Mesothelin Secretion by Pancreatic Cancer Cells Co-opts Macrophages and Promotes Metastasis.

Pancreatic ductal adenocarcinoma (PDAC) is a highly metastatic disease, yet effective treatments to inhibit PDAC metastasis are lacking. The rich PDAC tumor microenvironment plays a major role in disease progression. Macrophages are the most abundant immune cell population in PDAC tumors and can acquire a range of functions that either hinder or promote tumor growth and metastasis. Here, we identified that mesothelin secretion by pancreatic cancer cells co-opts macrophages to support tumor growth and metastasis of cancer cells to the lungs, liver, and lymph nodes. Mechanistically, secretion of high levels of mesothelin by metastatic cancer cells induced the expression of VEGF alpha (VEGFA) and S100A9 in macrophages. Macrophage-derived VEGFA fed back to cancer cells to support tumor growth, and S100A9 increased neutrophil lung infiltration and formation of neutrophil extracellular traps. These results reveal a role for mesothelin in regulating macrophage functions and interaction with neutrophils to support PDAC metastasis. SIGNIFICANCE: Mesothelin secretion by cancer cells supports pancreatic cancer metastasis by inducing macrophage secretion of VEGFA and S100A9 to support cancer cell proliferation and survival, recruit neutrophils, and stimulate neutrophil extracellular trap formation. See related commentary by Alewine, p. 513.

Inhibition of insulin-like growth factors increases production of CXCL9/10 by macrophages and fibroblasts and facilitates CD8+ cytotoxic T cell recruitment to pancreatic tumours.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with an urgent unmet clinical need for new therapies. Using a combination of in vitro assays and in vivo preclinical models we demonstrate that therapeutic inhibition of the IGF signalling axis promotes the accumulation of CD8+ cytotoxic T cells within the tumour microenvironment of PDAC tumours. Mechanistically, we show that IGF blockade promotes macrophage and fibroblast production of the chemokines CXCL9 and CXCL10 to facilitate CD8+ T cell recruitment and trafficking towards the PDAC tumour. Exploring this pathway further, we show that IGF inhibition leads to increased STAT1 transcriptional activity, correlating with a downregulation of the AKT/STAT3 signalling axis, in turn promoting Cxcl9 and Cxcl10 gene transcription. Using patient derived tumour explants, we also demonstrate that our findings translate into the human setting. PDAC tumours are frequently described as "immunologically cold", therefore bolstering CD8+ T cell recruitment to PDAC tumours through IGF inhibition may serve to improve the efficacy of immune checkpoint inhibitors which rely on the presence of CD8+ T cells in tumours.

Overcoming osimertinib resistance with AKT inhibition in EGFRm-driven Non-Small-Cell-Lung-Cancer with PIK3CA/PTEN alterations.

PURPOSE: Osimertinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) indicated for the treatment of EGFR mutated (EGFRm)-driven lung adenocarcinomas. Osimertinib significantly improves progression-free survival in first-line treated patients with EGFRm advanced NSCLC. Despite the durable disease control, the majority of patients receiving osimertinib eventually develop disease progression. EXPERIMENTAL DESIGN: ctDNA profiling analysis on-progression plasma samples from patients treated with osimertinib in both first (Phase 3, FLAURA trial) and second-line trials (Phase 3, AURA3 trial) revealed a high prevalence of PIK3CA/AKT/PTEN alterations. In vitro and in vivo evidence using CRISPR engineered NSCLC cell lines and PXD models support a functional role for PIK3CA and PTEN mutations in the development of osimertinib resistance. RESULTS: These alterations are functionally relevant as EGFRm NSCLC cells with engineered PIK3CA/AKT/PTEN alterations develop resistance to osimertinib and can be re-sensitized by treatment with the combination of osimertinib and the AKT inhibitor capivasertib. Moreover, xenograft and PDX in vivo models with PIK3CA/AKT/PTEN alterations display limited sensitivity to osimertinib relative to models without alteration, and in these double mutant models capivasertib and osimertinib combination elicits an improved anti-tumor effect versus osimertinib alone. CONCLUSIONS: Together, this approach offers a potential treatment strategy for patients with EGFRm-driven NSCLC that have a sub-optimal response, or develop resistance, to osimertinib through PIK3CA/AKT/PTEN alterations.