Fourteen colorectal cancer cell lines, categorized according to the presence or absence of microsatellite instability, were further analysed for chromosomal stability by karyotyping. NonRER (microsatellite stable) cell lines typically displayed highly aberrant karyotypes with alterations not only of chromosome number but also of chromosome structure including chromosomal deletions, inversions, and translocations. RER (microsatellite unstable) cell lines, in contrast, displayed significantly fewer alterations of chromosome number. Moreover, RER cell lines also displayed significantly fewer cytogenetically evident alterations of chromosome structure. Compared to NonRER colon cancers, RER colon cancers are significantly less likely to have undergone chromosomal gain, loss, or breakage. Characterization of p53 gene status by gene sequencing was performed in an attempt to determine if p53 gene status correlated with the chromosomal stability of the RER cancers. Gene mutations in p53 were present in all of the NonRER colon cancers. However, p53 gene mutations were also found present in four of nine of the RER colon cancers. Unexpectedly, RER colon cancers bearing mutant p53 demonstrated the same stability of chromosome number, and the same stability of chromosome structure, as the RER colon cancers with wild-type p53. Therefore, in RER colon cancers specific p53 independent mechanisms actively maintain the stability of both chromosome number and structure.

We describe the spontaneous progression of a colon adenoma cell line to tumorigenicity and growth factor independence. This system allows direct comparison of biologic stages of malignant progression with alterations of colon cancer suppressor genes and oncogenes. VACO-235, a human colon adenoma cell line, is at early passages nontumorigenic in the nude mouse, unable to grow in soft agar, growth stimulated by serum and EGF, and growth inhibited by TGF-beta. VACO-235 daughter passages 93 and higher have in culture spontaneously progressed to being weakly tumorigenic, but retain all other growth characteristics of VACO-235 early passages. A mouse xenograft from late passage VACO-235 was reestablished in culture as the granddaughter cell line, VAC0411. VAC0411 is highly tumorigenic, clones in soft agar, and is unresponsive to serum, EGF, and TGF-beta. Early passage VACO-235 bears a mutant K-ras allele, bears only mutant APC alleles, expresses no DCC transcripts, and expresses only wild type p53 transcripts. VACO-411 retains the identical genotype, still expressing only wild type p53. Colonic cells after ras mutation, APC mutation, and DCC inactivation remain nontumorigenic and growth factor dependent. Malignant progression involves at least two additional steps, and in VAC0411 can proceed by a novel pathway not requiring p53 inactivation. (J. Clin. Invest. 1994. 93:1005-1013

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Leukemic relapse following bone marrow transplant (BMT) is generally due to the recurrence in recipient cells, but may rarely occur as a result of donor cell transformation. Donor cell relapse is generally identified using cytogenetic markers such as the sex chromosomes. Recently, molecular techniques have been used to identify the origin of bone marrow cells by their DNA restriction fragment length polymorphisms. We describe the case of a male pediatric patient who had a leukemic relapse 30 months following BMT from his sister. Both cytogenetic and molecular techniques were used to identify the origin of the leukemic relapse. Cytogenetic analyses indicated the absence of the Y chromosome and the presence of a donor cell type 9qh polymorphism, suggesting a donor cell relapse. Molecular analyses also indicated the absence of the Y chromosome but demonstrated the recurrence of recipient DNA markers from three other chromosomes, suggesting a recipient cell relapse. While the leukemic cell lineage cannot be definitively assigned in this case, our results suggest that caution must be exercised when assigning leukemic cell lineage following post-BMT relapse.

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Leukemic relapse following bone marrow transplant (BMT) is generally due to the recurrence in recipient cells, but may rarely occur as a result of donor cell transformation. Donor cell relapse is generally identified using cytogenetic markers such as the sex chromosomes. Recently, molecular techniques have been used to identify the origin of bone marrow cells by their DNA restriction fragment length polymorphisms. We describe the case of a male pediatric patient who had a leukemic relapse 30 months following BMT from his sister. Both cytogenetic and molecular techniques were used to identify the origin of the leukemic relapse. Cytogenetic analyses indicated the absence of the Y chromosome and the presence of a donor cell type 9qh polymorphism, suggesting a donor cell relapse. Molecular analyses also indicated the absence of the Y chromosome but demonstrated the recurrence of recipient DNA markers from three other chromosomes, suggesting a recipient cell relapse. While the leukemic cell lineage cannot be definitively assigned in this case, our results suggest that caution must be exercised when assigning leukemic cell lineage following post-BMT relapse.

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