Mutation allele frequency threshold does not affect prognostic analysis using next-generation sequencing in oral squamous cell carcinoma.

BACKGROUND: With the development of sequencing technologies, there may be some disputes on sequencing analysis. The aim of this study was to investigate different allele frequency thresholds of mutations in targeted genes on prognostic analyses using a panel of cancer associated gene exons (CAGE) in oral squamous cell carcinoma (OSCC). METHODS: Forty-six patients were included in this study. Twelve genes were sequenced and analyzed using next-generation sequencing from formalin-fixed paraffin-embedded tissues. Allele frequency thresholds of 10, 5, and 3% were used for prognostic analyses. RESULTS: With a mean sequence depth of 3199-fold, 99% of CAGE were represented by at least 10 reads. Ninety-four non-synonymous (missense [70.2%], nonsense [11.7%], splice site [10.6%], and insertion/deletion [7.5%]) mutations were detected in 40 OSCC patients with an allele frequency threshold of 10%. TP53 (78.3%), NOTCH1 (30.4%), CASP8 (13.0%), CDKN2A (10.9%), and CDH1 (6.5%) were the most frequently mutated genes. Using allele frequency thresholds of 10, 5, and 3%, there were no significant differences in clinical outcomes between patients with non-synonymous mutations and wild type genotypes. CONCLUSIONS: TP53, NOTCH1, CASP8, CDKN2A, and CDH1 are the most frequently mutated genes in OSCC patients. The allele frequency threshold used in this study does not affect the results of clinical outcome analysis.

Elevated growth differentiating factor 15 expression predicts long-term benefit of docetaxel, cisplatin and 5-fluorouracil induction chemotherapy in patients with oral cancer.

Our previous phase 3 trial (NCT01542931) failed to demonstrate improved survival when docetaxel, cisplatin and 5-fluorouracil (TPF) induction chemotherapy was introduced prior to surgery and postoperative radiotherapy in patients with locally advanced oral squamous cell carcinoma (OSCC). The aim of the present study was to investigate the long-term predictive value of GDF15 expression for potential personalized treatment strategies in OSCC. A total of 256 patients with stage III/IVA OSCC from our phase 3 trial were enrolled in the present study. Immunohistochemical staining against GDF15 was performed in the biopsy samples from 230/256 patients. Kaplan-Meier analysis, followed by the log-rank test, and the Cox proportional hazards model were used for outcome analysis using the statistical SPSS 18.0 software package for Windows. Among the 230 patients, low GDF15 expression was detected in 68 patients and high GDF15 expression was detected in 162 patients. With a median follow-up period of 67 months, the patients with low GDF15 expression exhibited a higher survival rate than those with high GDF15 expression, including 5-year overall survival (73.4 vs. 57.7%; P=0.059), 5-year disease-free survival (64.5 vs. 49.2%; P=0.033), 5-year locoregional recurrence-free survival (66.0 vs. 51.5%; P=0.043) and 5-year distant metastasis-free survival (73.4 vs. 56.6%; P=0.038) rates. Furthermore, the cT3/4N0M0 patients with high GDF15 expression benefited significantly from TPF induction chemotherapy, including overall survival (HR=0.233; P=0.02), disease-free survival (HR=0.296; P=0.014), locoregional recurrence-free survival (HR=0.347; P=0.035) and distant metastasis-free survival (HR=0.212; P=0.013) rates. The results of the present study suggested that elevated GDF15 expression may be used as a long-term prognostic biomarker for poor clinical outcomes in patients with locally advanced OSCC. Elevated GDF15 expression in cT3/4N0M0 patients predicts significant long-term benefit of survival from TPF induction chemotherapy.

Stathmin is overexpressed and regulated by mutant p53 in oral squamous cell carcinoma.

