Xiaojian Zhou

The NF-kappa B inhibitor, celastrol, could enhance the anti-cancer effect of gambogic acid on oral squamous cell carcinoma.

BackgroundGambogic acid (GA) is a major active ingredient of gamboge, a widely used traditional Chinese medicine that has been reported to be a potent cytotoxic agent against some malignant tumors. Many studies have shown that the NF-kappa B signaling pathway plays an important role in anti-apoptosis and the drug resistance of tumor cells during chemotherapy. In this study, the effects and mechanisms of GA and the NF-kappa B inhibitor celastrol on oral cancer cells were investigated.MethodsThree human oral squamous cell carcinoma cell lines, Tca8113, TSCC and NT, were treated with GA alone, celastrol alone or GA plus celastrol. Cytotoxicity was assessed by MTT assay. The rate of apoptosis was examined with annexin V/PI staining as well as transmission electronic microscopy in Tca8113 cells. The level of constitutive NF-kappa B activity in oral squamous cell carcinoma cell lines was determined by immunofluorescence assays and nuclear extracts and electrophoretic mobility shift assays (EMSAs) in vitro. To further investigate the role of NF-kappa B activity in GA and celastrol treatment in oral squamous cell carcinoma, we used the dominant negative mutant SR-IκBα to inhibit NF-kappa B activity and to observe its influence on the effect of GA.ResultsThe results showed that GA could inhibit the proliferation and induce the apoptosis of the oral squamous cell carcinoma cell lines and that the NF-kappa B pathway was simultaneously activated by GA treatment. The minimal cytotoxic dose of celastrol was able to effectively suppress the GA-induced NF-kappa B pathway activation. Following the combined treatment with GA and the minimal cytotoxic dose of celastrol or the dominant negative mutant SR-IκBα, proliferation was significantly inhibited, and the apoptotic rate of Tca8113 cells was significantly increased.ConclusionThe combination of GA and celastrol has a synergistic antitumor effect. The effect can be primarily attributed to apoptosis induced by a decrease in NF-kappa B pathway activation. The NF-kappa B signaling pathway plays an important role in this process. Therefore, combining GA and celastrol may be a promising modality for treating oral squamous cell carcinoma.

Correlation of NF-κB signal pathway with tumor metastasis of human head and neck squamous cell carcinoma

BackgroundNuclear factor-kappa B (NF-κB) signaling constitutes a key event in the multistep process of carcinogenesis, progression and treatment in many cancer types. However, the significance of NF-κB pathway for complex and tissue-specific aspects of head and neck cancer progression, such as invasion and metastasis, is less understood.MethodsThe expression of NF-κB p65 in squamous cell carcinoma of the head and neck (SCCHN) clinical specimens by immunohistochemistry. The role of NF-κB activity in head and neck squamous cell carcinoma was determined by western blot, reporter assay and EMSA analysis in vitro and metastasis assays in vivo in different metastatic potential tumor cells. Furthermore, the apoptosis rate and expression of metastasis-related protein such as MMP9 and VEGF were examined by Annexin V/PI staining and Western blot, respectively.ResultsA higher level of active nuclear-localized NF-κB was observed in the metastatic SCCHN specimens group (p < 0.01). The NF-κB activities of SCCHN cell lines with different metastatic potentials were then determined and in excellent agreement with results found in SCCHN specimens, highly metastatic SCCHN cell lines expressed high level of NF-κB activity. The treatment of highly metastatic SCCHN cells with NF-κB inhibitors reduced the in vitro cell invasion capacity of the cells without affecting the apoptotic rate. Additionally, the NF-κB inhibitors significantly inhibited the experimental lung metastasis of Tb cells and lymph node metastasis of TL cells in nude mice. Furthermore, the expression of metastasis-related proteins, such as matrix metalloproteinase 9 and vascular endothelial growth factor, was inhibited by pyrrolidine dithiocarbonate.ConclusionsThis study suggests that NF-κB activity significantly contributes to tumor hematologic and lymphatic metastases and may aid in the development of early detection methods or therapies targeting non-conventional molecular targets.

