Calcium-binding Proteins in Human Carcinoma Cell Lines

Elevated levels of Ca2+-binding proteins are reported in transformed cells and thought to be involved in their uncontrolled proliferation and often increased motility. Therefore, three cell lines [LICR(Lond)-HN 1, -HN 2, and -HN 6] derived from human carcinomas displaying various degrees of locomotive activity were investigated for the presence of parvalbumin and related Ca2+-binding proteins. By applying different immunohistochemical methods in conjunction with a monospecific anti-parvalbumin antiserum, an intense staining was seen in cells displaying translocative motility. Often in these cells, an association with filamentous structures located in the nuclear region was observed. Unique Ca2+-binding proteins, absent from comparable normal tissue, were found in the malignant cell lines when analyzed by two-dimensional polyacrylamide gel electrophoresis and high-performance liquid chromatography. From these tumor cells a protein (Mr, 12,000; pI, 4.8) was isolated that crossreacted with antiparvalbumin antiserum. Peptide maps of this protein revealed a further structural homology to parvalbumin (Mr, 12,000; pI, 4.9). In analogy to muscle, where there is evidence for a regulatory role of parvalbumin in the contraction-relaxation cycle, we speculate that this protein is tumor-associated and connected to the motile behavior of carcinoma cells.