Recurrent homogeneously staining regions in 8p1 in breast cancer and lack of amplification of POLB, LHRH, and PLAT genes.

In a cytogenetic study of 125 primary and untreated breast cancers, 107 were selected for the quality of their metaphases permitting detection of amplifications:homogeneously staining regions (HSRs), abnormally banded region (ABRs), and double minutes (dmins). HSRs and ABRs were detected in 62 cases (58%), but no cases of dmins were observed. The localizations of HSRs and ABRs were not random because they were observed in the 8p1 position in 14 cases. The possible amplifications of five sequences, MOS (8q1), LHRH (8p21.1), POLB (8p11.2), PLAT (8p12), and D8Z2 (8c) were investigated in three tumors with HSR on the short arm of chromosome 8. Because these sequences were not amplified, two interpretations can be proposed: 1) there is a frequent amplification of a sequence from the 8p1 region, located between the investigated sequences; and 2) the amplifications do not occur in 8p1, but HSRs or ABRs of undetermined origin have a strong tendency to be translocated onto 8p. Because cases with HSR(8p) have less complex karyotypes than with HSRs in other locations, the first interpretation is the most likely: HSRs may be formed in 8p and further translocated on other chromosomes in the course of tumor progression.