Expression analysis of the PMP22 gene in glioma and osteogenic sarcoma cell lines

Previously we reported the amplification of the peripheral myelin protein 22 (PMP22) gene in cell lines of human osteogenic and glioma tumors. PMP22 normally is expressed at high levels in Schwann cells of the peripheral nervous system and is suggested to function as a structural protein of the myelin sheath. One of the most common inherited peripheral neuropathies, Charcot-Marie-Tooth Type 1A (CMT1A), is associated with a duplication of a 1.5-Mb DNA region on chromosome 17p11.2 - p12 containing PMP22. On the other hand, PMP22 is identical to gas3, whose expression is induced in growth-arresting NIH3T3-fibroblasts and is thought to play a role in cell proliferation. The precise role of gas3/PMP22 remains to be determined. Here we show that in the tumor cell lines RH30 and SF763 the amplified region including PMP22 comprises the whole 1.5-Mb CMT1A region. We could prove expression of PMP22 by reverse transcriptase-polymerase chain reaction (RT-PCR) and discovered an unusual PMP22 transcript in these tumor cell lines. Western blot analyses resulted in detection of a 22-kDa protein by the PMP22-specific antibody 558/2 and in exclusion of myelin protein zero (MPZ) expression in these cell lines.