Targeting CDK9 by wogonin and related natural flavones potentiates the anti-cancer efficacy of the Bcl-2 family inhibitor ABT-263

Wogonin induces mitochondrial apoptosis and synergizes with venetoclax in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is among the most aggressive hematological malignancies and patients are commonly treated with combinatorial immunochemotherapies such as R-CHOP. Till now, the prognoses are still variable and unsatisfactory, depending on the molecular subtype and the treatment response. Developing effective and tolerable new agents is always urgently needed, and compounds from a natural source have gained increasing attentions. Wogonin is an active flavonoid extracted from the traditional Chinese herbal medicine Scutellaria baicalensis Georgi and has shown extensive antitumor potentials. However, the therapeutic effect of wogonin on DLBCL remains unknown. Here, we found that treatment with wogonin dose- and time-dependently reduced the viability in a panel of established DLBCL cell lines. The cytotoxicity of wogonin was mediated through apoptosis induction, along with the loss of mitochondrial membrane potential and the downregulation of BCL-2, MCL-1, and BCL-xL. In terms of the mechanism, wogonin inhibited the PI3K and MAPK pathways, as evidenced by the clear decline in the phosphorylation of AKT, GSK3β, S6, ERK, and P38. Furthermore, the combination of wogonin and the BCL-2 inhibitor venetoclax elicited synergistically enhanced killing effect on DLBCL cells regardless of their molecular subtypes. Finally, administration of wogonin significantly impeded the progression of the DLBCL tumor in a xenograft animal model without obvious side effects. Taken together, the present study suggests a promising potential of wogonin in the treatment of DLBCL patients either as monotherapy or an adjuvant for venetoclax-based combinations.

Wogonin Inhibits Colorectal Cancer Proliferation and Epithelial Mesenchymal Transformation by Suppressing Phosphorylation in the AKT Pathway

Colorectal cancer is the third leading cause of cancer-related death worldwide. Hence, there is a need to identify new therapeutic agents to improve the current repertoire of therapeutic drugs. Wogonin, a flavonoid from the herbal medicine Scutellaria baicalensis, has unique antitumor activity. Our study aimed to further explore the inhibitory effects of wogonin on colorectal cancer and its specific mechanism. The results showed that wogonin significantly inhibited the proliferation of colorectal cancer cells as well as their ability to invade and metastasize. We detected phosphorylation of tumor-associated signaling pathways using a phosphorylated protein microarray and found that wogonin intervention significantly inhibited the phosphorylation level of the AKT protein in colorectal cancer cells. Through in vitro and in vivo experiments, it was confirmed that wogonin exerted its antitumor effects against colorectal cancer by inhibiting phosphorylation in the AKT pathway. Our discovery of wogonin as an inhibitor of AKT phosphorylation provides new opportunities for the pharmacological treatment of colorectal cancer.

A systematic review on understanding the mechanistic pathways and clinical aspects of natural CDK inhibitors on cancer progression.: Unlocking cellular and biochemical mechanisms

Cell division, differentiation, and controlled cell death are all regulated by phosphorylation, a key biological function. This mechanism is controlled by a variety of enzymes, with cyclin-dependent kinases (CDKs) being particularly important in phosphorylating proteins at serine and threonine sites. CDKs, which contain 20 unique components, serve an important role in regulating vital physiological functions such as cell cycle progression and gene transcription. Methodologically, an extensive literature search was performed using reputable databases such as PubMed, Google Scholar, Scopus, and Web of Science. Keywords encompassed "cyclin kinase," "cyclin dependent kinase inhibitors," "CDK inhibitors," "natural products," and "cancer therapy." The inclusion criteria, focused on relevance, publication date, and language, ensured a thorough representation of the most recent research in the field, encompassing articles published from January 2015 to September 2023. Categorization of CDKs into those regulating transcription and those orchestrating cell cycle phases provides a comprehensive understanding of their diverse functions. Ongoing clinical trials featuring CDK inhibitors, notably CDK7 and CDK4/6 inhibitors, illuminate their promising potential in various cancer treatments. This review undertakes a thorough investigation of CDK inhibitors derived from natural (marine, terrestrial, and peptide) sources. The aim of this study is to provide a comprehensive comprehension of the chemical classifications, origins, target CDKs, associated cancer types, and therapeutic applications.

The mechanism of UNC-51-like kinase 1 and the applications of small molecule modulators in cancer treatment

Autophagy is a process of self-renewal in cells, which not only provides the necessary nutrients for cells, but also clears necrotic organelles. Autophagy disorders are closely related to diseases such as cancer. UNC-51-like kinase 1 (ULK1) is a serine/threonine protein kinase that plays a crucial role in receiving input from energy and nutrient sensors, activating autophagy to maintain cellular homeostasis under stressful conditions. In recent years, targeting ULK1 has become a highly promising strategy for cancer treatment. This review introduces the regulatory mechanism of ULK1 in autophagy through the AMPK/mTOR/ULK1 pathway and reviews the research progress of ULK1 activators and inhibitors and their applications in cancer treatment. In addition, we analyze the binding modes between ULK1 and modulators through virtual molecular docking, which will provide a reliable basis and theoretical guidance for the design and development of new therapeutic drugs targeting ULK1.

