In vitro antitumor properties of a novel cyclin-dependent kinase inhibitor, P276-00

Clinical development and informatics analysis of natural and semi-synthetic flavonoid drugs: A critical review

BACKGROUND

Flavonoids are one of the most important metabolites with vast structural diversity and a plethora of potential pharmacological applications, which have drawn considerable attention in the laboratory. Nevertheless, it remains uncertain how many candidates were progressed to clinical application.

AIM OF REVIEW

We carried out a critical review of natural and semi-synthetic flavonoid drugs and candidates undergoing different clinical phases worldwide by applying an adequate search method and conducted a brief cheminformatic and bioinformatic analysis. It was expected that the obtained results might narrow the screening scope and reduce the cost of drug research and development.

KEY SCIENTIFIC CONCEPTS OF REVIEW

To our knowledge, this is the most systematic summarization of flavonoid-based drugs and clinical candidates to date. It was found that a total of 19 flavonoid-based drugs have been approved for the market, and of these, natural flavonoids accounted for 52.6%. Besides, a total of 36 flavonoid-based clinical candidates are undergoing or suspended in different phases, and of these, natural flavonoids account for 44.4%. Thus, natural flavonoids remain the best option for finding novel agents/active templates, and when investigated in conjunction with synthetic chemicals and biologicals, they offer the potential to discover novel structures that can lead to effective agents against a variety of human diseases. Additionally, flavonoid-based marketed drugs have been successful in cardiovascular treatment, and the related drugs account for more than 30% of marketed drugs. However, the use of flavonoids as antineoplastic and immunomodulating agents is not likely for approximately 50% of the candidates suspended in the clinical stage. Interestingly, the marketed drugs covered a broader range of chemical spaces based on size, polarity, and three-dimensional structure compared to the clinical candidates. In addition, flavonoid glycosides with poor oral bioavailability account for 36.8% of the marketed drugs, and thus, they could be thoroughly investigated.

Advances in synthesis and biological evaluation of CDK2 inhibitors for cancer therapy

One of the leading causes of mortality in the world is cancer. This disease occurs when responsible genes that regulate the cell cycle become inactive due to internal or external factors. Specifically, the G1/S and S/G2 transitions in the cell cycle are controlled by a protein called cyclin-dependent kinase 2 (CDK2). CDKs, which play a crucial role in managing the cell cycle, have been a wide area of research in cancer treatment. Over the past 11 years, significant research has been made in identifying potent, targeted, and efficient inhibitors of CDK2. In this summary, we have summarized recent developments in the synthesis and biological evaluation of CDK2 inhibitors.

The Pharmacological Implications of Flavopiridol: An Updated Overview

Flavopiridol is a flavone synthesized from the natural product rohitukine, which is derived from an Indian medicinal plant, namely Dysoxylum binectariferum Hiern. A deeper understanding of the biological mechanisms by which such molecules act may allow scientists to develop effective therapeutic strategies against a variety of life-threatening diseases, such as cancer, viruses, fungal infections, parasites, and neurodegenerative diseases. Mechanistic insight of flavopiridol reveals its potential for kinase inhibitory activity of CDKs (cyclin-dependent kinases) and other kinases, leading to the inhibition of various processes, including cell cycle progression, apoptosis, tumor proliferation, angiogenesis, tumor metastasis, and the inflammation process. The synthetic derivatives of flavopiridol have overcome a few demerits of its parent compound. Moreover, these derivatives have much improved CDK-inhibitory activity and therapeutic abilities for treating severe human diseases. It appears that flavopiridol has potential as a candidate for the formulation of an integrated strategy to combat and alleviate human diseases. This review article aims to unravel the potential therapeutic effectiveness of flavopiridol and its possible mechanism of action.

Molecular Pharmacology of Multitarget Cyclin-Dependent Kinase Inhibitors in Human Colorectal Carcinoma Cells

BACKGROUND

Colorectal cancer (CRC) is a leading cause of cancer death. Certain signaling pathways are implicated in colorectal carcinogenesis. Cyclin-dependent kinases (CDKs) are commonly hyperactivated in CRC and hence multitarget CDK inhibitors serve as promising therapeutic drugs against CRC.

OBJECTIVE

Off-target effects of multitarget CDK inhibitors with differential CDK inhibitory spectrum viz. P276-00 (also known as riviciclib), roscovitine and UCN-01 on CRC cell lines of varied genetic background were delineated.

METHOD

Protein expression was analyzed for key signaling proteins by western blotting. β-catenin localization was assessed using immunofluorescence. HIF-1 transcriptional activity and target gene expression were studied by reporter gene assay and RT-PCR respectively. Anti-migratory and anti-angiogenic potential was evaluated by wound healing assay and endothelial tube formation assay.

RESULTS

CDK inhibitors modulated various signaling pathways in CRC and for certain proteins showed a highly cell line-dependent response. Riviciclib and roscovitine inhibited HIF-1 transcriptional activity and HIF-1α accumulation in hypoxic HCT116 cells. Both of these drugs also abrogated migration of HCT116 and in vitro angiogenesis in HUVECs.

CONCLUSION

Anticancer activity of multitarget CDK inhibitors can be certainly attributed to their off-target effects and should be analyzed while assessing their therapeutic utility against CRC.

Addressing Transcriptional Dysregulation in Cancer through CDK9 Inhibition

Undermining transcriptional addiction, the dependence of cancers on selected transcriptional programs, is critically important for addressing cancers with high unmet clinical need. Cyclin-dependent kinase 9 (CDK9) has long been considered an actionable therapeutic target for modulating transcription in many diseases. This appeal is due to its role in coordinating the biochemical events that regulate RNA polymerase II (RNA Pol II) pause-release state, one that offers a way for attenuating transcriptional dysregulation driven by amplified or overexpressed transcription factors implicated in cancer. However, targeting CDK9 in the clinic has historically proven elusive, a challenge that stems from the often highly intolerable cytotoxicity attributed to its essentiality across many cell lineages and the polypharmacology of the first generation of pan-CDK inhibitors to reach the clinic. A new wave of highly selective molecules progressing through the early stages of clinical evaluation offers renewed hope.

