Resistance to chemotherapy is a major cause of therapeutic failure in cancer cure. Thus, development of novel compounds to be used either alone or as combined therapies constitutes an effective strategy to inhibit cancer cells and prevent the emergence of drug resistance. This invention consists of the use of the phenolic component Kaempferol alone or combined to chemotherapeutic drugs such as 5- Fluorouracil (5-FU) to treat cancers that are either resistant or not to chemotherapy.