Carcinogenesis is a long process that results in the accumulation of genetic alterations primarily in genes involved in the regulation of signalling pathways relevant for the regulation of cell growth and the cell cycle. Alteration of additional genes regulating cell adhesion and migration, angiogenesis, apoptosis, and drug resistance confers to the cancer cells a more malignant phenotype. Genes that participate in the regulation of some critical metabolic pathways are also altered during this process. Choline kinase (ChoK) has been reported to belong to the latter family of cancer-related genes. Recently, we have reported that increased activity of ChoK is observed in human breast carcinomas. Here, we provide further evidence that ChoK dysregulation is a frequent event found in a variety of human tumors such as lung, colorectal, and prostate tumors. Furthermore, a large panel of human tumor-derived cell lines also show increased ChoK activity when compared to appropriate non-tumorigenic or primary cells. These findings strongly support the role of ChoK alterations in the carcinogenic process in human tumors, suggesting that ChoK could be used as a tumor marker. (C) 2002 Elsevier Science (USA). All rights reserved.