Functional role of glycosphingolipids in contact inhibition of growth in a human mammary epithelial cell line

We have demonstrated previously the involvement of certain glycosphingolipids ( GSL s) in ‘contact inhibition’ (dependent on cell‐to‐cell contact) of cell growth. Here, we examined the roles of specific GSL s in contact inhibition of the human epithelial cell line MCF 10A. Contact‐inhibited cells show increased expression of the ganglioside GD 3 and the globo‐series GSL Gb3, and of the mRNA s for the corresponding sialyltransferases ST 8 SIA 1 ( GD 3 synthase) and galactosyltransferase A4 GALT (Gb3 synthase). si RNA knockdown (KD) of ST 8 SIA 1 and/or A4 GALT significantly suppresses contact inhibition. Exogenous addition of GD 3 or Gb3 inhibits proliferation of low‐density cells. Our findings suggest that GSL s play functional roles in contact inhibition of these cells and that Merlin/ NF 2, a tumor suppressor protein, is involved in the GSL function.