The present invention provides methods for determining if an agent (i) treats or prevents cancer, (ii) treats or prevents obesity, and/or (iii) increases insulin sensitivity, comprising contacting Fyn and/or LKB1 with the agent and determining if the agent inhibits Fyn kinase activity or inhibits the interaction between Fyn and LKB1, wherein inhibition of Fyn kinase activity or inhibition of the interaction between Fyn and LKB1 by the agent indicates that the agent (i) treats or prevents cancer, (ii) treats or prevents obesity, and/or (iii) increases insulin sensitivity. The present invention also provides methods for treating cancer, treating obesity, or increasing insulin sensitivity in a subject, comprising administering to the subject a therapeutically effective amount of an agent that inhibits Fyn kinase or that inhibits the interaction between Fyn and LKB1.
