Antitumor Effects of Chelerythrine: A Literature Review

Abstract

Chelerythrine (CHE), one of the main active components of the medicinal plant, Chelidonium majus, (Figure 1) Botanical authority is traditionally used as a natural medicine for its significant antitumor activity. The relevant literature on the antitumor activity of CHE has been reviewed to provide a theoretical basis for further study and utilization. This review aimed to provide new ideas for developing tumor-targeted drugs.

Introduction

Chelidonium majus, a plant in the Papaveraceae family, is a traditional Chinese herbal medicine with an analgesic effect and is used to relieve cough and ulcer pain, for disinfection, and as a diuretic. Chelerythrine (CHE) (Figure 2) is one of the main effective active components of C majus. Major pharmacologically relevant components, most of which were isolated, are isoquinoline alkaloids. CHE has been found to be antibacterial, ¹ antiparasitic, ² anti-inflammatory, ³ antiplatelet, ⁴ anti-diabetic, ⁵ and to relieve stomach ulcers induced by ethanol. ⁶ It also provides protective effects against lipopolysaccharide (LPS)-induced endotoxic shock, ⁷ among other biological activities. Moreover, Chmura et al ⁸ reported that CHE is cytotoxic to 9 types of tumor cells (eg, MCF7, MCF7ADR, H329, DaOY, LnCaP, SQ120B, JSQ13, SCC135, and SCC61). However, after years of research, the ability of CHE to induce apoptosis in a variety of cancer cells, including those of the prostate, ⁹ liver, ¹⁰ and kidney, ¹¹ has been favored by numerous researchers. It has also been shown that apoptosis may be associated with reactive oxygen species (ROS)-dependent endoplasmic reticulum (ER) stress.^12,13 Additionally, Gao et al ¹⁴ showed that CHE can inhibit the growth of cisplatin-resistant non-small cell lung cancer (NSCLC) A549 cells, through enhanced growth inhibition and apoptosis induction, showing a synergistic antitumor effect on NSCLC A549 cells and subcutaneous graft tumors in nude mice. Furthermore, Lin et al ¹⁵ found that CHE selectively inhibits the growth of triple-negative breast cancer (TNBC) cell lines and shows a synergistic/additive effect in combination with the chemotherapeutic drug, paclitaxel. The antitumor activity exhibited by such compounds isolated from natural sources has the potential to address major problems in the field of oncology.

Figure 1.

A photograph of celandine (Chelidonium majus).

Figure 2.

The chemical structure of chelerythrine (CHE).

The Antitumor Activity of CHE

Influence of the Signal Transduction Pathway

Influencing signal transduction pathways is an effective way to control cell proliferation and differentiation.

Yang et al 16 reported that detection of the signaling pathway activated by CHE in osteosarcoma through protein blotting revealed that CHE-induced apoptosis is mediated by rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase/ERK) kinase (MEK)/extracellular signal-regulated kinase (ERK pathway activation. These findings suggest that activation of the ERK-mitogen-activated protein kinases (MAPK) pathway may be a therapeutic strategy for osteosarcoma. Subsequently, Yang et al ¹⁷ used MTT(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), flow cytometry, immunofluorescence staining, and protein blotting, and found a significant inhibition of CHE on Henrietta Lacks (HeLa) cells. They also found that CHE dose-dependently inhibited the expression of PI3 K subunits and downstream AKT/mTOR and protein kinase C (PKC) signaling. The abnormal expression of CHE resulted in the upregulation of APAF1, cleaved caspase-9, cleaved caspase-3, and cleaved- poly (ADP-ribose) polymerase (PARP), thereby inducing mitochondrial apoptosis. Furthermore, it has been illustrated that CHE triggers mitochondrial apoptosis via the PI3 K/BAD signaling pathway to inhibit the proliferation of HeLa cells.

Kumar et al ¹⁸ also investigated the effect of CHE on the activation of the p53-dependent/independent pathway in Dalton lymphoma (DL) cell death. DL cells were treated with CHE for 1, 3, and 6 h. It was found that treatment with CHE significantly increased the expression of total p53/phosphate-53 (ser-15) at the protein and mRNA level, which led to the activation of the p53-dependent apoptotic pathway in DL cells. Furthermore, the increased activity of cytochrome c, caspase-9, and caspase-3, as well as the degradation of DNA fragments, confirmed the activation of the p53-independent apoptotic pathway in p53-knockdown RNAi-DL cells. These findings show that apoptotic pathways that mediate signal targeting have the potential to aid in the development of better therapeutic tumor regimens (Table 1).

