Preclinical evaluation of ribociclib and its synergistic effect in combination with alpelisib in non-keratinizing nasopharyngeal carcinoma

Evaluating the simultaneous electrochemical determination of antineoplastic drugs using LaNiO3/g-C3N4@RGH nanocomposite material

A novel electrochemical sensor based on LaNiO3/g-C3N4@RGH nanocomposite material was developed to simultaneously determine Ribociclib (RIBO) and Alpelisib (ALPE). Ribociclib and Alpelisib are vital anticancer medications used in the treatment of advanced breast cancer. The sensor exhibited excellent electrocatalytic activity towards the oxidation of RIBO and ALPE, enabling their simultaneous detection. The fabricated sensor was characterized using various techniques, including energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), which confirmed the successful synthesis of the LaNiO3/g-C3N4@RGH composite material. Electrochemical characterization revealed enhanced conductivity and lower resistance of the modified electrode compared to the bare electrode. The developed sensor exhibited high repeatability, reproducibility, stability, and selectivity toward RIBO detection. Furthermore, the sensor displayed high sensitivity with low detection limits of 0.88 nM for RIBO and 6.1 nM for ALPE, and linear ranges of 0.05-6.2 μM and 0.5-6.5 μM, respectively. The proposed electrochemical sensor offers a promising approach for simultaneously determining RIBO and ALPE in pharmaceutical formulations and biological samples with recovery data of 98.7-102.0 %, providing a valuable tool for anticancer drug analysis and clinical research.

Synergistic therapeutic potential of alpelisib in cancers (excluding breast cancer): Preclinical and clinical evidences

The phosphoinositide 3-kinase (PI3K) signaling pathway is well-known for its important role in cancer growth, proliferation and migration. The activation of PI3K pathway is always connected with endocrine resistance and poor prognosis in cancers. Alpelisib, a selective inhibitor of PI3K, has been demonstrated to be effective in combination with endocrine therapy in HR+ PIK3CA-mutated advanced breast cancer in preclinical and clinical trials. Recently, the synergistic effects of alpelisib combined with targeted agents have been widely reported in PIK3CA-mutated cancer cells, such as breast, head and neck squamous cell carcinoma (HNSCC), cervical, liver, pancreatic and lung cancer. However, previous reviews mainly focused on the pharmacological activities of alpelisib in breast cancer. The synergistic therapeutic potential of alpelisib in other cancers has not yet been well reviewed. In this review, an extensive study of related literatures (published until December 20, 2022) regarding the anti-cancer functions and synergistic effects of alpelisib was carried out through the databases. Useful information was extracted. We summarized the preclinical and clinical studies of alpelisib in combination with targeted anti-cancer agents in cancer treatment (excluding breast cancer). The combinations of alpelisib and other targeted agents significantly improved the therapeutic efficacy both in preclinical and clinical studies. Unfortunately, synergistic therapies still could not effectively avoid the possible toxicities and adverse events during treatment. Finally, some prospects for the combination studies in cancer treatment were provided in the paper. Taken together, this review provided valuable information for alpelisib in preclinical and clinical applications.

Targeted therapy for head and neck cancer: signaling pathways and clinical studies

Head and neck cancer (HNC) is malignant, genetically complex and difficult to treat and is the sixth most frequent cancer, with tobacco, alcohol and human papillomavirus being major risk factors. Based on epigenetic data, HNC is remarkably heterogeneous, and treatment remains challenging. There is a lack of significant improvement in survival and quality of life in patients with HNC. Over half of HNC patients experience locoregional recurrence or distal metastasis despite the current multiple traditional therapeutic strategies and immunotherapy. In addition, resistance to chemotherapy, radiotherapy and some targeted therapies is common. Therefore, it is urgent to explore more effective and tolerable targeted therapies to improve the clinical outcomes of HNC patients. Recent targeted therapy studies have focused on identifying promising biomarkers and developing more effective targeted therapies. A well understanding of the pathogenesis of HNC contributes to learning more about its inner association, which provides novel insight into the development of small molecule inhibitors. In this review, we summarized the vital signaling pathways and discussed the current potential therapeutic targets against critical molecules in HNC, as well as presenting preclinical animal models and ongoing or completed clinical studies about targeted therapy, which may contribute to a more favorable prognosis of HNC. Targeted therapy in combination with other therapies and its limitations were also discussed.

