NDV strain Ulster, which is nonlytic, has also been shown to replicate efficiently in human cancer cells in vitro, including cells of the following types of human tumors:
- Colorectal carcinoma.
- Gastric carcinoma.
- Pancreatic carcinoma.
- Bladder carcinoma.
- Breast carcinoma.
- Ovarian carcinoma.
- Renal cell carcinoma.
- Lung carcinoma.
- Larynx carcinoma.
- Cervical carcinoma.
- B-cell lymphoma.
- T-cell lymphoma.
This strain does not replicate very efficiently in resting or proliferating normal human white blood cells in vitro. Other experiments have shown that NDV Ulster can kill infected cells  Reviewed in  and that it can replicate in human cancer cells whether they are actively proliferating or not. Reviewed in 
The ability of lytic strains of NDV to kill human cancer cells in vivo has also been examined. In xenograft studies, human cancer cells were injected either subcutaneously or intradermally into athymic, nude mice (i.e., mice that do not reject tumor cells from other animals because they have a defective immune system), and tumors were allowed to form. NDV was injected directly into the tumors, and tumor growth and animal survival were monitored.
Intratumoral injection of strain 73-T was associated with complete tumor regression in 75% to 100% of mice bearing human fibrosarcoma, neuroblastoma, or cervical carcinoma tumors.[1,2,3,10] Intratumoral injection of 73-T was also associated with more than 80% tumor regression in 66% of mice bearing human synovial sarcoma tumors. In addition, intratumoral injection of 73-T was associated with 68% to 96% inhibition of tumor growth in mice bearing human epidermoid, colon, lung, breast, or prostate carcinoma tumors.
Intratumoral injection of strain Italien was associated with complete tumor regression in 100% of mice bearing human melanoma tumors. The growth of metastatic tumors in these animals, however, was not affected, suggesting that the virus was unable to disseminate widely throughout the body. Reviewed in [14,20]
Replication of strain 73-T in the above-mentioned neuroblastoma xenografts was demonstrated by showing an increase in the amount of virus that could be recovered from tumor samples over time. When this strain was injected into the thigh muscle of athymic, nude mice, the amount of virus that could be recovered decreased with time, a finding consistent with the proposal that NDV replicates much more efficiently in cancer cells than in most normal cells.