Enhanced nucleocytoplasmic RNA transport has been demonstrated by incubating normal rat liver nuclei in presence of cytosols originating from the poorly differentiated, fast-growing
hepatoma HW-165, in the linear phase of
tumor growth. The effect of
hepatoma HW-165 cytosol was reduced or suppressed in presence of small amounts of normal liver cytosol: on the other hand, several
polypeptides of molecular weight 20,000 to 40,000 daltons were hardly detectable in
hepatoma HW-165 cytosol, both arguments indicating that potentially regulatory
proteins should be absent or present in reduced concentration in
hepatoma HW-165 cytosol. No modification of
RNA release was observed in presence of cytosols originating from the thymus of RNA virus (BL/F)-infected rats, whatever be the time after inoculation. Attempts were made to use the nuclear restriction assay, supplemented with plasma or serum of various origins, as a
biochemical marker of
neoplasia. In a first series of assays, including 80
cancer patients and 12 healthy controls, the RNA transport activity was stimulated by the serum of patients bearing various
tumors (
lung cancer,
cancer of the respiratory tract, uterine cervix...), except in a few cases of mammary
carcinoma, where values equivalent to or lower than the controls were obtained.