Biological variation observed in baseline Top1 levels in xenograft models and patient samples.

<p>Abbreviations: PBMCs, peripheral blood mononuclear cells; SD, standard deviation.</p>a<p>. Xenograft data include Top1 levels measured in untreated and vehicle-treated (water) A375 and HCT 116 xenograft bearing mice and vehicle-treated (water) Colo829 and SK-MEL-28 mice from all experiments.</p>b<p>. Top1 levels measured in tumor biopsies from patients at baseline. Top1 levels expressed as an average of all measurements above the LLQ; each patient had Top1 levels above the LLQ for at least 2 of 3 protein loads.</p>c<p>. Top1 levels measured in PBMC samples from patients at baseline. Top1 levels expressed as an average of all measurements above the LLQ. In one patient, the Top1 levels were below the LLQ, in this case the LLQ was used as the Top1 measurement.</p

Validation of assay performance.

<p>(A) Top1 levels were measured in serial dilutions of three A375 and three HCT 116 xenograft extract samples using the Top1 immunoassay. (B) Total Top1 levels from the diluted extracts in panel A normalized to 1 μg/mL. (C) Comparison of Top1 levels in 24 matched samples and 6 control extracts, measured by two independent laboratories, the Pharmacodynamic Assay Development and Implementation Section (PADIS) laboratory and the National Clinical Target Validation Laboratory (NCTVL). Sample dilution and analysis were performed independently by both laboratories and Top1 levels were compared across sites.</p

Dose-dependent decrease in Top1 levels in A375 xenografts.

<p>Tumor biopsies were collected from A375 xenografts 2, 4, and 7 hours after a single dose of 0.033 to 1.0 MTD topotecan or water vehicle control (n = 4/cohort). Box plots represent interquartile range, 10^th and 90^th percentile whiskers, and median Top1 levels; diamonds represent group mean. Asterisks (*), treatment cohort mean was statistically different from vehicle mean at same time point, with a significance level of P≤0.05, as determined by Student's one-tailed <i>t</i>-test.</p

Top1 levels measured in xenografts treated with topotecan compared to two indenoisoquinoline topoisomerase inhibitors.

<p>(A) Top1 levels in A375 xenografts collected 4 or 7 hours following single dose treatment (MTD indicated) with topotecan or the indenoisoquinoline NSC 724998 (n = 5–6 mice/cohort). (B) HCT 116 xenografts and (C) Colo829 xenografts collected 4 hours after mice were treated with the indicated doses and drugs. (n = 3–6 mice/cohort; NSC 724998 had 2 mice/cohort). Box plots represent interquartile range, 10^th and 90^th percentile whiskers, and median Top1 levels; diamonds represent group mean. Dashed lines in panels B and C indicate the mean Top1 levels in a matched untreated cohort (0 h) for these xenograft models. Asterisks (*), treatment cohort mean was statistically different from vehicle mean at same time point, with a significance level of P≤0.05, as determined by Student's one-tailed <i>t</i>-test.</p

Inter-day and intra-assay performance of the Top1 immunoassay.

<p>Abbreviations: CV%, percent coefficient of variation; LLQ, lower limit of quantitation; SD, standard deviation.</p

Top1 levels in topotecan-responsive and -nonresponsive xenograft models.

<p>Mice treated with water vehicle or single dose 1.0 MTD topotecan for the designated times were assessed for Top1 levels using the validated immunoassay. (A) Mice bearing A375, topotecan-responsive xenografts were collected 2, 4, or 7 hours after treatment (n = 4/cohort). (B) HCT 116 colon cancer xenografts were collected 2, 5, and 24 hours after treatment and compared to baseline (0 h, no vehicle). n = 3–6 topotecan-treated mice/cohort and n = 12 in the 0 h cohort. (C) Colo829 xenografts were collected 4, 7, or 24 hours after treatment (n = 3/cohort). (D) SK-MEL-28 xenografts were collected 2, 5, or 24 hours after treatment (n = 6/cohort). Box plots represent interquartile range, 10^th and 90^th percentile whiskers, and median Top1 levels; diamonds represent group mean. Asterisks (*), treatment cohort mean was statistically different from the vehicle mean at same time point (or baseline in the HCT 116 cohorts), with a significance level of P≤0.05, as determined by Student's one-tailed <i>t</i>-test.</p