Modified ingenol semi-synthetic derivatives from Euphorbia tirucalli induce cytotoxicity on a large panel of human cancer cell lines

Semisynthetic phytochemicals in cancer treatment: a medicinal chemistry perspective

Cancer is the uncontrolled proliferation of abnormal cells that invade other areas, spread to other organs, and cause metastases, which is the most common cause of death. A review of all FDA-approved new molecular entities (NMEs) shows that natural products and derivatives account for over one-third of all NMEs. Before 1940, unmodified products and derivatives accounted for 43% and 14% of NME registrations, respectively. Since then, the share of unmodified products has decreased to 9.5% of all approved NMEs, while the share of derivatives has increased to 28%. Since the 1940s, semi-synthetic and synthetic derivatives of natural substances have gained importance, and this trend continues to date. In this study, we have discussed in detail isolated phytoconstituents with chemical modifications that are either FDA-approved or under clinical trials, such as podophyllotoxin, Taxol (paclitaxel, docetaxel), vinca alkaloids (vincristine, vinblastine), camptothecin, genistein, cephalotaxine, rohitukine, and many more, which may act as essential leads to the development of novel anticancer agents. Furthermore, we have also discussed recent developments in the most potent semisynthetic phytoconstituents, their unique properties, and their importance in cancer treatment.

Plant-Based Anticancer Compounds With a Focus on Breast Cancer

Breast cancer is a common form of cancer among women characterized by the growth of malignant cells in the breast tissue. The most common treatments for this condition include chemotherapy, surgical intervention, radiation therapy, hormone therapy, and biological therapy. The primary issues associated with chemotherapy and radiation therapy are their adverse events and significant financial burden among patients in underdeveloped countries. This highlights the need to explore and develop superior therapeutic options that are less detrimental and more economically efficient. Plants provide an abundant supply of innovative compounds and present a promising new avenue for investigating cancer. Plants and their derivations are undergoing a revolution due to their reduced toxicity, expediency, cost-effectiveness, safety, and simplicity in comparison to conventional treatment methods. Natural products are considered promising candidates for the development of anticancer drugs, due perhaps to the diverse pleiotropic effects on target events. The effects of plant-derived products are limited to cancer cells while leaving healthy cells unaffected. Identification of compounds with strong anticancer properties and development of plant-based medications for cancer treatment might be crucial steps in breast cancer therapy. Although bioactive compounds have potent anticancer properties, they also have drawbacks that need to be resolved before their application in clinical trials and improved for the approved drugs. This study aims to give comprehensive information on known anticancer compounds, including their sources and molecular mechanisms of actions, along with opportunities and challenges in plant-based anticancer therapies.

13-oxyingenol dodecanoate derivatives induce mitophagy and ferroptosis through targeting TMBIM6 as potential anti-NSCLC agents

Ingenol diterpenoids continue to attract the attention for their extensive biological activity and novel structural features. To further explore this type of compound as anti-tumor agent, 13-oxyingenol dodecanoate (13-OD) was prepared by a standard chemical transformation from an Euphorbia kansui extract, and 29 derivatives were synthesized through parent 13-OD. Their inhibition activities against different types of cancer were screened and some derivatives showed superior anti-non-small cell lung cancer (NSCLC) cells cytotoxic potencies than oxaliplatin. In addition, TMBIM6 was identified as a crucial cellular target of 13-OD using ABPP target angling technique, and subsequently was verified by pull down, siRNA interference, BLI and CETSA assays. With modulating the function of TMBIM6 protein by 13-OD and its derivatives, Ca2+ release function was affected, causing mitochondrial Ca2+ overload, depolarisation of membrane potential. Remarkably, 13-OD, B6, A2, and A10-2 induced mitophagy and ferroptosis. In summary, our results reveal that 13-OD, B6, A2, and A10-2 holds great potential in developing anti-tumor agents for targeting TMBIM6.

