QR-32 is a regressive murine
fibrosarcoma cell clone which cannot grow when they are transplanted in mice; QRsP-11 is a progressive malignant
tumor cell clone derived from QR-32 which shows strong tumorigenicity. A recent study showed there to be differentially expressed up-regulated and down-regulated
proteins in these cells, which were identified by proteomic differential display analyses by using two-dimensional gel electrophoresis and mass spectrometry.
Cofilins are small
proteins of less than 20 kDa. Their function is the regulation of actin assembly. Cofilin-1 is a small ubiquitous
protein, and regulates actin dynamics by means of binding to actin filaments. Cofilin-1 plays roles in cell migration, proliferation and phagocytosis.
Cofilin-2 is also a small
protein, but it is mainly expressed in skeletal and cardiac muscles. There are many reports showing the positive correlation between the level of cofilin-1 and
cancer progression. We have also reported an increased expression of cofilin-1 in
pancreatic cancer tissues compared to adjacent paired normal tissues. On the other hand,
cofilin-2 was significantly less expressed in
pancreatic cancer tissues. Therefore, the present study investigated the comparison of the levels of cofilin-1 and
cofilin-2 in regressive QR-32 and progressive QRsP-11cells by western blotting.
Cofilin-2 was significantly up-regulated in QRsP-11 compared to QR-32 cells (p<0.001). On the other hand, the difference of the intensities of the bands of cofilin-1 (18 kDa) in QR-32 and QRsP-11 was not significant. However, bands of 27 kDa showed a quite different intensity between QR-32 and QRsP-11, with much higher intensities in QRsP-11 compared to QR-32 (p<0.001). These results suggested that the 27-kDa
protein recognized by the antibody against cofilin-1 is a possible
biomarker for progressive
tumor cells.