Table 1.

Induction of Apoptosis of Tumor Cells by Chelerythrine (CHE).

Cell lines	Signal channel	Machine processed	Reference
Osteosarcoma cells	RAF/MEK/ERK	Activation of ERK-MAPK apoptosis	Yang et al 16
HeLa cell	AKT /mTOR /PKCα PI3 K/BAD	The PI3 K subunits, Cleaved Caspase-9, Cleaved Caspase-3, and Cleaved-PARP, proliferate and undergo apoptosis	Yang et al 17
Dalton Lymphoma (DL) cells	p53-dependent/ independent pathway	Degradation of p53/phosphate-53 (ser-15), cytochrome c, caspase-9, caspase-3, and DNA fragments	Kumar et al 18

Abbreviations: ERK, extracellular signal-regulated kinase; PAPRP, poly (ADP-ribose) polymerase; RAF, rapidly accelerated fibrosarcoma; MAPK, mitogen-activated protein kinase.

Cell Growth Cycle Arrest

Because of the uncontrolled growth of tumor cells, cancer can be regarded as a periodic cell cycle defect. As such, both, tumor cell cycle arrest and the induction of tumor cell apoptosis can be used as effective means to control the tumor (Table 2).

Table 2.

Chelerythrine (CHE) can Block Tumor Cells at Different Times.

Cell lines	Method	Underlying mechanism	Reference
BGC823 of gastric cancer cells	Mass concentrations of 1.5, 2.0, and 2.5 µg/mL	The S phase, G2/M phase, and apoptosis rates were positively correlated with the number of cells	Yongli 19
The human leukemic cell line, HL-60	2.6 µM IC50	The cell cycle was stalled in the G1 phase apoptosis (induction of caspase-8 activity)	Vrba et al 20
Human lung cancer (A549, H460), colon cancer (HCT116, SW480), breast cancer (MCF-7, MDA-MB231), and peripheral blood mononuclear cells from healthy individuals	16 to 500 µg/mL was selective and differently toxic and non-toxic to CHE	Induced apoptosis of cancer cells (under the microscope) and arrest in the G2/M phase	Deljanin et al 21
NSCLC, including A549, NCI-H1299, NCI-H292, and NCI-H460 human umbilical vein endothelial cells and LL24 human lung fibroblasts	To establish a new kind of CHE and its analog, 3f	Dose-dependent and associated with G0/G1 cell cycle arrest	Yang et al 22

Zong et al ¹⁹ found that the rate of apoptosis in BGC823 gastric cancer cells induced by CHE was positively correlated with the No. of cells in the S and G2/M phase. However, in human leukemia HL-60 cells, Vrba et al. ²⁰ found that CHE with a half-maximal inhibitory concentration (IC50) of 2.6 µM stalled the cell cycle at the G1 phase and induced apoptosis (by stimulating caspase-8 activity) and necrosis. Furthermore, Deljanin et al ²¹ intervened with a whole-plant-dried ethanol extract of white cabbage in human lung cancer (A549, H460), colon cancer (HCT116, SW480), and breast cancer (MCF-7, MDA-MB231) cell lines, as well as peripheral blood monocytes from healthy individuals. The extract was found to be selective and differentially toxic to other cancer cells at a concentration of 16 to 500 µg/mL. Additionally, IC50 at intervals ranging from 44 to 143 µg/mL demonstrated synergistic activity with doxorubicin at lower concentrations (1-2 µg/mL), antagonism at higher doses, induced apoptosis of cancer cells (microscopy), and arrest in the G2/M phase. Moreover, Yang et al ²² established a series of new CHE analogs and evaluated NSCLC cell lines, NCI-H1299, NCI-H292, and NCI-H460. Specifically, they compared the cytotoxicity of these new analogs in NSCLC and non-tumor cell lines (including human umbilical vein endothelial cells and LL24 human lung fibroblasts). The results showed that analogue compound 3f was significantly dose-dependent in A549 and NCI-H1299 cells and stalled the G0/G1 cell cycle. In this study, the molecular arrangement and electronic features of 3f were closely related to the structure of CHE and supported its activity.