Expression of cyclin-dependent kinase 9 is positively correlated with the autophagy level in colon cancer

BACKGROUND

Cyclin-dependent kinase 9 (CDK9) expression and autophagy in colorectal cancer (CRC) tissues has not been widely studied. CDK9, a key regulator of transcription, may influence the occurrence and progression of CRC. The expression of autophagy-related genes BECN1 and drug resistance factor ABCG2 may also play a role in CRC. Under normal physiological conditions, autophagy can inhibit tumorigenesis, but once a tumor forms, autophagy may promote tumor growth. Therefore, understanding the relationship between autophagy and cancer, particularly how autophagy promotes tumor growth after its formation, is a key motivation for this research.

AIM

To investigate the relationship between CDK9 expression and autophagy in CRC, assess differences in autophagy between left and right colon cancer, and analyze the associations of autophagy-related genes with clinical features and prognosis.

METHODS

We collected tumor tissues and paracarcinoma tissues from colon cancer patients with liver metastasis to observe the level of autophagy in tissues with high levels of CDK9 and low levels of CDK9. We also collected primary tissue from left and right colon cancer patients with liver metastasis to compare the autophagy levels and the expression of BECN1 and ABCG2 in the tumor and paracarcinoma tissues.

RESULTS

The incidence of autophagy and the expression of BECN1 and ABCG2 were different in left and right colon cancer, and autophagy might be involved in the occurrence of chemotherapy resistance. Further analysis of the relationship between the expression of autophagy-related genes CDK9, ABCG2, and BECN1 and the clinical features and prognosis of colorectal cancer showed that the high expression of CDK9 indicated a poor prognosis in colorectal cancer.

CONCLUSION

This study laid the foundation for further research on the combination of CDK9 inhibitors and autophagy inhibitors in the treatment of patients with CRC.

Binary Nanodrug-Delivery System Designed for Leukemia Therapy: Aptamer- and Transferrin-Codecorated Daunorubicin- and Luteolin-Coloaded Nanoparticles

Objective

This study aimed to develop a binary nanodrug-delivery system decorated with aptamers (APs) and transferrin (Tf) and loaded with daunorubicin (Drn) and luteolin (Lut) for the treatment of leukemia.

Methods

Oligonucleotide AP- and Tf-contaiing ligands were designed and synthesized separately. AP-decorated Drn-loaded nanoparticles (AP-Drn NPs) and Tf-Lut NPs were prepared by self-assembly. An AP- and Tf-codecorated Drn- and Lut-coloaded nanodrug-delivery system (AP/Tf-Drn/Lut NPs) was prepared by self-assembly of AP-Drn NPs and Tf-Lut NPs. In vitro and in vivo efficiency of the system was evaluated on leukemia cell line and cell-bearing mouse model in comparison with single ligand-decorated, single drug-loaded and free-drug formulations.

Results

AP/Tf-Drn/Lut NPs were spherical and nanosized (187.3±5.3 nm) and loaded with about 85% of drugs. In vitro cytotoxicity of AP/Tf-Drn/Lut NPs was remarkably higher than single ligand-decorated ones. Double drug-loaded AP/Tf-Drn/Lut NPs exhibited higher tumor-cell inhibition than single drug-loaded ones, which showed a synergic effect of the two drugs. AP/Tf-Drn/Lut NPs achieved the most efficient antileukemic activity and absence of toxicity in vivo.

Conclusion

The present study showed that AP/Tf-Drn/Lut NPs are a promising drug-delivery system for targeted treatment of leukemia, due to the synergic effect of the two drugs in this system. The limitations of this system include stability during large-scale production and application from bench to bedside.

