Login to Access Video or Poster Abstract: MP48-13
Sources of Funding: None

Introduction

Recent preclinical evidence has indicated the involvement of androgen receptor (AR) signals in bladder cancer outgrowth as well as chemosensitivity. Meanwhile, we have demonstrated that AR signals modulate the expression and activity of FOXO1, a transcriptional factor known to induce apoptosis through the PI3K-Akt pathway, in bladder cancer cells. In this study, we investigated the role of FOXO1 in bladder cancer progression as well as resistance to cisplatin treatment.

Methods

We assessed the effects of FOXO1 inhibition via short hairpin RNA (shRNA) virus infection or inhibitor (AS1842856) treatment on bladder cancer cell proliferation (by MTT assay in the presence or absence of cisplatin), migration (by scratch wound healing assay), and invasion (by transwell invasion assay), apoptosis (by TUNEL assay), and the expression of their related molecules (by RT-PCR). We also immunohistochemically stained for phospho-FOXO1 (p-FOXO1), an inactive form of FOXO1, in tissue microarrays consisting of muscle-invasive bladder cancer specimens from patients who received at least 3 cycles of cisplatin + gemcitabine neoadjuvant chemotherapy prior to radical cystectomy.

Results

FOXO1 silencing via its shRNA in AR-positive bladder cancer lines, UMUC3 and 647V-AR, resulted in significant increases in cell viability, migration, and invasion, and the expression of MMP-2/VEGF, as well as significant decreases in apoptosis and the expression of cyclin-dependent kinase inhibitors p21/p27. In addition, FOXO1 knockdown cells were significantly more resistant to cisplatin treatment at its pharmacological concentrations, compared with control cells. In these control FOXO1-positive lines, AS1842856 treatment also significantly reduced cisplatin sensitivity. Immunohistochemistry in transurethral resection specimens further showed p-FOXO1 positivity in 25 (58%) of 43 cases, including 7 (41%) of 17 responders to chemotherapy versus 18 (69%) of 26 non-responders (P=0.068).

Conclusions

FOXO1, as a tumor suppressor, appears to play an important role in bladder cancer progression and correlates with cisplatin sensitivity. Accordingly, FOXO1 stimulation, with or without AR inactivation, has the potential of being a therapeutic approach for bladder cancer and may also be useful for overcoming chemoresistance.

Funding

None