LAUSR

We have demonstrated previously the involvement of certain glycosphingolipids (GSLs) in ‘contact inhibition’ (dependent on cell‐to‐cell contact) of cell growth. Here, we examined the roles of specific GSLs in contact inhibition of the human epithelial cell line MCF10A. Contact‐inhibited cells show increased expression of the ganglioside GD3 and the globo‐series GSL Gb3, and of the mRNAs for the corresponding sialyltransferases ST8SIA1 (GD3 synthase) and galactosyltransferase A4GALT (Gb3 synthase). siRNA knockdown (KD) of ST8SIA1 and/or A4GALT significantly suppresses contact inhibition. Exogenous addition of GD3 or Gb3 inhibits proliferation of low‐density cells. Our findings suggest that GSLs play functional roles in contact inhibition of these cells and that Merlin/NF2, a tumor suppressor protein, is involved in the GSL function.