We investigated expression levels of Na + ,K + -ATPase K K-isoforms and their ATPase activities in human colorectal cancer tissue and the accompanying normal mucosa. A decrease in expression of the K K1-isoform protein was observed in all sampled cancer tissues compared with the normal mucosae. The level of ouabain (5 W WM)-sensitive Na + ,K + -ATPase activity in carcinomas was 81 þ 5% that of in the normal mucosae. The mRNA expression of K K2-and K K4-isoforms was decreased in almost all the carcinoma samples. Interestingly, the expression level of the K K3-isoform protein in the cancer tissue was higher than that of the normal mucosa. These results indicate that a decrease in the K K1-isoform expression and an increase in the K K3-isoform expression may be associated with colorectal cancer.

Tumor growth of colorectal cancers accompanies upregulation of cyclooxygenase-2, which catalyzes a conversion step from arachidonic acid to prostaglandin H 2 (PGH 2 ). Here, we compared the expression levels of thromboxane synthase (TXS), which catalyzes the conversion of PGH 2 to thromboxane A 2 (TXA 2 ), between human colorectal cancer tissue and its accompanying normal mucosa. It was found that TXS protein was consistently upregulated in the cancer tissues from different patients. TXS was also highly expressed in human colonic cancer cell lines. Depletion of TXS protein by the antisense oligonucleotide inhibited proliferation of the cancer cells. This inhibition was rescued by the direct addition of a stable analogue of TXA 2 . The present results suggest that overexpression of TXS and subsequent excess production of TXA 2 in the cancer cells may be involved in the tumor growth of human colorectum.

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The possibility of dextran magnetite complex (DM) as a new hyperthermic material was examined in this study. DM suspension of 56 mg ml(-1) iron concentration was locally injected into the normal tongue of golden hamster. DM injected tongues were heated by 500 kHz alternating current (AC) magnetic field and its serial changes in temperature were recorded at 30-s intervals. The temperature of DM injected tongue was maintained at about 43.0-45.0 degrees C for 30 min by changing the AC magnetic field intensity. While temperature elevations of the contralateral tongue and the rectum were only of minor degree. In experiment on the extent of heating area, there was correlation between volume of black stain area and amount of the injected DM suspension (Y = - 18.1 + 1.94X, r = 0.931, P < 0.0001, n = 9 ). Histological examination after heating revealed brown uniform DM accumulation in the connective tissue between fibers of the tongue muscle. Except for vascular dilatations, no tissue damage was seen in the heated tongue. Thus, DM which has the possibility of selective and uniform heating in local hyperthermia might be useful for oral cancer therapy.

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