CDK2 In Complex Research Articles

Structural simplification of Osimertinib to elaborate new indolyle-pyrimidine-5-carbonitrile derivatives with Anti-proliferative and Anti-SARS-CoV-2 activities assisted by molecular dynamic simulation

Based on the simplicity and modification of the medication osimertinib, two new series of indolyle-pyrimidine-5-carbonitrile scaffolds were created and synthesized with dual action as anti-SARS-Cov-2 and anticancer. The newly created heterocyclic compounds' chemical structures were effectively characterized. With IC50 values of 18.52, 20.89, and 19.85, respectively, compounds 9b, 10, and 15 had inhibitory actions against SARS-CoV-2 when compared to remdesivir and chloroquine, which served as pharmacological controls and had IC50 values of 3.38 μM and 24.9 μM, respectively.Furthermore, compounds 9a and 13 showed anti-proliferative activity against HepG2 cell lines with IC50s of 5.63 μM and 3.06 μM, respectively, in comparison to doxorubicin's IC50 of 7.4 μM. qRT-PCR revealed that HepG2 cells treated with compounds 9a and 13 showed increased p53 expression levels and decreased CDK1 and PI3K expression levels in comparison to doxorubicin. Molecular dynamics simulations of 20 ns duration were performed with PI3Kα, PI3Kγ, and CDK and active compound complexes. The results confirm that compound 13 has the potential to be a therapeutic candidate for additional preclinical and clinical research, as indicated by the molecular docking data.

Pseudolaric Acid B Inhibits FLT4-induced Proliferation and Migration in Non-small Cell Lung Cancer.

Non-Small Cell Lung Cancer (NSCLC) has attracted much attention on account of the high incidence and mortality of cancers. Vascular Endothelial Growth Factor Receptor 3 (VEGFR3/FLT4), which is a highly expressed receptor in NSCLC, greatly regulates cancer proliferation and migration. Pseudolaric Acid B (PAB) is a diterpenoid acid with antitumor activity isolated from Pseudolarix kaempferi. This study aimed to explore the inhibitory effect of PAB targeting FLT4 in NSCLC. Cell membrane chromatography was used to evaluate the affinity of PAB binding on FLT4. NCIH1299 cells were used in this study, and an MTT assay was performed to determine the anti-proliferation effect of PAB. Cell cycle analysis was conducted to study the cycle arrest of PAB. Wound healing and Transwell assays assessed the rate of cell migration. Western blot analysis evaluated the expression of related proteins. PAB showed strong affinity to FLT4 with a KD value of 3.01 × 10- 6 M. Targeting FLT4 by PAB inactivated downstream P38MAPK and PI3K/AKT pathways, which inhibited the proliferation of NCI-H1299 cells. Meanwhile, PAB promoted G2/M phase arrest by influencing CyclinB1 and CDK1 complex formation to inhibit NCI-H1299 cell growth, but the effect was attenuated by knocking down the FLT4. Besides, PAB regulated MMP9 secretion through the Wnt/β-catenin signaling pathway to inhibit NCI-H1299 cell migration. However, the ability of PAB to inhibit migration was significantly weakened by FLT4 knockdown in NCI-H1299 cells. PAB can inhibit the proliferation and migration of NSCLC cells through targeting FLT4 and is expected to be a promising FLT4 inhibitor for NSCLC treatment.

CDK2 and CDK4: Cell Cycle Functions Evolve Distinct, Catalysis-Competent Conformations, Offering Drug Targets.

Cyclin-dependent kinases (CDKs), particularly CDK4 and CDK2, are crucial for cell cycle progression from the Gap 1 (G1) to the Synthesis (S) phase by phosphorylating targets such as the Retinoblastoma Protein (Rb). CDK4, paired with cyclin-D, operates in the long G1 phase, while CDK2 with cyclin-E, manages the brief G1-to-S transition, enabling DNA replication. Aberrant CDK signaling leads to uncontrolled cell proliferation, which is a hallmark of cancer. Exactly how they accomplish their catalytic phosphorylation actions with distinct efficiencies poses the fundamental, albeit overlooked question. Here we combined available experimental data and modeling of the active complexes to establish their conformational functional landscapes to explain how the two cyclin/CDK complexes differentially populate their catalytically competent states for cell cycle progression. Our premise is that CDK catalytic efficiencies could be more important for cell cycle progression than the cyclin-CDK biochemical binding specificity and that efficiency is likely the prime determinant of cell cycle progression. We observe that CDK4 is more dynamic than CDK2 in the ATP binding site, the regulatory spine, and the interaction with its cyclin partner. The N-terminus of cyclin-D acts as an allosteric regulator of the activation loop and the ATP-binding site in CDK4. Integrated with a suite of experimental data, we suggest that the CDK4 complex is less capable of remaining in the active catalytically competent conformation, and may have a lower catalytic efficiency than CDK2, befitting their cell cycle time scales, and point to critical residues and motifs that drive their differences. Our mechanistic landscape may apply broadly to kinases, and we propose two drug design strategies: (i) allosteric Inhibition by conformational stabilization for targeting allosteric CDK4 regulation by cyclin-D, and (ii) dynamic entropy-optimized targeting which leverages the dynamic, entropic aspects of CDK4 to optimize drug binding efficacy.

