Cyclin-dependent Kinase Research Articles

Compromised CDK12 activity causes dependency on the high activity of O-GlcNAc transferase.

O-GlcNAc transferase (OGT) coordinates with regulators of transcription, including cyclin-dependent kinase 12 (CDK12), the major transcription elongation kinase. Here, we use inhibitor- and knockdown-based strategies to show that co-targeting of OGT and CDK12 is toxic to prostate cancer cells. OGT catalyzes all nucleocytoplasmic O-GlcNAcylation and due to its essentiality in higher eukaryotes, it is not an ideal drug target. Our glycoproteomics-data revealed that short-term CDK12 inhibition induces hyper-O-GlcNAcylation of the spliceosome-machinery in different models of prostate cancer. By integrating our glycoproteomics-, gene essentiality- and clinical-data from CDK12 mutant prostate cancer patients, we identify the non-essential serine-arginine protein kinase 1 (SRPK1) as a synthetic lethal partner with CDK12-inactivation. Both normal and cancer cells become highly sensitive against inhibitors of OGT and SRPK1 if they have lowered activity of CDK12. Inactivating mutations in CDK12 are enriched in aggressive prostate cancer, and we propose that these patients would benefit from therapy targeting the spliceosome.

LncRNA VELRP Modulates Pulmonary Arterial Smooth Muscle Cell Proliferation and Promotes Vascular Remodeling in Pulmonary Hypertension.

Pulmonary hypertension is a devastating vascular disorder characterized by extensive pulmonary vascular remodeling, ultimately leading to right ventricular failure and death. Activation of PDGF (platelet-derived growth factor) signaling promotes the hyperproliferation of pulmonary arterial smooth muscle cells (PASMCs), thus contributing to the pulmonary vascular remodeling. However, the molecular mechanisms that govern hyperproliferation of PASMCs induced by PDGF remain largely unknown, including the contribution of long noncoding RNAs (lncRNAs). In this study, we aimed to identify a novel lncRNA regulated by PDGF implicated in PASMC proliferation in pulmonary vascular remodeling. RNA-sequencing analysis was conducted to identify a novel lncRNA named vessel-enriched lncRNA regulated by PDGF-BB (VELRP). Functional investigations of VELRP were performed using knockdown and overexpression strategies along with RNA sequencing. Validation of the function and potential mechanisms of VELRP were performed through Western blot, RNA immunoprecipitation, and chromatin immunoprecipitation assays. We identified a novel vessel-enriched lncRNA with an increased response to PDGF-BB stimulus. VELRP was identified as an evolutionarily conserved RNA molecules. Modulation of VELRP in PASMCs significantly altered cell proliferation. Mechanistically, VELRP enhances trimethylation of H3K4 by interacting with WDR5 (WD repeat-containing protein 5), leading to increased expression of CDK (cyclin-dependent kinase) 1, CDK2, and CDK4 and consequent hyperproliferation of PASMCs. The pathological relevance of VELRP upregulation in pulmonary artery was confirmed using rat pulmonary hypertension models in vivo, as well as in PASMCs from patients with idiopathic pulmonary arterial hypertension patients. Specific knockdown of VELRP in smooth muscle cells using adeno-associated virus type 9 SM22α (smooth muscle protein 22α) promoter-shRNA-mediated silencing of VELRP resulted in a significant decrease in right ventricular systolic pressure and vascular remodeling in rat pulmonary hypertension model. VELRP, as an lncRNA upregulated by PDGF-BB, mediates PASMC proliferation via WDR5/CDK signaling. In vivo studies demonstrate that targeted intervention of VELRP in smooth muscle cells can prevent the development of pulmonary hypertension.

Updates in Systemic Treatment of Hormone Receptor-Positive Early-Stage Breast Cancer.

