Homoharringtonine inhibits the AKT pathway and induces in vitro and in vivo cytotoxicity in human multiple myeloma cells

Synergism of BCL-2 family inhibitors facilitates selective elimination of senescent cells

Accumulation of senescent cells in tissues with advancing age participates in the pathogenesis of several human age-associated diseases. Specific senescent secretome, the resistance of senescent cells to apoptotic stimuli, and lack of immune system response contribute to the accumulation of senescent cells and their adverse effects in tissues. Inhibition of antiapoptotic machinery, augmented in senescent cells, by BCL-2 protein family inhibitors represents a promising approach to eliminate senescent cells from tissues. This study aimed to explore synergistic and selective senolytic effects of anti-apoptotic BCL-2 family targeting compounds, particularly BH3 mimetics.

Using human non-transformed cells RPE-1, BJ, and MRC-5 brought to ionizing radiation-, oncogene-, drug-induced and replicative senescence, we found synergy in combining MCL-1 selective inhibitors with other BH3 mimetics. In an attempt to uncover the mechanism of such synergy, we revealed that the surviving subpopulation of cells resistant to individually applied ABT-737/ABT-263, MIK665, ABT-199, and S63845 BCL-2 family inhibitors showed elevated MCL-1 compared to untreated control cells indicating the presence of a subset of cells expressing high MCL-1 levels and, therefore, resistant to BCL-2 inhibitors within the original population of senescent cells.

Overall, we found that combining BCL-2 inhibitors can be beneficial for eliminating senescent cells, thereby enabling use of lower, potentially less toxic, doses of drugs compared to monotherapy, thereby overcoming the resistance of the subpopulation of senescent cells to monotherapy.

Curcumin in Combination With Omacetaxine Suppress Lymphoma Cell Growth, Migration, Invasion, and Angiogenesis via Inhibition of VEGF/Akt Signaling Pathway

Background

Both omacetaxine (HHT) and curcumin were shown to exhibit anti-proliferative effect on lymphoma cells. However, the role of combination of HHT with curcumin (HHT/curcumin combination) on lymphoma cells remains unclear. Thus, this study aimed to investigate the effect of HHT/curcumin combination on the proliferation, migration, and angiogenesis of lymphoma cells.

Methods

Cell counting kit-8 (CCK-8), Ki67 immunofluorescence and transwell assays were used to assess the viability, proliferation and migration of U937 and Raji cells respectively. In addition, tube formation assay was used to determine the effects of HHT/curcumin combination on angiogenesis in human umbilical vein endothelial cells (HUVECs).

Results

In this study, we found that HHT/curcumin combination significantly inhibited the proliferation, migration and invasion in U937 and Raji cells (all P < 0.01). In addition, combination treatment markedly inhibited the secreted levels of vascular endothelial growth factor (VEGF)-(A-D) (all P < 0.01) in Raji cells. Moreover, combination treatment exhibited anti-tumor effects in Raji cells, as shown by the decreased signals of phosphorylated VEGF receptor 2 (p-VEGFR2) and phosphorylated protein kinase B (p-Akt) (all P < 0.01). Meanwhile, combination treatment inhibited VEGFA levels (P < 0.01) in exosomes derived from Raji cells. Application of exosomes with downregulated VEGF to HUVECs notably inhibited proliferation, migration and tube formation of HUVECs, evidenced by the decreased signals of p-Akt, angiogenin-1, matrix metallopeptidase 2 (MMP2) and matrix metallopeptidase 9 (MMP9) (all P < 0.01).

Conclusion

Our findings indicated that combination of HHT and curcumin could inhibit lymphoma cell growth and angiogenesis via inhibition of VEGF/Akt signaling pathway. These results suggested that HHT combined with curcumin might be regarded as a promising therapeutic approach for the treatment of lymphoma.

