The effect of methanol leaf extract of Chromolaena odorata (MLECO) on Human Colorectal Adenocarcinoma Cell lines HT-29 (ATCC® HTB-38â„¢) proliferation was investigated using the Cell Titer 96 MTT Proliferation Assay where the viable cells were seeded at a density of 5 × 104 (100 𝜇L/well). Varying log concentrations of extract (100-700 𝜇g/mL) were added and incubated for 24, 48, and 72 h time points. Incubation of the extract in the presence of VEGF and ET-1 was also conducted at different times. 

MTT assay showed that after 72 hours, the extract caused marked inhibitory effects on the cancer cell lines with lower concentration showing greater effect. When the plant extract was incubated alone with cancer cell lines at 200 and 800 𝜇g/mL, the results showed that the latter concentrations was more potent at cell inhibition but when incubated with VEGF and ET-1, the 200 𝜇g/mL +ET-1 was more potent at 24 hours. 

The result showed that the methanol leaf extract of Chromolaena odorata alone caused marked inhibition of HT29 cell lines after 72 hours but in the presence of the mitogens (VEGF and ET-1), the effect on the cell line was that of proliferation showing that the mitogens interfered with the plant extract’s ability to cause inhibition of cell line.