Abstract LB265: IpY.20: Innovative strategies for post-CDK estrogen receptor (ER)+ metastatic breast cancer (mBC)

Abstract Cyclin-dependent kinases (CDK) 4/6 are key cell cycle regulators that form complexes with cyclin D1 and the master regulator p27Kip1. This ternary complex acts downstream of the ER- and HER2-pathways, which drive cell proliferation. CDK4/6 phosphorylates the Retinoblastoma protein and other substrates, and keeps p27 from inhibiting G1-associated CDK2. Targeted inhibition of CDK4/6 (CDK4/6i) blocks the growth of ER+ and HER2+ BC by dissolving the CDK4/6-cyclin D1 complex and permitting the shuttling of p27 to inhibit CDK2 complex. Approval of CDK 4/6i such as palbociclib, though a game changer for ER+ mBC, resulted in tumor resistance, leaving patients without effective treatments and a 5-yr survival of only 30%. Although CDK2 inhibitors (CDK2i) address compensatory CDK2 activity bypassing CDK4/6i, a key resistance mechanism, they lack selectivity due to CDK homology, resulting in off-target toxicity. To inhibit CDK2/4/6 simultaneously, combinations of CDK4/6i and CDK2i monotherapies were attempted, but the lack of coordination between CDK4/6 and CDK2 inhibition resulted in suboptimal efficacy. Concarlo presents a unique therapeutic rationale for directly targeting the CDK master regulator p27 to simultaneously inhibit CDK2/4/6 in a concerted manner, one that is guided by the role of p27 to turn all of the G1 CDKs ON and OFF during periods of proliferation and quiescence, respectively. This transition is facilitated by BRK (Breast tumor kinase)-mediated phosphorylation of p27. When p27 is Y phosphorylated, it converts CDK4/6 and CDK2 into open, active complexes. An endogenous BRK-spliced variant ALT can competitively bind to p27, block Y phosphorylation and lock CDK2/4/6 in the OFF conformation. Concarlo engineered a shorter variant of ALT (CCL20) and packaged in cationic liposomes for intracellular delivery, creating a novel IpY.20 drug product. As a single agent, IpY.20 inhibits cell proliferation in treatment-naïve and CDK4i-resistant HR+ cells with reduced non-tumor cell activity. In combination, IpY.20 enhances CDK4/6i responses in treatment-naïve HR+ cells, making it a potential front-line mBC therapy. While other CDKi activity is limited to cytostasis, IpY.20 shows dual cytostasis-cytotoxicity, potentially a more durable option. IpY.20 does not cause neutropenia commonly seen with other CDKis, and rescues the CDK4/6i-induced neutropenia in mice, suggesting better clinical tolerability. These findings underscore the significance of coordinated targeting of CDK2/4/6, making IpY.20 a first-in-class product uniquely exploiting p27-mediated CDK2/4/6 regulation. Direct targeting of p27 presents a new treatment paradigm bypassing the challenges of ATP-competitive CDKis, with potential to expand into tumor types with aberrant p27, CDK2/4/6 activity, or RAS/MAPK pathways that increase CDK4/6 activity. Citation Format: Grace Chen, Natalie Dudas, Kate Coleman, Carolina Guido, Natalia Zisman, Krishna Allamneni, Stacy Wister Blain. IpY.20: Innovative strategies for post-CDK estrogen receptor (ER)+ metastatic breast cancer (mBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB265.

