Low grade amplification of MDM2 gene in a subset of human breast cancers without p53 alterations

MDM2 protein is thought to bind to p53 tumor suppressor protein leading to inhibition of p53-mediated transactivation. Amplification of the MDM2 gene has been frequently observed in human sarcoma, and relevant overexpression of the MDM2 protein is assumed to contribute to tumorigenesis through inactivation of the p53 function. In order to determine whether MDM2 amplification plays a role in the development of human breast cancer without genetic alteration of p53, we analyzed, MDM2 gene amplification by quantitative hybridization and genetic alteration of p53, in 32 primary tumors and 26 metastatic lymph nodes. Low grade amplification of the MDM2 gene (2-6 fold) was observed in four cases, none of which showed even subtle genetic alterations of p53 or loss of alleles on 17p. Moreover, in three of the four cases with MDM2 gene amplification, the level of gene amplification in the metastatic lymph nodes was slightly higher than that in the primary tumors. These results, taken together with previous findings, suggest that a subset of breast cancers without genetic alteration of p53 may also arise by inactivation of the p53 function through interaction with the overexpressed MDM2 protein induced by gene amplification.     

Mutations of a novel human RAD54 homologue, RAD54B, in primary cancer.

Association of breast tumor susceptibility gene products BRCA1 and BRCA2 with the RAD51 recombination protein suggested that cancer could arise through defects in recombination. The identification of NBS1, responsible for Nijmegen breakage syndrome, from the MRE11/RAD50 recombination protein complex also supports this hypothesis. However, our mutation analysis revealed that known members of the RAD52 epistasis group are rarely mutated in human primary cancer. Here we describe the isolation of a novel member of the SNF2 superfamily, characterized with sequence motifs similar to those in DNA and RNA helicases. The gene, designated RAD54B, is significantly homologous to the RAD54 recombination gene. The expression of RAD54B was high in testis and spleen, which are active in meiotic and mitotic recombination. These findings suggest that RAD54B may play an active role in recombination processes in concert with other members of the RAD52 epistasis group. RAD54B maps to human chromosome 8q21.3-q22 in a region associated with cancer-related chromosomal abnormalities. Homozygous mutations at highly conserved positions of RAD54B were observed in human primary lymphoma and colon cancer. These findings suggest that some cancers arise through alterations of the RAD54B function.     

Correlation of loss of alleles on the short arms of chromosomes 11 and 17 with metastasis of primary breast cancer to lymph nodes.

To examine the role of loss of heterozygosity (LOH) during tumor development and/or progression, we looked for correlations between metastasis of breast cancer to a regional lymph node(s) and LOH of chromosomal arms 11p, 13q, 16q, 17p, and 17q, where frequent losses in primary tumors have been detected. No correlation between lymph node metastasis and LOH of chromosomes 13q, 16q, or 17q was observed. However, tumors showing LOH of chromosomes 11p (chi 2 = 10.82, P less than 0.01) and 17p (chi 2 = 6.78, P less than 0.01) revealed a significantly higher incidence of metastasis to a regional lymph node(s) than tumors without LOH on these chromosomal arms. Furthermore, only four of 30 (13%) patients with tumors that retained both 11p and 17p had metastasis to a regional lymph node(s), compared with 24 of 32 (75%) patients with tumors that had lost both 11p and 17p. Analysis of LOH with markers on chromosomes 11p and 17p in a large number of tumors indicated that the peritelomeric region of each of these chromosomal arms contains a tumor suppressor gene that may be associated with tumor progression, particularly metastasis to a regional lymph node(s).     

Adrenal metastasis from carcinoma of the colon and rectum: A report of three cases

We report herein three cases of patients with adrenal metastases from colorectal carcinoma. Recurrent disease was suspected following markedly elevated levels of serum carcinoembryonic antigen (CEA), and adrenal metastases were confirmed by computed tomography (CT) scanning in all three patients. The adrenal metastasis was solitary in one patient and this patient is still alive and free from disease 1 year after undergoing complete removal of the adrenal metastasis. On the other hand, metastatic disease was not limited to the adrenal gland in the other two patients and both died of recurrent disease, 33 months and 4 months after undergoing removal of the adrenal metastases, respectively. Thus, although the prognosis of adrenal metastasis from colorectal cancer is usually poor, we believe that patients with a solitary adrenal metastasis will benefit from complete removal of the metastasis.     

Abnormal cellular property of fibroblasts from congenital gingival fibromatosis

Two strains of cultured cells were isolated and characterized from the gingiva of two siblings with congenital gingival fibromatosis. The growth rate of both fibroblast strains was slower than that of comparable cells obtained from the normal gingiva of control individuals. The amounts of substances, including collagen and glycosaminoglycans, biosynthesized by the diseased cells were much greater than those by the control cells from normal gingivae. Namely, 11.7-13.7% of the protein synthesized by diseased cells was collagen, whereas collagen accounted for only 6.1-8.5% of the total protein produced by normal cells. Moreover, the production of a large amount of extracellular substances by the diseased cells was confirmed by electron microscopic examination. These observations suggest that the fibromatosis tissues contain affected fibroblasts which have low growth activity but are active in the production of much greater amounts of collagen and other extracellular substances compared to normal fibroblasts.     

Immunohistochemical analysis of p53 and ras p21 expression in colorectal adenomas and early carcinomas

To further investigate whether multiple genetic changes are involved in the development of colorectal cancer, we performed an immunohistochemical analysis of p53 and ras p21 protein expression in 139 specimens of colorectal adenoma with varying degrees of dysplasia, 57 specimens of early cancer with an adenomatous component, and 12 specimens of superficial early cancer without any adenomatous component. Positive p53 staining was found in 15% of the adenomas with moderate dysplasia and in 42% of the adenomas with severe dysplasia or intramucosal carcinoma (IMCA). Positive immunostaining of p53 was observed to be significantly correlated with the degree of dysplasia and the depth of invasion, as was the expression of ras p21. However, a closer correlation was observed with the increasing size of the adenomas. Furthermore, p53 staining was positive in 42% of the 12 superficial early cancer specimens, while ras staining was positive in only 1 specimen (8%). These results indicate that p53 gene overexpression may play some biological role in both the adenoma-to-carcinoma sequence and in de novo cancer development, whereas ras p21 expression may not be as involved in de novo cancer development as in the malignant conversion of colorectal adenomas.     

Chemo-sensitivity of a human salivary adenocarcinoma cell line to several anti-cancer drugs and enhancement of the antitumor effects by combination with filipin or verapamil

A human salivary adenocarcinoma cell line, HSGc, was tested for the chemosensitivity and compared with a human squamous cell carcinoma cell line, KB. From IC50 values of anti-cancer drugs on the cells, it was found that HSGc was sensitive to CDDP, 5-FU and DTIC but resistant to ADM, MTX, VCR, PEP and MMC as compared to KB. The chemosensitivity of HSGc was in agreement with previously reported clinical data on the therapeutic results of salivary gland tumors. This suggests that HSGc may be an useful model for understanding the biological response of salivary adenocarcinoma cells to anti-cancer drugs. We further examined the combined effects of filipin and verapamil with these anti-cancer drugs. Filipin was found to enhance cell-killing effect of 5-FU and PEP on HSGc, while the combination of filipin with either DTIC or PEP was also effective on KB. Verapamil was effective in combination with 5-FU, VCR or PEP on HSGc and with DTIC, VCR or PEP on KB. Especially the most predominant enhancement on HSGc was observed in combination of filipin or verapamil with PEP. These findings suggest that even low-sensitive drug, PEP, is also useful when combined with either filipin or verapamil.