This study will analyze and evaluate the following items: The safety of natural killer（NK） cells for treatment of subjects with solid tumors. Forty patients will be enrolled for each of the five cancers (in total 200 patients will be enrolled). The effectiveness of natural killer（NK）cell therapy alone or with chemotherapy or targeted drugs. Subjects from 18 to 75 years of age who are diagnosed with a solid tumor including pancreatic cancer, lung cancer, breast cancer, ovarian cancer and colon cancer, and for whom standard treatments are not effective, may be eligible for this study. Participants undergo the following procedures: Peripheral blood will be collected from a vein of arm. Peripheral blood mononuclear cells（PBMC） will be isolated and purified for NK manufacturing. After 14~21 days cultivation, activated NK will be harvested and formulated for clinical administration. Subjects will receive NK cell treatment by intravenous infusion. The frequency is once every 3 or 4 weeks for the first 3 months. Participants who respond well after 3 months may be eligible to continue NK cell therapy; and those not may receive NK therapy combined with chemotherapy and/or targeted drugs, or chemotherapy/targeted drugs alone. Evaluations during therapy including: Clinical assessment, and history of medications; Blood draws for routine and research tests, including but not limited to: lymphocyte population and circulating tumor cell analysis in peripheral blood; CT scan, bone scan and positron emission tomography（PET ）scan, if indicated, for disease evaluation; Pharmacokinetics study after NK infusion. For this test, the number of NK cells in the blood is measured over time at indicated time-points.