1385P Analysis of Drug-Induced RNA Expression Changes in NSCLC Patient-Derived Explants As a Potential Tool for Personalized Therapy Choice

Tumor tissue has a complex structure, which includes different cellular and matrix components. Ex vivo tissue explants retain individual features of original neoplasms and may be used for personalized testing of the drug sensitivity. The existing morphological methods for evaluation of drug response in alive tissue sections are extraordinarily time-consuming and have poor interlaboratory reproducibility. We attempted to establish RNA-based expression assays, which may supplement or replace the existing pathology-based analyses. Fresh tumor tissues were obtained from patients with non-small cell lung cancer (NSCLC) undergoing surgery. Tumor 0.4-mm-thick slices were generated with a tissue chopper. NSCLC explants were cultured for 24 hours in a standard media containing either cisplatin (30 mkg/ml) or gefitinib (4 mkg/ml) or no drug (control). Samples from the same tumor sections were analyzed in parallel both with RNA-expression tests (PCR, RNAseq) and immunohistochemistry (IHC). 234 individual explants from 16 NSCLCs were obtained. The expression level of Ki-67 determined by PCR showed only limited correlation with percentage of Ki-67 positive cells identified by IHC (R2=0.27). MKI-67 (Ki-67 encoding gene) and TPX2 were chosen as proliferation markers for RNA expression tests. They showed nearly identical changes in expression upon drug exposure. As expected, EGFR-mutated tumors demonstrated more pronounced decline of expression of RNA proliferation markers in response to gefitinib as compared to EGFR wild-type NSCLCs. Interestingly, EGFR-mutated cancers appeared to be more sensitive to cisplatin as well. Selected tumor sets were further subjected to transcriptome RNAseq analysis. EGFR-mutated explants had significantly higher expression level of MAGEA3 than the wild-type samples. Furthermore, MAGEA3 expression in EGFR-mutated tumors was decreasing during incubation with gefitinib but not with cisplatin. Several genes were responsive to cisplatin exposure. HEXIM1, NXF1, POLG2 and CCL7 appeared to be the most promising markers of cisplatin sensitivity. RNA expression markers are promising reporters of individual tumor drug responsiveness.