Human breast-cancer metastasis formation in a nude-mouse model: Studies ofhyaluronidase, hyaluronan and hyaluronan-binding sites in metastatic cells

Few animal models are available to study metastasis formation. The purpose of the present study was to obtain a useful model of metastasis formation i n nude mice in an attempt to analyze the stroma reaction and in particular the production and the expression of hyaluronan (HA), hyaluronidase, and HA -binding sites by cultivated cells, and HA and hyaluronectin (HN) in the in vasive areas of tumors. Nude mice were subjected to i.p. injections of seve ral human cancer cell lines (PLC/PRF/5, HepG2, CB 191, CB 193, PC3, CAL 51, SA 87 and SA 98), and formation of metastases was analyzed in different or gans (lung, liver, kidney, spleen and axillary nodes) by immunohistochemica l techniques. CAL 51, a breast-cancer-metastasis-derived cell line with a n ormal karyotype, produced i.p. tumors in 75% animals and metastases in 90% animals (detected in the liver and axillary nodes). Two modes of invasion b y CAL 51 cells were observed in the liver: one, direct, from the surface of the liver and the other, indirect, via the bloodstream, HA and HN were str ongly expressed at the invasion areas. A cell line derived from hepatic met astasis of CAL 51 (HMD CAL 51)presented an abnormal karyotype, HMD CAL 51 p roduced more hyaluronidase(12-fold) and HA (IO-fold) and expressed more CD4 4 (1.6-fold) and other HA-binding sites (9.5-fold) than the established cel l line CAL 51. Our results show that i.p. injection of the CAL 51 cell line into nude mice provides a useful model of metastasis formation. The passag e of the CAL 51 cells from the primary state to the metastatic state was ch aracterized by a dramatic increase of HA and hyaluronidase production, and expression of HA, HN and HA-binding sites. (C) 1999 Wiley-Liss, Inc.