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 synergizes with quizartinib in FLT3-ITD acute myeloid leukemia by targeting FLT3-AKT-c-Myc pathway

Acute myeloid leukemia (AML) with FLT3 internal tandem duplication (FLT3-ITD) has a dismal prognosis. FLT3 inhibitors have been developed to treat patients with FLT3-ITD AML; however, when used alone, their efficacy is insufficient. FLT3 inhibitors combined with chemotherapy may be a promising treatment for FLT3-ITD AML. Homoharringtonine (HHT) is a classical anti-leukaemia drug with high sensitivity to FLT3-ITD AML cells. Here, we showed that HHT synergizes with a selective next-generation FLT3 inhibitor, quizartinib, to inhibit cell growth/viability and induce cell-cycle arrest and apoptosis in FLT3-ITD AML cells in vitro, significantly inhibit acute myeloid leukemia progression in vivo, and substantially prolong survival of mice-bearing human FLT3-ITD AML. Mechanistically, HHT and quizartinib cooperatively inhibit FLT3-AKT and its downstream targets GSK3β, c-Myc, and cyclin D1, cooperatively up-regulate the pro-apoptosis proteins Bim and Bax, and down-regulate the anti-apoptosis protein Mcl1. Most strikingly, HHT and quizartinib cooperatively reduce the numbers of side-population (SP) and aldehyde dehydrogenase (ALDH)-positive cells, which reportedly are rich in LSCs. In conclusion, HHT combined with quizartinib may be a promising treatment strategy for patients with FLT3-ITD AML.

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.

Homoharringtonine Exerts an Antimyeloma Effect by Promoting Excess Parkin-Dependent Mitophagy

Purpose

Homoharringtonine (HHT) has been used as an antileukemia agent in the clinic which processes a high-potential therapeutic efficacy against multiple myeloma (MM). In this study, we investigated the antimyeloma mechanism of HHT.

Methods

Three MM cell lines and a xenograft model were applied. Mitochondrial function was evaluated by detecting MitoTracker Green, the mtDNA copy number, mitochondrial protein and enzyme activity, the mitochondrial membrane potential and mitochondrial morphology. Mitophagy levels were assessed by monitoring autophagosomes, performing a colocalization analysis and determining the levels of related proteins. An shRNA was applied to knockdown Parkin.

Results

Based on the results of the in vitro experiments, HHT exerted a promising antiproliferative effect on the MM.1S, RPMI 8226 and H929 cell lines by increasing mitophagy. In addition, HHT markedly inhibited myeloma tumor growth and prolonged survival by promoting mitophagy in vivo. Furthermore, HHT treatment contributed to notable mitochondrial dysfunction and Parkin-dependent mitophagy, as evidenced by the destruction of mitochondria, the decrease in the mtDNA copy number, decrease in the Bcl-2/Bax ratio, and decrease in the levels of mitochondrial proteins and the optimal expression of Parkin and NDP52. However, the addition of rapamycin did not produce significant synergistic effect with HHT, indicating that HHT reached the threshold level to induce mitophagy. The colocalization analysis and assessment of mitochondrial function examination further confirmed that HHT triggered mitophagy and mitochondrial dysfunction. Moreover, the antiproliferative effect of HHT was reversed by an shRNA targeting Parkin, highlighting the indispensable role of Parkin-dependent mitophagy in the antimyeloma effect of HHT.

Conclusion

HHT exerts an antimyeloma effect by inducing excess mitophagy, providing new mechanistic insights into a therapeutic strategy for MM.

Exploiting Protein Translation Dependence in Multiple Myeloma with Omacetaxine-Based Therapy

PURPOSE

The prognosis of patients with multiple myeloma who are resistant to proteasome inhibitors, immunomodulatory drugs (IMiD), and daratumumab is extremely poor. Even B-cell maturation antigen-specific chimeric antigen receptor T-cell therapies provide only a temporary benefit before patients succumb to their disease. In this article, we interrogate the unique sensitivity of multiple myeloma cells to the alternative strategy of blocking protein translation with omacetaxine.

EXPERIMENTAL DESIGN

We determined protein translation levels (n = 17) and sensitivity to omacetaxine (n = 51) of primary multiple myeloma patient samples. Synergy was evaluated between omacetaxine and IMiDs in vitro, ex vivo, and in vivo. Underlying mechanism was investigated via proteomic analysis.

