Betulinic acid shows anticancer activity against equine melanoma cells and permeates isolated equine skin in vitro

What Is the Evidence Behind Sarcoid Treatments?

Despite the ubiquitous nature of sarcoids, robust data regarding the selection of treatment modalities are scarce, with many treatments having little or no published data to support their use. Treatment options are numerous and vary with the location and type of sarcoid, treatment accessibility, and the financial status of the owner. Many treatments are expensive and time-consuming, and some have health and safety implications. It is this author's belief that, based on the limited evidence base, appropriate treatment options vary with the location and type of the sarcoid, and no one treatment is universally appropriate.

Equine Melanoma Updates

Melanomas are very common in older gray horses, with 80% of gray horses having at least 1 melanoma by 15 years of age. Historically considered a benign disease, it is now known that up to 66% of lesions will eventually metastasize. Melanomas may also cause local problems due to abscessation, ulceration, and interference with function of the affected areas. Treatment can be limited by size and location, but surgical resection, where possible, is likely to be the treatment of choice.

Cellular and molecular mechanisms underlying the potential of betulinic acid in cancer prevention and treatment

BACKGROUND

Betulinic acid (BA), which is a pentacyclic triterpenoid found in the bark of plane, birch, and eucalyptus trees, has emerged as a compound of significant interest in scientific research due to its potential therapeutic applications. BA has a range of well-documented pharmacological and biological effects, including antibacterial, immunomodulatory, diuretic, antiviral, antiparasitic, antidiabetic, and anticancer activities. Although numerous research studies have explored the potential anticancer effects of BA, there is a noticeable gap in the literature, highlighting the need for a more up-to-date and comprehensive evaluation of BA's anticancer potential.

PURPOSE

The aim of this work is to critically assess the reported cellular and molecular mechanisms underlying the cancer preventive and therapeutic effects of BA.

METHODS

Relevant research on the inhibitory effects of BA against cancerous cells was searched using Science Direct, Scopus, Web of Science, and PubMed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

The anticancer properties of BA are mediated by the activation of cell death and cell cycle arrest, production of reactive oxygen species, increased mitochondrial permeability, modulation of nuclear factor-κB and Bcl-2 family signaling. Emerging evidence also underscores the combined anticancer effects of BA with other natural bioactive compounds or approved drugs. Notably, several novel BA nanoformulations have been found to exhibit encouraging antineoplastic activities.

CONCLUSION

BA, whether used alone or in combination, or as a form of nanoformulation, shows significant potential for cancer prevention and treatment. Nevertheless, further detailed studies are necessary to confirm the therapeutic effectiveness of this natural compound.

Potent drug delivery enhancement of betulinic acid and NVX-207 into equine skin in vitro - a comparison between a novel oxygen flow-assisted transdermal application device and microemulsion gels

BACKGROUND

Gray horses are predisposed to equine malignant melanoma (EMM) with advancing age. Depending on the tumor's location and size, they can cause severe problems (e.g., defaecation, urination, feeding). A feasible therapy for EMM has not yet been established and surgical excision can be difficult depending on the location of the melanoma. Thus, an effective and safe therapy is needed. Naturally occurring betulinic acid (BA), a pentacyclic triterpene and its synthetic derivate, NVX-207 (3-acetyl-betulinic acid-2-amino-3-hydroxy-2-hydroxymethyl-propanoate) are known for their cytotoxic properties against melanomas and other tumors and have already shown good safety and tolerability in vivo. In this study, BA and NVX-207 were tested for their permeation potential into equine skin in vitro in Franz-type diffusion cell (FDC) experiments after incubation of 5 min, 30 min and 24 h, aiming to use these formulations for prospective in vivo studies as a treatment for early melanoma stages. Potent permeation was defined as reaching or exceeding the half maximal inhibitory concentrations (IC50) of BA or NVX-207 for equine melanoma cells in equine skin samples. The active ingredients were either dissolved in a microemulsion (ME) or in a microemulsion gel (MEG). All of the formulations were transdermally applied but the oil-in-water microemulsion was administered with a novel oxygen flow-assisted (OFA) applicator (DERMADROP TDA).

