Putative tumor suppressor genes can be mapped to specific chromosomes by the introduction of individual chromosomes derived from normal cells via microcell fusion. We have examined whether a highly malignant human uterine endometrial carcinoma cell line, HHUA, can be suppressed by only one normal chromosome or by multiple chromosomes. A library of mouse A9 clones containing different human chromosomes tagged with the pSV2-neo plasmid DNA were constructed. Transfer by microcell fusion of either chromosome 1, 6, 9, 11, or 19 into the HHUA tumor cell line was performed, and the abilities of the microcell hybrids to form tumors in nude mice were examined. The introduction of a chromosome 19 had no effect on the tumorigenicity of the cells, whereas microcell-hybrid clones with an introduced chromosome 1, 6 or 9 were completely suppressed for tumorigenicity. A decrease in tumor-take incidence in some but not all clones was observed following the introduction of a chromosome 11. The nontumorigenic microcell hybrids with an introduced chromosome 1 differed from the nontumorigenic microcell hybrids with an introduced chromosome 6, 9, or 11. A large percentage of hybrids with chromosome 1 senesced and/or showed alterations in cellular morphology and transformed growth properties in vitro. No growth or morphology alterations were observed following transfer of the other chromosomes. These results may indicate that more than one chromosome carries a tumor suppressor gene(s) for this human uterine endometrial carcinoma cell line and support the hypothesis that multiple tumor suppressor genes control the tumorigenic phenotype in the multistep process of neoplastic development.