Raymond Wai-Man Ng

Mature miR-184 as Potential Oncogenic microRNA of Squamous Cell Carcinoma of Tongue

Purpose: The aim of this study was to evaluate the microRNA expression patterns in squamous cell carcinoma (SCC) of the tongue. Experimental Design: Expression levels of 156 human mature microRNAs were examined using real-time quantitative PCR (Taq Man MicroRNA Assays; Human Panel) on laser microdissected cells of 4 tongue carcinomas and paired normal tissues. Expression of mature miR-184 was further validated in 20 paired tongue SCC and the normal tissues. Potential oncogenic functions of miR-184 were evaluated in tongue SCC cell lines (Cal27, HN21B, and HN96) with miR-184 inhibitor. Plasma miR-184 levels were evaluated using real-time quantitative PCR. Results: Using 3-fold expression difference as a cutoff level, we identified 24 up-regulated mature miRNAs including miR-184, miR-34c, miR-137, miR-372, miR-124a, miR-21, miR-124b, miR-31, miR-128a, miR-34b, miR-154, miR-197, miR-132, miR-147, miR-325, miR-181c, miR-198, miR-155, miR-30a-3p, miR-338, miR-17-5p, miR-104, miR-134, and miR-213; and 13 down-regulated mature miRNAs including miR-133a, miR-99a, miR-194, miR-133b, miR-219, miR-100, miR-125b, miR-26b, miR-138, miR-149, miR-195, miR-107, and miR-139. Overexpression of miR-184 was further validated in 20 paired tongue SCC and normal tissues (P = 0.002). Inhibition of miR-184 in tongue SCC cell lines could reduce cell proliferation rate. Down-regulation of c-Myc was observed in two cell lines in response to miR-184 inhibitor. Suppressing miR-184 could induce apoptosis in all three cell lines. Plasma miR-184 levels were significantly higher in tongue SCC patients in comparison with normal individuals, and the levels were significantly reduced after surgical removal of the primary tumors. Conclusions: Overexpression of miR-184 might play an oncogenic role in the antiapoptotic and proliferative processes of tongue SCC. In addition, plasma miR-184 levels were associated with the presence of primary tumor. Further studies on the aberrantly expressed miRNAs in tongue SCC as well as using plasma miRNAs as novel tumor markers are warranted.

Identification of pyruvate kinase type M2 as potential oncoprotein in squamous cell carcinoma of tongue through microRNA profiling

MicroRNAs (miRNAs) are noncoding RNAs with specific regulatory role in gene expression. Recent reports suggested their involvement in human malignancies. Currently, there is no information concerning miRNA expression and functions in squamous cell carcinoma (SCC) of tongue. In this study, we evaluated the expression patterns of 156 mature miRNAs in tongue SCC using Taqman‐based microRNA assays. Of these 156 miRNAs, miR‐133a and miR‐133b were significantly reduced in tongue SCC cells in comparison with the paired normal epithelial cells. Tongue SCC cell lines transfected with miR‐133a and miR‐133b precursors displayed reduction in proliferation rate. In addition, the number of apoptotic cells was increased in response to the introduction of precursors. Computational target gene prediction suggested that both miR‐133a and miR‐133b are targeting transcript of pyruvate kinase type M2 (PKM2), a potential oncogene in solid cancers. In tongue SCC cell lines, PKM2 expression was reduced in response to miR‐133a and miR‐133b precursors transfection. Immunohistochemical staining results of tongue SCC tissues suggested that PKM2 was overexpressed in tongue SCC and was associated with the downregulation of miR‐133a and miR‐133b. Our results suggested that aberrant reduction of miR‐133a and miR‐133b was associated with the dysregulation of PKM2 in SCC of tongue.

Cooperation of Yeast Peroxiredoxins Tsa1p and Tsa2p in the Cellular Defense against Oxidative and Nitrosative Stress

Peroxiredoxins are a family of antioxidant enzymes conserved from bacteria to humans. In Saccharomyces cerevisiae, there exist five peroxiredoxins, among which Tsa2p shares striking homology with the well described Tsa1p but has not been extensively studied. Here we report on the functional characterization of yeast tsa2Δ mutants and the comparison ofTSA1 with TSA2. The tsa2Δ andtsa1Δ tsa2Δ cells grew normally under aerobic conditions. However, the tsa1Δtsa2Δ mutant yeast was more susceptible to oxidants than either tsa1Δ or tsa2Δ cells. Notably, thetsa1Δ tsa2Δ yeast was also hypersensitive to peroxynitrite and sodium nitroprusside. This phenotype was rescued by the expression of either the TSA1 or TSA2gene. The demonstration of a peroxynitrite reductase activity of Tsa2pin vitro points to a pivotal role for peroxiredoxins in the protection against nitrosative stress. In yeast cells, Tsa1p and Tsa2p exhibited comparable antioxidant activity. While the basal expression level of TSA1 was significantly higher than that ofTSA2, the transcription of TSA2 was stimulated more potently by various oxidants. In addition, TSA2 was activated in tsa1Δ cells in a Yap1p-dependent manner. Taken together, our findings implicate the cooperation of Tsa1p and Tsa2p in the cellular defense against reactive oxygen and nitrogen species.

