Colin W. Steele

Inhibition of CXCR2 profoundly suppresses inflammation-driven and spontaneous tumorigenesis

The chemokine receptor CXCR2 is a key mediator of neutrophil migration that also plays a role in tumor development. However, CXCR2 influences tumors through multiple mechanisms and might promote or inhibit tumor development depending on context. Here, we used several mouse models of spontaneous and inflammation-driven neoplasia to define indispensable roles for CXCR2 in benign and malignant tumors. CXCR2-activating chemokines were part of the secretome of cultured primary benign intestinal adenomas (ApcMin/+) and highly expressed by all tumors in all models. CXCR2 deficiency profoundly suppressed inflammation-driven tumorigenesis in skin and intestine as well as spontaneous adenocarcinoma formation in a model of invasive intestinal adenocarcinoma (AhCreER;Apcfl/+;Ptenfl/fl mice). Pepducin-mediated CXCR2 inhibition reduced tumorigenesis in ApcMin/+ mice. Ly6G+ neutrophils were the dominant source of CXCR2 in blood, and CXCR2 deficiency attenuated neutrophil recruitment. Moreover, systemic Ly6G+ cell depletion purged CXCR2-dependent tumor-associated leukocytes, suppressed established skin tumor growth and colitis-associated tumorigenesis, and reduced ApcMin/+ adenoma formation. CXCR2 is thus a potent protumorigenic chemokine receptor that directs recruitment of tumor-promoting leukocytes into tissues during tumor-inducing and tumor-driven inflammation. Similar leukocyte populations were also found in human intestinal adenomas, which suggests that CXCR2 antagonists may have therapeutic and prophylactic potential in the treatment of cancer.

RE: nab-Paclitaxel Plus Gemcitabine for Metastatic Pancreatic Cancer: Long-Term Survival From a Phase III Trial.

We read with interest the article by Goldstein and colleagues that reports the long-term results of the large phase III randomized trial (IMPACT) of nab-paclitaxel plus gemcitabine or gemcitabine alone in patients with metastatic pancreatic cancer, extending support for the superior efficacy of this combination therapy (1). They reported that the presence of a systemic inflammatory response, as evidenced by an elevated neutrophil lymphocyte ratio (NLR), effectively stratified survival independent of the trial treatment. A pooled treatment analysis demonstrated that patients with an NLR of 5 or less had a statistically significantly prolonged survival compared with patients with an NLR of more than 5 (median = 9.1 vs 5.0 months, P < .001). In the nab-Paclitaxel plus gemcitabine arm there was a statistically significantly longer overall survival vs the gemcitabine arm alone in patients with an NLR of 5 or less (P < .001). Furthermore, when there was evidence of a raised systemic inflammatory response, a trend was evident favoring prolonged survival in the nab-paclitaxel plus gemcitabine arm vs the gemcitabine alone group (P = .079). These results confirm our previous observations in patients with pancreatic adenocarcinoma, that an elevated NLR is an important independent prognostic factor (2). However, there is good evidence that assessment of the systemic inflammatory response using acute phase proteins, in particular C-reactive protein (CRP) and albumin (Glasgow Prognostic Score [GPS]) has superior prognostic value in a variety of common solid tumors (3), including pancreatic cancer both in resectable and nonresectable forms (2). Therefore, it is clear that even in such a poor-prognosis tumor as pancreatic cancer outcomes can be stratified according to the systemic inflammatory response. This new knowledge offers the possibility for simple and effective stratification for patients with this difficult-to-treat cancer. For heterogeneous cancers, in particular pancreatic cancer, a stratified medicine approach offers potential to target an individual’s cancer with the right treatment for the right patient (4). This strategy could improve overall outcomes and quality of life for patients by minimizing unnecessary side effects arising from ineffective therapies. However, as demonstrated in the present study, the concept of stratification should not be limited to tumoror gene-centric aspects but extended to consider patient or host aspects including the burden of the systemic inflammatory response. Moreover, beyond stratification there is also an opportunity for therapeutic targeting of the systemic inflammatory response. Given the role of JAK-STAT signaling in the inflammatory responses of patients with pancreatic cancer (5), it is of interest that a recent randomized phase II trial of the JAK1/JAK2 inhibitor ruxolitinib combined with capecitabine in patients with metastatic pancreatic cancer revealed a statistically significantly prolonged survival for those patients who were administered ruxolitinib with coexisting evidence of an elevated systemic inflammatory response, as measured by CRP and/or the modified GPS (6). It is also of interest that nab-paclitaxel itself has potential to alter the tumor stroma and immune environment (7). In summary, the work of Goldstein and colleagues (1) confirms the prognostic value of the systemic inflammatory response in patients with metastatic pancreatic cancer. Furthermore, it heralds a new era in which the systemic inflammatory response becomes a legitimate target for treatment of these patients.