Abstract 5709: PF-07104091, a first-in-class CDK2-selective inhibitor for the treatment of HR+/HER2- breast cancer and CCNE1high ovarian cancer

Abstract The selective inhibition of Cyclin\CDK complexes controlling cell cycle progression has been established as cancer therapy by selective CDK4/6 inhibitors in HR+/HER2- breast cancer. Expanding control of the cell cycle through selective inhibition of CDK2 offers novel therapeutic opportunities in cancer, including targeting CCNE1 amplified tumors and countering resistance to CDK4\6 inhibitors in ER+ breast cancer. PF-07104091 is a first-in-class CDK2-selective inhibitor under clinical investigation in patients with HR+/HER2- breast cancer and ovarian cancer. Preclinical studies using PF-07104091 establish the therapeutic impact of CDK2 inhibition in both diseases and highlight distinct mechanistic roles for CDK2 in control of cancer cell proliferation. In models of CCNE1 amplified ovarian cancer, CDK2 plays the dominant role in control of RB1 phosphorylation and the G1 checkpoint. CDK2 inhibition with PF-07104091 induces G1 growth arrest and controls tumor xenograft growth as single agent therapy. In ER+ breast models CDK2 plays a supportive role in the control of RB1 phosphorylation cooperating with CDK4\6. Whole genome CRISPR KO and CRISPR activation screens in conjunction with CDK4\6 inhibition establish CDK2 KO as a primary sensitizer to CDK4\6 inhibition, and support Cyclin E\CDK2 complexes as the driver of resistance to CDK4\6 inhibitors in ER+ breast models. PF-07104091 combined with CDK4\6 inhibitor Palbociclib or CDK4-selective inhibitor PF-0060 synergistically controls proliferation of ER+ BC cells in vitro and induces tumor regression in ER+ BC xenograft models, including PDX models with acquired resistance to CDK4\6 inhibitors and endocrine therapy. Citation Format: Chen Shen, Ming Qiu, Nanni Huser, Bernadette Pascual, Qin Zhang, Todd VanArsdale, Anwar Murtaza, Jonathan Almaden, berly Kim, Lars Anders, Koleen Eisele. PF-07104091, a first-in-class CDK2-selective inhibitor for the treatment of HR+/HER2- breast cancer and CCNE1high ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5709.

Computational exploration of allosteric inhibitors targeting CDK4/CDK6 proteins: a promising approach for multi-target drug development

Cyclin-dependent kinases (CDKs) play a pivotal role in orchestrating the intricate regulation of the cell cycle, a fundamental process governing cell growth and division. In particular, CDK4 and CDK6 are critical for the transition from the G1 phase to the S phase, where Deoxyribonucleic acid (DNA) replication occurs, and their dysregulation is linked to various diseases, notably cancer. While ATP-binding site inhibitors for CDKs are well-documented, this study focuses on uncovering allosteric inhibitors, providing a fresh perspective on CDK inhibition. Computational techniques were employed in this investigation, utilizing Molecular Operating Environment (MOE) for virtual screening of a drug-like compound library. Moreover, the stability of the most promising binding inhibitors was assessed through Molecular Dynamics (MD) simulations and MMPBSA/MMGBSA analyses. The outcome reveals that three inhibitors (C1, C2, and C3) exhibited the strongest binding affinity for CDK4/CDK6, as corroborated by docking and simulation analyses. The computed binding energies ranged from −6.1 to −7.6 kcal/mol, underscoring the potency of these allosteric inhibitors. Notably, this study identifies key residues (PHE31, HIS95, HIS100, VAL101, ASP102, ASP104, and THR107) that play pivotal roles in mediating inhibitor binding within the allosteric sites. Among the findings, the C1–CDK4 complex and C2–CDK6 complex emerge as particularly promising inhibitors, exhibiting high binding energies, favorable interaction patterns, and sustained presence within the active site. This study contributes significantly to the pursuit of multi-target drugs against CDK4/CDK6 proteins, with potential implications for the development of innovative therapies across various disorders, including cancer and other cell cycle-related conditions. Communicated by Ramaswamy H. Sarma

CDK4 phosphorylation status and rational use for combining CDK4/6 and BRAF/MEK inhibition in advanced thyroid carcinomas.

