Amino acid residue penultimate to the amino-terminal gly residue strongly affects two cotranslational protein modifications, N-myristoylation and N-acetylation.

To examine the amino-terminal sequence requirements for cotranslational protein N-myristoylation, a series of site-directed mutagenesis of N-terminal region were performed using tumor necrosis factor as a nonmyristoylated model protein. Subsequently, the susceptibility of these mutants to protein N-myristoylation was evaluated by metabolic labeling in an in vitro translation system or in transfected cells. It was found that the amino acid residue at position 3 in an N-myristoylation consensus motif, Met-Gly-X-X-X-Ser-X-X-X, strongly affected the susceptibility of the protein to two different cotranslational protein modifications, N-myristoylation and N-acetylation; 10 amino acids (Ala, Ser, Cys, Thr, Val, Asn, Leu, Ile, Gln, and His) with a radius of gyration smaller than 1.80 A directed N-myristoylation, two negatively charged residues (Asp and Glu) directed N-acetylation, and two amino acids (Gly and Met) directed heterogeneous modification with both N-myristoylation and N-acetylation. The amino acid requirements at this position for the two modifications were dramatically changed when Ser at position 6 in the consensus motif was replaced with Ala. Thus, the amino acid residue penultimate to the N-terminal Gly residue strongly affected two cotranslational protein modifications, N-myristoylation and N-acetylation, and the amino acid requirements at this position for these two modifications were significantly affected by downstream residues.

[Weekly hepatic arterial infusion of high dose 5-fluorouracil for liver metastasis from colorectal cancer].

A weekly infusion of high dose 5-fluorouracil by way of the hepatic artery has been performed in 23 cases with synchronous metastasis from colorectal cancer since 1993. The prognosis in these cases was compared with 94 cases treated without infusion chemotherapy in 94 cases before 1992. The overall one-year and three-year survival rate was 64.8% and 30.2%, respectively, in cases with infusion chemotherapy. The one-year and three-year survival rate was 42.8% and 18.6%, respectively, in cases without infusion chemotherapy. Overall survival rate was significantly different between cases with and without infusion chemotherapy (p < 0.05). In conclusion, weekly infusion chemotherapy resulted in a better survival rate than without infusion chemotherapy.

Steroid sulfatase expression is an independent predictor of recurrence in human breast cancer.

Steroid sulfatase (STS) hydrolyzes several sulfated steroids such as estrone sulfate, dehydroepiandrosterone sulfate, and cholesterol sulfate. In the present study, we have measured STS mRNA levels in 97 breast cancers by reverse transcription-PCR using a fluorescent primer in the presence of an internal standard RNA and evaluated its association with disease-free and overall survival. The median value was 728.0 amol/ng RNA (range, 0-11,778 amol/ng RNA). Levels were significantly higher in tumors demonstrating lymph node metastasis than in those without nodal involvement (P = 0.033) and in patients who experienced a recurrence during the follow-up period (mean, 40.8 months; median, 39 months) compared with those with no evidence of further disease (mean, 49.2 months; median, 48 months; P = 0.029). No significant associations were found between STS mRNA expression and age, menopausal status, tumor size, histological grade, estrogen receptor status, or postoperative adjuvant therapy. High levels of STS mRNA proved to be a significant predictor of reduced relapse-free survival as a continuous variable (log STS mRNA; P = 0.028). As a dichotomous variable with an optimized cutoff point of 1,240 amol/ng RNA, expression was also associated with a significantly shorter relapse-free survival rate (P = 0.002), but no significant correlation was found between the STS mRNA level and overall survival. Expression was found to be an independent factor for predicting relapse-free survival on multivariate analysis. The results thus support a putative role of STS in breast cancer growth and metastasis.

Molecular and epidemiological analyses of abnormal expression of aromatase in breast cancer.

One-third of human breast cancers exhibit estrogen-dependent proliferation. It appears that estrogen functions as a mitogenic factor in these carcinomas. As aromatase is the rate-limiting enzyme in estrogen biosynthesis. It could play an important role in the pathogenesis of estrogen-dependent breast cancer. The aromatase gene consists of at least six exons 1, each containing a promoter, and the tissue-specific expression is regulated by alternative use of these multiple promoters. The expression of aromatase in the breast and abdominal adipose tissues is regulated by a promoter flanking exon 1b. Molecular and epidemiological analyses of tissue-specific utilization of multiple exons 1 and promoters revealed a switching from use of the adipose-specific exon 1b to exon 1c in adipose tissues adjacent to the carcinomas in most breast cancer patients. Exon 1c has been shown to be specific for the ovary. Aromatase mRNA in adipose tissues distal to the tumour of the same patients was normally transcribed from exon 1b as was breast tissue in healthy controls. It is noteworthy that a switching from exon 1b to exon 1c was often observed in breast cancer patients having metastatic lymph nodes. These data suggest that switching from an adipose-specific exon 1b to exon 1c could cause a deviation from strict regulation of tissue-specific expression of the adipose aromatase leading to over-expression of the adipose aromatase. Consequently overproduction of local estrogen may promote carcinogenesis or proliferation of breast cancer cells.