Correlations between heparan sulfate metabolism and hepatoma growth

Abstract

A rat hepatoma cell line (Gershenson et al., Science, 170:859-861, 1970) contains a dynamic steady-state pool of free heparan sulfate (HS) chains in the nucleus that increases in amount when growing cells reach confluence (Fedarko and Conrad, J. Cell Biol., 102:587-599, 1986). In logarithmically growing cells labeled with 35SO4(2-) steady-state levels of [35SO4]HS in the nucleus are altered by a variety of culture conditions. Rapidly dividing cells (doubling time = 18-22 h) growing under optimized conditions had steady-state levels of nuclear HS within the range of 40-50 pmol 35SO4 in nuclear HS/10(6) cells. The steady-state levels of nuclear HS were lowered by several changes in culture conditions, including 1) additions of 1 mM p-nitrophenyl-beta-D-xyloside, 0.25-0.5 mM (+)-catechin, 0.5 ng/ml transforming growth factor beta, 20 ng/ml phorbol-12-myristate-13-acetate, 1 mM dibutyryl cAMP, or 1 mM inositol-2-PO4; 2) decreased levels of D-glucose; or 3) deletions of serum, insulin, or inositol. In all cases lowering of the nuclear HS level was accompanied by an increase in the cell doubling times, suggesting a correlation in which nuclear HS levels must be optimized for maximal growth rates. When cells cultured under optimal growth conditions reached confluence, the level of nuclear HS increased threefold and the cells stopped dividing. The same culture conditions that lowered the steady-state levels of HS in the logarithmically growing cells prevented this rise in the nuclear HS as the cells reached confluence and resulted in loss of contact inhibition and overgrowth of the confluent cultures. These observations suggest a second correlation in which elevated nuclear HS levels are found when cell growth is inhibited at confluence; prevention of this rise results in continued growth. Consistent with this correlation between elevated nuclear HS and reduced growth rates, it was observed that addition of either 0.5 microgram/ml hydrocortisone or 0.05 microgram/ml retinoic acid to the culture medium of logarithmically growing cultures resulted in increases in steady-state levels of nuclear HS that were accompanied by increased cell doubling times. The two agents that increased the levels of nuclear HS in logarithmically growing cultures had little effect on levels of nuclear HS in confluent cells or on contact inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Internalization and degradation of hepatocyte growth factor in hepatocytes with down‐regulation of the receptor/c‐Met

“…It is of note that cell-surface HSPG accumulates in the nucleus and regulates the growth of a hepatoma cell line [29]. Further study will elucidate the HGF-signal transduction mediated by each pathway.…”

Human heparanase nuclear localization and enzymatic activity

“…Several groups have reported the presence of HS chains in the nucleus of various cell types [5][6][7][39][40][41] and demonstrated that HSPGs may regulate the internalization and nuclear uptake of FGF-1 and FGF-2. [7][8][9] It was also suggested that a correlation exists between nuclear localization of HS and the growth rate of hepatoma cells, and that both glypican and biglycan participate in the regulation of C6 glioma cell proliferation and survival through a direct involvement of HSPGs in nuclear processes.…”

Organization of the Chick CDC37 Gene

“…Although these glycosaminoglycans are usually associated with extracellular matrices, they are also present at the cell surface (20) and within the cytoplasm and nucleus of several cell types (21)(22)(23). Although their intracellular functions are not yet established, it is noteworthy that a specific subpopulation of heparan sulfate is targeted to the nucleus of hepatoma cells (21,24) and that heparin inhibits Fos-and Jun-induced transcription events in vitro and in situ within the nucleus (25). The latter events may occur via competition with DNA binding (18,25).…”