The invention provides carbazole compounds, and prodrugs therefor, comprising a heterogroup coupled to an aryl group, wherein the heterogroup is selected from the group consisting of SO 2 , S=O, C=O, NH, and PO 3 . The aryl group may be substituted with one or more substituents selected from the group consisting of OH, NH 2 , NR 1 R 2 , NHR 1 , OCH 3 , OCHR 1 R 2 , OCH 2 R 1 , OCR 1 R 2 R 3 , C=O, or S=O, wherein R 1 , R 2 , and R 3 are alkyl groups, optionally wherein the heterogroup coupled to the aryl group is a dansyl group, and optionally wherein the heterogroup coupled to the aryl group is a fluorescent group. The compounds are useful for the treatment of cancers, especially those with decreased Ras-association domain family 1A (RASSF1A) expression, including prostate cancer. The compounds may reduce DNA methyltransferase activity and/or increase RASSF1A expression. Retention of the compound in a cell is diagnostic for decreased RASSF1A expression, and hence potentially for a cancer cell.
