Disclosed is a medium for cultivating tumor cells, comprising the
following constituents, as comprised for example in the medium RPMI 1640:
(a) fetal calf serum (FCS), (b) penicillin-streptomycin, (c) L-glutamine,
(d) transferrin, (e) insulin, (f) human epidermal growth factor (EGF) and
(g) .alpha.-TGF. A method for characterizing tumor cells or potential
tumor cells, respectively, is also described. Said method includes the
culturing of cells in the inventive medium and the two tumor cell lines
LNHOS1 and PTHOS1 established by means of the inventive culturing method.