CDK4/6 inhibitors (CDK4/6i) have been established as standard treatment against advanced Estrogen Receptor-positive breast cancers. These drugs are being tested against several cancers, including in combinations with other therapies. We identified the T172-phosphorylation of CDK4 as the step determining its activity, retinoblastoma protein (RB) inactivation, cell cycle commitment and sensitivity to CDK4/6i. Poorly differentiated (PDTC) and anaplastic (ATC) thyroid carcinomas, the latter considered one of the most lethal human malignancies, represent major clinical challenges. Several molecular evidence suggest that CDK4/6i could be considered for treating these advanced thyroid cancers. We analyzed by two-dimensional gel electrophoresis the CDK4 modification profile and the presence of T172-phosphorylated CDK4 in a collection of 98 fresh-frozen tissues and in 21 cell lines. A sub-cohort of samples was characterized by RNA sequencing and immunohistochemistry. Sensitivity to CDK4/6i (palbociclib and abemaciclib) was assessed by BrdU incorporation/viability assays. Treatment of cell lines with CDK4/6i and combination with BRAF/MEK inhibitors (dabrafenib/trametinib) was comprehensively evaluated by western blot, characterization of immunoprecipitated CDK4 and CDK2 complexes and clonogenic assays. CDK4 phosphorylation was detected in all well-differentiated thyroid carcinomas (n=29), 19/20 PDTC, 16/23 ATC and 18/21 thyroid cancer cell lines, including 11 ATC-derived ones. Tumors and cell lines without phosphorylated CDK4 presented very high p16CDKN2A levels, which were associated with proliferative activity. Absence of CDK4 phosphorylation in cell lines was associated with CDK4/6i insensitivity. RB1 defects (the primary cause of intrinsic CDK4/6i resistance) were not found in 5/7 tumors without detectable phosphorylated CDK4. A previously developed 11-gene expression signature identified the likely unresponsive tumors, lacking CDK4 phosphorylation. In cell lines, palbociclib synergized with dabrafenib/trametinib by completely and permanently arresting proliferation. These combinations prevented resistance mechanisms induced by palbociclib, most notably Cyclin E1-CDK2 activation and a paradoxical stabilization of phosphorylated CDK4 complexes. Our study supports further clinical evaluation of CDK4/6i and their combination with anti-BRAF/MEK therapies as a novel effective treatment against advanced thyroid tumors. Moreover, the complementary use of our 11 genes predictor with p16/KI67 evaluation could represent a prompt tool for recognizing the intrinsically CDK4/6i insensitive patients, who are potentially better candidates to immediate chemotherapy.

The Role of Cyclin-Dependent Kinases (CDK) 4/6 in the Ovarian Tissue and the Possible Effects of Their Exogenous Inhibition.

The combination of cyclin-dependent kinase (CDK) 4/6 inhibitors with endocrine therapy is the standard treatment for patients with HR+/HER2- advanced breast cancer. Recently, this combination has also entered the early setting as an adjuvant treatment in patients with HR+/HER2- disease at a high risk of disease recurrence following (neo)adjuvant chemotherapy. Despite their current use in clinical practice, limited data on the potential gonadotoxicity of CDK4/6 inhibitors are available. Hence, fully informed treatment decision making by premenopausal patients concerned about the potential development of premature ovarian insufficiency and infertility with the proposed therapy remains difficult. The cell cycle progression of granulosa and cumulus cells is a critical process for ovarian function, especially for ensuring proper follicular growth and acquiring competence. Due to the pharmacological properties of CDK4/6 inhibitors, there could be a potentially negative impact on ovarian function and fertility in women of reproductive age. This review aims to summarize the role of the cyclin D-CDK4 and CDK6 complexes in the ovary and the potential impact of CDK4/6 inhibition on its physiological processes.

Abstract 1143: Development of a CDK2-selective small molecule inhibitor INCB123667 for the treatment of CCNE1hi breast cancers

Abstract Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors have been approved for treatment of metastatic ER+ HER2− breast cancer as monotherapy or in combination with endocrine therapy. However, many patients become resistant to CDK4/6 therapy due to various mechanisms such as loss of tumor suppressor Rb, hyperactivation of CDK4/6, and/or CDK2/Cyclin E1 expression and activity, resulting in a highly unmet clinical need. Triple-negative breast cancers (TNBC), owing to a lack of hormone receptor (HR) expression and extensive heterogeneity, remain notoriously aggressive and unresponsive to current therapies. CCNE1 overexpression or amplification has been shown to be an oncogenic driver associated with poor clinical outcomes in ovarian, gastric, endometrial, and HR+ breast cancers. CCNE1hi cancers are dependent on CDK2 for growth and survival. CDK2 in complex with CCNE1 phosphorylates Rb, resulting in E2F target gene expression and G1 to S-phase cell cycle progression. Using a potent and selective CDK2 inhibitor, INCB123667, we demonstrate the efficacy of CDK2 inhibition in CCNE1hi breast cancer models. Analysis of genome-wide CRISPR screen data identified a subset of CCNE1hi breast cancer models dependent on CDK2 comprised of basal and luminal breast cancer subtypes, including TNBC, ER+ HER2−, and HR− HER2+ models. Two CCNE1hi cell lines, HCC1569 and MDAMB157, were evaluated in cell assays monitoring pRb, S-phase, and growth inhibition, and found to be sensitive to treatment with INCB123667 and insensitive to multiple CDK4/6 inhibitors. Through extensive biochemical studies, INCB123667 was observed to be potently active against CDK2 at subnanomolar range and inactive against other CDKs (CDK1, CDK4, CDK6, CDK7, and CDK9). INCB123667 also selectively induced senescence in CCNE1hi HCC1569 cells. In contrast, CCNE1 nonamplified cell lines, MCF7 and T47D, were inactive in pRb, S-phase, and growth inhibition assays when treated with INCB123667. Significant tumor growth inhibition was observed in CCNE1hi PDX and xenograft models with minimal body weight loss. We also observed dose-dependent inhibition of CDK2 substrates, including pRb S780, both in vitro and in vivo. To further characterize downstream signaling and transcriptional changes with CDK2 inhibition, we identified a discrete gene signature associated with cell cycle regulation, which was notably distinct from CDK4/6 responsive target genes. In conclusion, we have demonstrated CDK2 activity in CCNE1hi breast cancers using INCB123667, a potent and selective small molecule inhibitor of CDK2 currently in clinical development. Treatment resulted in cell growth inhibition and antitumor activity in vitro and in vivo. Our data demonstrate the therapeutic potential of CDK2 inhibition in CCNE1hi HR+ HER2− and TNBC breast cancer models. Acknowledgments: R&D services provided by Pharmaron, Crown Bioscience, and Champions Oncology Citation Format: Saswati Chand, Michael Hansbury, Yvonne Lo, Pat Feldman, Justine Carl, Cynthia Timmers, Joshua Hummel, Susan Wee, Sunkyu Kim. Development of a CDK2-selective small molecule inhibitor INCB123667 for the treatment of CCNE1hi breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1143.

