Xiaobing Chen

Quantitative Proteomic Analysis of Oral Brush Biopsies Identifies Secretory Leukocyte Protease Inhibitor as a Promising, Mechanism-Based Oral Cancer Biomarker

A decrease in the almost fifty percent mortality rate from oral cancer is needed urgently. Improvements in early diagnosis and more effective preventive treatments could affect such a decrease. Towards this end, we undertook for the first time an in-depth mass spectrometry-based quantitative shotgun proteomics study of non-invasively collected oral brush biopsies. Proteins isolated from brush biopsies from healthy normal tissue, oral premalignant lesion tissue (OPMLs), oral squamous cell carcinoma (OSCC) and matched control tissue were compared. In replicated proteomic datasets, the secretory leukocyte protease inhibitor (SLPI) protein stood out based on its decrease in abundance in both OPML and OSCC lesion tissues compared to healthy normal tissue. Western blotting in additional brushed biopsy samples confirmed a trend of gradual decreasing SLPI abundance between healthy normal and OPML tissue, with a larger decrease in OSCC lesion tissue. A similar SLPI decrease was observed in-vitro comparing model OPML and OSCC cell lines. In addition, exfoliated oral cells in patients’ whole saliva showed a loss of SLPI correlated with oral cancer progression. These results, combined with proteomics data indicating a decrease in SLPI in matched healthy control tissue from OSCC patients compared to tissue from healthy normal tissue, suggested a systemic decrease of SLPI in oral cells correlated with oral cancer development. Finally, in-vitro experiments showed that treatment with SLPI significantly decreased NF-kB activity in an OPML cell line. The findings indicate anti-inflammatory activity in OPML, supporting a mechanistic role of SLPI in OSCC progression and suggesting its potential for preventative treatment of at-risk oral lesions. Collectively, our results show for the first time the potential for SLPI as a mechanism-based, non-invasive biomarker of oral cancer progression with potential in preventive treatment.

The In Vitro and In Vivo Antitumor Effects of Clotrimazole on Oral Squamous Cell Carcinoma

Background Clotrimazole is an antifungal imidazole derivative showing anti- neoplastic effect in some tumors, but its anticancer potential is still unclear in oral squamous cell carcinoma (OSCC). The aim of this study was to evaluate the antitumor effect of clotrimazole, and to investigate the possible mechanism of clotrimazole-mediated antitumor activity in OSCC. Methodology In vitro experiments, the cell viability and clonogenic ability of three human OSCC cell lines CAL27, SCC25 and UM1 were detected after clotrimazole treatment by CCK8 assay and colony formation assay. Cell cycle progression and apoptosis were assessed by flow cytometry, and the involvement of several mediators of apoptosis was examined by western blot analysis. Then, the in vivo antitumor effect of clotrimazole was investigated in CAL27 xenograft model. Immunohistochemistry and western blot analysis were performed to determine the presence of apoptotic cells and the expression of Bcl-2 and Bax in tumors from mice treated with or without clotrimazole. Results Clotrimazole inhibited proliferation in all three OSCC cell lines in a dose-and time-dependent manner, and significantly reduced the colony formation of OSCC cells in vitro. Clotrimazole caused cell cycle arrest at the G0/G1 phase. In addition, clotrimazole induced apoptosis in OSCC cells, and significantly down-regulated the anti-apoptotic protein Bcl-2 and up-regulated the pro-apoptotic protein Bax. Notably, clotrimazole treatment inhibited OSCC tumor growth and cell proliferation in CAL27 xenograft model. Clotrimazole also markedly reduced Bcl-2 expression and increased the protein level of Bax in tumor tissues of xenograft model. Conclusion Our findings demonstrated a potent anticancer effect of clotrimazole by inducing cell cycle arrest and cellular apoptosis in OSCC.

Elevated autocrine chemokine ligand 18 expression promotes oral cancer cell growth and invasion via Akt activation

Chemokine (C-C motif) ligand 18 (CCL18) has been implicated in the pathogenesis and progression of various cancers; however, in oral squamous cell carcinoma (OSCC), the role of CCL18 is unknown. In this study, we found that CCL18 was overexpressed in primary OSCC tissues and was associated with an advanced clinical stage. CCL18 was found in both the cytoplasm and cell membrane of OSCC cells and was predominantly produced by cancer epithelial cells, as opposed to tumor-infiltrating macrophages. In vitro studies indicated that the effects of endogenous CCL18 on OSCC cell growth, migration, and invasion could be blocked by treatment with a neutralizing anti-CCL18 antibody or CCL18 knockdown, while exogenous recombinant CCL18 (rCCL18) rescued those effects. Akt was activated in rCCL18-treated OSCC cells, while LY294002, a pan-PI3K inhibitor, abolished both endogenous and exogenous CCL18-induced OSCC cell invasion. In vivo, LY294002 treatment attenuated rCCL18-induced OSCC cell growth. Our results indicate that CCL18 acts in an autocrine manner via Akt activation to stimulate OSCC cell growth and invasion during OSCC progression. They also provide a potential therapeutic target for the treatment of oral cancer.

