ABSTRACT
BACKGROUND: The molecular drug all-trans retinoic acid (ATRA) acts on cancer cells via different molecular pathways, but its poor bioavailability in cancer cells limits its potency. This study was, therefore, carried out to analyse the oncogene expressions in the lung tissue of benzo[a]pyrene (B[a]P)-induced mice and compare between free ATRA and cationic liposome nanoformulation (lipo- ATRA) treatments. OBJECTIVE: This study was designed to analyse the changes in the expression levels of epidermal growth factor receptor (EGFR) and B-Raf in the lung tissues of B[a]P-induced mice during the cancer development stage itself and to find the suppressive effect of free ATRA and lipo-ATRA. METHODS: Lung cancer was induced in mice by oral ingestion of 50mg/kg body weight B[a]P weekly twice for four consecutive weeks. Then, the mice were treated with free and lipo-ATRA (0.60mg/kg) for 30 days via i.v injection. The EGFR and B-Raf gene expressions were analyzed in lung cells by reverse transcriptase polymerase chain reaction (RT-PCR) and quantitative polymerase chain reaction (qPCR). RESULTS: The RT-PCR gene band density and the relative quantity (RQ) values from qPCR revealed both EGFR and B-Raf genes to be significantly overexpressed in B[a]P control mice while having very low or no expression in normal mice. This indicates that they function as oncogenes in B[a]P-induced lung carcinogenesis. The lipo-ATRA treatment has shown a highly significant increase in RQ values for both EGFR and BRaf when compared to the free ATRA treatment. CONCLUSION: The study results have revealed the cationic lipo-ATRA treatment to have enhanced the bioavailability of ATRA in lung tissue due to its significant suppression action on EGFR-mediated oncogenes' expressions. Furthermore, the EGFR and BRaf could be the molecular targets of ATRA action in lung carcinogenesis.
ABSTRACT
This study aimed to find out the molecular therapeutic effect of lipo-ATRA on tumour suppressor TIG3 and cell proliferative biomarker PPARγ in B (a) P-induced lung cancer model. In RT-PCR study, ATRA- and lipo-ATRA-treated mice samples showed relatively higher TIG3 expression and decreased PPARγ expression (Band density) than cancer control. Among treatments, lipo-ATRA showed vital effect than free ATRA by enhancing TIG3 and decreasing PPARγ. The qPCR results also showed significant (p ≤ 0.05) difference in both TIG3 and PPAR (RQ values of TIG3, lipo-ATRA 23.85 ± 1.29; free ATRA 10.43 ± 1.81 and for PPARγ, lipo-ATRA 4.707 ± 1.21; free ATRA 15.78 ± 2.34). From this, we conclude that liposomal ATRA formulation is most preferable for prolonged delivery of ATRA at targeted site to favour molecular action. It implies that the therapeutic effect of lipo-ATRA in lung cancer was exhibited by ameliorating the TIG3 expression and by suppressing the expression of PPARγ.
