MKI67 and nasopharyngeal carcinoma: In addition, Ki67 staining on retinal sections from the optimal 60 K dose group showed limited positive cells at 7 and 30 days post-injection, and no positive cells at 180 days (Additional file 3: Table S3C), demonstrating that clinical-grade CNS10-NPC product were not proliferative and were non-tumorigenic.