Purification of a protein associated with human bronchogenic squamous-cell carcinoma

A heteroantiserum raised in rabbits to extracts of human squamous-cell carcinoma of the lung which exhibited marked tumour specificity was used to monitor the fractionation and isolation of a tumour-associated component of the extract. KC1 extracts of pools of both normal lung and bronchogenic squamous-cell carcinoma were subjected to a series of purification steps involving acid precipitation, salting out, DEAE chromatography and preparative polyacrylamide-gel electrophoresis. At each stage, fractions were tested for their ability to react in the complement-fixation assay with the antiserum. A protein was ultimately isolated which did not appear to be present at detectable levels in an equivalent fraction of normal lung extract, reacted with the heteroantiserum, and appeared to be present in all extracts of squamous-cell carcinoma.