Transcriptome analysis and differential expression in Arabidopsis thaliana in response to rohitukine (a chromone alkaloid) treatment

Rohitukine is a chromone alkaloid and precursor of potent anticancer drugs flavopiridol, P-276-00, and 2,6-dichloro-styryl derivative (11d) (IIIM-290). The metabolite is reported to possess anticancer, anti-inflammatory, antiadipogenic, immunomodulatory, gastroprotective, anti-implantation, antidyslipidemic, anti-arthritic, and anti-fertility properties. However, the physiological role of rohitukine in plant system is yet to be explored. Here, we studied the effect of rohitukine isolated from Dysoxylum gotadhora on Arabidopsis thaliana. The A. thaliana plants grown on a medium fortified with different rohitukine concentrations showed a significant effect on the growth and development. The root growth of A. thaliana seedlings showed considerable inhibition when grown on medium containing 1.0 mM of rohitukine. Transcriptomic analysis indicated the expression of 895 and 932 genes in control and treated samples respectively at a cut-off of FPKM ≥ 1 and P-value < 0.05. Gene ontology (GO) analysis revealed the upregulation of genes related to photosynthesis, membrane transport, antioxidation, xenobiotic degradation, and some transcription factors (TFs) in response to rohitukine. Conversely, rohitukine downregulated several genes including RNA helicases and those involved in nitrogen compound metabolism. The RNA-seq result was also validated by real-time qRT-PCR analysis. In light of these results, we discuss (i) likely ecological importance of rohitukine in parent plant as well as (ii) comparison between responses to rohitukine treatment in plants and mammals.

CDK inhibitors from past to present: A new wave of cancer therapy

Deregulation of the cell cycle machinery, which has been linked to dysregulation of cyclin-dependent kinases (CDKs), is a defining characteristic of cancer, eventually promoting abnormal proliferation that feeds tumorigenesis and disease development. In this regard, several CDK inhibitors (CDKIs) have been developed during the last few decades (1st, 2nd, and 3rd generation CDKIs) to inhibit cancer cell proliferation. 1st and 2nd generation CDKIs have not received much clinical attention for the treatment of cancer patients because of their limited specificity and high toxicity. However, the recent development of combination strategies allowed us to reduce the toxicity and side effects of these CDKIs, paving the way for their potential application in clinical settings. The 3rd generation CDKIs have yielded the most promising results at the preclinical and clinical levels, propelling them into the advanced stages of clinical trials against multiple malignancies, especially breast cancer, and revolutionizing traditional treatment strategies. In this review, we discuss the most-investigated candidates from the 1st, 2nd, and 3rd generations of CDKIs, their basic mechanisms of action, the reasons for their failure in the past, and their current clinical development for the treatment of different malignancies. Additionally, we briefly highlighted the most recent clinical trial results and advances in the development of 3rd generation FDA-approved selective CDK4/6 inhibitors that combat the most prevalent cancer. Overall, this review will provide a thorough knowledge of CDKIs from the past to the present, allowing researchers to rethink and develop innovative cancer therapeutic regimens.

From Structure Modification to Drug Launch: A Systematic Review of the Ongoing Development of Cyclin-Dependent Kinase Inhibitors for Multiple Cancer Therapy

Herein, we discuss more than 50 cyclin-dependent kinase (CDK) inhibitors that have been approved or have undergone clinical trials and their therapeutic application in multiple cancers. This review discusses the design strategies, structure-activity relationships, and efficacy performances of these selective or nonselective CDK inhibitors. The theoretical basis of early broad-spectrum CDK inhibitors is similar to the scope of chemotherapy, but because their toxicity is greater than the benefit, there is no clinical therapeutic window. The notion that selective CDK inhibitors have a safer therapeutic potential than pan-CDK inhibitors has been widely recognized during the research process. Four CDK4/6 inhibitors have been approved for the treatment of breast cancer or for prophylactic administration during chemotherapy to protect bone marrow and immune system function. Furthermore, the emerging strategies in the field of CDK inhibitors are summarized briefly, and CDKs continue to be widely pursued as emerging anticancer drug targets for drug discovery.

CDK9 inhibitors in multiple myeloma: a review of progress and perspectives

Currently, multiple myeloma is not yet considered a curable disease. Despite the recent advances in therapy, the average patient lifespan is still unsatisfactory. Recently, CDK9 inhibitors emerged as a suitable agent to overcome resistance and prolong survival in patients with poor diagnoses. Downregulation of c-MYC, XIAP, Mcl-1 and restoration of p53 tumor-suppressive functions seems to play a key role in achieving clinical response. The applicability of the first generation of CDK9 inhibitors was limited due to relatively high toxicity, but the introduction of novel, highly selective drugs, seems to reduce the effects of off-target inhibition. CDK9 inhibitors were able to induce dose-dependent cytotoxicity in Doxorubicin-resistant, Lenalidomide-resistant and Bortezomib-resistant cell lines. They seem to be effective in cell lines with unfavorable prognostic factors, such as p53 deletion, t(4; 14) and t(14; 16). In preclinical trials, the application of CDK9 inhibitors led to tumor cells apoptosis, tumor growth inhibition and tumor mass reduction. Synergistic effects between CDK9 inhibitors and either Venetoclax, Bortezomib, Lenalidomide or Erlotinib have been proven and are awaiting verification in clinical trials. Although conclusions should be drawn with due care, obtained reports suggest that including CDK9 inhibitors into the current drug regimen may turn out to be beneficial, especially in poor prognosis patients.

Promising Anticancer Activity of Multitarget Cyclin Dependent Kinase Inhibitors against Human Colorectal Carcinoma Cells

Background:

Colorectal cancer (CRC) is the third leading cause of cancer death worldwide, and its incidence is steadily rising in developing nations. Cell cycle aberrations due to deregulation of cyclin dependent kinases (CDKs) and cyclins are common events during colorectal carcinogenesis. Yet, efficacy of multitarget CDK inhibitors as therapeutic agents has not been much explored against CRC.

Objective:

The anticancer potential of multitarget CDK inhibitor riviciclib (also known as P276-00), was investigated against CRC cell lines of varied genetic background.

Method:

Cytotoxicity of riviciclib - potent CDK1, CDK4 and CDK9-specific inhibitor was evaluated in vitro. Further, its effect on clonogenic potential, cell cycle, apoptosis and transcription was tested using colony forming assay, flow cytometry and western blot analysis respectively. Also, efficacy of riviciclib in combination with standard chemotherapeutic agents was assessed. Dependency of CRC cells on specific CDKs for their survival was confirmed using siRNA studies.

Results:

Riviciclib exerted significant cytotoxicity against CRC cells and inhibited their colony forming potential. It induced apoptosis along with inhibition of cell cycle CDKs and cyclins as well as transcriptional CDKs and cyclins. Moreover, dual combination of riviciclib with standard chemotherapeutic drugs exhibited synergism in CRC cells. siRNA studies indicated that CRC cells are dependent on specific CDKs for their survival which are targets of riviciclib.

Conclusion:

This study provides evidence that multitarget CDK inhibitors can serve as promising therapeutic agents against CRC alone or in combination.

