Differential Expression of c-myc Gene and c-fos Gene in Premalignant and Malignant Tissues from Patients with Familial Polyposis Coli1

The expression of 8 oncogenes and the structures of 19 oncogenes were analyzed in 15 adenocarcinomas (12 primary and 3 metastatici, 18 adenomatous polyps, and 18 normal colonie mucosae derived from 19 patients with familial polyposis coli. The expression of c-myc gene was most elevated in carcinoma, and moderately elevated in adenoma, com pared with corresponding normal colonie mucosa. In contrast, the expres sion of c-fos gene was markedly decreased in all samples of adenoma and carcinoma, compared with that of normal colonie mucosa. These char acteristic expression patterns of c-myc and c-fos genes were revealed not only in familial polyposis coli but also in cases of nonhereditary colon carcinoma. Structures of the 19 oncogenes were not modified in either adenoma or carcinoma, except for amplification of the c-myc gene de tected in one carcinoma, but not in adenoma, from the same patient. Analyses of the amplified c-myc gene suggest that gene duplication may relate to the mechanism of gene amplification. Thus, the enhanced expression of c-myc gene in adenoma and carcinoma may reflect the proliferativi' activity, while the c-fos gene may be a prerequisite to stabilize the state of terminal differentiation of colonie epithelial cells. INTRODUCTION FPC,3 which is inherited as an autosomal dominant trait with an extremely high penetrance, is characterized by the develop ment of numerous adenomatous polyps in the colon and rectum early in life. These adenomatous polyps usually develop before age 20 years and will often progress to an adenocarcinoma by age 40 years. This is in contrast to an average of 50-60 years for the occurrence of sporadic colorectal carcinoma in the general population. The frequency of FPC is estimated to be 1 of every 8,000 to 10,000 births. These polyps, apparently caused by a single genetic factor, are assumed to be precursor lesions for malignant tumors of the colon and rectum. It is also ac cepted that adenomatous polyps of nonhereditary cases are major premalignant lesions of the colon and rectum in the general population. Therefore, analysis of carcinogenesis in FPC is important for an understanding of the molecular mech anism of the carcinogenesis of colorectal carcinoma. The major gene involved in FPC is located on chromosome 5 (1). In cases of sporadic colorectal carcinoma, an alÃ-eleloss of chromosome 5 or chromosome 17 was detected in about 23% (2) or 75% (3), respectively. Recently, we also observed an alÃ-eleloss of chro mosome 5 or chromosome 22 in about 50 or 36%, respectively, of colorectal carcinoma from patients with FPC (4). Therefore the loss of a normal alÃ-eleat the specific locus on these chro mosomes may be critical in carcinogenesis of the colorectum. In other hereditary cancers or embryonal cancers, mutation of the specific locus at homozygous or hemizygous state seems to Received 12/23/87; revised 5/11/88; accepted 6/3/88. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. ' This work was supported in part by Grants-in-Aid for Cancer Research 60010032, 60015072, 61010033, 61015078. 62010031, and 62015059 from the Ministry of Education, Science and Culture, Japan, and by a Grant-in-Aid from Fukuoka Cancer Society. 2To whom requests for reprints should be addressed. ' The abbreviations used are: FPC, familial polyposis coli; MHC, major histocompatibility complex; SSPE, 0.75 M NaCl-0.05 M NaH2PO<-5 min EDTA. produce cancer, as noted in cases of retinoblastoma (5, 6), Wilms' tumor (7), and related embryonal tumors (8). These genes may play an important role to modulate oncogenes, such as the N-myc gene in retinoblastoma. It has been suggested that certain cellular oncogenes are associated with cellular proliferation, carcinogenesis, and tumor progression (9). Extensive studies on the structure and expres sion of the oncogenes were performed in various tumor cell lines as well as in solid tumors (10-12). The accumulated data suggest associations between characteristic alterations of spe cific oncogenes and certain types of tumor, including Burkitt lymphoma (13, 14), neuroblastoma (15, 16), retinoblastoma (17), small cell carcinoma of lung (18), and breast cancer (19). Moreover, amplification of the N-myc gene in neuroblastoma or that of the HER-2/neu gene in breast cancer correlates with tumor progression and prognosis of the disease (19-21). In colorectal carcinoma, it was reported that the expression of cmyc, c-fos, c-H-ras, and c-K-ras genes was elevated (12). A high incidence of mutation of the c-K-ras gene was noted in colorec tal carcinoma and also in adenoma (22, 23). We examined the expression and structure of oncogenes and MHC genes in 51 specimens of adenocarcinomas, adenomatous polyps, and corresponding normal colonie mucosa derived from 19 patients with FPC, the objective being to determine whether there is a gene highly expressed or activated especially in adenomatous polyps or in adenocarcinomas from patients with FPC. We now report that 62% of the adenomatous polyps and 75% of adenocarcinomas revealed an elevated expression of the c-myc gene compared with corresponding normal colonie mu cosa. In contrast, all of adenomatous polyps and adenocarci nomas showed a decreased expression of the c-fos gene com pared with corresponding normal colonie mucosa. These char acteristic expression patterns of c-myc and c-fos genes were also demonstrated in cases of nonhereditary colon carcinoma. These observations suggest that the c-myc gene might be involved in cellular proliferation, while the c-fos gene may be a prerequisite to stabilize the terminal differentiation of colonie epithelial cells. MATERIALS AND METHODS Samples. Tissue specimens were collected from 19 Japanese patients with FPC: 12 adenocarcinomas in colorectum; 1 metastatic carcinoma in lung; 2 metastatic carcinomas in liver; 18 adenomatous polyps; and 18 normal colonie mucosa (Table 1). Adenocarcinomas and correspond ing normal colonie mucosa were collected from 5 patients with nonhereditary colon carcinoma. Normal colonie mucosa was obtained by dissecting the mucosa from the muscularis propria, after resection of polyps macroscopically. These tissues were frozen in liquid nitrogen immediately after excision and stored until use in this study. Plasmid DNAs. Plasmid DNAs used in this study were provided by the following scientists: pT22-H-ros by Y. Sakaki; pfos-l(v-fos) by I. M. Verma; pSSV-1 l(v-iw) by S. Aaronson; c-fes by Tak W. Mak; pDRal l(HLA-DRa) by H. Inoko; /3-actin by T. Kakunaga; pHSRlfcmyc) by Oncor. pH¡H¡3(v-K-ras), pSW9-7(N-rÃ1⁄4Ã-), pN-myc, #6929(Lmyc), pHuB/y/nl, pHM2A(c-mos), pKX044(c-<?reS-2), p/#r39-l, pSM3(v-/ms), pv-roi, 3611E-H(v-ro/), pmyb, p-\-abl, pPvuIIE(v-irc),