Cyclin-dependent Kinase Inhibitor Research Articles

Proapoptotic role of CDK1 in overcoming paclitaxel resistance in ovarian cancer cells in response to combined treatment with paclitaxel and duloxetine

BackgroundPaclitaxel resistance and recurrence are major obstacles in ovarian cancer, which is the leading cause of death among gynecologic cancers. During cancer cell progression, cyclin-dependent kinase 1 (CDK1) drives cells through the G2 phase and into mitosis. In this study, we demonstrated that CDK1 played a crucial role in switching paclitaxel-resistant ovarian cancer cells from mitotic arrest to apoptosis following combined treatment with paclitaxel and duloxetine, an antidepressant known as a serotonin-norepinephrine reuptake inhibitor (SNRI).MethodsCell viability was assessed by MTT assay. Apoptotic cell death and mitochondrial membrane potential (MMP) were detected by flow cytometry. Protein expression levels were explored using western blotting. Mitochondrial and cytosolic fractionation were performed to determine the mitochondrial localization of proteins. Immunofluorescence was used to detect protein expression levels and localization.ResultsCombined treatment with paclitaxel and duloxetine induced apoptotic cell death in paclitaxel-resistant ovarian cancer cells. We suggested that combined treatment of these drugs induced CDK1 activation and increased mitochondrial localization of activated CDK1, which caused phosphorylation of the antiapoptotic Bcl-2 and Bcl-xL proteins. Selective CDK1 inhibitors blocked Bcl-2 and Bcl-xL phosphorylation induced by paclitaxel and duloxetine, and strongly suppressed apoptotic cell death. Furthermore, we demonstrated that S6K is a potential upstream mediator of the proapoptotic activation of CDK1.ConclusionTaken together, switching CDK1 to a proapoptotic role through the combination of paclitaxel and duloxetine could overcome paclitaxel resistance in ovarian cancer cells, providing promising therapeutic strategies for treating paclitaxel-resistant ovarian cancer.

Potential Role of Bioactive Compounds of Purple Corn as Breast Cancer Drug Candidates Through Inhibition of Cyclin-Dependent Protein Kinase 6 (Cdk6): An In-Silico Approach

Cancer is characterized by disorderly cell proliferation. Upregulation and activation of the Cyclin-Dependent Protein Kinase 6 (CDK6) signalling pathway can induce uncontrolled proliferation of breast cancer cells. Therefore, inhibition of CDK6 persists to be developed as a target for the design and development of potential drugs to treat breast cancer. This study aims to predict the biofunction of anthocyanin compounds from purple corn extract as Cyclin- Dependent Protein Kinase 6 (CDK6) inhibitors in silico. The research methods used include data mining, ligand and receptor preparation, molecular docking, docking visualization, and data analysis. Our results show that six compounds of purple corn extract (cyanidin, cyanidin 3-glucoside, pelargonidin-3-glucoside, pelargonidin, peonidin, and peonidin-3-glucoside) can bind CDK6 at the C-terminal and N-terminal domains. The binding pattern indicated that cyanidin, cyanidin 3-glucoside, pelargonidin-3-glucoside, pelargonidin, peonidin, and peonidin-3-glucoside bind to the identical site CDK6 residues as Palbociclib (control). This finding indicated that compounds from purple corn are most likely competitive inhibitors of CDK6. Peonidin-3-glucoside showed the lowest binding energy of -282.5 kcal/mol, close to palbociclib (-329.4 kcal/mol).

Clinical characteristics and prognostic analysis of CDKN2A/2B gene in pediatric acute lymphoblastic leukemia: a retrospective case-control study