CDK9 Inhibitors in Cancer Research

Cyclin dependent kinase 9 (CDK9) played an essential role in regulating transcriptional elongation. Aberrations in CDK9 activity have been observed in various cancers, which made CDK9 was an attractive therapeutic...

Chiral Flavonoids as Antitumor Agents

Flavonoids are a group of natural products with a great structural diversity, widely distributed in plant kingdom. They play an important role in plant growth, development and defense against aggressors. Flavonoids show a huge variety of biological activities such as antioxidant, anti-inflammatory, anti-mutagenic, antimicrobial and antitumor, being able to modulate a large diversity of cellular enzymatic activities. Among natural flavonoids, some classes comprise chiral molecules including flavanones, flavan-3-ols, isoflavanones, and rotenoids, which have one or more stereogenic centers. Interestingly, in some cases, individual compounds of enantiomeric pairs have shown different antitumor activity. In nature, these compounds are mainly biosynthesized as pure enantiomers. Nevertheless, they are often isolated as racemates, being necessary to carry out their chiral separation to perform enantioselectivity studies. Synthetic chiral flavonoids with promising antitumor activity have also been obtained using diverse synthetic approaches. In fact, several new chiral bioactive flavonoids have been synthesized by enantioselective synthesis. Particularly, flavopiridol was the first cyclin-dependent kinase (CDK) inhibitor which entered clinical trials. The chiral pool approaches using amino acid as chiral building blocks have also been reported to achieve small libraries of chrysin derivatives with more potent in vitro growth inhibitory effect than chrysin, reinforcing the importance of the introduction of chiral moieties to improve antitumor activity. In this work, a literature review of natural and synthetic chiral flavonoids with antitumor activity is reported for the first time.

Integrated Genomic Profiling and Drug Screening of Patient-Derived Cultures Identifies Individualized Copy Number-Dependent Susceptibilities Involving PI3K Pathway and 17q Genes in Neuroblastoma

Neuroblastoma is the commonest extracranial pediatric malignancy. With few recurrent single nucleotide variations (SNVs), mutation-based precision oncology approaches have limited utility, but its frequent and heterogenous copy number variations (CNVs) could represent genomic dependencies that may be exploited for personalized therapy. Patient-derived cell culture (PDC) models can facilitate rapid testing of multiple agents to determine such individualized drug-responses. Thus, to study the relationship between individual genomic aberrations and therapeutic susceptibilities, we integrated comprehensive genomic profiling of neuroblastoma tumors with drug screening of corresponding PDCs against 418 targeted inhibitors. We quantified the strength of association between copy number and cytotoxicity, and validated significantly correlated gene-drug pairs in public data and using machine learning models. Somatic mutations were infrequent (3.1 per case), but copy number losses in 1p (31%) and 11q (38%), and gains in 17q (69%) were prevalent. Critically, in-vitro cytotoxicity significantly correlated only with CNVs, but not SNVs. Among 1278 significantly correlated gene-drug pairs, copy number of GNA13 and DNA damage response genes CBL, DNMT3A, and PPM1D were most significantly correlated with cytotoxicity; the drugs most commonly associated with these genes were PI3K/mTOR inhibitor PIK-75, and CDK inhibitors P276-00, SNS-032, AT7519, flavopiridol and dinaciclib. Predictive Markov random field models constructed from CNVs alone recapitulated the true z-score-weighted associations, with the strongest gene-drug functional interactions in subnetworks involving PI3K and JAK-STAT pathways. Together, our data defined individualized dose-dependent relationships between copy number gains of PI3K and STAT family genes particularly on 17q and susceptibility to PI3K and cell cycle agents in neuroblastoma. Integration of genomic profiling and drug screening of patient-derived models of neuroblastoma can quantitatively define copy number-dependent sensitivities to targeted inhibitors, which can guide personalized therapy for such mutationally quiet cancers.

Cyclin-Dependent Kinase Inhibitors in Hematological Malignancies-Current Understanding, (Pre-)Clinical Application and Promising Approaches

Simple Summary

Cyclin-dependent kinases are involved in the regulation of cancer-initiating processes like cell cycle progression, transcription, and DNA repair. In hematological neoplasms, these enzymes are often overexpressed, resulting in increased cell proliferation and cancer progression. Early (pre-)clinical data using cyclin-dependent kinase inhibitors are promising but identifying the right drug for each subgroup and patient is challenging. Certain chromosomal abnormalities and signaling molecule activities are considered as potential biomarkers. We therefore summarized relevant studies investigating cyclin-dependent kinase inhibitors in hematological malignancies and further discuss molecular mechanisms of resistance and other open questions.

Abstract

Genetically altered stem or progenitor cells feature gross chromosomal abnormalities, inducing modified ability of self-renewal and abnormal hematopoiesis. Cyclin-dependent kinases (CDK) regulate cell cycle progression, transcription, DNA repair and are aberrantly expressed in hematopoietic malignancies. Incorporation of CDK inhibitors (CDKIs) into the existing therapeutic regimens therefore constitutes a promising strategy. However, the complex molecular heterogeneity and different clinical presentation is challenging for selecting the right target and defining the ideal combination to mediate long-term disease control. Preclinical and early clinical data suggest that specific CDKIs have activity in selected patients, dependent on the existing rearrangements and mutations, potentially acting as biomarkers. Indeed, CDK6, expressed in hematopoietic cells, is a direct target of MLL fusion proteins often observed in acute leukemia and thus contributes to leukemogenesis. The high frequency of aberrancies in the retinoblastoma pathway additionally warrants application of CDKIs in hematopoietic neoplasms. In this review, we describe the preclinical and clinical advances recently made in the use of CDKIs. These include the FDA-approved CDK4/6 inhibitors, traditional and novel pan-CDKIs, as well as dual kinase inhibitors. We additionally provide an overview on molecular mechanisms of response vs. resistance and discuss open questions.

Small Molecule CDK Inhibitors for the Therapeutic Management of Cancer

Cyclin-dependent kinases (CDKs) are a group of multifunctional enzymes consisting of catalytic and regulatory subunits. The regulatory subunit, cyclin, remains dissociated under normal circumstances, and complexation of cyclin with the catalytic subunit of CDK leads to its activation for phosphorylation of protein substrates. The primary role of CDKs is in the regulation of the cell cycle. Retinoblastoma protein (Rb) is one of the widely investigated tumor suppressor protein substrates of CDK, which prevents cells from entering into cell-cycle under normal conditions. Phosphorylation of Rb by CDKs causes its inactivation and ultimately allows cells to enter a new cell cycle. Many cancers are associated with hyperactivation of CDKs as a result of mutation of the CDK genes or CDK inhibitor genes. Therefore, CDK modulators are of great interest to explore as novel therapeutic agents against cancer and led to the discovery of several CDK inhibitors to clinics. This review focuses on the current progress and development of anti-cancer CDK inhibitors from preclinical to clinical and synthetic to natural small molecules.