RESULTS

All tested formulations exceeded the IC50 values for equine melanoma cells for BA and NVX-207 in equine skin samples, independently of the incubation time NVX-207 applied with the OFA applicator showed a significant time-dependent accumulation and depot-effect in the skin after 30 min and 24 h (P < 0.05).

CONCLUSIONS

All tested substances showed promising results. Additionally, OFA administration showed a significant accumulation of NVX-207 after 30 min and 24 h of incubation. Further in vivo trials with OFA application are recommended.

Cross-Species Comparison of the Pan-RAF Inhibitor LY3009120's Anti-Tumor Effects in Equine, Canine, and Human Malignant Melanoma Cell Lines

Malignant melanomas (MMs) are the abnormal proliferation of melanocytes and are one of the lethal skin cancers in humans, equines, and canines. Accordingly, MMs in companion animals can serve as naturally occurring animal models, completing conventional cancer models. The common constitutive activation of the MAPK and PI3K pathways in MMs has been described in all three species. Targeting the related pathways is considered a potential option in comparative oncologic approaches. Herein, we present a cross-species comparative analysis exposing a set of ten melanoma cell lines (one human, three equine, and six canine) derived from primary tumors or metastasis to a pan-RAF and RAF dimer inhibitor (LY3009120). Cellular response (proliferation, biomass, metabolism, early and late apoptosis/necrosis, and morphology) and the presence of pathogenic single-nucleotide variants (SNVs) within the mutational hotspot genes BRAF exon 11 and 15, NRAS exon 2 and 3, KRAS exon 2, and KIT exon 11 were analyzed. This study showed that equine malignant melanoma (EMM) cells (MelDuWi) harbor the KRAS p.Q61H mutation, while canine malignant melanoma (CMM) cells (cRGO1 and cRGO1.2) carry NRAS p.G13R. Except for EMM metastasis cells eRGO6 (wild type of the above-mentioned hotspot genes), all melanoma cell lines exhibited a decrease in dose dependence after 48 and 72 h of exposure to LY3009120, independent of the mutation hotspot landscape. Furthermore, LY3009120 caused significant early apoptosis and late apoptosis/necrosis in all melanoma cell lines except for eRGO6. The anti-tumor effects of LY3009120 were observed in nine melanoma cell lines, indicating the potential feasibility of experimental trials with LY3009120. The present study reveals that the irradiation-resistant canine metastasis cells (cRGO1.2) harboring the NRAS p.G13R mutation are significantly LY3009120-sensitive, while the equine metastases-derived eRGO6 cells show significant resistance to LY3009120, which make them both valuable tools for studying resistance mechanisms in comparative oncology.

Betulinic acid arrests cell cycle at G2/M phase by up-regulating metallothionein 1G inhibiting proliferation of colon cancer cells

Betulinic acid (BA) is a pentacyclic triterpene found in many plant species and has a broad-spectrum anti-tumor effect in various cancers, including colon cancer (CRC). However, its anticancer mechanism in CRC is no clear. RNA sequencing and bioinformatics analysis showed BA up-regulated 378 genes and down-regulated 137 genes in HT29 cells, while 2303 up-regulated and 1041 down-regulated genes were found in SW480 cells. KEGG enrichment analysis showed BA significantly stimulated the expression of metallothionein 1 (MT1) family genes in both HT29 and SW480 cells. Metallothionein 1G (MT1G) was the gene with the highest upregulation of MT1 family genes induced by BA dose-dependently. High MT1G expression enhanced the sensitivity of CRC cells to BA, whereas, MT1G knockdown had the opposite effect in vitro and in vivo. GSEA and GSCA showed genes affected by BA treatment were involved in cell cycle and G2/M checkpoint in CRC. Flow cytometry further exhibited BA reduced the percentage of G0/G1 cells and increased the percentage of G2/M cells in a dose-dependent manner, which could be rescued by MT1G knockdown. Moreover, MT1G also counteracted the BA-induced changes in cell cycle-related proteins (CDK2 and CDK4) and p-Rb. In summary, we have revealed a new anti-tumor mechanism that BA altered the cell cycle progression of CRC cells by upregulating MT1G gene, thereby inhibiting the proliferation of CRC cells.

