p38 Expression and Modulation of STAT3 Signaling in Oral Cancer

Cytotoxic effects of the cigarette smoke extract of heated tobacco products on human oral squamous cell carcinoma: the role of reactive oxygen species and CaMKK2

BACKGROUND

The increasing prevalence of heated tobacco products (HTPs) has heightened concerns regarding their potential health risks. Previous studies have demonstrated the toxicity of cigarette smoke extract (CSE) from traditional tobacco's mainstream smoke, even after the removal of nicotine and tar. Our study aimed to investigate the cytotoxicity of CSE derived from HTPs and traditional tobacco, with a particular focus on the role of reactive oxygen species (ROS) and intracellular Ca2+.

METHODS

A human oral squamous cell carcinoma (OSCC) cell line, HSC-3 was utilized. To prepare CSE, aerosols from HTPs (IQOS) and traditional tobacco products (1R6F reference cigarette) were collected into cell culture media. A cell viability assay, apoptosis assay, western blotting, and Fluo-4 assay were conducted. Changes in ROS levels were measured using electron spin resonance spectroscopy and the high-sensitivity 2',7'-dichlorofluorescein diacetate assay. We performed a knockdown of calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) by shRNA lentivirus in OSCC cells.

RESULTS

CSE from both HTPs and traditional tobacco exhibited cytotoxic effects in OSCC cells. Exposure to CSE from both sources led to an increase in intracellular Ca2+ concentration and induced p38 phosphorylation. Additionally, these extracts prompted cell apoptosis and heightened ROS levels. N-acetylcysteine (NAC) mitigated the cytotoxic effects and p38 phosphorylation. Furthermore, the knockdown of CaMKK2 in HSC-3 cells reduced cytotoxicity, ROS production, and p38 phosphorylation in response to CSE.

CONCLUSION

Our findings suggest that the CSE from both HTPs and traditional tobacco induce cytotoxicity. This toxicity is mediated by ROS, which are regulated through Ca2+ signaling and CaMKK2 pathways.

Induction of S arrest and apoptosis in human oral cancer cells by Rhinacanthin-C extracted from Rhinacanthus nasutus via modulating Akt and p38 signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

The search for effective herbal medicines for complementary treatments is on the rise due to the high incidence of recurrence and mortality rate in human oral cancer. Rhinacanthus nasutus KURZ., an annual herb found mostly in Southeast Asia including Thailand, has been wildly used as a traditional folk medicine for the treatment of several diseases including cancer. However, the anti-cancer effect of Rhinacanthin-C (Rh-C) as a major naphthoquinone compound found in R. nasutus and the underlying mechanism of its action on human oral cancer cells remain unknown.

AIM OF THE STUDY

To investigate the anti-cancer mechanism of Rh-C extracted from R. nasutus in human oral cancer cells.

MATERIALS AND METHODS

The anti-proliferative effect of Rh-C on human oral squamous cell carcinoma (HSC4) was determined and compared to normal oral cells (human gingival fibroblasts, HGF, and normal oral keratinocytes, NOK) using the SRB colorimetric method. The molecular mechanism of Rh-C was explored using flow cytometry, colorimetric assay, in vitro human topoisomerase II assay, and Western blotting.

RESULTS

Rh-C displayed a time- and concentration-dependent growth inhibition on HSC4 and was much less effective on both tested normal oral cells. Rh-C inhibited Akt phosphorylation whereas over-activated p38 MAPK phosphorylation in HSC4 but not in HGF. Rh-C also inhibited topoisomerase II activity. As a result, the cell cycle was arrested in S-phase as the expression of CDK1/2 and Cyclin A2 was decreased. Eventually, the induction of HSC4 cell apoptosis was mediated by increased caspase 3 activity.

CONCLUSIONS

Rh-C isolated from R. nasutus possesses anti-cancer properties on human oral cancer cells by causing the S arrest and the apoptotic induction via modulating Akt/p38 signaling pathways. The results provide molecular bases for further developing Rh-C as a potential drug candidate or a complementary treatment for oral cancer.

