Kenichi Sogawa

Histological study on pN upgrading of oral cancer

Abstract The International Union Against Cancer (UICC) does not define the number of sections required from each regional lymph node to record pTNM classification. This study was designed to clarify the incidence of occult metastasis and to assess the pN upgrading of patients with oral cancer. Ultimately, this study led to a proposal for appropriate semiserial sectioning guidelines. Five hundred fifty-four nonmetastatic cervical lymph nodes taken from 73 patients with oral cancer were subjected to hematoxylin-eosin (HE) staining and keratin immunohistochemistry. Micrometastases, defined as foci ≤3 mm, were detected in 29 sites of 23 lymph nodes (4.2%) of 16 patients (21.9%). In 9 patients (12.3%) pN upgrading was needed: in 6 from pN0 to pN1, in 1 from pN0 to pN2b, and in 2 from pN1 to pN2b. The remaining 13 lymph nodes with occult metastasis were found in 5 pN2b and 2 pN2c patients, resulting in no pN upgrading. Occult metastasis was also detected in 6 small lymph nodes ≤5 mm in diameter. The average minor axis of the micrometastasis was 1.36±0.85 mm. We propose that the lymph nodes should be cut and examined at 1-mm intervals to detect micrometastatic foci and to evaluate the pN classification accurately.

Telomerase components as a diagnostic tool in human oral lesions

Telomerase activity is considered to be a diagnostic marker of malignancy since most malignant cells express this activity and most somatic cells do not. However, the detection of telomerase activity is rather complicated and is affected by many factors. Recently, human telomerase components were cloned and found to consist of 3 subunits. We assessed which component of telomerase best correlates with malignancy in order to study the possibilities for developing a new diagnostic marker. Telomerase activity was measured by a telomeric repeat amplification protocol (TRAP) assay, and the telomerase components hTR, hTRT-mRNA and TP1-mRNA were detected by the reverse transcriptase-polymerase chain reaction (RT-PCR). Twenty-five of 26 oral malignant lesions, 9 of 22 benign lesions and none of 19 normal control tissues exhibited distinct telomerase activity. hTR and TP1-mRNA expression levels were detected in all malignant lesions and normal control tissues and had no significant correlation with the telomerase activity results. In contrast, hTRT-mRNA expression was closely associated with telomerase activity. All lesions expressing hTRT were telomerase positive. In addition, some samples of dysplastic lesions, benign tumors, lichen planus and normal mucosa exhibiting poor telomerase activity revealed weak expression of hTRT. Expression levels of hTRT-mRNA positively correlated with clinical and pathological findings. Detection of hTRT-mRNA by RT-PCR appeared to be more sensitive for telomerase than measurement of telomerase activity by the TRAP assay. Detection of hTRT-mRNA may provide information useful in the diagnosis of oral malignancies.

Keratin mRNA for detecting micrometastasis in cervical lymph nodes of oral cancer

We studied three keratin (K) gene candidates, K13, K19, and K20 mRNAs, for detecting micrometastases in cervical lymph nodes (LNs) by reverse transcriptase-polymerase chain reaction (RT-PCR). Of 166 histologically metastasis-negative nodes, 24 micrometastatic LNs (14. 4%) were detected based on K13 gene expression. Keratin 19 mRNA is an inadequate marker for the genetic diagnosis due to not only illegitimate gene expression from lymphatic tissue but also gene expression from the ectopic salivary gland. Keratin 20 mRNA showed low sensitivity. It is suggested that K13 mRNA may be a promising tumor marker among these keratin genes for detecting the micrometastases in cervical LNs of oral cancer.

Increased Expression of Matrix Metalloproteinase-2 and Tissue Inhibitor of Metalloproteinase-2 Is Correlated with Poor Prognostic Variables in Patients with Thymic Epithelial Tumors

A distinction between noninvasive, invasive, and metastatic thymoma on the basis of the cytologic features is difficult. The current study investigated whether the expression of MMP and TIMP was correlated with tumor invasiveness and prognosis in patients with thymoma.

