Class II Tumor Suppressor Genes
Class II tumor suppressor genes encode proteins that function in the negative regulation of cell growth. The genes are downregulated in cancer without mutations or deletions in their coding regions. Downregulation is reversible indicating that gene and protein function can be reconstituted upon appropriate treatment.
The term “class II tumor suppressor gene” was invented in 1997 by Ruth Sager, who was the first to realize during the upcoming age of gene expression profiling that in human cancers many genes show reduced expression in tumors without being deleted or mutated. Accordingly, two classes of tumor suppressor genes were suggested: Class I tumor suppressor genes (tumor suppressor genes, TGS) that are lost in cancer due to mutation or deletion and class II tumor suppressor genes that are not altered at the DNA level but rather exhibit strongly reduced expression in tumors as compared with normal tissue.