ABSTRACT In this retrospective case-control study involving 424 pediatric patients diagnosed with Pediatric Acute Lymphoblastic Leukemia (ALL), the investigation focused on analyzing the clinical characteristics and prognosis associated with the Cyclin-dependent kinase inhibitor 2A/2B (CDKN2A/2B) gene. Treatment and evaluation followed the South China Children's Leukemia Group-ALL-2016 protocol (SCCLG-ALL-2016). Among the cohort, 92 patients (21.7%) exhibited CDKN2A/2B gene deletions, with 11.1% homozygous and 10.6% heterozygous deletions. Notably, ALL patients that do have CDKN2A/2B gene deletions tended to present at an older age (P = 0.001), demonstrate hepatosplenomegaly on palpation (P < 0.001), and exhibit a higher incidence of Central nervous system leukemia (CNSL) (P = 0.037) and T-ALL (P = 0.007). A significant correlation was observed between ALL that does have CDKN2A/2B gene deletions and ETV6::RUNX1-positive (8.7% vs. 19.3%, P = 0.017) and IKZF1 gene deletions (20.7% vs. 8.4%, P = 0.001). Survival analysis of 392 patients revealed no significant differences in 5-year relapse, Overall survival (OS), or Event-free survival (EFS) between ALL that does/ does not have CDKN2A/2B gene deletions. Subgroup analysis highlighted poorer prognosis among hepatosplenomegaly patients in the CDKN2A/2B gene deletion group, with a 5-year EFS of 81.8%, 95%CI (0.695–0.963), P = 0.05. Hepatosplenomegaly emerged as the most significant prognostic factor for EFS [HR = 2.306, 95%CI (1.192–4.461), P = 0.013]. Cox regression analyses identified covariates influencing prognosis, ALL with the CDKN2A/2B gene showing no significant impact on outcomes. In conclusion, while ALL that does have CDKN2A/2B gene deletions is associated with certain clinical characteristics and genetic aberrations, they did not significantly impact OS or EFS. Furthermore, subgroup analysis revealed a potential prognostic role of ALL that does have CDKN2A/2B deletions presenting with hepatosplenomegaly on palpation, emphasizing the importance of comprehensive risk stratification in treatment decision-making for this subgroup.

Cyclin-dependent kinase inhibitor p18 regulates lineage transitions of excitatory neurons, astrocytes, and interneurons in the mouse cortex.

Neural stem cells (NSCs) can give rise to both neurons and glia, but the regulatory mechanisms governing their differentiation transitions remain incompletely understood. Here, we address the role of cyclin-dependent kinase inhibitors (CDKIs) in the later stages of dorsal cortical development. We find that the CDKIs p18 and p27 are upregulated at the onset of astrocyte generation. Acute manipulation of p18 and p27 levels shows that CDKIs modulate lineage switching between upper-layer neurons and astrocytes at the transitional stage. We generate a conditional knock-in mouse model to induce p18 in NSCs. The transcriptomic deconvolution of microdissected tissue reveals that increased levels of p18 promote glial cell development and activate Delta-Notch signaling. Furthermore, we show that p18 upregulates the homeobox transcription factor Dlx2 to subsequently induce the differentiation of olfactory bulb interneurons while reducing the numbers of upper-layer neurons and astrocytes at the perinatal stage. Clonal analysis using transposon-based reporters reveals that the transition from the astrocyte to the interneuron lineage is potentiated by p18 at the single-cell level. In sum, our study reports a function of p18 in determining the developmental boundaries among different cellular lineages arising sequentially from NSCs in the dorsal cortex.

Interfacial cfDNA Enrichment and Amplification with On-Chip Thermoplasmonics for Highly Sensitive Cancerous Liquid Biopsy.

Tumor-derived cell-free DNA (cfDNA) has been exploited as an effective liquid biopsy biomarker for early cancer diagnosis. However, the fragmented and low-abundance nature in circulating blood pose challenges for highly sensitive cfDNA quantification. Herein, a multifunctional plasmonic biosensor termed Interfacial cfDNA Enrichment, Amplification and Sensing with on-chip Thermoplasmonics (INEAST) is developed for cfDNA-based liquid biopsy and lung cancer diagnosis. The INEAST biosensor achieved in situ thermoregulation and label-free cfDNA biosensing by simultaneously harnessing interfacial thermoplasmonics and localized surface plasmon resonance. Typical cfDNA biomarkers, including epidermal growth factor receptor (EGFR), tumor protein 53 (TP53), phosphatase and tensin homologue deleted on chromosome 10 (PTEN), and cyclin-dependent kinase inhibitor (CDKN2A), are quantified with detection limits down to femtomolar-level. Through further validation using blood samples from lung cancer patients, the proposed INEAST bioassays demonstrated superior reliability for lung cancer screening, particularly when combined with clinically available tumor-protein metrics. This study demonstrated that the INEAST biosensor enables rapid and sensitive cfDNA quantification, yielding a promising and compatible liquid biopsy for early-stage lung cancer diagnosis.

FN-1501 Inhibits Diffuse Large B-Cell Lymphoma Tumor Growth by Inducing Cell Cycle Arrest and Apoptosis.

