Powerful and versatile enhancer-promoter unit for mammalian expression vectors.

The enhancer and promoter of the immediate early gene of human cytomegalovirus (hCMV) were tested as a transcriptional control element by fusion to the cat gene, followed by measurement of its expression from plasmid DNA in the extrachromosomal and integrated state, respectively. Comparison of the hCMV enhancer-promoter to two other viral elements was performed in six commonly used cell lines of different tissue and species origin. Irrespective of the cell line and of the state of the DNA, the hCMV enhancer-promoter was considerably stronger than both the SV40 promoter and the long terminal repeat of Rous sarcoma virus.

Concurrent changes in growth-related biochemical parameters during regression of hormone-dependent rat mammary tumors.

The in vivo relationship was studied between these biochemical parameters which previous studies have separately implicated in the regression of hormone-dependent rat mammary tumors. Upon depletion of estrogen and suppression of prolactin levels by ovariectomy, there was a marked increase in the production of prostaglandin E2 (PGE2)(fourfold) and in the cyclic AMP (cAMP) content (twofold) in the regressing 7,12-dimethylbenz[a]anthracene-induced primary tumors. These two parameters appeared to be coupled since, in addition to this correlation, PGE2 stimulated adenylate cyclase and raised cAMP levels in both this primary tumor system and in another hormone-dependent transplantable rat mammary tumor (MTW9-A). Furthermore both the sensitivity of the adenylate cyclase system to PGE2 and the number of membrane binding sites for PGE2 increased upon induction of regression in these tumors. Under conditions where PGE2 and cAMP were elevated, (i.e., in regressing, but not growing, hormone-dependent mammary tumors), there was significant phosphorylation in the intact tissue of a 75,000-dalton nuclear protein, which appeared to be identical to the regression-associated protein shown by Cho-Chung and co-workers to undergo increased phosphorylation in response to elevated cAMP levels.

Caffeine and unsaturated fat diet significantly promotes DMBA-induced breast cancer in rats.

The following study was carried out to determine the possibility of caffeine being a promoter of breast cancer development in animals consuming vegetable fat. A controlled study, comparing the time of mammary tumor development and the number of tumors was carried out in Sprague-Dawley rats which had been given 20 mg of DMBA at seven weeks of age. This study evaluated the tumor promotional effects of caffeine alone, caffeine and unsaturated fat in combination, unsaturated fat alone, and a standard rat chow diet. The results show that the rats which consumed caffeine and unsaturated fat had the earliest development of tumor and the most multiple tumor occurrence. Average time to tumor development was 95 days. The fat or standard chow rats had an average time to tumor development of 134 and 140 days, respectively. The caffeine-alone rats had a mean time to tumor development of 188 days. The combination of an unsaturated fat diet and caffeine significantly shortened the time to tumor development when compared with the other three groups.

Hormone dependence of 7,12-dimethylbenz[a]anthracene-induced mammary tumor growth: correlation with prostaglandin E2 content.

Prostaglandin content in 7,12-dimethylbenz[a]anthracene-induced rat mammary tumors was correlated with growth responses to alterations in endogenous estrogen and prolactin. Prostaglandin E2 (PGE2) content varied inversely with tumor latency. Ovariectomy of tumor-bearing Sprague-Dawley rats resulted in regression of tumors in 90% of the castrated rats. PGE2 content in tumors from ovariectomized rats was elevated twofold (P less than 0.05) compared to PGE2 content in tumors from intact controls. Haloperidol treatment promoted tumor growth even after ovariectomy and returned tumor PGE2 values to control levels. Tumors grouped by growth status irrespective of hormone status showed an inverse relationship between PGE2 content and growth response.

Biochemical subgrouping of benign breast disease to define premalignant potential.

To determine which subgroups of benign breast disease are likely to progress to malignant degeneration, a biochemical analysis of 3'5' cyclic adenosine monophosphate (cAMP) was run on several samples of breast tissue. cAMP is elevated in a progressive fashion from normal breast tissue to fibrosis, cystic mastitis, ductular hyperplasias, and finally to carcinoma. Correlation of cAMP levels in breast lesions with histopathologic grading of increasing epithelial proliferation confirmed the concept that there are subgroups within those lesions that have greater malignant potential. Benign breast lesions with significantly higher cAMP levels, although still lower than those of cancer, must be considered at higher risk for eventual malignant change.

Caffeine, cyclic nucleotides, and breast disease.

Methylxanthine consumption is associated with the development of fibrocystic disease of the breast. Methylxanthine abstention is associated with resolution of signs and symptoms of fibrocystic disease. Abstinence from methylxanthine consumption decreased breast biopsies and the need for major breast surgery because of benign disease. Methylxanthine consumption is associated with elevated cyclic adenosine monophosphate (AMP) and cyclic guanosine monophosphate (GMP) values in fibrocystic dsiease over those obtained in normal breast tissue.