Induction of the Apoptosis Pathway

The identification of small-molecule inhibitors of anti-apoptotic Bcl-2 family members plays a pivotal role in the mitochondrial regulation of cellular apoptotic pathways, providing new therapeutic opportunities.

Chan et al ²³ screened 107,423 extracts from natural products by high-throughput screening. Using CHE as an inhibitor of the L-Bak Bcl-2 homology 3 (BH3) domain, they observed the inhibition of BclXL-Bak BH3 peptide binding at a concentration of 1.5 µM/L and the dislocation of the BH3-containing protein, Bax, from Bcl-XL. They also found that although staurosporine, H7, etoposide, and CHE released cytochrome c from mitochondria in intact cells, only CHE released cytochrome-c from isolated mitochondria. Moreover, it has been found that CHE-treated mammalian cells undergo apoptosis through the mitochondrial pathway. Furthermore, cells overexpressing Bcl-XL that were fully resistant to apoptotic stimulation in the study also remained sensitive to CHE. Finally, CHE directly initiates apoptosis by targeting the Bcl-2 family proteins. Furthermore, a study by Zhang et al showed ¹⁰ that the proliferation of SMMC-7721 liver cancer cells was inhibited by CHE in a time- and dose-dependent manner. Additionally, obvious accumulation in the S phase was observed, and the cells showed typical apoptotic characteristics. Furthermore, CHE induced significant apoptosis by disrupting the mitochondrial membrane potential, releasing cytochrome c, activating caspase-3, and cleaving PARP in a dose-dependent manner. Additionally, when Bcl-XL expression was downregulated and Bax and Bid expression were upregulated, Bcl-2 was unchanged. These findings show that CHE plays an important role in inhibiting tumor growth through the activation of the mitochondrial pathway to induce apoptosis in human HCC cells and regulate the expression of Bcl-2 family proteins. Yang et al ¹⁷ recently showed that CHE induced mitochondrial apoptosis in HeLa cells by regulating the expression of Bcl-2 family members. Moreover, immunofluorescence staining analysis indicated that the transfer of AIF and cytochrome to the cytoplasm or nucleus and significant changes in mitochondrial morphology were observed in HeLa cells. However, in an earlier study by Wan et al, ²⁴ mouse embryonic fibroblasts (MEFs) lacking Bax or Bak were not significantly defective in apoptotic signaling, but Bax and Bak double knockout (DKO) showed significant resistance to different apoptotic stimuli, indicating that Bax and Bak are sufficient and unnecessary regulators of apoptotic signaling. It was also noted that CHE acts as a Bcl-XL inhibitor and triggers apoptosis by acting directly on mitochondria. In contrast to classical apoptotic stimuli, CHE is capable of directly inducing apoptosis in DKO MEFs, and wild-type and DKO MEFs are equally sensitive to CHE-induced apoptosis. Furthermore, CHE-mediated cytochrome c release is rapid and precedes translocation and integration of Bax. In addition, CHE does not trigger cell death in DKO MEFs through necroptotic or autophagic death mechanisms. However, CHE induces the loss of mitochondrial membrane potential, membrane permeability conversion, and subsequent activation of the mitochondrial apoptotic pathway, even in Bax and Bak-deficient cells. These findings suggest that an alternative Bax/Bak-independent apoptosis pathway remains to be explored.