Hormone-receptor positive (HR +) and human epidermal growth factor receptor 2 (HER2) negative early breast cancer (eBC) is a heterogeneous disease with several contributing factors for increased risk of recurrence, including tumor features, individual biomarkers, and genomic risk. The current standard approach in the management of HR + /HER2neg eBC includes chemotherapy and endocrine therapy (ET), and additional therapies based on risk profile, menopausal status, and genetics are sometimes appropriate. The risk of recurrence is more pronounced in patients with high-risk eBC including large tumor size, nodal involvement, high proliferative index, and genetic predisposition. In premenopausal patients with high-risk eBC, ovarian function suppression in combination with adjuvant ET improves survival. In postmenopausal patients, extended aromatase inhibitor (AI) therapy can be considered. Recent trials have identified novel treatment approaches to reduce the risk of recurrence in high-risk HR + /HER2neg eBC including the addition of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors to adjuvant ET. For patients with germline BRCA1/BRCA2 mutations, adjuvant poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors have been shown to improve overall survival (OS). However, despite these recent advances, the risk of recurrence remains substantial, highlighting an area of unmet need. There are several ongoing clinical trials further investigating the role of CDK 4/6 inhibitors and immunotherapy in high-risk HR + /HER2neg eBC.

A new model and precious tool to study molecular mechanisms of macrophage aging.

The accumulation of senescent cells, characterized by a senescence-associated secretory phenotype (SASP), contributes to chronic inflammation and age-related diseases (ARD). During aging, macrophages can adopt a senescent-like phenotype and an altered function, which promotes senescent cell accumulation. In the context of aging and ARD, controlling the resolution of the inflammatory response and preventing chronic inflammation, especially by targeting macrophages, must be a priority. Aging being a dynamic process, we developed a model of in vitro murine peritoneal macrophage aging. Our results show that macrophages cultured for 7 or 14 days exhibit a senescence-like phenotype: proliferation decrease, the levels of cyclin-dependent kinase inhibitors p16INK4A and p21CIP1 and of pro-inflammatory SASP components (MCP-1, IL-6, IL-1β, TNF-α, and MMP-9) increase, phagocytosis capacity decline and glycolytic activity is induced. In our model, chronic treatment with CB3, a thioredoxin-1 mimetic anti-inflammatory peptide, completely prevents p21CIP1 increase and enables day 14 macrophages to maintain proliferative activity.We describe a new model of macrophage aging with a senescence-like phenotype associated with inflammatory, metabolic and functional perturbations. This model is a valuable tool for characterizing macrophage aging mechanisms and developing innovative strategies with promising therapeutical purpose in limiting inflammaging and ARD.

Discovery of novel CDK4/6 inhibitors from fungal secondary metabolites

The development of targeted therapies for breast cancer, particularly those focusing on cyclin-dependent kinases 4/6 (CDK4/6), has significantly improved patient outcomes. However, the currently approved CDK4/6 inhibitors are associated with various side effects, underscoring the need for novel compounds with enhanced efficacy and safety profiles. This study aimed to identify potential CDK4/6 inhibitors from MeFSAT, a database of fungal secondary metabolites using an in-silico screening approach. The virtual screening process incorporated drug-likeness filters, ADME and toxicity predictions, consensus molecular docking, and 200 ns molecular dynamics simulations. Out of 411 initial compounds, two molecules demonstrated favorable binding interactions and stability with the CDK4/6 protein complex. The MTT assay showed that MSID000025 had dose-dependent cytotoxicity against MCF7 breast cancer cells. This suggests that MSID000025 could be a good candidate CDK4/6 inhibitor for treating breast cancer. Our study highlights the potential of fungal secondary metabolites as a source of novel compounds for drug discovery. It provides a framework for identifying CDK4/6 inhibitors with improved therapeutic properties.

