Cellular F-actin levels as a marker for cellular transformation: correlation with bladder cancer risk

Previous findings in cultured cells that differentiated cells had markedly higher F-actin levels than undifferentiated cells (Cancer Res., 50: 2215-2220, 1990) suggested that quantitative F-actin measurements in urinary cells might provide diagnostic or prognostic information by identifying those individuals with cells tending towards a lower degree of differentiation. The feasibility of such an approach was investigated using a risk stratification schema. Bladder wash samples were obtained from 163 symptomatic patients being evaluated for bladder cancer and 41 asymptomatic controls without hematuria or other symptoms consistent with bladder cancer. F-actin levels were evaluated by flow cytometry using a fluorescent phalloidin probe. The risk of bladder cancer was stratified according to biopsy, either DNA ploidy by flow cytometry or quantitative fluorescence image analysis cytology, previous bladder cancer history, and hematuria. A strong correlation between the presence of cells with abnormally low F-actin content in cells obtained by bladder wash from 38 patients and biopsy-proved bladder transitional cell carcinoma (P less than 0.001) was observed. A strong correlation was also observed between the presence of cells with low F-actin content and risk of bladder cancer assessed by either stratification schema (P less than 0.0001). The correlation was more consistent with the stratification by quantitative fluorescence image analysis cytology because of the 37% false-positive rate of ploidy analysis by flow cytometry among the control patients. Further evidence that low F-actin was correlated with cellular abnormality was obtained from simultaneously labeling cells for F-actin and with M344 antibody, a monoclonal antibody against a low-grade bladder tumor-related antigen. These studies showed that the F-actin content of the M344-positive cells was lower than that of the M344-negative cells. These results suggest that F-actin could be an early and sensitive marker for bladder cancer detection and risk prognostication.