Isoharringtonine inhibits breast cancer stem-like properties and STAT3 signaling

Homoharringtonine induces apoptosis of mammary carcinoma cells by inhibiting the AKT/mTOR signaling pathway

Mammary tumour is the most common type of tumour in dogs, especially in unneutered female dogs. Homoharringtonine (HHT) is a natural alkaloid that can be used to treat various types of human tumour. However, the inhibitory effect and mechanism of HHT on canine mammary carcinomas (CMC) remain unclear. This study aimed to evaluate the inhibitory effect of HHT on CMC in vitro and determine its underlying molecular mechanism. The effects of HHT on the cytotoxicity of CMC U27 cells were evaluated by the cell counting kit-8, wound healing, and Transwell assays. HHT-induced apoptosis of U27 cells was detected by JC-1 and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay. Moreover, the gene expression of B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) were analysed using quantitative reverse transcription-polymerase chain reaction (RT-qPCR), and the protein expression of protein kinase B/mammalian target of rapamycin (AKT/mTOR) and mitochondrial apoptosis proteins were determined by western blotting. Furthermore, mammary tumour-bearing mouse models were established using 4T1 cells to evaluate the therapeutic effect of HHT. It was found that HHT could significantly down-regulated the protein expression of p-AKT, p-mTOR, and Bcl-2, and up-regulated the protein expression of P53, Bax, cleaved caspase-3, and cleaved caspase-9. In addition, HHT significantly suppressed both tumour volume and mass in mammary tumour mice. In conclusion, HHT damages CMC cells by inhibiting the AKT/mTOR signalling pathway and inducing mitochondrial apoptosis. Such findings lay a theoretical foundation for the clinical treatment of CMC and provide more options for clinical medication.

STAT family of transcription factors in breast cancer: Pathogenesis and therapeutic opportunities and challenges

Breast cancer is the most commonly diagnosed cancer and second-leading cause of cancer deaths in women. Breast cancer stem cells (BCSCs) promote metastasis and therapeutic resistance contributing to tumor relapse. Through activating genes important for BCSCs, transcription factors contribute to breast cancer metastasis and therapeutic resistance, including the signal transducer and activator of transcription (STAT) family of transcription factors. The STAT family consists of six major isoforms, STAT1, STAT2, STAT3, STAT4, STAT5, and STAT6. Canonical STAT signaling is activated by the binding of an extracellular ligand to a cell-surface receptor followed by STAT phosphorylation, leading to STAT nuclear translocation and transactivation of target genes. It is important to note that STAT transcription factors exhibit diverse effects in breast cancer; some are either pro- or anti-tumorigenic while others maintain dual, context-dependent roles. Among the STAT transcription factors, STAT3 is the most widely studied STAT protein in breast cancer for its critical roles in promoting BCSCs, breast cancer cell proliferation, invasion, angiogenesis, metastasis, and immune evasion. Consequently, there have been substantial efforts in developing cancer therapeutics to target breast cancer with dysregulated STAT3 signaling. In this comprehensive review, we will summarize the diverse roles that each STAT family member plays in breast cancer pathobiology, as well as, the opportunities and challenges in pharmacologically targeting STAT proteins and their upstream activators in the context of breast cancer treatment.

Tumor microenvironment: a prospective target of natural alkaloids for cancer treatment

Malignant tumor has become one of the major diseases that seriously endangers human health. Numerous studies have demonstrated that tumor microenvironment (TME) is closely associated with patient prognosis. Tumor growth and progression are strongly dependent on its surrounding tumor microenvironment, because the optimal conditions originated from stromal elements are required for cancer cell proliferation, invasion, metastasis and drug resistance. The tumor microenvironment is an environment rich in immune/inflammatory cells and accompanied by a continuous, gradient of hypoxia and pH. Overcoming immunosuppressive environment and boosting anti-tumor immunity may be the key to the prevention and treatment of cancer. Most traditional Chinese medicine have been proved to have good anti-tumor activity, and they have the advantages of better therapeutic effect and few side effects in the treatment of malignant tumors. An increasing number of studies are giving evidence that alkaloids extracted from traditional Chinese medicine possess a significant anticancer efficiency via regulating a variety of tumor-related genes, pathways and other mechanisms. This paper reviews the anti-tumor effect of alkaloids targeting tumor microenvironment, and further reveals its anti-tumor mechanism through the effects of alkaloids on different components in tumor microenvironment.