Progress in Antimelanoma Research of Natural Triterpenoids and Their Derivatives: Mechanisms of Action, Bioavailability Enhancement and Structure Modifications

Melanoma is one of the most dangerous forms of skin cancer, characterized by early metastasis and rapid development. In search for effective treatment options, much attention is given to triterpenoids of plant origin, which are considered promising drug candidates due to their well described anticancer properties and relatively low toxicity. This paper comprehensively summarizes the antimelanoma potential of natural triterpenoids, that are also used as scaffolds for the development of more effective derivatives. These include betulin, betulinic acid, ursolic acid, maslinic acid, oleanolic acid, celastrol and lupeol. Some lesser-known triterpenoids that deserve attention in this context are 22β-hydroxytingenone, cucurbitacins, geoditin A and ganoderic acids. Recently described mechanisms of action are presented, together with the results of preclinical in vitro and in vivo studies, as well as the use of drug delivery systems and pharmaceutical technologies to improve the bioavailability of triterpenoids. This paper also reviews the most promising structural modifications, based on structure-activity observations. In conclusion, triterpenoids of plant origin and some of their semi-synthetic derivatives exert significant cytotoxic, antiproliferative and chemopreventive effects that can be beneficial for melanoma treatment. Recent data indicate that their poor solubility in water, and thus low bioavailability, can be overcome by complexing with cyclodextrins, or the use of nanoparticles and ethosomes, thus making these compounds promising antimelanoma drug candidates for further development.

Equine Melanocytic Tumors: A Narrative Review

Adult grey horses have a high incidence of melanocytic tumors. This article narratively reviews the role of some genetic features related to melanoma formation in horses, such as STX17 mutation, ASIP or MITF alterations, and the link between the graying process and the development of these tumors. A clear system of clinical and pathological classification of melanocytic tumors in naevus, dermal melanoma, dermal melanomatosis and anaplastic malignant melanoma is provided. Clinical and laboratorial methods of diagnosing are listed, with fine needle aspiration and histopathology being the most relevant. Relevance is given to immunohistochemistry, describing potentially important diagnostic biomarkers such as RACK1 and PNL2. Different therapeutical options available for equine practitioners are mentioned, with surgery, chemotherapy and electroporation being the most common. This article also elucidatesnew fields of research, perspectives, and new therapeutic targets, such as CD47, PD-1 and COX-2 biomarkers.

Pharmaco-Toxicological Assessment of the Combined Cytotoxic Effects of Digoxin and Betulinic Acid in Melanoma Cells

Betulinic acid, a small molecule from pentacyclic triterpenes class, has been widely studied for its antitumor activity, revealing that it induces the apoptosis of tumor cells in a selective manner. In recent years, digoxin, a cardiac glycoside found particularly in the plant species Digitalis lanata, has drawn interest for its potential antitumor properties. The present study was designed to evaluate the antimelanoma potential of betulinic acid (BA), digoxin (DG), and their association (DG + BA). In vitro assessments were performed 24 h post-treatment on two human melanoma cell lines (SK-Mel-28 and RPMI-7951). In addition, the potential irritant effects of the test samples were evaluated using the chorioallantoic membrane of hen's eggs. BA and DG exhibit a concentration-dependent cytotoxic activity, with the combination of the two having a more marked effect on the decrease in cell viability (~17% for SK-Mel-28 cells and ~23% for RPMI-7951 cells). Further, morphological changes (rounding of the cells and their separation from the plaque) and alterations in the nucleus and actin fibers (condensation of chromatin and actin fibers, formation of apoptotic bodies) were observed, indicating an apoptotic-like process. Moreover, no irritating effects were observed in ovo. As a result, DG + BA acid may have synergistic potential in the antitumor treatment of melanoma, but future studies are needed in order to clarify the biological mechanisms involved.

