Methods are provided for detecting a cell proliferative disorder associated with TSLC1 by contacting a proliferating cell of a subject suspected of having the disorder with a reagent that detects TSLC1 and detecting the level of TSLC1 in the proliferating cell. TSLC1 is a single gene whose expression is reduced or absent in A549 and some other NSCLC, hepatocellular carcinoma and pancreatic cancer cell lines. It has further been discovered that TSLC1 expression or suppression is perfectly correlated with promoter methylation state. Restoration of TSLC1 expression to normal or higher levels is sufficient by itself to suppress tumor formation. The invention further provides methods of treating such disorders by contacting cells of a patient suffering from the disorder with a therapeutically effective amount of a reagent that modulates TSLC1 level in the proliferating cells.