Abstract 4910: Modeling immunotherapy in ex vivo organ culture of non-small cell lung cancer (NSCLC)

PD1-PDL1 interaction is one mechanism of tumor evasion of the immune system, and inhibitors of this interaction can allow cancer cell killing by cytotoxic T cells. In NSCLC as well as in most other cancers, the clinical benefit from such inhibitors is far from universal; around 20% of tumors respond to this treatment. Response of tumors to anti-cancer agents depends on interactions of epithelial tumor cells and the microenvironment, including stromal cells such as fibroblasts, immune cells and extracellular matrix. Studying cell signaling and drug-sensitivity of cancer should take into consideration the different compartments of an individual tumor. Regarding immunotherapy, manipulating regulators of PDL1 expression might augment the activity of these drugs, or possibly be active as an immunotherapy on its own. Specifically, little is known about the impact of chemotherapy, radiotherapy or targeted agents on the expression and activity of the PD1-PDL1 signaling in human cancer. Combining such treatments with immunotherapy is a potentially promising approach that is currently investigated clinically. However, the number of potential combinations is vast, and no valid and convenient experimental model exists to test candidate treatments and combinations. Experimental procedures: Ex vivo organ cultures (EVOC) were directly established from fresh NSCLC tissues, as a model that recapitulates real tumor and its microenvironment, including immune cells. Tissue elements were mechanistically dispersed to cell clumps (30-100 cells per clump), or cut to one cubic mm pieces and placed in culture. LDH release was used as a surrogate of cell death. Samples were analyzed by formalin fixation and paraffin embedment, sectioning and hematoxilin and eosin visualization of cells. PDL1 mRNA and protein levels were measured by RT-PCR and western blots. Results: Cell viability of NSCLC EVOC is maintained over a time window of at least 4-7 days. Cytotoxic drugs evoke cell death. PDL1 mRNA and protein levels are elevated in NSCLC EVOC in response to inflammation signals as Interferon gamma. Glucocorticoid steroidal drugs causes reduction in PDL1 mRNA and protein in NSCLC EVOC. Cisplatin treatment causes elevation in PDL1 protein. Variability in basal and induced PDL1 protein levels was detected in response to inflammation signals in EVOCs generated from different patients. Conclusions: Our results indicate the feasibility of EVOC for NSCLC and the potential to use it as a model to