Palbociclib induces cell senescence and apoptosis of gastric cancer cells by inhibiting the Notch pathway

Regulation of cellular senescence in tumor progression and therapeutic targeting: mechanisms and pathways

Cellular senescence, a stable state of cell cycle arrest induced by various stressors or genomic damage, is recognized as a hallmark of cancer. It exerts a context-dependent dual role in cancer initiation and progression, functioning as a tumor suppressor and promoter. The complexity of senescence in cancer arises from its mechanistic diversity, potential reversibility, and heterogeneity. A key mediator of these effects is the senescence-associated secretory phenotype (SASP), a repertoire of bioactive molecules that influence tumor microenvironment (TME) remodeling, modulate cancer cell behavior, and contribute to therapeutic resistance. Given its intricate role in cancer biology, senescence presents both challenges and opportunities for therapeutic intervention. Strategies targeting senescence pathways, including senescence-inducing therapies and senolytic approaches, offer promising avenues for cancer treatment. This review provides a comprehensive analysis of the regulatory mechanisms governing cellular senescence in tumors. We also discuss emerging strategies to modulate senescence, highlighting novel therapeutic opportunities. A deeper understanding of these processes is essential for developing precision therapies and improving clinical outcomes.

Senolytics: charting a new course or enhancing existing anti-tumor therapies?

Cell senescence is a natural response within our organisms. Initially, it was considered an effective anti-tumor mechanism. However, it is now believed that while cell senescence initially acts as a robust barrier against tumor initiation, the subsequent accumulation of senescent cells can paradoxically promote cancer recurrence and cause damage to neighboring tissues. This intricate balance between cell proliferation and senescence plays a pivotal role in maintaining tissue homeostasis. Moreover, senescence cells secrete many bioactive molecules collectively termed the senescence-associated secretory phenotype (SASP), which can induce chronic inflammation, alter tissue architecture, and promote tumorigenesis through paracrine signaling. Among the myriads of compounds, senotherapeutic drugs have emerged as exceptionally promising candidates in anticancer treatment. Their ability to selectively target senescent cells while sparing healthy tissues represents a paradigm shift in therapeutic intervention, offering new avenues for personalized oncology medicine. Senolytics have introduced new therapeutic possibilities by enabling the targeted removal of senescent cells. As standalone agents, they can clear tumor cells in a senescent state and, when combined with chemo- or radiotherapy, eliminate residual senescent cancer cells after treatment. This dual approach allows for the intentional use of lower-dose therapies or the removal of unintended senescent cells post-treatment. Additionally, by targeting non-cancerous senescent cells, senolytics may help reduce tumor formation risk, limit recurrence, and slow disease progression. This article examines the mechanisms of cellular senescence, its role in cancer treatment, and the importance of senotherapy, with particular attention to the therapeutic potential of senolytic drugs.

Self-assembled natural triterpenoids for the delivery of cyclin-dependent kinase 4/6 inhibitors to enhance cancer chemoimmunotherapy

Immunogenic cell death (ICD) has recently emerged as a promising strategy in reinforcing anti-PD-L1 blockade immunotherapy of triple-negative breast cancer (TNBC). The CDK4/6 inhibitor palbociclib (PAL), as a clinical star medicine targeting the cell cycle machinery, is an ideal candidate for fabricating a highly efficient ICD inducer for TNBC chemoimmunotherapy. However, the frequently observed chemoresistance and clinical adverse effects, as well as significant antagonistic effects when co-administered with certain chemotherapeutics, have seriously restricted the efficiency of PAL and the feasibility of combination strategies. Herein, we screened and identified six self-assembled natural pentacyclic triterpenoid (PT) molecules that can serve as competent co-administration nanoplatforms for the synergistic or combined delivery of PAL. Analysis of two representative PT-PAL nano-assemblies validated that PT-mediated co-assembly enhances the cytotoxicity and synergy of PAL by inhibiting the PI3K/AKT/mTOR signaling pathway, rather than directly targeting CDK4/6 proteins. Importantly, the PAL nanoassemblies exhibited multiple favorable therapeutic features and stronger accumulative ICD induction, ensuring highly efficient synergistic anti-PD-L1 chemoimmunotherapy by simultaneously facilitating T-cell immune response and reversing the immunosuppressive tumor microenvironment. This study offers possibilities for improving the anticancer efficacy of CDK4/6 inhibitors and potential avenues for clinical applications of chemoimmunotherapy in treating TNBC.

