Plasma membrane retrieval in neoplastic pancreatic acinar cells

The dynamics of plasma membrane retrieval has been studied in the pancreatic acinar carcinoma in order to determine if neoplastic cells exhibiting a heterogeneity of cytodifferentiation stages retain the capacity to interiorize and recycle plasma membrane. To this end, the plasma membranes of neoplastic pancreatic acinar cells were labeled with radioiodinated cationic ferritin (¹²⁵I-CF), and the fate of the tracer was monitored by quantitative electron microscopic autoraidography. The undifferentiated granule-deficient cells of the tumor internalized membrane-bound ¹²⁵I-CF and sequestered it predominantly in lysosomes. By contrast, the differentiated granule-rich cells internalized significantly more membrane-bound ¹²⁵I-CF, and the tracer was localized in secretory granules and in lysosomes. The data suggest that neoplastic cells retain the capability of retrieving plasma membrane and that the dyanamics of the process is correlated with the state of cytodifferentiation of the neoplastic cells.