Evi1 can immortalize immature myeloid cells with high efficiency. Southern blot analysis of MSCV integrations in 5 immortalized cell lines (P1 to P5) generated by MSCV-Evi1 infection (10 μg/lane) and 11 cell lines subcloned from the P3 line (P3-1 to P3-11) (5 μg/lane) digested with BglII.