From tumor to treatment. Molecular profiling of tumors can lead to the identification of key signal transduction pathways that may be dysregulated in a specific type of tumor (steps 1-4). In vitro studies on tumor cells can validate that the signaling pathway is aberrantly activated or inactivated in such a way that it favors cell growth, survival, and proliferation (step 5). Such studies may reveal that these signaling pathways are altered most frequently and to the greatest extent in the more aggressive forms of the tumor. A critical in vitro test is whether drugs that modulate the pathway that is dysregulated in these tumors can inhibit the survival, growth, or metastasis of the cells (step 6). Encouraging in vitro results can pave the way for clinical trials and new treatments (steps 7-8). The eventual goal would be to test tumor biopsies for characteristic tumor signatures and, based on the results, initiate the appropriate treatment (dashed line). With regard to mantle cell lymphoma, the paper by Rudelius and colleagues in this issue of Blood makes significant advances in terms of steps 5 and 6. Parts of this figure reproduced by permission. Originals, © 2003 Massachusetts Medical Society¹  and © 2001 The Rockefeller University Press.²