Oxidative Stress Induces Autophagy

The production of ROS is closely related to apoptosis. ROS were once considered to be a trivial metabolic byproduct that could be harmful to cells if not cleared or neutralized in time. However, recent studies have shown that ROS not only regulates cell proliferation, ²⁵ but a moderate production of ROS also helps cells maintain normal function, while excess production may cause lethal oxidative stress. Cell-intrinsic antioxidant mechanisms generally balance the disruptive effects caused by excess ROS. ²⁶ Moreover, extensive experimental data show that CHE induces the death of NSCLC, prostate, and renal cancer cells by regulating ROS generation, and is reversible by pretreatment through the ROS scavenger, N-acetyl-1-cysteine.^12,13,27

Typically, apoptosis, autophagic cell death, and necrosis are caused by small, moderate, and large amounts of ROS, respectively. ²⁵ Wu et al ¹² suggested that CHE could increase ROS accumulation in prostate cancer cells and lead to ROS-dependent ER stress and apoptosis and that pretreatment with N-acetylcysteine completely reversed CHE-induced apoptosis, as well as ER stress activation. CHE induces unique apoptosis of ROS-dependent ER stress in prostate cancer cells. Therefore, the discovery of the activated ROS-mediated ER stress apoptosis pathway by CHE provides the framework for new methods of cancer treatment. However, most studies regarding the anti-cancer effects of CHE have focused on its ability to induce apoptosis, a type I method of programmed cell death. ²⁸ However, whether autophagy, as a type II method of programmed cell death, ²⁹ contributes to the anti-cancer role of CHE has also attracted attention from researchers.

Autophagy is a slowly evolving system that induces the degradation of cytoplasmic inclusions in a lysosome-dependent manner. ³⁰ Tang et al ²⁷ first studied the role and mechanism of autophagy in NSCLC cells, and found that CHE reduced cell viability, inhibited colony formation, and induced apoptosis in a concentration-dependent manner. CHE also triggered the expression of microtubule-associated protein in A549 and NCI-H1299 cells. In combination treatment with chloroquine (an autophagy inhibitor), CHE further increased LC3-II expression, and a large No. of red dots stably expressing mRFP-EGFP-LC3 were observed in CHE-treated A549 cells, indicating that CHE induced autophagic flux. Moreover, the silencing of beclin 1 reversed the CHE-induced expression of LC3-II. Additionally, CHE triggered the production of ROS in both cell lines. The reduction of ROS levels through pretreatment with acetylcysteine reversed the CHE-induced decrease in cell viability, apoptosis, and autophagy. This inconsistency in autophagic effects may be due to the varying cancer cell lines. The antioxidant capacity of A549 cells is higher than that of NCI-H1299 cells, ³¹ and NCI-H1299 cells are more prone to producing excess ROS, which leads to autophagic cell death. ³² Alternatively, different products of autophagic degradation may contribute to the unique role of autophagy. ³³ The role of ROS-induced autophagy in cancer treatment may be largely dependent on the source of ROS production.

Inhibition of PKC Interaction

PKC is closely related to tumor development, and its overexpression has been found in many tumor cells, indicating that CHE as a PKC inhibitor can be reasonably manipulated to be an antitumor drug. PKC, which was first identified in the mouse brain in 1977, ³⁴ belongs to the serine/threonine kinase family and is widely distributed in eukaryotic cells as a key molecule for signal transduction. CHE is considered to be a potent PKC inhibitor (Table 3).

Table 3.

Potential Protein Kinase C (PKC) Targeting Effects of Chelerythrine (CHE).

Targets	Characteristic	Machine processed	Reference
Tyrosine protein kinases, cyclic adenosine phosphate-dependent protein kinases, and calcium /calmodulin-dependent protein kinases	Half of the inhibition occurred at 0.66 µM/L	Selective inhibition of PKC	Herbert et al 35
PKC isoform, PKN2	Highly expressed in TNBC cell lines	Knockdown of PKN2 in TNBC cells inhibited colony formation and the growth of xenografts	Lin et al 15
Rodent cortical neurons and neuronal cell lines	At 10 µM	Reduced the phosphorylation of both PKC and cyclic adenosine phosphate-dependent protein kinase substrates in mouse cultured cortical neurons	Saavedra et al 36

Abbreviations: PKC, protein kinase C; TNBC, triple-negative breast cancer.