On the assembly of the mitotic spindle, bistability and hysteresis

During cell division, the transition from interphase to mitosis is dictated by activation of the cyclin B-cdk1 (Cdk1) complex, master mitotic kinase. During interphase, Cdk1 accumulates in an inactive state (pre-Cdk1). When Cdk1 overcomes a certain threshold of activity upon initial activation of pre-Cdk1, then the stockpiled pre-Cdk1 is rapidly converted into overshooting active Cdk1, and mitosis is established irreversibly in a switch-like fashion. This is granted by positive Cdk1 activation loops and the concomitant inactivation of Cdk1 counteracting phosphatases, empowering Cdk1 activity and favoring the Cdk1-dependent phosphorylations that are required to establish mitosis. These circuitries prevent backtracking and ensure unidirectionality so that interphase and mitosis are considered bistable states. Mitosis also shows hysteresis, meaning that the levels of Cdk1 activity needed to establish mitosis are higher than those required to maintain it; therefore, once in mitosis cells can tolerate moderate drops in Cdk1 activity without exiting mitosis. Whether these features have other functional implications in addition to the general action of preventing backtracking is unknown. Here, we contextualize these concepts in the view of recent evidence indicating that loss of activity of small and compartmentalized amounts of Cdk1 within mitosis is necessary to assemble the mitotic spindle, the structure required to segregate replicated chromosomes. We further propose that, in addition to prevent backtracking, the stability and hysteresis properties of mitosis are also essential to move forward in mitosis by allowing cells to bear small, localized, drops in Cdk1 activity that are necessary to build the mitotic spindle.

Modulating structural dynamics of dual drugs for CDK4 complex addressing prostate cancer

Multiple drug therapies have been proposed to inhibit dysregulated activation of cyclin-dependent kinases (CDK) 4/6, resulting in primary or secondary resistance or partial deactivation. Owing to the presence of drug repurposing and drug combination therapies, the current study targeted p27-CDK4/cyclin D1 complex to investigate nine different experimentally verified drug combinations targeting the central binding groove (CBG) and ATP binding site. Our findings reveal top drug combinations that impart stability to dimer in active conformation are: ShetA2-Palbociclib, ShetA2-Abemaciclib (IC50, 2 nM), and Letrozole-Ribociclib (IC50, 11 nM). Impact of dual inhibition on structure dynamics categorically demonstrates the role of catalytic amino acids (Asp341 and Ala166) that forges interactions with aromatic rings and chemical scaffolds particularly pyrido-pyrimidine substructures efficaciously uphold an active conformation. Furthermore, the role of p27 linker is emphasized and validated that modulates compact domain organization and confers enhanced structure stability thus acting as molecular effectors of dual drugs binding in solution. Additionally, local conformational changes, hydrophobic microenvironment around CBG, and polar ATP site underpin the significance of aromatic rings in ligands that serve as targets for prostate cancer. Conclusively, the ADMET properties of combination drugs, the structural dynamics of each inhibitor in its respective binding site, and molecular determinants for enhanced binding affinities provide summarized data on dual inhibition therapy that can significantly aid in designing accurate dual inhibitors.

