HETEROGENEITY OF RENAL CELL CARCINOMA II
STUDIES ON TUMORIGENICITY OF CULTURED CELL LINE KU-2
1985 Volume 76 Issue 4 Pages 521-527
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1985 Volume 76 Issue 4 Pages 521-527
The heterogeneity in tumorigenicity of cell line KU-2 derived from human renal cell carcinoma was studied utilizing ten clone cell lines (N-2, 3, 5-11 and 13) of KU-2.
As an in vitro study on tumorigenicity, clonogenicity of the clones was determined in a soft agar culture. Single separated cells were inoculated 104 per ml in concentration. The plating efficiency (PE) of KU-2 was 45.7%, while the clones showed variety of PE, ranging from 6.8% to 54.9%. Of these clones, 4 clones, N-7 (PE=21.7%), N-8 (40.0%), N-10 (22.1%), N-13 (6.8%), and KU-2 were studied on their tumorigenicity in vivo. Twenty to fifty million cells of each clone were subcutaneously inoculated in 5-6 nude mice. KU-2, N-8 and N-10 formed visible tumors in 3/5, 2/6 and 3/6 of nude mice within 1-4 months after cell inoculation. However, no tumors grew in the nude mice in which N-7 or N-13 was inoculated. Histological examination of the tumors in nude mice showed some difference in differentiation of adenocarcinoma among 2 clones and KU-2. N-10 was less differentiated in glandular formation than N-8 and KU-2. Finally, to analyze the interaction between tumorigenicity and susceptibility to natural killer (NK) activity, lysis of the clones and KU-2 mediated by NK cells in human peripheral blood lymphocytes (PBL) were determined by 51Cr-releasing assay. In experiments using PBL of 3 young men activated by 1000IU/ml Interferon-α, N-8 was always most resistant to NK activity, followed by N-10, KU-2, N-7 and N-13. The average total lytic units of PBL against N-8 was about 1/3 of that against N-7.
The results of this study indicate that KU-2 cell line consists of heterogeneous cell populations with different degrees of tumorigenicity and of susceptibility to NK cell mediated cytotoxycity. The clones tumorigenic in nude mice were resistant to NK activity, which suggests acquisition of resistibility to NK activity is required of the cells to be tumorigenic in vivo. In addition, the presence of less tumorigenic and highly NK-sensitive clones in highly tumorigenic and less NK-sensitive cell line indicates that cell differentiation always occurs in a part of the tumor cells.