RESULTS

Almost universally, primary patient multiple myeloma cells exhibit >2.5-fold increased rates of protein translation compared with normal marrow cells. Ex vivo treatment with omacetaxine resulted in >50% reduction in viable multiple myeloma cells. In this cohort, high levels of translation serve as a biomarker for patient multiple myeloma cell sensitivity to omacetaxine. Unexpectedly, omacetaxine demonstrated synergy with IMiDs in multiple myeloma cell lines in vitro. In addition, in an IMiD-resistant relapsed patient sample, omacetaxine/IMiD combination treatment resensitized the multiple myeloma cells to the IMiD. Proteomic analysis found that the omacetaxine/IMiD combination treatment produced a double-hit on the IRF4/c-MYC pathway, which is critical to multiple myeloma survival.

CONCLUSIONS

Overall, protein translation inhibitors represent a potential new drug class for myeloma treatment and provide a rationale for conducting clinical trials with omacetaxine alone and in combination with IMiDs for patients with relapsed/refractory multiple myeloma.

Apoptotic and cell cycle response to homoharringtonine and harringtonine in wild and mutant p53 hepatocarcinoma cells

This study aimed to evaluate the modes of action of harringtonine (HT) and homoharringtonine (HHT) alkaloids in cell with wild (HepG2/C3A) and mutant p53 (HuH-7.5). We performed assays for cytotoxicity, genotoxicity, induction of apoptosis, cell cycle phase, and membrane integrity. Obtained data were compared with the relative expression of mRNA of genes related to proliferation, apoptosis, cell cycle control, metabolism of xenobiotics, and reticulum endoplasmic stress. The relative expression of the genes showed an increase in apoptosis-inducing mRNAs, such as TNF and BBC3, as well as a reduction in BCL2 and BAK. The mRNAs of CYP2E1 and CYP2C19 xenobiotic metabolism genes increased in both lineages, while CYP3A4 increased only in the HuH-7.5 lineage. The mRNA expression of endoplasmic reticulum (ER) stress genes (ERN1 and EIF2AK3) was shown to increase in HHT and HT treatments. A similar increase was recorded in the mRNA expression of the TRAF2 gene. The changes observed in this study support the hypothesis that ER stress was more strongly associated with TNF induction, causing cell death by apoptosis in p53 mutant cells. This result with wild and mutant p53 cells may have clinical implications in the use of these compounds.

Methyl-indole inhibits pancreatic cancer cell viability by down-regulating ZFX expression

This study explored the effect of methyl-indole on pancreatic cancer cell viability and investigated the mechanism involved. The viability of pancreatic cells showed a significant suppression on treatment with methyl-indole in dose-based manner. Treatment with 5 µM methyl-indole suppressed Capan-1 cell viability to 23%. The viability of Aspc-1 cells was reduced to 20% and those of MIApaCa-2 cells to 18% by 5 µM methyl-indole. The apoptotic proportion of Capan-1 cells was 67%, while as those of Aspc-1 and MIApaCa-2 cells increased to 72 and 77%, respectively, on treatment with 5 µM methyl-indole. The level of P13K, p-Tyr, p-Crkl and p-Akt was inhibited in the cells by methyl-indole. Moreover, methyl-indole also suppressed zinc-finger protein, X-linked mRNA and protein expression in tested cells. In summary, methyl-indole exhibits anti-proliferative effect on pancreatic cancer cells and induces apoptosis. It targeted ZFX expression and down-regulated P13K/AKT pathway in pancreatic cancer cells. Therefore, methyl-indole acts as therapeutic agent for pancreatic cancer and may be studied further.

Homoharringtonine enhances the effect of imatinib on chronic myelogenous leukemia cells by downregulating ZFX

Homoharringtonine (HHT) and imatinib have a synergistic effect in the clinical treatment of chronic myeloid leukemia (CML). The purpose of the present study was to explore the underlying mechanisms by which HHT enhanced imatinib sensitivity. K562 CML cells were treated with HHT and imatinib separately or in combination. Cell viability was detected by Cell Counting Kit-8 assay; apoptotic rates and protein expression levels of phosphorylated-tyrosine (p-Tyr) and p-CRK like proto-oncogene, adaptor protein (p-Crkl) were analyzed by flow cytometry; zinc-finger protein, X-linked (ZFX) overexpression plasmid was transfected to cells using electroporation; western blotting was used to detect the protein expression levels of PI3K, AKT, p-AKT and ZFX; and reverse transcription-quantitative PCR was used to measure ZFX mRNA expression levels. The results demonstrated that HHT and imatinib co-treatment had significant effects of proliferation inhibition and apoptosis induction on K562 CML cells compared with imatinib alone. Co-treatment also significantly downregulated the expression levels of p-Tyr, p-Crkl, PI3K and p-Akt compared with imatinib or HHT treatment. In addition, HHT downregulated ZFX mRNA and protein expression. ZFX overexpression reversed cell sensitivity to imatinib and HHT and also reduced the HHT-induced imatinib sensitization by increasing p-Akt expression. In conclusion, HHT may enhance the effect of imatinib on CML cells by downregulating ZFX.

