Etoposide-resistant human colon and lung adenocarcinoma cell lines exhibit sensitivity to homoharringtonine

Homoharringtonine: updated insights into its efficacy in hematological malignancies, diverse cancers and other biomedical applications

HHT has emerged as a notable compound in the realm of cancer treatment, particularly for hematological malignancies. Its multifaceted pharmacological properties extend beyond traditional applications, warranting an extensive review of its mechanisms and efficacy. This review aims to synthesize comprehensive insights into the efficacy of HHT in treating hematological malignancies, diverse cancers, and other biomedical applications. It focuses on elucidating the molecular mechanisms, therapeutic potential, and broader applications of HHT. A comprehensive search for peer-reviewed papers was conducted across various academic databases, including ScienceDirect, Web of Science, Scopus, American Chemical Society, Google Scholar, PubMed/MedLine, and Wiley. The review highlights HHT's diverse mechanisms of action, ranging from its role in leukemia treatment to its emerging applications in managing other cancers and various biomedical conditions. It underscores HHT's influence on cellular processes, its efficacy in clinical settings, and its potential to alter pathological pathways. HHT demonstrates significant promise in treating various hematological malignancies and cancers, offering a multifaceted approach to disease management. Its ability to impact various physiological pathways opens new avenues for therapeutic applications. This review provides a consolidated foundation for future research and clinical applications of HHT in diverse medical fields.

Cancer Chemotherapy via Natural Bioactive Compounds

BACKGROUND

Cancer-induced mortality is increasingly prevalent globally which skyrocketed the necessity to discover new/novel safe and effective anticancer drugs. Cancer is characterized by the continuous multiplication of cells in the human which is unable to control. Scientific research is drawing its attention towards naturally-derived bioactive compounds as they have fewer side effects compared to the current synthetic drugs used for chemotherapy.

OBJECTIVE

Drugs isolated from natural sources and their role in the manipulation of epigenetic markers in cancer are discussed briefly in this review article.

METHODS

With advancing medicinal plant biotechnology and microbiology in the past century, several anticancer phytomedicines were developed. Modern pharmacopeia contains at least 25% herbal-based remedy including clinically used anticancer drugs. These drugs mainly include the podophyllotoxin derivatives vinca alkaloids, curcumin, mistletoe plant extracts, taxanes, camptothecin, combretastatin, and others including colchicine, artesunate, homoharringtonine, ellipticine, roscovitine, maytanasin, tapsigargin,andbruceantin.

RESULTS

Compounds (psammaplin, didemnin, dolastin, ecteinascidin,and halichondrin) isolated from marine sources and animals such as microalgae, cyanobacteria, heterotrophic bacteria, invertebrates. They have been evaluated for their anticancer activity on cells and experimental animal models and used chemotherapy.Drug induced manipulation of epigenetic markers plays an important role in the treatment of cancer.

CONCLUSION

The development of a new drug from isolated bioactive compounds of plant sources has been a feasible way to lower the toxicity and increase their effectiveness against cancer. Potential anticancer therapeutic leads obtained from various ethnomedicinal plants, foods, marine, and microorganisms are showing effective yet realistically safe pharmacological activity. This review will highlight important plant-based bioactive compounds like curcumin, stilbenes, terpenes, other polyphenolic phyto-compounds, and structurally related families that are used to prevent/ ameliorate cancer. However, a contribution from all possible fields of science is still a prerequisite for discovering safe and effective anticancer drugs.

Synergistic cytotoxicity of homoharringtonine and etoposide in acute myeloid leukemia cells involves disrupted antioxidant defense

Background/Aims

Cytotoxicity induced by reactive oxygen species (ROS) is critical for the effectiveness of chemotherapeutic drugs used in the treatment of acute myeloid leukemia (AML). This study aimed to investigate whether ROS contributes to cytotoxicity in AML cells when treated with homoharringtonine (HHT) and etoposide (ETP) in combination.

Methods

AML cell lines THP1 and HL60 and primary AML cells from patients were treated with HHT and ETP alone or in combination, and cell viability was determined by trypan blue exclusion test, and apoptosis was analyzed by annexin-V/propidium iodide double staining as well as Western blot for measuring expression of cleaved caspase-9 and cleaved caspase-3. Intracellular ROS level was detected by DCFH-DA fluorescence assay, and N-Acetyl-L-cysteine (NAC) was used to scavenge intracellular ROS. Retroviral infection was applied to mediate stable overexpression in AML cells.

Results

We show that HHT and ETP exhibit synergistic cytotoxicity in AML cell lines and primary AML cells in vitro, and meanwhile, HHT causes elevated ROS generation in ETP-treated AML cells. We next reveal that the elevated ROS is a critical factor for the synergistic cytotoxicity, since ROS scavenge by NAC remarkably diminishes this effect. Mechanistically, we demonstrate that HHT causes elevated ROS generation by disabling thioredoxin-mediated antioxidant defense. Finally, similar to HHT treatment, depletion of thioredoxin sensitizes AML to ETP treatment.

Conclusion

These results provide the foundation for augmenting the efficacy of ETP in treating AML with HHT, and also highlight the importance of targeting ROS in improving treatment outcome in AML.

