Lukas J.A.C. Hawinkels

IL-17-producing γδ T cells and neutrophils conspire to promote breast cancer metastasis

Metastatic disease remains the primary cause of death for patients with breast cancer. The different steps of the metastatic cascade rely on reciprocal interactions between cancer cells and their microenvironment. Within this local microenvironment and in distant organs, immune cells and their mediators are known to facilitate metastasis formation. However, the precise contribution of tumour-induced systemic inflammation to metastasis and the mechanisms regulating systemic inflammation are poorly understood. Here we show that tumours maximize their chance of metastasizing by evoking a systemic inflammatory cascade in mouse models of spontaneous breast cancer metastasis. We mechanistically demonstrate that interleukin (IL)-1β elicits IL-17 expression from gamma delta (γδ) T cells, resulting in systemic, granulocyte colony-stimulating factor (G-CSF)-dependent expansion and polarization of neutrophils in mice bearing mammary tumours. Tumour-induced neutrophils acquire the ability to suppress cytotoxic T lymphocytes carrying the CD8 antigen, which limit the establishment of metastases. Neutralization of IL-17 or G-CSF and absence of γδ T cells prevents neutrophil accumulation and downregulates the T-cell-suppressive phenotype of neutrophils. Moreover, the absence of γδ T cells or neutrophils profoundly reduces pulmonary and lymph node metastases without influencing primary tumour progression. Our data indicate that targeting this novel cancer-cell-initiated domino effect within the immune system—the γδ T cell/IL-17/neutrophil axis—represents a new strategy to inhibit metastatic disease.

Matrix Metalloproteinase-14 (MT1-MMP)–Mediated Endoglin Shedding Inhibits Tumor Angiogenesis

Endoglin is a transforming growth factor-beta coreceptor with a crucial role in angiogenesis. A soluble form of endoglin is present in the circulation, but the role of soluble endoglin (sEndoglin) is poorly understood. In addition, the endoglin shedding mechanism is not known. Therefore, we examined the role of sEndoglin in tumor angiogenesis and the mechanism by which the extracellular domain of endoglin is released from the membrane.In colorectal cancer specimens, we observed high endothelial endoglin protein expression, accompanied with slightly lower sEndoglin levels in the circulation, compared with healthy controls. In vitro analysis using endothelial sprouting assays revealed that sEndoglin reduced spontaneous and vascular endothelial growth factor-induced endothelial sprouting. Human umbilical vascular endothelial cells were found to secrete high levels of sEndoglin. Endoglin shedding was inhibited by matrix metalloproteinase (MMP) inhibitors and MMP-14 short hairpin RNA, indicating MMP-14 as the major endoglin shedding protease. Coexpression of endoglin and membrane-bound MMP-14 led to a strong increase in sEndoglin levels. Endoglin shedding required a direct interaction between endoglin and membrane-localized MMP-14. Using cleavage site mutants, we determined that MMP-14 cleaved endoglin at a site in close proximity to the transmembrane domain. Taken together, this study shows that MMP-14 mediates endoglin shedding, which may regulate the angiogenic potential of endothelial cells in the (colorectal) tumor microenvironment.

VEGF release by MMP-9 mediated heparan sulphate cleavage induces colorectal cancer angiogenesis

Angiogenesis is crucial for the progression of colorectal carcinomas in which the bioavailability of Vascular Endothelial Growth Factor (VEGF) plays a major role. VEGF bioavailability is regulated by proteolytic release or cleavage. In colorectal cancer patients, we observed a significant correlation between circulating VEGF and tumour tissue Matrix Metalloproteinase-9 (MMP-9) levels but not with MMP-2. Therefore, we evaluated the role of MMP-9 in regulating VEGF bioavailability and subsequent angiogenesis in 3-dimensional human cell culture models. MMP-9 treatment released VEGF dose-dependently from HT29 colon carcinoma spheroids, comparable to heparitinase, a known mediator of VEGF release. Conditioned medium from human neutrophils, containing high amounts of active MMP-9, released VEGF comparable to recombinant MMP-9, in contrast to myofibroblast medium. MMP-9 treated spheroids showed decreased extracellular levels of heparan sulphates, required for VEGF binding to the matrix, whereas the levels in the medium were increased. Western blot analysis revealed that VEGF(165) is the major isoform released by MMP-9 treatment. In vitro experiments indicated that MMP-9 is not capable to cleave VEGF(165) into smaller isoforms, like plasmin does. These data suggested that MMP-9 mediates release rather than the cleavage of larger VEGF isoforms. Medium from MMP-9 treated HT29 spheroids induced endothelial cell sprouting in an angiogenesis assay, comparable to the effect of recombinant VEGF(165). Anti-VEGF antibody treatment resulted in a strongly reduced number of sprouts. In conclusion, we have shown that neutrophil-derived MMP-9 is able to release biologically active VEGF(165) from the ECM of colon cancer cells by the cleavage of heparan sulphates.