Eco-friendly sequential one-pot synthesis, molecular docking, and anticancer evaluation of arylidene-hydrazinyl-thiazole derivatives as CDK2 inhibitors

One current approach in the treatment of cancer is the inhibition of cyclin dependent kinase (CDK) enzymes with small molecules. CDK are a class of enzymes, which catalyze the transfer of the terminal phosphate of a molecule of ATP to a protein that acts as a substrate. Among CDK enzymes, CDK2 has been implicated in a variety of cancers, supporting its potential as a novel target for cancer therapy across many tumor types. Here the discovery and development of arylidene-hydrazinyl-thiazole as a potentially CDK2 inhibitors is described, including details of the design and successful synthesis of the series analogs (27a-r) using one-pot approach under eco-friendly ultrasound and microwave conditions. Most of the newly synthesized compounds showed good growth inhibition when assayed for their in-vitro anti-proliferative activity against three cancer cell lines (HepG2, MCF-7 and HCT-116) compared to the reference drug roscovitine, with little toxicity on the normal fibroblast cell lines (WI-38). Furthermore, the compounds exhibiting the highest anti-proliferative activities were tested against a panel of kinase enzymes. These derivatives displayed an outstanding CDK2 inhibitory potential with varying degree of inhibition in the range of IC₅₀ 0.35-1.49 μM when compared with the standard inhibitor roscovitine having an IC₅₀ value 0.71 μM. The most promising CDK2 inhibitor (27f) was selected for further studies to determine its effect on the cell cycle progression and apoptosis in HepG2 cell line. The results indicated that this compound implied inhibition in the G2/M phase of the cell cycle, and it is a good apoptotic agent. Finally, Molecular docking study was performed to identify the structural elements which involved in the inhibitory activity with the prospective target, CDK2, and to rationalize the structure-activity relationship (SAR).

Selective inhibition of CDK4/6: A safe and effective strategy for developing anticancer drugs

The sustained cell proliferation resulting from dysregulation of the cell cycle and activation of cyclin-dependent kinases (CDKs) is a hallmark of cancer. The inhibition of CDKs is a highly promising and attractive strategy for the development of anticancer drugs. In particular, third-generation CDK inhibitors can selectively inhibit CDK4/6 and regulate the cell cycle by suppressing the G1 to S phase transition, exhibiting a perfect balance between anticancer efficacy and general toxicity. To date, three selective CDK4/6 inhibitors have received approval from the U.S. Food and Drug Administration (FDA), and 15 CDK4/6 inhibitors are in clinical trials for the treatment of cancers. In this perspective, we discuss the crucial roles of CDK4/6 in regulating the cell cycle and cancer cells, analyze the rationale for selectively inhibiting CDK4/6 for cancer treatment, review the latest advances in highly selective CDK4/6 inhibitors with different chemical scaffolds, explain the mechanisms associated with CDK4/6 inhibitor resistance and describe solutions to overcome this issue, and briefly introduce proteolysis targeting chimera (PROTAC), a new and revolutionary technique used to degrade CDK4/6.

Advances in cyclin-dependent kinase inhibitors for the treatment of melanoma

Introduction: Despite the recent advances in the treatment of malignant melanoma with immunotherapy and BRAF/MEK targeted agents, advanced disease still beholds a poor prognosis for a significant proportion of patients. Cyclin-dependent kinase (CDK) inhibitors have been investigated as novel melanoma therapeutics throughout a range of phase 1 and 2 trials, as single agents and in combination with established treatments. Areas covered: This article summarizes the rationale for, and development of CDK inhibitors in melanoma, with their evolution from pan-CDK inhibitors to highly specific agents, throughout clinical trials and finally their potential future use. Expert opinion: Whilst CDK inhibitors have been practice changing in breast cancer management, their efficacy is yet to be proven in melanoma. Combination with BRAF/MEK inhibitors has been hindered by dose-limiting toxicities, but their role may yet to be found within the spectrum of biomarker-derived personalized melanoma management. The effect that CDK inhibitors can have as an adjunct to immunotherapy also remains to be seen.

Nucleic acid binding mechanism of flavone derivative, riviciclib: Structural analysis to unveil anticancer potential

Despite burgeoned knowledge about the origin, growth, tissue interactions, and spread of cancer in recent years, the functional complexity and unique survival ability of cancer cells still make it difficult to target them. Riviciclib is a semi-synthetic derivative of rohitukine and possesses anticancer potential. Inhibition of nucleic acid activity in an uncontrolled dividing cell can form the basis for the development of new-age cancer therapeutics. The present study reports the molecular interaction between riviciclib and nucleic acid (DNA/tRNA) using spectroscopic and molecular docking studies in an attempt to comprehend its cellular toxicity as well as the nature and mode of binding between them. Vibrational spectroscopic results suggest that riviciclib intercalates DNA duplex and primarily binds with guanine, adenine, and thymine nucleobases. While in the case of riviciclib-tRNA complexation, riviciclib interacts mostly with uracil residues of the tRNA molecule. Besides nucleobases, riviciclib interacts with the sugar-phosphate backbone of both biomacromolecules. Conformationally, DNA alters from B-form to C-form, whereas tRNA shows no change in its native A-form. The order (10⁴ M^-1) of binding constant for riviciclib-nucleic acid complexation infer moderate to strong affinity of riviciclib with DNA and tRNA, respectively. Molecular docking explorations are further in corroboration with our spectroscopic outcomes.

Identification of a new series of flavopiridol-like structures as kinase inhibitors with high cytotoxic potency

In this work, unique flavopiridol analogs bearing thiosugars, amino acids and heterocyclic moieties tethered to the flavopiridol via thioether and amine bonds mainly on its C ring have been prepared. The analogs bearing thioether-benzimidazoles as substituents have demonstrated high cytotoxic activity in vitro against up to seven cancer cell lines. Their cytotoxic effects are comparable to those of flavopiridol. The most active compound 13c resulting from a structure-activity relationship (SAR) study and in silico docking showed the best antiproliferative activity and was more efficient than the reference compound. In addition, compound 13c showed significant nanomolar inhibition against CDK9, CDK10, and GSK3β protein kinases.