Due to its high degree of aggressiveness, diffuse large B-cell lymphoma (DLBCL) presents a treatment challenge because 30% to 50% of patients experience resistance or relapse following standard chemotherapy. FN-1501 is an effective inhibitor of cyclin-dependent kinases and Fms-like receptor tyrosine kinase 3. This study aimed to examine the anti-tumor impact of FN-1501 on DLBCL and clarify its molecular mechanism. This study used the cell counting kit-8 assay to evaluate cell proliferation, along with western blotting and flow cytometry to analyze cell cycle progression and apoptosis influenced by FN-1501 in vitro. Afterward, the effectiveness of FN-1501 was evaluated in vivo utilizing the xenograft tumor model. In addition, we identified the potential signaling pathways and performed rescue studies using western blotting and flow cytometry. We found that FN-1501 inhibited cell proliferation and induced cell cycle arrest and apoptosis in DLBCL cells in vitro. Its anti-proliferative effects were shown to be time- and dose-dependent. The effect on cell cycle progression resulted in G1/S phase arrest, and the apoptosis induction was found to be caspase-dependent. FN-1501 treatment also reduced tumor volumes and weights and was associated with a prolonged progressionfree survival in vivo. Mechanistically, the MAPK and PI3K/AKT/mTOR pathways were significantly inhibited by FN-1501. Additional pathway inhibitors examination reinforced that FN-1501 may regulate cell cycle arrest and apoptosis through these pathways. FN-1501 shows promising anti-tumor activity against DLBCL in vivo and in vitro, suggesting its potential as a new therapeutic option for patients with refractory or relapsed DLBCL.

Associations of the Expression Levels and Risk Variants of CDKN2B-AS1 Long Noncoding RNA With the Susceptibility and Progression of Prostate Cancer.

Genetic variants of deregulated long noncoding RNAs (lncRNAs) have been implicated in tumorigenesis, cancer progression and cancer recurrence. Single-nucleotide polymorphisms (SNPs) of the lncRNA cyclin-dependent kinase inhibitor 2B antisense RNA 1 (CDKN2B-AS1) have been associated with the risk and progression of various cancers; however, their role in prostate cancer (PCa) remains underexplored. In this case-control study, we investigated the associations of CDKN2B-AS1 expression levels and variants with PCa risk and progression. For this, five SNPs of CDKN2B-AS1-rs564398, rs1333048, rs1537373, rs2151280 and rs8181047-were genotyped using a TaqMan allelic discrimination assay; data were collected from 695 patients with PCa and 695 healthy controls. Our findings revealed that, under a dominant model, patients with PCa carrying at least one minor C allele of rs1333048 exhibited an increased risk of developing tumours with high Gleason grades; this risk was particularly high in patients without biochemical recurrence. Data from the Genotype-Tissue Expression database indicated upregulated CDKN2B-AS1 expression in the prostates of individuals carrying the polymorphic C allele of rs1333048. Genotype screening of rs1333048 in PCa cell lines showed that cells with at least one minor C allele had higher CDKN2B-AS1 levels than those with the AA genotype. Furthermore, data from The Cancer Genome Atlas indicated that higher CDKN2B-AS1 levels in PCa tissues were correlated with larger tumour sizes (T3 + T4), more lymph node metastasis (N1), higher Gleason scores and shorter progression-free survival. In conclusion, the polymorphic variants of CDKN2B-AS1 at rs1333048 may modulate CDKN2B-AS1 expression, thus accelerating PCa progression.

Retinoic acid inhibition of cell proliferation via activation of CDKN1B signaling in the forebrain and spinal cord during mouse embryonic development

BackgroundThe active metabolite of vitamin A (retinol) is retinoic acid (RA). RA is essential for developing several organs as a signaling molecule that is tightly regulated during embryogenesis. We explored the teratogenic effects of RA on forebrain and spinal cord development modified by cyclin-dependent kinase inhibitor 1B (CDKN1B), as the mechanism underlying RA's teratogenic impacts requires further investigation. The study involved four groups of pregnant mice: the negative control group, the positive control group treated with dimethyl sulfoxide (DMSO) diluted in sunflower oil, the RA-treated group receiving a low dosage (5 mg/kg), and the RA-treated group receiving a high dosage (10 mg/kg). The treatment groups received daily intraperitoneal RA dissolved in DMSO and diluted with sunflower oil on gestational days 10.5, 11.5, and 12.5. On day 13.5 of pregnancy, the pregnant mice were euthanized by cervical dislocation, and immunohistochemical analyses of brain and spinal cord tissues were performed.ResultsMorphologically, we observed a decrease in the number of implantation sites and the presence of hematomas in several uterus areas in the high-dose RA (10 mg/kg) group. Additionally, RA was shown to cause adverse changes in uterine weight and length. RA treatment indicated elevated levels of CDKN1B expression in spinal cord development, the diencephalon, and the telencephalon.ConclusionOur findings demonstrated that by activating CDKN1B as an RA target gene for cell cycle arrest, an excess of RA during brain development in mouse embryos can induce cell undifferentiation during development.