Homoharringtonine regulates the alternative splicing of Bcl-x and caspase 9 through a protein phosphatase 1-dependent mechanism

BACKGROUND

Homoharringtonine (HHT) is a natural alkaloid with potent antitumor activity, but its precise mechanism of action is still poorly understood.

METHODS

We examined the effect of HHT on alternative splicing of Bcl-x and Caspase 9 in various cells using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The mechanism of HHT-affected alternative splicing in these cells was investigated by treatment with protein phosphatase inhibitors and overexpression of a protein phosphatase.

RESULTS

Treatment with HHT downregulated the levels of anti-apoptotic Bcl-xL and Caspase 9b mRNA with a concomitant increase in the mRNA levels of pro-apoptotic Bcl-xS and Caspase 9a in a dose- and time-dependent manner. Calyculin A, an inhibitor of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A), significantly inhibited the effects of HHT on the alternative splicing of Bcl-x and Caspase 9, in contrast to okadaic acid, a specific inhibitor of PP2A. Overexpression of PP1 resulted in a decrease in the ratio of Bcl-xL/xS and an increase in the ratio of Caspase 9a/9b. Moreover, the effects of HHT on Bcl-x and Caspase 9 splicing were enhanced in response to PP1 overexpression. These results suggest that HHT-induced alternative splicing of Bcl-x and Caspase 9 is dependent on PP1 activation. In addition, overexpression of PP1 could induce apoptosis and sensitize MCF7 cells to apoptosis induced by HHT.

CONCLUSION

Homoharringtonine regulates the alternative splicing of Bcl-x and Caspase 9 through a PP1-dependent mechanism. Our study reveals a novel mechanism underlying the antitumor activities of HHT.

PI3K/Akt inhibitor LY294002 potentiates homoharringtonine antimyeloma activity in myeloma cells adhered to stromal cells and in SCID mouse xenograft

Homoharringtonine (HHT) is a known anti-leukemia drug that inhibits multiple myeloma (MM) cells both in vitro and in vivo. Our prior study demonstrated that the potency of HHT in MM cells was compromised significantly when myeloma cells were co-cultured with BM stromal cells. This study aimed to investigate whether PI3K/Akt inhibitor LY294002 could potentiate the antimyeloma activity of HHT against MM cells adhered to BM stromal cells and in vivo xenograft models. A co-culture system composed of MM cells and human stromal cells was employed to mimic MM cells in bone marrow niche. The inhibitory and pro-apoptotic effect of HHT and LY294002 was determined by CCK-8 assay or flow cytometry. Expression of PI3K/Akt signaling molecules and anti-apoptotic protein myeloid cell leukemia-1 (Mcl-1) was assessed by western blot analysis and/or reverse transcription real-time quantitative PCR (RT-qPCR). MM xenografts were used to evaluate antitumor effect of combined therapy with HHT and LY294002. Adhesion to BM stromal cells rendered MM cells resistant to HHT whereas silencing Mcl-1 partly reversed the resistance. LY294002 induced apoptosis in MM cells and potentiated the antimyeloma effects of HHT by inhibiting the PI3K/Akt signal pathway which was abnormally activated during adhesion. LY294002 also enhanced the antimyeloma effect of HHT in in vivo xenograft models. These findings suggest that activation of PI3K/Akt signal pathway was responsible for the resistance to HHT in MM cells adhered to stromal cells. LY294002 can potentiate the antimyeloma activity of HHT both in vitro and in vivo, which may represent a new clinical treatment in MM.

