Effect of 13cRA on cell proliferation by SRB assay. SY5Y and NB69 cells were plated on 96 well plates and treated with or without 10Â ÎźM retinoic acid. Plates were harvested after 2, 5, and 7Â days of 13cRA treatment. Cell viability was analyzed by an SRB assay measuring optical density (OD). Cell lines treated with 13cRA showed lower OD, indicating reduced cell number compared to untreated control cells. (DOC 46 kb