Reversal of multidrug resistance by icaritin in doxorubicin-resistant human osteosarcoma cells

Multidrug resistance (MDR) is one of the major obstacles in cancer chemotherapy. Our previous study has shown that icariin could reverse MDR in MG-63 doxorubicin-resistant (MG-63/DOX) cells. It is reported that icariin is usually metabolized to icariside II and icaritin. Herein, we investigated the effects of icariin, icariside II, and icaritin (ICT) on reversing MDR in MG-63/DOX cells. Among these compounds, ICT exhibited strongest effect and showed no obvious cytotoxicity effect on both MG-63 and MG-63/DOX cells ranging from 1 to 10 μmol·L^-1. Furthermore, ICT increased accumulation of rhodamine 123 and 6-carboxyfluorescein diacetate and enhanced DOX-induced apoptosis in MG-63/DOX cells in a dose-dependent manner. Further studies demonstrated that ICT decreased the mRNA and protein levels of multidrug resistance protein 1 (MDR1) and multidrug resistance-associated protein 1 (MRP1). We also verified that blockade of STAT3 phosphorylation was involved in the reversal effect of multidrug resistance in MG-63/DOX cells. Taken together, these results indicated that ICT may be a potential candidate in chemotherapy for osteosarcoma.

The cell cycle phases of DNA damage and repair initiated by topoisomerase II-targeting chemotherapeutic drugs

Although cytostasis and cytotoxicity induced by cancer chemotherapy drugs targeting topoisomerase II (topoII) arise in specific cell cycle phases, it is unknown whether the drug-initiated DNA damage triggering these responses, or the repair (reversal) of this damage, differs between cell cycle phases or between drug classes. Accordingly, we used a flow cytometric alkaline unwinding assay to measure DNA damage (strand breakage (SB)) and SB repair in each cell cycle compartment of human cancer cell lines treated with clinically relevant concentrations of doxorubicin, daunomycin, etoposide, and mitoxantrone. We found that treated HeLa and A549 cells exhibited the greatest SB in G2/M phase, the least in G1 phase, and generally an intermediate amount in S phase. The cell cycle phase specificity of the DNA damage appeared to be predictive of the cell cycle phase of growth arrest. Furthermore, it appeared to be dependent on topoIIalpha expression as the extent of SB did not differ between cell cycle compartments in topoIIalpha-diminished A549(VP)28 cells. HeLa cells were apparently unable to repair doxorubicin-initiated SB. The rate of repair of etoposide-initiated SB in HeLa cells and of mitoxantrone-initiated SB in HeLa and A549 cells was similar in each cell cycle compartment. In A549 cells, the rate of repair of doxorubicin and etoposide-initiated SB differed between cell cycle phases. Overall, these results indicate that the cell cycle phase specificity of cytostasis and cytotoxicity induced in tumor cells by topoII-targeting drugs may be directly related to the cell cycle phase specificity of the drug-initiated DNA damage. Analysis by cell cycle compartment appears to clarify some of the intercellular heterogeneity in the extent of drug-initiated DNA damage and cytotoxicity previously observed in cancer cells analyzed as a single population; this approach might be useful in resolving inconsistent results reported in investigations of tumor cell topoII content versus response to topoII-targeting drugs.

Homoharringtonine: a new treatment option for myeloid leukemia

HHT, one of the alkaloids from a Chinese natural plant, Cephalotaxus, has shown its potential in leukemia treatment. This compound demonstrated strong growth-inhibiting activities in vitro and in animal experiments, and obtained encouraging results in some clonal proliferative disease such as in chronic myeloid leukemia (CML) and in polycythemia vera. Evidences also confirmed HHT as an apoptosis inducer in tumor cell lines and fresh cells from cancer patients. The CR rate reported with HHT-based regimen in acute nonlymphocytic leukemia showed no statistic differences from that with DNR-based regimen, although the case number was limited. While used in clinical trial, the drug often cause noticeably cardiovascular disturbances if be given rapidly by intravenous infusion. Myelosuppression is the common complication in HHT-based chemotherapy. Although with the anti-growth activity in vitro and praisable achievement in acute and chronic myeloid leukemia treatment, the drug shows no beneficial effect in lymphocytic leukemia and solid tumors. The underlying mechanism for the discrepancy of efficacy keeps unknown. This review will present with the preclinical research data including the action mechanism, pharmacokinetics and drug resistance of HHT as well as the result from the clinical trial with HHT in China and the United States.

Homoharringtonine mediates myeloid cell apoptosis via upregulation of pro-apoptotic bax and inducing caspase-3-mediated cleavage of poly(ADP-ribose) polymerase (PARP)

Homoharringtonine (HHT) is a plant alkaloid with antileukemia activity that is currently being used for treatment of acute, chronic leukemias and MDS. In this study, we show that HHT can induce apoptosis in a variety of human myeloid leukemia cell lines (U937, HL-60, HEL, THP, and K562). U937 and HL60 cells undergo rapid apoptosis on treatment with HHT, as indicated by increased annexin V binding capacity, caspase-3 activation, and cleavage of poly(ADP-ribose) polymerase (PARP). In addition, the expression of bax is upregulated during HHT-induced cell death, whereas the expression of bcl-2 is only slightly decreased. Importantly, treatment of primary leukemic cells, obtained from acute myeloid leukemia patients, resulted in rapid apoptosis. Thus, our data provide the mechanism of HHT and justify the use of HHT in the treatment of human myeloid leukemia.