Colorectal cancer liver metastases (CRCLM) that present with a replacement histopathological growth pattern (HGP) are resistant to neoadjuvant anti‐angiogenic therapy. Surrogate biomarkers are not available to preoperatively identify patients with these tumors. Here we identify differentially expressed genes between CRCLM with a replacement HGP and those with a desmoplastic HGP using RNA sequencing. We demonstrate that LOXL4 is transcriptionally upregulated in replacement HGP CRCLM compared with desmoplastic HGP CRCLM and the adjacent normal liver. Interestingly, lysyl oxidase‐like 4 (LOXL4) protein was expressed by neutrophils present in the tumor microenvironment in replacement HGP CRCLM. We further demonstrate that LOXL4 expression is higher in circulating neutrophils of cancer patients compared with healthy control patients and its expression can be induced by stimulation with lipopolysaccharide and TNF‐α. Our study is the first to show the expression of LOXL4 in neutrophils and reveals the potential for LOXL4‐expressing neutrophils to support the replacement HGP phenotype and to serve as a surrogate biomarker for this subtype of CRCLM. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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Neutrophils influence innate and adaptative immunity by generating numerous cytokines and chemokines whose regulation largely depends on transcriptional activators such as NF-κB and C/EBP factors. In this study, we describe the critical involvement of CREB transcription factors (CREB1 and activating transcription factor-1) in this functional response as well as relevant upstream signaling components. Neutrophil stimulation with LPS or TNF led to the phosphorylation, DNA binding activity, and chemokine promoter association of CREB1 and activating transcription factor-1. These responses occurred downstream of the p38-MSK1 signaling axis, as did the phosphorylation and promoter association of another bZIP factor, C/EBPβ. Conversely, inhibition of RSK1 failed to alter the phosphorylation of either CREB1 or C/EBPβ in neutrophils. From a more functional standpoint, the inhibition of p38 MAPK or MSK1 interfered with cytokine generation in neutrophils. Likewise, overexpression of a dominant-negative CREB1 mutant (K-CREB) or of a point mutant (S133A) resulted in a decreased ability of human neutrophil-like PLB-985 cells to generate inflammatory cytokines (CXCL8, CCL3, CCL4, and TNF-α). Collectively, our data show the involvement of CREB1 in neutrophil cytokine production, the key role of its S133 residue, important upstream signaling events, and the parallel activation of another bZIP factor. These are all potential molecular targets that could be exploited in the context of several chronic inflammatory diseases that prominently feature neutrophils and their products.

Neutrophils are generally the first leukocytes to arrive at sites of inflammation or injury, where they release a variety of inflammatory mediators, which contribute to shaping the ensuing immune response. Here, we show that in neutrophils exposed to physiological stimuli (i.e. LPS and TNF-a), inhibition of the PI3K signaling pathway impairs the synthesis and secretion of IL-8, Mip-1a, and Mip-1b. Further investigation showed that Mip-1a and Mip-1b gene transcription was similarly decreased, whereas IL-8 transcription and steadystate mRNA levels were unaffected. Accordingly, PI3K inhibition had no impact on NF-jB or C/EBP activation, which are essential for IL-8 transcription, but the basis for this selective inhibition of chemokine transcription remains elusive. We nevertheless identified translational targets of the PI3K pathway (S6, S6 kinase, 4E-BP1). Inhibitor studies and overexpression experiments further established that the various effects of PI3K on chemokine production can be ascribed to p85a and p110d subunits. Finally, we show that in LPS-and TNF-activated neutrophils, PI3K acts downstream of the kinases p38 MAPK and TAK1 . Given the importance of neutrophils and their products in numerous chronic inflammatory disorders, the PI3K pathway could represent an attractive therapeutic target.

