Silibinin activated ROS-p38-NF-κB positive feedback and induced autophagic death in human fibrosarcoma HT1080 cells

Prospects of compounds of herbal plants as anticancer agents: a comprehensive review from molecular pathways

Cancer refers to the proliferation and multiplication of aberrant cells inside the human body, characterized by their capacity to proliferate and infiltrate various anatomical regions. Numerous biochemical pathways and signaling molecules have an impact on the cancer auto biogenesis process. The regulation of crucial cellular processes necessary for cell survival and proliferation, which are triggered by phytochemicals, is significantly influenced by signaling pathways. These pathways or components are regulated by phytochemicals. Medicinal plants are a significant reservoir of diverse anticancer medications employed in chemotherapy. The anticancer effects of phytochemicals are mediated by several methods, including induction of apoptosis, cessation of the cell cycle, inhibition of kinases, and prevention of carcinogenic substances. This paper analyzes the phytochemistry of seven prominent plant constituents, namely, alkaloids, tannins, flavonoids, phenols, steroids, terpenoids, and saponins, focusing on the involvement of the MAPK/ERK pathway, TNF signaling, death receptors, p53, p38, and actin dynamics. Hence, this review has examined a range of phytochemicals, encompassing their structural characteristics and potential anticancer mechanisms. It has underscored the significance of plant-derived bioactive compounds in the prevention of cancer, utilizing diverse molecular pathways. In addition, this endeavor also seeks to incentivize scientists to carry out clinical trials on anticancer medications derived from plants.

Medicinal Plants in Cancer Treatment: Contribution of Nuclear Factor-Kappa B (NF-kB) Inhibitors

Nuclear factor-kappa B (NF-κB) is one of the principal inducible proteins that is a predominant transcription factor known to control the gene expression in mammals and plays a pivotal role in regulating cell signalling in the body under certain physiological and pathological conditions. In cancer cells, such as colon, breast, pancreatic, ovarian, melanoma, and lymphoma, the NF-κB pathway has been reported to be active. In cellular proliferation, promoting angiogenesis, invasion, metastasis of tumour cells and blocking apoptosis, the constitutive activity of NF-κB signalling has been reported. Therefore, immense attention has been given to developing drugs targeting NF-κB signalling pathways to treat many types of tumours. They are a desirable therapeutic target for drugs, and many studies concentrated on recognizing compounds. They may be able to reverse or standstill the growth and spread of tumours that selectively interfere with this pathway. Recently, numerous substances derived from plants have been evaluated as possible inhibitors of the NF-κB pathway. These include various compounds, such as flavonoids, lignans, diterpenes, sesquiterpenes, polyphenols, etc. A study supported by folk medicine demonstrated that plant-derived compounds could suppress NF-κB signalling. Taking this into account, the present review revealed the anticancer potential of naturally occurring compounds which have been verified both by inhibiting the NF-κB signalling and suppressing growth and spread of cancer and highlighting their mechanism of NF-κB inhibition.

Plant Polyphenols for Aging Health: Implication from Their Autophagy Modulating Properties in Age-Associated Diseases

Polyphenols are a family of naturally occurring organic compounds, majorly present in fruits, vegetables, and cereals, characterised by multiple phenol units, including flavonoids, tannic acid, and ellagitannin. Some well-known polyphenols include resveratrol, quercetin, curcumin, epigallocatechin gallate, catechin, hesperetin, cyanidin, procyanidin, caffeic acid, and genistein. They can modulate different pathways inside the host, thereby inducing various health benefits. Autophagy is a conserved process that maintains cellular homeostasis by clearing the damaged cellular components and balancing cellular survival and overall health. Polyphenols could maintain autophagic equilibrium, thereby providing various health benefits in mediating neuroprotection and exhibiting anticancer and antidiabetic properties. They could limit brain damage by dismantling misfolded proteins and dysfunctional mitochondria, thereby activating autophagy and eliciting neuroprotection. An anticarcinogenic mechanism is stimulated by modulating canonical and non-canonical signalling pathways. Polyphenols could also decrease insulin resistance and inhibit loss of pancreatic islet β-cell mass and function from inducing antidiabetic activity. Polyphenols are usually included in the diet and may not cause significant side effects that could be effectively used to prevent and treat major diseases and ailments.

