Biochemical assays of proteins extracted from cytocentrifuge preparations and cryostat tissue sections. (A) Western blotting. Anti-ALK (ALKc) identifies the 80-kD NPM-ALK protein present in lysates of SU-DHL-1 cells. This protein is also detected by anti-NPM (NA24). In contrast, anti-ALK detects a protein of 85 kD in lysates from case #789 and a protein of 97 kD in lysates from case #862 but only wild-type 38-kD NPM are present in these cases. Normal tonsil contains no ALK protein and only wild-type NPM. (B) In vitro kinase assay. Kinase activity is present in the 80-kD NPM-ALK protein present in the SU-DHL-1 cell line, in an 85-kD ALK protein present in case #789, and in a 97-kD ALK protein present in case #862. No corresponding band is detected in the tonsil used as negative control.