The present invention relates to a composition useful for the diagnosis of diseases associated with aberrant expression of the gene encoding the receptor Kremen 1 and/or Kremen 2 e.g. tumors or diseases of the kidneys, bones and eyes. The present invention also relates to a pharmaceutical composition containing a compound which is capable of modifying (a) the expression of the gene encoding Kremen 1 and/or Kremen 2 or (b) the activity of the Kremen 1 and/or Kremen 2 receptor.