Abstract: The present invention provides a method to treat susceptible cancers in humans comprising administering a cancer-treating amount of a member of the tetracycline family or a pharmaceutically acceptable salt thereof. Doxycycline, minocycline and tetracycline are utilized in the preferred method. Preferred methods of the present invention treat osteo-, breast, lung, prostate or Kaposi's cancers. Other aspects of the invention are described in the full application.