Identification of genes associated with cisplatin resistance in human oral squamous cell carcinoma cell line

BackgroundCisplatin is widely used for chemotherapy of head and neck squamous cell carcinoma. However, details of the molecular mechanism responsible for cisplatin resistance are still unclear. The aim of this study was to identify the expression of genes related to cisplatin resistance in oral squamous cell carcinoma cells.MethodsA cisplatin-resistant cell line, Tca/cisplatin, was established from a cisplatin-sensitive cell line, Tca8113, which was derived from moderately-differentiated tongue squamous cell carcinoma. Global gene expression in this resistant cell line and its sensitive parent cell line was analyzed using Affymetrix HG-U95Av2 microarrays. Candidate genes involved in DNA repair, the MAP pathway and cell cycle regulation were chosen to validate the microarray analysis results. Cell cycle distribution and apoptosis following cisplatin exposure were also investigated.ResultsCisplatin resistance in Tca/cisplatin cells was stable for two years in cisplatin-free culture medium. The IC50 for cisplatin in Tca/cisplatin was 6.5-fold higher than that in Tca8113. Microarray analysis identified 38 genes that were up-regulated and 25 that were down-regulated in this cell line. Some were novel candidates, while others are involved in well-characterized mechanisms that could be relevant to cisplatin resistance, such as RECQL for DNA repair and MAP2K6 in the MAP pathway; all the genes were further validated by Real-time PCR. The cell cycle-regulated genes CCND1 and CCND3 were involved in cisplatin resistance; 24-hour exposure to 10 μM cisplatin induced a marked S phase block in Tca/cisplatin cells but not in Tca8113 cells.ConclusionThe Tca8113 cell line and its stable drug-resistant variant Tca/cisplatin provided a useful model for identifying candidate genes responsible for the mechanism of cisplatin resistance in oral squamous cell carcinoma. Our data provide a useful basis for screening candidate targets for early diagnosis and further intervention in cisplatin resistance.

Inhibition of cyclin D1 expression by cyclin D1 shRNAs in human oral squamous cell carcinoma cells is associated with increased cisplatin chemosensitivity

Cyclin D1 is a well‐known cell cycle regulator. Recently, its pro‐survival function has been revealed in several tumors. Because increasing expression of cyclin D1 is a common event in oral squamous cell carcinoma (OSCC) and has been correlated with cisplatin resistance, we investigated if cyclin D1 inhibition could increase cisplatin chemosensitivity of OSCC. Five cyclin D1 shRNAs were prepared and 3 were selected for subsequent experiments. IC50 values for cisplatin were determined by an MTT assay. Cisplatin‐induced apoptosis and cell cycle block were investigated. A tumor transplantation model was generated to examine the cisplatin sensitivity of Tca/cisplatin after in vivo cyclin D1 silencing. The role of nuclear factor‐κB (NF‐κB) and cyclin‐dependent kinase 4 (CDK4) in cyclin D1‐mediated cisplatin resistance was also examined. The most effective shRNA resulted in 84.51% knockdown of the cyclin D1 protein level. After the transfection with the 2 most effective shRNAs, the cisplatin IC50 decreased from 5.88 μg/ml to 1.36 μg/ml and 2.47 μg/ml, although overexpression of cyclin D1 rendered OSCC cells more resistant to cisplatin treatment (IC50 increased from 6.43 μg/ml to 12.24 μg/ml). This decreasing IC50 was correlated with the down‐regulation of cisplatin‐induced NF‐κB activity in cyclin D1 knockdown cells, and was independent of CDK4 function. In vivo tumor transplantation models also confirmed a cisplatin‐sensitizing effect of cyclin D1 shRNA in OSCC. A TUNEL assay validated the increase in apoptosis as induced by cisplatin in cyclin D1 knockdown cells. Cyclin D1 may be an important target for future therapy in patients with OSCC.