TFAP2C-DDR1 axis regulates resistance to CDK4/6 inhibitor in breast cancer

Breast cancer is the predominant malignancy with the majority of cases are characterized as HR+/HER2-subtype. Although cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have shown remarkable efficacy in treating this subtype when combined with endocrine therapy, the development of resistance to these inhibitors remains a significant clinical obstacle. Hence, there is an urgent need to explore innovative therapies and decipher the underlying mechanisms of resistance to CDK4/6i. In this study, we employed quantitative high-throughput combination screening (qHTCS) and genomics/proteomics approaches to uncover the molecular mechanisms driving resistance to CDK4/6i (palbociclib) in breast cancer. The comprehensive analyses revealed DDR1 as a potential factor implicated in mediating resistance to CDK4/6i. Specifically, DDR1 inhibition in combination with palbociclib exhibited remarkable synergistic effects, reducing cell survival signaling and promoting apoptosis in resistant cells. In-vivo xenograft model further validated the synergistic effects, showing a significant reduction in the resistant tumor growth. Exploration into DDR1 activation uncovered TFAP2C as a key transcription factor regulating DDR1 expression in palbociclib resistant cells and inhibition of TFAP2C re-sensitized resistant cells to palbociclib. Gene set enrichment analysis (GSEA) in the NeoPalAna trial demonstrated a significant enrichment of the TFAP2C-DDR1 gene set from patitens after palbociclib treatment, suggesting the possible activation of the TFAP2C-DDR1 axis following palbociclib exposure. Overall, this study provides crucial insights into the novel molecular landscape of palbociclib resistance in breast cancer, suggesting TFAP2C-DDR1 axis inhibition as a promising strategy to overcome resistance.

CDK4/6 inhibition initiates cell cycle arrest by nuclear translocation of RB and induces a multistep molecular response

CDK4/6 inhibitors are standard of care in the treatment of metastatic breast cancer. Treatment regimen consists of a combination with endocrine therapy, since their therapeutic efficacy as monotherapy in most clinical trials was rather limited. Thus, understanding the molecular mechanisms that underlie response to therapy might allow for the development of an improved therapy design. We analyzed the response to the CDK4/6 inhibitor palbociclib in bladder cancer cells over a 48-hour time course using RNA sequencing and identified a multi-step mechanism of response. We next translated these results to the molecular mechanism in bladder cancer cells upon PD treatment. The initial step is characterized by translocation of the RB protein into the nucleus by activation of importin α/β, a mechanism that requires the NLS sequence. In parallel, RB is proteolyzed in the cytoplasm, a process regulated by gankyrin and the SCF complex. Only hypophosphorylated RB accumulates in the nucleus, which is an essential step for an efficient therapy response by initiating G1 arrest. This might explain the poor response in RB negative or mutated patients. At later stages during therapy, increased expression of the MiT/TFE protein family leads to lysosomal biogenesis which is essential to maintain this response. Lastly, cancer cells either undergo senescence and apoptosis or develop mechanisms of resistance following CDK4/6 inhibition.

Curcumin Induces Autophagy-mediated Ferroptosis by Targeting the PI3K/AKT/mTOR Signaling Pathway in Gastric Cancer

As a very common malignancy of the digestive system, the incidence and mortality rates of gastric cancer (GC) are increasing year by year. The critical role of ferroptosis in cancer development has been well-documented. The polyphenol compound curcumin shows prominent anti-tumor effects in multiple cancer types, including GC. However, whether curcumin participates in GC tumorigenesis by regulating ferroptosis remains unknown. Gastric cancer cells AGS and HGC-27 were treated with curcumin (0, 10, and 20 μM). Cell viability and death were evaluated through CCK-8 and LDH release assays. LC3B expression in cells was estimated through immunofluorescence staining. Intracellular ferrous iron (Fe2+), GSH, MDA, and lipid ROS levels were assessed by corresponding assay kits. The cellular levels of autophagy markers (ATG5, ATG7, Beclin 1, and LC3B), ferroptosis markers (ACSL4, SLC7A11, and GPX4), and phosphorylated (p)-PI3K, p-AKT, and p-mTOR were determined through western blotting. Curcumin attenuated cell viability but stimulated cell death in GC cells. Curcumin enhanced autophagy in GC cells, as demonstrated by the increased levels of ATG5, ATG7, Beclin 1, and LC3B. Besides, curcumin upregulated iron, MDA, GSH, and ACSL4 levels while downregulated lipid ROS, SLC7A11, and GPX4 levels, suggesting its stimulation on ferroptosis in GC cells. Curcumin decreased p-PI3K, p-AKT, and p-mTOR levels in cells. Importantly, the ferroptosis inhibitor ferrostatin-1 overturned the impacts of curcumin on GC cell viability, death, and ferroptosis. Curcumin suppresses GC development by inducing autophagy-mediated ferroptosis by inactivating the PI3K/AKT/mTOR signaling.

