Aurora Viaje

Skin tumor initiating ability of benzo(a)pyrene 4,5- 7,8- and 7,8-diol-9,10-epoxides and 7,8-diol

The skin tumor initiating abilities of both K-region and non-K-region epoxides of benzo(a)pyrene(BP) were determined in mice using a two-stage system of tumorigenesis. BP-4,5-epoxide and BP-7,8-dihydrodiol-9,10-epoxide (anti) were found to be weak tumor initiators whereas BP-7,8-epoxide had about a third of the activity as the parent hydrocarbon, BP. However, the 7,8-dihydrodiol of BP was found to be approximately as potent as BP suggesting that it may be a proximate carcinogen.

Fluocinolone acetonide: a potent inhibitor of mouse skin tumor promotion and epidermal DNA synthesis.

Abstract The relationship between the inhibition of mouse skin tumor promotion and the inhibition of epidermal DNA synthesis by the steroidal anti-inflammatory agent, fluocinolone acetonide (FA), was investigated. Simultaneous doses of either 10, 1, or 0.1 μg of FA and phorbol ester tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), resulted in an almost complete inhibition of promotion, whereas 0.01 and 0.001 μg of FA resulted in inhibition rates of 82% and 15%, respectively. Likewise, simultaneous doses of 10 or 1 μg of fluclorolone acetonide (FCA) and TPA caused a nearly complete inhibition of promotion, whereas 0.1 μg of FCA decreased promotion by 62%. In general, as the dose of both steroids was increased, an increase in the tumor latency period was observed. With the exception of the borderline effect of 0.001 μg of FA, the above doses of FA inhibited epidermal DNA synthesis by at least 60% for a 24-h period. Topical treatment with 10 μg of FA resulted in an almost complete inhibition of DNA synthesis for 6 days. The administration of 10 μg of FA 24 h after TPA treatment brought about a maximal inhibition of DNA synthesis of 65%, as compared with a 98% inhibition in control mice whose DNA synthesis had not been prestimulated. That is, FA was not quite as effective on S-phase cells as on G-1 cells. There appears to be a relationship between the inhibition of tumor promotion and epidermal DNA synthesis.

Improved conditions for murine epidermal cell culture

SummaryAn improved method for cultivating newborn mouse epidermal cells has been developed that increases the longevity, epithelial nature and efficiency of cell-line establishment. The use of Super Medium, an enriched Waymouths formulation, increased proliferation for long periods of time, as did incubation at 31°C rather than 37°C. The fetal bovine serum requirement was found to be reduced at the lower temperature. An increase in labeling indices was seen when epidermal growth factor (EGF) or the cyclic nucleotides were added and the presence of EGF receptors was determined. Of the prostaglandins (PG) examined, PGE1 and PGE2 produced the greatest increase in DNA synthesis. The PG precursors, arachidonic and 8,11,14-eicosatrienoic acid, were also greatly stimulatory. The use of a lethally irradiated 3T3 feeder layer at 31°C proved superior in maintenance of an epithelial morphology. Subculturable cell lines were established much more readily and reproducibly in carcinogen-treated cultures grown under the improved conditions.

Chapter 14 Explant Methods for Epidermal Cell Culture

Publisher Summary This chapter discusses the explant methods for epidermal cell culture. Full-thickness human skin is composed of epidermis, dermis, and subcutaneous tissue. Dermal components such as fibroblasts have been useful in studies on somatic cell genetics, cellular aging, and transformation. Keratinocytes are more pertinent because of the differentiation process they undergo and because the majority of human cancers arise from epithelial cells. The extent of drying of the explant on the dish prior to the addition of medium is critical, but is unfortunately a subjective measurement that varies from one skin to another. Sufficient drying is required for good adhesion to the dish, but further drying appears to affect the dermal part of the block and can effectively inhibit fibroblast outgrowth. Microscopic examination of human skin explants has shown that epithelial cells begin to grow out from the tissue block within several days after explanation. The use of a lethally irradiated 3T3 feeder layer may be considered under the category of growth factors, because the improved growth seen in many systems appears to be due to a labile factor given off by the 3T3 cells.