BACKGROUND: The aim of this study was to investigate the oncogenic function and regulatory mechanism of stathmin in oral squamous cell carcinoma (OSCC). METHODS: Two-dimensional electrophoresis and liquid chromatography-tandem mass chromatography were applied to screen differentiated proteins during carcinogenesis in OSCC. Cell Counting Kit-8 (CCK-8) assays, colony formation, migration, flow cytometry, immunofluorescence and a xenograft model were used to detect the function of stathmin. The correlation between stathmin and p53 expression was analyzed using immunohistochemistry. Mutant/wild type p53 plasmids and small interfering RNA were used to examine the regulation of stathmin. Chromatin immunoprecipitation assays and luciferase assays were performed to detect the transcriptional activation of stathmin by p53. RESULTS: Overexpression of stathmin was screened and confirmed in OSCC patients and cell lines. Silencing expression of stathmin inhibited proliferation, colony formation and migration and promoted apoptosis. Poly ADP ribose polymerase (PARP) and cyclin-dependent kinase 1 (cdc2) were activated after silencing the expression of stathmin. Suppression of tumorigenicity was also confirmed in vivo. Mutant p53 transcriptionally activated the expression of stathmin in HN6 and HN13 cancer cells, but not in HN30 cells harboring wild type p53. CONCLUSIONS: These results suggest that stathmin acts as an oncogene and is transcriptionally regulated by mutant p53, but not by wild-type p53. Stathmin could be a potential anti-tumor therapeutic target in OSCC.

Mutant GDF15 presents a poor prognostic outcome for patients with oral squamous cell carcinoma.

PURPOSE: To investigate the mutation status of growth differentiation factor 15 (GDF15) in patients with oral squamous cell carcinoma (OSCC), as well as the prognostic value of missense GDF15 mutations. PATIENTS AND METHODS: Formalin-fixed paraffin-embedded biopsy samples from 46 OSCC patients were involved in this study. GDF15 and TP53 mutations were sequenced using the Ion Torrent Personal Genome Machine, GDF15 protein expression was detected using immunohistochemistry. Torrent Suite Software v.3.6, Integrative Genomics Viewer; v.2.3, statistical software SPSS18.0 for Windows were used for analysis. All hypothesis-generating tests were two-sided at a significance level of 0.05. RESULTS: Twenty-nine GDF15 mutations were identified in 19 out of 46 patients (41.3%), including eighteen missense mutations, two nonsense mutations and nine synonymous mutations. The patients with missense GDF15 mutations had poorer prognostic outcomes than those with wild-type GDF15, including overall survival (P = 0.035), disease-free survival (P = 0.032), locoregional recurrence-free survival (P = 0.015), and distant metastasis-free survival (P = 0.070). Missense GDF15mutations was an independent increased risk factor of overall survival (HR = 5.993, 95% CI:1.856-19.346, P = 0.003), disease-free survival (HR = 3.764, 95% CI:1.295-10.945, P = 0.015), locoregional recurrence-free survival (HR = 4.555, 95% CI:1.494-13.889, P = 0.008), and distant metastasis-free survival (HR = 4.420, 95% CI:1.145-13.433, P = 0.009). CONCLUSIONS: Patients with missense GDF15 mutations have significantly poorer outcomes than those with wild-type GDF15, missense GDF15 mutations could be used as an independent increased risk factor of poor prognosis in OSCC patients.

Targeting catalase but not peroxiredoxins enhances arsenic trioxide-induced apoptosis in K562 cells.

Despite considerable efficacy of arsenic trioxide (As2O3) in acute promyelocytic leukemia (APL) treatment, other non-APL leukemias, such as chronic myeloid leukemia (CML), are less sensitive to As2O3 treatment. However, the underlying mechanism is not well understood. Here we show that relative As2O3-resistant K562 cells have significantly lower ROS levels than As2O3-sensitive NB4 cells. We compared the expression of several antioxidant enzymes in these two cell lines and found that peroxiredoxin 1/2/6 and catalase are expressed at high levels in K562 cells. We further investigated the possible role of peroxirdoxin 1/2/6 and catalase in determining the cellular sensitivity to As2O3. Interestingly, knockdown of peroxiredoxin 1/2/6 did not increase the susceptibility of K562 cells to As2O3. On the contrary, knockdown of catalase markedly enhanced As2O3-induced apoptosis. In addition, we provide evidence that overexpression of BCR/ABL cannot increase the expression of PRDX 1/2/6 and catalase. The current study reveals that the functional role of antioxidant enzymes is cellular context and treatment agents dependent; targeting catalase may represent a novel strategy to improve the efficacy of As2O3 in CML treatment.