Mechanisms of Resistance in Multiple Myeloma

Multiple myeloma (MM) is an incurable hematopoietic cancer that is characterized by malignant plasma cell infiltration of the bone marrow and/or extramedullary sites. Multi-modality approaches including "novel agents," traditional chemotherapy, and/or stem cell transplantation are used in MM therapy. Drug resistance, however, ultimately develops and the disease remains incurable for the vast majority of patients. In this chapter, we review both tumor cell-autonomous and non-autonomous (microenvironment-dependent) mechanisms of drug resistance. MM provides an attractive paradigm highlighting a number of current concepts and challenges in oncology. Firstly, identification of MM cancer stem cells and their unique drug resistance attributes may provide rational avenues towards MM eradication and cure. Secondly, the oligoclonal evolution of MM and alternation of "clonal tides" upon therapy challenge our current understanding of treatment responses. Thirdly, the success of MM "novel agents" provides exemplary evidence for the impact of therapies that target the immune and non-immune microenvironment. Fourthly, the rapid pace of drug approvals for MM creates an impetus for development of precision medicine strategies and biomarkers that promote efficacy and mitigate toxicity and cost. While routine cure of the disease remains the ultimate and yet unattainable prize, MM advances in the last 10-15 years have provided an astounding paradigm for the treatment of blood cancers in the modern era and have radically transformed patient outcomes.

Cephalotaxus Alkaloids

Cephalotaxus alkaloids represent a family of plant secondary metabolites known for 60 years. Significant activity against leukemia in mice was demonstrated for extracts of Cephalotaxus. Cephalotaxine (CET) (1), the major alkaloid of this series was isolated from Cephalotaxus drupacea species by Paudler in 1963. The subsequent discovery of promising antitumor activity among new Cephalotaxus derivatives reported by Chinese, Japanese, and American teams triggered extensive structure elucidation and biological studies in this family. The structural feature of this cephalotaxane family relies mainly on its tetracyclic alkaloid backbone, which comprises an azaspiranic 1-azaspiro[4.4]nonane unit (rings C and D) and a benzazepine ring system (rings A and B), which is linked by its C3 alcohol function to a chiral oxygenated side chain by a carboxylic function alpha to a tetrasubstituted carbon center. The botanical distribution of these alkaloids is limited to the Cephalotaxus genus (Cephalotaxaceae). The scope of biological activities of the Cephalotaxus alkaloids is mainly centered on the antileukemic activity of homoharringtonine (HHT) (2), which in particular demonstrated marked benefits in the treatment of orphan myeloid leukemia and was approved as soon as 2009 by European Medicine Agency and by US Food and Drug Administration in 2012. Its exact mechanism of action was partly elucidated and it was early recognized that HHT (2) inhibited protein synthesis at the level of the ribosome machinery. Interestingly, after a latency period of two decades, the topic of Cephalotaxus alkaloids reemerged as a prolific source of new natural structures. To date, more than 70 compounds have been identified and characterized. Synthetic studies also regained attention during the past two decades, and numerous methodologies were developed to access the first semisynthetic HHT (2) of high purity suitable for clinical studies, and then high grade enantiomerically pure CET (1), HHT (2), and analogs.

Novel phosphatidylinositol 3-kinase inhibitor BKM120 enhances the sensitivity of multiple myeloma to bortezomib and overcomes resistance

Proteasome inhibitor bortezomib has proven efficacy against multiple myeloma. However, bortezomib activates the phosphatidylinositol 3-kinase/AKT (PI3K/AKT) pathway (which is essential to the development of myeloma), often resulting in drug resistance and disease recurrence. The addition of BKM120 significantly enhanced the apoptotic effects of bortezomib in both bortezomib-sensitive and bortezomib-resistant cells. Treatment with bortezomib alone increased the phosphorylation of AKT (P-AKT), whereas the addition of BKM120 markedly downregulated P-AKT in both bortezomib-sensitive and bortezomib-resistant cells. The clinical relevance of combined treatment with bortezomib and BKM120 was investigated in a xenograft mouse model and in myeloma patients, and the synergy of the combination was confirmed. In conclusion, the addition of BKM120 enhanced the sensitivity of myeloma cells to bortezomib.

Synergistic Effect and Molecular Mechanism of Homoharringtonine and Bortezomib on SKM-1 Cell Apoptosis

Background

Myelodysplastic syndromes (MDS) are clonal marrow stem-cell disorders with a high risk of progression to acute myeloid leukemia (AML). Treatment options are limited and targeted therapies are not available for MDS. In the present study, we investigated the cytotoxicity and the molecular mechanism of Homoharringtonine (HHT) and Bortezomib towards high-risk MDS cell line SKM-1 in vitro and the role of miR-3151 was first evaluated in SKM-1 cells.