Combined Targeting of Pathogenetic Mechanisms in Pancreatic Neuroendocrine Tumors Elicits Synergistic Antitumor Effects

Pancreatic neuroendocrine neoplasms (PanNENs) are the second most common malignancy of the pancreas. Surgery remains the only curative treatment for localized disease. For patients with inoperable advanced or metastatic disease, few targeted therapies are available, but their efficacy is unpredictable and variable. Exploiting prior knowledge on pathogenetic processes involved in PanNEN tumorigenesis, we tested buparlisib (PI3K inhibitor) and ribociclib (CDK4/6 inhibitor), as single agents or in combination, in different preclinical models. First, we used cell lines representative of well-differentiated (INS-1E, NT-3) and poorly differentiated (BON-1) PanNENs. The combination of buparlisib with ribociclib reduced the proliferation of 2D and 3D spheroid cultures more potently than the individual drugs. Buparlisib, but not ribociclib, induced apoptosis. The anti-proliferative activity of the drugs correlated with downstream target inhibition at mRNA and protein levels. We then tested the drugs on primary islet microtissues from a genetic PanNET animal model (Men1-defective mice) and from wild-type mice: the drug combination was effective against the former without altering islet cell physiology. Finally, we treated PanNET patient-derived islet-like 3D tumoroids: the combination of buparlisib with ribociclib was effective in three out of four samples. Combined targeting of PI3K and CDK4/6 is a promising strategy for PanNENs spanning various molecular and histo-pathological features.

PI3K inhibitors in trastuzumab-resistant HER2-positive breast cancer cells with PI3K pathway alterations

The activation of the PI3K signaling pathway resulting from genetic alterations induces carcinogenesis and resistance to anticancer therapies. Breast cancer is a major malignancy that is associated with dysregulation of the PI3K signaling pathway. PIK3CA mutations and PTEN loss occur in every subtype of breast cancer. PI3K inhibitors are being evaluated in breast cancer after the success of an alpha isoform-specific PI3K inhibitor in estrogen receptor (ER)-positive/HER2-negative metastatic breast cancer. Some preclinical data indicate the potential for PI3K/mTOR targeting in combination with trastuzumab for HER2-positive breast cancer with or without expression of the estrogen receptor. However, the role of this therapy in HER2-positive breast cancer with PIK3CA mutations and/or PTEN loss remains unclear. We examined three HER2-positive, ER-negative breast cancer cell lines to determine the efficacy of a novel alpha isoform-specific PI3K inhibitor in combination with trastuzumab. The results indicated that this combination was effective in PIK3CA-mutant or PTEN-deficient breast cancer cells by inducing apoptosis and inhibiting the expression of downstream proteins. PTEN loss by siRNA modulation in parental HER2-positive cancer cells with PI3K signaling pathway alterations could not confer resistance to alpelisib or GDC-0077 plus trastuzumab. We selected the CK-MB-1 cell line without alterations in the PI3K pathway to demonstrate that PI3K inhibitors plus trastuzumab represented a biomarker-specific treatment. In vivo effects of alpelisib plus trastuzumab were tested and confirmed in a mouse model, showing the combination strategy offered the best opportunity to achieve tumor volume reduction. With known safety profiles, this cytotoxic chemotherapy-free regimen warrants further attention as a biomarker-driven strategy for treating HER2-positive breast cancer.

Cellular Senescence: Molecular Targets, Biomarkers, and Senolytic Drugs

Cellular senescence is defined as irreversible cell cycle arrest caused by various processes that render viable cells non-functional, hampering normal tissue homeostasis. It has many endogenous and exogenous inducers, and is closely connected with age, age-related pathologies, DNA damage, degenerative disorders, tumor suppression and activation, wound healing, and tissue repair. However, the literature is replete with contradictory findings concerning its triggering mechanisms, specific biomarkers, and detection protocols. This may be partly due to the wide range of cellular and in vivo animal or human models of accelerated aging that have been used to study senescence and test senolytic drugs. This review summarizes recent findings concerning senescence, presents some widely used cellular and animal senescence models, and briefly describes the best-known senolytic agents.

