TEAD4-YAP interaction regulates tumoral growth by controlling cell-cycle arrest at the G1 phase.

TEA domain transcription factor 4 (TEAD4), which has critical functions in the process of embryonic development, is expressed in various cancers. However, the important role of TEAD4 in human oral squamous cell carcinomas (OSCCs) remain unclear. Here we investigated the TEAD4 expression level and the functional mechanism in OSCC using quantitative reverse transcriptase-polymerase chain reaction, Western blot analysis, and immunohistochemistry. Furthermore, TEAD4 knockdown model was used to evaluate cellular proliferation, cell-cycle analysis, and the interaction between TEAD4 and Yes-associated protein (YAP) which was reported to be a transcription coactivator of cellular proliferation. In the current study, we found that TEAD4 expression increased significantly in vitro and in vivo and correlated with tumoral size in OSCC patients. TEAD4 knockdown OSCC cells showed decreased cellular proliferation resulting from cell-cycle arrest in the G1 phase by down-regulation of cyclins, cyclin-dependent kinases (CDKs), and up-regulation of CDK inhibitors. We also found that the TEAD4-YAP complex in the nuclei may be related closely to transcriptions of G1 arrest-related genes. Taken together, we concluded that TEAD4 might play an important role in tumoral growth and have potential to be a therapeutic target in OSCCs.

Evidence for Critical Role of Lymphocyte Cytosolic Protein 1 in Oral Cancer.

Lymphocyte cytosolic protein 1 (LCP1), a member of actin-binding protein of the plastin family, has been identified in several malignant tumors of non-hematopoietic sites, such as the colon, prostate, and breast. However, little is known about the roles of LCP1 in oral squamous cell carcinomas (OSCCs). This present study sought to clarify the clinical relevance of LCP1 in OSCCs and investigate possible clinical applications for treating OSCCs by regulating LCP1 expression. We found up-regulation of LCP1in OSCCs compared with normal counterparts using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunoblotting, and immunohistochemistry (P < 0.05). We used shRNA models for LCP1 (shLCP1) and enoxacin (ENX), a fluoroquinolone antibiotic drug, as a regulator of LCP1 expression. In addition to the LCP1 knockdown experiments in which shLCP1 cells showed several depressed functions, including cellular proliferation, invasiveness, and migratory activities, ENX-treated cells also had attenuated functions. Consistent with our hypothesis from our in vitro data, LCP1-positive OSCC samples were correlated closely with the primary tumoral size and regional lymph node metastasis. These results suggested that LCP1 is a useful biomarker for determining progression of OSCCs and that ENX might be a new therapeutic agent for treating OSCCs by controlling LCP1 expression.

Novel mechanism of aberrant ZIP4 expression with zinc supplementation in oral tumorigenesis.

Zrt-Irt-like protein 4 (ZIP4) is critical molecule for proper mammalian development and releasing zinc from vesicular compartments. Recent studies suggested that ZIP4 plays an important role of tumor progression in pancreatic, prostate, and hepatocellular cancers, however, little is known about the detail mechanism of ZIP4 in their cancers. In the present study, we examined the possibility of ZIP4 as a new molecular target for oral squamous cell carcinoma (OSCC). We evaluated ZIP4 expression in OSCC-derived cell lines and primary OSCC samples by quantitative RT-PCR, immunoblotting, and immunohistochemistry (IHC). We also analyzed the clinical correlation between ZIP4 status and clinical behaviors in patients with OSCC. In addition, ZIP4 knockdown cells (shZIP4 cells) and ZnCl2 treatment were used for functional experiments, including cellular proliferation assay, zinc uptake assay, and cell-cycle analysis. ZIP4 mRNA and protein were up-regulated significantly in OSCCs compared with normal counterparts in vitro and in vivo. IHC showed that ZIP4 expression in the primary OSCC was positively correlated with primary tumoral size. The shZIP4 cells showed decrease accumulation of intercellular zinc and decreased cellular growth by cell-cycle arrest at the G1 phase, resulting from up-regulation of cyclin-dependent kinase inhibitors and down-regulation of cyclins and cyclin-dependent kinases. Since cellular growth of OSCC cells after treatment with zinc was significantly greater than control cells, we speculated that intercellular ZnCl2 accumulation is an important factor for cellular growth. Consistent with our hypothesis, not only decreased zinc uptake by ZIP4 knockdown but also chelating agent, N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), showed inhibitory effects of cellular proliferation. Therefore, our data provide evidence for an essential role of ZIP4 and intracellular zinc for tumoral growth in OSCC, suggesting that zinc uptake might be a potential therapeutic targeting event for OSCCs.

Maxillary Swelling as the First Evidence of Multiple Myeloma.

Multiple myeloma is a malignant neoplasm of plasma cells characterized by proliferation of a single clone of abnormal immunoglobulin-secreting plasma cells. Since the amount of hemopoietic bone marrow is decreased in the maxilla, oral manifestations of multiple myeloma are less common in the maxilla than in the mandible. We report the case of 33-year-old Japanese man who presented with a mass in the right maxillary alveolar region. Computed tomography and magnetic resonance images showed a soft tissue mass in the right maxilla eroding the anterior and lateral walls of the maxillary sinus and extending into the buccal space. The biopsy results, imaging, and laboratory investigations led to the diagnosis of multiple myeloma. This case report suggests that oral surgeons and dentists should properly address oral manifestations as first indications of multiple myeloma.