This Phase I, open-label, multicenter study will evaluate the pharmacokinetics, safety, and preliminary anti-tumor activity of atezolizumab as monotherapy in Chinese participants with locally advanced or metastatic gastric cancer, nasopharyngeal cancer, esophageal cancer, and hepatocellular carcinoma (HCC) that are refractory to standard therapeutic modalities and for whom no further standard therapy is available or who have refused standard therapy; and the safety and preliminary anti-tumor activity of atezolizumab in combination with gemcitabine and cisplatin in Chinese participants with Stage IV, treatment-naive non−small cell lung cancer (NSCLC). The study will consist of a pharmacokinetic (PK) phase and an extension phase.