Recent Research Progress of Chiral Small Molecular Antitumor-Targeted Drugs Approved by the FDA From 2011 to 2019

Chiral drugs usually contain chiral centers, which are present as single enantiomers or racemates. Compared with achiral drugs, they have significant advantages in safety and efficacy with high stereoselectivity. Of these drugs, chirality not only exerts influence on the solubility and pharmacokinetic characteristics but also has specific mechanistic characteristics on their targets. We noted that small molecules with unique chiral properties have emerged as novel components of antitumor drugs approved by the FDA in decade. Since approved, these drugs have been continuously explored for new indications, new mechanisms, and novel combinations. In this mini review, recent research progress of twenty-two FDA-approved chiral small molecular-targeted antitumor drugs from 2011 to 2019 is summarized with highlighting the potential and advantages of their applications. We believe that these updated achievements may provide theoretical foundation and stimulate research interests for optimizing drug efficacy, expanding clinical application, overcoming drug resistance, and advancing safety in future clinical administrations of these chiral targeted drugs.

Mechanisms and Implications of CDK4/6 Inhibitors for the Treatment of NSCLC

Cyclin-dependent kinases (CDKs) are key regulators of cell cycle progression in malignant tumor cells and play an important role through complex molecular interactions. Dysregulation of CDK dependent pathways is often found in non-small cell lung cancer, which indicates its vulnerability and can be used in clinical benefit. CDK4/6 inhibitors can prevent tumor cells from entering the G approved 1 and S phases, which have been studied in a series of explorations and brought great clinical effect to patients and encouragement to both physicians and researchers, thereby showing potential as a new therapeutic agent. A series of preclinical and clinical studies have been carried out on CDK4/6 inhibitors in NSCLC, and have been achieved some results, which may become a new potential treatment in the future. This review focuses on the research progress on CDK4/6 inhibitors in NSCLC, particularly the mechanisms of action, drugs, clinical research progress, and future application.

Combination of Epithelial Growth Factor Receptor Blockers and CDK4/6 Inhibitor for Nasopharyngeal Carcinoma Treatment

Simple Summary

Our findings indicated that the EGF-EGFR pathway was highly activated in very young patients with recurrent or metastatic NPC. High EGFR expression in patients with metastatic NPC resulted in poor clinical outcomes. To examine whether the EGFR pathway serves as a therapeutic target for NPC, NPC patient-derived xenograft (PDX) and NPC cell lines were treated with EGFR inhibitors (EGFRi) and a cell cycle blocker. Either EGFRi or cell cycle blocker treatment alone could reduce NPC cell growth and PDX tumor growth. Furthermore, combination treatment exerted an additive suppression effect on PDX tumor growth. This study provides promising evidence that EGFRi used in combination with a cell cycle blocker may be used to treat patients with NPC.

Abstract

Background: Nasopharyngeal carcinoma (NPC) involves host genetics, environmental and viral factors. In clinical observations, patients of young and old ages were found to have higher recurrence and metastatic rates. Methods: Cytokine array was employed to screen druggable target(s). The candidate target(s) were confirmed through patient-derived xenografts (PDXs) and a new EBV-positive cell line, NPC-B13. Results: Overexpression of epithelial growth factor (EGF) and EGF receptor (EGFR) was detected in young patients than in older patients. The growth of NPC PDX tumors and cell lines was inhibited by EGFR inhibitors (EGFRi) cetuximab and afatinib when used separately or in combination with the cell cycle blocker palbociclib. Western blot analysis of these drug-treated PDXs demonstrated that the blockade of the EGF signaling pathway was associated with a decrease in the p-EGFR level and reduction in PDX tumor size. RNA sequencing results of PDX tumors elucidated that cell cycle-related pathways were suppressed in response to drug treatments. High EGFR expression (IHC score ≥ grade 3) was correlated with poor survival in metastatic patients (p = 0.008). Conclusions: Our results provide encouraging preliminary data related to the combination treatment of EGFRi and palbociclib in patients with NPC.

