Cancer treatment remains a serious problem worldwide. Analysis of the relationship between cancer cellsand normal cells reveals that these two share characteristics in contradiction, thus could be analyzed by usingcontradictory principles. Under the theory of contradictory principles, induction of a dormant state or reversalof cancer cells is an important treatment strategy beyond traditional cytotoxic therapy. Normal cells are also thetargets and under the influence of anti-cancer treatments and should be considered during therapy. Findingsbased on crosstalk between these two cell types may offer opportunities for the development of new biomarkersand therapies.