CDK12 loss drives prostate cancer progression, transcription-replication conflicts, and synthetic lethality with paralog CDK13

Biallelic loss of cyclin-dependent kinase 12 (CDK12) defines a metastatic castration-resistant prostate cancer (mCRPC) subtype. It remains unclear, however, whether CDK12 loss drives prostate cancer (PCa) development or uncovers pharmacologic vulnerabilities. Here, we show Cdk12 ablation in murine prostate epithelium is sufficient to induce preneoplastic lesions with lymphocytic infiltration. In allograft-based CRISPR screening, Cdk12 loss associates positively with Trp53 inactivation but negatively with Pten inactivation. Moreover, concurrent Cdk12/Trp53 ablation promotes proliferation of prostate-derived organoids, while Cdk12 knockout in Pten-null mice abrogates prostate tumor growth. In syngeneic systems, Cdk12/Trp53-null allografts exhibit luminal morphology and immune checkpoint blockade sensitivity. Mechanistically, Cdk12 inactivation mediates genomic instability by inducing transcription-replication conflicts. Strikingly, CDK12-mutant organoids and patient-derived xenografts are sensitive to inhibition or degradation of the paralog kinase, CDK13. We therein establish CDK12 as a bona fide tumor suppressor, mechanistically define how CDK12 inactivation causes genomic instability, and advance a therapeutic strategy for CDK12-mutant mCRPC.

Design, synthesis, and biological evaluation of novel 5,7,4′-trimethoxyflavone sulfonamide-based derivatives as highly potent inhibitors of LRPPRC/STAT3/CDK1

Leucine-rich pentatricopeptide repeat-containing protein (LRPPRC), signal transducer and activator of transcription 3 (STAT3), and cyclin-dependent kinase 1 (CDK1) are promising therapeutic targets for cancer treatment. However, there is a lack of effective inhibitors of LRPPRC, STAT3, and CDK1 in clinic. Our previous study has proved that 5,7,4′-Trimethoxyflavone (TMF) is a novel inhibitor of LRPPRC/STAT3/CDK1. However, the extraction rate of TMF from Tangerine Peel is quite low, and the doses of TMF in cells and mice are rather high. Herein, structural modifications of TMF have led to two series of TMF derivatives including sulfonamide substituted at 3′-position (7a–m) and 3′,8-position (11a–m). Among all compounds, 7e, 7k, 11e, and 11g exhibited as effective, broad-spectrum, and potent anticancer agents in vitro. Moreover, 7e, 7k, 11e, and 11g showed better antitumor effects than TMF and clinical used chemotherapy drug capecitabine in vivo with no obvious toxicity. Mechanism studies showed that 11g could bind to LRPPRC, STAT3, and CDK1 to disassociate the LRPPRC-JAK2-STAT3 and JAK2-STAT3-CDK1 complexes, resulting in suppression of JAK2/STAT3 signaling pathway. These findings suggest that 11g may serve as a leading compound for cancer therapy as a triple-target (LRPPRC, STAT3, and CDK1) inhibitor.

Novel Genes of the Male Reproductive System: Potential Roles in Male Reproduction and as Non-hormonal Male Contraceptive Targets.

The development of novel non-hormonal male contraceptives represents a pivotal frontier in reproductive health, driven by the need for safe, effective, and reversible contraceptive methods. This comprehensive review explores the genetic underpinnings of male fertility, emphasizing the crucial roles of specific genes and structural variants (SVs) identified through advanced sequencing technologies such as long-read sequencing (LRS). LRS has revolutionized the detection of structural variants and complex genomic regions, offering unprecedented precision and resolution over traditional next-generation sequencing (NGS). Key genetic targets, including those implicated in spermatogenesis and sperm motility, are highlighted, showcasing their potential as non-hormonal contraceptive targets. The review delves into the systematic identification and validation of male reproductive tract-specific genes, utilizing advanced transcriptomics and genomics studies with validation using novel knockout mouse models. We discuss the innovative application of small molecule inhibitors, developed through platforms like DNA-encoded chemistry technology (DEC-Tec), which have shown significant promise in preclinical models. Notable examples include inhibitors targeting serine/threonine kinase 33 (STK33), soluble adenylyl cyclase (sAC), cyclin-dependent kinase 2 (CDK2), and bromodomain testis associated (BRDT), each demonstrating nanomolar affinity and potential for reversible and specific inhibition of male fertility. This review also honors the contributions of Dr. David L. Garbers whose foundational work has paved the way for these advancements. The integration of genomic, proteomic, and chemical biology approaches, supported by interdisciplinary collaboration, is poised to transform male contraceptive development. Future perspectives emphasize the need for continued innovation and rigorous testing to bring these novel contraceptives from the laboratory to clinical application, promising a new era of male reproductive health management.