Anti-cancer therapy with cyclin-dependent kinase inhibitors: impact and challenges

The introduction of cyclin-dependent kinase 4/6 inhibitors (CKIs) has marked a major development in the standard treatment of advanced breast cancer. Extensive preclinical, translational and clinical research efforts into CKI agents are ongoing, and clinical application of this class of systemic anti-cancer therapy is anticipated to expand beyond metastatic breast cancer treatment. Emerging evidence indicates that mechanisms by which CKI agents exert their therapeutic effect transcend their initially expected impacts on cell cycle control into the realms of cancer immunology and metabolism. The recent expansion in our understanding of the multifaceted impact of CKIs on tumour biology has the potential to improve clinical study design, therapeutic strategies and ultimately patient outcomes. This review contextualises the current status of CKI therapy by providing an overview of the original and emerging insights into mechanisms of action and the evidence behind their current routine use in breast cancer management. Recent preclinical and clinical studies into CKIs across tumour types are discussed, including a synthesis of the more than 300 clinical trials of CKI-combination treatments registered as of November 2020. Key challenges and opportunities anticipated in the 2020s are explored, including treatment resistance, combination therapy strategies and potential biomarker development.

Combination of miR‑143 and miR‑506 reduces lung and pancreatic cancer cell growth through the downregulation of cyclin‑dependent kinases

Lung cancer (LC) and pancreatic cancer (PC) are the first and fourth leading causes of cancer‑related deaths in the US. Deregulated cell cycle progression is the cornerstone for rapid cell proliferation, tumor development, and progression. Here, we provide evidence that a novel combinatorial miR treatment inhibits cell cycle progression at two phase transitions, through their activity on the CDK4 and CDK1 genes. Following transfection with miR‑143 and miR‑506, we analyzed the differential gene expression of CDK4 and CDK1, using qPCR or western blot analysis, and evaluated cell cycle inhibition, apoptosis and cytotoxicity. The combinatorial miR‑143/506 treatment downregulated CDK4 and CDK1 levels, and induced apoptosis in LC cells, while sparing normal lung fibroblasts. Moreover, the combinatorial miR treatment demonstrated a comparable activity to clinically tested cell cycle inhibitors in inhibiting cell cycle progression, by presenting substantial inhibition at the G1/S and G2/M cell cycle transitions. More importantly, the miR‑143/506 treatment presented a broader application, effectively downregulating CDK1 and CDK4 levels, and reducing cell growth in PC cells. These findings suggest that the miR‑143/506 combination acts as a promising approach to inhibit cell cycle progression for cancer treatment with minimal toxicity to normal cells.

Cyclin-dependent kinase inhibitors in head and neck cancer and glioblastoma-backbone or add-on in immune-oncology?

Cyclin-dependent kinases (CDK) control the cell cycle and play a crucial role in oncogenesis. Pharmacologic inhibition of CDK has contributed to the recent clinical approval of dual CDK4/6 inhibitors for the treatment of breast and small cell lung cancer. While the anticancer cell effects of CDK inhibitors are well-established, preclinical and early clinical studies describe additional mechanisms of action such as chemo- and radiosensitization or immune stimulation. The latter offers great potential to incorporate CDK inhibitors in immune-based treatments. However, dosing schedules and accurate timing of each combination partner need to be respected to prevent immune escape and resistance. In this review, we provide a detailed summary of CDK inhibitors in the two solid cancer types head and neck cancer and glioblastoma multiforme; it describes the molecular mechanisms of response vs. resistance and covers strategies to avoid resistance by the combination of immunotherapy or targeted therapy.