Network pharmacological analysis and experimental study of cucurbitacin B in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is a malignant tumor with a high incidence and poor prognosis. Cucurbitacin B (CuB) is a tetracyclic triterpenoid small-molecule compound extracted from plants, such as Cucurbitaceae and Brassicaceae, which has powerful anticancer effects. However, the effect and mechanism of CuB on OSCC remain unclear. Within the framework of the current study, network pharmacology was used to analyze the relationship between CuB and OSCC. The network pharmacology analysis showed that CuB and OSCC share 134 common targets; among them, PIK3R1, SRC, STAT3, AKT1, and MAPK1 are the key targets. The molecular docking analysis showed that CuB binds five target proteins. The results of the enrichment analysis showed that CuB exerted effects on OSCC through various pathways; of these pathways, PI3K-AKT was the most important pathway. The results of the in vitro cell experiments showed that CuB could inhibit the proliferation and migration of SCC25 and CAL27 cells, block the cell cycle in the G2 phase, induce cell apoptosis, and regulate the protein expression of the PI3K-AKT signaling pathway. The results of the in vivo animal experiments showed that CuB could inhibit 4NQO-induced oral cancer in mice. Therefore, network pharmacology, molecular docking, cell experiments, and animal experiments showed that CuB could play a role in OSCC by regulating multiple targets and pathways.

Methyltransferase-like 3-induced N6-methyladenosine upregulation promotes oral squamous cell carcinoma by through p38

BACKGROUND

Oral squamous cell carcinoma (OSCC), a main type of squamous cell cancer, is associated with considerable morbidity and mortality. Recent reports suggested methyltransferase-like 3 (METTL3)-mediated N6-methyladenosine (m6A) modification to be an essential regulator in the fate determination of stem cells. However, the functional significance of METTL3 in OSCC remains largely unknown.

METHODS

METTL3 expression was examined in OSCC patient samples, followed by correlation analysis against clinical tumor features. Functional assays, such as assessment of surface marker expression, colony forming, BrdU incorporation, tumor xenograft assay, and m6A dot blot, were conducted to study the impact of METTL3 knockdown (KD) in OSCC cells.

RESULTS

High METTL3 expression was positively correlated with more severe clinical features of OSCC tumors. METTL3 KD caused impairment of stem-like capacities in OSCC cells, such as tumorigenicity in vivo and colony-forming ability in vitro. Furthermore, METTL3-KD and cycloleucine, a methylation inhibitor, decreased m6A levels and down-regulated p38 expression in OSCC cells. On the contrary, the impaired cell proliferation capacity of OSCC cells after METTL3-KD was restored by exogenous expression of p38.

CONCLUSION

Our findings identified m6A methyltransferase METTL3 as a key element in the regulation of tumorigenesis in OSCC.

Thyroid Hormone Induces Oral Cancer Growth via the PD-L1-Dependent Signaling Pathway

Oral cancer is a fatal disease, and its incidence in Taiwan is increasing. Thyroid hormone as L-thyroxine (T₄) stimulates cancer cell proliferation via a receptor on integrin αvβ3 of plasma membranes. It also induces the expression of programmed death-ligand 1 (PD-L1) and cell proliferation in cancer cells. Thyroid hormone also activates β-catenin-dependent cell proliferation in cancer cells. However, the relationship between PD-L1 and cancer proliferation is not fully understood. In the current study, we investigated the role of inducible thyroid hormone-induced PD-L1-regulated gene expression and proliferation in oral cancer cells. Thyroxine bound to integrin αvβ3 to induce PD-L1 expressions via activation of ERK1/2 and signal transducer and activator of transcription 3 (STAT3). Inactivated STAT3 inhibited PD-L1 expression and nuclear PD-L1 accumulation. Inhibition of PD-L1 expression reduced β-catenin accumulation. Furthermore, nuclear PD-L1 formed a complex with nuclear proteins such as p300. Suppression PD-L1 expression by shRNA blocked not only expression of PD-L1 and β-catenin but also signal transduction, proliferative gene expressions, and cancer cell growth. In summary, thyroxine via integrin αvβ3 activated ERK1/2 and STAT3 to stimulate the PD-L1-dependent and β-catenin-related growth in oral cancer cells.

