Abstract: The present invention provides methods for diagnosing cancer (such as ovarian, breast, or colon cancer) or a predisposition thereto in a subject, for monitoring the efficacy of treatment of a subject suffering from cancer, or for determining the likelihood of survival of a subject suffering from cancer, comprising detecting modified chromatin (such as DNA methylation) within a locus of the LOC134466 gene in a sample taken from the subject. The invention further provides kits for use in these methods, and methods of treating subjects based on a diagnosis performed using the methods of the invention.