To test the primary function of ECM1, we first silenced the expression of total ECM1 using short hairpin RNAs (shRNAs) specific for the transcripts encoding ECM1a, ECM1b, and ECM1c but not ECM1d (for rationale, see the “Materials and methods” section) (Fig. 1e) and analyzed the in vitro and in vivo tumor growth of the resulting cell lines. This evidence concerns the gene ECM1 and neoplasm.