Flavopiridol: a promising cyclin-dependent kinase inhibitor in cancer treatment.

Flavopiridol, a synthetic flavonoid derived from rohitukine, stands out as a powerful cyclin-dependent kinase (CDK) inhibitor with significant anticancer properties. Its action mechanisms involve inducing cell cycle arrest, triggering apoptosis, and inhibiting transcription across various cancer types. Despite these promising effects, flavopiridol's clinical use has been hampered by issues related to toxicity and drug resistance. This study aims to comprehensively review flavopiridol's mechanisms of action, structure-activity relationships, synthetic derivatives, pharmacokinetics, and its potential role in clinical applications, with a focus on how combination therapies can enhance its efficacy and address resistance challenges in cancer treatment. A thorough analysis of key studies was performed, examining flavopiridol's anticancer properties, emphasizing its structure-activity relationships, synthetic modifications, and clinical outcomes. The anticancer effects of flavopiridol are primarily driven by its inhibition of CDKs, induction of apoptosis, promotion of oxidative stress, and antiangiogenic activity. Modifications in its chemical structure, especially in the D ring, have shown a significant impact on its CDK inhibitory potency. Several synthetic derivatives have also demonstrated enhanced anticancer activity. While preclinical models highlight flavopiridol's potential in treating cancers such as leukemia and solid tumors, clinical trials have brought attention to its limitations, particularly regarding toxicity and resistance. However, flavopiridol remains a promising candidate for cancer therapy, especially when used in combination with other treatments. Future research efforts should focus on refining its therapeutic profile, minimizing toxicity, and investigating synergistic treatment combinations, including those with immunotherapy. Understanding the mechanisms of resistance and discovering predictive biomarkers will be crucial for its effective integration into clinical practice.

Discovery of novel CDK2 inhibitors for cancer treatment: integrating ligand-based pharmacophore modelling, molecular docking, DFT, ADMET, and molecular dynamics simulation studies

BackgroundThe global landscape of public health faces significant challenges attributed to the prevalence of cancer and the emergence of treatment resistance. This study addresses these challenges by focusing on Cyclin-dependent Kinase 2 (CDK2) and employing a systematic computational approach for the discovery of novel cancer therapeutics.ResultsInitial ligand-based pharmacophore modelling, utilizing a training set of five reported CDK2 inhibitors, yielded a robust model characterized by Aro|Hyd| and |Acc|Don| features. Screening this validated model against the ZINC database identified 1881 hits, which were further subjected to molecular docking studies. The top 10 compounds (Z1–Z10) selected from the docking studies underwent Pharmacokinetic parameters Absorption, Distribution, Metabolism, Excretion and Toxicity profiling, Density Functional Theory (DFT) studies and the top two went for 100ns molecular dynamics (MD) simulations by comparing them with the standard Roscovitine. Compounds Z1 and Z2 emerged as the most promising, with docking scores of − 8.05 kcal/mol and − 8.02 kcal/mol, respectively. DFT analysis of the top 10 compounds revealed minimal variations in highest occupied molecular orbital–lowest unoccupied molecular orbital energy gaps, indicating consistent electronic stability and reactivity across the candidates. MD simulations of Z1 and Z2 confirmed their stable interactions with CDK2, with root mean square deviation (RMSD) values ranging from 1.4 to 2.5 Å for Z1 and 1.5 to 2.4 Å for Z2.ConclusionThe current research identified compounds Z1 and Z2, which demonstrated significant potential as potent CDK2 inhibitors for cancer therapy, providing valuable insights into the development of more effective CDK2 inhibitors and addressing the critical need for innovative therapeutic strategies in cancer treatment.Graphical abstract

Decreased mitochondrial transcription factor A and mitochondrial DNA copy number promote cyclin-dependent kinase inhibitor 1A expression and reduce tumorigenic properties of colorectal cancer cells