Prognostic Value of Cancer Stem Cell Markers in Head and Neck Squamous Cell Carcinoma: a Meta-analysis

Bmi-1, CD133, Nanog and Oct-4 have been reported as cancer stem cell (CSC) markers in head and neck squamous cell carcinoma (HNSCC). However, the prognostic value of them in HNSCC remains controversial. Hence, this meta-analysis was conducted to access the association between the four CSC markers and survival outcome of HNSCC patients. A total of 22 articles with 27 studies met the inclusion criteria and the combined hazard ratio (HR) and 95% confidence intervals (95% CI) were calculated. Data analysis showed that high expression of CSC markers was associated with poor overall survival (OS) (HR = 1.93; 95% CI: 1.46–2.55, P < 0.001) and disease free survival (DFS) (HR = 4.78; 95% CI: 2.95–7.75, P < 0.001) but not disease specific survival (DSS) (HR = 1.17; 95% CI: 0.74–1.84, P = 0.50) of HNSCC patients. Subgroup analysis indicted that high expression of CD133 (HR = 2.33, 95%CI: 1.42–3.83, P < 0.001), Oct-4(HR = 2.10, 95%CI: 1.36–3.22, P = 0.007) and Nanog (HR = 2.49, 95%CI: 1.66–3.72, P < 0.001) could predict poor OS in HNSCC patients respectively whereas overexpression of Bmi-1 was not related to the reduced OS in HNSCC patients (HR = 1.32, 95%CI: 0.66–2.65, P = 0.43). Therefore, we concluded that CSC markers, especially CD133, Nanog and Oct-4, might be predictive factors in HNSCC patients.

IL-1β maintains the redox balance by regulating glutaredoxin 1 expression during oral carcinogenesis.

BACKGROUND Interleukin-1 beta (IL-1β) is a pleiotropic cancer-inflammation-linked cytokine which has been reported upregulated in many cancers. In our previous study, IL-1β was found to be one of the key node genes during oral malignant transformation, and glutaredoxin 1 (Grx1) was identified as one of the downstream genes of IL-1β in tumor microenvironment. Grx1 is ubiquitous oxidoreductase which is necessary for scavenging reactive oxygen species (ROS) and the intracellular redox balance maintenance. METHODS Tissues from different stages of mucosal malignant transformation were obtained from 4NQO-induced rat oral carcinogenesis model and human mucosa for Grx1 expression detection by immunohistochemical staining. The intracellular ROS levels and Grx1 mRNA level of oral squamous carcinoma cell CAL27 were detected after IL-1β treatment with or without pretreatment of IL-1Ra or NAC, respectively. The ROS levels were detected in Leti-si-IL-1β and Leti-si-NC CAL27 cells after IL-1β stimulation. The invasion and migration abilities of CAL27 cells were tested by transwell assay after IL-1β stimulation with or without pretreatment of IL-1Ra. RESULTS Grx1 expression was associated with the malignant transformation process in vivo. Exogenous IL-1β upregulated the intracellular ROS level and the expression of Grx1 in CAL27 cells, which could be counteracted by IL-1Ra. The intracellular ROS accumulation induced by exogenous IL-1β was responsible for the Grx1 upregulation. Endogenous IL-1β acted as a switch in regulating the ROS level by modulating Grx1 expression, which was involved in the invasion and migration of OSCC cells. CONCLUSIONS IL-1β finely orchestrated the redox balance during carcinogenesis by modulating Grx1 expression.

