Eugenol Induces Apoptosis in Tongue Squamous Carcinoma Cells by Mediating the Expression of Bcl-2 Family

Head and neck squamous cell carcinoma is highly aggressive type of cancer for which the available treatment often causes patients severe side effects. Eugenol (Eug) is the major active constituent of clove essential oil and is known to possess antitumor properties. The present study aimed to assess the in vitro cytotoxicity of eugenol in SCC-4, tongue squamous carcinoma cells, and also in HGF, human gingival fibroblasts. Both cell lines were treated with five concentrations of Eug (0.1-1 mM) for 72 h. Cellular viability was assessed, followed by cellular morphological evaluation and by staining of the nuclei and cytoskeleton. RT-PCR was conducted in order to find the effect eugenol had on the expression on Bad, Bax, and Bcl-2 genes. Eugenol induced a dose-dependent decrease in viability in both cell lines, with the SCC-4 cells being significantly more affected. HGF cells detached from the plate at the highest concentrations used, while SCC-4 cells changed their morphology in a dose-dependent manner, with rounding, floating cells, and confluency loss being observed. Apoptotic-like signs such as chromatin and actin filaments condensation were clearly seen in SCC-4 cells, while RT-PCR revealed a significantly increased expression of pro-apoptotic genes Bax and Bad. Therefore, eugenol exerts its cytotoxic effect in tongue squamous cell carcinoma through inducing apoptosis.

Enforced C-Src Activation Causes Compartmental Dysregulation of PI3K and PTEN Molecules in Lipid Rafts of Tongue Squamous Carcinoma Cells by Attenuating Rac1-Akt-GLUT-1-Mediated Sphingolipid Synthesis

Pharmacologic intervention to affect the membrane lipid homeostasis of lipid rafts is a potent therapeutic strategy for cancer. Here we showed that gallic acid (GA) caused the complex formation of inactive Ras-related C3 botulinum toxin substrate 1 (Rac1)-phospho (p)-casein kinase 2 α (CK2α) (Tyr 255) in human tongue squamous carcinoma (TSC) cells, which disturbed the lipid raft membrane-targeting of phosphatidylinositol 3-kinase (PI3K)-Rac1-protein kinase B (Akt) signal molecules by inducing the association of p110α-free p85α with unphosphorylated phosphatase tensin homolog deleted on chromosome 10 (PTEN) in lipid rafts. The effects on induction of inactive Rac1-p-CK2α (Tyr 255) complex formation and attenuation of p-Akt (Ser 473), GTP-Rac1, glucose transporter-1 (GLUT-1) lipid raft membrane-targeting, and cell invasive activity by GA were counteracted either by CK2α short hairpin RNA or cellular-Src (c-Src) inhibitor PP1. PP1 treatment, GLUT-1 or constitutively active Rac1 ectopic-expression blocked GA-induced decreases in cellular glucose, sphingolipid and cholesterol of lipid raft membranes, p85α-p110α-GTP-Rac1 complexes, glucosylceramide synthase activity and increase in ceramide and p110α-free p85α-PTEN complex levels of lipid raft membranes, which reversed the inhibition on matrix metalloproteinase (MMP)-2/-9-mediated cell invasion induced by GA. Using transient ectopic expression of nuclear factor-kappa B (NF-κB) p65, MMP-2/-9 promoter-driven luciferase, and NF-κB-dependent luciferase reporter genes and NF-κB specific inhibitors or Rac1 specific inhibitor NSC23766, we confirmed that an attenuation of Rac1 activity by GA confers inhibition of NF-κB-mediated MMP-2/-9 expression and cell invasion. In conclusion, GA-induced c-Src activation is a key inductive event for the formation of inactive Rac1-p-CK2α (Tyr 255) complexes, which disturbed lipid raft compartment of PI3K and PTEN molecules by impairing Akt-regulated GLUT-1-mediated sphingolipid synthesis, and finally resulting in inhibition of TSC cell invasion.