Path of Silibinin from diet to medicine: A dietary polyphenolic flavonoid having potential anti-cancer therapeutic significance

In the last few decades, targeting cancer by the use of dietary phytochemicals has gained enormous attention. The plausible reason and believe or mind set behind this fact is attributed to either lesser or no side effects of natural compounds as compared to the modern chemotherapeutics, or due to their conventional use as dietary components by mankind for thousands of years. Silibinin is a naturally derived polyphenol (a flavonolignans), possess following biochemical features; molecular formula C₂₅H₂₂O₁₀, Molar mass: 482.44 g/mol, Boiling point 793 °C, with strikingly high antioxidant and anti-tumorigenic properties. The anti-cancer properties of Silibinin are determined by a variety of cellular pathways which include induction of apoptosis, cell cycle arrest, inhibition of angiogenesis and metastasis. In addition, Silibinin controls modulation of the expression of aberrant miRNAs, inflammatory response, and synergism with existing anti-cancer drugs. Therefore, modulation of a vast array of cellular responses and homeostatic aspects makes Silibinin an attractive chemotherapeutic agent. However, like other polyphenols, the major hurdle to declare Silibinin a translational chemotherapeutic agent, is its lesser bioavailability. After summarizing the chemistry and metabolic aspects of Silibinin, this extensive review focuses on functional aspects governed by Silibinin in chemoprevention with an ultimate goal of summarizing the evidence supporting the chemopreventive potential of Silibinin and clinical trials that are currently ongoing, at a single platform.

Autophagy activated by silibinin contributes to glioma cell death via induction of oxidative stress-mediated BNIP3-dependent nuclear translocation of AIF

Induction of lethal autophagy has become a strategy to eliminate glioma cells, but it remains elusive whether autophagy contributes to cell death via causing mitochondria damage and nuclear translocation of apoptosis inducing factor (AIF). In this study, we find that silibinin induces AIF translocation from mitochondria to nuclei in glioma cells in vitro and in vivo, which is accompanied with autophagy activation. In vitro studies reveal that blocking autophagy with 3MA, bafilomycin A1 or by knocking down ATG5 with SiRNA inhibits silibinin-induced mitochondrial accumulation of superoxide, AIF translocation from mitochondria to nuclei and glioma cell death. Mechanistically, silibinin activates autophagy through depleting ATP by suppressing glycolysis. Then, autophagy improves intracellular H2O2 via promoting p53-mediated depletion of GSH and cysteine and downregulation of xCT. The increased H2O2 promotes silibinin-induced BNIP3 upregulation and translocation to mitochondria. Knockdown of BNIP3 with SiRNA inhibits silibinin-induced mitochondrial depolarization, accumulation of mitochondrial superoxide, and AIF translocation from mitochondria to nuclei, as well as prevents glioma cell death. Furthermore, we find that the improved H2O2 reinforces silibinin-induced glycolysis dysfunction. Collectively, autophagy contributes to silibinin-induced glioma cell death via promotion of oxidative stress-mediated BNIP3-dependent nuclear translocation of AIF.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

Shikonin induces apoptosis and prosurvival autophagy in human melanoma A375 cells via ROS-mediated ER stress and p38 pathways

