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Abstract. Five out of six human melanoma cell lines tested were able to degrade in vitro a smooth muscle cell extracellular matrix in a plasmin-dependent way. In three of these five cell lines, this process was mediated by tissue-type plasminogen activator (t-PA) and in the other two cell lines by urokinase-type plasminogen activator (u-PA).All melanoma cell lines produced t-PA mRNA and protein, whereas only the two cell lines showing u-PAmediated matrix degradation produced u-PA mRNA and protein . These latter cell lines also produced plasminogen activator inhibitor type-1 (PAI-1) and type-2 (PAI-2) mRNA and protein . u-PA receptor (u-PA-R) mRNA and binding of radiolabeled u-PA was found in all melanoma cell lines. The metastatic capacity of these cell lines was studied in nude mice. All cell lines were able to develop primary tumors at the sub-RING metastasis, tumor cells must penetrate basement membranes and interstitial tissues, when they detach from the primary tumor and intravasate into the circulation, and later when they extravasate at the site formation of the secondary tumor. This means that these tumor cells should express the right panel and adequate levels of proteolytic enzymes to degrade the extracellular matrix (15,16,24,34,49,57) . In addition, these enzymes may have a function in the process of angiogenesis when endothelial cells grow invasively into the newly formed tumor and form new blood vessels (25,38) . The serine protease plasmin is one ofthe major enzymes believed to be involved in such proteolytic processes (15,16,24,42,43) . Plasmin has a broad substrate specificity and can digest most of the components of the extracellular matrix including the basement membrane, either directly or by activation of proenzymes of metalloproteinases, like type IV collagenase or interstitial collagenase (23,39,57) . Plasmin is formed by a conversion of the zymogen plasminogen, which is regulated by plasminogen activators. Two distinct plasminogen activators The two u-PA and PAM producing cell lines showed the highest frequency to form spontaneous lung metastases after subcutaneous inoculation, whereas five of the six cell lines formed lung colonies after intravenous inoculation .In conclusion, u-PA mediated matrix degradation in vitro and production of u-PA and PAI-1 by human melanoma cell lines correlated with their ability to form spontaneous lung metastasis in nude mice. No correlation was found with the ability to form lung colonies after intravenous injection. These findings suggest a role for u-PA and PAI-1 in a relatively early stage of melanoma metastasis.are known, the tissue-type (t-PA),' and the urokinase-type (u-PA) . The activity ofthe activators can be regulated by interactions with specific inhibitors, of which two have been described, type 1(PAI-1) and type 2 (PAI-2) (33, 53) . In addition, u-PA and its proenzyme, pro-u-PA, can be localized at cell surfaces by binding through their growth factor domain to a specific receptor (u-PAR) (2,8,12,41,51,55,56,62) .To study the role of plasminoge...

Summary We studied the relation between tumour vascular density and tumour growth rate, metastatic incidence and vascular permeability factor (VPF) mRNA levels in a human xenograft model described previously. Vascular density was determined by automated image analysis.Xenografts derived from cell lines BLM and MV3 showed the highest mean vascular density (MVD), the highest in vivo growth rate, high VPF mRNA levels and rapid development of lung metastases. Xenografts of cell lines M14, Mel57 and MV1 showed a significantly lower degree of vascularization, lower in vivo growth rates and lower levels of VPF mRNA, but formed lung metastases with a similar incidence as those of BLM and MV3. Xenografts from cell line 1 F6 did not form lung metastases, whereas tumours derived from a spontaneous mutant of 1 F6, designated 1 F6m, gave rise to lung metastases to the same extent as Mel57, M14 and MV1 tumours. MVD values in 1 F6 and 1 F6m xenografts, VPF mRNA levels and in vivo growth rates of 1 F6 and 1 F6m xenografts, however, were similar. In conclusion, in the melanoma xenograft model vascular density is correlated with in vivo growth rate and with in vitro VPF mRNA levels, but not with the ability to metastasize.

The contribution of cigarette smoking to sporadic colorectal cancer may differ according to molecular aspects of the tumor or according to glutathione S-transferase M1 (GSTM1) or glutathione S-transferase T1 (GSTT1) genotype. In the prospective Netherlands Cohort Study on Diet and Cancer, adjusted incidence rate ratios for 1986-1993 were computed for overall colorectal cancer, tumors with and without adenomatous polyposis coli (APC) mutations, and tumors with and without human mut-L homologue 1 (hMLH1) expression, according to cigarette smoking characteristics (661 cases, 2,948 subcohort members). Case-only analyses were performed to estimate odds ratios for interaction between cigarette smoking and GSTM1 and GSTT1 genotypes. In comparison with never smokers, a high smoking frequency increased the risk of colorectal cancer (for a five-cigarette/day increment, incidence rate ratio (IRR) = 1.07, 95% confidence interval (CI): 1.03, 1.12), and this association was stronger in 371 tumors without a truncating APC mutation (IRR = 1.11, 95% CI: 1.05, 1.17). Long-term smoking was associated with lack of hMLH1 expression in 56 tumors (for a 10-year increment, IRR = 1.17, 95% CI: 1.00, 1.37). No statistically significant interactions between smoking and GSTM1 or GSTT1 genotype were observed. These results indicate that cigarette smoking is associated with risk of colorectal cancer, and this association may depend on molecular characteristics of the tumor as defined by APC mutation and hMLH1 expression status.

SUMMARY Ninety four pulmonary neoplasms were examined immunocytochemically with two or three different monoclonal antibodies against the intermediate filament proteins cytokeratin, neurofilament, vimentin, and desmin. In normal tissues these have a different and non-overlapping distribution, and it is generally believed that tumours maintain the same pattern of expression as the tissues from which they arise. In this report, however, the coexpression of at least two (