The apoptosis linked gene-2 (ALG-2), discovered as a proapoptotic calcium binding protein, has recently been found upregulated in lung cancer tissue indicating that this protein may play a role in the pathology of cancer cells and/or may be a tumor marker. Using immunohistochemistry on tissue microarrays we analysed the expression of ALG-2 in 7371 tumor tissue samples of various origin as well as in 749 normal tissue samples. Most notably, ALG-2 was upregulated in mesenchymal tumors. No correlation was found between ALG-2 staining intensity and survival of patients with lung, breast or colon cancer. siRNA mediated ALG-2 downregulation led to a significant reduction in viability of HeLa cells indicating that ALG-2 may contribute to tumor development and expansion.