HepaCAM and p-mTOR Closely Correlate in Bladder Transitional Cell Carcinoma and hepaCAM Expression Inhibits Proliferation via an AMPK/mTOR Dependent Pathway in Human Bladder Cancer Cells

Abstract

We explored the correlation between hepaCAM and activated p-mTOR in bladder transitional cell carcinoma. We also determined whether the antiproliferation effect of hepaCAM is associated with the AMPK/mTOR pathway. We performed quantitative reverse transcriptase-polymerase chain reaction to determine hepaCAM mRNA expression as well as Western blot to measure hepaCAM and p-mTOR protein levels in 25 men and 5 women. Disease was Ta-T1 in 7 patients, T2-T4 in 23, grade 1 in 13, grade 2 in 9, grade 3 in 8, primary in 13 and recurrent in 17. The WST-8 assay was used to study the effect of hepaCAM on cellular proliferation. p-AMPK, p-mTOR, total AMPK, total mTOR, c-Myc and cyclin D1 were also determined by Western blot. hepaCAM mRNA and protein levels were significantly decreased, while p-mTOR protein was remarkably increased in bladder transitional cell carcinoma compared to adjacent tissues (each p<0.01). Spearman correlation analysis revealed that the hepaCAM decrease was associated with an increase in p-mTOR (r=-0.533, p=0.002). Also, hepaCAM inhibited the proliferation of human bladder transitional cell carcinoma cells. hepaCAM over expression activated AMPK and down-regulated p-mTOR, and its targets c-Myc and cyclin D1. Treatment with the AMPK inhibitor compound C prevented the antiproliferation effect of hepaCAM. Compound C completely blocked hepaCAM induced activation of AMPK and down-regulation of p-mTOR and its targets c-Myc and cyclin D1. Results suggest an important correlation between hepaCAM and p-mTOR. hepaCAM can inhibit bladder cancer cell proliferation through an AMPK/mTOR dependent pathway.