Another form of cancer turns out to have a core of stem cells that can be targeted: "the research team generated cellular models of drug resistance by treating prostate tumor cell lines with increasing doses of the common chemotherapy drugs, including docetaxel. They identified a cell population expressing markers of embryonic development. In addition, these cells displayed cancer stem cell functions, including the capacity to initiate tumor cell growth. Next, the team evaluated human tissue samples of prostate cancer and found that patients with more aggressive or metastatic tumors had more of these cancer 'stem' cells. ... The study also defines a new therapeutic strategy for patients with prostate cancer, consisting of a combination of standard chemotherapy and two pharmacological agents that inhibit key signaling pathways associated with embryonic development and cell differentiation. Results showed that chemotherapy eliminated differentiated tumor cells, whereas the signaling pathway inhibitors selectively depleted the cancer stem cell population. Some of these inhibitors are already in clinical trials, and some are FDA-approved. ... By targeting these newly identified cancer 'stem' cells, we are attacking the foundation of tumor growth, rather than treating the symptoms of it."