(A) Typical experiment showing the number of progenitor cells after retroviral transduction of CD34⁺ cells with PA317 alone (□), LNL6 (▨), or LNC(SCL) (▪). GM and erythroid colonies in the presence and absence of G418 (1.5 mg/mL active concentration) are shown. Agar cultures were established using 1,000 CD34⁺ cells and GM and erythroid colonies were quantitated in independent cultures using the appropriate growth factor combinations. Data points are the mean ± SD of triplicate cultures (in absence of G418) or 9-replicate cultures (in presence of G418). (B) Total number of G418R colonies per 1 × 10⁴CD34⁺ cells for 5 representative patient samples. Cultures were established in the presence of G418 (1.5 mg/mL) using a range of cell concentrations (1 × 10³ to 5 × 10⁴ CD34⁺ cells) after transduction with LNL6 (N) or LNC(SCL) (S). (▪) The number of GM colonies; (▨) the number of erythroid colonies. GM and erythroid colonies were quantitated in independent cultures. Each bar represents the mean from 9-replicate cultures. (C) The proportion of erythroid colonies grown in agar culture as a function of the total number of colonies obtained after the transduction of CD34⁺ cells with LNL6 or LNC(SCL). Each point represents an individual patient sample.