The present invention is directed to the identification of markers that can be used to determine whether tumors are sensitive or resistant to a therapeutic agent. The present invention is also directed to the identification of therapeutic targets. The invention features a number of "sensitivity markers." These are markers that are expressed in most or all cell lines that are sensitive to treatment with an agent and which are not expressed (or are expressed at a rather low level) in cells that are resistant to treatment with that agent. The invention also features a number of "resistance markers." These are markers that are expressed in most or all cell lines that are resistant to treatment with an agent and which are not expressed (or are expressed at a rather low level) in cells that are sensitive to treatment with that agent.