Alpelisib for the treatment of PIK3CA-mutated, hormone receptor-positive, HER2-negative metastatic breast cancer

Introduction: Two-thirds of advanced breast cancers are hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative (HR+/HER2-). Gene mutations in PIK3CA, encoding the PI3K catalytic subunit alpha of phosphatidyl-inositol 3-kinase (PI3K), are a frequent event in this population and are implicated in hormone therapy resistance. Alpelisib is a PI3K-alpha inhibitor and is the first PI3K inhibitor approved, in association with fulvestrant, by the FDA and EMA, based on improved progression-free survival (PFS) versus fulvestrant alone in a randomized phase III trial in HR+/HER2-, PIK3CA-mutated tumors following progression on/after HT.Areas covered: The scientific rationale, preclinical development, pharmacokinetics, and clinical efficacy/safety of alpelisib-fulvestrant are summarized. The role of alpelisib in the clinical setting is discussed, referencing current therapeutic options and clinical challenges associated with alpelisib's safety profile.Expert opinion: Alpelisib is an option for patients with HR+/HER2-, PIK3CA-mutated tumors whose disease progressed during/after aromatase inhibitor treatment. The PFS benefit appears clinically significant over fulvestrant alone, with a 7.9 months, non-significant, improvement in overall survival. Its safety profile requires strict patient selection, mainly based on baseline glycemic status, and close monitoring.

Efficacy of Providing the PI3K p110α Inhibitor BYL719 (Alpelisib) to Middle-Aged Mice in Their Diet

BYL719 (alpelisib) is a small molecule inhibitor of PI3K p110α developed for cancer therapy. Targeted suppression of PI3K has led to lifespan extension in rodents and model organisms. If PI3K inhibitors are to be considered as an aging therapeutic, it is important to understand the potential consequences of long-term exposure, and the most practical way to achieve this is through diet administration. Here, we investigated the pharmacokinetics of BYL719 delivered in diet and the efficacy of BYL719 to suppress insulin signaling when administered in the diet of 8-month-old male and female mice. Compared to oral gavage, diet incorporation resulted in a lower peak plasma BYL719 (3.6 vs. 9.2 μM) concentration but similar half-life (~1.5 h). Consuming BYL719 resulted in decreased insulin signaling in liver and muscle within 72 h, and mice still showed impaired glucose tolerance and insulin sensitivity following 6 weeks of access to a diet containing 0.3 g/kg BYL719. However, consuming BYL719 did not affect food intake, body mass, muscle function (rotarod and hang time performance) or cognitive behaviors. This provides evidence that BYL719 has long-term efficacy without major toxicity or side effects, and suggests that administering BYL719 in diet is suitable for studying the effect of pharmacological suppression of PI3K p110α on aging and metabolic function.

Therapeutic evaluation of palbociclib and its compatibility with other chemotherapies for primary and recurrent nasopharyngeal carcinoma

BACKGROUND

Recent genomic analyses revealed that druggable molecule targets were only detectable in approximately 6% of patients with nasopharyngeal carcinoma (NPC). However, a dependency on dysregulated CDK4/6-cyclinD1 pathway signaling is an essential event in the pathogenesis of NPC. In this study, we aimed to evaluate the therapeutic efficacy of a specific CDK4/6 inhibitor, palbociclib, and its compatibility with other chemotherapeutic drugs for the treatment of NPC by using newly established xenograft models and cell lines derived from primary, recurrent, and metastatic NPC.

METHODS

We evaluated the efficacies of palbociclib monotherapy and concurrent treatment with palbociclib and cisplatin or suberanilohydroxamic acid (SAHA) in NPC cell lines and xenograft models. RNA sequencing was then used to profile the drug response-related pathways. Palbociclib-resistant NPC cell lines were established to determine the potential use of cisplatin as a second-line treatment after the development of palbociclib resistance. We further examined the efficacy of palbociclib treatment against cisplatin-resistant NPC cells.

RESULTS

In NPC cells, palbociclib monotherapy was confirmed to induce cell cycle arrest in the G1 phase in vitro. Palbociclib monotherapy also had significant inhibitory effects in all six tested NPC tumor models in vivo, as indicated by substantial reductions in the total tumor volumes and in Ki-67 proliferation marker expression. In NPC cells, concurrent palbociclib treatment mitigated the cytotoxic effect of cisplatin in vitro. Notably, concurrent treatment with palbociclib and SAHA synergistically promoted NPC cell death both in vitro and in vivo. This combination also further inhibited tumor growth by inducing autophagy-associated cell death. NPC cell lines with induced palbociclib or cisplatin resistance remained sensitive to treatment with cisplatin or palbociclib, respectively.

