Established cell lines (e.g. HeLa, HEK293, etc) that are commercially available (e.g. through ATCC) does not require IRB approval for you to procure or to use. This is because it does not meet the definition of human subjects under IRB purview, and does not meet the scope of Singapore's Human Tissue Framework (HTF) as it has been substantially manipulated.
However, researchers are to note the following and take due caution where applicable.
1. Purchasing of primary cells (e.g. skin biopsies) can fall under the prohibition against trading of human tissues.
2. Creation of cell lines from tissues you had isolated from human subject comes under the scope of HTF.