FGF19/FGFR4 signaling axis confines and switches the role of melatonin in head and neck cancer metastasis

Targeting fibroblast growth factor receptor (FGFR) with inhibitors in head and neck cancers: Their roles, mechanisms and challenges

Head and neck squamous cell carcinoma (HNSCC) is a common and aggressive type of cancer with significant rates of morbidity and mortality. Traditional treatment options, including radiotherapy, chemotherapy, and surgery, are widely used, but their effectiveness can be uncertain. As research in cancer therapies evolves, molecular-targeted therapies are increasingly recognized as promising alternatives for managing malignant tumors. Fibroblast growth factor receptors (FGFRs) have been shown to be one of the essential components in the pathways in the progression of HNSCC. This review aims to summarize and discuss the structure, functions, signaling pathways, abnormal alterations of FGFRs, and their roles in tumorigenesis and development. We have accumulated information from in vitro, in vivo, and clinical studies regarding FGFR inhibitors in HNSCC. However, the efficacy of FGFR inhibitors as a cancer therapy is limited, which may be due to the resistance to FGFR inhibitors. In this review we also discuss the potential mechanisms of FGFR inhibitor resistance in HNSCC. By enriching our understanding of the treatment with and resistance of FGFR inhibitors in HNSCC, researchers may unveil new therapeutic targets or strategies to enhance the efficacy of FGFR inhibitors in this context.

Melatonin regulates endoplasmic reticulum stress in diverse pathophysiological contexts: A comprehensive mechanistic review

The endoplasmic reticulum (ER) is crucial for protein quality control, and disruptions in its function can lead to various diseases. ER stress triggers an adaptive response called the unfolded protein response (UPR), which can either restore cellular homeostasis or induce cell death. Melatonin, a safe and multifunctional compound, shows promise in controlling ER stress and could be a valuable therapeutic agent for managing the UPR. By regulating ER and mitochondrial functions, melatonin helps maintain cellular homeostasis via reduction of oxidative stress, inflammation, and apoptosis. Melatonin can directly or indirectly interfere with ER-associated sensors and downstream targets of the UPR, impacting cell death, autophagy, inflammation, molecular repair, among others. Crucially, this review explores the mechanistic role of melatonin on ER stress in various diseases including liver damage, neurodegeneration, reproductive disorders, pulmonary disease, cardiomyopathy, insulin resistance, renal dysfunction, and cancer. Interestingly, while it alleviates the burden of ER stress in most pathological contexts, it can paradoxically stimulate ER stress in cancer cells, highlighting its intricate involvement in cellular homeostasis. With numerous successful studies using in vivo and in vitro models, the continuation of clinical trials is imperative to fully explore melatonin's therapeutic potential in these conditions.

PTX promotes breast cancer migration and invasion by recruiting ATF4 to upregulate FGF19

BACKGROUND

Widely-spread among women, breast cancer is a malignancy with fatalities, and chemotherapy is a vital treatment option for it. Recent studies have underscored the potential of chemotherapeutic agents such as paclitaxel, adriamycin, cyclophosphamide, and gemcitabine, among others, in facilitating tumor metastasis, with paclitaxel being extensively researched in this context. The molecular mechanism of these genes and their potential relevance to breast cancer is noteworthy.

METHOD

Clinical tissue specimens were used to analyze the expression and clinical significance of FGF19 or P-FGFR4 in patients with breast cancer before and after chemotherapy. qRT-PCR, ELISA, immunofluorescence and Western blotting were used to detect the expression level of FGF19 in breast cancer cells. The biological impacts of paclitaxel, FGF19, and ATF4 on breast cancer cells were assessed through CCK8, Transwell, and Western blot assays. The expression of ATF4 in breast cancer cells was determined through database analysis, Western blot analysis, qRT-PCR, and immunofluorescence. The direct interaction between FGF19 and ATF4 was confirmed by a luciferase assay, and Western blotting was used to assess the levels of key proteins in the stress response pathway. To confirm the effects of PTX and FGF19 in vivo, we established a lung metastasis model in nude mice.

RESULTS

FGF19 expression was increased in breast cancer patients after chemotherapy. Paclitaxel can boost the migration and invasion of breast cancer cells, accompanied by an increase in FGF19 expression. ATF4 might be involved in facilitating the enhancing effect of FGF19 on breast cancer cell migration. Finally, stimulation during paclitaxel treatment could trigger a stress response, influencing the expression of FGF19 and the migration of breast cancer cells.

