Assessing tumor heterogeneity and FLOT/FOLFOX-induced alterations in cancer stem cells and cancer immune checkpoint molecules using patient-derived tumor organoids

BackgroundGastric cancer is a deadly disease with poor prognosis and unfavorable therapeutic outcomes. It is known that a major cause of treatment failure for gastric cancer is related to tumor heterogeneity. However, it is difficult to assess heterogeneity, as the composition of tumors is dynamic and cancer treatments reshape cell diversity and gene/protein expression profiles.ObjectiveWe utilized gastric cancer patient-derived tumor organoids to monitor tumor heterogeneity and the impacts of chemotherapy (FLOT and FOLFOX) on cancer stem cells (LGR5 and CD133) and cancer immune checkpoint molecules (MHC-I and PD-L1).MethodsSix tumor organoids were established from different patients or different regions of the same tumor. The tumor organoids were used to investigate the real-time profiles of cancer stem cell marker expression and cancer immune checkpoint molecule expression after chemotherapy treatment. Tumor suppression was monitored by the propidium iodide assay and measurements of tumor organoid diameter. Expression levels of cancer stem cell markers and immune checkpoint molecules were analyzed by flow cytometry.ResultsGrowth of all tumor organoids could be suppressed by chemotherapy. However, diverse impacts of FLOT and FOLFOX were observed in terms of the expression profiles of cancer stem cell markers and cancer immune checkpoint molecules. In particular, tumor organoids from different patients exhibited distinct expression profiles for cancer stem cell markers and immune checkpoint molecules after treatment with the same chemotherapeutic regimen. Similar observations were made with tumor organoids derived the same patient but different tumor regions.ConclusionOur findings demonstrated that spatial and temporal tumoral heterogeneity can be observed after treatment with chemotherapy, suggesting that repeated monitoring of tumor characteristics may be essential for clinical decision making. In addition, sampling of multiple sites at multiple time-points might be important when evaluating the impacts of chemotherapy on cancer stem cells markers and immune checkpoint molecules.