Prospective randomized study of selective neck dissection versus observation for N0 neck of early tongue carcinoma

There are controversies on the benefits of elective neck dissection (END) for oral tongue carcinoma.

Multiple dysregulated pathways in nasopharyngeal carcinoma revealed by gene expression profiling

Gene expression profiling was conducted using primary human nasopharyngeal carcinoma (NPC) biopsy samples to improve the understanding of the molecular pathways defining NPC and to identify novel potential therapeutic targets. RNA samples were extracted from 36 patients suspected to have NPC and hybridized onto the Affymetrix U133A chip. NPC was diagnosed in 19 patients, 11 had lymphoid hyperplasia (LH), and 6 were “normal” biopsies. Clinical stages for these NPC patients ranged from I–IV, including one M1. All NPC patients (except the M1) were treated with curative intent, which included radiotherapy alone (4 patients), or combined with chemotherapy (14 patients). Unsupervised clustering demonstrated a distinct NPC expression pattern, compared to normal biopsies. Subsequent Significance Analysis of Microarrays (SAM) derived from 14 NPC and 6 normal samples discovered 1,089 differentially regulated genes. Pathway analyses revealed novel insights into the mechanisms leading to NPC, whereby upregulation of NFκB2 and survivin play central roles in increasing resistance to apoptosis, and changes in integrin and WNT/β‐catenin signaling leading to uncontrolled proliferation. The role of survivin in resisting apoptosis in NPC was confirmed by RNA interference. Our data provide novel insights into the development and progression of NPC, and suggest survivin as a novel therapeutic target for NPC.

Surgical salvage of persistent or recurrent nasopharyngeal carcinoma with maxillary swing approach — Critical appraisal after 2 decades

The purpose of this study was to report on our experience on salvage nasopharyngectomy using the maxillary swing approach for persistent or recurrent nasopharyngeal carcinoma after primary treatment.

Preoperative measurement of tumor thickness of oral tongue carcinoma with intraoral ultrasonography

Tumor thickness of oral tongue carcinoma is an important independent prognostic factor for local recurrence, subclinical nodal metastasis, and survival. An accurate preoperative assessment of tumor thickness is therefore essential in optimizing treatment algorithm. The present study aims at evaluating the accuracy of intraoral ultrasonography in preoperative measurement of tumor thickness.

Reconstruction of circumferential pharyngeal defects after tumour resection: reference or preference.

BACKGROUND Reconstruction of circumferential hypopharyngeal defects is often challenging. The aim of the study is to examine the result of our experience and to formulate improved management guidelines. METHOD Between 1980 and 2009, all patients who have circumferential pharyngectomy were recruited. Data were recorded prospectively for analysis. RESULTS A total of 202 patients were recruited. Majority had primary tumour in the hypopharynx (n=165), and the remaining patients had recurrent laryngeal carcinoma. Radiotherapy was given preoperatively in 72 patients and postoperatively in 108 patients. A pectoralis major (PM) flap was used in 92 (45.5%) patients, a free anterolateral thigh (ALT) flap in 24 (11.9%) patients and a free jejunal flap in 86 (42.6%) patients. Early fistula rate was 23.9% in the PM flap group, 12.5% in the ALT group and 4.6% in the jejunum group. Late anastomotic stricture rate was 27.2% in the PM flap group, 12.5% in the free ALT group and 2.3% in the jejunum group. Early fistula formation significantly increased the risk of subsequent anastomotic stricture (p=0.023). In patients with no stricture, 61.9% of them in the jejunal group were able to resume solid diet, compared with 35.8% and 38.1% in the PM and ALT groups. After PM flap harvesting, 34.8% of the chest wall defects could not be closed primarily, which were best repaired using the lateral thoracic flap. The donor-site morbidity of ALT and jejunal flap was low. CONCLUSION In suitable patients, free jejunal flap reconstruction of circumferential pharyngectomy defects achieves the best functional outcome with minimal donor-site morbidity.

Mature miR-184 and Squamous Cell Carcinoma of the Tongue

Human microRNA 184 (miR-184) is overexpressed in squamous cell carcinoma (SCC) of the tongue. In vitro inhibition of miR-184 levels could induce apoptosis and hinder proliferation of tongue SCC cells. Patients with tongue SCC have high plasma miR-184 levels. Plasma miR-184 is likely associated with the tumor load. Surgical removal of the primary tumor reduced plasma miR-184 levels significantly. The data suggested that miR-184 is linked to the pathogenesis of tongue SCC. Further studies are warranted to evaluate the use of microRNA-based serological markers in monitoring tongue SCC.

Elimination of palatal fistula after the maxillary swing procedure

The maxillary swing procedure has been used as an anterolateral approach to expose the nasopharynx, the central skull base, and its vicinity. The reported incidence of postoperative palatal fistula has ranged from 20% to 25%. The oronasal incompetence especially associated with a large fistula has adversely affected normal speech, eating, and swallowing functions. We describe a modified palatal incision to reduce the incidence of palatal fistula associated with the maxillary swing procedure.