13 (MMP-13) and collagen X (Col X) positive cells in the articular cartilage. Moreover, HF lowered histologic OA score and prevented articular cartilage degeneration. The micro-computed tomography (μCT) scan showed that HF maintained the subchondral bone microarchitecture, demonstrated by the restoration of bone volume fraction (BV/TV), subchondral bone plate thickness (SBP.Th.), and trabecular pattern factor (Tb.Pf) to a level comparable to that of the Sham group. Immunostaining for CD31 and μCT based angiography showed that the number and volume of vessels in subchondral bone was restored by HF. HF administered by oral gavage recoupled bone remodeling and inhibited aberrant angiogenesis in the subchondral bone, further slowed the progression of OA. Therefore, HF administered by oral gavage could be a potential therapy for OA.

Aminoacyl-tRNA synthetases: Structure, function, and drug discovery

Aminoacyl-tRNA synthetases (AARSs) are the enzymes that catalyze the aminoacylation reaction by covalently linking an amino acid to its cognate tRNA in the first step of protein translation. Beyond this classical function, these enzymes are also known to have a role in several metabolic and signaling pathways that are important for cell viability. Study of these enzymes is of great interest to the researchers due to its pivotal role in the growth and survival of an organism. Further, unfolding the interesting structural and functional aspects of these enzymes in the last few years has qualified them as a potential drug target against various diseases. Here we review the classification, function, and the conserved as well the appended structural architecture of these enzymes in detail, including its association with multi-synthetase complexes. We also considered their role in human diseases in terms of mutations and autoantibodies against AARSs. Finally, we have discussed the available inhibitors against AARSs. This review offers comprehensive information on AARSs under a single canopy that would be a good inventory for researchers working in this area.

Halofuginone inhibits TGF-β/BMP signaling and in combination with zoledronic acid enhances inhibition of breast cancer bone metastasis

More efficient therapies that target multiple molecular mechanisms are needed for the treatment of incurable bone metastases. Halofuginone is a plant alkaloid-derivative with antiangiogenic and antiproliferative effects. Here we demonstrate that halofuginone is an effective therapy for the treatment of bone metastases, through multiple actions that include inhibition of TGFβ and BMP-signaling.

Halofuginone blocked TGF-β-signaling in MDA-MB-231 and PC3 cells showed by inhibition of TGF-β–induced Smad-reporter, phosphorylation of Smad-proteins, and expression of TGF-β-regulated metastatic genes. Halofuginone increased inhibitory Smad7-mRNA and reduced TGF-β-receptor II protein. Proline supplementation but not Smad7-knockdown reversed halofuginone-inhibition of TGF-β-signaling. Halofuginone also decreased BMP-signaling. Treatment of MDA-MB-231 and PC3 cells with halofuginone reduced the BMP-Smad-reporter (BRE)₄, Smad1/5/8-phosphorylation and mRNA of the BMP-regulated gene Id-1. Halofuginone decreased immunostaining of phospho-Smad2/3 and phospho-Smad1/5/8 in cancer cells in vivo.

Furthermore, halofuginone decreased tumor-take and growth of orthotopic-tumors. Mice with breast or prostate bone metastases treated with halofuginone had significantly less osteolysis than control mice. Combined treatment with halofuginone and zoledronic-acid significantly reduced osteolytic area more than either treatment alone. Thus, halofuginone reduces breast and prostate cancer bone metastases in mice and combined with treatment currently approved by the FDA is an effective treatment for this devastating complication of breast and prostate-cancer.

Halofuginone enhances the chemo-sensitivity of cancer cells by suppressing NRF2 accumulation

