Summary Persistent activation of Stat3 is oncogenic and is prevalent in a wide variety of human cancers. Chronic cytokine stimulation is associated with Stat3 activation in some tumors, implicating cytokine receptor-associated Jak family kinases. Using Jak2 inhibitors, we demonstrate a central role of Jaks in modulating basal and cytokine-induced Stat3 activation in human solid tumor cell lines. Inhibition of Jak2 activity is associated with abrogation of Stat3 nuclear translocation and tumorigenesis. The Jak2 inhibitor, AZD1480, suppresses the growth of human solid tumor xenografts harboring persistent Stat3 activity. We demonstrate the essential role of Stat3 downstream of Jaks by inhibition of tumor growth using shRNA targeting Stat3. Our data support a key role of Jak kinase activity in Stat3-dependent tumorigenesis.

Key Points AZD1208 is a selective pan-Pim kinase inhibitor with efficacy in AML cells, xenografts, and Flt3-internal tandem duplication or Flt3 wild-type patient samples. AML cell growth inhibition is associated with suppression of p70S6K, 4EBP1 phosphorylation, and messenger RNA translation.

Purpose: To determine the tumor tissue/cell distribution, functional associations, and clinical significance of PD-1, LAG-3, and TIM-3 protein expression in human non-small cell lung cancer (NSCLC). Experimental Design: Using multiplexed quantitative immunofluorescence, we performed localized measurements of CD3, PD-1, LAG-3, and TIM-3 protein in >800 clinically annotated NSCLCs from three independent cohorts represented in tissue microarrays. Associations between the marker's expression and major genomic alterations were studied in The Cancer Genome Atlas NSCLC dataset. Using mass cytometry (CyTOF) analysis of leukocytes collected from 20 resected NSCLCs, we determined the levels, coexpression, and functional profile of PD-1, LAG-3, and TIM-3 expressing immune cells. Finally, we measured the markers in baseline samples from 90 patients with advanced NSCLC treated with PD-1 axis blockers and known response to treatment. Results: PD-1, LAG-3, and TIM-3 were detected in tumorinfiltrating lymphocytes (TIL) from 55%, 41.5%, and 25.3% of NSCLC cases, respectively. These markers showed a prominent association with each other and limited association with major clinicopathologic variables and survival in patients not receiving immunotherapy. Expression of the markers was lower in EGFR-mutated adenocarcinomas and displayed limited association with tumor mutational burden. In single-cell CyTOF analysis, PD-1 and LAG-3 were predominantly localized on T-cell subsets/NKT cells, whereas TIM-3 expression was higher in NK cells and macrophages. Coexpression of PD-1, LAG-3, and TIM-3 was associated with prominent T-cell activation (CD69/CD137), effector function (Granzyme-B), and proliferation (Ki-67), but also with elevated levels of proapoptotic markers (FAS/BIM). LAG-3 and TIM-3 were present in TIL subsets lacking PD-1 expression and showed a distinct functional profile. In baseline samples from 90 patients with advanced NSCLC treated with PD-1 axis blockers, elevated LAG-3 was significantly associated with shorter progressionfree survival. Conclusions: PD-1, LAG-3, and TIM-3 have distinct tissue/ cell distribution, functional implications, and genomic correlates in human NSCLC. Expression of these immune inhibitory receptors in TILs is associated with prominent activation, but also with a proapoptotic T-cell phenotype. Elevated LAG-3 expression is associated with insensitivity to PD-1 axis blockade, suggesting independence of these immune evasion pathways.

Triple-negative breast cancers (TNBCs) have poor prognosis and lack targeted therapies. Interrogation of genomic datasets identified increased PIM1 copy number-driven expression in TNBC. RNA interference in breast cancer and non-malignant mammary epithelial cell models revealed a PIM1 dependency in TNBC cells for proliferation and apoptotic protection, absent in non-malignant cells. PIM1 knockdown reduced BCL2 expression, and dynamic BH3 profiling analysis revealed that PIM1 prevents mitochondrial-mediated apoptosis in TNBC cell lines. PIM1 expression associates with several MYC-transcriptional signatures and promotes cell population growth through regulation of c-MYC and transcription of MYC-targets, including MCL1. The pan-PIM kinase inhibitor AZD1208 inhibited growth and sensitized TNBC cell lines, xenografts and patient-derived xenografts to standard of care chemotherapy. We identify PIM1 as a malignant cell-selective target in TNBC, illustrating relationships with MYC activation, regulation of anti-apoptotic BCL2 and MCL1, established TNBC oncogenic proteins SHP2 and EPHA2 and cell cycle inhibitor p27. Finally we identify a potential use of PIM1 inhibitors to abrogate TNBC's high threshold to TNBC standard of care chemotherapy induced apoptotic cell death.

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