Invasion of Melanoma in Double Knockout Mice Lacking Tenascin-X and Tenascin-C

The roles of extracellular matrix glycoproteins belonging to the tenascin family in the regulation of tumor cell proliferation, invasion, and metastasis are not known. To address this issue, we generated tenascin-X (TNX) and tenascin-C (TNC) double knockout mice and compared findings in these mice with those in single knockout (TNX+/+TNC-/- and TNX-/-TNC+/+) mice. We investigated the proliferation and invasion of B16-BL6 melanoma cells after these cells had been injected into the footpads of mice in each group. The primary tumor size and invasion to the ankle adjacent to the primary tumor site were examined at 35 days after injection of the melanoma cells. The primary tumor size in TNX-/-TNC+/+ mice was significantly larger than that in wild-type mice, but those of TNX+/+TNC-/- and double knockout mice were comparable to that in the wild-type mice. On the other hand, invasion to the ankle was obviously promoted in TNX- I - TNC+/+ and double knockout mice compared with that in the wild-type mice, but invasion to the ankle in TNX+/+TNC-/- mice was only slightly promoted. Gelatin zymography confirmed increased matrix metalloproteinase (MMP)-9 activity in the dorsal skin of TNX-/-TNC+/+, TNX+/+TNC-/- and double knockout mice. However, the amounts of MMP-9 mRNA in the dorsal skins of all mice were almost the same, indicating that the increased activity of MMP-9 in the single and double knockout mice is regulated at the MMP-9 processing level. These results indicate that MMP-9 is activated in all TN-deficient mice, but that TNX exerts a greater effect on tumor invasion than does TNC.     

APC10.1 cells as a model for assessing the efficacy of potential chemopreventive agents in the Apc mouse model in vivo

Apc^Min mice are widely used for mechanism and efficacy studies associated with the development of chemopreventive agents. APC10.1 cells have been derived from Apc^Min mouse adenomas and retain the heterozygous Apc genotype. We tested the hypothesis that this cell type may provide an in vitro model to predict chemopreventive activity of agents in the Apc^Min mouse in vivo.The growth inhibitory properties of 14 putative colorectal cancer chemopreventive agents, tricin, apigenin, 3′,4′,5′,5,7-pentamethoxyflavone, resveratrol, curcumin, 3,4-methylenedioxy-3′,4′,5′-trimethoxychalcone (DMU135), 3,4,5,4′-tetramethoxystilbene (DMU212), celecoxib, aspirin, piroxicam, all-trans-retinoic acid, difluoromethylornithine (DFMO), quercetin and cyanidin-3-glucoside, were studied in this cell line, and the IC₅₀ values were calculated. The IC₅₀ values were plotted against previously published data of reduction of adenoma numbers caused by these agents in Apc^Min mice. The correlation co-efficient was 0.678 (p < 0.01), suggesting that there was a tentative correlation between the ability to inhibit the growth of APC10.1 cells and the ability to delay adenoma development in vivo. If this relationship is supported by using further agents, APC10.1 cells may serve in the future as an initial screen to prioritise compounds for assessing chemopreventive efficacy in Apc^Min mice in vivo. Such a screen could reduce the number of animals required to find active agents, help reduce costs and increase throughput.     

Allelic Loss at the Tuberous Sclerosis (Tsc2) Gene Locus in Spontaneous Uterine Leiomyosarcomas and Pituitary Adenomas in the Eker Rat Model

Hereditary renal carcinomas (RCs) develop in virtually all Eker rats by the age of one year. Investigation of extra-renal primary tumors co-occurring in Eker rats late in life (at 2 years) additionally revealed enhanced development of hemangiosarcomas of the spleen, uterine leiomyosarcomas and pituitary adenomas, although the demonstrated predilection for these extra-renal tumors was not as complete as with RCs. We identified the germline mutated tuberous sclerosis ( Tsc2 ) gene as the predisposing Eker gene and revealed the tumor suppressor nature of Tsc2 gene function in renal carcinogenesis. In the present study, we examined allelic loss at the Tsc2 gene locus in uterine leiomyosarcomas and pituitary adenomas developing in hybrid F1 rats carrying the Eker mutation as well as in pituitary adenomas from non-carrier rats. We detected loss of heterozygosity in 4 of 11 uterine leiomyosarcomas (36%) and 11 of 31 pituitary adenomas (35%) from Eker rats but in none of 9 pituitary adenomas from non-carrier rats ( P <0.05), suggesting that inactivation of the Tsc2 gene is also a critical event in the pathogenesis of these extra-renal tumors. Our present data indicate that there might be different pathways for tumorigenesis of pituitary adenomas between Eker and non-carrier rats.