Ingenol mebutate inhibits the growth of pancreatic cancer cells in vitro via STING with an efficacy comparable to that of clinically used anticancer agents

Pancreatic cancer is associated with a poor prognosis; thus, there is an urgent need to develop new and effective treatments. Ingenol mebutate (IM), which is isolated from the latex of Euphorbia peplus, was recently shown to be effective against pancreatic cancer cell lines; however, its mechanism of action has not been fully elucidated. In this study, we focused on the less drug-sensitive pancreatic cancer cell line Panc-1 and compared IM to commercially available anticancer drugs using cell survival assays. In addition, we aimed to identify novel biomolecules that may be involved in the mechanism of action of IM using RNA sequencing, western blotting, and inhibition assays. The IC50 values after 72 h of exposure to IM and SN-38, drugs to which the Panc-1 cells are most sensitive among the tested anticancer agents, were 43.1 ± 16.8 nM and 165 ± 37 nM, respectively. IM showed a cytostatic effect equal to or greater than that of the clinically used pancreatic cancer therapeutic drugs. RNA sequencing and protein expression analysis revealed that expression of stimulator of interferon genes (STING) increased at low IM concentration, whereas cell viability decreased. Co-exposure of IM and STING inhibitor, H-151, to Panc-1 or MIA PaCa-2 cell lines canceled the growth-inhibitory effects of IM alone. In conclusion, IM may have an efficacy comparable to that of existing pancreatic cancer therapeutic agents on the less drug-sensitive Panc-1 cell line and the immune-related molecule STING plays a role in the mechanism of action of IM.

The Role of Ingenane Diterpenes in Cancer Therapy: From Bioactive Secondary Compounds to Small Molecules

Diterpenes are a class of critical taxonomic markers of the Euphorbiaceae family, representing small compounds (eg, molecules) with a wide range of biological activities and multi-target therapeutic potential. Diterpenes can exert different activities, including antitumor and multi-drug resistance-reversing activities, and antiviral, immunomodulatory, and anti-inflammatory effects, mainly due to their great structural diversity. In particular, one polycyclic skeleton has been highlighted: ingenane. Besides this natural diterpene, promising polycyclic skeletons may be submitted to chemical modification—by in silico approaches, chemical reactions, or biotransformation—putatively providing more active analogs (eg, ingenol derivatives), which are currently under pre-clinical investigation. This review outlines the current mechanisms of action and potential therapeutic implications of ingenol diterpenes as small cancer molecules.

Natural Plant Compounds: Does Caffeine, Dipotassium Glycyrrhizinate, Curcumin, and Euphol Play Roles as Antitumoral Compounds in Glioblastoma Cell Lines?

Many plant-derived compounds are shown to be promising antitumor therapeutic agents by enhancing apoptosis-related pathways and cell cycle impairment in tumor cells, including glioblastoma (GBM) cell lines. We aimed to review four natural plant compounds effective in GBM cell lines as caffeine, dipotassium glycyrrhizinate (DPG), curcumin, and euphol. Furthermore, antitumoral effect of these plant compounds on GBM cell lines through microRNAs (miRs) modulation was investigated. However, only DPG and curcumin were found as effective on miR modulation. Caffeine arrests GBM cell cycle in G0/G1 phase by cyclin-dependent kinases (CDK) complex inhibition and by decreasing BCL-2 and increasing FOXO1 expression levels causing greater apoptotic activity. Caffeine can also directly inhibit IP3R3, p38 phosphorylation, and rho-associated protein kinase (ROCK), decreasing cell invasion and migration capacity or indirectly by inhibiting the tissue inhibitor metalloproteinase-1 (TIMP-1) and integrins β1 and β3, leading to lower matrix metalloproteinases, MMP-2 and MMP-9. DPG presents antitumoral effect in GBM cells related to nuclear factor kappa B (NF-κB) pathway suppression by IRAK2 and TRAF6-mediating miR-16 and miR-146a, respectively. More recently, it was observed that DPG upregulated miR-4443 and miR-3620, responsible for post-transcriptional inhibition of the NF-κB pathway by CD209 and TNC modulation, respectively leading to lower MMP-9 and migration capacity. Curcumin is able to increase miR-223-3p, miR-133a-3p, miR-181a-5p, miR-34a-5p, miR-30c-5p, and miR-1290 expression leading to serine or threonine kinase (AKT) pathway impairment and also it decreases miR-27a-5p, miR-221-3p, miR-21-5p, miR-125b-5p, and miR-151-3p expression causing p53-BCL2 pathway inhibition and consequently, cellular apoptosis. Interestingly, lower expression of miR-27a by curcumin action enhanced the C/EBP homologous protein(CHOP) expression, leading to paraptosis. Curcumin can inhibit miR-21 expression and consequently activate apoptosis through caspase 3 and death receptor (DR) 4 and 5 activation. Autophagy is controlled by the LC-3 protein that interacts with Atg family for the LC3-II formation and autophagy activation. Euphol can enhance LC3-II levels directly in GBM cells or inhibits tumor invasion and migration through PDK1 modulation.