CONCLUSION

These data suggest that paclitaxel regulates FGF19 expression through ATF4 and thus promotes breast cancer cell migration and invasion.

Comprehensive analysis of endoplasmic reticulum stress related signature in head and neck squamous carcinoma

Head and neck squamous carcinoma (HNSC) is a prevalent malignant disease, with the majority of patients being diagnosed at an advanced stage. Endoplasmic reticulum stress (ERS) is considered to be a process that promotes tumorigenesis and impacts the tumor microenvironment (TME) in various cancers. The study aims to investigate the predictive value of ERS in HNSC and explore the correlation between ERS-related genes and TME. A series of bioinformatics analyses were carried out based on mRNA and scRNA-seq data from the TCGA and GEO databases. We conducted RT-qPCR and western blot to validate the signature, and performed cell functional experiments to investigate the in vitro biological functions of the gene. We identified 63 ERS-related genes that were associated with outcome and stage in HNSC. A three-gene signature (ATF6, TRIB3, and UBXN6) was developed, which presents predictive value in the prognosis and immunotherapy response of HNSC patients. The high-risk group exhibited a worse prognosis but may benefit from immunotherapy. Furthermore, there was a significant correlation between the signature and immune infiltration. In the high-risk group, fibroblasts were more active in intercellular communication, and more T cells were observed at the end of the sequential phase. The genes in the ERS-related signature were overexpressed in HNSC cells, and the knockdown of TRIB3 significantly inhibited cell proliferation and migration. This study established a novel ERS-related signature that has potential implications for HNSC therapy and the understanding of TME.

Melatonin inhibits the stemness of head and neck squamous cell carcinoma by modulating HA synthesis via the FOSL1/HAS3 axis

Hyaluronic acid (HA) is a glycosaminoglycan and the main component of the extracellular matrix (ECM), which has been reported to interact with its receptor CD44 to play critical roles in the self-renewal and maintenance of cancer stem cells (CSCs) of multiple malignancies. Melatonin is a neuroendocrine hormone with pleiotropic antitumor properties. However, whether melatonin could regulate HA accumulation in the ECM to modulate the stemness of head and neck squamous cell carcinoma (HNSCC) remains unknown. In this study, we found that melatonin suppressed CSC-related markers, such as CD44, of HNSCC cells and decreased the tumor-initiating frequency of CSCs in vivo. In addition, melatonin modulated HA synthesis of HNSCC cells by downregulating the expression of hyaluronan synthase 3 (HAS3). Further study showed that the Fos-like 1 (FOSL1)/HAS3 axis mediated the inhibitory effects of melatonin on HA accumulation and stemness of HNSCC in a receptor-independent manner. Taken together, melatonin modulated HA synthesis through the FOSL1/HAS3 axis to inhibit the stemness of HNSCC cells, which elucidates the effect of melatonin on the ECM and provides a novel perspective on melatonin in HNSCC treatment.

FGF19/FGFR4 signaling contributes to hepatocellular carcinoma survival and immune escape by regulating IGF2BP1-mediated expression of PD-L1

Immune-checkpoint blockade (ICB) therapies have been widely used in clinical treatment of cancer patients, but only 20-30% of patients benefit from immunotherapy. Therefore, it is important to decipher the molecular mechanism of resistance to ICB and develop new combined treatment strategies. PD-L1 up-regulation in tumor cells contributes to the occurrence of immune escape. Increasing evidence shows that its transcription level is affected by multiple factors, which limits the objective response rate of ICB. Fibroblast growth factor 19 (FGF19), a member of the fibroblast growth factor family, is widely involved in the malignant progression of many tumors by binding to fibroblast growth factor receptor 4 (FGFR4). In this study, we confirmed that FGF19 acts as a driver gene in hepatocellular carcinoma (HCC) progression by binding to FGFR4. The up-regulation of FGF19 and FGFR4 in HCC is associated with poor prognosis. We found that FGF19/FGFR4 promoted the proliferation and invasion of HCC cells by driving IGF2BP1 to promote PD-L1 expression. Knockdown of FGFR4 significantly reduced the expression of IGF2BP1/PD-L1 and inhibited the proliferation and invasion of HCC cells. These biological effects are achieved by inhibiting the PI3K/AKT pathway. The combination of FGFR4 knockdown and anti-PD-1 antibody greatly suppressed tumor growth and enhanced the sensitivity of immunotherapy, highlighting the clinical significance of FGF19/FGFR4 activation in immunotherapy.