Clinical usefulness of telomerase assay for the detection of lymph node metastasis in patients with oral malignancy

OBJECTIVE Telomerase is considered a diagnostic marker of malignancy. We investigated the usefulness of telomerase assay for the detection of lymph node micrometastasis. METHODS Sixteen cervical lymph nodes with metastasis of oral cancer and 20 benign lymph nodes were studied. The oral cancer cell line was used to estimate the sensitivity for telomerase assay. Telomerase activity was measured by semiquantitative telomeric repeat amplification protocol. RESULTS There was a significant difference between malignant and benign lymph nodes. The telomerase activity of 50 mg of lymph nodes with 103 or more cancer cells differed from that of control lymph nodes. Lymph nodes with 102 or fewer tumor cells expressed similar levels as benign lymph nodes. CONCLUSIONS In addition to routine histologic examination, telomerase assay is considered a useful tool for the detection of lymph node metastasis in patients with oral malignancy.

Telomerase activation and cell proliferation during 7,12-dimethylbenz[a]anthracene–induced hamster cheek pouch carcinogenesis

Telomerase is a ribonucleoprotein complex intimately involved in cell immortalization and carcinogenesis. This enzyme is activated and stabilizes telomere length in almost all types of cancer. Telomerase may be necessary for continuous cell proliferation. In this study, we analyzed telomerase activity in hamster experimental oral lesions (starting from epithelial hyperplasia through dysplasia, carcinoma in situ, and invasive carcinoma) evoked by 7,12‐dimethylbenz[a]anthracene, and in normal mucosa. We also analyzed proliferative activity in these lesions by using immunohistochemical analysis and flow cytometry. Histologically normal epithelium expressed weak telomerase activity. The telomerase activity count increased rapidly in the early stage of carcinogenesis and gradually in the late stage. Cell‐proliferative activity closely correlated with progression of disease. These findings indicate that telomerase activation is an early event and that increases in telomerase activity upregulate cell proliferation in chemically induced hamster oral carcinogenesis. Mol. Carcinog. 25:164–168, 1999.

Induction of apoptosis and inhibition of DNA topoisomerase-I in K-562 cells by a marine microalgal polysaccharide

We have previously purified an extracellular polysaccharide, D-galactan sulfate associated with L(+)-lactic acid, produced from a marine microalga Dinoflagellate Gymnodinium sp. A3 (GA3). The GA3 polysaccharide, irrespective of presence or absence of lactic acid, exhibited significant cytotoxicity, which is based on an induction of apoptotic cell death, toward human myeloid leukemia K562 cells. Furthermore, we found that the GA3 polysaccharide with or without lactic acid possesses an inhibitory effect on topoisomerase-I (topo-I). The potent cytotoxic effect of GA3 polysaccharide may result from its inhibitory effect on topo-I, because the topo-I inhibition is known to trigger apoptotic cell death.

Enhanced expression of catalytic subunit isoform PP1γ1 of protein phosphatase type 1 associated with malignancy of osteogenic tumor

The expressions of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, were examined in 14 cases of three types of osteogenic tumor using immunohistochemical analysis. The percentage of tumor cells stained positively with antiserum against PP1 catalytic subunit-isoform PP1 gamma 1 was significantly higher in malignant osteogenic tumors than in benign osteogenic tumors. Furthermore, malignant osteogenic tumor showed markedly high S-phase fraction in the cell cycle of tumor cells, as compared to benign osteogenic tumors. These results suggest that PP1 gamma 1 is involved in the accelerated growth of malignant cells in osteogenic tumors.

Enhanced expression of PP1γ1, a catalytic subunit isoform of protein phosphatase type 1, in invasive ductal carcinoma of the breast

Breast cancer is one of the most common malignancies of women. Assessing the biological parameters of malignant tumors may facilitate predictions of clinical outcome. The expression of the three catalytic subunits of protein phosphatase (PP) type 1, PP1 alpha, PP1 gamma 1 and PP1 delta, as well as the one catalytic subunit of PP type 2, PP2AC, were examined in ten cases of mammary dysplasia, ten cases of fibroadenoma and 12 cases of invasive ductal carcinoma, using immunohistochemical analysis. Moreover, we measured the S-phase fraction of the cell cycle for use as a marker value of cell growth, using flow cytometric analysis. The percentage of proliferating cells that stained positive with antisera against PP1 gamma 1 was significantly higher in invasive ductal carcinoma than in mammary dysplasia and fibroadenoma. Furthermore, invasive ductal carcinoma showed a markedly high number of tumor cells in the S-phase of the cell cycle, as compared to mammary dysplasia and fibroadenoma. Our results indicate that PP1 gamma 1 may be involved in the accelerated growth of malignant cells in breast tumors.