PurposeColorectal cancer is one of the most common and deadliest cancer types worldwide. In the last years, changes in the mitochondrial DNA (mtDNA) copy number have been described to correlate with the prognostic outcome for colorectal cancer patients by impacting different tumorigenic properties. One key regulator of mtDNA is the mitochondrial transcription factor A (TFAM) that acts as a limiting factor of mtDNA copy number. Here, we investigated the effect of TFAM deficiency on mtDNA and tumorigenic properties in the human colorectal cancer cell line SW480.MethodsTFAM expression was stably downregulated in the colorectal cancer cell line SW480 using the CRISPR-Cas9 approach. To dissect the molecular alterations induced by deletion of TFAM, RNA sequencing and gene set enrichment analysis was performed on TFAM-wild-type and TFAM-deficient SW480 cells. Functional consequences of TFAM downregulation were assessed in cellular assays.ResultsWe showed that TFAM deficiency leads to decreased mtDNA copy number and reduced expression of mtDNA-encoded genes. TFAM-deficient cells also revealed higher activity of senescence-associated β-galactosidase and decreased cell growth parameters. Moreover, RNA sequencing showed that the expression of cyclin dependent kinase inhibitor 1A (CDKN1A/p21) is significantly increased in TFAM-deficient cells.ConclusionOur results suggest that TFAM-induced changes of the mitochondrial genome lead to upregulated CDKN1A/p21 expression in colorectal cancer cells identifying p21 as a new possible linker between mitochondria and nucleus.

Zuogui pills ameliorate chemotherapy-induced ovarian aging by improving stemness, regulating cell cycle and reducing apoptosis of oogonial stem cells via the Notch1/Nrf2 pathway

Ethnopharmacological relevanceZuogui Pills (ZGP) is a classic traditional Chinese herbal formula originating from the Ming Dynasty. It has been widely used in the treatment of kidney deficiency-related diseases, including ovarian aging. Aim of the studyTo investigate the effects and potential mechanisms of ZGP on ovarian aging induced by the chemotherapeutic agent cyclophosphamide (CTX), as well as its impact on the therapeutic target, oogonial stem cells (OSCs), involving the Notch1/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. Materials and methodsThis study utilized High-Performance Liquid Chromatography (HPLC) to analyze the active components of Zuogui Pills (ZGP). In vivo experiments involved the establishment of an ovarian aging model in female rats through intraperitoneal injection of CTX, followed by an 8-week treatment with ZGP and dehydroepiandrosterone (DHEA). The Notch pathway inhibitor DAPT was administered via intraperitoneal injection, followed by ZGP intervention to validate its therapeutic effects. Transcriptomic sequencing was used to analyze the differential genes before and after ZGP treatment of CTX-induced ovarian aging, and KEGG and GO analyses were applied to assess the changes in relevant signaling pathways and biological processes. In vitro experiments included the extraction, separation, and purification of ovarian germ stem cells, followed by transfection with a Notch1 overexpression plasmid. The CTX active component 4-Hydroxycyclophosphamide (4HC) was used for model intervention, and ZGP, DHEA-containing serum, and DAPT were applied to intervene with the oogonial stem cells. The effects of CTX modeling, the therapeutic efficacy of ZGP, and the general condition of the rats were observed. H&E staining was employed to assess ovarian morphology and follicle counting at various stages. Serum hormone levels were measured using ELISA, while qPCR, Western blot, flow cytometry, immunofluorescence, and IHC were utilized to analyze the expression of the Notch1/Nrf2 pathway, cell cycle proteins, and stemness-related indicators. Flow cytometry, TUNEL fluorescence, and CCK8 assays were conducted to evaluate changes in cell cycle composition, apoptosis, and proliferation. Finally, ChIP-qPCR was employed to validate the transcriptional regulation of the target gene NFE2L2 by Notch1. ResultsZGP improved serum sex hormones in ovarian aging rats, enhanced ovarian index, and optimized ovarian and uterine morphology, as well as follicle quantity composition. After transcriptome sequencing, KEGG analysis enriched the Notch signaling pathway and cell cycle, while GO analysis highlighted enrichment in the Notch pathway and stem cell population maintenance. Various experiments validated that ZGP significantly improved the expression of cell cycle-related proteins Cyclin D1 (CCND1), Cyclin E1 (CCNE1), cyclin-dependent kinase inhibitor 1a (CDKN1A), stemness markers Mouse Vasa Homolog (MVH), Octamer-binding Transcription Factor 4 (Oct4), Fragilis, 5-Bromo-2′-deoxyuridine (BrdU), as well as Notch1 and Nrf2 in aging ovarian tissues and OSCs. Additionally, ZGP promoted the proliferation of 4HC-damaged OSCs, optimized OSCs cell cycle composition, reduced G0/G1 phase arrest, and decreased early and late apoptosis. ZGP could reverse the detrimental effects on stemness and cell cycle of OSCs caused by blocking the Notch pathway. Furthermore, ZGP may activate the regulation of its target gene NFE2L2 by upregulating Notch1 expression in OSCs, thereby exerting therapeutic effects. ConclusionZGP protects ovarian function in CTX-induced ovarian aging rats by regulating the Notch1/Nrf2 pathway. It restores serum sex hormone levels, maintains normal follicle development, promotes the proliferation of aged OSCs, optimizes the cell cycle, reduces apoptosis, and preserves stemness, thereby alleviating ovarian aging.