Cyclin-dependent kinase 7 inhibitors in cancer therapy

Cyclin-dependent kinase 7 (CDK7) plays crucial roles in the regulation of cell cycle and transcription that are tightly associated with cancer development and metastasis. The recent identification of the first covalent inhibitor which possesses high specificity against CDK7 prompts intense studies on designing highly selective CDK7 inhibitors and exploring their applications in cancer treatments. This review summarizes the latest biological studies on CDK7 and reviews the development of CDK7 inhibitors in preclinical and clinical evaluations, along with the prospects and potential challenges in this research area. CDK7 is an attractive anticancer target, and the discovery and development of CDK7 inhibitors has received much attention.

A Critical Review on Anticancer Mechanisms of Natural Flavonoid Puerarin

Cancer is one of the prominent global causes of death and the foremost worldwide health concern. Despite unprecedented progress in cancer chemoprevention, a vast number of cancers, however, remain an undefeatable challenge for treatment modalities. Immense therapeutic activities of puerarin contribute to its use in various health disorders. In this review, we explored the potential molecular mechanisms and targets of puerarin, proving its potential as a novel anticancer agent, for future cancer therapy and chemoprevention. Several mechanisms account for anticancer activity of puerarin which includes downregulation of NF-kB signalling pathway, mTOR signalling pathway, PI3K and BCl-2 proteins and upregulation of miR-16, caspase proteins, c- Jun N terminal kinase and extracellular signal-regulated kinase 1/2. These alterations result in inhibition of cancer cell proliferation and/or induction of apoptosis. Understanding the molecular mechanisms involved in chemotherapy and chemoprevention could aid in the more pronounced exploration of puerarin in effective cancer treatment.

Development of a CDK10/CycM in vitro Kinase Screening Assay and Identification of First Small-Molecule Inhibitors

Cyclin-dependent kinases (CDKs) constitute a family of 20 serine/threonine protein kinases that play pivotal roles in the regulation of numerous important molecular and cellular processes. CDKs have long been considered promising therapeutic targets in a variety of pathologies, and the recent therapeutic success of CDK4/6 inhibitors in breast cancers has renewed interest in their therapeutic potential. Small-molecule inhibitors have been identified for every human CDK, except for CDK10. The only recent discovery of an activating cyclin (CycM) for CDK10 enabled us to identify its first phosphorylation substrates and gain insights into its biological functions. Yet, our knowledge of this kinase remains incomplete, despite it being the only member of its family that causes severe human developmental syndromes, when mutated either on the cyclin or the CDK moiety. CDK10 small-molecule inhibitors would be useful in exploring the functions of this kinase and gauging its potential as a therapeutic target for some cancers. Here, we report the identification of an optimized peptide phosphorylation substrate of CDK10/CycM and the development of the first homogeneous, miniaturized CDK10/CycM in vitro kinase assay. We reveal the ability of known CDK inhibitors, among which clinically tested SNS-032, riviciclib, flavopiridol, dinaciclib, AZD4573 and AT7519, to potently inhibit CDK10/CycM. We also show that NVP-2, a strong, remarkably selective CDK9 inhibitor is an equally potent CDK10/CycM inhibitor. Finally, we validate this kinase assay for applications in high-throughput screening campaigns to discover new, original CDK10 inhibitors.

Evaluation of Pyrano[3,2 C] Quinoline Analogues as Anticancer Agents

Background:

Quinoline analogues exhibited diversified biological activities depending on the structure type. A number of natural products with pyrano[3,2-c]quinolone structural motifs and patented chromenes were reported as promising cytotoxic agents.

Objective:

The present study is aimed to evaluate a new series of pyrano[3,2-c]quinoline scaffolds derived from the fusion of bioactive quinolone pharmacophore with structurally diverse aryl substituted chromene for its cytotoxicity.

Methods:

A library of pyrano[3,2-c]quinoline analogues was prepared from one-pot multi component synthesis using various aromatic aldehydes, malononitrile and 2,4-dihydroxy-1-methylquinoline. The new synthetics were primarily screened for its cytotoxicity (IC50) against different human cancer cell lines in vitro. The promising synthetics were further evaluated in vitro for their potency against different kinase activity. The promising compounds were finally tested for their in vivo efficacy in SCID type mice HCT-116 tumor model.

Results:

The screening results revealed that compounds 4c, 4f, 4i and 4j showed promising activity in in vitro study. However, compound 4c was found to be the most potent candidate with 23% tumor growth inhibition in HCT-116 tumor mice model.

Conclusion:

The structure activity relationship suggested that 3-substitution on the aryl ring at C4 position of the pyrano[3,2 c]quinolone moiety seems to have an important position for cytotoxicity activity. However, 3- chloro substitution at C4 aryl ring showed a significant alteration of the bioactive conformer of the parent scaffold and outcome with compound 4c as the most potent candidate of the series.

Mechanisms of therapeutic CDK4/6 inhibition in breast cancer

Cyclin dependent kinase (CDK) 4/6 inhibitors have advanced the treatment of metastatic breast cancer by targeting the cell cycle machinery, interrupting intracellular and mitogenic hormone signals that stimulate proliferation of malignant cells. Preclinical evidence demonstrated that derangements of cyclin D1, CDK4/6, and retinoblastoma expression are common in breast cancer, and suggested a therapeutic benefit from interrupting this axis required for cell cycle progression. Studies of cell lines and animal models of breast cancer have demonstrated the complex interplay between the cell cycle and estrogen receptor and human epidermal growth receptor 2 signaling, which informs our understanding of synergistic use of CDK4/6 inhibitors with endocrine therapy, as well as mechanisms of resistance to endocrine therapy. Interestingly, estrogen receptor activity leads to upregulation of cyclin D1 expression, but the estrogen receptor is also in turn activated by cyclin D1, independent of estrogen binding. Early CDK inhibitors were nonspecific and limited by systemic toxicities, while the current generation of CDK4/6 inhibitors have shown promise in the treatment of hormone receptor-positive breast cancer. Preclinical investigations of the three CDK4/6 inhibitors approved by the US Food and Drug Administration (palbociclib, ribociclib, and abemaciclib) lend further insight into their mechanism of action, which will hopefully inform the future use and refinement of these therapies. Finally, we summarize evidence for additional novel CDK4/6 inhibitors currently in development.

Selective Synthesis of (+)-Dysoline

Dysoline, a novel chromone alkaloid isolated from Dysoxylum binectariferum, was reported to have selective cytotoxicity for HT1080 fibrosarcoma cells (IC₅₀ of 0.21 μM). Given the scarcity of natural material, a concise synthesis of (+)-dysoline was developed, allowing for further biological evaluation. An enantioselective nucleophile-catalyzed aldol lactonization formed the piperidine ring with control of relative and absolute stereochemistry. Construction of the C6-chromone core with complete regioselectivity was achieved using a Danheiser benzannulation.

