This invention relates, e.g., to a method for predicting the response of a subject having estrogen-receptor-positive breast cancer to an inhibitor of the estrogen signaling pathway (e.g. tamoxifen), comprising measuring in a cancer sample from the subject the level of phosphorylation, compared to a baseline value, of one or more of the following members of an interconnected intracellular signaling pathway: (a) 4EBP1, and/or (b) p70S6, and/or (c) STAT3, and/or (d) FAK, wherein a significantly elevated level of phosphorylation of 4EBP1, and/or p70S6 and/or STAT3, and/or a significantly decreased level of phosphorylation of FAK, compared to the baseline value, indicates that the subject is likely to be a non-responder to the inhibitor and/or has a poor prognosis. Additional members of the intracellular signaling pathway whose phosphorylation can be measured are also described. Also described is a method for treating breast cancer in a subject in need thereof, wherein the subject exhibits an elevated level of phosphorylation of these markers, comprising administering to the subject an effective amount of one or more inhibitors of members of the interconnected intracellular signaling pathway.