Panoply™ Human NTRK1 Over-expressing Stable Cell Line

For solid tumors, including lung cancer, the application of cancer immunotherapy has improved clinical outcomes for a small number of patients. However, most patients show little or no response to immune checkpoint inhibitors used as monotherapy, or develop resistance during treatment. Therefore, identifying resistance mechanisms and new combination therapies is crucial for improving the efficacy of immune checkpoint inhibitors. Here, researchers conducted an in vivo shRNA screening experiment focusing on genes encoding FDA-approved drug targets (FDAome). They implanted epithelial and mesenchymal Kras/p53 (KP) mutant mouse lung cancer cells expressing an FDAome shRNA library into syngeneic mice treated with anti-PD-1 antibodies. Sequencing of barcoded shRNAs revealed a significant decrease in Ntrk1 expression in mesenchymal tumors treated with PD-1 blockade, suggesting that Ntrk1 provides a survival advantage to tumor cells under immune system pressure. These data confirm that Ntrk1 transcription levels are upregulated in tumors treated with PD-1 inhibitors. Furthermore, analysis of tumor-infiltrating T cell populations indicated that Ntrk1 can promote CD8+ T cell exhaustion. Finally, the study found that Ntrk1 promotes the expression of PD-L1 on tumor cells by regulating the Jak/Stat signaling pathway. Therefore, these data suggest that Ntrk1 activates the Jak/Stat signaling pathway, regulating the expression of immunosuppressive molecules, including PD-L1, thereby promoting immune exhaustion in the tumor microenvironment.

Since Ntrk1 was initially identified through an FDA-approved hairpin RNA screen and considered essential for tumor cell survival under immune pressure induced by PD-1 blockade, researchers aimed to determine whether Ntrk1 regulates the tumor immune microenvironment. To address this, researchers subcutaneously implanted Ntrk1-overexpressing cells and control cells into 129/sv wild-type mice to examine their effects on the immune microenvironment. Overexpression of Ntrk1 significantly increased tumor size in vivo (Figure 1A), consistent with in vitro growth data. Flow cytometry analysis of four-week-old tumors revealed that Ntrk1 overexpression was associated with a significant decrease in total T cell infiltration within the primary tumor, likely due to a significant reduction in total CD8+ T cells, while there was no significant effect on CD4+ T cells (Figure 1B-D). Furthermore, Ntrk1 overexpression also affected the function of CD8+ T cells, with a nearly threefold increase in PD-1+ CD8+ T cells in tumors expressing Ntrk1 (Figure 1E, F). These cells also co-expressed Tim3, indicating that this subset of CD8+ T cells was in an exhausted state. In vitro co-culture experiments also confirmed that Ntrk1 overexpression reduced the proliferative capacity of immune cells, while Ntrk1 deficiency promoted immune cell proliferation.

Figure 1. Ntrk1 modulates tumor growth as well as CD8+ T cell exhaustion and activity in vivo. (Konen J M, et al., 2019)