Ethnopharmacology, chemodiversity, and bioactivity of Cephalotaxus medicinal plants

Cephalotaxus is the only genus of Cephalotaxaceae family, and its natural resources are declining due to habitat fragmentation, excessive exploitation and destruction. In many areas of China, folk herbal doctors traditionally use Cephalotaxus plants to treat innominate swollen poison, many of which are cancer. Not only among Han people, but also among minority ethnic groups, Cephalotaxus is used to treat various diseases, e.g., cough, internal bleeding and cancer in Miao medicine, bruises, rheumatism and pain in Yao medicine, and ascariasis, hookworm disease, scrofula in She medicine, etc. Medicinal values of some Cephalotaxus species and compounds are acknowledged officially. However, there is a lack of comprehensive review summarizing the ethnomedicinal knowledge of Cephalotaxus, relevant medicinal phytometabolites and their bioactivities. The research progresses in ethnopharmacology, chemodiversity, and bioactivities of Cephalotaxus medicinal plants are reviewed and commented here. Knowledge gaps are pinpointed and future research directions are suggested. Classic medicinal books, folk medicine books, herbal manuals and ethnomedicinal publications were reviewed for the genus Cephalotaxus (Sanjianshan in Chinese). The relevant data about ethnobotany, phytochemistry, and pharmacology were collected as comprehensively as possible from online databases including Scopus, NCBI PubMed, Bing Scholar, and China National Knowledge Infrastructure (CNKI). "Cephalotaxus", and the respective species name were used as keywords in database search. The obtained articles of the past six decades were collated and analyzed. Four Cephalotaxus species are listed in the official medicinal book in China. They are used as ethnomedicines by many ethnic groups such as Miao, Yao, Dong, She and Han. Inspirations are obtained from traditional applications, and Cephalotaxus phytometabolites are developed into anticancer reagents. Cephalotaxine-type alkaloids, homoerythrina-type alkaloids and homoharringtonine (HHT) are abundant in Cephalotaxus, e.g., C. lanceolata, C. fortunei var. alpina, C. griffithii, and C. hainanensis, etc. New methods of alkaloid analysis and purification are continuously developed and applied. Diterpenoids, sesquiterpenoids, flavonoids, lignans, phenolics, and other components are also identified and isolated in various Cephalotaxus species. Alkaloids such as HHT, terpenoids and other compounds have anticancer activities against multiple types of human cancer. Cephalotaxus extracts and compounds showed anti-inflammatory and antioxidant activities, immunomodulatory activity, antimicrobial activity and nematotoxicity, antihyperglycemic effect, and bone effect, etc. Drug metabolism and pharmacokinetic studies of Cephalotaxus are increasing. We should continue to collect and sort out folk medicinal knowledge of Cephalotaxus and associated organisms, so as to obtain new enlightenment to translate traditional tips into great therapeutic drugs. Transcriptomics, genomics, metabolomics and proteomics studies can contribute massive information for bioactivity and phytochemistry of Cephalotaxus medicinal plants. We should continue to strengthen the application of state-of-the-art technologies in more Cephalotaxus species and for more useful compounds and pharmacological activities.

Homoharringtonine inhibited breast cancer cells growth via miR-18a-3p/AKT/mTOR signaling pathway

Homoharringtonine (HHT), a natural alkaloid derived from the cephalotaxus, exhibited its anti-cancer effects in hematological malignancies clinically. However, its pesticide effects and mechanisms in treating solid tumors remain unclear. In this study, we found that HHT was capable of inhibiting tumor growth after 5-days treatment of breast cancer cells, MCF-7, in vivo. Furthemore, HHT also significantly inhibited the cancer cell growth and induced cell apoptosis in vitro. miRNA sequencing proved miR-18a-3p was noticeably downregulated in the cells after HHT treatment. Moreover, downregulating miR-18a-3p increased HHT-induced cell apoptosis; our data supported that HHT suppressed miR-18a-3p expression and inhibited tumorigenesis might via AKT-mTOR signaling pathway. In conclusion: our study proved that HHT suppressed breast cancer cell growth and promoted apoptosis mediated by regulating of the miR-18a-3p-AKT-mTOR signaling pathway, HHT may be a promising antitumor agent in breast cancer treatment.