Exploring native Scutellaria species provides insight into differential accumulation of flavones with medicinal properties

Scutellaria baicalensis is a well-studied medicinal plant belonging to the Lamiaceae family, prized for the unique 4′-deoxyflavones produced in its roots. In this study, three native species to the Americas, S. lateriflora, S. arenicola, and S. integrifolia were identified by DNA barcoding, and phylogenetic relationships were established with other economically important Lamiaceae members. Furthermore, flavone profiles of native species were explored. 4′-deoxyflavones including baicalein, baicalin, wogonin, wogonoside, chrysin and 4′-hydroxyflavones, scutellarein, scutellarin, and apigenin, were quantified from leaves, stems, and roots. Qualitative, and quantitative differences were identified in their flavone profiles along with characteristic tissue-specific accumulation. 4′-deoxyflavones accumulated in relatively high concentrations in root tissues compared to aerial tissues in all species except S. lateriflora. Baicalin, the most abundant 4′-deoxyflavone detected, was localized in the roots of S. baicalensis and leaves of S. lateriflora, indicating differential accumulation patterns between the species. S. arenicola and S. integrifolia are phylogenetically closely related with similar flavone profiles and distribution patterns. Additionally, the S. arenicola leaf flavone profile was dominated by two major unknown peaks, identified using LC–MS/MS to most likely be luteolin-7-O-glucuronide and 5,7,2′-trihydroxy-6-methoxyflavone 7-O-glucuronide. Collectively, results presented in this study suggest an evolutionary divergence of flavonoid metabolic pathway in the Scutellaria genus of Lamiaceae.

Novel CDK9 inhibitor oroxylin A promotes wild-type P53 stability and prevents hepatocellular carcinoma progression by disrupting both MDM2 and SIRT1 signaling

Hepatocellular carcinoma (HCC) is one of the most lethal tumours worldwide. However, the effects of first-line sorafenib treatment in advanced HCC fail to prolong patients' survival due to the highly heterogeneous characteristics of HCC etiology. Cyclin-dependent kinase 9 (CDK9) is an important target in the continuous development of cancer therapy. Here, we demonstrate that CDK9 is closely associated with the progression of HCC and can serve as an HCC therapeutic target by modulating the recovery of wild-type p53 (wt-p53) function. We prove that mouse double minute 2 homologue (MDM2) and Sirtuin 1 (SIRT1) are phosphorylated by CDK9 at Ser166 and Ser47, respectively. Inhibition of CDK9 not only reduces the MDM2-mediated ubiquitination and degradation of wt-p53 but also increases wt-p53 stability by suppressing deacetylase activity of SIRT1. Thus, inhibition of CDK9 promotes the wt-p53 stabilization and prevents HCC progression. However, excessive inhibition by high concentrations of specific CDK9 inhibitors counteracts the promotion of p53 stability and reduces their anti-HCC activity because of extreme general transcription repression. The effects of a novel CDK9 inhibitor named oroxylin A (OA) from Scutellaria baicalensis are explored, with the results indicating that OA shows moderate and controlled inhibition of CDK9 activity and expression, and stabilizes wt-p53 by inhibiting CDK9-regulated MDM2 and SIRT1 signaling. These outcomes indicate the high therapeutic potential of OA against HCC and its low toxicity in normal tissue. This study demonstrates a novel mechanism for the regulation of wt-p53 by CDK9 and indicates that OA is a potential candidate for HCC therapy.

A drug-biomarker interaction model to predict the key targets of Scutellaria barbata D. Don in adverse-risk acute myeloid leukaemia

A poor prognosis, relapse and resistance are burning issues during adverse-risk acute myeloid leukaemia (AML) treatment. As a natural medicine, Scutellaria barbata D. Don (SBD) has shown impressive antitumour activity in various cancers. Thus, SBD may become a potential drug in adverse-risk AML treatment. This study aimed to screen the key targets of SBD in adverse-risk AML using the drug-biomarker interaction model through bioinformatics and network pharmacology methods. First, the adverse-risk AML-related critical biomarkers and targets of SBD active ingredient were obtained from The Cancer Genome Atlas database and several pharmacophore matching databases. Next, the protein-protein interaction network was constructed, and topological analysis and pathway enrichment were used to screen key targets and main pathways of intervention of SBD in adverse-risk AML. Finally, molecular docking was implemented for key target verification. The results suggest that luteolin and quercetin are the main active components of SBD against adverse-risk AML, and affected drug resistance, apoptosis, immune regulation and angiogenesis through the core targets AKT1, MAPK1, IL6, EGFR, SRC, VEGFA and TP53. We hope the proposed drug-biomarker interaction model provides an effective strategy for the research and development of antitumour drugs.

The Therapeutic Potential of Wogonin Observed in Preclinical Studies

Wogonin is a flavonoid found in different plants such as roots of Scutellaria baicalensis Georgi distributed mainly in Asia and Europe. Dried root extracts of S. baicalensis with high content of wogonin, popularly known as "Huang-Qin" or Chinese or baical skullcap, have been used for long time in traditional Chinese medicine. Several health benefits are attributed to wogonin and derivatives showing anti-inflammatory, antiviral, anticancer, and antioxidant effects and more recently antineurodegenerative properties. Preclinical pharmacological activities of wogonin against diverse types of cancer such as breast, colorectal, and human gastric cancer will be presented in this review. In addition, studies on oxidative stress and bioavailability of wogonin will be discussed together with antineurodegenerative potential with special focus on Alzheimer's disease. Outcomes extracted from the last preclinical studies related to therapeutic applications of wogonin will be commented and updated in this review. The scientific evidence collected in this review aims to encourage transfer of the preclinical evidence of wogonin to new clinical studies.