CDK-dependent phosphorylation regulates PNKP function in DNA replication

Okazaki fragment maturation (OFM) stands as a pivotal DNA metabolic process, crucial for genome integrity and cell viability. Dysregulation of OFM leads to DNA single-strand breaks- accumulation, which is linked to various human diseases such as cancer and neurodegenerative disorders. Recent studies have implicated LIG3-XRCC1 acting in an alternative OFM pathway to the canonical FEN1-LIG1 pathway. Here, we reveal that polynucleotide kinase-phosphatase (PNKP) is another key participant in DNA replication, akin to LIG3-XRCC1. Through functional experiments, we demonstrate PNKP's enrichment at DNA replication forks and its association with PCNA, indicating its involvement in replication processes. Cellular depletion of PNKP mirrors defects observed in OFM-related proteins, highlighting its significance in replication fork dynamics. Additionally, we identify PNKP as a substrate for cyclin-dependent kinase 1/2 (CDK1/2), which phosphorylates PNKP at multiple residues. Mutation analysis of these phosphorylation sites underscores the importance of CDK2-mediated PNKP phosphorylation in DNA replication. Our findings collectively indicate a novel role for PNKP in facilitating Okazaki fragment joining, thus shedding light on its contribution to genome stability maintenance.

Elacestrant in ER+, HER2- Metastatic Breast Cancer with ESR1-Mutated Tumors: Subgroup Analyses from the Phase III EMERALD Trial by Prior Duration of Endocrine Therapy plus CDK4/6 Inhibitor and in Clinical Subgroups.

Elacestrant significantly prolonged progression-free survival (PFS) with manageable safety versus standard-of-care (SOC) endocrine therapy (ET) in patients with estrogen receptor-positive (ER+), HER2- metastatic breast cancer and tumors harboring estrogen receptor 1 (ESR1) mutation following ET plus a cyclin-dependent kinase 4/6 inhibitor (ET+CDK4/6i). In patients with ESR1-mutated tumors, we evaluated the efficacy and safety of elacestrant versus SOC based on prior ET+CDK4/6i duration and in clinical subgroups with prior ET+CDK4/6i ≥12 months. EMERALD, an open-label phase III trial, randomly assigned patients with ER+, HER2- metastatic breast cancer who had received 1-2 prior lines of ET, mandatory CDK4/6i, and ≤1 chemotherapy to elacestrant (345 mg daily) or SOC (aromatase inhibitor or fulvestrant). PFS was assessed across subgroups in post hoc exploratory analyses without adjustment for multiple testing. In patients with ESR1-mutated tumors and prior ET+CDK4/6i ≥12 months, the median PFS for elacestrant versus SOC was 8.6 versus 1.9 months (HR, 0.41; 95% confidence interval, 0.26-0.63). In this population, the median PFS (in months) for elacestrant versus SOC was 9.1 versus 1.9 (bone metastases), 7.3 versus 1.9 (liver and/or lung metastases), 9.0 versus 1.9 (<3 metastatic sites), 10.8 versus 1.8 (≥3 metastatic sites), 5.5 versus 1.9 (PIK3 catalytic subunit α mutation), 8.6 versus 1.9 (tumor protein p53 gene mutation), 9.0 versus 1.9 (HER2-low), 9.0 versus 1.9 (ESR1D538G-mutated tumors), and 9.0 versus 1.9 (ESR1Y537S/N-mutated tumors). Subgroup safety was consistent with the overall population. The duration of prior ET+CDK4/6i ≥12 months in metastatic breast cancer was associated with a clinically meaningful improvement in PFS for elacestrant compared with SOC and was consistent across all subgroups evaluated in patients with ER+, HER2-, ESR1-mutated tumors.

