Identification of myosin in human epithelial cancers with immunofluorescence

The location of myosin in neoplastic cells from human breast, colonic, gastric, bronchial, skin, esophageal, and renal carcinomas has been examined using an immunofluorescence technique with an antibody raised against human smooth muscle myosin. Normal tissues and fibroblast cell cultures were also investigated. In all the tumors myosin was located in the cytoplasm adjacent to the plasma membrane. Cancer cells appeared more strongly immunofluorescent than normal tissues. The precise pattern of immunofluorescence in neoplastic cells varied with the histologic type of the tumor. Linear immunofluorescence around the outer border of the cytoplasm was the most common pattern observed, but in well differentiated adenocarcinomas, myosin was located chiefly in relation to the microvillous border. In three of the squamous carcinomas a granular pattern of immunofluorescence was observed. Undifferentiated breast carcinomas did not contain more myosin than better differentiated tumors, and the intensity of immunofluorescence was no greater in invasive cancer cells than noninvasive tumor cells. The results suggest that myosin is present in greater amounts in neoplastic cells than normal cells and may be concerned with cell shape and polarity as well as cell movement.