CONCLUSIONS

Our study findings provide essential support for the use of palbociclib as an alternative therapy for NPC and increase awareness of the effective timing of palbociclib administration with other chemotherapeutic drugs. Our results provide a foundation for the design of first-in-human clinical trials of palbociclib regimens in patients with NPC.

Exploring treatment with Ribociclib alone or in sequence/combination with Everolimus in ER+HER2-Rb wild-type and knock-down in breast cancer cell lines

Background

Breast cancer (BC) is the second most common type of cancer worldwide. Among targeted therapies for Hormone Receptor-positive (HR⁺) and Human Epidermal growth factor Receptor 2-negative (HER2⁻) BC, the Cyclin-Dependent Kinases (CDK4/6) are targeted by inhibitors such as Ribociclib (Rib); however, resistance to CDK4/6 inhibitors frequently develops. The aim of this work is to assess in vitro activity of Rib and Everolimus (Eve) in HR⁺HER2⁻ MCF-7 and HR⁻HER2⁻BT-549 BC cell lines.

Methods

HR⁺HER2⁻ MCF-7 and HR⁻HER2⁻ BT-549 BC cell lines were treated with increasing concentration of Rib and Eve (up to 80 μg/mL) for 48–72 h. Subsequently, HR⁺HER2⁻ MCF-7 cells were silenced for Retinoblastoma (Rb) gene, and thus, the effect of Rib in sequential or concurrent schedule with Eve for the treatment of both Rb wild type or Rb knock-down MCF-7 in vitro was evaluated. Cell viability of HR⁺HER2⁻ MCF-7cells treated with sequential and concurrent dosing schedule was analyzed by MTT assay. Moreover, cell cycle phases, cell death and senescence were evaluated by cytofluorimetric analysis after treatment with Rib or Eve alone or in combination.

Results

The sequential treatment didn’t produce a significant increase of cytotoxicity, compared to Rib alone. Instead, the cotreatment synergized to increase the cytotoxicity compared to Rib alone. The cotreatment reduced the percentage of cells in S and G2/M phases and induced apoptosis. Rib triggered senescence and Eve completely reversed this effect in Rb wild type BC cells. Rib also showed Rb-independent effects as shown by results in Rb knock-down MCF-7.

Conclusion

Overall, the Rib/Eve concurrent therapy augmented the in vitro cytotoxic effect, compared to Rib/Eve sequential therapy or single treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07619-1.

Targeting the polycomb repressive complex-2 related proteins with novel combinational strategies for nasopharyngeal carcinoma

Aberrant epigenetic regulation is critically involved in the pathogenesis of nasopharyngeal carcinoma (NPC), where abnormal histone methylation can be found in polycomb repressive complex-2 (PRC2) related cancer gene loci. This study investigated some novel combinational strategies against NPC in vitro using PRC2-targeting agents as a backbone. PRC2 subunit proteins were overexpressed in over 70% of NPC tumors and enhancer of zeste homolog-2 (EZH2) expression correlated with more advanced T-stage. Basal expression of EZH2 and embryonic ectoderm development (EED) was higher in Epstein-Bar virus (EBV)⁺ NPC cells than EBV^- cells. Treatment with an EED inhibitor (EED226) led to reduced levels of H3K27me3 with minimal inhibitory effect on NPC cell growth. The combination of an EZH2 inhibitor (EPZ-6438) and trichostatin-A (TSA) yielded the highest synergy score (12.64) in NPC cells in vitro than combinations using EED226 and agents like chemotherapy and azacitadine. Global gene expression analysis showed that EED226 predominantly affects the expression of major histocompatibility complex (MHC) class I genes and cell cycle-related genes in NPC cells. Furthermore, treatment with EED226 resulted in increased MHC-I proteins in vitro. Based on the prediction of an artificial neural network, a synergistic inhibitory effect on growth was found by combining EED226 with cyclin dependent kinase (CDK) 4/6 inhibitor (LEE011) in NPC cells. In summary, this study found that PRC2-targeting agents could exert synergistic effect on growth inhibition when combined with TSA or LEE011 in NPC cells. Since MHC-I genes alterations are found in a third of NPC tumors, the effect of EED226 on MHC-I genes expression on response to immunotherapy in NPC warrants further investigations.