Adaptive learning to address gaps in metastatic breast cancer treatment with CDK 4/6 inhibitors.

92 Background: To address identified gaps in knowledge and confidence of US-based healthcare professionals (HCPs) when using cyclin-dependent kinase 4/6 inhibitors (CDK 4/6i) to treat metastatic breast cancer (mBC), an adaptive learning program (ALP) was deployed to review guideline recommendations and evidence from randomized clinical trials (RCTs) and real-world data (RWD). Methods: The ALP consisted of reading materials (guideline excerpts, RCTs, RWD, cases) with a virtual tutor that taught. The ALP continued to review necessary content until responders were both correct and confident (conscious competence). Impact on learning was interpreted as greater for learning objectives with the lowest accuracy score (% of correct responses) and higher distance to 100% conscious competency at baseline. Immediately post-ALP, satisfaction, perceived impact on knowledge, confidence and intent to change practice were assessed quantitatively and qualitatively. ANOVA compared continuous measures by profession. Results: Participants (n=261) were physicians (MD, 17%), advanced practice practitioners (APP, 20%), registered nurses (RN, 49%), pharmacists (11%), and other (3%). Mean completion time was 44 minutes and learners’ proficiency shifted +64% towards conscious competency. The learning objectives most impacted by the education are shown (Table). Learners most satisfied with the ALP (47% with 9-10 on a 10-point satisfaction scale) appreciated the challenge and reported positive impact on their knowledge and confidence, resulting in intent to change their patient-communication, clinical decisions and interprofessional collaboration when using CDK4/6i. Conclusions: This ALP initiative addressed the educational gaps of US HCPs regarding CDK4/6i in HR+/HER2- mBC by challenging participants to re-consider their knowledge and confidence until conscious competency was demonstrated. Engaged learners found the activity impactful and reported intent to change practice. Future studies should seek to address attrition challenges and assess long term impacts of such programs. Top five learning objectives with lowest-ranking accuracy, by profession. Learning Objectives (LOs) Most Impacted Initial Scores by Profession Final Score ALL MD APP RN PharmD Other Identify appropriate CDK4/6i treatment options for a premenopausal woman with newly diagnosed HR+/HER2- mBC 54 57 53 53 62 52 100 Match RWD sources with their characteristics 56 55 60 55 61 41 100 Interpret results from the landmark CDK4/6i RCTs 58 62 61 53 64 56 100 Interpret RWE related to the use of CDK4/6i in patients who are underrepresented in RCTs* 62 62 63 58 74 65 100 Identify the latest updates from CDK4/6i RCTs 62 60 63 61 62 82 100 Average accuracy score for all 24 LOs 71 72 73 69 74 64 100 *Significantly different between professions (p&lt;0.05; one-way ANOVA).

An overview of the latest outlook of sulfamate derivatives as anticancer candidates (2020-2024).

Considering the emergence of new anticancer drugs, in this review we emphasized and highlighted the recent reports and advances related to sulfamate-incorporating compounds with potential anticancer activity during the last 5 years (2020-2024). Additionally, we discussed their structure-activity relationship, clarifying their potent bioactivity as anticancer agents. Sulfamate derivatives hold promise as effective therapeutic candidates against cancer. By targeting biological targets associated with the development of cancer, such as steroid sulfatases (STS), carbonic anhydrases (CAs), microtubules, NEDD8-activating enzyme, small ubiquitin-like modifiers(SUMO)-activating enzyme (SAE), cyclin-dependent kinases (CDKs), breast cancer susceptibility gene 1 (BRCA1), and so on, this can furnish small molecules as anticancer lead candidates serving the drug discovery field. For example, compound 2, an STS inhibitor, demonstrated superior activity compared to its reference, irosustat, by fivefold. In addition, compound 21, an SAE, is under phase I clinical trials. Continued research into sulfamate derivatives holds potential for the development of novel therapeutic agents targeting various diseases.