Modulation of MicroRNAs by Euphorbia Microsciadia Boiss in MDA-MB-231 Cell Line: New Possibilities in Breast Cancer Therapy

BACKGROUND

A large number of Euphorbia species have been evaluated for anticancer effects; however, their anticancer mechanisms have not been established up to now.

OBJECTIVE

The present study aimed to evaluate the effects of Euphorbia microsciadia (E. microsciadia) Boiss on the modulation of micro (mi) RNAs in MDA-MB-231 cell line.

METHODS

As the first step, the inhibitory concentration of hydroalcoholic extract of E. microsciadia on MDA-MB-231 cells was examined using the MTT assay, bypassing 24 and 48h from seeding. The real-time quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) was also utilized to determine Let-7, miR-15, miR-16, miR-29, miR-151, miR-155, miR-21, miR-146b, miR-181b, miR-221, miR-222, miR-21, and miR-146b expressions in MDA-MB-231 cells, by passing 24 and 48h from treating with the extract of E. microsciadia.

RESULTS

The results reveal the cytotoxic effects of E. microsciadia on MDA-MB-231 cell line in a dose-dependent manner. The half maximal Inhibitory Concentrations (IC50) were also equal to 275 and 240μg/ml for E. microsciadia, by passing 24 and 48h from the treatment, respectively. Furthermore, it was confirmed that, E. microsciadia had augmented the expression levels of Let-7, miR-15, miR-16, miR-29, and miR-34a, which lead to an increase in apoptosis.

CONCLUSION

E. microsciadia could modulate some miRNAs involved in cell cycle arrest and apoptosis in MDA-MB-231 cell line. Accordingly, targeting miRNAs by E. microsciadia can open some newer avenues for breast cancer therapy.

Status and Challenges of Plant-Anticancer Compounds in Cancer Treatment

Nowadays, cancer is one of the deadliest diseases in the world, which has been estimated to cause 9.9 million deaths in 2020. Conventional treatments for cancer commonly involve mono-chemotherapy or a combination of radiotherapy and mono-chemotherapy. However, the negative side effects of these approaches have been extensively reported and have prompted the search of new therapeutic drugs. In this context, scientific community started to look for innovative sources of anticancer compounds in natural sources, including traditional plants. Currently, numerous studies have evaluated the anticancer properties of natural compounds derived from plants, both in vitro and in vivo. In pre-clinical stages, some promising compounds could be mentioned, such as the sulforaphane or different phenolic compounds. On the other hand, some phytochemicals obtained positive results in clinical stages and were further approved for cancer treatment, such as vinca alkaloids or the paclitaxel. Nevertheless, these compounds are not exempt of limitations, such as low solubility, restricted effect on their own, negative side-effects, etc. This review aims to compile the information about the current phytochemicals used for cancer treatment and also promising candidates, main action mechanisms and also reported limitations. In this sense, some strategies to face the limitations have been considered, such as nano-based formulations to improve solubility or chemical modification to reduce toxicity. In conclusion, although more research is still necessary to develop more efficient and safe phytochemical drugs, more of these compounds might be used in future cancer therapies.

Semi-Synthetic Ingenol Derivative from Euphorbia tirucalli Inhibits Protein Kinase C Isotypes and Promotes Autophagy and S-phase Arrest on Glioma Cell Lines

The identification of signaling pathways that are involved in gliomagenesis is crucial for targeted therapy design. In this study we assessed the biological and therapeutic effect of ingenol-3-dodecanoate (IngC) on glioma. IngC exhibited dose-time-dependent cytotoxic effects on large panel of glioma cell lines (adult, pediatric cancer cells, and primary cultures), as well as, effectively reduced colonies formation. Nevertheless, it was not been able to attenuate cell migration, invasion, and promote apoptotic effects when administered alone. IngC exposure promoted S-phase arrest associated with p21CIP/WAF1 overexpression and regulated a broad range of signaling effectors related to survival and cell cycle regulation. Moreover, IngC led glioma cells to autophagy by LC3B-II accumulation and exhibited increased cytotoxic sensitivity when combined to a specific autophagic inhibitor, bafilomycin A1. In comparison with temozolomide, IngC showed a mean increase of 106-fold in efficacy, with no synergistic effect when they were both combined. When compared with a known compound of the same class, namely ingenol-3-angelate (I3A, Picato^®), IngC showed a mean 9.46-fold higher efficacy. Furthermore, IngC acted as a potent inhibitor of protein kinase C (PKC) activity, an emerging therapeutic target in glioma cells, showing differential actions against various PKC isotypes. These findings identify IngC as a promising lead compound for the development of new cancer therapy and they may guide the search for additional PKC inhibitors.