Gout is a prevalent and incapacitating disease triggered by the deposition of monosodium urate (MSU) crystals in joints, which are also massively infiltrated by neutrophils. The interaction of the latter with MSU crystals triggers several responses, including the generation of inflammatory mediators and of neutrophil extracellular traps (NETs). Though some of the signaling events mobilized by MSU in neutrophils have been described (e.g., Src family kinases, Syk, PKC, PI3K), the picture remains fragmentary. Likewise, the impact of these signaling events on cellular responses is incompletely understood. In this study, we examined transcriptomic changes triggered by MSU in neutrophils and their impact on the corresponding proteins, as well as the role of various signaling pathways in prominent functional responses. We report for the first time that neutrophils can secrete the monocyte chemoattractant, CCL4, in response to MSU. Accordingly, we found that transcription factors NF-κB, CREB, and C/EBP are belatedly activated by MSU crystals, and at least the former is involved in chemokine generation. Moreover, we show that MAPKs and Akt are activated by MSU in neutrophils, that they are under the control of TAK1 and Syk, and that they participate in cytokine generation and NETosis. In the latter instance, we found the phenomenon to be independent of endogenous ROS, but under the control of PAD4. We finally provide evidence that endogenous factors contribute to the belated phosphorylation of kinases and transcription factors in response to MSU. Collectively, our findings unveil potentially important therapeutic targets for gouty arthritis.

A growing number of inflammatory and immune processes in vivo have been shown to be influenced by neutrophil-derived cytokines. Whereas the underlying transcriptional mechanisms are increasingly well understood, the translational regulation of this neutrophil response remains largely unexplored. Here, we show that the MNK1, which participates in translational control in several cell types, is activated in response to physiological neutrophil agonists (LPS, TNF-α) in the cytoplasmic and nuclear compartments. With the use of various pharmacological inhibitors, we found that MNK1 activation takes place downstream of the TAK1-p38 MAPK axis in neutrophils, whereas the MEK/ERK, JNK, PI3K, and PKC pathways are not involved. Pharmacological blockade of MNK1, as well as overexpression experiments, established that cytokine protein synthesis (but not gene expression) is under the control of MNK1 in neutrophils. Likewise, MNK1 inhibition reversed the antiapoptotic effect of LPS and TNF-α in neutrophils, and this was accompanied by a decreased expression of the antiapoptotic protein Mcl-1. Thus, MNK1 appears to be an important regulator of neutrophil responses. Although MNK1 inhibition did not affect protein recruitment to mRNA caps, it decreased the phosphorylation of molecules implicated in translation initiation control, such as S6K, S6, and hyperphosphorylated 4E-BP1. These molecular targets of MNK1 are shared with those of PI3K in neutrophils, and accordingly, MNK1 inhibition partially impaired the belated PI3K/Akt activation elicited by LPS or TNF in these cells. Given the importance of neutrophils and their products in numerous chronic inflammatory disorders, MNK1 could represent an attractive therapeutic target.

