EVIDENCE OF ALLELIC IMBALANCE OF CHROMOSOME-6 IN HUMAN ASTROCYTOMAS

Transfer of human chromosome 6 can suppress the malignant phenotype of melanoma. Because of the neural ectoderm origin of melanoma and since up to 30% of gliomas have abnormalities involving chromosome 6, we performed restriction fragment length polymorphism analysis to determine the importance of allelic loss on chromosome 6 in gliomas. DNA samples from tumor and white blood cells were obtained from patients with pathologically verified gliomas. Of the 20 paired samples, there were two gangliogliomas and one grade I, four grade II, two tumors labeled ''low grade,'' two grade III, and nine grade IV astrocytomas. DNA was hybridized with polymorphic probes D6S29 (6p21), c-myb (6q23.3-24), SOD2 (6q25), D6S37 (6q26), and ESR (6q27). All grades of tumor revealed areas of genetic loss. Allelic imbalance (AI) was present in 11 of 47 (23%) of informative loci on 6q and four of seven (57%) on 6p. Loci at 6p21 and 6q26 were most often lost. In contrast, probes from three non-chromosome 6 loci demonstrated a combined total of 11% allelic loss. Genetic loss from chromosome 6 is a frequent event in glial neoplasms.