Characterization of human bladder cell membrane during cancer transformation

Abstract

Phenomena associated with changes in cell membranes are thought to play an important role in the cancer transformation. We hypothesized that the electrical charge of tumor cells can indirectly represent membrane-based changes that have occurred during cell transformation and may indicate tumor cell status. Here, we describe work showing that phospholipids, proteins content, and electric charge, are all altered in the cell membranes of pT2 stage/grade G3 bladder cancer. Qualitative and quantitative phospholipid composition and the presence of integral membrane proteins were identified using high-performance liquid chromatography. Protein composition was determined using selective hydrolysis of isolated bladder cell membrane proteins and peptide resolution. The surface charge density of human bladder cell membranes was determined using electrophoresis. Our results show that cancer transformation is associated with increased phospholipid levels and a decreased level of integral proteins. Moreover, the process of cancer transformation significantly enhanced changes in the surface charge density of the human bladder cell membrane. In conclusion, this study demonstrates that cell membrane structure and function are modified in bladder cancer cells and that further work in this area is warranted.

Fig. 1

A characteristic example of the separation of peptides from integral membrane proteins from bladder tissue (UV detected at 220 nm)

Fig. 2

The dependence of surface charge density on pH of non-neoplastic and bladder cancer cells from several patients

Fig. 3

The amounts of cell membrane phospholipids from human bladder tissue containing pT2-staged/G3-graded tissue. Statistically significant differences corresponded to P < 0.05. ^aIn comparison with control (non-neoplastic tissue)

Fig. 4

Content of integral membrane proteins isolated from human bladder tissue containing pT2-staged/G3-graded cancer. Statistically significant differences corresponded to P < 0.05. ^aIn comparison with control (non-neoplastic tissue)

Fig. 5

Content of peptides of hydrolyzed cell membranes isolated from human bladder tissue containing pT2-staged/G3-graded cancer. Statistically significant differences corresponded to P < 0.05. ^aIn comparison with control (non-neoplastic tissue)