The KEAP1-NRF2 system regulates the cellular defence against oxidative and xenobiotic stresses. NRF2 is a transcription factor that activates the expression of cytoprotective genes encoding antioxidative, detoxifying and metabolic enzymes as well as transporters. Under normal conditions, KEAP1 represses NRF2 activity by degrading the NRF2 protein. When cells are exposed to stresses, KEAP1 stops promoting NRF2 degradation, and NRF2 rapidly accumulates and activates the transcription of target genes. Constitutive accumulation of NRF2 via a variety of mechanisms that disrupt KEAP1-mediated NRF2 degradation has been observed in various cancer types. Constitutive NRF2 accumulation confers cancer cells with a proliferative advantage as well as resistance to anti-cancer drugs and radiotherapies. To suppress the chemo- and radio-resistance of cancer cells caused by NRF2 accumulation, we conducted high-throughput chemical library screening for NRF2 inhibitors and identified febrifugine derivatives. We found that application of the less-toxic derivative halofuginone in a low dose range rapidly reduced NRF2 protein levels. Halofuginone induced a cellular amino acid starvation response that repressed global protein synthesis and rapidly depleted NRF2. Halofuginone treatment ameliorated the resistance of NRF2-addicted cancer cells to anti-cancer drugs both in vitro and in vivo. These results provide preclinical proof-of-concept evidence for halofuginone as an NRF2 inhibitor applicable to treatment of chemo- and radio-resistant forms of cancer.

Anticancer activity of halofuginone in a preclinical model of osteosarcoma: inhibition of tumor growth and lung metastases

Osteosarcoma is the main malignant primary bone tumor in children and adolescents for whom the prognosis remains poor, especially when metastases are present at diagnosis. Because we recently demonstrated that TGF-β/Smad cascade plays a crucial role in osteosarcoma metastatic progression, we investigated the effect of halofuginone, identified as an inhibitor of the TGF-β/Smad3 cascade, on osteosarcoma progression. A preclinical model of osteosarcoma was used to evaluate the impact of halofuginone on tumor growth, tumor microenvironment and metastasis development. In vivo experiments showed that halofuginone reduces primary tumor growth and lung metastases development. In vitro experiments demonstrated that halofuginone decreases cell viability mainly by its ability to induce caspase-3 dependent cell apoptosis. Moreover, halofuginone inhibits the TGF-β/Smad3 cascade and the response of TGF-β key targets involved in the metastases dissemination process such as MMP-2. In addition, halofuginone treatment affects the “vicious cycle” established between tumor and bone cells, and therefore the tumor-associated bone osteolysis. Together, these results demonstrate that halofuginone decreased primary osteosarcoma development and associated lung metastases by targeting both the tumor cells and the tumor microenvironment. Using halofuginone may be a promising therapeutic strategy against tumor progression of osteosarcoma specifically against lung metastases dissemination.

Halofuginone suppresses growth of human uterine leiomyoma cells in a mouse xenograft model

STUDY QUESTION

Does halofuginone (HF) inhibit the growth of human uterine leiomyoma cells in a mouse xenograft model?

SUMMARY ANSWER

HF suppresses the growth of human uterine leiomyoma cells in a mouse xenograft model through inhibiting cell proliferation and inducing apoptosis.

WHAT IS KNOWN ALREADY

Uterine leiomyomas are the most common benign tumors of the female reproductive tract. HF can suppress the growth of human uterine leiomyoma cells in vitro. The mouse xenograft model reflects the characteristics of human leiomyomas.

STUDY DESIGN, SIZE, DURATION

Primary leiomyoma smooth muscle cells from eight patients were xenografted under the renal capsule of adult, ovariectomized NOD-scid IL2Rγ(null) mice (NSG). Mice were treated with two different doses of HF or vehicle for 4 weeks with six to eight mice per group.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Mouse body weight measurements and immunohistochemical analysis of body organs were carried out to assess the safety of HF treatment. Xenografted tumors were measured and analyzed for cellular and molecular changes induced by HF. Ovarian steroid hormone receptors were evaluated for possible modulation by HF.

MAIN RESULTS AND THE ROLE OF CHANCE

Treatment of mice carrying human UL xenografts with HF at 0.25 or 0.50 mg/kg body weight for 4 weeks resulted in a 35-40% (P < 0.05) reduction in tumor volume. The HF-induced volume reduction was accompanied by increased apoptosis and decreased cell proliferation. In contrast, there was no significant change in the collagen content either at the transcript or protein level between UL xenografts in control and HF groups. HF treatment did not change the expression level of ovarian steroid hormone receptors. No adverse pathological effects were observed in other tissues from mice undergoing treatment at these doses.

LIMITATIONS, REASONS FOR CAUTION

While this study did test the effects of HF on human leiomyoma cells in an in vivo model, HF was administered to mice whose tolerance and metabolism of the drug may differ from that in humans. Also, the longer term effects of HF treatment are yet unclear.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study showing the effectiveness of HF in reducing UL tumor growth by interfering with the main cellular processes regulating cell proliferation and apoptosis are in agreement with previous studies on the effects of HF on other fibrotic diseases. HF can be considered as a candidate for reducing the size of leiomyomas, particularly prior to surgery.

