Chemoresistance in non-small-cell lung cancer: can multidrug resistance markers predict the response of xenograft lung cancer models to chemotherapy?

Objective: In chemotherapy for non-small-cell lung cancer (NSCLC), some patients seem to exhibit an intrinsic resistance or develop an acquired resistance under treatment. Results on resistance markers for possible treatment failure as shown in studies on selected lung cancer cell lines could not be completely confirmed in clinical trials. As these conflicting data require further research, we created a model between cell culture and the clinical need to study this problem.

Methods: Our study was based on patient-derived NSCLC xenografts in a mouse model, which revealed a high coincidence with the original tumour. Protein and messenger RNA (mRNA) expression of known resistance markers (breast cancer resistance protein (BCRP), multidrug resistance P-glycoprotein (MDR), lung cancer-related protein (LRP) and multidrug resistance protein 1 (MRP1)) were analysed by real-time polymerase chain reaction (PCR) and immunoblotting in 24 xenografts. Chemosensitivity to etoposide, carboplatin, gemcitabine, paclitaxel, cetuximab and erlotinib was determined in in vivo xenograft experiments and compared with the protein and mRNA expression of the multidrug resistance markers.

Results: With the exception of a single correlation between chemosensitivity and mRNA expression of etoposide and bcrp (mRNA expression of BCRP), we found no significant correlation between the response rates and protein- and mRNA expression levels in our 24 xenografts. The present results indicate that in vivo expression levels of multidrug resistance proteins and their mRNAs may not play a comparable role in chemoresistance of NSCLC, as pointed out in selected tumour cell lines.

Conclusions: Patient-derived xenografts allow detailed investigation of therapy-related markers and their dynamic regulation in a well-standardised and clinically related way. As a consequence of our investigations, we regard multidrug resistance to be a multifactorial phenomenon, in which more factors than the markers analysed by the present study may be involved.