Targeting CDK9 for Anti-Cancer Therapeutics

Cyclin Dependent Kinase 9 (CDK9) is one of the most important transcription regulatory members of the CDK family. In conjunction with its main cyclin partner-Cyclin T1, it forms the Positive Transcription Elongation Factor b (P-TEFb) whose primary function in eukaryotic cells is to mediate the positive transcription elongation of nascent mRNA strands, by phosphorylating the S2 residues of the YSPTSPS tandem repeats at the C-terminus domain (CTD) of RNA Polymerase II (RNAP II). To aid in this process, P-TEFb also simultaneously phosphorylates and inactivates a number of negative transcription regulators like 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) Sensitivity-Inducing Factor (DSIF) and Negative Elongation Factor (NELF). Significantly enhanced activity of CDK9 is observed in multiple cancer types, which is universally associated with significantly shortened Overall Survival (OS) of the patients. In these cancer types, CDK9 regulates a plethora of cellular functions including proliferation, survival, cell cycle regulation, DNA damage repair and metastasis. Due to the extremely critical role of CDK9 in cancer cells, inhibiting its functions has been the subject of intense research, resulting the development of multiple, increasingly specific small-molecule inhibitors, some of which are presently in clinical trials. The search for newer generation CDK9 inhibitors with higher specificity and lower potential toxicities and suitable combination therapies continues. In fact, the Phase I clinical trials of the latest, highly specific CDK9 inhibitor BAY1251152, against different solid tumors have shown good anti-tumor and on-target activities and pharmacokinetics, combined with manageable safety profile while the phase I and II clinical trials of another inhibitor AT-7519 have been undertaken or are undergoing. To enhance the effectiveness and target diversity and reduce potential drug-resistance, the future of CDK9 inhibition would likely involve combining CDK9 inhibitors with inhibitors like those against BRD4, SEC, MYC, MCL-1 and HSP90.

Targeting Bcl-2 Proteins in Acute Myeloid Leukemia

B cell lymphoma 2 (BCL-2) family proteins play an important role in intrinsic apoptosis. Overexpression of BCL-2 proteins in acute myeloid leukemia can circumvent resistance to apoptosis and chemotherapy. Considering this effect, the exploration of anti-apoptotic BCL-2 inhibitors is considered to have tremendous potential for the discovery of novel pharmacological modulators in cancer. This review outlines the impact of BCL-2 family proteins on intrinsic apoptosis and the development of acute myeloid leukemia (AML). Furthermore, we will also review the new combination therapy with venetoclax that overcomes resistance to venetoclax and discuss biomarkers of treatment response identified in early-phase clinical trials.

CDK9 as a Valuable Target in Cancer: From Natural Compounds Inhibitors to Current Treatment in Pediatric Soft Tissue Sarcomas

Cyclin-Dependent Kinases (CDKs) are well-known reliable targets for cancer treatment being often deregulated. Among them, since the transcription-associated CDK9 represents the sentry of cell transcriptional homeostasis, it can be a valuable target for managing cancers in which the transcriptional machinery is dysregulated by tumor-driver oncogenes. Here we give an overview of some natural compounds identified as CDK inhibitors with reported activity also against CDK9, that were taken as a model for the development of highly active synthetic anti-CDK9 agents. After, we summarize the data on CDK9 inhibition in a group of rare pediatric solid tumors such as rhabdomyosarcoma, Ewing’s sarcoma, synovial sarcoma and malignant rhabdoid tumors (soft tissue sarcomas), highlighting the more recent results in this field. Finally, we discuss the perspective and challenge of CDK9 modulation in cancer.

Natural analogues inhibiting selective cyclin-dependent kinase protein isoforms: a computational perspective

Cyclin-dependent kinases (CDKs) are known for their vital role in regulating cell cycle progression through protein-kinase interactions. CDKs also help in regulating transcription and development of the central nervous system. Inhibition of CDKs is a very fundamental approach for drug discovery in areas of different types of cancers, Alzheimer's, and HIV infections. The present research focuses on finding a novel, potent, and specific natural inhibitors of CDK isoforms (CDK2, CDK5, CDK7, CDK9). Molecular docking, molecular dynamics (MD) simulations, and Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) were carried out to get an in-depth understanding of protein-ligand interactions. Based on our molecular docking results, Ligands-3, 5, 14, and 16 were screened among 17 different Pyrrolone-fused benzosuberene compounds as potent and specific inhibitors without any cross-reactivity against different CDK isoforms. Analysis of MD simulations and MM-PBSA studies, revealed the binding energy profiles of all the selected complexes. Our selected ligands performed better than the standard inhibitor (Roscovitine). Ligands-3 and 14 show specificity for CDK7 and Ligands-5 and 16 were specific against CDK9. These ligands are expected to possess lower risk of side effects due to their natural origin. Moreover, the backbone structure of these ligands could also be exploited to develop specific inhibitors against other CDK isoforms.Communicated by Ramaswamy H. Sarma.