STUDY FUNDING/COMPETING INTERESTS

This project was funded by NIH PO1HD057877 and R01 HD064402. Authors report no competing interests.

Kaposi's sarcoma: a 10-year experience with 248 patients at a single tertiary care hospital in Tanzania

BACKGROUND

Kaposi's Sarcoma is the most common sarcoma and second most prevalent cancer seen in Tanzania. Little is known about Kaposi's sarcoma in our setting as there is paucity of recent published data regarding this condition. This study describes the clinicopathological pattern and treatment outcome of Kaposi's sarcoma at Bugando Medical Centre, a tertiary care hospital in northwestern Tanzania.

METHODS

This was a prospective study of histologically confirmed Kaposi's sarcoma that was conducted at Bugando Medical Center between July 2004 and June 2014.

RESULTS

A total of 248 patients (M:F = 1.4:1) representing 2.4% of all malignancies during the study period were enrolled into the study. The median age at presentation was 36 years. Females were younger than males (p = 0.04). Out of 248 patients, 122 (49.2%) were HIV positive. Of these, 46 (37.7%) were males and 76 (62.3%) females. AIDS-related Kaposi's sarcoma were younger than HIV negative Kaposi's sarcoma patients (p = 0.011). Median duration of symptoms was 6 months. Kaposi's sarcoma was the AIDS defining disease in 82 (67.2%) patients while in the remaining 40 (32.8%) it was diagnosed between 1 and 14 months after the initial diagnosis of AIDS. The lower limb was most frequently involved site in 28.9% of patient. Females had more disseminated lesions compared with more localized lesions in the males (p = 0.001). The treatment modalities in this study included chemotherapy, radiotherapy, surgery and highly active antiretroviral therapy. Overall 126 (53.4%) patients had significant improvement in quality of life at the end of 1 year follow up. Treatment related complication and mortality rates were 25.8 and 24.2% respectively. Poor ACTG stage, CD4+ count <200 cells/µl, associated co-morbid illness, disseminated disease and poor adherent to chemotherapy were the significant independent factors associated with deaths (p < 0.001). Patient's follow-up was generally poor and data on long-term survivals were not available as more than two-thirds of patients were lost to follow up.

CONCLUSION

Kaposi's sarcoma is the most common malignant vascular tumor and HIV/AIDS- related cancer in our region. There is an urgent need to develop health education programmes to enhance the understanding of this disease and how it spreads, particularly among the younger generation.

Halofuginone - the multifaceted molecule

Halofuginone is an analog of febrifugine-an alkaloid originally isolated from the plant Dichroa febrifuga. During recent years, halofuginone has attracted much attention because of its wide range of beneficial biological activities, which encompass malaria, cancer, and fibrosis-related and autoimmune diseases. At present two modes of halofuginone actions have been described: (1) Inhibition of Smad3 phosphorylation downstream of the TGFβ signaling pathway results in inhibition of fibroblasts-to-myofibroblasts transition and fibrosis. (2) Inhibition of prolyl-tRNA synthetase (ProRS) activity in the blood stage of malaria and inhibition of Th17 cell differentiation thereby inhibiting inflammation and the autoimmune reaction by activation of the amino acid starvation and integrated stress responses. This review deals with the history and origin of this natural product, its synthesis, its known modes of action, and it's various biological activities in pre-clinical animal models and in humans.

Plant-derived anticancer agents: a promising treatment for bone metastasis

Bone metastasis is a very frequent complication of advanced cancer, and it remains an incurable disease. Current therapies that have been approved for the treatment of bone metastases delay the occurrence of skeletal-related events and can extend the patient's lifespan by a few years. However, they will not cure or cause the regression of established bone metastases, and new side effects are emerging after prolonged treatment. Thus, new therapies are severely needed. There are compelling evidences from in vitro and in vivo preclinical studies that support the use of compounds derived from plants to treat several forms of cancers including bone metastasis. More than 25% of the drugs used during the past 20 years were directly derived from plants, whereas another 25% are chemically altered natural products. Still, only 5-15% of the ∼250 000 higher plants have ever been investigated for bioactive compounds. There is a growing interest for the study of anticancer drugs with relatively low side effects that target specific key signaling pathways that control the establishment and progression of the cancer metastasis. Therefore, further studies are needed to identify new natural compounds with high efficiency in cancer prevention and treatment. Extensive reviews about plant-derived agents and their use in cancer have been published, but none when it comes to the treatment of bone metastases. Only a few of these compounds have been evaluated for the treatment of bone metastasis; here we describe some of the most prominent ones that are having the potential to reach the clinic soon.