Methods

SKM-1 cells were treated with different concentrations of HHT or Bortezomib, and cell viability was analyzed with CCK-8 assay. The influence on cell proliferation, cell cycle distribution and the percentage of apoptosis cells were analyzed by flow cytometry. Calcusyn software was used to calculate combination index (CI) values. Western blot was used to analysis phosphorylation of Akt and nuclear NF-κB protein expression in SKM-1 cells. Mature miR-3151 level and p53 protein level were detected after HHT or Bortezomib treatment. The cell proliferation and p53 protein level were reassessed in SKM-1 cells infected with lentivirus to overexpress miR-3151.

Results

Simultaneous exposure to HHT and Bortezomib (10.4:1) resulted in a significant reduction of cell proliferation in SKM-1 cells (P < 0.05). Cell cycle arrest at G0/G1 and G2/M phase was observed (P < 0.05). HHT and Bortezomib synergistically induced cell apoptosis by regulating members of caspase 9, caspase 3 and Bcl-2 family (P < 0.01). The mechanisms of the synergy involved Akt and NF-κB signaling pathway inhibition, downregulation of mature miR-3151 and increment of downstream p53 protein level. Overexpression of miR-3151 promoted cell proliferation and inhibited p53 protein expression in SKM-1 (P < 0.01).

Conclusions

HHT and Bortezomib synergistically inhibit SKM-1 cell proliferation and induce apoptosis in vitro. Inhibition of Akt and NF-κB pathway signaling contribute to molecular mechanism of HHT and Bortezomib. miR-3151 abundance is implicated in SKM-1 cell viability, cell proliferation and p53 protein expression.

Efficacy and safety of homoharringtonine plus cytarabine and aclarubicin for patients with myelodysplastic syndrome-RAEB

The aim of the present study was to evaluate the treatment outcome of homoharringtonine, cytarabine (AraC) and aclarubicin combination therapy as induction treatment for myelodysplastic syndromes-refractory anemia with excess blasts (MDS-RAEB). A total of 24 patients with MDS-RAEB who were aged between 18 and 66 years were treated with homoharringtonine, AraC and aclarubicin (HAA regimen). The HAA regimen consisted of homoharringtonine (2 mg/m² intramuscularly twice daily, days 1-3), AraC (75 mg/m² injected subcutaneously twice daily, days 1-7) and aclarubicin (12 mg/m², days 1-7). The overall response rate was 79% with a complete remission rate of 58.3% and partial remission rate of 20.7%. There was no evidence of early mortality in this group of patients. The median overall survival (OS) was 36.2 months (95% confidence interval, 24.6-47.4 months), and the estimated three year overall survival rate was 45.8%. In conclusion, HAA combination therapy is a suitable induction regimen for patients with MDS-RAEB, which may improve the outcome for de novo higher-risk MDS patients, particularly of those with favorable and intermediate cytogenetics.

Homoharringtonine induces apoptosis and inhibits STAT3 via IL-6/JAK1/STAT3 signal pathway in Gefitinib-resistant lung cancer cells

Tyrosine kinase inhibitors (TKIs) are mostly used in non-small cell lung cancer (NSCLC) treatment. Unfortunately, treatment with Gefitinib for a period of time will result in drug resistance and cause treatment failure in clinic. Therefore, exploring novel compounds to overcome this resistance is urgently required. Here we investigated the antitumor effect of homoharringtonine (HHT), a natural compound extracted from Cephalotaxus harringtonia, on Gefitinib-resistant NSCLC cell lines in vitro and in vivo. NCI-H1975 cells with EGFR T790M mutation are more sensitive to HHT treatment compared with that of A549 cells with wild type EGFR. HHT inhibited cells growth, cell viability and colony formation, as well as induced cell apoptosis through mitochondria pathway. Furthermore, we explored the mechanism of HHT inhibition on NSCLC cells. Higher level of interleukin-6 (IL-6) existed in lung cancer patients and mutant EGFR and TGFβ signal requires the upregulation of IL-6 through the gp130/JAK pathway to overactive STAT3, an oncogenic protein which has been considered as a potential target for cancer therapy. HHT reversiblely inhibited IL-6-induced STAT3 Tyrosine 705 phosphorylation and reduced anti-apoptotic proteins expression. Gefitinib-resistant NSCLC xenograft tests also confirmed the antitumor effect of HHT in vivo. Consequently, HHT has the potential in Gefitinib-resistant NSCLC treatment.

