Cancer research
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Comparative Study
Preclinical pharmacology of the natural product anticancer agent bryostatin 1, an activator of protein kinase C.
Bryostatin 1, a natural product anticancer agent isolated from a marine bryozoan, has been shown in tissue culture to activate protein kinase C. This agent has recently undergone Phase I testing in humans given either as a bolus i.v. injection or a continuous infusion. To understand how bryostatin 1 might be used best as an anticancer agent, a study of the pharmacokinetics, tissue distribution, metabolism, and elimination of bryostatin 1 in mice was undertaken, using [C26-3H]-labeled bryostatin 1. ⋯ The concentration in the gastrointestinal tract, along with the fecal excretion, suggests the possibility of enterohepatic circulation of this drug. In summary, this study demonstrates that bryostatin 1 is relatively stable in vivo, widely distributed but concentrated in some major tissues, and rapidly excreted first through urine and at later times through the feces. The data from this animal study should be useful in the design of future human trials with this anticancer drug.
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When carboplatin (cis-diammine-1,1-cyclobutane-dicarboxylato-platinum) delivery to brain tumors is optimized with osmotic blood-brain barrier disruption (BBBD), high frequency hearing loss can result. Treatment with sodium thiosulfate (STS) blocked carboplatin cytotoxicity against the LX-1 human small cell lung carcinoma cell line in vitro. ⋯ In a rat model of osmotic BBBD, STS was neurotoxic when given immediately after BBBD but not when given 60 min after BBBD, when the barrier is reestablished. Thus, delayed administration of STS may provide a mechanism to reduce the cochlear toxicity caused by BBBD-enhanced carboplatin delivery to the brain.
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Comparative Study
Association between cisplatin resistance and mutation of p53 gene and reduced bax expression in ovarian carcinoma cell systems.
P53 status may be a determinant of chemosensitivity of tumor cells; however, its involvement in cellular resistance to cisplatin remains uncertain. To investigate the relationships between p53 and the development of resistance to cisplatin, the p53 gene status was studied in ovarian carcinoma cell systems which included two cisplatin-resistant variants (IGROV-1/Pt 0.5 and IGROV-1/Pt 1) selected in vitro after prolonged drug exposure of the cisplatin-sensitive parental IGROV-1 cell line. IGROV-1/Pt 0.5 and IGROV-1/Pt 1 cell lines exhibited a degree of resistance of approximately 6 and 14, respectively, following 96-h exposure to the drug and were cross-resistant to other DNA-damaging agents (ionizing radiation and melphalan). ⋯ Northern blot analysis demonstrated a marked reduction in bax mRNA levels in IGROV-1/Pt 1 cisplatin-resistant cells. Cotransfection assays with wild-type or mutant p53 expression plasmids and a reporter gene plasmid that utilized the bax gene promoter to drive transcription of chloramphenicol acetyltransferase were consistent with the role of p53 in regulation of bax expression in these cells. Taken together, these observations support a role for mutations of the p53 gene in the development of cisplatin resistance in ovarian cancer as a consequence of loss of the ability of p53 to transactivate bax, an apoptosis-inducing gene.