CORRELATION OF LOSS OF HETEROZYGOSITY WITH CYTOGENETIC ANALYSIS USINGG-BANDING AND FLUORESCENCE IN-SITU HYBRIDIZATION IN ANEUPLOID CULTURES FROM 2 HUMAN TESTICULAR GERM-CELL TUMORS

A detailed karyotype analysis using fluorescence in situ hybridization (FISH), with 24 chromosome-specific paint probes has been carried out on newly established cell lines from two testicular tumors, an i(12p) -positive teratoma, and an i(12p)-negative combined seminoma/teratoma. This has been correlated with loss of heterozygosity (LOH) and alleli c imbalance, using DNA RFLP analysis to clarify the genetic changes an d to identify any common regions of deletion or rearrangement. With G- banding alone, a total of 11 breakpoints were recognized. After FISH, the position of seven required revision, and al new ones were identifi ed. The chromosomes involved most frequently in both tumors were numbe rs 1, 12, and 18. Breakpoints in 11q and 16q were also seen in both, a nd seven or more copies of 12p per cell were found in all clones. LOH was found for 18q in both tumors, and overall was much more frequent i n underrepresented regions (one or two copies). On the whole, there wa s good agreement between the cytogenetic and DNA RFLP data; loci showi ng allelic imbalance generally had an odd number of copies of the chro mosome region in which they were known to be located. Combined data on the chromosome 1 translocations in both tumors suggested that rearran gements were more complicated than cytogenetics alone had predicted.