C-glycosyl flavone from Urginea indica inhibits proliferation & angiogenesis & induces apoptosis via cyclin-dependent kinase 6 in human breast, hepatic & colon cancer cell lines

Background & objectives:

Search for novel compounds beneficial to the treatment of cancer attracts a great deal of attention. We earlier demonstrated the isolation of 5,7-dihydroxy-2-[4’-hydroxy-3’-(methoxymethyl)phenyl]-6-C-β-glucopyranosyl flavone, a novel C-glycosyl flavone from Urginea indica bulb. The present study was undertaken to investigate the effect of this novel compound on human normal epithelial and breast, hepatic and colon cancer cell lines.

Methods:

The maximum non-toxic concentration (MNTC) and cytotoxicity of C-glycosyl flavone were assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Cell cycle was analyzed by flow cytometry. Docking studies were performed to predict possible targets. Levels of cyclin-dependent kinase 1 (CDK1) and CDK6, Bcl2 and BAX and cytochrome c were quantified by specific ELISA. Mitochondrial membrane potential was determined using JC-1 dye. Apoptosis was quantified by Annexin V ELISA method.

Results:

Flow cytometry analysis demonstrated G0/G1 arrest. In silico docking studies predicted CDK1 and CDK6 as a possible target of C-glycosyl flavone. In vitro study confirmed CDK6 as the main target in C-glycosyl flavone-treated cancer cell lines. C-glycosyl flavone treatment also induced membrane blebbing, chromatin fragmentation and nucleosome formation. C-glycosyl flavone treatment caused marked loss of mitochondrial membrane potential, decrease in Bcl2/BAX ratio and activation of caspase-3 and release of caspase-9 and cytochrome c. In addition, C-glycosyl flavone inhibited the tumour-induced angiogenesis and reduced the vascular endothelial growth factor levels. Similarly, CDK6 inhibitor significantly inhibited proliferation and angiogenesis and induced apoptosis in tested cell lines.

Interpretation & conclusions:

The results indicate that C-glycosyl flavone may exert induction of apoptosis, cell cycle arrest and inhibition of angiogenesis via CDK6. Thus, targeting CDK6 using C-glycosyl flavone may serve as a novel therapeutic approach for the treatment of breast, hepatic and colon cancers.

An insight into the emerging role of cyclin-dependent kinase inhibitors as potential therapeutic agents for the treatment of advanced cancers

Cancer denotes a pathological manifestation that is characterized by hyperproliferation of cells. It has anticipated that a better understanding of disease pathogenesis and the role of cell-cycle regulators may provide an opportunity to develop an effective cancer therapeutic agents. Specifically, the cyclin-dependent kinases (CDKs) which regulate the transition of cell-cycle through different phases; have been identified as fundamental targets for therapeutic advances. It is an evident from experimental studies that several events leading to tumor growth occur by exacerbation of CDK4/CDK6 in G1-phase of cell division cycle. Additionally, the characteristics of S- and G2/M-phase regulated by CDK1/CDK2 are pivotal events that may lead to abrupt the cell division. Although, previously reported CDK inhibitors have shown remarkable results in pre-clinical studies, but have not yielded appreciable clinical results yet. Therefore, the development of clinically potent CDK inhibitors has remained to be a challenging task. However, continuous efforts has led to the development of some novel CDKs inhibitors that have emerged as a potent strategy for the treatment of advanced cancers. In this article, we have summarized the role of CDKs in cell-cycle regulation and tumorigenesis and recent advances in the development of CDKs inhibitors as a promising therapy for the treatment of advanced cancer. In addition, we have also performed a comparison of crystallographic studies to get valuable insight into the interaction mode differences of inhibitors, binding to CDK isoforms with apparently similar binding sites. The knowledge of ligand-specific recognition towards a particular CDK isoform may be applied as a key tool in future for the designing of isoform-specific inhibitors.

CDK9 inhibitors in acute myeloid leukemia

Current treatment for acute myeloid leukemia (AML) is less than optimal, but increased understanding of disease pathobiology and genomics has led to clinical investigation of novel targeted therapies and rational combinations. Targeting the cyclin-dependent kinase 9 (CDK9) pathway, which is dysregulated in AML, is an attractive approach. Inhibition of CDK9 leads to downregulation of cell survival genes regulated by super enhancers such as MCL-1, MYC, and cyclin D1. As CDK9 inhibitors are nonselective, predictive biomarkers that may help identify patients most likely to respond to CDK9 inhibitors are now being utilized, with the goal of improving efficacy and safety.

Discovery and Preclinical Development of IIIM-290, an Orally Active Potent Cyclin-Dependent Kinase Inhibitor

Rohitukine (1), a chromone alkaloid isolated from Indian medicinal plant Dysoxylum binectariferum, has inspired the discovery of flavopiridol and riviciclib, both of which are bioavailable only via intravenous route. With the objective to address the oral bioavailability issue of this scaffold, four series of rohitukine derivatives were prepared and screened for Cdk inhibition and cellular antiproliferative activity. The 2,6-dichloro-styryl derivative IIIM-290 (11d) showed strong inhibition of Cdk-9/T1 (IC₅₀ 1.9 nM) kinase and Molt-4/MIAPaCa-2 cell growth (GI₅₀ < 1.0 μM) and was found to be highly selective for cancer cells over normal fibroblast cells. It inhibited the cell growth of MIAPaCa-2 cells via caspase-dependent apoptosis. It achieved 71% oral bioavailability with in vivo efficacy in pancreatic, colon, and leukemia xenografts at 50 mg/kg, po. It did not have CYP/efflux-pump liability, was not mutagenic/genotoxic or cardiotoxic, and was metabolically stable. The preclinical data presented herein indicates the potential of 11d for advancement in clinical studies.

Tetrahydro-3H-pyrazolo[4,3-a]phenanthridine-based CDK inhibitor

Cyclin-dependent kinases have emerged as important targets for cancer therapy.

Emerging data on improving response to hormone therapy: the role of novel targeted agents

INTRODUCTION

Hormone receptor positive (HR+) breast cancer represents the most common subtype of breast cancer. Metastatic HR+ breast cancer may develop resistance to standard hormone therapies, arising from genomic alterations in the estrogen receptor and/or upregulation of other signal transduction pathways. Areas covered: In this review, we discuss hormone resistance and strategies to overcome it, from the pre-clinical and clinical perspectives. This review includes a discussion of inhibition of the PI3K/AKT/mTOR, CDK 4/6, histone deacetylation, fibroblast growth factor receptor, and immune pathways, based on review of relevant literature. Expert commentary: Several emerging novel therapies to improve the response to hormone therapy are approved or are in development. The most promising agents at present are inhibitors of CDK 4/6 and mTOR, which have already been incorporated into treatment in the advanced stage setting and are under study for early stage disease.

