MKI67 and neuroendocrine carcinoma: Although the GEP-NET cell lines NT-18P, NT-18LM and NT-36 displayed a significantly lower Ki67 positivity than the GEP-NEC cell lines NT-32 and NT-38, we observed only slightly higher doubling times of 7.09 days (95% CI: 5.43; 9.48) for NT-36 cells, 6.35 days (95% CI: 4.87; 8.42) for NT-18LM cells and 4.64 days (95% CI: 4.15; 5.20) and for NT-18P cells (Fig. 2B).