Activation of the leukocyte plastin gene occurs in most human cancer cells.

Examination of human neoplastic cell lines using reverse transcription-polymerase chain reaction (RT-PCR), Northern blotting, and protein profiling revealed that > 90% of transformed human cell lines surveyed exhibited widely varying degrees of activation of the leukocyte (L)-plastin gene. By contrast, diploid cell types exhibited no evidence of event transient activation of this gene. The low level activation of the L-plastin gene, detectable only by RT-PCR, was confirmed by using the recombinant human L-plastin promoter to select "L-plastin positive" clonal subpopulations from these RT-PCR-positive cell lines. A stable cell line selected by this method exhibited low level constitutive synthesis of L-plastin mRNA and polypeptide. This cell line also exhibited the coinduction of at least three highly abundant new cytoplasmic proteins (M(r) 42,000, 37,000, and 34,000) and reduction in growth rate and saturation density. Most clonal cell lines derived by this selection procedure that activated the L-plastin gene exhibited a crisis stage that led to death of the clonal strain, a phenomenon that could be reproduced by induction of synthesis of recombinant L-plastin from its complementary DNA.