Characteristics of a cancerous cell line, HIOEC-B(a)P-96, induced by benzo(a)pyrene from human immortalized oral epithelial cell line.

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in the oral and maxillofacial region. The mechanism of carcinogenesis of OSCC is still unclear. In vitro study on OSCC cell lines, especially derived from immortalized oral epithelial cells, is a very useful strategy to understand the mechanism of carcinogenesis. Based on our previous human immortalized oral epithelial cell (HIOEC) line, obtained from normal oral epithelial cells by transfection of HPV16 E6/E7 gene, a new cancerous cell line, HIOEC-B(a)P-96 (HB96), was established from the HIOEC by induction with benzo(a)pyrene. The characteristics of the HB96 cells such as cell morphology, ultrastructure, proliferation ability, invasion ability, and tumorigenesis were studied. The HB96 cells lost contact inhibition with uncontrolled cell division and obvious cell overlap, they were polygonal in shape and ununiform in size with increased ratio between nucleus and plasma. Increased proliferative ability and invasion ability were confirmed by the cell proliferation analysis and cell invasion assay, respectively. The tumorigenicity of well to moderately differentiated squamous cell carcinoma was confirmed in the nude mice experiments pathologically. Increased expression of HPV16 E6/E7 proteins and obvious correlation with decreased expression of p53 and Rb proteins was also confirmed by Western blotting. Thus, this HB96 cell line induced by benzo(a)pyrene from the HIOEC line is a useful tool to study the mechanism of carcinogenesis of OSCC in vitro for future genomic and proteomic analyses. It is also the first in vitro cancerous cell line of OSCC in China derived from immortalized oral epithelial cells.

Expression of growth differentiation factor 15 is positively correlated with histopathological malignant grade and in vitro cell proliferation in oral squamous cell carcinoma

Previously, we established an in vitro cellular carcinogenesis model of oral squamous cell carcinoma (OSCC) and expression microarray analysis showed that the gene encoding growth differentiation factor 15 (GDF15) was significantly upregulated in this model. In this study, we confirmed that expression of GDF15 was increased both at mRNA and protein levels in a panel of OSCC lines and clinical samples from primary OSCC patients. We also observed that expression of GDF15 was positively correlated with the malignancy of the disease: a higher level of GDF15 expression indicates a higher malignant grade of OSCC. Treatment of OSCC cell line (Tca3118) with siRNA against GDF15 significantly inhibited cellular proliferation and colony formation. Based on these observations, we conclude that GDF15 is a positive gene of OSCC development and progression and GDF15 can be used as an additional marker for histopathologic evaluation of OSCC differentiation.

Decreased expression of Annexin A1 correlates with pathologic differentiation grade in oral squamous cell carcinoma

Previously, we established an in vitro cellular carcinogenesis model of oral squamous cell carcinoma (OSCC), including the human immortalized oral epithelia cells (HIOECs) and its derived cancerous HB96 cells. In this study, comparative proteomic analysis identified that Annexin A1 was one of the significantly down-regulated genes in the cancerous HB96 cells. To investigate Annexin A1 down-regulation and its potential usefulness as a molecular marker in OSCC, we further screened Annexin A1 expressions with a panel of OSCC lines, and clinical samples of cancerous and the paired adjacent normal tissues from primary OSCC patients. By Western blot analysis and real-time PCR, we showed that both Annexin A1 mRNA and protein expressions decreased in OSCC cell lines except in two cell lines for the mRNA levels. Immunohistochemistry and real-time PCR also showed that both Annexin A1 mRNA and protein expressions decreased in the cancerous tissues from OSCC patients compared with those in the paired adjacent non-malignant epithelia. More importantly, both Annexin A1 mRNA and protein expressions negatively correlated with the pathologic differentiation grades of cancerous tissues. The lower Annexin A1 mRNA or protein expressions correlated with the poorer pathologic differentiation grades. These results suggest that decreased expression of Annexin A1 contributes to the cancerous progression of OSCC, and Annexin A1 may be a potential biomarker for pathologic differentiation grade of OSCC.