LC-based targeted metabolomics analysis of nucleotides and identification of biomarkers associated with chemotherapeutic drugs in cultured cell models

Treatment of mammalian cells with chemotherapeutic drugs can result in perturbations of nucleotide pools. Monitoring these perturbations in cultured tumor cells from human sources is useful for assessment of the effect of drug therapy and a better understanding of the mechanism of action of these drugs. In this study, three classes of chemotherapeutic drugs with different mechanisms of action were used in the development of drug-treated cell models. The LC-based targeted metabolomics analysis of nucleotides in cells of the control group and the drug-treated group was carried out. Several data processing methods were combined for the identification of potential biomarkers associated with the action of drugs, including one-way analysis of variance, principal component analysis, and receiver operating characteristic curves. Intriguingly, tumor cells of both the control group and the drug-treated groups can be distinguished from each other, and several variables were recognized as potential biomarkers, such as ATP, GMP, and UDP for antimetabolite agents, ATP, GMP, and CTP for DNA-damaging agents, as well as GMP, ATP, UDP, and GDP for the mitotic spindle agents. Further validation of the potential biomarkers was performed using the receiver operating characteristic curve. Considering their corresponding area under the curve, which was larger than 0.9, it can be concluded that GMP and ATP are the best potential biomarkers for DNA-damaging drugs, as well as GMP, ATP, and UDP for the other two classes of drugs. This limited nucleotide approach cannot completely distinguish the mechanisms of the nine drugs, but it provides preliminary evidence for the role of pharmacometabolomics in the preclinical development of drugs at least.

Omacetaxine mepesuccinate in the treatment of intractable chronic myeloid leukemia

In a significant proportion of patients with chronic myeloid leukemia, resistance to BCR-ABL tyrosine kinase inhibitors develops due to acquisition of BCR-ABL kinase domain mutations and insensitivity of leukemia stem cells to tyrosine kinase inhibitors. Omacetaxine mepesuccinate (formerly called homoharringtonine) is a natural alkaloid that inhibits protein synthesis and induces cell death. Omacetaxine mepesuccinate has been recently approved by the US Food and Drug Administration to treat patients with chronic myeloid leukemia who failed to respond to multiple tyrosine kinase inhibitors and/or acquired the BCR-ABL-T315I mutation. In this review, we discuss the use and effectiveness of omacetaxine mepesuccinate in the treatment of chronic myeloid leukemia, with coverage of its pharmacology, mode of action, and pharmacokinetics. We believe that omacetaxine mepesuccinate will be beneficial to many patients with chronic myeloid leukemia who do not respond well to tyrosine kinase inhibitors.

The plant alkaloid and anti-leukemia drug homoharringtonine sensitizes resistant human colorectal carcinoma cells to TRAIL-induced apoptosis via multiple mechanisms

TNF-related apoptosis-inducing ligand (TRAIL) is a pro-apoptotic ligand from the TNF-alpha family that is under consideration, along with agonistic anti-TRAIL receptor antibodies, as a potential anti-tumor agent. However, most primary human tumors are resistant to monotherapy with TRAIL apoptogens, and thus the potential applicability of TRAIL in anti-tumor therapy ultimately depends on its rational combination with drugs targeting these resistances. In our high-throughput screening for novel agents/drugs that could sensitize TRAIL-resistant colorectal cancer cells to TRAIL-induced apoptosis, we found homoharringtonine (HHT), a cephalotaxus alkaloid and tested anti-leukemia drug, to be a very effective, low nanomolar enhancer of TRAIL-mediated apoptosis/growth suppression of these resistant cells. Co-treatment of TRAIL-resistant RKO or HT-29 cells with HHT and TRAIL led to the effective induction of apoptosis and the complete elimination of the treated cells. HHT suppressed the expression of the anti-apoptotic proteins Mcl-1 and cFLIP and enhanced the TRAIL-triggered activation of JNK and p38 kinases. The shRNA-mediated down-regulation of cFLIP or Mcl-1 in HT-29 or RKO cells variably enhanced their TRAIL-induced apoptosis but it did not markedly sensitize them to TRAIL-mediated growth suppression. However, with the notable exception of RKO/sh cFLIP cells, the downregulation of cFLIP or Mcl-1 significantly lowered the effective concentration of HHT in HHT + TRAIL co-treatment. Combined HHT + TRAIL therapy also led to the strong suppression of HT-29 tumors implanted into immunodeficient mice. Thus, HHT represents a very efficient enhancer of TRAIL-induced apoptosis with potential application in TRAIL-based, anti-cancer combination therapy.