Halofuginone ameliorates autoimmune arthritis in mice by regulating the balance between Th17 and Treg cells and inhibiting osteoclastogenesis

OBJECTIVE

The small molecule halofuginone has been shown to inhibit fibrosis, angiogenesis, and tumor progression. This study was undertaken to evaluate the effects of halofuginone in preventing autoimmune arthritis in mice.

METHODS

The effects of halofuginone on joint diseases were assessed by clinical scoring and histologic analysis. Protein expression levels were confirmed by immunohistochemistry, enzyme-linked immunosorbent assay, flow cytometry, and/or Western blotting. The expression levels of messenger RNA (mRNA) for various molecules were determined by real-time polymerase chain reaction (PCR). Proliferation of osteoclast precursors was assessed by bromodeoxyuridine uptake. Osteoclast differentiation and activity were determined by quantifying tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and area of resorbed bone.

RESULTS

Treatment with halofuginone suppressed the development of autoimmune arthritis and reciprocally regulated Th17 cells and FoxP3+ Treg cells. These effects of halofuginone on Th17 differentiation involved increased signaling of ERK and reduction of STAT-3 and NF-ATc1 expression. Furthermore, halofuginone induced the expression of indoleamine 2,3-dioxygenase (IDO) in dendritic cells, leading to reduced production of Th17 cells. In addition, halofuginone prevented the formation and activity of osteoclasts through suppression of transcription factors, such as activator protein 1 and NF-ATc1, and inhibited cell cycle arrest by the committed osteoclast precursors via expression of Ccnd1 encoding cyclin D1.

CONCLUSION

Taken together, our results suggest that halofuginone is a promising therapeutic agent for the treatment of Th17 cell-mediated inflammatory diseases and bone diseases.

Treatment of severe or progressive Kaposi's sarcoma in HIV-infected adults

BACKGROUND

Kaposi's sarcoma remains the most common cancer in Sub-Saharan Africa and the second most common cancer in HIV-infected patients worldwide. Since the introduction of highly active antiretroviral therapy (HAART), there has been a decline in its incidence.However, Kaposi's sarcoma continues to be diagnosed in HIV-infected patients.

OBJECTIVES

To assess the added advantage of chemotherapy plus HAART compared to HAART alone; and the advantages of different chemotherapy regimens in HAART and HAART naive HIV infected adults with severe or progressive Kaposi's sarcoma.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and , GATEWAY, the WHO Clinical Trials Registry Platform and the US National Institutes of Health's ClinicalTrials.gov for ongoing trials and the Aegis archive of HIV/AIDS for conference abstracts. An updated search was conducted in July 2014.

SELECTION CRITERIA

Randomised trials and observational studies evaluating the effects of any chemotherapeutic regimen in combination with HAART compared to HAART alone, chemotherapy versus HAART, and comparisons between different chemotherapy regimens.

DATA COLLECTION AND ANALYSIS

Two review authors assessed the studies independently and extracted outcome data.We used the risk ratio (RR) with a 95% confidence interval (CI) as the measure of effect.We did not conduct meta-analysis as none of the included trials assessed identical chemotherapy regimens.

