Abstract: The present invention relates to an anoikis-inducing agent comprising a Tiarella polyphylla extract, a tiarellic acid compound isolated therefrom or a pharmaceutically acceptable salt thereof, which is specific to cancer cells expressing a tumor-associated antigen L6 or a homolog thereof. The Tiarella polyphylla extract, the tiarellic acid compound isolated therefrom or pharmaceutically acceptable salt thereof of the present invention leads to loss of cell adhesion to reduce cancer cell proliferation and exhibits the effect of inducing cell death in cancer cells expressing a tumor-associated antigen L6 or a homolog thereof, thereby being used for preventing and treating cancer diseases due to a tumor-associated antigen L6 or a homolog thereof.