2. ASS1 deficiency (defined as ≤50% ASS expression) demonstrated on tissue specimen (cytospin samples are acceptable) by immunohistochemistry (IHC). For subjects previously treated with chemotherapy, this specimen may have been obtained before that chemotherapy. A new tissue specimen obtained after most recent chemotherapy is not required. Thus ASS1 deficiency is required for entrance into the study. If tissue is not available to determine ASS1 deficiency, then tissue must be obtained by biopsy to determine ASS1 status.