MAIN RESULTS

We included six randomised trials and three observational studies involving 792 HIV-infected adults with severe Kaposi's sarcoma.Seven studies included patients with a mix of mild to moderate (T0) and severe (T1) Kaposi's sarcoma. However, this review was restricted to the subset of participants with severe Kaposi's sarcoma disease.Studies comparing HAART plus chemotherapy to HAART alone showed the following: one trial comparing HAART plus doxorubicin,bleomycin and vincristine (ABV) to HAART alone showed a significant reduction in disease progression in the HAART plus ABV group (RR 0.10; 95% CI 0.01 to 0.75, 100 participants); there was no statistically significant reduction in mortality and no difference in adverse events. A cohort study comparing liposomal anthracyclines plus HAART to HAART alone showed a non-statistically significant reduction in Kaposi's sarcoma immune reconstitution inflammatory syndrome in patients that received HAART plus liposomal anthracyclines (RR 0.49; 95% CI 0.16 to 1.55, 129 participants).Studies comparing HAART plus chemotherapy to HAART plus a different chemotherapy regimen showed the following: one trial involving 49 participants and comparing paclitaxel versus pegylated liposomal doxorubicin in patients on HAART showed no difference in disease progression. Another trial involving 46 patients and comparing pegylated liposomal doxorubicin versus liposomal daunorubicin showed no participants with progressive Kaposi's sarcoma disease in either group.Studies comparing different chemotherapy regimens in patients from the pre-HAART era showed the following: in the single RCT comparing liposomal daunorubicin to ABV, there was no significant difference with the use of liposomal daunorubicin compared to ABV in disease progression (RR 0.78; 95% CI 0.34 to 1.82, 227 participants) and overall response rate. Another trial involving 178 participants and comparing oral etoposide versus ABV demonstrated no difference in mortality in either group. A non-randomised trial comparing bleomycin alone to ABV demonstrated a higher median survival time in the ABV group; there was also a non-statistically significant reduction in adverse events and disease progression in the ABV group (RR 11; 95% CI 0.67 to 179.29, 24 participants).An additional non-randomised study showed a non-statistically significant overall mortality benefit from liposomal doxorubicin as compared to conservative management consisting of either bleomycin plus vinblastine, vincristine or single-agent antiretroviral therapy alone (RR 0.93; 95% CI 0.75 to 1.15, 29 participants). The overall quality of evidence can be described as moderate quality. The quality of evidence was downgraded due to the small size of many of the included studies and small number of events.

AUTHORS' CONCLUSIONS

The findings from this review suggest that HAART plus chemotherapy may be beneficial in reducing disease progression compared to HAART alone in patients with severe or progressive Kaposi's sarcoma. For patients on HAART, when choosing from different chemotherapy regimens, there was no observed difference between liposomal doxorubicin, liposomal daunorubicin and paclitaxel.

The chemistry and biology of febrifugine and halofuginone

The trans-2,3-disubstituted piperidine, quinazolinone-containing natural product febrifugine (also known as dichroine B) and its synthetic analogue, halofuginone, possess antimalarial activity. More recently studies have also shown that halofuginone acts as an agent capable of reducing fibrosis, an indication with clinical relevance for several disease states. This review summarizes historical isolation studies and the chemistry performed which culminated in the correct structural elucidation of naturally occurring febrifugine and its isomer isofebrifugine. It also includes the range of febrifugine analogues prepared for antimalarial evaluation, including halofuginone. Finally, a section detailing current opinion in the field of halofuginone's human biology is included.

New molecular medicine-based scar management strategies

Keloids and hypertrophic scars are prevalent disabling conditions with still suboptimal treatments. Basic science and molecular-based medicine research have contributed to unravel new bench-to-bedside scar therapies and to dissect the complex signalling pathways involved. Peptides such as the transforming growth factor beta (TGF-β) superfamily, with Smads, Ski, SnoN, Fussels, endoglin, DS-Sily, Cav-1p, AZX100, thymosin-β4 and other related molecules may emerge as targets to prevent and treat keloids and hypertrophic scars. The aim of this review is to describe the basic complexity of these new molecular scar management strategies and point out new fibrosis research lines.

Aminoacyl-tRNA synthetases as drug targets in eukaryotic parasites

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Aminoacyl-tRNA synthetases are essential and many aaRS inhibitors kill parasites.

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We examine compound inhibitors tested experimentally against parasite aaRSs.

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Successful inhibitors were discovered by both phenotype and target-based approaches.

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Selectivity and resistance are ongoing challenges for development of parasite drugs.