Mesoporous polydopamine Targeting CDK4/6 Inhibitor toward Brilliant Synergistic Immunotherapy of Breast Cancer

Immunotherapy utilizing anti-PD-L1 blockade has achieved dramatic success in clinical breast cancer management but is often hampered by the limited immune response. Increasing evidence shows that immunogenic cell death (ICD) recently arises as a promising strategy for enlarging tumor immunogenicity and eliciting systemic anti-tumor immunity effectively. However, developing simple but versatile, highly efficient but low-toxic, biosafe, and clinically available transformed ICD inducers remains a huge demand and is highly desirable. Herein, a multifunctional ICD inducer is purposefully developed A6-MPDA@PAL by integrating photothermal therapy (PTT) nanoplatforms mesoporous polydopamine (MPDA), CDK4/6 inhibitor palbociclib (PAL), and CD44-specific targeting A6 peptide in a simple way for augmenting the immune antitumor efficacy of anti-PD-L1 therapy. Remarkably, the light-inducible nanoplatforms exhibit multiple favorable therapeutic features ensuring a superior and biosafe PTT/chemotherapy efficacy. Together with stronger accumulative ICD induction, single administration of A6-MPDA@PAL can trigger robust systemic antitumor immunity and abscopal effect with the assistance of anti-PD-L1 blockade by fascinating the intratumoral infiltration of T lymphocytes and reversing the immunosuppressive tumor microenvironment simultaneously, therapy achieving brilliant synergistic immunotherapy with effective tumor ablation. This study presents a simple and smart ICD inducer opening up attractive clinical possibilities for reinforcing the anti-PD-L1 therapy against breast cancer.

Comprehensive analysis of CPNE1 predicts prognosis and drug resistance in gastric adenocarcinoma

BACKGROUND

Recent studies have confirmed that Copines-1 (CPNE1) is associated with many malignancies. However, the role of CPNE1 in stomach adenocarcinoma (STAD) is currently unclear.

METHODS

TIMER2.0, TCGA, UALCAN databases were used to investigate the expression of CPNE1 in STAD and normal tissues. KM-plotter database was used to explore the relationship between CPNE1 expression and prognosis in STAD. Immunohistochemistry (IHC) was used to assess the protein levels of CPNE1 in both normal and cancer tissues, as well as to confirm the prognostic significance of CPNE1. In order to assess the viability of CPNE1 as a divider, the Recipient Operating Characteristics (ROC) curve was employed and the assessment based on the AUC score (below the curve). To investigate the potential function of CPNE1, correlation analysis and enrichment analysis were performed with the clusterProfiler package in R software. The CPNE1 binding protein network was constructed by STRING and GeneMANIA. The relationship between methylation and prognosis was explored by Methsurv database. The Genomics of Drug Sensitivity in Cancer (GDSC) was employed to predict drug responsiveness in STAD. Ultimately, CCK-8 assays and RT-qPCR were performed to confirm the correlation between CPNE1 expression and the IC50 of Axitinib in the AGS cell line.

RESULT

CPNE1 is highly expressed in various cancers, including STAD. High expression of CPNE1 indicated poor overall survival (OS) of STAD (P < 0.05). The ROC curve suggested that CPNE1 was a potential diagnostic biomarker (AUC = 0.925). The functions of CPNE1 were enriched in DNA-acting catalytic activity, sulfur transferase activity, Ran GTPase binding, DNA helicase activity, helicase activity and eukaryotic ribosome biosynthesis. Hyper-methylated CPNE1 predicts better prognosis in STAD (P < 0.05). Additionally, STAD patients with high-expression CPNE1 seemed to be more resistant to the chemotherapeutic agents, including A-770041, WH-4-023, AZD-2281, AG-014699, AP-24534, Axitinib, AZD6244, RDEA119, AZD8055, Temsirolimus, Pazopanib and Roscovitine. In vitro experiments demonstrated the involvement of CPNE1 in Axitinib chemoresistance.

