Differences in the Uptake and Nuclear Localization of Anti-proliferative Heparan Sulfate Between Human Lung Fibroblasts and Human Lung Carcinoma Cells

Heparan sulfate inhibits the proliferation of normal human lung fibroblasts (HFL-1) but not of a human lung carcinoma cell-line (A549). In this study we investigated possible mechanisms and structural requirements by which antiproliferative heparan sulfates exerts its effects on binding, uptake and subcellular localisation. Both HFL-1 and A549 cells were incubated with 125I- or rhodamine-labeled L-iduronate-rich antiproliferative heparan sulfate species as well as L-iduronate-poor inactive ones. The antiproliferative heparan sulfate was bound to the cell surface on both HFL-1 and A549 cells, but to a lesser extent and with less affinity to A549 cells. Both cell types bound the antiproliferative heparan sulfate with one high- and with one low affinity site. The L-iduronate-poor heparan sulfate bound to a lesser extent and with less affinity to both cell types compared to the antiproliferative heparan sulfate. The antiproliferative heparan sulfate accumulated in the cytoplasm of HFL-1 cells after 24 h incubation, but after 72 h it was found evenly distributed in the nucleus. The time-scale for antiproliferative activity correlated with nuclear localization. In contrast, in A549 cells it was only found near the nuclear membrane. The inactive heparan sulfate was taken up in considerably smaller amounts compared to the antiproliferative heparan sulfate and could not be detected in the nucleus of either HFL-1 or A549 cells. Our data suggest that the antiproliferative activity of L-iduronate-rich heparan sulfate on normal fibroblasts may be due to direct effects on nuclear processes, such as gene transcription.