Aminoacyl-tRNA synthetases are central enzymes in protein translation, providing the charged tRNAs needed for appropriate construction of peptide chains. These enzymes have long been pursued as drug targets in bacteria and fungi, but the past decade has seen considerable research on aminoacyl-tRNA synthetases in eukaryotic parasites. Existing inhibitors of bacterial tRNA synthetases have been adapted for parasite use, novel inhibitors have been developed against parasite enzymes, and tRNA synthetases have been identified as the targets for compounds in use or development as antiparasitic drugs. Crystal structures have now been solved for many parasite tRNA synthetases, and opportunities for selective inhibition are becoming apparent. For different biological reasons, tRNA synthetases appear to be promising drug targets against parasites as diverse as Plasmodium (causative agent of malaria), Brugia (causative agent of lymphatic filariasis), and Trypanosoma (causative agents of Chagas disease and human African trypanosomiasis). Here we review recent developments in drug discovery and target characterisation for parasite aminoacyl-tRNA synthetases.

Halofuginone inhibits the establishment and progression of melanoma bone metastases

TGF-β derived from bone fuels melanoma bone metastases by inducing tumor secretion of prometastatic factors that act on bone cells to change the skeletal microenvironment. Halofuginone is a plant alkaloid derivative that blocks TGF-β signaling with antiangiogenic and antiproliferative properties. Here, we show for the first time that halofuginone therapy decreases development and progression of bone metastasis caused by melanoma cells through the inhibition of TGF-β signaling. Halofuginone treatment of human melanoma cells inhibited cell proliferation, phosphorylation of SMAD proteins in response to TGF-β, and TGF-β-induced SMAD-driven transcription. In addition, halofuginone reduced expression of TGF-β target genes that enhance bone metastases, including PTHrP, CTGF, CXCR4, and IL11. Also, cell apoptosis was increased in response to halofuginone. In nude mice inoculated with 1205 Lu melanoma cells, a preventive protocol with halofuginone inhibited bone metastasis. The beneficial effects of halofuginone treatment were comparable with those observed with other anti-TGF-β strategies, including systemic administration of SD208, a small-molecule inhibitor of TGF-β receptor I kinase, or forced overexpression of Smad7, a negative regulator of TGF-β signaling. Furthermore, mice with established bone metastases treated with halofuginone had significantly less osteolysis than mice receiving placebo assessed by radiography. Thus, halofuginone is also effective in reducing the progression of melanoma bone metastases. Moreover, halofuginone treatment reduced melanoma metastasis to the brain, showing the potential of this novel treatment against cancer metastasis.

Advances in the systemic treatment of cutaneous sarcomas

Cutaneous sarcomas are a rare subset of soft tissue sarcomas. These tumors are primarily managed with definitive surgical resection; however, upon unresectable recurrence or metastatic spread, systemic therapy is warranted. As with other sarcomas, these treatments have classically included cytotoxic chemotherapy programs that were associated with variable response rates and poor overall survival. Recently, major advances have been made in the understanding of the molecular biology of these tumors, and treatment paradigms are changing. Multiple pathways have been documented to be important in the growth of cutaneous sarcomas, including receptor tyrosine kinases such as platelet-derived growth factor receptor, insulin-like growth factor receptor and KIT. Dysregulated angiogenesis, through vascular endothelial growth factor (VEGF) and other pathways, is also associated with the growth of these tumors. In this review, we discuss the current standard therapies of cutaneous sarcoma and the recent advances and ongoing investigations into cutaneous sarcoma biology.

Local inhibition of angiogenesis by halofuginone coated silicone materials

Anti-angiogenic therapy is a promising approach for the treatment of increased angiogenesis in certain diseases. We aimed to investigate the local anti-angiogenic effect of silicone implants coated with Halofuginone, an angiogenesis inhibitor that inhibits synthesis of collagen-type-I and matrix metalloproteinases. The degree of angiogenesis was observed after implantation of surface modified Halofuginone eluting silicone implants into a submuscular pocket in rats over a period of 3 months. Subsequently, key mediators of angiogenesis (TGF-beta-1, bFGF, COL1A1, MMP-2, MMP-9, VEGF and PDGF) were established by immunohistological staining and RT-PCR and statistically evaluated. In comparison to uncoated silicone implants, Halofuginone eluting silicone implants lead to a significant local decrease of angiogenesis. Halofuginone eluting hybrid surface silicone implants have a significant local anti-angiogenic effect by down-regulating the expression activity of key mediators of angiogenesis.

