Aspects of this invention relate to the fields of molecular biology and medicine. More specifically, disclosed herein are several approaches to provide subjects suffering from cancer with an inhibitor of S100A6 and/or S 100A4 alone or in combination with other cancer therapies so as to improve the cancer therapy and/or more efficiently treat cancer, in particular forms of cancer that are resistant to other therapies. Also disclosed herein are approaches for using S 100A6 and/or S 100A4 as a biomarker for metastases. Further, disclosed herein are approaches for using S 100A6 and/or S 100A4 as a biomarker for cancer therapies, in particular, as a biomarker to determine individual responses to cancer therapies. In addition, disclosed herein are approaches to identifying S 100A6 and/or S 100A4 inhibitors, for example, that act synergistically with a cancer therapy.