Stromal interaction molecule 1 regulates growth, cell cycle, and apoptosis of human tongue squamous carcinoma cells

Oral tongue squamous cell carcinoma (OTSCC) is the most common type of oral carcinomas. However, the molecular mechanism by which OTSCC developed is not fully identified. Stromal interaction molecule 1 (STIM1) is a transmembrane protein, mainly located in the endoplasmic reticulum (ER). STIM1 is involved in several types of cancers. Here, we report that STIM1 contributes to the development of human OTSCC. We knocked down STIM1 in OTSCC cell line Tca-8113 with lentivirus-mediated shRNA and found that STIM1 knockdown repressed the proliferation of Tca-8113 cells. In addition, we also showed that STIM1 deficiency reduced colony number of Tca-8113 cells. Knockdown of STIM1 repressed cells to enter M phase of cell cycle and induced cellular apoptosis. Furthermore, we performed microarray and bioinformatics analysis and found that STIM1 was associated with p53 and MAPK pathways, which may contribute to the effects of STIM1 on cell growth, cell cycle, and apoptosis. Finally, we confirmed that STIM1 controlled the expression of MDM2, cyclin-dependent kinase 4 (CDK4), and growth arrest and DNA damage inducible α (GADD45A) in OTSCC cells. In conclusion, we provide evidence that STIM1 contributes to the development of OTSCC partially through regulating p53 and MAPK pathways to promote cell cycle and survival.

Role of CD133+ cells in tongue squamous carcinomas: Characteristics of 'stemness' in vivo and in vitro

The objective of the present study was to determine the ‘stemness’ characteristics of CD133⁺ cells (harvested from the squamous cell tongue carcinoma Tca-8113 cell line) in vitro and to observe the tumourigenicity of the CD133⁺ cells in the bodies of NOD/SCID mice. Single cells from the Tca-8113 cell line were observed for multiplication capacity in vitro. The suspending and pelletizing phenomena of Tca-8113 cells in vitro were also observed, and the expression of CD133 in squamous cell carcinoma of the tongue was measured. The CD133⁺ cells from the Tca-8113 cell line were purified, and their multiplication capacity and differentiation potency were observed. The NOD/SCID mouse model was established, and the tumourigenicity of the CD133⁺ cells was determined. The Tca-8113 cells were observed to emerge in the form of suspending tumour spheres in squamous cell carcinoma of the tongue. Monoplasts with sustainable multiplication capacity accounted for ~5.32% of the spheres, and 0.95% of the CD133⁺ cells were expressed in squamous cell carcinoma of the tongue, with stronger multiplication capacity and differentiation potency in vitro. Stronger tumourigenicity was also observed in the bodies of the NOD/SCID mice. CD133^– cells exhibited a multiplication capacity to a certain extent. Overall, the CD133⁺ cells in squamous cell carcinoma of the tongue are characterised by relatively strong tumourigenicity capacity in vivo and in vitro. To a certain extent, these CD133⁺ cells demonstrate the characteristics of ‘stemness’.

[Application of fluorescence probe marked by quantum dots to detect early submandibular lymph node metastasis in a nude mouse model]

OBJECTIVE

A fluorescence probe marked with a specific angle protein antibody by using quantum dots QDs605-CK (AE1/AE3) was utilized to detect metastasis and micrometastasis rates of early submandibular lymph node metastatic carcinoma in a nude mouse model. The method was compared with traditional immunohistochemistry (IHC) staining and hematine-eosin (HE) staining to explore a new method for early diagnosis and treatment of tongue squamous cell carcinoma.

METHODS

Human tongue Tca8113 cells were cultured and inoculated in 18 nude mice tongue body tissues (except the midline) to establish submandibular lymph node metastasis in tumor-bearing nude mice models. The nude mice were sacrificed, and the mandibular lymph node was dissected after injecting tumor cells for six weeks. One lymph node was divided into two parts: one was used to create a serial section embedded by paraffin then detected in HE staining and IHC staining; the other was immediately frozen in liquid nitrogen and detected using the fluorescence probe marked with a specific angle protein antibody by using quantum dots. Lymph node metastasis and micrometastases rates were calculated.

RESULTS

The rates of metastasis in the submandibular lymph node via quantum dot immunofluorescence staining, IHC staining, and HE staining showed positive values of 66.7%, 61.1%, and 27.8%, respectively. The micrometastases rates were 38.9% and 33.3% via quantum dot immunofluorescence staining and IHC staining, respectively. The positive rates of detecting lymph nodes metastasis with quantum dot labeled keratin CK (AEl/AE3) immunofluorescence and keratin CK (AE1/AE3) IHC staining were higher than that of conventional HE staining ('=6.379, P<0.05). The two methods showed no statistical difference (chi2 = 0.120, P > 0.05).

CONCLUSION

Quantum dots fluorescent probe marked with the angle protein antibody CK (AE1/ AE3) can precisely locate the submandibular lymph node metastasis tumor cell of the nude mice tongue squamous cell carcinoma, and the emitted red fluorescence showed strong specificity, high resolution, and a clear background. The method could be utilized to detect submandibular lymph node metastasis and micrometastasis of tongue squamous cell carcinoma in nude mice.