Herbert et al ³⁵ found that the antitumor activity of CHE measured in vitro may be attributed to the inhibition of PKC, half of which occurs at 0.66 µM/L, by interacting with the catalytic domain of PKC. In contrast to tyrosine, cyclic adenosine phosphate-dependent, and calcium/calmodulin-dependent protein kinases, CHE can selectively inhibit PKC. TNBC is a subtype of breast cancer that is currently lacking targeted therapy. Lin et al ¹⁵ showed that PKN2, a PKC isoform, was also highly expressed in TNBC cell lines, and knockdown of PKN2 in TNBC cells inhibited colony formation and growth of xenografts. These findings suggest that PKN2 is required for the survival of TNBC cells and is most likely a targeted marker that can be selectively inhibited by CHE. Although CHE is used as a PKC inhibitor, its inhibitory effect is controversial. Saavedra et al ³⁶ stated in their most recent study that possible non-targeted effects could be observed between CHE and cultured rodent cortical neurons and neuronal cell lines. Phosphorylation of PKC and cyclic adenosine phosphate-dependent protein kinase substrates in cultured mouse cortical neurons was reduced by 10 µM CHE commonly used in neuronal cultures, but not in rat primary cortical neurons or striatal cell lines. Notably, they also found that CHE induced a concentration-dependent increase in intracellular calcium (2 + ) levels to mediate calpain, CHE-induced ERK1/2, and calpain-independent caspase-3 activation, which could be terminated by the calcium chelator, BAPTA-AM. Additionally, CHE promoted calpain activation by cleaving spectrin, striatal-rich protein tyrosine phosphatase, and calcineurin A. ³⁶ Similar to normal synaptic mechanisms, increased calcium concentrations can promote metastatic growth of breast cancer cells, according to previous studies that documented the ability of cells to couple to astrocytes through gap junctions, reprogramming them to create a tumor microenvironment that supports their growth. ³⁷ Zeng et al ³⁸ reported a significant interaction between brain metastatic cells and neurons and demonstrated that activates the GluN2B-NMDAR signaling axis in the glutamate-stimulated brain tumor microenvironment, while breast cancer cells functionally produce interactions with neurons and astrocytes. Moreover, Venkataramani et al ³⁹ suggested that neuronal activity can promote the deterioration of glioma cells through non-synaptic paracrine and autocrine mechanisms. It can be argued that CHE, as a specific and widely used PKC inhibitor for signal transduction, should be excluded as a PKC inhibitor in future studies when it is shown not to have an effect on PKC in non-neuronal cells.

Targeted G-Tetrameric Chimerism

The 6 hallmarks of malignancy include cells that are anti-apoptotic, insensitive to anti-growth signals, have self-sufficient growth signals, sustained angiogenesis, unlimited replication potential, and tissue infiltration/metastasis. ⁴⁰ These 6 markers are closely related to the gene promoters forming the G-tetraplexes, including c-MYC, c-KIT, and KRAS (self-sufficiency); RB1 (insensitive); Bcl-2 (anti-apoptotic); VEGFA (angiogenesis); hTERT (unlimited replication); and PDGFA (transfer).^41–46 These oncogene promoters form extremely diverse folded forms of G-tetramers.

Verma et al ⁴⁷ proposed that G-tetramers can affect expression at the gene promoter and can be directly regulated at the transcription level. ⁴⁸ Jana et al, ⁴⁹ employed CHE after the treatment of MCF7 breast cancer cells, and confirmed through various spectroscopic techniques (ultraviolet absorption spectroscopy, fluorescence anisotropy, circular dichroism spectroscopy, and CD melting) and molecular dynamic simulations that effectively monitored the combination of CHE and G-tetramers indexes, that the formation of CHE-tetramer complexes is thermodynamically feasible. To confirm the ability of CHE to bind to DNA, the binding constant of CHE to CT-DNA (dG-dC) · Poly · Poly (dG-dC), Poly (dA-dT), Poly (dA-dT), and 7 other double-stranded oligonucleotides was determined using a pH of 5.3, indicating that CHE showed a highly specific binding ability for DNA containing continuous GC base pairs [5′-TGGGGA-3′/3′-ACCCCT-5′]. ⁵⁰ Using UV visible spectroscopy, fluorescence spectroscopy, and circular dichroism spectroscopy,. Shu et al ⁵¹ found that CHE can bind to human telomeric DNA and induce it to form G-4 strands, thus preventing telomerase activity and inhibiting lung cancer A549, colon cancer HCT-8, and liver cancer Bel-7402 cell proliferation. This indicated that CHE is a telomeric, G-tetrastrand stabilizer and an effective telomerase inhibitor. The G-tetraplex-binding nature of CHE plays a crucial role in studying the antitumor activity of this compound and provides new insights into the future development of targeted cancer therapies (Table 4).