The Role of Platelets in the Tumor-Microenvironment and the Drug Resistance of Cancer Cells

Besides the critical functions in hemostasis, thrombosis and the wounding process, platelets have been increasingly identified as active players in various processes in tumorigenesis, including angiogenesis and metastasis. Once activated, platelets can release bioactive contents such as lipids, microRNAs, and growth factors into the bloodstream, subsequently enhancing the platelet⁻cancer interaction and stimulating cancer metastasis and angiogenesis. The mechanisms of treatment failure of chemotherapeutic drugs have been investigated to be associated with platelets. Therefore, understanding how platelets contribute to the tumor microenvironment may potentially identify strategies to suppress cancer angiogenesis, metastasis, and drug resistance. Herein, we present a review of recent investigations on the role of platelets in the tumor-microenvironment including angiogenesis, and metastasis, as well as targeting platelets for cancer treatment, especially in drug resistance.

Antifungal activity and mechanism of action of Ou-gon (Scutellaria root extract) components against pathogenic fungi

Ou-gon, an extract from Scutellaria baicalensis Georgi root, has been shown to exhibit pronounced antifungal activity. The present study aimed to identify antifungal components of Ou-gon and to determine their mechanism of action against pathogenic fungi. Antifungal activity was assessed by the microbroth dilution method using four common human pathogenic fungi, Trichophyton rubrum, Trichophyton mentagrophytes, Aspergillus fumigatus, and Candida albicans. Components of crude Ou-gon extract were separated by reversed-phase high-performance liquid chromatography. Active antifungal components were identified by liquid chromatography-electrospray ionization tandem mass spectrometry. Terminal deoxynucleotidyl transferase dUTP nick end-labelling assay, SYTOX^® green uptake assay, determination of intracellular reactive oxygen species and mitochondrial membrane potential as well as microscopy (confocal laser microscopy, scanning and transmission electron microscopy) were used to probe the mode of action. Two components with potent antifungal activity, baicalein and wogonin, were identified in Ou-gon. Baicalein showed potent antifungal activity against the four fungi tested. Wogonin displayed antifungal activity against all four fungi except C. albicans. The components are considered to induce apoptosis-like programmed cell death via hyperproduction of reactive oxygen species. This study enhances our understanding of the antifungal activity of Kampo medicine, and may contribute to the development of new and safe antifungal therapeutics.

Repression of Mcl-1 expression by the CDC7/CDK9 inhibitor PHA-767491 overcomes bone marrow stroma-mediated drug resistance in AML

Acute myeloid leukaemia (AML) is an aggressive cancer with 50-75% of patients relapsing even after successful chemotherapy. The role of the bone marrow microenvironment (BMM) in protecting AML cells from chemotherapeutics and causing consequent relapse is increasingly recognised. However the role that the anti-apoptotic Bcl-2 proteins play as effectors of BMM-mediated drug resistance are less understood. Here we show that bone marrow mesenchymal stromal cells (BMSC) provide resistance to AML cells against BH₃-mimetics, cytarabine and daunorubicin, but this is not mediated by Bcl-2 and/or Bcl-X_L as previously thought. Instead, BMSCs induced Mcl-1 expression over Bcl-2 and/or Bcl-X_L in AML cells and inhibition of Mcl-1 with a small-molecule inhibitor, A1210477, or repressing its expression with the CDC7/CDK9 dual-inhibitor, PHA-767491 restored sensitivity to BH₃-mimetics. Furthermore, combined inhibition of Bcl-2/Bcl-X_L and Mcl-1 could revert BMSC-mediated resistance against cytarabine + daunorubicin. Importantly, the CD34⁺/CD38^- leukemic stem cell-encompassing population was equally sensitive to the combination of PHA-767491 and ABT-737. These results indicate that Bcl-2/Bcl-X_L and Mcl-1 act in a redundant fashion as effectors of BMM-mediated AML drug resistance and highlight the potential of Mcl-1-repression to revert BMM-mediated drug resistance in the leukemic stem cell population, thus, prevent disease relapse and ultimately improve patient survival.

