Enhancement of tumor suppressor RAR- protein expression by cationic liposomal-ATRA treatment in benzo(a)pyrene-induced lung cancer mice model

Targeting the specific molecular proteins or genes which are responsible for the suppression of cancer growth is currently an emerging molecular method to treat cancer. ATRA treatment is now considered as a molecular targeted therapy for many cancers. As ATRA exhibits its therapeutic effect through its receptors, this study was focused to investigate the effect and action of liposomal-ATRA treatment on the expression of RAR- protein which is also a tumor suppressor. The liposomal-ATRA was developed with cationic DOTAP and cholesterol by thin-film formation method. The benzo(a)pyrene(50mg/kg b.wt)-induced mice were treated with free and liposomal-ATRA(0.60mg/kg b.wt). The RAR- protein expression in lung and liver tissue samples were analyzed by immunohistochemistry (IHC) and western blotting (WB) on the 30th and 120th days. Almost nil expression of RAR- protein was observed in B(a)P cancer control and liposome alone-treated groups. A comparatively elevated expression was seen in the free ATRA-treated group (IHC score2+ in lung on the 120th day with band density of 14.46 +/- 1.24% in WB). Interestingly, the liposomal-ATRA treatment demonstrated a significantly (p0.01) higher RAR- expression in lung (35.20 +/- 3.398% band intensity and score 4+ in the 120th day) than that of in ATRA alone treatment. This study results indicate that the RAR- protein expression was suppressed by B(a)P during cancer induction even on the 30th day itself. The treatment could reactivate the suppression and the lipo-ATRA treatment could show significantly higher RAR- expression on the 120th day, which implies that it accumulated more ATRA in target site and sustained it for enhanced action.