Table 4.

The High Binding of Chelerythrine (CHE) to DNA in Cancer Cells.

Project type	Method	Machine processed	Reference
MCF7 breast cancer cells	UV absorption spectra, fluorescence anisotropy, circular dichroism spectroscopy, and CD melting/molecular dynamics simulations	G-tetramer complex formation	Jana et al 49
Binding constants of CT-DNA, Poly (dG-dc) · Poly (dG-dC), Poly (dA-dT), Poly (dA-dT), and remaining 7 double-stranded oligonucleotides	Fluorescence titrimetric method	High-specific binding capacity for DNA containing continuous GC base pairs [5′-TGGGGA-3′/3′-ACCCCT-5′]	Bai et al 50
Lung cancer A549, colon cancer HCT-8, and liver cancer Bel-7402 cells	UV visible, fluorescence, and circular dichroism	Binding to telomeric DNA induces G-4 chain formation; preventing telomerase activity and cell proliferation	Shu et al 51

Specific Targeted Effects in Drug Combinations

As a traditional Chinese medicine (TCM) monomeric compound, CHE has nonspecific cellular targets and multi-target properties. Additionally, plant-derived chemotherapeutic agents are toxic to some extent. To improve cancer targeting with phytochemical compounds, targeting must be specific yet flexible (Table 5).

Table 5.

Synergistic Effect of Chelerythrine (CHE) in Drug Combination Therapy in Cancer Cells.

Cell lines	Drug combination	Machine processed	Reference
NCI-H1703	NCI-CHE hydrochloride	Nuclear content of β-catenin as well as the overall cellular content β-catenin of cancer stem cell transcription factors (SOX2 and MYC ↓)	Heng et al 52
SK-MES-1 and A549	Erlotinib and cisplatin	Blocking EGFR signaling by reducing the phosphorylation of downstream targets (e g, STAT3, ERK1/2, p38 MAPK, and Bad proteins)	Gao et al and He et al14,53
TNBC cell lines (MDA-MB-231, BT-549, HCC1937, and MDA-MB-468) and non-TNBC cell lines (MCF7, ZR75-1, SK-BR-3, and MDA-MB-453)	Paclitaxel	TNBC cell lines were more sensitive and dose- and time-dependent than non-TNBC cell lines	Lin et al 15

Abbreviations: ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; TNBC, triple-negative breast cancer

Concentration-Dependent Improvement of the Targeted Pathways

The cell viability assay by Heng et al ⁵² confirmed that the use of the correct concentration of CHE hydrochloride could improve the targeting pathway through its effects on cytotoxic and antiproliferative activity in NSCLC cell lines. Immunofluorescence staining of β-catenin showed that the nuclear content of β-catenin as well as the overall cellular content were decreased after treatment of CHE hydrochloride with NCI-H1703. Moreover, the favorable inhibitory activity of CHE hydrochloride on cancer stem cells (CSCs) was observed, including soft agar colony formation, migration, invasion, and spheroid formation. CHE hydrochloride treatment exhibits certain concentration-dependent targeting behaviors with regulated β-catenin expression, cell death, and apoptosis. Moreover, downregulation of catenin implies downregulation of CSC transcription factors (SOX2 and MYC) and usually induces necrosis at high concentrations and apoptosis at lower concentrations. In conclusion, CHE has the potential to mitigate cancer growth due to its inhibitory effect on CSC oncogenic activity in lung cancer and can be flexibly regulated according to concentration to modulate specific targeting in various cell lines.