Design, synthesis, and discovery of Eudistomin Y derivatives as lysosome-targeted antiproliferation agents

Eudistomin Y is a novel class of β-carbolines of marine origin with potential antiproliferation activity against MDA-MB-231 cells (triple-negative breast carcinoma). However, the subcellular target or the detailed mechanism against cancer cell proliferation has not yet been identified. In this study, based on its special structure, a novel series of Eudistomin Y fluorescent derivatives were designed and synthesized by enhancing the electron-donor effect of N-9 to endow it with fluorescent properties through N-alkylation. The structure–activity relationships against the proliferation of cancer cells were also analyzed. A quarter of Eudistomin Y derivatives showed much higher potency against cancer cell proliferation than the original Eudistomin Y1. Fluorescent derivative H1k with robust antiproliferative activity could arrest MDA-MB-231 cells in the G2–M phase. The subcellular localization studies of the probes, including H1k, and Eudistomin Y1 were performed in MDA-MB-231 cells, and the co-localization and competitive inhibition assays revealed their lysosome-specific localization. Moreover, H1k could dose-dependently increase the autophagy signal and downregulate the expression of cyclin-dependent kinase (CDK1) and cyclin B1 which principally regulated the G2–M transition. Furthermore, the specific autophagy inhibitor 3-methyladenine significantly inhibited the H1k-triggered antiproliferation of cancer cells and the downregulation of CDK1 and cyclin B1. Overall, the lysosome is identified as the subcellular target of Eudistomin Y for the first time, and derivative H1k showed robust antiproliferative activity against MDA-MB-231 cells by decreasing Cyclin B1–CDK1 complex via a lysosome-dependent pathway.

Cytotoxic Mechanism of Momilactones A and B against Acute Promyelocytic Leukemia and Multiple Myeloma Cell Lines.

Simple SummaryThough the anticancer potentiality of momilactones has been reported in several studies, their cytotoxic mechanism has not been comprehensively scrutinized. In this study, we investigated the cytotoxicity of momilactones A (MA) and B (MB) against acute promyelocytic leukemia (APL) HL-60 and multiple myeloma (MM) U266 cell lines. According to MTT results, MB and the mixture MAB (1:1, w/w) show a substantial inhibition on the cell viability of HL-60 and U266, with IC50 ranging from 4.49 to 5.59 µM. Besides, MB and MAB at 5 µM inhibit HL-60 cells through the regulations of relevant proteins to apoptosis-inducing factors (p-38, BCL-2, and caspase-3) and cell cycle arrest at G2 phase (p-38, CDK1, and cyclin B1). Meanwhile, these compounds enhance U266 apoptosis by altering p-38, BCL-2, and caspase-3 signaling pathways. Significantly, momilactones exhibit a minor effect on a non-cancerous cell line (MeT-5A), implying that they are promising candidates for developing novel anti-APL and anti-MM medicines.This is the first study clarifying the cytotoxic mechanism of momilactones A (MA) and B (MB) on acute promyelocytic leukemia (APL) HL-60 and multiple myeloma (MM) U266 cell lines. Via the MTT test, MB and the mixture MAB (1:1, w/w) exhibit a potent cytotoxicity on HL-60 (IC50 = 4.49 and 4.61 µM, respectively), which are close to the well-known drugs doxorubicin, all-trans retinoic acid (ATRA), and the mixture of ATRA and arsenic trioxide (ATRA/ATO) (1:1, w/w) (IC50 = 5.22, 3.99, and 3.67 µM, respectively). Meanwhile MB, MAB, and the standard suppressor doxorubicin substantially inhibit U266 (IC50 = 5.09, 5.59, and 0.24 µM, respectively). Notably, MB and MAB at 5 µM may promote HL-60 and U266 cell apoptosis by activating the phosphorylation of p-38 in the mitogen-activated protein kinase (MAPK) pathway and regulating the relevant proteins (BCL-2 and caspase-3) in the mitochondrial pathway. Besides, these compounds may induce G2 phase arrest in the HL-60 cell cycle through the activation of p-38 and disruption of CDK1 and cyclin B1 complex. Exceptionally, momilactones negligibly affect the non-cancerous cell line MeT-5A. This finding provides novel insights into the anticancer property of momilactones, which can be a premise for future studies and developments of momilactone-based anticancer medicines.

High-Resolution Profiling of Lung Adenocarcinoma Identifies Expression Subtypes with Specific Biomarkers and Clinically Relevant Vulnerabilities.

Integrative analysis of multiomic and drug dependency data uncovers robust lung adenocarcinoma expression subtypes with unique therapeutic vulnerabilities and subtype-specific biomarkers of response.