KPNB1 inhibition disrupts proteostasis and triggers unfolded protein response-mediated apoptosis in glioblastoma cells

The nuclear import receptor karyopherin β1 (KPNB1) is involved in the nuclear import of most proteins and in the regulation of multiple mitotic events. Upregulation of KPNB1 has been observed in cancers including glioblastoma. Depletion of KPNB1 induces mitotic arrest and apoptosis in cancer cells, but the underlying mechanism is not clearly elucidated. Here, we found that downregulation and functional inhibition of KPNB1 in glioblastoma cells induced growth arrest and apoptosis without apparent mitotic arrest. KPNB1 inhibition upregulated Puma and Noxa and freed Mcl-1-sequestered Bax and Bak, leading to mitochondrial outer membrane permeabilization (MOMP) and apoptosis. Moreover, combination of Bcl-xL inhibitors and KPNB1 inhibition enhanced apoptosis in glioblastoma cells. KPNB1 inhibition promoted cytosolic retention of its cargo and impaired cellular proteostasis, resulting in elevated polyubiquitination, formation of aggresome-like-induced structure (ALIS), and unfolded protein response (UPR). Ubiquitination elevation and UPR activation in KPNB1-deficient cells were reversed by KPNB1 overexpression or inhibitors of protein synthesis but aggravated by inhibitors of autophagy-lysosome or proteasome, indicating that rebalance of cytosolic/nuclear protein distribution and alleviation of protein overload favor proteostasis and cell survival. Chronic activation of eIF2α/ATF4 cascade of UPR was responsible for the upregulation of Puma and Noxa, apoptosis and ABT-263 sensitivity. Taken together, our findings demonstrate that KPNB1 is required for proteostasis maintenance and its inhibition induces apoptosis in glioblastoma cells through UPR-mediated deregulation of Bcl-2 family members.

Combined venetoclax and alvocidib in acute myeloid leukemia

More effective treatment options for elderly acute myeloid leukemia (AML) patients are needed as only 25-50% of patients respond to standard-of-care therapies, response duration is typically short, and disease progression is inevitable even with some novel therapies and ongoing clinical trials. Anti-apoptotic BCL-2 family inhibitors, such as venetoclax, are promising therapies for AML. Nonetheless, resistance is emerging. We demonstrate that venetoclax combined with cyclin-dependent kinase (CDK) inhibitor alvocidib is potently synergistic in venetoclax-sensitive and -resistant AML models in vitro, ex vivo and in vivo. Alvocidib decreased MCL-1, and/or increased pro-apoptotic proteins such as BIM or NOXA, often synergistically with venetoclax. Over-expression of BCL-XL diminished synergy, while knock-down of BIM almost entirely abrogated synergy, demonstrating that the synergistic interaction between alvocidib and venetoclax is primarily dependent on intrinsic apoptosis. CDK9 inhibition predominantly mediated venetoclax sensitization, while CDK4/6 inhibition with palbociclib did not potentiate venetoclax activity. Combined, venetoclax and alvocidib modulate the balance of BCL-2 family proteins through complementary, yet variable mechanisms favoring apoptosis, highlighting this combination as a promising therapy for AML or high-risk MDS with the capacity to overcome intrinsic apoptosis mechanisms of resistance. These results support clinical testing of combined venetoclax and alvocidib for the treatment of AML and advanced MDS.

Application of luteolin nanomicelles anti-glioma effect with improvement in vitro and in vivo

Glioblastoma multiforme (GBM) is one of the most common and malignant tumor. Luteolin, a polyphenolic compound, has been proposed to have anti-tumor activity against various cancers. However, the greatest obstacle in the administration of luteolin is its hydrophobicity as well as the low oral bioavailability. In this study, we formulated luteolin-loaded MPEG-PCL (Luteolin/MPEG-PCL) micelles aiming to improve its solubility in aqueous solution and investigate the anti-tumor effect on glioma in vitro and in vivo. The spherical Luteolin/MPEG-PCL micelles were completely dispersible in normal saline and could release luteolin in a sustained manner in vitro. We demonstrated that Luteolin/MPEG-PCL micelles had stronger cytotoxicity and induced a higher percentage of apoptosis in C6 and U87 cells than free luteolin in vitro. The immunohistochemical study revealed that Luteolin/MPEG-PCL micelles induced more glioma cell apoptosis than free luteolin and inhibited neovascularization in tumor tissues. The Pro-caspase9 and Bcl-2 down-regulation and cleaved-caspase9 and Bax up-regulation suggested that luteolin induced apoptosis via the mitochondrial pathway in vitro. What is more, we found the drug could cumulated much more in the nano-drug group than free drug group through imaging in vivo. In conclusion, the Luteolin/MPEG-PCL micelles have the potential clinical application in glioma chemotherapy.