Cinnamomum zeylanicum Extract and its Bioactive Component Cinnamaldehyde Show Anti-Tumor Effects via Inhibition of Multiple Cellular Pathways

Cinnamomum zeylanicum is a tropical plant with traditional medicinal significance that possesses antimicrobial, antifungal, anti-parasitic, and anti-tumor properties. Here, we have elucidated the anti-tumor effects of Cinnamomum zeylanicum extract (CZE) and its bioactive compound cinnamaldehyde (CIN) on oral cancer and elucidated underlying molecular mechanisms. Anti-tumor activities of CZE and CIN were demonstrated by various in vitro experiments on oral cancer cells (SCC-4, SCC-9, SCC-25). The cell proliferation, growth, cell cycle arrest, apoptosis, and autophagy were analyzed by MTT, clonogenic assay, propidium iodide, annexin-V-PI, DAPI, and acridine orange staining, respectively. The binding affinity of CIN towards dihydrofolate reductase and p38-MAP kinase alpha was analyzed by molecular docking. Western blot assay was performed to assess the alteration in the expression of various proteins. CZE and CIN treatment significantly inhibited the growth and proliferation of oral cancer cells in a dose-dependent manner. These treatments further induced apoptosis, cell cycle arrest, and autophagy. CZE and CIN inhibited the invasion and cytoplasmic translocation of NF-κB in these cell lines. CIN showed a high affinity to MAP kinase P38 alpha and dihydrofolate reductase with binding affinities of −6.8 and −5.9 kcal/mol, respectively. The cancer cells showed a decreased expression of various PI3k-AKT-mTOR pathways related to VEGF, COX-2, Bcl-2, NF-κB, and proteins post-treatment.

Epigenetic Deregulation of Protein Tyrosine Kinase 6 Promotes Carcinogenesis of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) accounts for over 90% of oral cancers and causes considerable morbidity and mortality. Epigenetic deregulation is a common mechanism underlying carcinogenesis. DNA methylation deregulation is the epigenetic change observed during the transformation of normal cells to precancerous and eventually cancer cells. This study investigated the DNA methylation patterns of PTK6 during the development of OSCC. Bisulfite genomic DNA sequencing was performed to determine the PTK6 methylation level. OSCC animal models were established to examine changes in PTK6 expression in the different stages of OSCC development. The DNA methylation of PTK6 was decreased during the development of OSCC. The mRNA and protein expression of PTK6 was increased in OSCC cell lines compared with human normal oral keratinocytes. In mice, the methylation level of PTK6 decreased after treatment with 4-nitroquinoline 1-oxide and arecoline, and the mRNA and protein expression of PTK6 was increased. PTK6 hypomethylation can be a diagnostic marker of OSCC. Upregulation of PTK6 promoted the proliferation, migration, and invasion of OSCC cells. PTK6 promoted carcinogenesis and metastasis by increasing STAT3 phosphorylation and ZEB1 expression. The epigenetic deregulation of PTK6 can serve as a biomarker for the early detection of OSCC and as a treatment target.

Modified citrus pectin prevents isoproterenol-induced cardiac hypertrophy associated with p38 signalling and TLR4/JAK/STAT3 pathway

Modified citrus pectin (MCP) is a specific inhibitor of galectin-3 (Gal-3) that is regarded as a new biomarker of cardiac hypertrophy, but its effect is unclear. The aim of this study is to investigate the role and mechanism of MCP in isoproterenol (ISO)-induced cardiac hypertrophy. Rats were injected with ISO to induce cardiac hypertrophy and treated with MCP. Cardiac function was detected by ECG and echocardiography. Pathomorphological changes were evaluated by the haematoxylin eosin (H&E) and wheat germ agglutinin (WGA) staining. The hypertrophy-related genes for atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (β-MHC), and the associated signal molecules were analysed by qRT-PCR and western blotting. The results show that MCP prevented cardiac hypertrophy and ameliorated cardiac dysfunction and structural disorder. MCP also decreased the levels of ANP, BNP, and β-MHC and inhibited the expression of Gal-3 and Toll-like receptor 4 (TLR4). Additionally, MCP blocked the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), but it promoted the phosphorylation of p38. Thus, MCP prevented ISO-induced cardiac hypertrophy by activating p38 signalling and inhibiting the Gal-3/TLR4/JAK2/STAT3 pathway.

