Immunotherapy for Solid Tumor Malignancies in Pediatrics Using Interleukin-15 and -21 Armored Glypican-3-specific Chimeric Antigen Receptor T Cells

1. Procurement Eligibility Inclusion Criteria: * Diagnosis of a solid tumor expressing GPC3 * Lansky or Karnofsky score of \>=60% * Life expectancy of \>16 weeks * Informed consent explained to, understood by and signed by patient/guardian. For patients with hepatocellular carcinoma only: * Barcelona Liver Cancer Stage A, B or C * Child-Pugh Turcotte Score \<7 Exclusion Criteria: * History of hypersensitivity reactions to murine protein-containing products OR presence of human anti-mouse antibody (HAMA) prior to enrollment for patients who have received prior therapy with murine antibodies. * History of organ transplantation * Known HIV positivity * Active bacterial, fungal, or viral infection (except Hepatitis B or Hepatitis C virus infections) 2. Treatment eligibility Inclusion Criteria: * Lansky or Karnofsky score of \>=60% * Life expectancy of \>16 weeks * Informed consent explained to, understood by and signed by patient/guardian. * Adequate organ function * Adequate laboratory values * Refractory or relapsed disease after treatment with up- front therapy and at least one salvage treatment cycle * Recovered from acute toxic effects of all prior chemotherapy and investigational agents before entering this study * Sexually active patients must be willing to utilize one of the more effective birth control methods for 12 months after the T-cell infusion. * Informed consent explained to, understood by and signed by patient/guardian. For patients with hepatocellular carcinoma only: * Barcelona Liver Cancer Stage A, B or C * Child-Pugh Turcotte Score \<7 Exclusion Criteria: * History of hypersensitivity reactions to murine protein-containing products OR presence of human anti-mouse antibody (HAMA) prior to enrollment for patients who have received prior therapy with murine antibodies. * History of organ transplantation * Known HIV positivity * Active autoimmune or inflammatory disorder * Live vaccines within 30 days prior to enrollment • Active bacterial, fungal, or viral infection (except Hepatitis B or Hepatitis C virus infections) * Pregnancy or lactation * Uncontrolled infection * Systemic steroid treatment (≥ 0.5 mg prednisone equivalent/kg/day, dose adjustment or discontinuation of medication must occur at least 24hrs prior to CAR T cell infusion) * Congestive heart failure (as defined by New York Heart Association Functional Classification III or IV), unstable angina, serious uncontrolled cardiac arrhythmia, a myocardial infarction within 6 months prior to study entry or a history of myocarditis.