Combining in silico and in vitro approaches for understanding the mechanism of action of the galactomannan extracted from Cassia grandis seeds against colorectal cancer

This study aimed to investigate the antitumor activity of galactomannan extracted from Cassia grandis seeds (GCg) against colorectal cancer cells using both experimental and computational approaches. Galactomannan was extracted from C. grandis seeds and prepared into solutions with varying concentrations. The cytotoxicity of these solutions was tested on HT-29 and HCT-116 colorectal cancer cell lines using the MTT assay. Additionally, computational evaluations, including molecular docking and molecular dynamics simulations, were performed to explore the potential binding interactions of GCg with cyclin-dependent kinase 2 (CDK2). The experimental results demonstrated that GCg significantly inhibited the proliferation of HT-29 cells, especially at concentrations of 5 mg/mL. On the other hand, no concentration inhibited >30 % of HCT-116 cells. Computational analysis revealed that GCg could bind to the ATP-binding site of CDK2, promoting the inactive DFG-out conformation, similar to the known inhibitor K03861. This interaction suggests a mechanism through which GCg may exert its anticancer effects. GCg exhibits significant cytotoxic activity against HT-29 colorectal adenocarcinoma cells, likely through the inhibition of CDK2; however, its efficacy against HCT-116 cells is limited, possibly due to structural differences in the molecular targets. To the best of the authors' knowledge, no studies have explored the applications of GCg in cancers, particularly colorectal ones. Further studies are needed to explore the antimetastatic effects and potential clinical applications of GCg in colorectal cancer treatment.

Roscovitine, a CDK Inhibitor, Reduced Neuronal Toxicity of mHTT by Targeting HTT Phosphorylation at S1181 and S1201 In Vitro.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by a single mutation in the huntingtin gene (HTT). Normal HTT has a CAG trinucleotide repeat at its N-terminal within the range of 36. However, once the CAG repeats exceed 37, the mutant gene (mHTT) will encode mutant HTT protein (mHTT), which results in neurodegeneration in the brain, specifically in the striatum and other brain regions. Since the mutation was discovered, there have been many research efforts to understand the mechanism and develop therapeutic strategies to treat HD. HTT is a large protein with many post-translational modification sites (PTMs) and can be modified by phosphorylation, acetylation, methylation, sumoylation, etc. Some modifications reduced mHTT toxicity both in cell and animal models of HD. We aimed to find the known kinase inhibitors that can modulate the toxicity of mHTT. We performed an in vitro kinase assay using HTT peptides, which bear different PTM sites identified by us previously. A total of 368 kinases were screened. Among those kinases, cyclin-dependent kinases (CDKs) affected the serine phosphorylation on the peptides that contain S1181 and S1201 of HTT. We explored the effect of CDK1 and CDK5 on the phosphorylation of these PTMs of HTT and found that CDK5 modified these two serine sites, while CDK5 knockdown reduced the phosphorylation of S1181 and S1201. Modifying these two serine sites altered the neuronal toxicity induced by mHTT. Roscovitine, a CDK inhibitor, reduced the p-S1181 and p-S1201 and had a protective effect against mHTT toxicity. We further investigated the feasibility of the use of roscovitine in HD mice. We confirmed that roscovitine penetrated the mouse brain by IP injection and inhibited CDK5 activity in the brains of HD mice. It is promising to move this study to in vivo for pre-clinical HD treatment.

