Clonal analysis of mouse plasmacytomas showing decreased oncogenicities after long-term culture.

C ell lines and derived clones o f the m ouse plasm acytom a M OPC-315 w ere analyzed for: (1) oncogenicity in vivo , (2) doubling tim es in vitro , (3) differences in im m unoglobulin structure and secretion and (4) viral enzym e activity. Seven clones derived from the J27-3a line of M OPC-315 w ere less on­ cogenic than the original tum or and th e p aren t cell line. F our caused 80 to 90 p ercen t le thal tumors, b u t only at a dose of 1 x 107 cells. N one o f th e clones p roduced m ore than 40 p ercen t le thal tum ors w hen 1 x 106 cells w ere injected. Spontaneously regressing tum ors developed from all clones b u t not from the p aren t tum or or cell line. R egression of estab lished tum ors occurred m ore often in the th ree oncogenic clones (58 percent) than in the four m ore oncogenic clones (16 percent). C ell doubling tim es in vitro varied from 17 hours to 87 hours b u t w ere not p red ic tive of oncogenicity in v ivo . C lones varied over a 40-fold range w ith resp ec t to im m unoglobulin secretion, b u t no correlation w ith oncogenicity could be found. C rossed disc gel-rocket electrophoresis and O uchterlony a n a ly s is o f c u ltu re m e d ia d e m o n s tra te d no c h a n g e s in s e c re te d im m unoglobulins. An inverse relation b e tw een oncogenicity and viral enzym e activity was found w hen J27-3a was com pared to clones derived from it. H ow ever, relative oncogenicity and viral enzym e activity d id no t correlate com pletely am ong the clones them selves. * Supported in part by grants CA 17487 and CA 13625 from the National Institutes of Health. t Present address: Laboratory of Toxicology, Na­ tional Cancer Institute, NIH, Building 37, Room 5B22, Bethesda, MD 20205. | To whom requests for reprints should be addressed.