Potential of melatonin to reverse epigenetic aberrations in oral cancer: new findings

It is now an accepted principle that epigenetic alterations cause cellular dyshomeostasis and functional changes, both of which are essential for the initiation and completion of the tumor cycle. Oral carcinogenesis is no exception in this regard, as most of the tumors in the different subsites of the oral cavity arise from the cross-reaction between (epi)genetic inheritance and the huge challenge of environmental stressors. Currently, the biochemical machinery is put at the service of the tumor program, halting the cell cycle, triggering uncontrolled proliferation, driving angiogenesis and resistance to apoptosis, until the archetypes of the tumor phenotype are reached. Melatonin has the ability to dynamically affect the epigenetic code. It has become accepted that melatonin can reverse (epi)genetic aberrations present in oral and other cancers, suggesting the possibility of enhancing the oncostatic capacity of standard multimodal treatments by incorporating this indolamine as an adjuvant. First steps in this direction confirm the potential of melatonin as a countermeasure to mitigate the detrimental side effects of conventional first-line radiochemotherapy. This single effect could produce synergies of extraordinary clinical importance, allowing doses to be increased and treatments not to be interrupted, ultimately improving patients' quality of life and prognosis. Motivated by the urgency of improving the medical management of oral cancer, many authors advocate moving from in vitro and preclinical research, where the bulk of melatonin cancer research is concentrated, to systematic randomized clinical trials on large cohorts. Recognizing the challenge to improve the clinical management of cancer, our motivation is to encourage comprehensive and robust research to reveal the clinical potential of melatonin in oral cancer control. To improve the outcome and quality of life of patients with oral cancer, here we provide the latest evidence of the oncolytic activity that melatonin can achieve by manipulating epigenetic patterns in oronasopharyngeal tissue.

Antioxidant Use after Diagnosis of Head and Neck Squamous Cell Carcinoma (HNSCC): A Systematic Review of Application during Radiotherapy and in Second Primary Cancer Prevention

Approximately 5-20% of HNSCC patients experience second primary cancers within the first 5 years of treatment, contributing to high mortality rates. Epidemiological evidence has linked a low dietary intake of antioxidants to an increased risk of cancer, especially squamous cell carcinoma, prompting research into their potential in neoplasm chemoprevention. Cigarette smoking is the primary risk factor for HNSCC, and a diet rich in antioxidants offers protective effects against head and neck cancer. Paradoxically, smokers, who are at the highest risk, tend to consume fewer antioxidant-rich fruits and vegetables. This has led to the hypothesis that integrating antioxidants into the diet could play a role in both primary and secondary prevention for at-risk individuals. Furthermore, some HNSCC patients use antioxidant supplements during chemotherapy or radiotherapy to manage side effects, but their impact on cancer outcomes remains uncertain. This systematic review explores the evidence for the potential use of antioxidants in preventing second primary cancers in HNSCC patients. In conclusion, none of the antioxidants tested so far (α-tocopherol, β-carotene, JP, Isotretinoin, interferon α-2a, vitamin E, retinyl palmitate, N-acetylcysteine) was effective in preventing second primary tumors in HNSCC patients, and they could only be used in reducing the side effects of radiotherapy. Further research is needed to better understand the interplay between antioxidants and cancer outcomes in this context.

Adaptive c-Met-PLXDC2 Signaling Axis Mediates Cancer Stem Cell Plasticity to Confer Radioresistance-associated Aggressiveness in Head and Neck Cancer

Radiotherapy plays an essential role in the treatment of head and neck squamous cell carcinoma (HNSCC), yet radioresistance remains a major barrier to therapeutic efficacy. A better understanding of the predominant pathways determining radiotherapy response could help develop mechanism-informed therapies to improve cancer management. Here we report that radioresistant HNSCC cells exhibit increased tumor aggressiveness. Using unbiased proteome profiler antibody arrays, we identify that upregulation of c-Met phosphorylation is one of the critical mechanisms for radioresistance in HNSCC cells. We further uncover that radioresistance-associated HNSCC aggressiveness is effectively exacerbated by c-Met but is suppressed by its genetic knockdown and pharmacologic inactivation. Mechanistically, the resulting upregulation of c-Met promotes elevated expression of plexin domain containing 2 (PLXDC2) through activating ERK1/2-ELK1 signaling, which in turn modulates cancer cell plasticity by epithelial-mesenchymal transition (EMT) induction and enrichment of the cancer stem cell (CSC) subpopulation, leading to resistance of HNSCC cells to radiotherapy. Depletion of PLXDC2 overcomes c-Met-mediated radioresistance through reversing the EMT progress and blunting the self-renewal capacity of CSCs. Therapeutically, the addition of SU11274, a selective and potent c-Met inhibitor, to radiation induces tumor shrinkage and limits tumor metastasis to lymph nodes in an orthotopic mouse model. Collectively, these significant findings not only demonstrate a novel mechanism underpinning radioresistance-associated aggressiveness but also provide a possible therapeutic strategy to target radioresistance in patients with HNSCC.