CONCLUSION

CPNE1 could be a predictive biomarker and a potential target for biological therapy in STAD.

Atonal homolog 7 (ATOH7) confers neuroprotection for photoreceptor cells in glaucoma via inhibition of the notch pathway

Single-cell RNA sequencing (scRNA-seq) technologies enable the profiling and analysis of the transcriptomes of single cells and hold promise for clarifying gene mechanisms at single-cell resolution. We based this study on scRNA-seq data to reveal glaucoma-related genes and downstream pathways with neuroprotection effects. The scRNA-seq datasets related to glaucoma of retinal tissue samples of human beings and Atonal Homolog 7 (ATOH7)-null mice were obtained from the GEO database. The 74 top marker genes and 20 cell clusters were obtained in human retinal tissue samples. The key gene ATOH7 was found after the intersection with genes from GeneCards data. In the ATOH7-null mouse retinal tissue samples, pseudotime inference demonstrated significant changes in cell differentiation. Moreover, mouse retinal photoreceptor cells (PRCs) were cultured and treated with lentivirus carrying oe-ATOH7 alone or in combination with Notch signaling pathway activator Jagged-1/FC, after which cell biological functions were determined. The involvement of ATOH7 in glaucoma was identified through regulating PRCs. Furthermore, ATOH7 conferred neuroprotection in PRCs in glaucoma by mediating the Notch signaling pathway. In vitro data confirmed that ATOH7 overexpression promoted the differentiation of PRCs and inhibited their apoptosis by suppressing the Notch signaling pathway. The evidence provided by our study highlighted the involvement of ATOH7 in the blockade of the Notch signaling pathway, resulting in the neuroprotection for PRCs in glaucoma.

Palbociclib-Induced Cellular Senescence Is Modulated by the mTOR Complex 1 and Autophagy

Despite not dividing, senescent cells acquire the ability to synthesize and secrete a plethora of bioactive molecules, a feature known as the senescence-associated secretory phenotype (SASP). In addition, senescent cells often upregulate autophagy, a catalytic process that improves cell viability in stress-challenged cells. Notably, this "senescence-related autophagy" can provide free amino acids for the activation of mTORC1 and the synthesis of SASP components. However, little is known about the functional status of mTORC1 in models of senescence induced by CDK4/6 inhibitors (e.g., Palbociclib), or the effects that the inhibition of mTORC1 or the combined inhibition of mTORC1 and autophagy have on senescence and the SASP. Herein, we examined the effects of mTORC1 inhibition, with or without concomitant autophagy inhibition, on Palbociclib-driven senescent AGS and MCF-7 cells. We also assessed the pro-tumorigenic effects of conditioned media from Palbociclib-driven senescent cells with the inhibition of mTORC1, or with the combined inhibition of mTORC1 and autophagy. We found that Palbociclib-driven senescent cells display a partially reduced activity of mTORC1 accompanied by increased levels of autophagy. Interestingly, further mTORC1 inhibition exacerbated the senescent phenotype, a phenomenon that was reversed upon autophagy inhibition. Finally, the SASP varied upon inhibiting mTORC1, or upon the combined inhibition of mTORC1 and autophagy, generating diverse responses in cell proliferation, invasion, and migration of non-senescent tumorigenic cells. Overall, variations in the SASP of Palbociclib-driven senescent cells with the concomitant inhibition of mTORC1 seem to depend on autophagy.

Drug-Like Small Molecules That Inhibit Expression of the Oncogenic MicroRNA-21

We report the discovery of drug-like small molecules that bind specifically to the precursor of the oncogenic and pro-inflammatory microRNA-21 with mid-nanomolar affinity. The small molecules target a local structure at the Dicer cleavage site and induce distinctive structural changes in the RNA, which correlate with specific inhibition of miRNA processing. Structurally conservative single nucleotide substitutions eliminate the conformational change induced by the small molecules, which is also not observed in other miRNA precursors. The most potent of these compounds reduces cellular proliferation and miR-21 levels in cancer cell lines without inhibiting kinases or classical receptors, while closely related compounds without this specific binding activity are inactive in cells. These molecules are highly ligand-efficient (MW < 330) and display specific biochemical and cellular activity by suppressing the maturation of miR-21, thereby providing an avenue toward therapeutic development in multiple diseases where miR-21 is abnormally expressed.