CCRG-04. RIBOCICLIB RESPONSIVE MENINGIOMA IN THE TREATMENT OF BREAST CANCER

Abstract BACKGROUND Meningiomas are the most common primary intracranial tumors, typically managed with surgical resection and/or radiation therapy. Systemic therapy options are limited and reserved for cases refractory to conventional interventions. Cyclin dependent kinase (CDK) proteins are key cell cycle regulators. CDK inhibitors are clinically available, approved for treatment of breast cancer and in clinical trials for meningioma. METHODS We present a case where a patient with incidentally-discovered intracranial meningioma undergoing CDK inhibitor therapy with ribociclib for breast cancer experienced a radiographic response. RESULTS A 73-year-old female was diagnosed with estrogen receptor (ER) positive, progesterone receptor (PR) positive, HER2 negative metastatic invasive ductal carcinoma of the breast. She was treated with estrogen receptor antagonist fulvestrant and CDK 4/6 inhibitor ribociclib. MRI of the brain performed for disease staging demonstrated an extraaxial, dural-based, homogenously enhancing mass along the left posterior petrous ridge consistent with a meningioma. Two-month interval scan demonstrated a marginal decrease in size of the mass (15.6x18.3 mm to 15.4x17.5 mm). Systemic disease related to breast cancer concurrently improved. Two years later, with ongoing fulvestrant and ribociclib therapy, a repeat MRI brain demonstrated further decrease in size of the meningioma (13.4x16.8 mm). CONCLUSIONS Hormonally-directed therapies previously demonstrated limited benefit for meningiomas despite PR/ER positivity reported for these tumors. However, CDK 4/6 inhibitors abemaciclib and ribociclib have demonstrated activity in treatment of recurrent grade 2/3 meningiomas. The radiographic response noted in our case suggests there may be a role for systemic therapy even in treatment-naive cases that may not be amenable to surgical resection or radiation therapy.

CSIG-09. BEYOND SINGLE AGENTS: EXPLORING THE POTENTIAL OF ABEMACICLIB IN COMBINATION WITH PANOBINOSTAT FOR IMPROVED GLIOMA TREATMENT

Abstract BACKGROUND Glioblastoma is the most common primary central nervous system tumour with a median survival of less than 15 months. Addressing the underlying redundant, and converging signaling pathways necessitates the utilization of small molecule inhibitors capable of simultaneous targeting and inhibition. In glioma, the aberrant CDK4/6-Rb pathway dysregulation resulting in disruption of cell cycle checkpoint progression can lead to uncontrolled cell division, a hallmark of cancer. The neuro-pharmacokinetics of abemaciclib, a Cyclin-dependent kinase inhibitor, is being currently investigated in phase 1 clinical trials by National Cancer Institue, [NCT05413304]. The importance of panobinostat as a Histone deacetylase inhibitor and potentiating the effects of various small molecular inhibitors in published literature is paramount. This study is based on investigating ways to overcome resistance by exploring the synergistic cytotoxic effects of abemaciclib in combination with panobinostat in glioma. METHODS We investigated the antiproliferative effects of abemaciclib and panobinostat on glioma cells using an MTS cell proliferation assay. Inhibitor combination analysis was done using, SYNERGYFINDER via zip-model. Flow cytometry with Annexin V staining further assessed cell death and apoptosis induced. RESULTS The antiproliferative effects of abemaciclib, alone and in combination with panobinostat, in pediatric lines (KNS 42, SJG2), and adult human glioblastoma line, SF188 exhibited lower IC50 as compared to adult high grade glioma lines (LN 18, LNZ 308). Synergy analysis revealed a strong cytotoxic effect in KNS 42 and SF 188 cells treated with the combination. Flow cytometric analysis indicated that the combination therapy induced significant cell death only in a subset of cell lines- KNS 42 and SF 188, suggesting underlying genetic heterogeneity influences treatment response, warranting further mechanistic studies. CONCLUSION Combination therapies using abemaciclib and panobinostat, targeting CDK4/6 and histone deacetylation pathways, show promise against aggressive and treatment-resistant gliomas. Further investigation into these combination approaches is crucial to understand resistant mechanisms, optimize efficacy, and establish their clinical efficacy for improving glioma patient outcomes.

PRMT5/WDR77 Enhances the Proliferation of Squamous Cell Carcinoma via the ΔNp63α-p21 Axis.