Shikonin, a botanical drug extracted from Lithospermum erythrorhizon, exhibits anti-cancer effects in various cancer cell lines. However, the mechanisms underlying these effects have not been completely elucidated yet. Here, we showed that Shikonin induces apoptosis and autophagy in A375 cells and inhibits their proliferation. Shikonin caused G2/M phase arrest through upregulation of p21 and downregulation of cyclin B1. Shikonin significantly triggered ER stress-mediated apoptosis by upregulating the expression of p-eIF2α, CHOP, and cleaved caspase-3. It also induced protective autophagy by activating the p38 pathway, followed by an increase in the levels of p-p38, LC3B-II, and Beclin 1. Upon suppression of autophagy by 3-methyladenine, Shikonin-induced apoptosis was enhanced in A375 cells. Moreover, after pretreatment with N-acetyl-cysteine, Shikonin increased the production of reactive oxygen species that are involved in regulating ER stress-mediated apoptosis and p38-activated autophagy, as evidenced by the reversion of cell viability and apoptosis and a decrease in p-eIF2α, CHOP, p-p38, LC3B-II, and Beclin 1 levels. Thus, we demonstrated that Shikonin induced apoptosis and autophagy in A375 cells via the activation of ROS-mediated ER stress and p38 pathways, indicating that Shikonin can serve as a potential agent for human melanoma therapy.

Silibinin, A Natural Blend In Polytherapy Formulation For Targeting Cd44v6 Expressing Colon Cancer Stem Cells

Colon cancer stem cells have been attributed to poor prognosis, therapeutic resistance and aggressive nature of the malignancy. Recent reports associated CD44v6 expression with relapse, metastasis and reduced 5-year survival of colon cancer patients, thereby making it a potential therapeutic target. Thus, in this study, comprehensive prediction and screening of CD44v6 against 1674 lead compounds was conducted. Silibinin was identified as a potential compound targeting CD44v6. Inorder to substantiate these findings, the cytotoxic effect of 5FU, Silibinin and 5FU+ Silibinin was assessed on human colon carcinoma cell line HCT116 derived CD44+ subpopulation. 5FU+ Silibinin inhibited cell proliferation of CD44+ subpopulation at lower concentration than Silibinin standalone. Further, corresponding to CD44v6 knockdown cells, 5FU+ Silibinin treatment significantly decreased CD44v6, Nanog, CTNNB1 and CDKN2A expression whereas increased E-cadherin expression in HCT116 derived CD44+ cells. Moreover, synergistic effect of these drugs suppressed sphere formation, inhibited cell migration, triggered PARP cleavage and perturbation in mitochondrial membrane potential, thereby activating intrinsic apoptotic pathways and induced autophagic cell death. Importantly, 5FU+ Silibinin could inhibit PI3K/MAPK dual activation and arrest the cell cycle at G0/G1 phase. Thus, our study suggests that inhibition of CD44v6 attenuates stemness of colon cancer stem cells and holds a prospect of potent therapeutic target.

PAR-1 mediated apoptosis of breast cancer cells by V. cholerae hemagglutinin protease

Bacterial toxins have emerged as promising agents in cancer treatment strategy. Hemagglutinin (HAP) protease secreted by Vibrio cholerae induced apoptosis in breast cancer cells and regresses tumor growth in mice model. The success of novel cancer therapies depends on their selectivity for cancer cells with limited toxicity for normal tissues. Increased expression of Protease Activated Receptor-1 (PAR-1) has been reported in different malignant cells. In this study we report that HAP induced activation and over expression of PAR-1 in breast cancer cells (EAC). Immunoprecipitation studies have shown that HAP specifically binds with PAR-1. HAP mediated activation of PAR-1 caused nuclear translocation of p50-p65 and the phosphorylation of p38 which triggered the activation of NFκB and MAP kinase signaling pathways. These signaling pathways enhanced the cellular ROS level in malignant cells that induced the intrinsic pathway of cell apoptosis. PAR-1 mediated apoptosis by HAP of malignant breast cells without effecting normal healthy cells in the same environment makes it a good therapeutic agent for treatment of cancer.

