A novel synthetic C-1 analogue of 7-deoxypancratistatin induces apoptosis in p53 positive and negative human colorectal cancer cells by targeting the mitochondria: enhancement of activity by tamoxifen

Amaryllidaceae Alkaloids Decrease the Proliferation, Invasion, and Secretion of Clinically Relevant Cytokines by Cultured Human Colon Cancer Cells

Alkaloids isolated from members of the Amaryllidaceae plant family are promising anticancer agents. The purpose of the current study was to determine if the isocarbostyrils narciclasine, pancratistatin, lycorane, lycorine, crinane, and haemanthamine inhibit phenomena related to cancer progression in vitro. To achieve this, we examined the proliferation, adhesion, and invasion of cultured human colon cancer cells via MTT assay and Matrigel-coated Boyden chambers. In addition, Luminex assays were used to quantify the secretion of matrix metalloproteinases (MMP) and cytokines associated with poor clinical outcomes. We found that all alkaloids decreased cell proliferation regardless of TP53 status, with narciclasine exhibiting the greatest potency. The effects on cell proliferation also appear to be specific to cancer cells. Narciclasine, lycorine, and haemanthamine decrease both adhesion and invasion but with various potencies depending on the cell line. In addition, narciclasine, lycorine, and haemanthamine decreased the secretion of MMP-1, -2, and -7, as well as the secretion of the cytokines pentraxin 3 and vascular endothelial growth factor. In conclusion, the present study shows that Amaryllidaceae alkaloids decrease phenomena and cytokines associated with colorectal cancer progression, supporting future investigations regarding their potential as multifaceted drug candidates.

Synthesis, Anti-proliferative Activity, and Molecular Docking Study of New Series of 1,3-5-Triazine Schiff Base Derivatives

Based on the use of s-triazine as a scaffold, we report here a new series of s-triazine Schiff base derivatives and their anti-proliferative activity against two cancer cell lines: human breast carcinoma (MCF-7), and colon cancer (HCT-116) compared with tamoxifen as a reference compound. Several derivatives exhibited growth inhibition activity in the sub-micromolar range. The results reveal that the s-triazine Schiff base derivatives showed varied activities and that the substituents on the s-triazine core have a great effect on the anti-proliferative activity. Compounds with a piperidino and benzylamino substituent on the s-triazine moiety 4b and 4c were most effective in both cell lines compared to the reference compound used. In addition, compound 4b has a para chlorine atom on the benzylidine residue, demonstrating the most potent activity with IC₅₀ values of 3.29 and 3.64 µM in MCF-7 and HCT-116, respectively. These results indicate that in general, the nature of the substituents on the triazine core and the type of substituent on the benzilyldene ring significantly influenced the anti-proliferative activity. The results obtained from the anti-proliferative activity and the molecular docking study indicate that s-triazine-hydrazone derivatives may be an excellent scaffold for the development of new anti-cancer agents.

Targeting Autophagic Pathways by Plant Natural Compounds in Cancer Treatment

Nowadays, natural compounds of plant origin with anticancer effects have gained more attention because of their clinical safety and broad efficacy profiles. Autophagy is a multistep lysosomal degradation pathway that may have a unique potential for clinical benefit in the setting of cancer treatment. To retrieve articles related to the study, the databases of Google Scholar, Web of sciences, Medline and Scopus, using the following keywords: Autophagic pathways; herbal medicine, oncogenic autophagic pathways, tumor-suppressive autophagic pathways, and cancer were searched. Although natural plant compounds such as resveratrol, curcumin, oridonin, gossypol, and paclitaxel have proven anticancer potential via autophagic signaling pathways, there is still a great need to find new natural compounds and investigate the underlying mechanisms, to facilitate their clinical use as potential anticancer agents through autophagic induction.

Phenanthridone Alkaloids of the Amaryllidaceae as Activators of the Apoptosis-related Proteolytic Enzymes, Caspases

Apoptosis-inducing anticancer drugs have garnered widespread interest in recent years. Targets which concomitantly also exhibit minimal adverse effects in normal, healthy cells have been particularly well-received. The phenanthridone alkaloids such as pancratistatin and narciclasine exemplify such a class of chemotherapeutics, with potent and selective cytotoxic effects in a wide variety of cancer cells which are manifested via the apoptotic mode of cell death. Caspases are central to the apoptotic process through their key function as effector molecules in apoptosis-related signaling pathways. Any attempt to mediate in such pathways, for example to probe the efficacy or mechanism of action of a drug, would inexorably serve to have a modulatory effect on these proteolytic enzymes. Apoptosis studies of phenanthridone alkaloids of the Amaryllidaceae have only gathered momentum over the past decade, following which caspases have understandably emerged as reliable biochemical markers of the process in an assortment of cancers. This review covers such studies of these alkaloids based on their structural-type, pointing out the various caspases which have been activated in different cancer cells and how structure modification can to a certain extent have a bearing on such activity. Also considered are clues to the apoptosis signaling pathways mediated following phenanthridone-induced activation of caspases.

