ANALYSIS OF C-ERBB-2 AMPLIFICATION IN SALIVARY-GLAND TUMORS BY DIFFERENTIAL POLYMERASE CHAIN-REACTION

DNA samples extracted from 22 normal salivary glands, 38 salivary pleo morphic adenomas and 20 other salivary gland neoplasms were screened f or amplification of the c-erbB-2 oncogene by a differential polymerase chain reaction (PCR). The samples were PCR amplified with primers spe cific for the c-erbB-2 oncogene and for a reference gene (interferon-g amma). A breast carcinoma cell line SKBR-3 known to contain c-erbB-2 a mplification was used as positive control. Following gel electrophores is, the intensity of the amplified DNA bands was determined by laser d ensitometry and the level of amplification of the c-erbB-2 oncogene wa s assessed from the intensity of the c-erbB-2 specific band relative t o that of the interferon-gamma band. Of all the tumours detected, only the two poorly differentiated adenocarcinomas, two of the pleomorphic adenomas and one of the Warthin's tumours showed gene amplification a t levels comparable to the breast carcinoma cell line. None of the nor mal salivary gland tissues was found to have amplification. Within the group of pleomorphic adenomas the average level of amplification was not significantly different from that observed in the normal salivary gland, or in total genomic DNA from unrelated tissue (P less-than-or-e qual-to 0.001, determined by a general linear model of statistical ana lysis). These results indicate that amplification of the c-erbB-2 onco gene is infrequent in salivary neoplasia. Thus, gene amplification alo ne cannot account for the high prevalence of c-erbB-2 overexpression d emonstrated previously in salivary gland tumours. When present, c-erbB -2 amplification may be associated with a more aggressive behaviour.