Anticancer drugs from traditional toxic Chinese medicines

Many anticancer drugs are obtained from natural sources. Nature produces a variety of toxic compounds, which are often used as anticancer drugs. Up to now, there are at least 120 species of poisonous botanicals, animals and minerals, of which more than half have been found to possess significant anticancer properties. In spite of their clinical toxicity, they exhibit pharmacological effects and have been used as important traditional Chinese medicines for the different stages of cancer. The article reviews many structures such as alkaloids of Camptotheca acuminata, Catharanthus roseus and Cephalotaxus fortunei, lignans of Dysosma versipellis and Podophyllum emodi, ketones of Garcinia hanburyi, terpenoids of Mylabris and Ginkgo biloba, diterpenoids of Tripterygium wilfordii, Euphorbia fischeriana, Euphorbia lathyris, Euphorbia kansui, Daphne genkwa, Pseudolarix kaempferi and Brucea javanica, triterpenoids of Melia toosendan, steroids of Periploca sepium, Paris polyphylla and Venenum Bufonis, and arsenic compounds including Arsenicum and Realgar. By comparing their related phytochemistry, toxic effects and the recent advances in understanding the mechanisms of action, this review puts forward some ideals and examples about how to increase antitumour activity and/or reduce the side effects experienced with Chinese medicine.

Responses in mantle cell lymphoma cells to SNS-032 depend on the biological context of each cell line

SNS-032 is a potent inhibitor of cyclin-dependent kinases (Cdk) 2, 7, and 9 that regulate the cell cycle and transcription. Our studies in indolent primary chronic lymphocytic leukemia cells showed that SNS-032 inhibited transcription, diminished the antiapoptotic protein Mcl-1, and induced apoptosis. The present study focuses on evaluating this compound in four proliferating mantle cell lymphoma lines (Jeko-1, Granta 519, Mino, and SP-53). Consistent with its action against Cdk9 and Cdk7, SNS-032 inhibited the phosphorylation of RNA pol II in all four lines and blocked RNA synthesis. The transcripts and protein levels of short-lived proteins decreased, including cyclin D1 and Mcl-1. Cell growth was inhibited in a concentration-dependent manner in all lines. Apoptosis was induced in JeKo-1, Mino, and SP-53 cells without disrupting cell cycle distribution. However, apoptosis was limited in Granta cells; rather, there was a significant reduction of clonogenic survival. Small interfering RNA was used to specifically knock down Mcl-1 and cyclin D1 in JeKo-1 and Granta cells. Knocking down Mcl-1 induced significant apoptosis in Jeko-1 cells but not Granta cells. Reducing cyclin D1, rather than Mcl-1, was associated with loss of clonogenic survival in Granta cells. Thus, these results indicated that mantle cell lymphoma cell lines have distinct mechanisms sustaining their survival, and the mechanism of action of SNS-032 is dependent on the biological context of an individual line.

The continuing search for antitumor agents from higher plants

Plant secondary metabolites and their semi-synthetic derivatives continue to play an important role in anticancer drug therapy. In this short review, selected single chemical entity antineoplastic agents from higher plants that are currently in clinical trials as cancer chemotherapy drug candidates are described. These compounds are representative of a wide structural diversity. In addition, the approaches taken toward the discovery of anticancer agents from tropical plants in the laboratory of the authors are summarized. The successful clinical utilization of cancer chemotherapeutic agents from higher plants has been evident for about half a century, and, when considered with the promising pipeline of new plant-derived compounds now in clinical trials, this augurs well for the continuation of drug discovery research efforts to elucidate additional candidate substances of this type.