Betulinic acid: A natural promising anticancer drug, current situation, and future perspectives

Natural products serve as the single most productive source for the discovery of drugs and pharmaceutical leads. Among the various chemicals derived from microbes, plants, and animals, phytochemicals have emerged as potential candidates for the development of anticancer drugs due to their structural diversities, complexities, and pleiotropic effects. Herein, we discuss betulinic acid (BA), a ubiquitously distributed lupane structured pentacyclic triterpenoid, scrutinized as a promising natural agent for the prevention, suppression, and management of various human malignancies. Ease of availability, common occurrences, cell-specific cytotoxicity, and astonishing selectivity are the important factors that contribute to the development of BA as an anticancer agent. The current review delineates the mechanistic framework of BA-mediated cancer suppression through the modulation of multiple signaling pathways and also summarizes the key outcomes of BA in preclinical investigations.

Anti-Inflammatory and Anticancer Properties of Birch Bark-Derived Betulin: Recent Developments

Birch tree bark-derived betulin has attracted scientific interest already for several centuries, being one of the first natural products identified from plants. However, the cellular events regulated by betulin and precise molecular mechanisms under these processes have been begun to be understood only recently. Today, we know that betulin can exert important anticancer activities through modulation of diverse cellular pathways. In this review article, betulin-regulated molecular signaling is unraveled and presented with a special focus on its participation in anti-inflammatory processes, especially by modulating nuclear factor-κB (NF-κB), prostaglandin/COX, and nuclear factor erythroid2-related factor 2 (Nrf2)-mediated cascades. By regulating these diverse pathways, betulin can not only affect the development and progression of different cancers, but also enhance the antitumor action of traditional therapeutic modalities. It is expected that by overcoming the low bioavailability of betulin by encapsulating it into nanocarriers, this promising natural compound may provide novel possibilities for targeting inflammation-related cancers.

Effects of Topically Applied Betulinic Acid and NVX-207 on Melanocytic Tumors in 18 Horses

Simple Summary

Melanomas are skin tumors of the pigment-producing melanocytes. Equine melanomas are among the most frequently diagnosed tumors affecting grey horses. The melanocytic tumors progress to malignancy in more than two-thirds of cases. Previous laboratory experiments and studies with horses utilizing the naturally occurring betulinic acid (BA) and its derivative NVX-207 showed promising results with respect to the topical (epicutaneous) treatment of equine melanoma. Therefore, the aim of this feasibility study was to gain first insights into the effect and safety of BA and NVX-207 in eighteen horses with early-stage melanocytic tumors after a 13-week-long topical application. The topical treatment was convenient and safe. Compared to a placebo, the data suggest a positive treatment effect from topical application of BA and NVX-207 on equine melanomas toward the end of the treatment period. However, the time period studied was too short to conclusively prove this. Further advancement of the investigational medicinal products studied herein could lead to an effective, topical and marketable novel drug which helps to relieve suffering and, consequently, improve the welfare of equine skin cancer patients.

Abstract

The naturally occurring betulinic acid (BA) and its derivative NVX-207 induce apoptosis in equine melanoma cells in vitro. After topical application, high concentrations of the substances can be reached in healthy equine skin. With the aim to investigate the effect and safety of topically applied BA and NVX-207 in horses with melanocytic tumors, the longitudinal, prospective, randomized, double-blind, placebo-controlled study protocol included eighteen Lipizzaner mares with early-stage cutaneous melanoma assigned to three groups. Melanocytic lesions were topically treated either with a placebo, 1% BA or 1% NVX-207 twice a day for 91 days. Caliper measurements, clinical examinations and blood tests were performed to assess the effects and safety of the medication. The topical treatment was convenient and safe. The volumes of tumors treated with BA were significantly reduced over time as compared to tumors treated with the placebo from day 80 of the study. Although treatment with NVX-207 seemed to decrease tumor volume, these results did not reach statistical significance. The findings must be regarded as preliminary due to the limited group size and need to be replicated in a larger cohort with modified pharmaceutical test formulations. Accordingly, the treatment protocol cannot yet be recommended in its current form.