Halofuginone inhibits multiple myeloma growth in vitro and in vivo and enhances cytotoxicity of conventional and novel agents

Multiple Myeloma (MM), a malignancy of plasma cells, remains incurable despite the use of conventional and novel therapies. Halofuginone (HF), a synthetic derivative of quinazolinone alkaloid, has recently been shown to have anti-cancer activity in various preclinical settings. This study demonstrated the anti-tumour activity of HF against a panel of human MM cell lines and primary patient-derived MM cells, regardless of their sensitivity to conventional therapy or novel agents. HF showed anti-MM activity in vivo using a myeloma xenograft mouse model. HF suppressed proliferation of myeloma cells alone and when co-cultured with bone marrow stromal cells. Similarly, HF induced apoptosis in MM cells even in the presence of insulin-like growth factor 1 or interleukin 6. Importantly, HF, even at high doses, did not induce cytotoxicity against CD40 activated peripheral blood mononuclear cells from normal donors. HF treatment induced accumulation of cells in the G(0) /G(1) cell cycle and induction of apoptotic cell death associated with depletion of mitochondrial membrane potential; cleavage of poly (ADP-ribose) polymerase and caspases-3, 8 and 9 as well as down-regulation of anti-apoptotic proteins including Mcl-1 and X-IAP. Multiplex analysis of phosphorylation of diverse components of signalling cascades revealed that HF induced changes in P38MAPK activation; increased phosphorylation of c-jun, c-jun NH(2)-terminal kinase (JNK), p53 and Hsp-27. Importantly, HF triggered synergistic cytotoxicity in combination with lenalidomide, melphalan, dexamethasone, and doxorubicin. Taken together, these preclinical studies provide the preclinical framework for future clinical studies of HF in MM.

CpG methylation as a tool to characterize cell-free Kaposi sarcoma herpesvirus DNA

We studied the presence of Kaposi sarcoma herpesvirus sequences in cell-free DNA (cfDNA) isolated from the blood of patients with AIDS-related Kaposi sarcoma (KS) and primary effusion lymphoma (PEL). The use of paramagnetic beads linked to methyl-CpG binding domain protein allowed separation of virion and cell-derived DNA. Only virion DNA was detected in the blood of KS patients, whereas cell-derived DNA was detected in a patient with AIDS-related PEL. The difference in the origins of cfDNA in these settings may in part reflect very different proliferative indices in KS and PEL tumor tissue.

Halofuginone and other febrifugine derivatives inhibit prolyl-tRNA synthetase

Febrifugine, one of the fifty fundamental herbs of traditional Chinese medicine, has been characterized for its therapeutic activity whilst its molecular target has remained unknown. Febrifugine derivatives have been used to treat malaria, cancer, fibrosis, and inflammatory disease. We recently demonstrated that halofuginone (HF), a widely studied derivative of febrifugine, inhibits the development of Th17-driven autoimmunity in a mouse model of multiple sclerosis by activating the amino acid response pathway (AAR). Here we show that HF binds glutamyl-prolyl-tRNA synthetase (EPRS) inhibiting prolyl-tRNA synthetase activity; this inhibition is reversed by the addition of exogenous proline or EPRS. We further show that inhibition of EPRS underlies the broad bioactivities of this family of natural products. This work both explains the molecular mechanism of a promising family of therapeutics, and highlights the AAR pathway as an important drug target for promoting inflammatory resolution.

Microarray profiling reveals the integrated stress response is activated by halofuginone in mammary epithelial cells

BACKGROUND

The small molecule Halofuginone (HF) is a potent regulator of extracellular matrix (ECM ) gene expression and is unique in its therapeutic potential. While the basis for HF effects is unknown, inhibition of TGFβ signaling and activation of the amino acid restriction response (AAR) have been linked to HF transcriptional control of a number of ECM components and amelioration of fibrosis and alleviation of autoimmune disease by regulation of Th17 cell differentiation, respectively. The aim of this study was to generate a global expression profile of HF targets in epithelial cells to identify potential mediators of HF function in this cell type.

RESULTS

We report that HF modulation of the expression of the ECM remodeling protein Mmp13 in epithelial cells is separable from previously reported effects of HF on TGFβ signal inhibition, and use microarray expression analysis to correlate this with transcriptional responses characteristic of the Integrated Stress Response (ISR).

CONCLUSIONS

Our findings suggest activation of the ISR may be a common mechanism underlying HF biological effects.