In vitro activation of cyclophosphamide for an in vitro chemosensitivity assay

Abstract

The problem of activation of cyclophosphamide (CY) for an in vitro chemosensitivity assay was studied using the B16 melanoma. The efficacy of the S9 hepatic microsomal fraction in vitro was compared with activation by passage of drug in vivo. The effect of CY was assayed by inhibition of tritiated thymidine (3HdThd) uptake by B16 tumor cells in vitro, and by its effect in single dose in vivo on the life span of syngeneic C57BL/6 mice injected with B16 tumor cells. In vivo activation of CY that was achieved by injecting 20 mg of CY intraperitoneally (i.p.) into mice and obtaining plasma 20 minutes later was more rapid and more reproducible, while in vitro activation provided a more potent preparation and a better quantitative correlation with the in vivo effect of CY. The activation activity of different preparations of S9 microsomal fractions was found to be directly related to the activity of aminopyrine demethylase, a mixed function oxidase enzyme, in the S9 fraction, rather than to total protein concentration. The S9-activated drug required 2 1/2 to 3 hours to achieve maximum inhibition of subsequent tumor cell tritiated thymidine (3HdThd) incorporation compared with 20 minutes to achieve maximum inhibition by in vivo activated drug. We conclude that rapid qualitative screening for effectiveness of CY may best be done with in vivo activated drug, whereas quantitative prediction of effective concentration appears to be best achieved with drug activated in vitro by the hepatic S9 fraction.

Evaluation of mutagenicity and metabolism-mediated cytotoxicity of the naphthoquinone 5-methoxy-3,4-dehydroxanthomegnin from Paepalanthus latipes

“…In this study, we investigated in vitro metabolism-mediated cytotoxicity of 5-methoxy-3,4-dehydroxanthomegnin using the S9 system. For comparison, we evaluated cyclophosphamide, an indirect-acting cytotoxicant employed in antineoplastic therapy, as the control of biotransformation induction by the hepatic S9 fraction (Hill and Hill, 1984). …”

Umbilical Hernia Repair in Patients with Cirrhosis and in Patients with Severe Comorbidities—A Nationwide Cohort Study

“…In a systematic review and meta‐analysis, the proportion of emergency umbilical hernia repair in patients with cirrhosis was found to be 43% in a total of 3,229 patients with cirrhosis [16]. Furthermore, in some studies, the mortality rate was 15%, and the morbidity rate was at least 80% following emergency umbilical hernia repair in patients with cirrhosis, respectively [17–20]. According to the latest guidelines published by European Hernia Society (EHS) in 2019, elective umbilical hernia repair should be offered to patients with cirrhosis and with a MELD‐score above 15 preceded by preoperative optimization of liver function.…”

A new zebrafish model for experimental leukemia therapy

“…The survival activation of a drug. 26 In particular, the effectiveness of CY, which is converted into an active metabolite by enzymatic systems in liver, 27 against ZL1 leukemia in vivo demonstrates the maturity of these systems in 10-13 d old larvae. In addition, the transplantable tumor model in syngeneic (i.e., nonimmunosuppressed) animals enables accurate assessment of broad host organism responses to a tumor such as an immune response 28 and angiogenesis.…”