Exploiting mitochondrial and oxidative vulnerabilities with a synthetic analog of pancratistatin in combination with piperlongumine for cancer therapy

Harsh adverse effects as a result of nonspecific targeting of chemotherapeutics currently pose obstacles in cancer therapy; thus, it would be invaluable to devise novel approaches to specifically target cancer cells. The natural compound pancratistatin (PST) has been shown to preferentially induce apoptosis in a variety of cancer cell types. Recently, several analogs of PST were shown to be efficacious in inducing apoptosis in a variety of aggressive cancer cell types via cancer cell mitochondrial targeting; it caused dissipation of mitochondrial membrane potential and decreased oxygen consumption, and with isolated mitochondria, it induced the release of apoptogenic factors. The natural compound piperlongumine has been shown to target the stress response to reactive oxygen species in cancer cells. We explored the combinatorial potential of two small molecules (SVTH-6 and piperlongumine) that target these vulnerabilities in cancer cells. Interestingly, when combined with the PST analog, SVTH-6, an increase in mitochondrial dysfunction was observed, leading to an enhanced cytotoxic effect against several human cancer cell types. Additionally, this combination treatment was effective in reducing cancer cell growth in physiologically more relevant 3-dimensional spheroid cell cultures. This enhanced effect was found to be dependent on reactive oxygen species generation because an antioxidant could rescue cancer cells from this combination treatment. Importantly, noncancerous cells were markedly less sensitive to this combination treatment. Thus, targeting mitochondrial and oxidative stress vulnerabilities of cancer cells could be an effective strategy for cancer therapy.-Ma, D., Gilbert, T., Pignanelli, C., Tarade, D., Noel, M., Mansour, F., Gupta, M., Ma, S., Ropat, J., Curran, C., Vshyvenko, S., Hudlicky, T., Pandey. S. Exploiting mitochondrial and oxidative vulnerabilities with a synthetic analog of pancratistatin in combination with piperlongumine for cancer therapy.

Natural Compounds from Herbs that can Potentially Execute as Autophagy Inducers for Cancer Therapy

Accumulated evidence indicates that autophagy is a response of cancer cells to various anti-cancer therapies. Autophagy is designated as programmed cell death type II, and is characterized by the formation of autophagic vacuoles in the cytoplasm. Numerous herbs, including Chinese herbs, have been applied to cancer treatments as complementary and alternative medicines, supplements, or nutraceuticals to dampen the side or adverse effects of chemotherapy drugs. Moreover, the tumor suppressive actions of herbs and natural products induced autophagy that may lead to cell senescence, increase apoptosis-independent cell death or complement apoptotic processes. Hereby, the underlying mechanisms of natural autophagy inducers are cautiously reviewed in this article. Additionally, three natural compounds—curcumin, 16-hydroxycleroda-3,13-dien-15,16-olide, and prodigiosin—are presented as candidates for autophagy inducers that can trigger cell death in a supplement or alternative medicine for cancer therapy. Despite recent advancements in therapeutic drugs or agents of natural products in several cancers, it warrants further investigation in preclinical and clinical studies.

Cancer Cell Mitochondria Targeting by Pancratistatin Analogs is Dependent on Functional Complex II and III

Enhanced mitochondrial stability and decreased dependence on oxidative phosphorylation confer an acquired resistance to apoptosis in cancer cells, but may present opportunities for therapeutic intervention. The compound pancratistatin (PST) has been shown to selectively induce apoptosis in cancer cells. However, its low availability in nature has hindered its clinical advancement. We synthesized PST analogs and a medium-throughput screen was completed. Analogs SVTH-7, -6, and -5 demonstrated potent anti-cancer activity greater than PST and several standard chemotherapeutics. They disrupted mitochondrial function, activated the intrinsic apoptotic pathway, and reduced growth of tumor xenografts in vivo. Interestingly, the pro-apoptotic effects of SVTH-7 on cancer cells and mitochondria were abrogated with the inhibition of mitochondrial complex II and III, suggesting mitochondrial or metabolic vulnerabilities may be exploited by this analog. This work provides a scaffold for characterizing distinct mitochondrial and metabolic features of cancer cells and reveals several lead compounds with high therapeutic potential.

CSC-3436 switched tamoxifen-induced autophagy to apoptosis through the inhibition of AMPK/mTOR pathway

Background

Triple-negative breast cancer (TNBC) lacks specific therapeutic target and limits to chemotherapy and is essential to develop novel therapeutic regimens. Increasing studies indicated that tamoxifen, a selective estrogen receptor modulators (SERMs), has anti-tumor therapeutic effect in estrogen receptor α (ERα)-negative tumor. Here, we determined whether autophagy was activated by tamoxifen in TNBC cells. Moreover, CSC-3436 displayed strong and selective growth inhibition on cancer cells. Next, we investigated the anti-proliferation effect of combination of CSC-3436 plus tamoxifen on cell death in TNBC cells.

Results

Our study found that tamoxifen induces autophagy in TNBC cells. Endoplasmic reticulum stress and AMPK/mTOR contributed tamoxifen-induced autophagy. Interestingly, in combination treatment with CSC-3436 enhanced the anti-proliferative effect of tamoxifen. We found that CSC-3436 switched tamoxifen-induced autophagy to apoptosis via cleavage of ATG-5. Moreover, AMPK/mTOR pathway may involve in CSC-3436 switched tamoxifen-induced autophagy to apoptosis. The combination of tamoxifen and CSC-3436 produced stronger tumor growth inhibition compared with CSC-3436 or tamoxifen alone treatments in vivo.

Conclusion

These data indicated that CSC-3436 combined with tamoxifen may be a potential approach for treatment TNBC.