Combinations Produce Synergistic Effects

A recent study suggests that synergistic effects may be achieved through targeted coverage pathways in a combination treatment regimen consisting of phytochemical compounds and chemical therapies. ⁵⁴ Phytochemical compounds also have the potential to mitigate chemical therapy-induced toxicity, which further justifies their use with conventional therapies. ⁵⁵ For example, combination treatment of CHE hydrochloride, erlotinib, and cisplatin had synergistic or additive effects against NSCLC.^14,53 Paclitaxel chemotherapy acts by enhancing the polymerization and stability of microtubules, disrupting the progression of the normal cell cycle during mitosis. ⁵⁶ At present, no targeted therapy exists for patients with TNBC, and chemotherapy is still the standard treatment regimen. Lin et al ¹⁵ investigated the effect of CHE combined with paclitaxel on the proliferation of TNBC cells. They evaluated 4 TNBC (MDA-MB-231, BT-549, HCC1937, and MDA-MB-468) and 4 non-TNBC cell lines (MCF7, ZR75-1, SK-BR-3, and MDA-MB-453). All 4 TNBC cell lines experienced reduced proliferation in a time-dependent manner to a greater degree than the non-TNBC cell lines. Therefore, TNBC cell lines were more sensitive and dose- and time-dependent to this treatment than non-TNBC cell lines. These findings showed that CHE exhibits selective, antiproliferative activity against TNBC cells, and the dual treatment of CHE and paclitaxel has additive or synergistic effects. Therefore, combination therapy with CHE and chemotherapeutic agents is a significant treatment plan for tumors.

Conclusion

CHE is an active ingredient extracted from traditional Chinese herbal medicine and has the advantages of low toxicity, high utility, many targets, and strong specificity. From a safety perspective, naturally derived phytochemical compounds are superior to the immune response of patients with cancer. Several TCM monomers and natural compounds with similar properties to CHE have been present in other official treatment regimens used in different countries. However, in recent years, CHE research in China has lacked momentum. Moreover, most experiments related to natural compounds and TCM monomers with chemotherapeutic drugs harbor many limitations, such as the lack of stochastic methods, non-standardized methods of tumor size measurement, subjective evaluation, and the lack of an appropriate sample size and statistical methods. Traditional and modern medicine from various ethnic backgrounds should be brought together to tap into the full potential of the field of antitumor medicine.

The following aspects should be further investigated: First, pharmacological techniques should be employed to utilize the targeted specificity of CHE and determine the forms of preparation and individualized dosage. Second, in addition to in vitro cells, in vivo models should be utilized to explore the specific antitumor mechanism of CHE. Moreover, computer models should be developed to optimize the exploration of CHE in tumor cells and reduce the cost of this modality. Third, due to the various ways in which different cancer cells produce ROS, the mechanisms of various pathways are understood only at the level of conjecture and have undergone preliminary verification. Therefore, CHE-induced ROS production in various types of cancer cells warrants further research. Fourth, CHE can effectively inhibit the G-tetrastrand structure, combining human telomeric DNA and RNA G-tetramers. Thus, the complete signaling cascade and fine regulatory sites of the tetrastrand structure formed in the promoter regions of oncogenes such as Bcl-2, VEGFA, and KRAS, as well as their expression, should be explored. Fifth, artificial intelligence is the leading method of accurate detection, characterization, and monitoring, especially with the development of fine dynamic tumor reconstruction. Therefore, future research should be multidisciplinary and include artificial intelligence to deduce tumor genotype and biological process, predict clinical results, and evaluate CHE targets to understand the impact on adjacent organs. Sixth, studies show that the aberrant expression of the PIWI-interacting RNAs (piRNA) signaling pathway regulates the expression of DNA methyltransferase, and the highly promising mechanism of piRNA regulation using CHE will be a breakthrough in the field of oncology. Seventh, currently based on network pharmacology of Chinese medicine monomer, drug, compound, are in the lateral verification of its multiple target effect, such research lack of deep exploration of the circuit link, so makes the research appears two large ends, but small middle, so based on network pharmacology reverse molecular docking and computer modeling, under the same structure relationship, and from the existing natural plant compounds screening drugs, should be a new idea. Finally, epigenetics is the main controlling factor of oncogenes in the development of cancer. Therefore, applying the epigenetic properties of CHE to treat malignant tumors demonstrates great potential in the field of epigenetic research.

The discovery of natural resources promotes research on plant-derived compounds and their TCM monomers. Research and clinical transformations focused on the applications of CHE will provide new strategies for the precise diagnosis and treatment of cancer. Therefore, in this era of rapid technological development, various disciplines and TCM can complement each other, and together a multidisciplinary approach toward an effective treatment for cancer can be made.