Cyclin-dependent kinase 1 depolymerizes nuclear lamin filaments by disrupting the head-to-tail interaction of the lamin central rod domain

Nuclear lamins maintain the nuclear envelope structure by forming long linear filaments via two alternating molecular arrangements of coiled-coil dimers, known as A11 and A22 binding modes. The A11 binding mode is characterized by the antiparallel interactions between coil 1b domains, whereas the A22 binding mode is facilitated by interactions between the coil 2 domains of lamin. The junction between A11- and A22-interacting dimers in the lamin tetramer produces another parallel head–tail interaction between coil 1a and the C-terminal region of coil 2, called the ACN interaction. During mitosis, phosphorylation in the lamin N-terminal head region by the cyclin-dependent kinase (CDK) complex triggers depolymerization of lamin filaments, but the associated mechanisms remain unknown at the molecular level. In this study, we revealed using the purified proteins that phosphorylation by the CDK1 complex promotes disassembly of lamin filaments by directly abolishing the ACN interaction between coil 1a and the C-terminal portion of coil 2. We further observed that this interaction was disrupted as a result of alteration of the ionic interactions between coil 1a and coil 2. Combined with molecular modeling, we propose a mechanism for CDK1-dependent disassembly of the lamin filaments. Our results will help to elucidate the cell cycle–dependent regulation of nuclear morphology at the molecular level.

Abstract 2151: Identification and proteogenomic characterization of novel lung adenocarcinoma subtypes with therapeutic relevance

Abstract Lung adenocarcinoma (LUAD) is one of the most common cancer types with various available treatment modalities. However, better biomarkers of response are still needed for further improving precision medicine. Therefore, a robust LUAD subtyping can substantially aid in determining the most effective therapies that target subtype-specific vulnerabilities. In this study, we integrated multiple datasets: (i) the full 509 LUAD patient cohort from The Cancer Genome Atlas (TCGA) project, (ii) cancer vulnerability data in LUAD cell lines from the Broad Institute’s DependencyMap, and (iii) proteomic data from the Clinical Proteomic Tumor Analysis Consortium (CPTAC) LUAD patients. Using these datasets, we identified 5 expression subtypes (S1-S5) with unique proteogenomic and dependency profiles that increased the resolution of previously defined subtypes (Proximal Inflammatory [PI]; Proximal Proliferative [PP]; and Terminal Respiratory Unit [TRU]). S4-associated cell lines exhibited specific vulnerability to CDK6 and CDK6-cyclin D3 complex gene, CCND3. S3 was characterized by dependency on CDK4, immune-related expression patterns, and altered MET signaling. Experimental validation showed that S3-associated cell lines responded to MET inhibitors, which also led to increased PD-L1 expression. Finally, we identified a small set of biomarkers for S3 and S4 that could be used in the clinic to classify patients into our therapeutically relevant subtypes. Overall, our lung adenocarcinoma expression subtypes, especially S3 that represents 20% of LUAD patients and S4 that represents 25% of LUAD patients, and their biomarkers could help identify patients likely to respond to CDK4/6, MET, or PD-L1 inhibitors, potentially improving patient outcome. Citation Format: Whijae Roh, Yifat Geffen, Mendy Miller, Shankara Anand, Jaegil Kim, David Heiman, Matthew Meyerson, Peter Laird, Andrew Cherniack, NCI CCG Tumor Molecular Pathology (TMP) Analysis Working Group, Gad Getz. Identification and proteogenomic characterization of novel lung adenocarcinoma subtypes with therapeutic relevance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2151.

Cdc6 is sequentially regulated by PP2A-Cdc55, Cdc14, and Sic1 for origin licensing in S. cerevisiae.

Cdc6, a subunit of the pre-replicative complex (pre-RC), contains multiple regulatory cyclin-dependent kinase (Cdk1) consensus sites, SP or TP motifs. In Saccharomyces cerevisiae, Cdk1 phosphorylates Cdc6-T7 to recruit Cks1, the Cdk1 phospho-adaptor in S phase, for subsequent multisite phosphorylation and protein degradation. Cdc6 accumulates in mitosis and is tightly bound by Clb2 through N-terminal phosphorylation in order to prevent premature origin licensing and degradation. It has been extensively studied how Cdc6 phosphorylation is regulated by the cyclin-Cdk1 complex. However, a detailed mechanism on how Cdc6 phosphorylation is reversed by phosphatases has not been elucidated. Here, we show that PP2ACdc55 dephosphorylates Cdc6 N-terminal sites to release Clb2. Cdc14 dephosphorylates the C-terminal phospho-degron, leading to Cdc6 stabilization in mitosis. In addition, Cdk1 inhibitor Sic1 releases Clb2·Cdk1·Cks1 from Cdc6 to load Mcm2-7 on the chromatin upon mitotic exit. Thus, pre-RC assembly and origin licensing are promoted by phosphatases through the attenuation of distinct Cdk1-dependent Cdc6 inhibitory mechanisms.

