Shinichi Nozaki

Immunohistochemical localization of a urokinase-type plasminogen activator system in squamous cell carcinoma of the oral cavity: association with mode of invasion and lymph node metastasis.

The binding of urokinase-type plasminogen activator (uPA) to its receptor (uPAR) has been implicated in cancer invasion and metastasis. This activity is known to be regulated by several inhibitors such as plasminogen activator inhibitors (PAIs). To elucidate the participation of the uPA system in the malignant behaviour of squamous cell carcinoma (SCC) in the oral cavity, uPA, uPAR, PAI-1 and -2 expression and localisation in 34 primary oral cancers were examined immunohistochemically. The results were then compared with clinicopathological findings. The positive rates of uPA, uPAR, PAI-1 and -2 expression were 23.5, 29.4, 29.4 and 11.8%, respectively. uPA expression correlated with mode of cancer invasion according to Yamamoto-Kohamas criteria (p < 0.01) and with secondary regional lymph node metastasis. uPAR expression also correlated with mode of invasion. In particular, the tumours of both uPA- and uPAR-positive [uPA(+)/uPAR(+)] cases were highly invasive. In the present study, neither PAI-1 nor PAI-2 expression correlated with clinicopathological parameters. However, PAI-2 negative cases of uPA(+)/uPAR(+) were significantly more invasive (p < 0.0001). Such uPA(+)/uPAR(+)/PAI-2(-) cases almost always showed secondary lymph node metastasis (p < 0.01). These results indicate that the uPA system plays a significant role in the invasive and metastatic processes of oral SCC, and that this system may be a powerful aid in evaluating the clinical course or prognosis of patients with oral cancer.

Loss of maspin is a negative prognostic factor for invasion and metastasis in oral squamous cell carcinoma

OBJECTIVE Maspin, a 42-kDa protein, belongs to the serpin family of protease inhibitors and is known to have tumor-suppressor function. In this study, we investigated the interrelationship between clinicopathologic findings and maspin expression in oral squamous cell carcinoma (OSCC). METHODS Using immunohistochemical techniques to examine the expression levels of maspin in OSCC, maspin expression in OSCC was detected in 46 (64.8%) of 71 cases. We also compared the clonicopathologic features of OSCC cases with maspin expression levels. Moreover, we examined expression of maspin in eight cell lines derived from OSCC using reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. RESULTS There was a significant correlation between decreased maspin expression and T-category (P < 0.01), lymph metastasis (P < 0.0001), and mode of invasion (P < 0.0001). Patients with positive maspin expression had a significantly better prognosis (P < 0.001). Lower expression of maspin was also seen in cell lines derived from grade 4D, which shows stronger invasive potential than other grades of OSCC. CONCLUSION Maspin may be a useful marker to identify the potential for progression in OSCC.

Fibroblast Growth Factor-2 Accelerates Invasion of Oral Squamous Cell Carcinoma

Abstract The aim of this study was to examine the effects of fibroblast growth factor-2 (FGF-2) on cancer cell invasion on fibroblast proliferation in an in vitro model of invasion. Three kinds of human oral squamous cell carcinoma cell lines with different invasive activity were used: OSC-20, OSC-19 (lower invasive type), HOC313 (higher invasive type). FGF-2 its high-affinity receptors FGFR-1 FGFR-2 were detected by western blotting. The expression of FGF-2 FGFRs mRNA was examined in cultured human oral squamous cell carcinoma cells by reverse transcriptase polymerase chain reaction (RT-PCR). Furthermore, recombinant human FGF-2 (rhFGF-2) was reacted with each cell line, the invasion rate was determined by invasion assay. We also observed the behavior of cancer cell invasion in the collagen gel invasion model in the presence or absence of FGF-2-neutralizing antibody (anti-FGF-2). HOC313 cells showed higher expression of FGF-2 than OSC-20 OSC-19 cells. The addition of rhFGF-2 promoted not only the proliferation of fibroblasts, but also the invasion of all cancer cell lines. In contrast, the addition of anti-FGF-2 completely inhibited the invasion of OSC-20 OSC-19 cells. These results suggest that a higher invasiveness of squamous carcinoma cells is associated with higher production of FGF-2, which acts in an autocrine fashion to promote cancer cell invasion, in a paracrine fashion to promote fibroblast proliferation.

Inhibition of Rac Induces Hyper-Activation of c-Jun N-Terminal Kinase and Caspase-Dependent Apoptosis

Abstract Apoptosis is one mechanism by which cancer cells can be eliminated. Therefore, understanding the signaling pathways that transduce apoptotic signals in cancer cells is an indispensable component of cancer research. Rac, a member of the Rho family of proteins, has been implicated in the regulation of cell survival and apoptosis. However, the mechanisms underlying this process remain to be elucidated. To understand the role of Rac in oral squamous cancer, we inhibited its activity by a Rac-specific small molecule inhibitor, NSC23766, or transfection of dominant negative Rac (Rac-DN), and discovered that inhibition of Rac activity elicits apoptosis in highly malignant oral squamous carcinoma (OSC-19) cells. Upon suppression of Rac, we observed up-regulation of c-Jun N-terminal kinase (JNK), leading to caspase-dependent apoptosis. Furthermore, stimulation of protein phosphatase (PP5) rescued apoptosis caused by Rac inhibition by dephosphorylating JNK. Taken together, inhibition of Rac activity leads to the suppression of PP5 activity, which results in extensive activation of JNK and caspase-dependent apoptosis. In conclusion, Rac inhibition may represent a novel therapeutic approach for oral squamous carcinoma.

Expression of Copper Efflux Transporter (ATP7B) in the Transport of Cisplatin in Cell Lines Derived From Invasive Oral Squamous Cell Carcinoma

Abstract Intrinsic or acquired resistance to cisplatin (CDDP) is a problem for its use in cancer chemotherapy. This resistance has been reported to correlate with expression of the human copper transporter 1 and two copper export pumps, ATP7A and ATP7B. In the current study, we investigated the correlation between the expression of these transporters and sensitivity to CDDP using four cell lines derived from each of high invasive oral squamous cell carcinoma (OSCC) and low invasive OSCC. We found that the amount of CDDP accumulated in high invasive OSCC cell lines (Yamamoto-Kohama criteria : grade 4C and 4D) with strong intrinsic tolerance was lower than in low invasive OSCC cell lines (grade 3) with weak intrinsic tolerance. Additionally, overexpression of ATP7B mRNA in cell lines derived from high invasive OSCC conferred low sensitivity to CDDP. Furthermore, the accumulation and sensitivity of CDDP was higher in HOC313 cells transfected with the ATP7B siRNA than in cells transfected with the nonsense siRNA. These results suggest that the overexpression of ATP7B results in the export of and, therefore, resistance to CDDP. Furthermore, ATP7B may be a key determinant of the intrinsic resistance to CDDP.