The present invention relates to novel isolated antibodies, or the derived compounds or functional fragments of same, capable of inhibiting the proliferation of tumor cells in vitro and/or in vivo, said antibodies having been obtained by functional screening. More particularly, the present invention relates to the 6F4 antibody, specific to the JAM-A protein, as well as its use for the treatment of cancer. Pharmaceutical compositions composed of such antibodies are also covered.