A genome-wide CRISPR/Cas9 knockout screen identifies SEMA3F gene for resistanceto cyclin-dependent kinase 4 and 6 inhibitors in breast cancer.

Palbociclib is a cell-cycle targeted small molecule agent used as one of the standards of care in combination with endocrine therapy for patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Although several gene alterations such as loss of Rb gene and amplification of p16 gene are known to be conventional resistance mechanisms to cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, the comprehensive landscape of resistance is not yet fully elucidated. The purpose of this study is to identify the novel resistant genes to the CDK4/6 inhibitors in HR-positive HER2-negative breast cancer. The wholegenome knockout screen using CRISPR/Cas9 genome editing was conducted in MCF7 to identify resistant genes to palbociclib. The candidate genes for resistance were selected by NGS analysis and GSEA analysis and validated by cell viability assay and mouse xenograft models. We identified eight genes including RET, TIRAP, GNRH1, SEMA3F, SEMA5A, GATA4, NOD1, SSTR1 as candidate genes from the wholegenome knockout screen. Among those, knockdown of SEMA3F by siRNA significantly and consistently increased the cell viability in the presence of CDK4/6 inhibitors in vitro and in vivo. Furthermore, the level of p-Rb was maintained in the palbociclibtreated SEMA3F-downregulated cells, indicating that the resistance is driven by increased activity of cyclin kinases. Our observation provided the first evidence of SEMA3F as a regulator of sensitivity to CDK4/6 inhibitors in breast cancer. The detailed mechanisms of resistance deserve further functional studies to develop the better strategy to overcome resistance in CDK4/6 inhibitors.

Realizing the scope of venous and arterial thrombosis in cyclin-dependent kinase 4/6 inhibitors in hormone positive breast cancer

Realizing the scope of venous and arterial thrombosis in cyclin-dependent kinase 4/6 inhibitors in hormone positive breast cancer

Implementing a drug interaction protocol for oral systemic anti-cancer therapy with focus on CDK4/6 inhibitors.

302 Background: Oral anti-cancer therapies (OACTs) are being increasingly used. Despite their convenience, OACTs introduce challenges with adherence, prescribing errors, and high incidence of drug-drug interactions (DDIs). Currently, there are limited guidelines for DDI checking. Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have revolutionized the management of metastatic ER+/HER2- breast cancer. While an overall survival benefit has been demonstrated with Ribociclib, its use can be problematic due to frequent DDIs and the risk of QTc prolongation. DDIs are routinely checked in our center with two interaction checkers, but they are not always documented due to a lack of a standardized protocol. This study aims to evaluate current DDI checking practices, identify common DDIs, and implement a systematic DDI protocol. Methods: A retrospective review was conducted on patients (pts) prescribed CDK4/6i in our center from Jan 2023 to Apr 2024. Data on pt demographics, treatment, DDI documentation, toxicity, and survival were collected. Retrospective DDI checks using Lexi-Interact and Drugs.com were performed. Results: A total of 65 pts were included, with 38 on Ribociclib and 27 on Palbociclib. The median follow-up was 11.6 months (range: 1-71). The median age of pts on Ribociclib was 54 (range: 35-77), compared to 61 (range: 44-82) on Palbociclib. The median number of medications was three with Ribociclib and five with Palbociclib. Seven pts (26%) were prescribed Palbociclib due to contraindications to Ribociclib, including cardiac disease (n=2), QTc-prolonging medications (n=4), and advanced age (n=1). DDI checks were documented in 46% of Ribociclib and 14% of Palbociclib pts (p=0.0063). There was a weak negative correlation between DDI documentation and toxicity, stronger in the Palbociclib arm (-0.079 for Ribociclib vs. -0.335 for Palbociclib). Retrospective checks revealed DDIs in 50% of Ribociclib and 52% of Palbociclib pts. Major DDIs were identified in 21% of Ribociclib and 7% of Palbociclib pts (p=0.133). Common major DDIs involved opioids and QTc-prolonging medications, most frequently antidepressants. Grade ≥3 toxicity occurred in 49% of Ribociclib vs. 64% of Palbociclib pts (p=0.21). Ribociclib caused more rash, liver toxicity, and diarrhea, while Palbociclib had significantly more grade ≥3 neutropenia (48% vs. 21%, p=0.042). No QTc prolongation was observed. Dose reductions were more common with Palbociclib (48% vs. 32%, p=0.27). There was no significant difference in survival data. Conclusions: Our findings highlight the importance of systematic DDI checks in pts receiving OACTs. Implementing a standardized protocol could reduce adverse interactions and improve pt outcomes. Further studies are needed to validate these findings and develop DDI guidelines. A standardized DDI protocol has now been developed for our center, with plans to re-audit after implementation.

