AXL activation can promote resistance to MEK inhibition in a model of colorectal cancer (CRC)

Background

In metastatic colorectal cancer (mCRC) the presence of intrinsic and the development of acquired resistance to target therapy represent the most unsolved problems in the treatment of patients. The RAS/RAF/MEK/MAPK signalling pathway plays central roles in the intracellular transduction of proliferative signals from activated cell membrane growth factor receptors to the nucleus in cancer cells. MEK activation is an important convergence point involved in the development of drug resistance in mCRC setting. AXL, a tyrosine kinase receptor, plays important roles for cancer progression, invasion, metastasis and drug resistance. We did this preclinical study to evaluate a possible mechanism of MEK acquired resistance.

Methods

CRC (HCT116 and LOVO) cell lines were used. We generated in vitro HCT116 and LOVO cell lines resistant to the MEK inhibitor refametinib. Expression and activation of intracellular pathway were analysed by Western Blot (WB). The effect of foretinib, R428 and S49076 (AXL inhibitors) were evaluated by MTT assay. Cell cycle and apoptosis were analysed by flow cytometry. Chambers of transwell were used to evaluate the migratory capacity.

Results

We generated, HCT116 and LOVO clones (MEK-R) resistant to refametinib after continuous one-year drug exposure. MEK-R CRC cells have an IC₅₀ value 50 and 100 times higher than parental cells, respectively. We found in the resistant clones a strong activation of pAXL and its downstream pathway (in particular pAKT). Treatment of resistant clones with the different concentrations of AXL inhibitors was able to reduce cell viability accompanied by a marked deregulation of activation of AXL, AKT and MAPK. Further experiments on cell cycle, apoptosis and migration are still ongoing and will be presented.

Conclusions

Our in vitro preliminary data demonstrate AXL activation as a potential mechanism of resistance to MEK inhibition, and suggest a treatment with AXL inhibitors as a clinical strategy to possibly prevent this mechanism of resistance in CRC.

Clinical trial identification

Legal entity responsible for the study

Second University of Naples

Funding

AIRC

Disclosure

All authors have declared no conflicts of interest.