Puerarin suppresses LPS-induced breast cancer cell migration, invasion and adhesion by blockage NF-κB and Erk pathway

BACKGROUND

Chronic inflammation is a major risk factor for the development and metastatic progression of breast cancer. Puerarin has long been used as traditional Chinese medicine, which possesses manifold physiological activities, including anti-inflammation and anti-cancer activities. However, its anti-cancer metastasis activity in breast cancer cell inflammation-mediated have not been studied.

METHODS

Cell viability was detected with Cell Counting Kit (CCK)-8. Transwell migration and invasion assay were performed to evaluate cell migration and invasion, respectively. Enzyme-linked immunosorbent assay (ELISA) was conducted to analysis the expression of inflammatory factor. In addition, mRNA and protein levels of related cytokines were determined by qRT- PCR assay and western blot analysis, respectively.

RESULTS

In this study, puerarin significantly inhibited lipopolysaccharide (LPS)-induced MCF-7 and MDA-MB-231 cell migration, invasion and adhesion. The mRNA and protein levels revealed that puerarin treatment effectively negated the expression of CCR7, CXCR4, MMP-2, MMP-9, ICAM and VCAM in LPS- activated MCF-7 and MDA-MB-231 cells. Further, the expression of inflammatory factor TNF-α and IL-6 in cell culture supernatant remarkably reduced. Finally, the result indicated that puerarin abrogated the NF-κB activation in breast cancer cells stimulated by LPS, which is mediated through inhibition of phosphorylation of p65 and IκBα. Also, puerarin inhibited phosphorylation of Erk in breast cancer cells LPS-induced.

CONCLUSIONS

This present study revealed that puerarin might be a novel therapeutic drug for breast cancer treatment.

Inhibitors of cyclin-dependent kinases as cancer therapeutics

Over the past two decades there has been a great deal of interest in the development of inhibitors of the cyclin-dependent kinases (CDKs). This attention initially stemmed from observations that different CDK isoforms have key roles in cancer cell proliferation through loss of regulation of the cell cycle, a hallmark feature of cancer. CDKs have now been shown to regulate other processes, particularly various aspects of transcription. The early non-selective CDK inhibitors exhibited considerable toxicity and proved to be insufficiently active in most cancers. The lack of patient selection biomarkers and an absence of understanding of the inhibitory profile required for efficacy hampered the development of these inhibitors. However, the advent of potent isoform-selective inhibitors with accompanying biomarkers has re-ignited interest. Palbociclib, a selective CDK4/6 inhibitor, is now approved for the treatment of ER+/HER2- advanced breast cancer. Current developments in the field include the identification of potent and selective inhibitors of the transcriptional CDKs; these include tool compounds that have allowed exploration of individual CDKs as cancer targets and the determination of their potential therapeutic windows. Biomarkers that allow the selection of patients likely to respond are now being discovered. Drug resistance has emerged as a major hurdle in the clinic for most protein kinase inhibitors and resistance mechanism are beginning to be identified for CDK inhibitors. This suggests that the selective inhibitors may be best used combined with standard of care or other molecularly targeted agents now in development rather than in isolation as monotherapies.

Targeting CDK9: a promising therapeutic opportunity in prostate cancer

Cyclin-dependent kinase 9 (CDK9) is a key transcriptional regulator and a lucrative target for cancer treatment. Targeting CDK9 can effectively confine the hyperactivity of androgen receptor and the constitutive expression of anti-apoptotic proteins; both being main causes of prostate cancer (PCa) development and progression. In castrate-resistant PCa, traditional therapies that only target androgen receptor (AR) have become obsolete due to reprograming in AR activity to make the cells independent of androgen. CDK9 inhibitors may provide a new and better therapeutic opportunity over traditional treatment options by targeting both androgen receptor activity and anti-apoptotic proteins, improving the chances of positive outcomes, especially in patients with the advanced disease. This review focuses on biological functions of CDK9, its involvement with AR and the potential for therapeutic opportunities in PCa treatment.

Maintaining Genome Stability in Defiance of Mitotic DNA Damage

The implementation of decisions affecting cell viability and proliferation is based on prompt detection of the issue to be addressed, formulation and transmission of a correct set of instructions and fidelity in the execution of orders. While the first and the last are purely mechanical processes relying on the faithful functioning of single proteins or macromolecular complexes (sensors and effectors), information is the real cue, with signal amplitude, duration, and frequency ultimately determining the type of response. The cellular response to DNA damage is no exception to the rule. In this review article we focus on DNA damage responses in G2 and Mitosis. First, we set the stage describing mitosis and the machineries in charge of assembling the apparatus responsible for chromosome alignment and segregation as well as the inputs that control its function (checkpoints). Next, we examine the type of issues that a cell approaching mitosis might face, presenting the impact of post-translational modifications (PTMs) on the correct and timely functioning of pathways correcting errors or damage before chromosome segregation. We conclude this essay with a perspective on the current status of mitotic signaling pathway inhibitors and their potential use in cancer therapy.

Anticancer Alkaloids from Trees: Development into Drugs

Trees have made an enormous phytochemical contribution in anticancer drugs' development more than any other life form. The contributions include alkaloids that are biosynthesized in various ways and yield. Lead alkaloids isolated from the trees are taxol and camptothecins that currently have annual sales in billion dollars. Other important alkaloids isolated from these life forms include rohitukine, harringtonine, acronycine, thalicarpine, usambarensine, ellipticine, and matrines. Studies on their mechanism of action and target on the DNA and protein of cancerous cells aided the development of potent hemisynthesized congeners. The molecules and their congeners passed/are passing a long period of historical development before approved as antineoplastic drugs for cancer chemotherapy. Some of them did not find the application as anticancer drugs due to ineffectiveness in clinical trials; others are generating research interest in the antineoplastic activity at the present and have reached clinical trial stages. Potentials in antineoplastic molecules from trees are high and are hoped to be commensurate with cancer types afflicting human society in the future.

Cyclin Dependent Kinase 9 Inhibitors for Cancer Therapy

Cyclin dependent kinase (CDK) inhibitors have been the topic of intense research for nearly 2 decades due to their widely varied and critical functions within the cell. Recently CDK9 has emerged as a druggable target for the development of cancer therapeutics. CDK9 plays a crucial role in transcription regulation; specifically, CDK9 mediated transcriptional regulation of short-lived antiapoptotic proteins is critical for the survival of transformed cells. Focused chemical libraries based on a plethora of scaffolds have resulted in mixed success with regard to the development of selective CDK9 inhibitors. Here we review the regulation of CDK9, its cellular functions, and common core structures used to target CDK9, along with their selectivity profile and efficacy in vitro and in vivo.