Colorectal cancer (CRC) is the third most common cancer worldwide and 50% of CRC patients develop liver metastases. Colorectal cancer liver metastases (CRCLM) present as two major histological growth patterns (HGP) that predict response to treatment/survival: 1. angiogenic tumors characterized by a desmoplastic stroma separating CRC cells from the liver parenchyma and are highly angiogenic and 2. co-opting tumors where tumor cells infiltrate the parenchymal cells in the liver and grow by co-opting the sinusoidal blood vessels between the liver cell plates without sprouting angiogenesis. Angiogenic tumors receiving neoadjuvant anti-angiogenics (anti-VEGF) and chemotherapy have more than double the 5-year overall survival compared to patients with co-opting tumors who have received the same neoadjuvant regimen. In addition, our clinical data revealed that anti-angiogenics could negatively affect outcomes in patients with co-opting lesions. The goal of our study is to understand how the immune system affects the development of the two distinct CRCLM tumors. We used both Nanostring GeoMX spatial protein profiling platform, immunohistochemistry and immunofluorescence, to identify the immune landscapes in chemonaïve and treated human CRCLM tumors. We observed that angiogenic tumors were rich in both CD4 and CD8 T cells with a near absence of neutrophils and macrophages. These adaptive immune cells were also FOXP3 positive indicating an immunosuppressive phenotype. Interestingly, we observed that vessel co-opting tumors have far fewer infiltrating lymphocytes than angiogenic tumors, but interestingly have greater numbers of innate cells - mostly neutrophils and macrophages. The macrophages were further characterized as being M2, tumor promoting, leading to an immunosuppressive environment. We then went on to analyze treated tumors. For those patients treated with chemotherapy alone we observed a larger infiltration of T cells in the angiogenic tumors and the appearance of T cells infiltrating the co-opting tumors. Surprisingly, in patients treated with chemotherapy and anti-angiogenic drugs (ie. anti-VEGF), which is part of the standard of care, the co-opting tumors no longer demonstrated the presence of T cell infiltration and had a similar profile to the chemonaïve tumors. This could explain why chemotherapy in co-opting tumors had a higher overall survival compared to those treated with chemotherapy and anti-VEGF. These results suggest developing treatments aimed at reshaping the different immune landscape in angiogenic and co-opting CRCLM to yield beneficial results for patient overall survival. Furthermore, the identification of immune cells or immune mediators facilitating the development of these two tumor would identify immune cell targets for immunotherapies. Citation Format: Diane H. Kim, Thomas Z. Mayer, Stephanie K. Petrillo, Anthoula Lazaris, Peter Metrakos. Distinct immunosuppressive environments elicited in vessel co-opting and angiogenic colorectal cancer liver metastases and changes following treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6154.

Approximatively 50 % of patients who undergo resection for primary colorectal cancer will develop liver metastases. Liver metastases present as two major histopathological growth patterns (HGP) the desmoplastic and the replacement HGP. In the desmoplastic HGP, the cancer cells are surrounded by a desmoplastic stromal ring preventing their contact with the normal liver. In the replacement HGP, the cancer cells infiltrate the normal liver and replace hepatocytes near the tumour periphery. We have found that the desmoplastic HGP tumors derive their blood supply through angiogenesis while the replacement HGP tumors are non-angiogenic and co-opt the blood vessel of the liver they invade. Furthermore, we have published that patients under chemotherapy presenting with a vessel co-opting phenotype have a worse pathological response and five-year overall survival compared to patients presenting with angiogenic liver metastases. Their prognosis is worse when treated with bevacizumab an anti-VEGF antibody used alongside chemotherapy. CRCLM are considered immunologically cold lesions, with low numbers of infiltrating T-cells, and thought to be unlikely to benefit from immunotherapies. We have recently found that neutrophils and macrophages but not lymphocytes infiltrate vessel co-opting lesions to a greater extent than angiogenic lesions. Using flow cytometry and the Nanostring GeoMx spatial protein profiling platform capable of detecting up to 96 proteins simultaneously on FFPE tissue slices, we established the immunoprofile of immune cells recruited to angiogenic or vessel co-opting CRCLM lesions in chemonaive and treated patients. Many studies have demonstrated that neutrophils and macrophages play an important role in tumor progression, modification of the ECM, angiogenesis, and immunosuppression. We hypothesize that innate immune cells can facilitate blood vessel co-option of CRCLM lesions and contribute to an immunosupressive environment favorable to tumor growth. Fully understanding the role of the innate immune system in the developmend of vessel co-opting CRCLM tumors could allow for the development of immunotherapies capable of converting vessel co-opting lesions into angiogenic lesions that are more successfully treated with chemotherapy and anti-angiogenic therapies. Citation Format: Thomas Z. Mayer, Diane H. Kim, Miran Rada, Stephanie Petrillo, Anthoula Lazaris, Peter Metrakos. Role of innate immune cells in the development of vessel co-opting CRC liver metastases [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3331.