I. To evaluate the toxicity of combination therapy with AMG 337 (c-Met inhibitor AMG 337) and mFOLFOX6 (oxaliplatin, leucovorin calcium, and fluorouracil) chemotherapy in patients with advanced or metastatic gastrointestinal (GI) cancers. (Phase I) II. To determine the dose of AMG 337 to be used in combination with mFOLFOX6 chemotherapy in the phase II portion of the trial. (Phase I) III. To determine the pharmacokinetics of AMG 337 in combination with mFOLFOX6. (Phase I) IV. To determine if the addition of AMG 337 to mFOLFOX6 chemotherapy improves median progression-free survival (PFS) in the first line treatment of patients with human epidermal growth factor receptor 2 (Her2Neu) negative and high c-met proto-oncogene (MET) expressing advanced esophagogastric and gastroesophageal junction (GEJ) adenocarcinoma. (Phase II)