Chemical composition, anticancer activities and related mechanisms of the essential oil from Alpinia coriandriodora rhizome

Alpinia coriandriodora is widely cultivated as a medicinal and edible Zingiberaceae plant in Guangxi, China. Since essential oils from Zingiberaceae plants can be used as a potential source of anticancer drugs, this study was designed to identify the chemical composition of A. coriandriodora rhizome essential oil (EO) and firstly elucidate its anticancer activities and related mechanisms. The GC-FID/MS results indicated that the most predominant component of EO was (E)-2-decenal (56.3%). Based on the MTT results, EO exhibited comparable cytotoxicity to A549 cells and lower cytotoxicity to non-cancerous cells compared with the positive control (elemene injection). For related mechanism studies, EO inhibited the A549 cells proliferation, resulting from inducing cell cycle arrest at G1 phase via downregulation of cyclin E2-CDK2 and cyclin D3-CDK4/CDK6 complexes and upregulation of p21. Meanwhile, it induced the apoptosis through mitochondrial pathway with the successive enhancement in the Bax/Bcl-2 ratio, Δψm decline, cyt c release, activation of caspase-9 and caspase-3, and PARP cleavage. Moreover, it inhibited the migration and invasion ability of A549 cells via downregulation of MMP-2 and N-cadherin, as well as upregulation of E-cadherin. Hence, EO has outstanding anticancer properties in vitro, and this fact encourages further studies using in vivo models.

Inhibition of CDK4/6 as Therapeutic Approach for Ovarian Cancer Patients: Current Evidences and Future Perspectives.

Simple SummaryAltered regulation of the cell cycle is a hallmark of cancer. The recent clinical success of the inhibitors of CDK4 and CDK6 has convincingly demonstrated that targeting cell cycle components may represent an effective anti-cancer strategy, at least in some cancer types. However, possible applications of CDK4/6 inhibitors in patients with ovarian cancer is still under evaluation. Here, we describe the possible biological role of CDK4 and CDK6 complexes in ovarian cancer and provide the rationale for the use of CDK4/6 inhibitors in this pathology, alone or in combination with other drugs. This review, coupling basic, preclinical and clinical research studies, could be of great translational value for investigators attempting to design new clinical trials for the better management of ovarian cancer patients.Alterations in components of the cell-cycle machinery are present in essentially all tumor types. In particular, molecular alterations resulting in dysregulation of the G1 to S phase transition have been observed in almost all human tumors, including ovarian cancer. These alterations have been identified as potential therapeutic targets in several cancer types, thereby stimulating the development of small molecule inhibitors of the cyclin dependent kinases. Among these, CDK4 and CDK6 inhibitors confirmed in clinical trials that CDKs might indeed represent valid therapeutic targets in, at least some, types of cancer. CDK4 and CDK6 inhibitors are now used in clinic for the treatment of patients with estrogen receptor positive metastatic breast cancer and their clinical use is being tested in many other cancer types, alone or in combination with other agents. Here, we review the role of CDK4 and CDK6 complexes in ovarian cancer and propose the possible use of their inhibitors in the treatment of ovarian cancer patients with different types and stages of disease.

Clinical CDK4/6 inhibitors induce selective and immediate dissociation of p21 from cyclin D-CDK4 to inhibit CDK2

Since their discovery as drivers of proliferation, cyclin-dependent kinases (CDKs) have been considered therapeutic targets. Small molecule inhibitors of CDK4/6 are used and tested in clinical trials to treat multiple cancer types. Despite their clinical importance, little is known about how CDK4/6 inhibitors affect the stability of CDK4/6 complexes, which bind cyclins and inhibitory proteins such as p21. We develop an assay to monitor CDK complex stability inside the nucleus. Unexpectedly, treatment with CDK4/6 inhibitors—palbociclib, ribociclib, or abemaciclib—immediately dissociates p21 selectively from CDK4 but not CDK6 complexes. This effect mediates indirect inhibition of CDK2 activity by p21 but not p27 redistribution. Our work shows that CDK4/6 inhibitors have two roles: non-catalytic inhibition of CDK2 via p21 displacement from CDK4 complexes, and catalytic inhibition of CDK4/6 independent of p21. By broadening the non-catalytic displacement to p27 and CDK6 containing complexes, next-generation CDK4/6 inhibitors may have improved efficacy and overcome resistance mechanisms.