The landscape of gene fusions and somatic mutations in salivary gland neoplasms - Implications for diagnosis and therapy

Recent studies of the genomic landscape of salivary gland tumors have provided important insights into the molecular pathogenesis of these tumors. The most consistent alterations identified include a translocation-generated gene fusion network involving transcription factors, transcriptional coactivators, tyrosine kinase receptors, and other kinases. In addition, next-generation sequencing studies of a few subtypes of salivary neoplasms have revealed hotspot mutations in individual genes and mutations clustering to specific pathways frequently altered in cancer. Although limited, these studies have opened up new avenues for improved classification and targeted therapies of salivary gland cancers. In this review, we summarize the latest developments in this field, focusing on tumor types for which clinically important molecular data are available.

Induction of Therapeutic Senescence in Vemurafenib-Resistant Melanoma by Extended Inhibition of CDK4/6

Dysregulation of the p16-cyclin D1-CDK4/6-Rb pathway occurs frequently in melanoma; however, the therapeutic efficacy of CDK4/6 inhibition remains to be critically evaluated. We demonstrate that CDK4/6 inhibition inhibits melanoma progression through induction of senescence. Palbociclib, a specific CDK4/6 inhibitor, rapidly induces cell cycle arrest within 24 hours and continued exposure for 8 days or longer induces senescence. The induction of senescence correlates with inhibition of mTOR and more specifically mTORC1 signaling. Vemurafenib, a specific BRAF(V600E) inhibitor, has significant clinical efficacy in BRAF(V600E)-positive melanomas, but its impact is hampered by a rapid acquisition of resistance. Strikingly, we found that vemurafenib-resistant tumors remain sensitive to palbociclib, suggesting that initial treatment with vemurafenib followed by palbociclib with or without mTOR inhibitors might provide an avenue to overcome recurrence of vemurafenib-resistant metastatic disease. Taken together, these results support palbociclib as a promising therapeutic for treatment of melanoma. Cancer Res; 76(10); 2990-3002. ©2016 AACR.

Novel Treatments in Development for Melanoma

The past several years can be considered a renaissance era in the treatment of metastatic melanoma. Following a 30-year stretch in which oncologists barely put a dent in a very grim overall survival (OS) rate for these patients, things have rapidly changed course with the recent approval of three new melanoma drugs by the FDA. Both oncogene-targeted therapy and immune checkpoint blockade approaches have shown remarkable efficacy in a subset of melanoma patients and have clearly been game-changers in terms of clinical impact. However, most patients still succumb to their disease, and thus, there remains an urgent need to improve upon current therapies. Fortunately, innovations in molecular medicine have led to many silent gains that have greatly increased our understanding of the nature of cancer biology as well as the complex interactions between tumors and the immune system. They have also allowed for the first time a detailed understanding of an individual patient's cancer at the genomic and proteomic level. This information is now starting to be employed at all stages of cancer treatment, including diagnosis, choice of drug therapy, treatment monitoring, and analysis of resistance mechanisms upon recurrence. This new era of personalized medicine will foreseeably lead to paradigm shifts in immunotherapeutic treatment approaches such as individualized cancer vaccines and adoptive transfer of genetically modified T cells. Advances in xenograft technology will also allow for the testing of drug combinations using in vivo models, a truly necessary development as the number of new drugs needing to be tested is predicted to skyrocket in the coming years. This chapter will provide an overview of recent technological developments in cancer research, and how they are expected to impact future diagnosis, monitoring, and development of novel treatments for metastatic melanoma.

Metabolism and pharmacokinetics of 8-hydroxypiperidinylmethyl-baicalein (BA-j) as a novel selective CDK1 inhibitor in monkey

Cyclin-dependent kinase 1 (CDK1) is the only necessary CDK in the cell proliferation process and a new target in the research and development of anti-cancer drugs. 8-Hydroxypiperidinemethyl-baicalein (BA-j) is a Mannich base derivative of baicalein (BA) isolated from Scutellaria baicalensis, as a novel selective CDK1 inhibitor. 12 metabolites of BA-j in the monkey urine were identified by LC-MS-MS and (1)H NMR. The major metabolic pathways of BA-j, by capturing oxygen free radicals ((.)O2(-)) and releasing peroxides (H2O2), are degraded into active intermediate metabolite dihydroflavonol, then into main metabolite M179 by Shiff reaction, second metabolite M264 by sulfation, trace amount of metabolite M559 by glucuronidation UGT1A9, and without metabolism by CYP3A4. The metabolic process of BA-j by regulating intracellular reactive oxygen species (ROS) was related with BA-j selectively inducing apoptosis in cancer cells. Pharmacokinetics of 10mg/kg oral BA-j in monkey by HPLC-UV was best fitted to a two-compartment open model, with t1/2(β) of 4.2h, Cmax 25.4μM at 2h, and Vd 12.6L, meaning the drug distributing widely in body fluids with no special selectivity to certain tissues, and being able to permeate through the blood-brain barrier. The protein binding rate of BA-j was 91.8%. BA-j has excellent druggability for oral administration or injection, and it may be developed into a novel anti-cancer drug as a selective CDK1 inhibitor.

BA-j as a novel CDK1 inhibitor selectively induces apoptosis in cancer cells by regulating ROS

Cyclin-dependent kinase 1 (CDK1) is the only necessary CDK in cell proliferation and a novel target in the development of anticancer drugs. 8-Hydroxypiperidinemethyl-baicalein (BA-j) is a novel selective CDK1 inhibitor with broad spectrum anti-cancer activity (IC₅₀ 12.3 μM) and 2 tumor xenografts. Because of the differential mechanisms controlling redox-states in normal and cancer cells, BA-j can capture oxygen free radicals (^·O₂⁻) and selectively increase the level of H₂O₂ in cancer cells, thereby specifically oxidize and activate the intrinsic apoptosis pathway bypassing the extrinsic death receptor pathway, thus inducing apoptosis in cancer cells rather than in normal cells. BA-j is different from cytotoxic anticancer drugs which can activate both the intrinsic apoptosis pathway and the extrinsic death receptor pathway, and therefore harm normal cells while killing cancer cells. The molecular and biochemical mechanisms of reactive oxygen species (ROS) regulation suggest that BA-j may be developed into a novel anticancer agent.