BACE, or beta-secretase, is an attractive target in the treatment of Alzheimer's Disease because of its involvement in the generation of amyloid beta peptides. BACE is a type I transmembrane aspartyl protease composed of pre-, pro-, catalytic, transmembrane and cytoplasmic domains. For the present study, the coding sequence was truncated just before the transmembrane domain and the resulting construct was extended with the C-terminal addition of a (His)(6) and expressed in several mammalian host cells. The enzyme expressed in CHO cells had the best crystallographic behavior and was purified in large quantities in a three step procedure. The purified BACE was comprised of two forms, namely the full length proBACE construct beginning with Thr(1), and a derivative missing the first 24 amino acids beginning with E(25). These BACE precursors co-crystallized in the presence of inhibitors yielding structures to 3.2 A resolution. HIV-1 protease treatment of this mixture resulted in complete cleavage of the F(39)-V(40) bond, leaving the V(40)EM...ES(432) (His)(6) derivative that was purified yielding an enzyme that was no more active than untreated BACE but co-crystallized with inhibitors producing well shaped, bipyramidal co-crystals diffracting to 2.6 A resolution.

Ellagic acid, a plant phenolic compound present in certain foods eaten by humans, has been reported to possess antimutagenic and anticarcinogenic properties. To evaluate the potential anticarcinogenic effect of ellagic acid in humans, we investigated the effect of nontoxic concentrations of ellagic acid on the metabolism of benzo(alpha)pyrene and binding of benzo(alpha)pyrene metabolites to DNA in cultured explants of human bronchus and in human bronchial epithelial cell cultures. Ellagic acid at concentrations of 10, 25, or 50 microM did not significantly alter the metabolism of benzo(alpha)pyrene in the bronchial explant cultures and in only one of four bronchial cell cultures. However, binding of metabolites of benzo(alpha)pyrene to DNA was inhibited in all explant and cell cultures of human bronchus by 26 to 77%. These results support the work of other investigators and suggest that ellagic acid may be an inhibitor of polycyclic aromatic hydrocarbon-induced carcinogenesis in humans.

The role of calcium in modulating cellular replication and differentiation has been described for various cell types. In the present study, the effects of Ca++ on the growth and differentiation of cultured rat esophageal epithelial cells was investigated.Epithelial cells were isolated from esophagi taken from 8 week-old male CDF rats by the enzymatic dissociation method of Kaighn. The cells were cultured in PFMR-4 medium supplemented with 0.25 mg/ml dialyzed fetal bovine serum, 5 ng/ml epidermal growth factor, 10-6 M hydrocortisone 10-6 M phosphoethanolamine, 10-6 M ethanolamine, 5 pg/ml insulin, 5 ng/ml transferrin, 10 ng/ml cholera toxin and 50 ng/ml garamycin at 36.5°C in a humidified atmosphere of 3% CO2 in air. At weekly intervals, the cells were subcultured with a solution containing 1% polyvinylpyrrolidone, 0.01% EGTA, and 0.05% trypsin. After various passages, the replication rate of the cells in PFMR-4 medium containing from 10-6 M to 10-3 M Ca++ was determined using a clonal growth assay.

Using an explant/cell culture system, rat esophageal epithelial cells were transformed in vitro by exposure to N-nitroso-N-benzyl-N-methylamine (BMNA). Twelve esophageal explant cultures per group were exposed twice (at days 1 and 7) to 0.0, 2.5, 5.0 or 10.0 micrograms BMNA/ml of medium. After incubation for 60-90 days, epithelial cells in primary cultures treated with all three concentrations of BMNA could be subcultured and cell lines were developed. The number of primary cultures and the number of subsequently developed epithelial cell lines was carcinogen-dose-dependent. Cell lines could only be established from carcinogen treated explants. Electron microscopy revealed that the BMNA-treated cell lines contained morphological markers of esophageal epithelial cells; i.e., numerous tonofilaments and junctional complexes, even after prolonged subculture. By immunofluorescence, the cells reacted positively with antibodies prepared to mouse skin prekeratins (K1 and K2). Two cell lines (from the 5 micrograms BMNA/ml group) were able to grow in soft agar and produce palpable tumors upon injection into syngeneic recipients. These tumors possessed the histological features of squamous cell carcinomas.

Although detailed cytogenetic analysis has been carried out in many types of cancer, there is little information on the chromosomal makeup of prostatic cancer cells. Karyological analyses of cell lines derived from both metastatic and primary prostatic carcinoma have been carried out by Q-, C-, and sequential banding techniques. The metastatic line, PC-3, isolated from a bone marrow specimen, is an established epithelial line which is tumorigenic in nude, athymic mice and forms colonies in semisolid agar suspension. A subline, PC-3/M, was isolated from a PC-3-induced mouse tumor. Karyotypic analysis of PC-3 by Q- and C-banding showed the cells to be aneuploid at all culture passage levels. The modal chromosome number shifted from 62 to 55 between the 5th and 50th passages. PC-3 has a unique karyotype. Chromosomes 2, 3, 5, 15, and Y were always absent. At least 11 different marker chromosomes were observed. The subline, PC-3/M, had a similar karyotype and retained the parental PC-3 markers. PC-3/M had a more restricted chromosomal frequency distribution range. Nearly 73% of the PC-3/M cells examined had 60 or 61 chromosomes in contrast to the wide distribution seen in PC-3. Silver staining for nucleolus organizer regions indicated that the number of functional nucleolus organizer regions in PC-3 was proportional to the number of acrocentric chromosomes. Banding analysis of PC-5-PI isolated from primary prostatic adenocarcinoma indicated that this line also had a characteristic karyotype with 28% pseudodiploid and 72% pseudotetraploid components. All metaphases examined were partially trisomic in chromosome 9 and lacked a demonstrable Y chromosome.

Epithelial cell cultures of the normal human prostate gland were established. The subculturing of these cultures was accomplished with a novel nonenzymatic technique. These cultures were defined as normal epithelial cells on the basis of ultrastructure, karyotype, and inability to grow in soft agar.

The objective of this study was to isolate, characterize, and preserve normal prostatic epithelial and carcinoma cell lines. To date, four specimens have been acquired from patients with benign prostatic hypertrophy. Culture attempts have been successful, yielding a total of 32 cell lines. Three of these lines have been examined thus far and were found to have clearly demonstrable tartrate-inhibitable acid phosphatase granules by histochemical techniques. Several problem areas emerge from these preliminary studies. These involve the difficulty of (a) characterization of the cells as originating from prostatic epithelium, (b) identification of prostatic carcinoma cells, and (c) possible senescence in culture of cell lines.