Bacillus Calmette-Guérin induces p21 expression in human transitional carcinoma cell lines via an immediate early, p53 independent pathway☆

Abstract 

Purpose

Work by our group has shown that bacillus Calmette-Guérin (BCG) induces cell cycle arrest at the G1/S interface in human transitional carcinoma cell lines. This study evaluated the effect of BCG on cell cycle regulatory proteins relevant to this effect.

Materials and Methods

The effect of BCG on selected cell cycle regulatory proteins, including cyclin D1, p27, and p21, was assessed in 2 human cell lines. After the identification of p21 as a candidate protein, p21 regulation was evaluated using a combination of Western, reverse transcriptase polymerase chain reaction, and promoter-reporter analysis. The immediate early versus delayed nature of p21 induction was determined. Finally, given the known potential for p21 to be regulated by both p53 dependent and independent pathways, the role of p53 in BCG induced expression of p21 was evaluated.

Results

BCG increased p21 expression 2-fold relative to controls as measured by Western, and promoter-reporter analysis. Inhibition of protein synthesis had no effect on p21 messenger ribonucleic acid induction in response to BCG. T24 cells contained a previously reported mutation in p53. In the p53 wild-type 253J cells, deletion of one or both p53 response elements in the p21 reporter had no effect on BCG induced reporter transactivation.

Conclusions

BCG up-regulates expression of p21 in human transitional cell carcinoma lines. The transactivation of p21 in response to BCG occurs through an immediate early, p53 independent pathway. The finding of increased p21, together with the observation that BCG induces cell cycle arrest at the G1/S interface, supports a role for this protein in the biologic response to BCG.

Keywords: Bladder cancer, Bacillus Calmette-Guérin, p21, α5 β1 integrin