Three types of Bloom syndrome B-lymphoblastoid cell lines, as well as one derived from a normal person, treated with 4-nitroquinoline-N-oxide and N-methyl-N'-nitro-N-nitrosoguanidine (0.3 micrograms/ml for 24 hr), were studied for tumorigenicity in nude mice, colony formation in soft agar, cytogenetic changes, and immunoglobulin markers. When normal and Bloom syndrome cells with normal sister c...