Cellular expression profiles of Epstein-Barr virus-transformed B-lymphoblastoid cell lines

Epstein-Barr virus (EBV) can infect human B cells and is associated with various types of B cell lymphomas. Studies on the global alterations of the cellular pathways mediated by EBV-induced B cell transformation are limited. In the present study, microarray analysis was performed following generation of two EBV-infected B-lymphoblastoid cell lines (BLCL), in which normal B cells obtained from two healthy Thai individuals and transcriptomic profiles were compared with their respective normal B cells. The two EBV-transformed BLCL datasets exhibited a high degree of similarity between their RNA expression profiles, whereas the two normal B-cell datasets did not exhibit the same degree of similarity in their RNA expression profiles. Differential gene expression analysis was performed, and the results showed that EBV infection was able to dysregulate several cellular pathways in the human B-cell genes involved in cancer and cell activation, such as the MAPK, WNT and PI3K-Akt signaling pathways, which were upregulated in the BLCL and were associated with increased cellular proliferation and immortalization of EBV-infected B cells. Expression of proteins located in the plasma membrane, which initiate a biological response to ligand binding, were also notably upregulated. Expression of genes involved in cell cycle control, the p53 signaling pathway and cellular senescence were downregulated. In conclusion, genes that were markedly upregulated by EBV included those involved in the acquisition of a tumorigenic phenotype of BLCL, which was positively correlated with several hallmarks of cancer.

CDK4/6 inhibitors: a novel strategy for tumor radiosensitization

Recently, the focus of enhancing tumor radiosensitivity has shifted from chemotherapeutics to targeted therapies. Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are a novel class of selective cell cycle therapeutics that target the cyclin D-CDK4/6 complex and induce G1 phase arrest. These agents have demonstrated favorable effects when used as monotherapy or combined with endocrine therapy and targeted inhibitors, stimulating further explorations of other combination strategies. Multiple preclinical studies have indicated that CDK4/6 inhibitors exhibit a synergistic effect with radiotherapy both in vitro and in vivo. The principal mechanisms of radiosensitization effects include inhibition of DNA damage repair, enhancement of apoptosis, and blockade of cell cycle progression, which provide the rationale for clinical use. CDK4/6 inhibitors also induce cellular senescence and promote anti-tumor immunity, which might represent potential mechanisms for radiosensitization. Several small sample clinical studies have preliminarily indicated that the combination of CDK4/6 inhibitors and radiotherapy exhibited well-tolerated toxicity and promising efficacy. However, most clinical trials in combined therapy remain in the recruitment stage. Further work is required to seek optimal radiotherapy-drug combinations. In this review, we describe the effects and underlying mechanisms of CDK4/6 inhibitors as a radiosensitizer and discuss previous clinical studies to evaluate the prospects and challenges of this combination.

Targeting Cell Cycle in Breast Cancer: CDK4/6 Inhibitors

Deregulation of cell cycle, via cyclin D/CDK/pRb pathway, is frequently observed in breast cancer lending support to the development of drugs targeting the cell cycle control machinery, like the inhibitors of the cycline-dependent kinases (CDK) 4 and 6. Up to now, three CDK4/6 inhibitors have been approved by FDA for the treatment of hormone receptor-positive (HR+), HER2-negative metastatic breast cancer. These agents have been effective in improving the clinical outcomes, but the development of intrinsic or acquired resistance can limit the efficacy of these treatments. Clinical and translational research is now focused on investigation of the mechanism of sensitivity/resistance to CDK4/6 inhibition and novel therapeutic strategies aimed to improve clinical outcomes. This review summarizes the available knowledge regarding CDK4/6 inhibitor, the discovery of new biomarkers of response, and the biological rationale for new combination strategies of treatment.