Palbociclib in Patients With Head and Neck Cancer and Other Tumors With CDKN2A Alterations: Results From the Targeted Agent and Profiling Utilization Registry Study.

Targeted Agent and Profiling Utilization Registry is a phase II basket trial evaluating the antitumor activity of commercially available targeted agents in patients with advanced cancer and targetable genomic alterations. Two cohorts of patients with cyclin-dependent kinase inhibitor 2A (CDKN2A)-mutated tumors treated with palbociclib are reported: one with head and neck cancer (HNC) with both squamous and nonsquamous cell histologies, and one with histology-pooled (HP) cancers. Eligible patients had measurable disease, Eastern Cooperative Oncology Group performance status 0-2, adequate organ function, and no standard treatment options. The primary end point was disease control (DC), defined as objective response (OR) or stable disease (SD) of at least 16+ weeks duration. For the HNC cohort, Simon's two-stage design with a null DC rate of 15% versus 35% (power = 0.85; α = .10) was used. For the HP cohort, the null hypothesis of a DC rate of 15% was rejected if the lower limit of a one-sided 90% CI was >15%. Secondary end points included OR, safety, progression-free survival, overall survival, duration of response, and duration of SD. Seventy patients with HNC (N = 28) or HP cancers (N = 42) were treated with palbociclib. For the HNC cohort, DC and OR rates were 40% (one-sided 90% CI, 27 to 100) and 4% (95% CI, <1 to 18), respectively. The null hypothesis was rejected (P = .002). For the HP cohort, DC and OR rates were 13% (one-sided 90% CI, 6 to 100) and 5% (95% CI, <1 to 17), respectively. The null hypothesis was not rejected. Thirty-one of 70 patients experienced treatment-related grade 3 to 4 adverse events (AEs) or serious AEs, the most common including neutropenia, thrombocytopenia, and leukopenia. Palbociclib met prespecified criteria to declare a signal of activity in patients with HNC with CDKN2A alterations, but not in the HP cohort.

413 (PB401): Comprehensive characterization of CDK inhibitors using a complete panel of all 20 human cyclin-dependent kinases

413 (PB401): Comprehensive characterization of CDK inhibitors using a complete panel of all 20 human cyclin-dependent kinases

Neoadjuvant letrozole and palbociclib in patients with HR-positive/HER2-negative early breast cancer and Oncotype DX Recurrence Score ≥18: DxCARTES study

