A tumor suppressor gene, or anti-oncogene, is a gene that protects a cell from one step on the path to cancer. When this gene is mutated to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes. This book presents topical research data in the study of tumor suppressors, including Rab GTPases as potential tumor suppressors; the regulation of neutrophil function by tumor suppressor PTEN; the role of BRIT1/MCPH1 in genome maintenance and tumor suppression; epigenetic silencing of tumor suppressors; and the relationship between Micro RNA and tumor suppressors.