The slow cell death response when screening chemotherapeutic agents

Abstract

Purpose To examine the correlation between cell death and a common surrogate of death used in screening assays, we compared cell death responses to those obtained with the sulforhodamine B (SRB) cell protein–based “cytotoxicity” assay. Method With the SRB assay, the Hill equation was used to obtain an IC50 and final cell mass, or cell mass present at infinite agent concentrations, with eight adherent cell lines and four agents (32 agent/cell combinations). Cells were treated with high agent concentrations (well above the SRB IC50) and the death response determined as the time-dependent decrease in cells failing to bind both annexin V and vital fluorochromes by flow cytometry. Results Death kinetics were categorized as fast (5/32) (similar to the reference nonadherent Jurkat line), slow (17/32), or none (10/32), despite positive responses in the SRB assay in all cases. With slow cell death, a single exposure to a chemotherapeutic agent caused a slow, progressive increase in dead (necrotic) and dying (apoptotic) cells for at least 72 h. Conclusions Cell death (defined by annexin and/or fluorochrome binding) did not correlate with the standard SRB “cytotoxicity” assay. With the slow cell death response, a single exposure to an agent caused a slow conversion from vital to apoptotic and necrotic cells over at least 72 h (the longest time point examined). Here, increasing the time of exposure to agent concentrations modestly above the SRB IC50 provides a method of maximizing cell kill. If tumors respond similarly, sustained low doses of chemotherapeutic agents, rather than a log-kill, maximum tolerated dose strategy may be an optimal strategy of maximizing tumor cell death.

3-Propionyl-thiazolidine-4-carboxylic acid ethyl esters: a family of antiproliferative thiazolidines

“…5,6,[10][11][12][13] The obtained cytotoxicity was compared to the activity of ALC67, camptothecin and 5-uorouracil, two marketed anticancer agents frequently used as positive controls in cytotoxicity assays. [17][18][19][20][21] All obtained IC 50 values were similar to ALC67's values (Table 1): the bioactivity of the terminal alkyne molecule remained when the phenyl moiety was replaced either by aliphatic or aromatic groups suggesting that this position is not essential for the molecule to be cytotoxic. Hence, a novel class of antiproliferative thiazolidines was developed.…”

A comparative analysis of in vitro toxicity of diesel exhaust particles from combustion of 1st- and 2nd-generation biodiesel fuels in relation to their physicochemical properties—the FuelHealth project

“…This assay is widely described as a “cytotoxicity assay” (Vichai and Kirtikara 2006 ). However, the observed decrease in cell protein concentration may result not only from cell death but also from a combination of alterations in cell biochemistry and anti-proliferative effects (Blois et al 2011 ). Our results showed that 48-h treatment with each of the three DEP samples decreased cellular protein content significantly (~40%) at the highest dose.…”

PEG- b -PLA micelles and PLGA- b -PEG- b -PLGA sol–gels for drug delivery

“…While most studies suggest that drug release tends to be rapid for PEG- b -PLA micelles, there is strong evidence for long-circulating PEG- b -PLA micelles, and promising tactics to slow drug release for PEG- b -PLA micelles for drug targeting by the EPR effect have emerged [39–42]. …”

“…Both options are available for cancer treatment: In the former case, PEG- b -PLA micelles with relatively low molecular weight PEG and PLA blocks might be sufficient for drug solubilization and for a log-kill, MTD strategy [42]. On the other hand, prodrug strategies involving PEG- b -PLA micelles with relatively high molecular weight PEG and PLA blocks and prodrugs may be considered for anticancer agents that may benefit from increasing the time of exposure as a method to maximize tumor cell killing.…”