Therapy-Induced Tumor Cell Senescence: Mechanisms and Circumvention

Plasticity of tumor cells (multitude of molecular regulation pathways) allows them to evade cytocidal effects of chemo- and/or radiation therapy. Metabolic adaptation of the surviving cells is based on transcriptional reprogramming. Similarly to the process of natural cell aging, specific features of the survived tumor cells comprise the therapy-induced senescence phenotype. Tumor cells with this phenotype differ from the parental cells since they become less responsive to drugs and form aggressive progeny. Importance of the problem is explained by the general biological significance of transcriptional reprogramming as a mechanism of adaptation to stress, and by the emerging potential of its pharmacological targeting. In this review we analyze the mechanisms of regulation of the therapy-induced tumor cell senescence, as well as new drug combinations aimed to prevent this clinically unfavorable phenomenon.

Cyclin-Dependent Kinase 4/6 Inhibitors: A Potential Breakthrough Therapy for Malignancies of Gastrointestinal Tract

Cancer is the leading cause of death worldwide for which effective treatments remain limited. This article aimed to critically review and discuss the potential of targeting cell cycle machineries as a vital tool for cancer treatment. Cyclin dependent kinase (CDK) 4/6 inhibitors were originally approved by the United State Food and Drug Administration (US FDA) for advanced-stage breast cancer treatment. The nearly double-prolonged survival time in patients who received CDK4/6 inhibitors are superior to the conventional chemotherapy or endocrine therapy alone and, thus, these medications have been designated a breakthrough therapy by the US FDA. The requirement of CDK4/6 in the progression of cancer cells, but probably dispensable in normal cells, makes CDK4/6 a popular target for cancer treatment. The effects of CDK4/6 inhibitors in cancer may also involve the tumor microenvironment in which the therapeutic effects are synergistically pronounced. These emerging roles, hence, prompt investigations regarding their therapeutic potential in other cancers, including gastrointestinal cancer. Many preclinical and clinical studies of CDK4/6 inhibitors in gastrointestinal cancers are underway and, as a result, several new potentials are gradually reported. Contrariwise, the primary effect of this drug group is arresting the cell cycle rather than inducing cell death. The efficacy of using CDK4/6 inhibitors as a single regimen in clinical practice is then limited. In this article, the effects of CDK4/6 inhibitors on the progression of gastrointestinal cancers, at both preclinical and clinical levels are reviewed. The future directions for research and the possibility of CDK4/6 inhibitors being "breakthrough therapy" for gastrointestinal cancers are also discussed.

IFN-γ and TNF Induce Senescence and a Distinct Senescence-Associated Secretory Phenotype in Melanoma

Immune checkpoint blockade (ICB) therapy is a central pillar of melanoma treatment leading to durable response rates. Important mechanisms of action of ICB therapy include disinhibition of CD4+ and CD8+ T cells. Stimulated CD4+ T helper 1 cells secrete the effector cytokines interferon-gamma (IFN-γ) and tumor necrosis factor alpha (TNF), which induce senescence in tumor cells. Besides being growth-arrested, senescent cells are metabolically active and secrete a large spectrum of factors, which are summarized as senescence-associated secretory phenotype (SASP). This secretome affects the tumor growth. Here, we compared the SASP of cytokine-induced senescent (CIS) cells with the SASP of therapy-induced senescent (TIS) cells. Therefore, we established in vitro models for CIS and TIS in melanoma. The human melanoma cell lines SK-MEL-28 and WM115 were treated with the cytokines IFN-γ and TNF as CIS, the chemotherapeutic agent doxorubicin, and the cell cycle inhibitor palbociclib as TIS. Then, we determined several senescence markers, i.e., growth arrest, p21 expression, and senescence-associated β-galactosidase (SA-β-gal) activity. For SASP analyses, we measured the regulation and secretion of several common SASP factors using qPCR arrays, protein arrays, and ELISA. Each treatment initiated a stable growth arrest, enhanced SA-β-gal activity, and—except palbociclib—increased the expression of p21. mRNA and protein analyses revealed that gene expression and secretion of SASP factors were severalfold stronger in CIS than in TIS. Finally, we showed that treatment with the conditioned media (CM) derived from cytokine- and palbociclib-treated cells induced senescence characteristics in melanoma cells. Thus, we conclude that senescence induction via cytokines may lead to self-sustaining senescence surveillance of melanoma.