BIRC6 mediates imatinib resistance independently of Mcl-1

Baculoviral IAP repeat containing 6 (BIRC6) is a member of the inhibitors of apoptosis proteins (IAPs), a family of functionally and structurally related proteins that inhibit apoptosis. BIRC6 has been implicated in drug resistance in several different human cancers, however mechanisms regulating BIRC6 have not been extensively explored. Our phosphoproteomic analysis of an imatinib-resistant chronic myelogenous leukemia (CML) cell line (MYL-R) identified increased amounts of a BIRC6 peptide phosphorylated at S480, S482, and S486 compared to imatinib-sensitive CML cells (MYL). Thus we investigated the role of BIRC6 in mediating imatinib resistance and compared it to the well-characterized anti-apoptotic protein, Mcl-1. Both BIRC6 and Mcl-1 were elevated in MYL-R compared to MYL cells. Lentiviral shRNA knockdown of BIRC6 in MYL-R cells increased imatinib-stimulated caspase activation and resulted in a ~20-25-fold increase in imatinib sensitivity, without affecting Mcl-1. Treating MYL-R cells with CDK9 inhibitors decreased BIRC6 mRNA, but not BIRC6 protein levels. By contrast, while CDK9 inhibitors reduced Mcl-1 mRNA and protein, they did not affect imatinib sensitivity. Since the Src family kinase Lyn is highly expressed and active in MYL-R cells, we tested the effects of Lyn inhibition on BIRC6 and Mcl-1. RNAi-mediated knockdown or inhibition of Lyn (dasatinib/ponatinib) reduced BIRC6 protein stability and increased caspase activation. Inhibition of Lyn also increased formation of an N-terminal BIRC6 fragment in parallel with reduced amount of the BIRC6 phosphopeptide, suggesting that Lyn may regulate BIRC6 phosphorylation and stability. In summary, our data show that BIRC6 stability is dependent on Lyn, and that BIRC6 mediates imatinib sensitivity independently of Mcl-1 or CDK9. Hence, BIRC6 may be a novel target for the treatment of drug-resistant CML where Mcl-1 or CDK9 inhibitors have failed.

Wogonin induces Beclin-1/PI3K and reactive oxygen species-mediated autophagy in human pancreatic cancer cells

Wogonin is considered to be an inhibitor of myeloid cell leukemia 1 and B-cell lymphoma 2, and a potential antitumor drug due to its ability to induce apoptosis in certain cancer cells; however, few previous studies have reported on wogonin-induced autophagy. The aim of the present study was to investigate the influence of wogonin on autophagy in human pancreatic cancer cells (HPCCs), elucidate its mechanism, and identify strategies to increase its effectiveness as an anti-cancer treatment. HPCCs were treated with wogonin and autophagy was detected in the cells. The mechanism of wogonin-related autophagy was investigated, and the antioxidant N-acetyl-L-cysteine (NAC) was used to assess the role of reactive oxygen species (ROS) in wogonin-related autophagy. The results demonstrated that wogonin may induce autophagy by activating the Beclin-1/phosphatidylinositol-3-kinase and ROS pathways in HPCCs, and may enhance ROS generation, followed by the activation of the AKT/ULK1/4E-BP1/CYLD pathway and inhibition of the mammalian target of rapamycin signaling pathway. The incubation of HPCCs with wogonin and the antioxidant NAC, revealed that the effects of wogonin-enhanced ROS generation on autophagy-related molecules were inhibited, contributing to the inhibition of autophagy and increasing the cell death ratio through apoptosis activation in HPCCs. These studies suggest that autophagy activation, via the ROS pathway, by the antitumor drug wogonin in HPCCs may partially reduce the antitumor effects of the drug, and that the antioxidant NAC may enhance the antitumor effectiveness of wogonin via the inhibition of ROS-enhanced autophagy and the subsequent promotion of apoptosis. Therefore, the present research suggests that wogonin combined with NAC may be a novel combination therapy for clinical pancreatic cancer therapy trials.

Antitumor action of CDK inhibitor LS-007 as a single agent and in combination with ABT-199 against human acute leukemia cells

AIM

LS-007 is a CDK inhibitor, which exhibits potent antitumor activity against chronic lymphocytic leukemia and ovarian cancer cells. In this study, we further evaluated the antitumor activity of LS-007 alone and in combination with a Bcl-2 inhibitor ABT-199 in acute leukemia (AL) cells.

METHODS

Cell viability was detected using resazurin assay, and cell apoptosis was examined using Annexin V/PI double staining and flow cytometry. The inhibition of LS-007 on kinases was evaluated with the mobility shift assay or ELISA. The expression of relevant signaling molecules was assessed using Western blotting and RT-PCR. Primary lymphocytes from patients with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) were separated using Ficoll-Paque PLUS.