Variation of PPARG Expression in Chemotherapy-Sensitive Patients of Hypopharyngeal Squamous Cell Carcinoma

Our previous study showed that the upregulation of peroxisome proliferator-activated receptor gamma (PPARG) could promote chemosensitivity of hypopharyngeal squamous cell carcinoma (HSCC) in chemotherapeutic treatments. Here, we acquired two more independent expression data of PPARG to validate the expression levels of PPARG in chemotherapy-sensitive patients (CSP) and its individualized variations compared to chemotherapy-non-sensitive patients (CNSP). Our results showed that overall PPARG expression was mildly downregulated (log fold change = −0.55; p value = 0.42; overexpression in three CSPs and reduced expression in four CSPs), which was not consistent with previous results (log fold change = 0.50; p = 0.22; overexpression in nine CSPs and reduced expression in three CSPs). Both studies indicated that PPARG expression variation was significantly associated with the Tumor-Node-Metastasis (TNM) stage (p = 7.45e − 7 and 6.50e − 4, for the first and second studies, respectively), which was used as one of the predictors of chemosensitivity. The new dataset analysis revealed 51 genes with significant gene expression changes in CSPs (LFC > 1 or <-1; p value < 0.01), and two of them (TMEM45A and RBP1) demonstrated strong coexpression with PPARG (Pearson correlation coefficient > 0.6 or <-0.6). There were 21 significant genes in the data from the first study, with no significant association with PPARG and no overlap with the 51 genes revealed in this study. Our results support the connection between PPARG and chemosensitivity in HSCC tumor cells. However, significant PPARG variation exists in CSPs, which may be influenced by multiple factors, including the TNM stage.

Inhibition of Aurora Kinase A by Alisertib Reduces Cell Proliferation and Induces Apoptosis and Autophagy in HuH-6 Human Hepatoblastoma Cells

Purpose

Aurora kinase A (AURKA), which belongs to the serine/threonine protein kinase family, has been identified as a key driver of the genesis and progression of diverse tumors. The aim of this study was to determine the clinical significance of AURKA in patients with hepatoblastoma (HB) and the effect of inhibiting AURKA in the HB cell line HuH-6.

Methods

The expression of AURKA in HB tissue and adjacent normal liver tissue was detected by immunohistochemistry. Then, statistical analysis was performed to evaluate the association between AURKA expression and the clinicopathological characteristics of HB. The effect of AURKA knockdown on cell viability was assessed by CCK-8 assay. EdU and CCK-8 assays, Western blotting, flow cytometry, and transmission electron microscopy (TEM) were used to examine the effect of alisertib (ALS), a selective AURKA small-molecule inhibitor, on the cell cycle, proliferation, apoptosis, and autophagy in HuH-6 human hepatoblastoma cells.

Results

The expression of AURKA was significantly higher in HB tissue than in adjacent normal tissue. Furthermore, high AURKA expression was associated with advanced Children’s Oncology Group (COG) stage and tumor metastasis of HB. In vitro, AURKA knockdown significantly reduced the viability of HuH-6 cells, while ALS treatment significantly suppressed HuH-6 cell proliferation and induced G1-phase cell cycle arrest by reducing cyclin-D1 expression. Moreover, ALS promoted apoptosis and autophagy by decreasing the activity of p38 MAPK in HuH-6 cells.

Conclusion

High expression of AURKA is a potential predictor of poor prognosis in HB patients. AURKA knockdown reduced the viability of HuH-6 cells, and ALS treatment inhibited cell proliferation and induced apoptosis and autophagy via the p38 MAPK signaling pathway. Our results suggest that AURKA may be a novel therapeutic target and ALS a potential therapeutic drug for the treatment of HB.

Ursolic acid induces apoptosis and autophagy in oral cancer cells

Oral squamous cell carcinoma (OSCC) is the fifth common cause of cancer mortality in Taiwan with high incidence and recurrence and needs new therapeutic strategies. In this study, ursolic acid (UA), a triterpenoid, was examined the antitumor potency in OSCC cells. Our results showed that UA inhibited the proliferation of OSCC cells in a dose- and time-dependent manner in both Ca922 and SCC2095 oral cancer cells. UA induced caspase-dependent apoptosis accompanied with the modulation of various biological biomarkers including downregulating Akt/mTOR/NF-κB signaling, ERK, and p38. In addition, UA inhibited angiogenesis as evidenced by abrogation of migration/invasion and blocking MMP-2 secretion in Ca922 cells. Interestingly, UA induced autophagy in OSCC cells, as manifested by LC3B-II conversion and increased p62 expression and accumulation of autophagosomes. Inhibition by autophagy inhibitor enhanced UA-mediated apoptosis in Ca922 cells. The experiment provides a rationale for using triterpenoid in the treatment of OSCC.

