Effect of cell density on intracellular adriamycin concentration and cytotoxicity in exponential and plateau phase EMT6 cells.

The relationship between cell number and available Adriamycin (ADM) has been investigated in EMT6 cells. Results have shown that the ratio between cell number and total available ADM is important in determining in vitro ADM uptake and surviving fraction. Having established this effect, the sensitivity of exponentially growing and plateau phase EMT6 cells to ADM was investigated. ADM was assayed by extraction followed by spectrofluorimetry and also by flow cytometry (FCM); both methods were found to give the same ratio of intracellular ADM between exponentially growing and plateau phase cells. We found that for a given exposure dose plateau phase cells were more sensitive than exponentially growing cells. For the same dose per cell, plateau cells take up more ADM than exponentially growing cells. But for a given intracellular ADM concentration exponentially growing cells have a lower surviving fraction than plateau phase cells. We conclude that the surviving fraction is dependent on the proliferative state of the cells and in order to draw that conclusion it is important to relate the ADM effect on cells in vitro to the total ADM available to each cell

An Investigation of the Ability of Antipsoriatic Drugs to Inhibit Calmodulin Activity: A Possible Mode of Action of Dithranol (Anthralin)

Epidermal calmodulin (CaM) has been reported to be elevated in psoriasis and to decrease following clearance of psoriasis with treatment. We set out to investigate whether any of the principle drugs used in the treatment of psoriasis had inherent CaM antagonist activity. Utilizing a CaM-activated phosphodiesterase we have demonstrated that even at very high concentrations, the systemic drugs etretinate, methotrexate, and 8-methoxypsoralen, and the topical agents hydrocortisone and crude coal tar showed minimal CaM inhibitory activity. Dithranol (anthralin), however, whether freshly prepared or oxidized, produced substantial inhibition of CaM activity and was demonstrated to be a potent competitive antagonist of CaM, suggesting another possible therapeutic mode of action of dithranol in psoriasis

Expression of Insulinlike Growth Factor (IGF) and IGF-Binding Protein Genes in Human Lung Tumor Cell Lines

Background: The presence of multiple, low-molecular-weight, insulinlike growth factor (IGF)-binding proteins in lung tumor cell-conditioned medium and lung cancer patient serum has been recently reported. Purpose: To begin to elucidate the genetic basis for these observations, the present study examines the expression by lung tumor cell lines of three IGF-binding protein genes, namely, IGFBP-1, IGFBP-2, and IGFBP-3. Since IGF-binding proteins are thought to modulate the biologic action of the IGFs, the relationship between the expression of IGF-binding protein genes and the genes encoding IGF-I and IGF-II also has been investigated. Methods: Gene expression was studied in four small-cell lung cancer (SCLC) and three non—small-cell lung cancer (NSCLC) cell lines using Northern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR) for IGFBP-1. Results: IGFBP-1 gene expression was detected by Northern blot analysis in one NSCLC cell line only. However, RT-PCR revealed that the IGFBP-1 gene was expressed in all four SCLC cell lines and in two of the three NSCLC lines. Northern blot analysis of IGFBP-2 gene expression demonstrated that all lung tumor cell lines expressed this gene. A low level of IGFBP-3 gene expression was detected in one SCLC cell line and in all three NSCLC cell lines. All lung tumor cell lines expressed the IGF-II gene as determined by Northern blot analysis. In marked contrast, none of the lines showed evidence of IGF-I gene expression using this method. However, RT-PCR revealed a low level of IGF-I gene expression in one SCLC and one NSCLC cell line only. Conclusions: These observations indicate 1) that IGF-binding proteins secreted by lung tumors are encoded by at least three different genes; 2) that there may be a close association between IGF-II and IGFBP-2 gene expression, such that, where there is production of IGF-II, IGFBP-2 is the principal BP; and 3) that the IGF-II gene is more widely expressed than the IGF-I gene in human lung tumor cell lines. [J Natl Cancer Institute 84: 628-634, 1992