Protein arginine methyltransferase 5 (PRMT5) is a critical oncogenic factor in various cancers, and its inhibition has shown promise in suppressing tumor growth. However, the role of PRMT5 in squamous cell carcinoma (SCC) remains largely unexplored. In this study, we analyzed SCC patient data from The Cancer Genome Atlas (TCGA) and the Cancer Dependency Map (DepMap) to investigate the relationship between PRMT5 and SCC proliferation. We employed competition-based cell proliferation assays, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays, flow cytometry, and in vivo mouse modeling to examine the regulatory roles of PRMT5 and its binding partner WDR77 (WD repeat domain 77). We identified downstream targets, including the p63 isoform ΔNp63α and the cyclin-dependent kinase inhibitor p21, through single-cell RNA-seq, RT-qPCR, and Western blot analyses. Our findings demonstrate that upregulation of PRMT5 and WDR77 correlates with the poor survival of head and neck squamous cell carcinoma (HNSCC) patients. PRMT5/WDR77 regulates the HNSCC-specific transcriptome and facilitates SCC proliferation by promoting cell cycle progression. The PRMT5 and WDR77 stabilize the ΔNp63α Protein, which in turn, inhibits p21. Moreover, depletion of PRMT5 and WDR77 repress SCC in vivo. This study reveals for the first time that PRMT5 and WDR77 synergize to promote SCC proliferation via the ΔNp63α-p21 axis, highlighting a novel therapeutic target for SCC.

From precursor to cancer: decoding the intrinsic and extrinsic pathways of pancreatic intraepithelial neoplasia progression.

This review explores the progression of pancreatic intraepithelial neoplasia (PanIN) to pancreatic ductal adenocarcinoma through a dual lens of intrinsic molecular alterations and extrinsic microenvironmental influences. PanIN development begins with Kirsten rat sarcoma viral oncogene (KRAS) mutations driving PanIN initiation. Key additional mutations in cyclin-dependent kinase inhibitor 2A (CDKN2A), tumor protein p53 (TP53), and mothers against decapentaplegic homolog 4 (SMAD4) disrupt cell cycle control and genomic stability, crucial for PanIN progression from low-grade to high-grade dysplasia. Additional molecular alterations in neoplastic cells, including epigenetic modifications and chromosomal alterations, can further contribute to neoplastic progression. In parallel with these alterations in neoplastic cells, the microenvironment, including fibroblast activation, extracellular matrix remodeling, and immune modulation, plays a pivotal role in PanIN initiation and progression. Crosstalk between neoplastic and stromal cells influences nutrient support and immune evasion, contributing to tumor development, growth, and survival. This review underscores the intricate interplay between cell-intrinsic molecular drivers and cell-extrinsic microenvironmental factors, shaping PanIN predisposition, initiation, and progression. Future research aims to unravel these interactions to develop targeted therapeutic strategies and early detection techniques, aiming to alleviate the severe impact of pancreatic cancer by addressing both genetic predispositions and environmental influences.

Cyclin-Dependent Kinase Inhibitors in the Rare Subtypes of Melanoma Therapy.

Melanoma occurs in various forms and body areas, not only in the cutis, but also in mucous membranes and the uvea. Rarer subtypes of that cancer differ in genomic aberrations, which cause their minor sensibility to regular cutaneous melanoma therapies. Therefore, it is essential to discover new strategies for treating rare forms of melanoma. In recent years, interest in applying CDK inhibitors (CDKIs) in cancer therapy has grown, as they are able to arrest the cell cycle and inhibit cell proliferation. Current studies highlight selective CDK4/6 inhibitors, like palbociclib or abemaciclib, as a very promising therapeutic option, since they were accepted by the FDA for advanced breast cancer treatment. However, cells of every subtype of melanoma do not react to CDKIs the same way, which is partly because of the genetic differences between them. Herein, we discuss the past and current research relevant to targeting various CDKs in mucosal, uveal and acral melanomas. We also briefly describe the issue of amelanotic and desmoplastic types of melanoma and the need to do more research to discover cell cycle dysregulations, which cause the growth of the mentioned forms of cancer.

Inhibition of Cyclin-Dependent Kinase 9 Rapidly Induces Apoptosis in Acute Lymphoblastic Leukemia and Shows Synergistic Activity with BH3-Mimetics

Inhibition of Cyclin-Dependent Kinase 9 Rapidly Induces Apoptosis in Acute Lymphoblastic Leukemia and Shows Synergistic Activity with BH3-Mimetics