Dear all,

I am currently investigating LPS-induced cell death. To determine the IC50 value, I seeded a cancer cell line and treated it with various concentrations of LPS as outlined in the literature. However, even at the highest concentration tested, I consistently observed approximately 90% cell viability, despite varying the incubation times across multiple attempts. Most recently, I replicated an experiment exactly as described in another study, yet the results remained unchanged. All other components, including the cell line and MTS assay, were verified to be functioning correctly. Based on these findings, I suspect that the LPS used in our study may be sub-optimal or unsuitable for this experimental setup (for using cell culture).

May you help me what is the problem?

LPS : L2630 Lipopolysaccharides from Escherichia coli O111:B4

Last MTS Raw datas (with A549 cells):

100 ng/mL LPS --- 0,4400 0,4313 ---- cell viability --- 86%

500 ng/mL LPS --- 0,4620 0,4278 ---- 89%

1000 ng/mL LPS --- 0,4422 0,4354 ---- 87%

1500 ng/mL LPS ---- 0,4042 0, 3993 --- 73%

Expectation cell viabilities:

100 ng/mL LPS --- cell viability --- ~ 80%

500 ng/mL LPS --- ~ 55%

1000 ng/mL LPS --- ~ 40%

1500 ng/mL LPS ---- ~ 30%