Efficacy of EGFR Inhibitors and NSAIDs Against Basal Bladder Cancers in a Rat Model: Daily vs. Weekly Dosing, Combining EGFR Inhibitors with Naproxen, and Effects on RNA Expression.

Background: There are few effective treatments specifically aimed at basal bladder cancer.

Objective: Female F344 rats administered N-butyl-N-(4-hydroxybutyl)-nitrosamine (OH-BBN) develop large invasive bladder cancers. We determined the efficacy of daily vs weekly dosing of EGFR inhibitors, determined the efficacy of naproxen combined with an EGFR inhibitor, and performed RNA analysis of bladder tumors treated for 5 days with EGFR inhibitors or NO-naproxen to identify pharmacodynamic biomarkers.

Methods: Erlotinib (6 mg/Kg BW daily or 21 or 42 mg/Kg BW weekly), lapatinib (25 or 75 mg/Kg BW daily or 263 or 525 mg/Kg BW weekly) and/or naproxen (30 mg/Kg BW daily) were administered to OH-BBN-treated rats beginning 2-12 weeks post OH-BBN. Rats were sacrificed 28 weeks after the final OH-BBN treatment to determine the effects of the EGFR inhibitors + naproxen on bladder weights and tumor development. In a separate study, rats were treated with OH-BBN. When palpable tumors developed, rats were treated with erlotinib, lapatinib, gefitinib, or the NSAID NO-naproxen for 5 days. RNA analysis was performed on the tumors.

Results: Daily or weekly dosing of erlotinib or lapatinib and daily dosing of naproxen reduced large tumor formation up to 70%, while combining daily lapatinib and naproxen reduced tumors 100%. RNA Analysis: All EGFR inhibitors strongly reduced cell proliferation and chromosome replication pathways, while NO-naproxen altered the G protein receptor, oxygen homeostasis and immune function pathways.

Conclusions: While daily and weekly dosing with EGFR inhibitors and naproxen were effective, combining lapatinib and naproxen yielded no tumors. This might encourage its clinical use in an adjuvant setting with superficial basal tumors, and perhaps even in a more advanced setting. Furthermore, RNA analysis identified specific pathways that might be potential pharmacodynamic biomarkers in clinical trials.