Significance

This work provides novel insights into c-Met-PLXDC2 signaling in radioresistance-associated aggressiveness and suggests a new mechanism-informed therapeutic strategy to overcome failure of radiotherapy in patients with HNSCC.

A stay of execution: ATF4 regulation and potential outcomes for the integrated stress response

ATF4 is a cellular stress induced bZIP transcription factor that is a hallmark effector of the integrated stress response. The integrated stress response is triggered by phosphorylation of the alpha subunit of the eukaryotic initiation factor 2 complex that can be carried out by the cellular stress responsive kinases; GCN2, PERK, PKR, and HRI. eIF2α phosphorylation downregulates mRNA translation initiation en masse, however ATF4 translation is upregulated. The integrated stress response can output two contradicting outcomes in cells; pro-survival or apoptosis. The mechanism for choice between these outcomes is unknown, however combinations of ATF4 heterodimerisation partners and post-translational modifications have been linked to this regulation. This semi-systematic review article covers ATF4 target genes, heterodimerisation partners and post-translational modifications. Together, this review aims to be a useful resource to elucidate the mechanisms controlling the effects of the integrated stress response. Additional putative roles of the ATF4 protein in cell division and synaptic plasticity are outlined.

Reciprocal FGF19-GLI2 signaling induces epithelial-to-mesenchymal transition to promote lung squamous cell carcinoma metastasis

PURPOSE

Metastatic lung squamous cell carcinoma (LUSC) is one of the most common causes of cancer death worldwide. As yet, however, the molecular mechanism underlying LUSC metastasis remains elusive. In this study, we report a novel mechanism involving signaling interactions between FGF19 and GLI2 that could drive the progression of LUSC.

METHODS

The expression of FGF19 in human LUSC samples was assessed by immunohistochemistry. The concentration of FGF19 in serum samples was assessed by ELISA. RNA sequencing, scratch wound-healing, trans-well, GO analysis, GSEA, luciferase reporter, Western blotting, immunofluorescence and immunohistochemistry assays, as well as an animal model were used to investigate the molecular mechanism underlying FGF19 driven LUSC progression. The therapeutic effect of a GLI2 inhibitor was determined using both in vitro cellular and in vivo animal experiments.

RESULTS

We found that FGF19, a member of the fibroblast growth factor family, plays a crucial role in the invasion and metastasis of LUSC, and identified GLI2 as an important downstream effector of FGF19 involved in metastasis. Surprisingly, we found that FGF19 and GLI2 could reciprocally induce the expression of each other, and form a positive feedback loop to promote LUSC cell invasion and metastasis. These findings were corroborated by an association between a poor prognosis of LUSC patients and FGF19/GLI2 co-expression. In addition, we found that the GLI inhibitor GANT61 could effectively reduce FGF19-mediated LUSC invasion and metastasis.

CONCLUSION

Our data suggest that FGF19 may serve as a novel biomarker for predicting metastatic LUSC. Intervening with the FGF19-GLI2 feedback loop may be a strategy for the treatment of FGF19-driven LUSC metastasis.

Melatonin: Emerging Player in the Management of Oral Cancer

Oral cancer (OC) has emerged as a major medical and social issue in many industrialized nations due to the high death rate. It is becoming increasingly common in people under the age of 45, although the underlying causes and mechanisms of this increase remain unclear. Melatonin, as a pleiotropic hormone, plays a pivotal role in a wide variety of cellular and physiological functions. Mounting evidence supports melatonin's ability to modify/influence oral carcinogenesis, help in the reduction of the incidence of OC, and increase chemo- and radiosensitivity. Despite its potential anti-carcinogenic effects, the precise function of melatonin in the management of OC is not well understood. This review summarizes the current knowledge regarding melatonin function in anti-carcinogenesis mechanisms for OC. In addition, clinical assessment and the potential therapeutic utility of melatonin in OC are discussed. This review will provide a basis for researchers to create new melatonin-based personalized medicines for treating and preventing OC.