Atg7 Knockdown Augments Concanavalin A-Induced Acute Hepatitis through an ROS-Mediated p38/MAPK Pathway

Concanavalin A (ConA), a T-cell mitogen that induces acute autoimmune hepatitis, is widely used to model pathophysiological processes of human acute autoimmune liver disease. Although autophagy has been extensively studied in the past decade, little is known about its molecular mechanism underlying the regulation of ConA-induced acute hepatitis. In this study, we used a Cre-conditional atg7 KO mouse to investigate the effects of Atg7-associated autophagy on ConA-induced murine hepatitis. Our results demonstrated that atg7 deficiency in mice enhanced macrophage activation and increased pro-inflammatory cytokines upon ConA stimulation. Atg7 silencing resulted in accumulation of dysfunctional mitochondria, disruption of reactive oxygen species (ROS) degradation, and increase in pro-inflammatory cytokines in Raw264.7 cells. p38/MAPK and NF-κB levels were increased upon ConA induction due to Atg7 deficiency. Blocking ROS production inhibited ConA-induced p38/IκB phosphorylation and subsequent intracellular inflammatory responses. Hence, this study demonstrated that atg7 knockout in mice or Atg7 knockdown in cell culture augmented ConA-induced acute hepatitis and related cellular malfunction, indicating protective effects of Atg7 on regulating mitochondrial ROS via a p38/MAPK-mediated pathway. Collectively, our findings reveal that autophagy may attenuate macrophage-mediated inflammatory response to ConA and may be the potential therapeutic targets for acute liver injury.

Autophagy induced by silibinin protects human epidermoid carcinoma A431 cells from UVB-induced apoptosis

Ultraviolet B (UVB) in the sun light is a major cause of skin damage, which accompanies complex alterations in irradiated skin cells, including DNA lesions, oxidative stress, inflammation and caspase activation. The protection against UVB damage requires multiple interruptions such as repair of the DNA lesions, scavenging of the reactive oxygen species (ROS), repression of the inflammation and others. Silibinin is suggested as an anti-UVB reagent, but the underlying mechanisms have not been fully elucidated. In this study, we found a role of autophagy in the anti-UVB effect of silibinin in A431 cells. Autophagy was reduced after UVB-irradiation while restored by silibinin through the suppression of the IGF-1R signalling pathway. The protective effect of silibinin in UVB-irradiated A431 cells was further enhanced by pre-treatment with an autophagy inducer, rapamycin, while it was reversed by an autophagy inhibitor, wortmannin, indicating that elevated autophagy contributed to the cell survival. Consistently, cell apoptosis was augmented by siRNAs targeting Beclin 1 and Atg5, supporting the hypothesis that autophagy induced by silibinin plays a protective role against UVB-induced epidermal apoptosis.

p38-NF-κB-promoted mitochondria-associated apoptosis and G2/M cell cycle arrest in norcantharidin-treated HeLa cells

Previous study proved that norcantharidin (NCTD) could exert its anticancer activity in a variety of malignant cell lines, including human cervical carcinoma HeLa cells. In this study, we found that NCTD-activated p38 mitogen-activated protein kinase (p38 MAPK)-nuclear transcription factor kappa B (NF-κB) signaling pathway induced mitochondrial apoptotic pathway activation and G2/M cell cycle arrest in HeLa cells. NCTD-induced mitochondria-associated apoptosis was concomitant with the collapse of mitochondrial membrane potential (ΔΨ(m)), translocation of Bax, down-regulation of Bcl-2 expression, and release of cytochrome c. NCTD-led G2/M cell-cycle arrest was associated with the up-regulated p21 and p-cdc25c expression and the down-regulated cyclin B and cdc2 expression. Treatment of the cells with p38 inhibitor SB203580 and NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) showed that p38 functioned upstream of NF-κB, while augmented apoptosis and cell cycle arrest were induced in response to NCTD with NF-κB activation. Intriguingly, NF-κB had a negative feedback regulatory effect on p38 activation. Moreover, NCTD-induced apoptosis and cell cycle arrest were significantly blocked by SB203580 and PDTC but not by pifithrin-α (p53 inhibitor). Therefore, p38-NF-κB induced mitochondrial apoptotic pathway and G2/M cell cycle arrest in NCTD-treated HeLa cells.