Contribution of p38 MAPK Pathway to Norcantharidin-Induced Programmed Cell Death in Human Oral Squamous Cell Carcinoma

Norcantharidin (NCTD), a demethylated analog of cantharidin isolated from blister beetles, has been used as a promising anticancer agent; however, the underlying function of NCTD against human oral squamous cell carcinoma (OSCC) has not been fully understood. Here, this study was aimed to investigate the apoptotic effect and molecular targets of NCTD in human OSCC in vitro and in vivo. The anticancer effects of NCTD and its related molecular mechanisms were evaluated by trypan blue exclusion assay, live/dead assay, western blotting, 4-6-Diamidino-2-Phenylindole (DAPI) staining, flow cytometric analysis, Terminal Deoxynucleotidyl Transferase dUTP Nick end Labeling (TUNEL) assay, and immunohistochemistry. NCTD significantly inhibited cell growth and increased the number of dead cells in HSC-3 and HN22 cell lines. It induced the following apoptotic phenomena: (1) the cleavages of poly (ADP-ribose) polymerase and casepase-3; (2) increase in apoptotic morphological changes (nuclear condensation and fragmentation); (3) increase in annexin V-positive cells or sub-G₁ population of cells. NCTD significantly activated the p38 mitogen-activated protein kinase (MAPK) pathway but inactivated the signal transducer and activator of transcription (STAT)3 pathway. A p38 MAPK inhibitor (SB203580) partially attenuated NCTD-induced programmed cell death (apoptosis) in both cell lines, whereas ectopic overexpression of STAT3 did not affect it. NCTD strongly suppressed tumor growth in the tumor xenograft bearing HSC-3 cells, and the number of TUNEL-positive cells increased in NCTD-treated tumor tissues. In addition, NCTD did not cause any histopathological changes in the liver nor the kidney. NCTD induced programmed cell death via the activation of p38 MAPK in OSCC. Therefore, these results suggest that NCTD could be a potential anticancer drug candidate for the treatment of OSCC.

Bone Metastasis Phenotype and Growth Undergo Regulation by Micro-Environment Stimuli: Efficacy of Early Therapy with HGF or TGFβ1-Type I Receptor Blockade

Hepatocyte growth factor (HGF) and transforming growth factor β1 (TGFβ1) are biological stimuli of the micro-environment which affect bone metastasis phenotype through transcription factors, but their influence on the growth is scarcely known. In a xenograft model prepared with 1833 bone metastatic cells, derived from breast carcinoma cells, we evaluated mice survival and Twist and Snail expression and localization after competitive inhibition of HGF with NK4, or after blockade of TGFβ1-type I receptor (RI) with SB431542: in the latter condition HGF was also measured. To explain the in vivo data, in 1833 cells treated with SB431542 plus TGFβ1 we measured HGF formation and the transduction pathway involved. Altogether, HGF seemed relevant for bone-metastatic growth, being hampered by NK4 treatment, which decreased Twist more than Snail in the metastasis bulk. TGFβ1-RI blockade enhanced HGF in metastasis and adjacent bone marrow, while reducing prevalently Snail expression at the front and bulk of bone metastasis. The HGF accumulation in 1833 cells depended on an auxiliary signaling pathway, triggered by TGFβ1 under SB431542, which interfered in the transcription of HGF activator inhibitor type 1 (HAI-1) downstream of TGFβ-activated kinase 1 (TAK1): HGF stimulated Twist transactivation. In conclusion, the impairment of initial outgrowth with NK4 seemed therapeutically promising more than SB431542 chemotherapy; a functional correlation between Twist and Snail in bone metastasis seemed to be influenced by the biological stimuli of the micro-environment, and the targeting of these phenotype biomarkers might inhibit metastasis plasticity and colonization, even if it would be necessary to consider the changes of HGF levels in bone metastases undergoing TGFβ1-RI blockade.