CXCR2 Inhibition Profoundly Suppresses Metastases and Augments Immunotherapy in Pancreatic Ductal Adenocarcinoma.

Summary CXCR2 has been suggested to have both tumor-promoting and tumor-suppressive properties. Here we show that CXCR2 signaling is upregulated in human pancreatic cancer, predominantly in neutrophil/myeloid-derived suppressor cells, but rarely in tumor cells. Genetic ablation or inhibition of CXCR2 abrogated metastasis, but only inhibition slowed tumorigenesis. Depletion of neutrophils/myeloid-derived suppressor cells also suppressed metastasis suggesting a key role for CXCR2 in establishing and maintaining the metastatic niche. Importantly, loss or inhibition of CXCR2 improved T cell entry, and combined inhibition of CXCR2 and PD1 in mice with established disease significantly extended survival. We show that CXCR2 signaling in the myeloid compartment can promote pancreatic tumorigenesis and is required for pancreatic cancer metastasis, making it an excellent therapeutic target.

Targeting the LOX/hypoxia axis reverses many of the features that make pancreatic cancer deadly: inhibition of LOX abrogates metastasis and enhances drug efficacy

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer‐related mortality. Despite significant advances made in the treatment of other cancers, current chemotherapies offer little survival benefit in this disease. Pancreaticoduodenectomy offers patients the possibility of a cure, but most will die of recurrent or metastatic disease. Hence, preventing metastatic disease in these patients would be of significant benefit. Using principal component analysis (PCA), we identified a LOX/hypoxia signature associated with poor patient survival in resectable patients. We found that LOX expression is upregulated in metastatic tumors from Pdx1‐Cre KrasG12D/+ Trp53R172H/+ (KPC) mice and that inhibition of LOX in these mice suppressed metastasis. Mechanistically, LOX inhibition suppressed both migration and invasion of KPC cells. LOX inhibition also synergized with gemcitabine to kill tumors and significantly prolonged tumor‐free survival in KPC mice with early‐stage tumors. This was associated with stromal alterations, including increased vasculature and decreased fibrillar collagen, and increased infiltration of macrophages and neutrophils into tumors. Therefore, LOX inhibition is able to reverse many of the features that make PDAC inherently refractory to conventional therapies and targeting LOX could improve outcome in surgically resectable disease.

Exploiting inflammation for therapeutic gain in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy associated with <5% 5-year survival, in which standard chemotherapeutics have limited benefit. The disease is associated with significant intra- and peritumoral inflammation and failure of protective immunosurveillance. Indeed, inflammatory signals are implicated in both tumour initiation and tumour progression. The major pathways regulating PDAC-associated inflammation are now being explored. Activation of leukocytes, and upregulation of cytokine and chemokine signalling pathways, both have been shown to modulate PDAC progression. Therefore, targeting inflammatory pathways may be of benefit as part of a multi-target approach to PDAC therapy. This review explores the pathways known to modulate inflammation at different stages of tumour development, drawing conclusions on their potential as therapeutic targets in PDAC.

Clinical potential of microRNAs in pancreatic ductal adenocarcinoma.

Objectives: Aggressive invasion and early metastases are characteristic features of pancreatic ductal adenocarcinoma (PDAC). More than 90% of patients have surgically nonresectable disease at presentation. Despite increasing knowledge of the genetics of this complex disease, systemic therapies, particularly gemcitabine, have modest clinical benefit and marginal survival advantage. MicroRNAs have been shown to have a role in oncogenesis, invasion, and metastases via epigenetic posttranscriptional gene regulation. Our objective was to discuss the clinical impact of microRNAs within PDAC. Methods: This review details the understanding of microRNAs to date and explores the clinical utility of microRNAs in PDAC. Results: Recent studies have focused on the impact of microRNA expression in PDAC, many of which have shown the diagnostic, predictive, and prognostic utility of microRNA profiling in PDAC identifying numerous potential targets including miR-21, miR-196a, and miR-217. Conclusions: MicroRNA stability in body fluid and tissue samples makes this area one of the most promising for earlier detection of PDAC. Indeed, microRNAs may in the future serve as a long-awaited screening tool for PDAC. Furthermore, microRNA expression profiling in PDAC may be incorporated into modern treatment algorithms to enhance therapeutic management. Equally as exciting is the potential for novel therapeutics directed against these important disease mediators.