In vitro assessment of triterpenoids NVX-207 and betulinyl-bis-sulfamate as a topical treatment for equine skin cancer

Equine sarcoid (ES) is the most prevalent skin tumor in equids worldwide. Additionally, aging grey horses frequently suffer from equine malignant melanoma (EMM). Current local therapies targeting these skin tumors remain challenging. Therefore, more feasible topical treatment options should be considered. In order to develop a topical therapy against ES and EMM, betulinyl-bis-sulfamate and NVX-207, derivatives of the naturally occurring betulin and betulinic acid, respectively, were evaluated for their antiproliferative (crystal violet staining assay), cytotoxic (MTS assay) and apoptotic (AnnexinV staining, cell cycle investigations) effects on primary ES cells, EMM cells and equine dermal fibroblasts in vitro. The more potent derivative was assessed for its in vitro penetration and permeation on isolated equine skin within 30 min and 24 h using Franz-type diffusion cells and HPLC analysis. Betulinyl-bis-sulfamate and NVX-207 inhibited the proliferation and metabolism in ES cells, EMM cells and fibroblasts significantly (p < 0.001) in a time- and dose-dependent manner. NVX-207 had superior anticancer effects compared to betulinyl-bis-sulfamate. Both compounds led to the externalization of phosphatidylserines on the cell membrane and DNA fragmentation, demonstrating that the effective mode of action was apoptosis. After 48 h of treatment with NVX-207, the number of necrotic cells was less than 2% in all cell types. Detected amounts of NVX-207 in the different skin layers exceeded the half-maximal inhibitory concentrations calculated by far. Even though data obtained in vitro are auspicious, the results are not unconditionally applicable to the clinical situation. Consequently, in vivo studies are required to address the antitumoral effects of topically applied NVX-207 in ES and EMM patients.

N-acetylglycoside of oleanolic acid (aridanin) displays promising cytotoxicity towards human and animal cancer cells, inducing apoptotic, ferroptotic and necroptotic cell death

BACKGROUND

The discovery of novel phytochemicals represents a reasonable approach to fight malignancies, especially those which are resistant to standard chemotherapy.

PURPOSE

We evaluated the cytotoxic potential of a naturally occurring N-acetylglycoside of oleanolic acid, aridanin, on 18 cancer cell lines, including sensitive and drug-resistant phenotypes mediated by P-glycoprotein, BCRP, p53 knockout, deletion-mutated EGFR, or BRAF mutations. Furthermore, metastasizing B16/F10 cells, HepG2 hepatocarcinoma and normal AML12 hepatocytes were investigated. The mechanisms of aridanin-induced cell death was further investigated.

METHODS

The resazurin reduction assay (RRA) was applied to evaluate the cytotoxicity, autophagy, ferroptotic and necroptotic cell death. CCRF-CEM leukemia cells were used for all mechanistic studies. A caspase-Glo assay was applied to evaluate the caspase activities. Flow cytometry was applied for the analyses of cell cycle (PI staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP; JC-1) and reactive oxygen species (ROS; H2DCFH-DA).

RESULTS

Aridanin and doxorubicin (positive control) inhibited the proliferation of all cancer cell lines tested. The IC50 values for aridanin varied from 3.18 µM (CCRF-CEM cells) to 9.56 µM (HepG2 cells). Aridanin had considerably lower IC50 values than that of doxorubicin against multidrug-resistant CEM/ADR5000 cells and melanoma cell lines (MaMel-80a, Mel-2a, MV3, and SKMel-505). Aridanin induced apoptosis in CCRF-CEM cells through increase of ROS levels and MMP breakdown, and to a lesser extent via caspases activation. Aridanin also induced ferroptotic and necroptotic cell death.

CONCLUSION

The present study opens good perpectives for the use of this phytochemical as an anticancer drug to combat multi-facorial resistance to established chemotherapeutics.