SLC31A1 and lung cancer: 40 have determined the pattern of CTR1 protein expression in normal and malignant human tissues using standard immunohistochemical techniques. No CTR1 expression was found in several common types of cancer, although metastatic colon carcinoma showed the highest level of expression among the malignant tissues 40. More recently Kim et al. 41 could detect the expression of CTR1 by immunohistochemistry in several samples of nonsmall cell lung cancer and corresponding normal epithelium.