CXCR2 inhibition suppresses acute and chronic pancreatic inflammation.

Pancreatitis is a significant clinical problem and the lack of effective therapeutic options means that treatment is often palliative rather than curative. A deeper understanding of the pathogenesis of both acute and chronic pancreatitis is necessary to develop new therapies. Pathological changes in pancreatitis are dependent on innate immune cell recruitment to the site of initial tissue damage, and on the coordination of downstream inflammatory pathways. The chemokine receptor CXCR2 drives neutrophil recruitment during inflammation, and to investigate its role in pancreatic inflammation, we induced acute and chronic pancreatitis in wild‐type and Cxcr2−/− mice. Strikingly, Cxcr2−/− mice were strongly protected from tissue damage in models of acute pancreatitis, and this could be recapitulated by neutrophil depletion or by the specific deletion of Cxcr2 from myeloid cells. The pancreata of Cxcr2−/− mice were also substantially protected from damage during chronic pancreatitis. Neutrophil depletion was less effective in this model, suggesting that CXCR2 on non‐neutrophils contributes to the development of chronic pancreatitis. Importantly, pharmacological inhibition of CXCR2 in wild‐type mice replicated the protection seen in Cxcr2−/− mice in acute and chronic models of pancreatitis. Moreover, acute pancreatic inflammation was reversible by inhibition of CXCR2. Thus, CXCR2 is critically involved in the development of acute and chronic pancreatitis in mice, and its inhibition or loss protects against pancreatic damage. CXCR2 may therefore be a viable therapeutic target in the treatment of pancreatitis.

Targeting inflammation in pancreatic cancer: Clinical translation

Preclinical modelling studies are beginning to aid development of therapies targeted against key regulators of pancreatic cancer progression. Pancreatic cancer is an aggressive, stromally-rich tumor, from which few people survive. Within the tumor microenvironment cellular and extracellular components exist, shielding tumor cells from immune cell clearance, and chemotherapy, enhancing progression of the disease. The cellular component of this microenvironment consists mainly of stellate cells and inflammatory cells. New findings suggest that manipulation of the cellular component of the tumor microenvironment is possible to promote immune cell killing of tumor cells. Here we explore possible immunogenic therapeutic strategies. Additionally extracellular stromal elements play a key role in protecting tumor cells from chemotherapies targeted at the pancreas. We describe the experimental findings and the pitfalls associated with translation of stromally targeted therapies to clinical trial. Finally, we discuss the key inflammatory signal transducers activated subsequent to driver mutations in oncogenic Kras in pancreatic cancer. We present the preclinical findings that have led to successful early trials of STAT3 inhibitors in pancreatic adenocarcinoma.

Timing is everything: Brca2 and p53 mutations in pancreatic cancer.

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Abstract PR10: CXCR2 Inhibition Suppresses Metastasis and Improves the Response to Immunotherapy in Pancreatic Cancer

PDAC is predicted to become the second commonest cause of cancer death in the western world by 2030. Aggressive invasion and early metastases are characteristic of the disease, and even the few patients eligible for potentially curative resection inevitably develop recurrent or metastatic disease. We now show that CXCR2 signalling is upregulated in human pancreatic cancer, predominantly in neutrophils at the tumour invasive edge. In mouse models, genetic ablation or inhibition of CXCR2 abrogated metastasis while inhibition also slowed tumorigenesis, particularly when combined with chemotherapy. Depletion of neutrophils also suppressed metastasis, suggesting a key role for CXCR2 in establishing and maintaining the metastatic niche. Indications from trials thus far suggest that immunotherapy will not work as a single agent strategy in pancreatic cancer patients. Importantly, we find that loss or inhibition of CXCR2 improved T-cell entry and combined inhibition of CXCR2 and PD1 in mice with established disease caused a significant extension of survival. Thus, our data highlight two novel therapeutic opportunities for PDAC: first the use of CXCR2 inhibitors in surgically-resected patients to prevent recurrence at distant sites, and second, the use of CXCR2 inhibition in combination with immunotherapy in surgically unresectable advanced disease. This abstract is also being presented as Poster B55 Citation Format: Colin Steele, Saadia Karim, Josh Leach, Peter Bailey, Andrew Biankin, Rob Nibbs, Simon Barry, Owen Sansom, Jen Morton.{Authors}. CXCR2 Inhibition Suppresses Metastasis and Improves the Response to Immunotherapy in Pancreatic Cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr PR10.