INVIVO AND INVITRO EXPRESSION OF OCTAMER BINDING-PROTEINS IN HUMAN-MELANOMA METASTASES, BRAIN-TISSUE, AND FIBROBLASTS

The pattern of octamer sequence-specific DNA binding proteins expresse d in human melanoma was examined in nuclear extracts of seven surgical ly isolated tumors, short-term cultures of these tumors, and 25 human melanoma cell lines to determine the in vivo and in vitro distribution of the melanocytic-associated Oct-M1 and Oct-M2 octamer binding activ ities. In the biopsy tissue and cultured melanoma cells of a metastasi s from the cerebellum, two other binding activities (N-Oct-2 and N-Oct -6) in addition to the Oct-M1, Oct-M2 and the generally expressed Oct- 1 protein were detected; this profile was consistent with that seen in normal human and mouse brain tissue. Melanoma tissue removed from lym ph nodes and cell lines established from them also showed Oct-1, Oct-M 1, Oct-M2, and N-Oct-2. N-Oct-2 was distinguished from the comigrating Oct-2A activity by failure to react with Oct-2A-specific antibody. Al l but one of the 25 melanoma cell lines exhibited Oct-1, Oct-M1, and O ct-M2 and/or N-Oct-2 activity, whereas cultured normal melanocytes exp ressed only Oct-1 and Oct-M1. In contrast to murine fibroblasts, which express only Oct-1, human fibroblast strains also expressed Oct-2A bi nding activity, which was confirmed by reactivity with Oct-2A antibody and the presence of Oct-2A mRNA and indicated that Oct-2A has a more general role than that of a lymphoid-specific transcription factor. Ov erall, the results indicate that expression of neural-specific Oct fac tors in human melanoma is (1) aberrant compared with normal melanocyte s, (2) can be modulated by the surrounding tissue in a brain metastasi s, and (3) may be part of the altered program of differentiation accom panying transformation.