Effect of mammary tumors on hematopoiesis and clonogenicity. Mammary tumors alter BALB-neuT hematopoiesis and affect normal BALB/c BM cells' clonogenicity. (A) Phenotype of colonies from BM and spleen of individual BALB-neuT and BALB/c. (B) Effects of BALB-neuT serum and tumor supernatant on CFUs of normal BALB/c BM cells. Sca-1⁺ hematopoietic stem/progenitor–enriched BM cells seeded on irradiated AFT024 stromal cells were conditioned for 5 days with 10% serum from tumor-bearing BALB-neuT or normal BALB/c mice (▧); with supernatant from tumor cell lines (C26 colon carcinoma and N2C mammary carcinoma) or from primary cultures of mammary BALB-neuT carcinomas (□), at the indicated concentrations; or with medium alone (▪). Cells were recovered and scored for CFUs in methylcellulose at day 10 (mean of 4 replicates ± SD). **P < .05 indicates statistically significant differences from control.