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 even 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.