2. Tumor biopsy will be requested from all study subjects unless the procedure poses too great a risk. If the subject declines, he or she may still participate in the study. We will ask subjects not undergoing biopsy to provide 6 unstained slides or a tissue block of archived tissue for immunohistochemistry (IHC) evaluation. Tumors from subjects enrolling in the phase II portion of the study will be analyzed retrospectively to demonstrate mammalian target of rapamycin (mTOR) activation as assessed by immunohistochemistry in a fresh biopsy. mTOR activation will be defined using distribution and intensity of staining for phosphorylation of mTOR, or its downstream substrates S6 kinase (S6K), and S6. Standard operating procedures (SOPs) describing the acquisition and handling of PBMCs and tissues are outlined in appendix 10.3 and 10.4. At a minimum, a total score (sum of intensity and distribution scores) of 2 for phospho-S6 or phospho-mTOR (S2448) mTOR will be required to determine that mTOR is active. Either measurement will be sufficient to ascertain that mTOR is active. Measurement of phosphorylation of Akt, factor 4E binding protein 1 (4E-BP1), and total levels of thymidylate synthase (TS) will also be measured, but are not part of the eligibility requirements. In the event of limited tissue availability, the stains will be prioritized as follows: S6, mTOR, S6K, Akt (S473), Akt (T308), and TS. Phosphorylation of S6 correlates most closely with mTOR activity, while phosphorylation of mTOR at S2448 best predicts response to sirolimus.