MDM2 antagonists overcome intrinsic resistance to CDK4/6 inhibition by inducing p21

Intrinsic resistance of unknown mechanism impedes the clinical utility of inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) in malignancies other than breast cancer. Here, we used melanoma patient-derived xenografts (PDXs) to study the mechanisms for CDK4/6i resistance in preclinical settings. We observed that melanoma PDXs resistant to CDK4/6i frequently displayed activation of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway, and inhibition of this pathway improved CDK4/6i response in a p21-dependent manner. We showed that a target of p21, CDK2, was necessary for proliferation in CDK4/6i-treated cells. Upon treatment with CDK4/6i, melanoma cells up-regulated cyclin D1, which sequestered p21 and another CDK inhibitor, p27, leaving a shortage of p21 and p27 available to bind and inhibit CDK2. Therefore, we tested whether induction of p21 in resistant melanoma cells would render them responsive to CDK4/6i. Because p21 is transcriptionally driven by p53, we coadministered CDK4/6i with a murine double minute (MDM2) antagonist to stabilize p53, allowing p21 accumulation. This resulted in improved antitumor activity in PDXs and in murine melanoma. Furthermore, coadministration of CDK4/6 and MDM2 antagonists with standard of care therapy caused tumor regression. Notably, the molecular features associated with response to CDK4/6 and MDM2 inhibitors in PDXs were recapitulated by an ex vivo organotypic slice culture assay, which could potentially be adopted in the clinic for patient stratification. Our findings provide a rationale for cotargeting CDK4/6 and MDM2 in melanoma.

Emerging therapeutic targets for nasopharyngeal carcinoma: opportunities and challenges

Introduction: Nasopharyngeal carcinoma (NPC) is a major public health problem in several countries, especially those in Southeast Asia and North Africa. In its typical poorly differentiated form, the Epstein-Barr virus (EBV) genome is present in the nuclei of all malignant cells with restricted expression of a few viral genes. The malignant phenotype of NPC cells results from the influence of these viral products in combination with cellular genetic, epigenetic and functional alterations. With regard to host/tumor interactions, NPC is a remarkable example of immune escape in the context of a hot tumor.Areas covered: This article has an emphasis on emerging therapeutic targets that are considered upstream or at an early stage of clinical application. It examines targets related to cellular oncogenic alterations, latent EBV infection and tumor interactions with the immune system.Expert opinion: There is a remarkable emergence of new agents that target EBV products. The clinical application of these agents would benefit from a systematic and comprehensive molecular classification of NPCs and from easy access to pre-clinical models in public repositories. There is a strong rationale for more investigations on the potential of immune modulators, especially those related to NK cells.

CDK4/6 Inhibitor Palbociclib Amplifies the Radiosensitivity to Nasopharyngeal Carcinoma Cells via Mediating Apoptosis and Suppressing DNA Damage Repair

Background

Radiotherapy is the primary approach for nasopharyngeal carcinoma (NPC). Although high survival rates can be obtained with radiation for early stage lesions, distant metastasis and local recurrence frequently occur. In this study, we pioneeringly investigated the antitumor activity and underlying mechanism of cyclin-dependent kinase 4/6 inhibitor (palbociclib) combined with radiation on NPC cells.

Methods

Evaluation of radiation enhancement with palbociclib was based on results from CCK8 and clonogenicity assays for cell proliferation, flow cytometry for apoptosis, ROS level and cell cycle and immunocytochemistry for DNA double-strand break repair.

Results

Palbociclib inhibited cellular growth of RB-proficient CNE-1 and CNE-2 via reducing RB phosphorylation and arresting cell cycle. Combination regimens of palbociclib plus radiation were significantly superior to palbociclib or radiation only through inhibiting cellular growth and inducing apoptosis. Moreover, the antitumor activity of both concurrent palbociclib plus radiation and radiation followed by palbociclib consistently preceded that of palbociclib followed by radiation. Meanwhile, the two preferable combination regimens possessed higher proportion of G2/M phase cells, evidently inhibited DNA double-strand break repair and eventually triggered tumor cell apoptosis.

Conclusion

Our study demonstrated that palbociclib could provoke a strong antitumor activity as a potential adjuvant to radiation therapy for NPC harboring RB expression.