Proteomics-based investigation of multiple stages of OSCC development indicates that the inhibition of Trx-1 delays oral malignant transformation

The majority of cases of oral squamous cell carcinoma (OSCC) develop from oral potentially malignant disorders, which have been confirmed to be involved in chronic oxidative stimulation. However, no effective treatment approaches have been used to prevent the development of dysplasia into cancerous lesions thus far. In the present study, a well-established OSCC model was used to detect proteomics profiles at different stages during oral malignant transformation. Of the 15 proteins that were found to be upregulated in both the dysplasia and carcinoma stages, the oxidative stress-associated proteins, thioredoxin-1 (Trx-1), glutaredoxin-1 and peroxiredoxin-2 were note as the proteins with significant changes in expression Trx-1 was identified to be the most significantly upregulated protein in the precancerous stage. Validation experiments confirmed that Trx-1 was overex-pressed both in dysplasia and cancerous tissue samples, and the inhibition of Trx-1 was able to promote the apoptosis of OSCC cells under hypoxic conditions. Furthermore, the experimental application of a Trx-1-specific inhibitory agent in an animal model led to a lower cancerization rate and a delay in tumor formation. The possible mechanisms were associated with the increased apoptosis via a reactive oxygen species (ROS)-dependent pathway. Taken together, our findings indicate that Trx-1 may be an important target for delaying oral malignant transformation, which provides a novel therapeutic strategy for the prevention and treatment of OSCC.

The poor outcome of second primary oral squamous cell carcinoma is attributed to Bmi1 upregulation

Radiotherapy for nasopharyngeal carcinoma has been reported to cause second primary oral squamous cell carcinoma (s‐OSCC). The prognosis and pathologic characteristic of s‐OSCC are largely unknown. Bmi1 was associated with the repair of radiation‐induced DNA damage, suggesting its possible involvement in the pathologic process of s‐OSCC. Herein, we compared the prognosis between s‐OSCC and primary OSCC (p‐OSCC) and explored the involvement of Bmi1 in s‐OSCC development. In this retrospective study, s‐OSCC and p‐OSCC patients were matched by propensity scores. Their outcomes were compared by univariate and multivariate analyses. The expression of Bmi1 in s‐OSCC and p‐OSCC was detected by immunohistochemistry (IHC). Radiation‐induced Bmi1 alteration in early‐stage was explored in a rat model and HaCaT cells. After matching, 116 pairs of patients with highly balanced characteristics were included. In univariate analysis, the overall survival (OS), disease‐specific survival (DSS), and local recurrence‐free survival (LRFS) were poorer in s‐OSCC than in p‐OSCC (P < 0.05), while their regional metastasis‐free survival (RMFS) was parallel (P = 0.112). Multivariate analysis further revealed that radiotherapy history was an independent risk factor for OS, DSS, and LRFS (P < 0.05). IHC results showed that the positive rate of Bmi1 was higher in s‐OSCC (P = 0.0027). In a rat model of radiotherapy‐induced mucositis, Bmi1 upregulation was observed 8 days after irradiation. Consistently, Bmi1 was upregulated in HaCaT cells 1 h after irradiation, and its upregulation was in accord with X‐ray exposure duration. In conclusion, the prognosis of s‐OSCC is poorer as compared to p‐OSCC, which may be attributed to Bmi1 upregulation.

Stromal-epithelial lactate shuttle induced by tumor‑derived interleukin‑1β promotes cell proliferation in oral squamous cell carcinoma

Stromal-epithelial lactate shuttle is an essential process to support fast-growing tumor cells, however, the underlying mechanism remains ambiguous. Interleukin-1β (IL-1β), which is a key node gene in both stromal and epithelial cells of oral squamous cell carcinoma (OSCC), may participate in this metabolic reprogramming. In the present study, anaerobic glycolysis of cancer-associated fibroblasts (CAFs) was evaluated and the role of IL-1β in regulating stromal-epithelial lactate shuttle was determined. A co-culture system of primary fibroblasts and OSCC cell lines (CAL27, UM1 or SCC25) was created to investigate the stromal-epithelial interaction. α-smooth muscle actin (α-SMA) expression of fibroblasts, IL-1β expression and cell proliferation of OSCC cells, and a series of glycolytic genes were measured. Recombinant IL-1β treatment and IL-1β knockdown in UM1 cells were also used to evaluate the effect of IL-1β. Expression of α-SMA, glucose transporter 1, hexokinase 2, lactic dehydrogenase and mono-carboxylate transporter (MCT) 4 were significantly overexpressed in activated fibroblasts, while IL-1β and MCT1 were upregulated in OSCC cells, indicating enhanced glycolysis in cells of the tumor stroma and a lactate shuttle to the tumor cells. Furthermore, exogenous IL-1β induced fibroblasts to present similar expression profiles as that in the co-culture system. Silencing of IL-1β significantly abrogated the regulatory effect of UM1 cells on stromal glycolysis. Additionally, carboxy-fluorescein succinimidyl ester cell tracing indicated that OSCC cell proliferation was accelerated during co-cultivation with fibroblasts. These results indicate that tumor-derived IL-1β enhanced stromal glycolysis and induced one-way lactate flow from the tumor mesenchyme to transformed epithelium, which promotes OSCC proliferation.