Melatonin inhibits ESCC tumor growth by mitigating the HDAC7/β-catenin/c-Myc positive feedback loop and suppressing the USP10-maintained HDAC7 protein stability

BACKGROUND

Melatonin, a natural hormone secreted by the pineal gland, has been reported to exhibit antitumor properties through diverse mechanisms of action. However, the oncostatic function of melatonin on esophageal squamous cell carcinoma (ESCC) remains elusive. This study was conducted to investigate the potential effect and underlying molecular mechanism of melatonin as single anticancer agent against ESCC cells.

METHODS

ESCC cell lines treated with or without melatonin were used in this study. In vitro colony formation and EdU incorporation assays, and nude mice tumor xenograft model were used to confirm the proliferative capacities of ESCC cells. RNA-seq, qPCR, Western blotting, recombinant lentivirus-mediated target gene overexpression or knockdown, plasmids transfection and co-IP were applied to investigate the underlying molecular mechanism by which melatonin inhibited ESCC cell growth. IHC staining on ESCC tissue microarray and further survival analyses were performed to explore the relationship between target genes' expression and prognosis of ESCC.

RESULTS

Melatonin treatment dose-dependently inhibited the proliferative ability and the expression of histone deacetylase 7 (HDAC7), c-Myc and ubiquitin-specific peptidase 10 (USP10) in ESCC cells (P < 0.05). The expressions of HDAC7, c-Myc and USP10 in tumors were detected significantly higher than the paired normal tissues from 148 ESCC patients (P < 0.001). Then, the Kaplan-Meier survival analyses suggested that ESCC patients with high HDAC7, c-Myc or USP10 levels predicted worse overall survival (Log-rank P < 0.001). Co-IP and Western blotting analyses further revealed that HDAC7 physically deacetylated and activated β-catenin thus promoting downstream target c-Myc gene transcription. Notably, our mechanistic study validated that HDAC7/β-catenin/c-Myc could form the positive feedback loop to enhance ESCC cell growth, and USP10 could deubiquitinate and stabilize HDAC7 protein in the ESCC cells. Additionally, we verified that inhibition of the HDAC7/β-catenin/c-Myc axis and USP10/HDAC7 pathway mediated the anti-proliferative action of melatonin on ESCC cells.

CONCLUSIONS

Our findings elucidate that melatonin mitigates the HDAC7/β-catenin/c-Myc positive feedback loop and inhibits the USP10-maintained HDAC7 protein stability thus suppressing ESCC cell growth, and provides the reference for identifying biomarkers and therapeutic targets for ESCC.

Identifying and characterizing drug sensitivity-related lncRNA-TF-gene regulatory triplets

Recently, many studies have shown that lncRNA can mediate the regulation of TF-gene in drug sensitivity. However, there is still a lack of systematic identification of lncRNA-TF-gene regulatory triplets for drug sensitivity. In this study, we propose a novel analytic approach to systematically identify the lncRNA-TF-gene regulatory triplets related to the drug sensitivity by integrating transcriptome data and drug sensitivity data. Totally, 1570 drug sensitivity-related lncRNA-TF-gene triplets were identified, and 16 307 relationships were formed between drugs and triplets. Then, a comprehensive characterization was performed. Drug sensitivity-related triplets affect a variety of biological functions including drug response-related pathways. Phenotypic similarity analysis showed that the drugs with many shared triplets had high similarity in their two-dimensional structures and indications. In addition, Network analysis revealed the diverse regulation mechanism of lncRNAs in different drugs. Also, survival analysis indicated that lncRNA-TF-gene triplets related to the drug sensitivity could be candidate prognostic biomarkers for clinical applications. Next, using the random walk algorithm, the results of which we screen therapeutic drugs for patients across three cancer types showed high accuracy in the drug-cell line heterogeneity network based on the identified triplets. Besides, we developed a user-friendly web interface-DrugSETs (http://bio-bigdata.hrbmu.edu.cn/DrugSETs/) available to explore 1570 lncRNA-TF-gene triplets relevant with 282 drugs. It can also submit a patient’s expression profile to predict therapeutic drugs conveniently. In summary, our research may promote the study of lncRNAs in the drug resistance mechanism and improve the effectiveness of treatment.