Small-Molecule Drug Discovery in Triple Negative Breast Cancer: Current Situation and Future Directions

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, but an effective targeted therapy has not been well-established so far. Considering the lack of effective targets, where do we go next in the current TNBC drug development? A promising intervention for TNBC might lie in de novo small-molecule drugs that precisely target different molecular characteristics of TNBC. However, an ideal single-target drug discovery still faces a huge challenge. Alternatively, other new emerging strategies, such as dual-target drug, drug repurposing, and combination strategies, may provide new insight into the improvement of TNBC therapeutics. In this review, we focus on summarizing the current situation of a series of candidate small-molecule drugs in TNBC therapy, including single-target drugs, dual-target drugs, as well as drug repurposing and combination strategies that will together shed new light on the future directions targeting TNBC vulnerabilities with small-molecule drugs for future therapeutic purposes.

Isoharringtonine Induces Apoptosis of Non-Small Cell Lung Cancer Cells in Tumorspheroids via the Intrinsic Pathway

Lung cancer is the major cause of cancer-associated death worldwide, and development of new therapeutic drugs is needed to improve treatment outcomes. Three-dimensional (3D) tumorspheroids offer many advantages over conventional two-dimensional cell cultures due to the similarities to in vivo tumors. We found that isoharringtonine, a natural product purified from Cephalotaxus koreana Nakai, significantly inhibited the growth of tumorspheroids with NCI-H460 cells in a dose-dependent manner and induced apoptotic cell death in our 3D cell culture system. On the other hand, A549 tumorspheroids displayed low sensitivity to isoharringtonine-induced apoptosis. Nuclear receptor subfamily 4 group A member 1 (NR4A1) is an orphan nuclear receptor known to regulate proliferation and apoptosis of cancer cells. We observed that knockdown of NR4A1 dramatically increased isoharringtonine-induced cancer cell death in A549 tumorspheroids by activating the intrinsic apoptosis pathway. Furthermore, treatment with combined isoharringtonine and iNR4A1 significantly inhibited multivulva formation in a Caenorhabditis elegans model and tumor development in a xenograft mouse model. Taken together, our data suggest that isoharringtonine is a potential natural product for treatment of non-small cell lung cancers, and inhibition of NR4A1 sensitizes cancer cells to anti-cancer treatment.

Role of STAT3 signaling pathway in breast cancer

Breast cancer has grown to be the second leading cause of cancer-related deaths in women. Only a few treatment options are available for breast cancer due to the widespread occurrence of chemoresistance, which emphasizes the need to discover and develop new methods to treat this disease. Signal transducer and activator of transcription 3 (STAT3) is an early tumor diagnostic marker and is known to promote breast cancer malignancy. Recent clinical and preclinical data indicate the involvement of overexpressed and constitutively activated STAT3 in the progression, proliferation, metastasis and chemoresistance of breast cancer. Moreover, new pathways comprised of upstream regulators and downstream targets of STAT3 have been discovered. In addition, small molecule inhibitors targeting STAT3 activation have been found to be efficient for therapeutic treatment of breast cancer. This systematic review discusses the advances in the discovery of the STAT3 pathways and drugs targeting STAT3 in breast cancer. Video abstract.

STAT3 as a potential therapeutic target in triple negative breast cancer: a systematic review

Triple negative breast cancer (TNBC), which is typically lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), represents the most aggressive and mortal subtype of breast cancer. Currently, only a few treatment options are available for TNBC due to the absence of molecular targets, which underscores the need for developing novel therapeutic and preventive approaches for this disease. Recent evidence from clinical trials and preclinical studies has demonstrated a pivotal role of signal transducer and activator of transcription 3 (STAT3) in the initiation, progression, metastasis, and immune evasion of TNBC. STAT3 is overexpressed and constitutively activated in TNBC cells and contributes to cell survival, proliferation, cell cycle progression, anti-apoptosis, migration, invasion, angiogenesis, chemoresistance, immunosuppression, and stem cells self-renewal and differentiation by regulating the expression of its downstream target genes. STAT3 small molecule inhibitors have been developed and shown excellent anticancer activities in in vitro and in vivo models of TNBC. This review discusses the recent advances in the understanding of STAT3, with a focus on STAT3’s oncogenic role in TNBC. The current targeting strategies and representative small molecule inhibitors of STAT3 are highlighted. We also propose potential strategies that can be further examined for developing more specific and effective inhibitors for TNBC prevention and therapy.