Parallel Acquired Resistance Heterogeneity: Novel Patient Derived Synchronous Cell Pair with Distinct Mutations in an ALK-Translocated Lung Adenocarcinoma

Background Molecularly targeted therapies provide prolonged clinical response rates in lung adenocarcinomas with druggable oncogenic driver driven. However, most tumors relapse due to a wide variety of resistance mechanisms. The emergence and intratumoral heterogeneity of these mechanisms are not fully understood. Accordingly, we established tumor cell lines from various metastatic sites in the pleural space.
Materials and methods A pair of novel ALK-translocated lung adenocarcinoma cell lines were established from the malignant pleural effusion (PF240-PE) and pleural carcinosis specimen (PF240-PC) of a 38-year-old female patient following ALK inhibitor treatment. Mutational analyses and immunohistochemistry were performed in treatment naïve and in post-crizotinib samples and in the patient derived tumor cell lines. Cell viability following different generations ALK inhibitor treatment alone and in combination with SAHA, a pan-HDAC inhibitor, was tested by SRB assays.
Results Two distinct mutations, namely the previously known L1152R and a so far functionally not characterized E1161K were identified in the tissue specimens. Strikingly, the carcinosis derived PF240-PC harbored E1161K and effusion derived PF240-PE carried L1152R mutation. In vitro drug sensitivity testing showed resistance of both lines to crizotinib but sensitivity against entrectinib, a novel generation ALK inhibitor. Importantly, PF240-PE combination treatment of crizotinib with the histone deacetylase inhibitor SAHA resulted in strong synergism.
Conclusion This is the first report of the successful synchronous establishment of patient-derived ALK translocated cell lines harboring two distinct resistant mutations providing evidence for the parallel emergence of multiple resistance mechanisms in a single patient. Furthermore, our results suggest that combinatory HDAC inhibition can enhance sensitivity of resistant mutation carrying ALK-translocated lung adenocarcinoma cells to ALK inhibition. Altogether our findings underline the importance of liquid and tissue based multiple site rebiopsies in order to efficiently combat acquired resistance during targeted treatment in future personalized precision medicine approaches.