The effect of the addition of cyclin-dependent kinases 4 and 6 inhibitors to endocrine therapy in terms of molecular downstaging remains undetermined. Switching from a high-risk to a low risk Recurrence Score (RS) group could provide useful information to identify patients who might not require chemotherapy. The purpose of this study was to assess the biological and clinical activity of letrozole plus palbociclib as neoadjuvant treatment for patients with hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative early breast cancer with an initial Oncotype DX RS ≥18. Participants were women aged ≥18 years with HR-positive/HER2-negative, Ki67 ≥ 20%, stage II-IIIB early breast cancer with a baseline RS ≥18. Eligible patients with a pretreatment RS 18-25 (cohort A) and 26-100 (cohort B) received six 28-day cycles of letrozole (2.5 mg per day; plus goserelin if pre- or perimenopausal) plus palbociclib (125 mg per day; 3/1 schedule) before surgery. The primary endpoint for both cohorts was the proportion of patients who achieved an RS ≤25 at surgery or a pathological complete response (pCR). A total of 67 patients were enrolled, among which 65 were assessable for the primary endpoint (32 patients in cohort A and 33 in cohort B). At surgery, 22 (68.8%) patients in cohort A and 18 (54.5%) patients in cohort B had an RS ≤25 or a pCR [only 1 (3.0%) patient in cohort B], meeting the primary endpoint in cohort B (P < 0.01), but not in cohort A (P= 0.98). No new safety signals were identified. The efficacy of neoadjuvant treatment with letrozole plus palbociclib does not seem to depend on pretreatment RS for patients with RS ≥18. However, around half of patients with HR-positive/HER2-negative early breast cancer with an RS 26-100 at baseline achieved molecular downstaging with this regimen.

Fasting-mimicking diet potentiates anti-tumor effects of CDK4/6 inhibitors against breast cancer by suppressing NRAS- and IGF1-mediated mTORC1 signaling

AimsAcquired resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) frequently emerges, and CDK4/6i-containing therapies in triple-negative breast cancer (TNBC) remain to be determined. MethodsRNA-sequencing, cell viability analysis, immunoblotting, siRNA transfection et al. were used to investigate and verify the resistance mechanism. BALB/c nude mice xenograft models and spontaneous MMTV-PyMT models were used to explore in vivo efficacy. ResultsThe mTOR pathway was activated in acquired CDK4/6i-resistant cells and inhibition of mTORC1 restored the sensitivity. While fasting-mimicking diet (FMD) enhances the activity of anticancer agents by inhibiting the mTORC1 signaling, we assessed FMD and found that FMD restored the sensitivity of CDK4/6i-resistant cells to abemaciclib and potentiated the anti-tumor activity of CDK4/6i in TNBC. The anti-tumor effects of FMD and/or CDK4/6i were accompanied by the downregulation of S6 phosphorylation. FMD cooperated with CDK4/6i to suppress the levels of IGF1 and RAS. The combination of FMD and abemaciclib also led to a potent inhibition of tumor growth in spontaneous transgenic MMTV-PyMT mouse models. ConclusionsOur data demonstrate that FMD overcomes resistance and potentiates the anti-tumor effect of CDK4/6i by inhibiting mTORC1 signaling via lowering the levels of IGF1 and RAS, providing the rationale for clinical investigation of a potential FMD-CDK4/6i strategy in breast cancer.

Spatiotemporal control of neutrophil fate to tune inflammation and repair for myocardial infarction therapy

Neutrophils are critical mediators of both the initiation and resolution of inflammation after myocardial infarction (MI). Overexuberant neutrophil signaling after MI exacerbates cardiomyocyte apoptosis and cardiac remodeling while neutrophil apoptosis at the injury site promotes macrophage polarization toward a pro-resolving phenotype. Here, we describe a nanoparticle that provides spatiotemporal control over neutrophil fate to both stymie MI pathogenesis and promote healing. Intravenous injection of roscovitine/catalase-loaded poly(lactic-co-glycolic acid) nanoparticles after MI leads to nanoparticle uptake by circulating neutrophils migrating to the infarcted heart. Activated neutrophils at the infarcted heart generate reactive oxygen species, triggering intracellular release of roscovitine, a cyclin-dependent kinase inhibitor, from the nanoparticles, thereby inducing neutrophil apoptosis. Timely apoptosis of activated neutrophils at the infarcted heart limits neutrophil-driven inflammation, promotes macrophage polarization toward a pro-resolving phenotype, and preserves heart function. Modulating neutrophil fate to tune both inflammatory and reparatory processes may be an effective strategy to treat MI.