Characterization of a complex chromosome rearrangement involving 6q in a melanoma cell line by chromosome microdissection.

Deletion of 6q is one of the most frequent chromosomal alterations in human malignant melanoma. Recently, we used chromosome painting probes of 6p and 6q to study 21 melanoma cell lines. A reciprocal translocation between chromosomes 6q and 17p was detected in one cell line (UACC-930). Upon further characterization of the translocation marker using the micro fluorescence in situ hybridization (FISH) technique, a complex rearrangement including an inversion of 6q and a translocation between the inverted 6q and 17p, [der(6)inv(6)(q16q27)t(6;17)(q26;p13)], was detected. A yeast artificial chromosome (YAC) clone spanning the breakpoint at 6q16 was isolated by the FISH screen. Loss of one or more copies of the YAC clone was also detected in 10 of 12 melanoma cell lines. This result implies that the YAC clone may contain a putative tumor suppressor gene related to the pathogenesis of malignant melanoma. Further characterizations of the breakpoint at 6q16 and molecular cloning breakpoints at 6q27 and 17p13 are in progress.