Cytokine Induced Killer cells immunotherapy overcomes the resistance to MET tyrosine kinase inhibitors in nonsmall cell lung cancer

Purpose/Objective: Prognosis for late stage lung cancer under conventional therapies remains poor. We hereby investigated whether immunotherapy approach with CIK (Cytokine Induced Killer) cells might overcome acquired resistance to MET tyrosine kinase inhibitors(TKI) in NSCLC. CIK cells are a subset of ex -vivo expanded T lymphocytes with T-NK phenotype and MHC-unrestricted antitumor activity which is mediated by the interaction of CIK’s membrane receptor NKG2D with MIC A/B and ULBPs ligands expressed on the tumor cells. We hypothesized that acquired resistance and consequent acquisition of more aggressive characteristics of NSCLC cells might be associated with upregulation of MIC A/B and ULBPs ligands. Materials and methods: MET inhibitor resistant cells are generated by treating MET -addicted cells with increasing concentrations of the MET small-molecule inhibitors PHA-665752 OR JNJ38877605. CIKs were expanded from 10 healty donors, starting from PBMC, with the timed addition of IFN-gamma, Ab anti-CD3 and IL2. Cytotoxicity assays were preformed to detect antitumor activity of CIK cells. Results: The median expansion of CIK cells was 29-fold (range, 743). Expanded CIKs included a median of 39% CD3+ CD56+ cells (range, 2174). Median expression of NKG2D receptor was 87% (range, 6095). NSCLC cells sensitive to MET TKI (EBC 1 WT) had 51% membrane expression of MIC A/B. Such expression was upregulated on the cells that acquired resistance (EBC 1R125) reaching 100%. There was no difference observed in ULBPs ligands expression between both cell lines. CIK cells efficiently killed both, sensitive and resistant cell lines. Specific killing was significantly higher against resistant cells comparing to sensitive cells. An average specific killing of resistant line was 55%, 51%, 43% and 37% at 40:1, 20:1, 10:1 and 5:1 effector/target ratio respectively. The sensitive line had, at the same ratio, an average specific killing of 38%, 34%, 26%, 23%, respectively (n = 14). Conclusions: Our data describe for the first time the association of MIC A/B upregulation and MET TKI resistance in NSCLC. Acquired resistance is a common and limiting problem for chronic therapy with many TKI, including MET TKI. CIK cells adoptive immunotherapy might address this issue targeting MET TKI resistant tumor cells.