Increased expression of Annexin A2 in oral squamous cell carcinoma.

Previously, in vitro cellular carcinogenesis model of oral squamous cell carcinoma (OSCC) was established with a line of human immortalized oral epithelia cells (HIOECs), a line of cancerous HB96 cells, and another kind of cells (HB56 cells) at the early stage of carcinogenesis. In this study, comparative proteomic analysis identified a panel of differentially expressed proteins among these cells, and Annexin A2 shown as one of the significantly up-regulated proteins accompanying cellular transformation. Annexin A2 was further validated for its expression in the three kinds of cells and in the clinical samples of tumour tissues and their adjacent normal epithelia from primary OSCC patients. Western blot analysis and real-time PCR detected increased Annexin A2 protein and mRNA levels in cancerous HB56 and HB96 cells over HIOECs. Immunohistochemistry showed elevated Annexin A2 protein expression in tumour tissues over the adjacent non-malignant epithelia from OSCC patients; however, the mRNA levels between tumour and normal tissues did not change significantly. Interestingly, levels of Annexin A2 protein expression negatively correlated with the tumour differentiation grades. The results presented here suggest that Annexin A2 protein may play important roles in carcinogenesis of OSCC, and it may also serve as a candidate biomarker for pathologic differentiation grade of OSCC.

Establishment and characterization of an HPV16 E6/E7- expressing oral squamous cell carcinoma cell line with enhanced tumorigenicity

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in the oral and maxillofacial region. The mechanism of carcinogenesis of OSCC is still unclear. Based on the previous cell line, HIOEC-B(a)P-96 (HB96), which we obtained by HPV16 E6/E7-immortalized human oral epithelial cells (HIOEC) and benzo(a)pyrene inducement, we prepared a new HB-second generation cancer cell line (HB-2) by continuous passage. Its characteristics such as morphology, proliferation activity, karyotype, and tumorigenesis were studied. The HB-2 cells displayed uncontrolled cell division and lost contact inhibition leading to cell overlap. Cells were polygonal and unevenly shaped, with an increased nucleus versus plasma ratio. Increased proliferative activity was confirmed by MTT assays. The tumorigenicity was confirmed by tumor growth experiments in nude mice. Therefore, the HB-2 and HB96 cell lines are useful tools to study the mechanism of carcinogenesis of OSCC in vitro for future genomic and proteomic analyses.

Comparative proteomic analysis of differentially expressed proteins in an in vitro cellular carcinogenesis model of oral squamous cell carcinoma

In vitro cellular model is an important tool to be used to investigate the cellular events related to pathophysiological conditions in humans. We have developed an in vitro cellular carcinogenesis model of oral squamous cell carcinoma (OSCC). In this study, we performed comparative proteomic analysis using 2‐DE and LC‐tandem mass chromatography to separate and identify differentially expressed proteins. Forty‐five proteins were identified, including 24 proteins with decreased expression and 19 proteins with increased expression during carcinogenesis from immortalized oral epithelial cells to squamous cancerous cells. The identified known proteins were classified into three ontologies of cellular component, molecular function, and biological process. Further validation of five identified proteins (ANXA1, ANXA2, CTSB, KRT17, and S100A6) in the cellular carcinogenesis model and cancerous tissues from OSCC patients confirmed the comparative proteomic results. Moreover, Annexin A1 and A2 expression levels correlated with the pathological differentiation grade of cancerous tissues. Thus, this work provides a dynamic protein file of differentially expressed proteins in oral squamous carcinoma cells, which could provide clues to study the mechanisms of OSCC carcinogenesis and possibly be developed as potential biomarkers for clinical diagnosis or prognostic monitoring.