Eur J Cannr C/m Onco~, Vol. 24. No. 8, pp. 1321-1328, 1988. Printed m Great Britam Nuclear Oncogene Amplification or Rearrangement is not Involved in Human Colorectal Malignancies zyxwvutsrqponmlkji RICCARDO DOLCETTI, VALLI DE RE, ALESSANDRA VIEL, MAURO PISTELLO. MANUELA TAVIAN and MAC‘RO BOIOCCHI* zyxwvutsrqponm Experimental Oncology 1, Centro di Rifrimento Oncologico, bi’ a Pedemontana Occidentale, 3308 1 .4z~inno (Pordenone), It& Abstract-We have examined 44 cases of human colonic and rectal carcinomas for structural rearrangement and amplification of c-myc, N-myc, L-myc, c-myb and ~53 oncogenes. L)Iv~~)~ hybridization showed evidence of c-myc amplrfication in only one of the samples tested. In addition, the same tumour also showed a rearrangement immediately 3’ to the c-myc locus. No rearrangement could be found at the c-myc locus in the other 43 cases. Moreover, our molecular analp~is of S- myc, L-myc, c-myb and ~53 genes indicated no relevant alteration of the copy number and/or genomic structure of these nuclear oncogenes. Thus, at least in human colorectal malignancies, it is unlikely that nuclear oncogene structural alterations and/or ampl$cation plays a major role in tumour induction or progression. INTRODUCTION CELLULAR proto-oncogenes have been identified by their homology to the oncogenic sequences of acutely transforming retroviruses or by DNA- mediated gene transfer techniques [ 1, 21. Evidence suggests that proto-oncogene-encoded proteins may represent components of the signalling pathways through which growth factors and mitogens exert their effect on cells. By such pathways, growth stimulating signals are conveyed through mem- brane receptors and cytoplasmic proteins to the nucleus, where a proliferative response may bc induced. As part of this picture, nuclear proto- oncogene products are surmised to play a central role in regulating cell proliferation and differen- tiation [3, 41. Although the relationship between cellular proto- oncogene activation and the development of the neoplastic state remains to be elucidated, it appears that structural or regulatory alterations of c-one genes are involved in tumour formation and/or progression. Modifications in the pattern of nuclear oncogene expression by gene amplification, retrovi- ral insertion or chromosome translocation have been frequently demonstrated in several human tumours and tumour cell lines [5-lo]. The myc proto-oncogene family has three well- characterized members, c-myc, N-myc and L-myc, which share similar structural features [ 1 l-l 41. Accepted 8 March 1988. *Author to whom correspondence and reprint requests should be sent. Nevertheless, this gene grouping not only reflects a structural kinship but also suggests that these kin- dred sequences may have related functions. The c- myc oncogene has been found to be translocated in lymphomas [5, 151 and amplified in the HL60 promyelocytic leukaemia cell line [ 161. In addition, this oncogene is amplified and overexpressed in mammary, lung and colon carcinoma ccl1 lines [7, 9, lo]. Particularly interesting is the finding of the amplification ofN-myc and L-myc genes, which have been correlated to the clinical stage and the progression of neuro- and rctinoblastomas and lung cancers [ 10, 17, 181. Increased expression of the c- myc gene seems to occur frequently in human colonic carcinomas [ 19-201. Amplification of c-myc with ovcrcxpression of this gene has initially been found in a human colonic cancer cell line with neuroendocrine properties (Co10 320) but there was no evidence of rearrangement or amplification of the myc locus in a group of 29 primary human colon carcinomas [ 191. We carried out similar analyses on c-myc and four other nuclear oncogenes (N-myc, L-myc, c- myb, ~53) to evaluate the real importance of struc- tural alterations of such gents in human colorectal malignancies. MATERIALS AND METHODS Normal and neoplastic tissues Normal and neoplastic tissues were collected from 24 patients with adenocarcinoma of the colon and from 20 patients with adcnocarcinoma of the rec- 1321