Characterizing actin puncta as the invadopodia in two cancer cell lines. Cancer cell line MTC and MDA-MB-231 had a number of punctate actin structures. These actin puncta were identified as invadopodia, as they were well colocalized with cortactin, as shown by immunostaining. In addition, in MDA-MB-231 cells, punctate F-actin structures are well colocalized with invadopodia marker TKS5.