RESULTS

LS-007 inhibited the proliferation of 6 AL cell lines with IC₅₀ values of 100-200 nmol/L, and decreased the survival of ALL and AML patient-derived lymphocytes with mean LD₅₀ value of 67 and 102 nmol/L, respectively. In kinase assays in vitro, LS-007 was more selective for the CDK family, inhibiting CDK2, CDK9, CDK1 and CDK4 at low nanomolar concentrations. In HL-60 and CCRF-CEM cells, LS-007 (0.1-0.4 μmol/L) dose-dependently induced cell apoptosis predominantly through CDK9 inhibition-related dephosphorylation at the ser2 residue of RNA pol II and the corresponding depletion of anti-apoptotic proteins, especially Mcl-1 and XIAP. LS-007 (0.2 and 0.4 μmol/L) also induced cell apoptosis in the patient-derived lymphocytes. In HL-60, CCRF-CEM and Molt-4 cells, combined application of LS-007 with ABT-199 (1 or 2 μmol/L) markedly increased cell apoptosis with a maximal decrease in the XIAP levels as compared with either drug used alone.

CONCLUSION

CDK inhibitor LS-007 potently inhibits the established human AL cell lines and primary AL blasts, and it also shows remarkable synergy with Bcl-2 inhibitor ABT-199.

Advances of wogonin, an extract from Scutellaria baicalensis, for the treatment of multiple tumors

As the major bioactive compound of Scutellaria baicalensis that has been approved to be effective as an anti-inflammatory and antiviral inhibitor in cardiovascular diseases, wogonin (WG) showed potent and promising antitumor effects both in vitro and in vivo. It has been proved that WG has the ability to inhibit the growth of tumor cells, induce apoptosis, and suppress angiogenesis. The molecular mechanisms involve reactive oxygen species, Ca²⁺, NF-κB, tumor necrosis factor-related apoptosis-inducing ligand, and tumor necrosis factor-alpha. Furthermore, the synergistic effect of WG with 5-fluorouracil, etoposide, and adriamycin to enhance chemotherapy and reverse drug resistance has also been confirmed. In this review, we summarize the advances in recent years on the antitumor effect of WG on multiple tumors; in addition, we also present information regarding the synergistic and chemosensitizing effects of WG with other drugs to illustrate its potential use in the clinic.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

Cyclin-Dependent Kinase Inhibitors as Anticancer Therapeutics

Cyclin-dependent kinases (CDKs) have been considered promising drug targets for a number of years, but most CDK inhibitors have failed rigorous clinical testing. Recent studies demonstrating clear anticancer efficacy and reduced toxicity of CDK4/6 inhibitors such as palbociclib and multi-CDK inhibitors such as dinaciclib have rejuvenated the field. Favorable results with palbociclib and its recent U.S. Food and Drug Administration approval demonstrate that CDK inhibitors with narrow selectivity profiles can have clinical utility for therapy based on individual tumor genetics. A brief overview of results obtained with ATP-competitive inhibitors such as palbociclib and dinaciclib is presented, followed by a compilation of new avenues that have been pursued toward the development of novel, non-ATP-competitive CDK inhibitors. These creative ways to develop CDK inhibitors are presented along with crystal structures of these agents complexed with CDK2 to highlight differences in their binding sites and mechanisms of action. The recent successes of CDK inhibitors in the clinic, combined with the potential for structure-based routes to the development of non-ATP-competitive CDK inhibitors, and evidence that CDK inhibitors may have use in suppressing chromosomal instability and in synthetic lethal drug combinations inspire optimism that CDK inhibitors will become important weapons in the fight against cancer.

Apigenin induces dermal collagen synthesis via smad2/3 signaling pathway

Decrease in fibroblast-produced collagen has been proven to be the pivotal cause of skin aging, but there is no satisfactory drug which directly increases dermal thickness and collage density. Here we found that a flavonoid natural product, apigenin, could significantly increase collagen synthesis. NIH/3T3 and primary human dermal fibroblasts (HDFs) were incubated with various concentrations of apigenin, with dimethyl sulfoxide (DMSO) serving as the negative control. Real-time reverse-transcription polymerase chain reaction (PCR), Western Blot, and Toluidine blue staining demonstrated that apigenin stimulated type-I and type-III collagen synthesis of fibroblasts on the mRNA and protein levels. Meanwhile, apigenin did not induce expression of alpha smooth muscle actin (α-SMA) in vitro and in vivo, a fibrotic marker in living tissues. Then the production of collagen was confirmed by Masson’s trichrome stain, Picrosirius red stain and immunohistochemistry in mouse models. We also clarified that this compound induced collagen synthesis by activating smad2/3 signaling pathway. Taken together, without obvious influence on fibroblasts’ apoptosis and viability, apigenin could promote the type-I and type-III collagen synthesis of dermal fibroblasts in vitro and in vivo, thus suggesting that apigenin may serve as a potential agent for esthetic and reconstructive skin rejuvenation.