Usefulness of Melatonin and Other Compounds as Antioxidants and Epidrugs in the Treatment of Head and Neck Cancer

Along with genetic mutations, aberrant epigenetic alterations are the initiators of head and neck cancer carcinogenesis. Currently, several drugs are being developed to correct these epigenetic alterations, known as epidrugs. Some compounds with an antioxidant effect have been shown to be effective in preventing these malignant lesions and in minimizing the complications derived from cytotoxic treatment. Furthermore, in vitro and in vivo studies show a promising role in the treatment of head and neck squamous cell carcinoma (HNSCC). This is the case of supplements with DNA methylation inhibitory function (DNMTi), such as epigallocatechin gallate, sulforaphane, and folic acid; histone deacetylase inhibitors (HDACi), such as sodium butyrate and melatonin or histone acetyltransferase inhibitors (HATi), such as curcumin. The objective of this review is to describe the role of some antioxidants and their epigenetic mechanism of action, with special emphasis on melatonin and butyric acid given their organic production, in the prevention and treatment of HNSCC.

Blockade of glutamine-dependent cell survival augments antitumor efficacy of CPI-613 in head and neck cancer

BACKGROUND

Alterations in metabolism are one of the emerging hallmarks of cancer cells and targeting dysregulated cancer metabolism provides a new approach to developing more selective therapeutics. However, insufficient blockade critical metabolic dependencies of cancer allows the development of metabolic bypasses, thus limiting therapeutic benefits.

METHODS

A series of head and neck squamous cell carcinoma (HNSCC) cell lines and animal models were used to determine the efficacy of CPI-613 and CB-839 when given alone or in combination. Glutaminase 1 (GLS1) depletion was achieved by lentiviral shRNAs. Cell viability and apoptosis were determined in HNSCC cells cultured in 2D culture dish and SeedEZ™ 3D scaffold. Molecular alterations were examined by Western blotting and immunohistochemistry. Metabolic changes were assessed by glucose uptake, lactate production, glutathione levels, and oxygen consumption rate.

RESULTS

We show here that HNSCC cells display strong addiction to glutamine. CPI-613, a novel lipoate analog, redirects cellular activity towards tumor-promoting glutaminolysis, leading to low anticancer efficacy in HNSCC cells. Mechanistically, CPI-613 inhibits the tricarboxylic acid cycle by blocking the enzyme activities of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, which upregulates GLS1 and eventually promotes the compensatory role of glutaminolysis in cancer cell survival. Most importantly, the addition of a GLS1 inhibitor CB-839 to CPI-613 treatment abrogates the metabolic dependency of HNSCC cells on glutamine, achieving a synergistic anticancer effect in glutamine-addicted HNSCC.

CONCLUSIONS

These findings uncover the critical role of GLS1-mediated glutaminolysis in CPI-613 treatment and suggest that the CB-839 and CPI-613 combination may potentiate synergistic anticancer activity for HNSCC therapeutic gain.

Using Patient-Derived Xenografts to Explore the Efficacy of Treating Head-and-Neck Squamous Cell Carcinoma With Anlotinib

Objective: The efficacy of anlotinib as a treatment for head-and-neck squamous cell carcinoma (HNSCC) has been little explored. Here, we used patient-derived xenografts (PDXs) to this end. Methods: Fresh tumor tissues of HNSCC patients were screened in terms of in vitro drug sensitivity using the MTT assay. Patient PDXs were used to confirm the anti-tumor effects of anlotinib in vivo. After the medication regimen was complete, the tumor volume changes in mice were calculated. Apoptosis was measured using the TUNEL assay. The cell proliferation and apoptosis levels of PDXs yielded data on the utility of anlotinib treatment in vivo. Results: Anlotinib suppressed the in vitro proliferation of nine tumor tissues by an average of 51.05 ± 13.74%. Anlotinib also significantly inhibited the growth of three PDXs in mice (tumor growth inhibition 79.02%). The expression levels of Ki-67 and proliferating cell nuclear antigen after anlotinib treatment were significantly lower than those in the controls. The negative and positive controls exhibited no and some apoptosis, respectively, whereas the anlotinib group evidenced extensive apoptosis. Conclusion: Anlotinib suppressed HNSCC growth in vitro and in vivo (by inhibiting cell proliferation and promoting apoptosis), suggesting that anlotinib can potentially treat HNSCC.