Exploring anti-TGF-β therapies in cancer and fibrosis

Transforming growth factor-β (TGF-β) is a multifunctional cytokine, with important roles in maintaining tissue homeostasis. TGF-β signals via transmembrane serine/threonine kinase receptors and intracellular Smad transcriptional regulators. Perturbed TGF-β signaling has been implicated in a large variety of pathological conditions. Increased TGF-β levels have been found in patients with cancer, fibrosis, and systemic sclerosis, and were correlated with disease severity. In cancer, TGF-β mediates tumor invasion and metastasis by affecting both tumor cells and the tumor microenvironment including fibroblast activation and immune suppression. Furthermore, TGF-β is a strong stimulator of extracellular matrix deposition. On the basis of these observations, small molecule inhibitors of the TGF-β receptor kinases, neutralizing antibodies that interfere with ligand–receptor interactions, antisense oligonucleotides reducing TGF-β expression, and soluble receptor ectodomains that sequester TGF-β have been developed to intervene with excessive TGF-β signaling activity in the aforementioned disorders. Here, we review the current state of anti-TGF-β therapy in clinical trials.

Interaction with colon cancer cells hyperactivates TGF-β signaling in cancer-associated fibroblasts

The interaction between epithelial cancer cells and cancer-associated fibroblasts (CAFs) has a major role in cancer progression and eventually in metastasis. In colorectal cancer (CRC), CAFs are present in high abundance, but their origin and functional interaction with epithelial tumor cells has not been elucidated. In this study we observed strong activation of the transforming growth factor-β (TGF-β)/Smad signaling pathway in CRC CAFs, accompanied by decreased signaling in epithelial tumor cells. We evaluated the TGF-β1 response and the expression of target genes including matrix metalloproteinases (MMPs) and plasminogen activator inhibitor (PAI)-1 of various epithelial CRC cell lines and primary CAFs in vitro. TGF-β1 stimulation caused high upregulation of MMPs, PAI-1 and TGF-β1 itself. Next we showed that incubation of CAFs with conditioned medium (CM) from epithelial cancer cells led to hyperactivation of the TGF-β signaling pathway, enhanced expression of target genes like PAI-1, and the expression of α-smooth muscle actin (α-SMA). We propose that the interaction of tumor cells with resident fibroblasts results in hyperactivated TGF-β1 signaling and subsequent transdifferentiation of the fibroblasts into α-SMA-positive CAFs. In turn this leads to cumulative production of TGF-β and proteinases within the tumor microenvironment, creating a cancer-promoting feedback loop.

Elevated TGFβ–Smad signalling in experimental Pkd1 models and human patients with polycystic kidney disease†

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited renal disease characterized by many fluid‐filled cysts and interstitial fibrosis in the kidneys, leading to chronic renal failure. During cystogenesis the renal tubules undergo extensive structural alterations that are accompanied by altered cellular signalling, directly and/or indirectly regulated by the PKD1 and PKD2 proteins. Since transforming growth factor (TGF)‐β signalling modulates cell proliferation, differentiation, apoptosis, adhesion and migration of various cell types, we studied the activation of this signalling pathway in Pkd1‐mutant mouse models at different stages of the disease. Therefore, we analysed expression of the TGFβ–Smad signalling pathway and its target genes in different Pkd1 mutant mouse models in various stages of polycystic disease. Nuclear accumulation of P‐Smad2 in cyst lining epithelial cells was not observed in the initiation phase but was observed at mild and more advanced stages of PKD. This coincides with mild fibrosis and increased mRNA levels of TGFβ target genes, such as fibronectin, collagen type I, plasminogen activator inhibitor 1 and matrix metalloproteinase‐2. At this stage many interstitial fibroblasts were found around cysts, which also showed nuclear localization for P‐Smad2. However, bone morphogenetic protein (BMP) signalling, which can antagonize TGFβ signalling, is not affected, since nuclear expression of P‐Smad1/5/8 and expression of the BMP target gene, inhibitor of DNA binding/differential‐1 (ID‐1) is not altered compared to wild‐type controls. Also, human kidneys with progressive ADPKD showed increased nuclear localization of P‐Smad2, while in general expression of P‐Smad1/5/8 was weak. These results exclude TGFβ signalling at the initiation of cystogenesis, but indicate an important role during cyst progression and in fibrogenesis of progressive ADPKD. Copyright

Tissue level, activation and cellular localisation of TGF-β1 and association with survival in gastric cancer patients

Transforming growth factor-β1 (TGF-β1), a tumour suppressing as well as tumour-promoting cytokine, is stored as an extracellular matrix-bound latent complex. We examined TGF-β1 activation and localisation of TGF-β1 activity in gastric cancer. Gastric tumours showed increased stromal and epithelial total TGF-β1 staining by immunohistochemistry. Active TGF-β1 was present in malignant epithelial cells, but most strongly in smooth muscle actin expressing fibroblasts. Normal gastric mucosa from the same patient showed some staining for total, and little for active TGF-β1. Active TGF-β1 levels were determined by ELISA on tissue homogenates, confirming a strong increase in active TGF-β1 in tumours compared to corresponding normal mucosa. Moreover, high tumour TGF-β1 activity levels were significantly associated with clinical parameters, including worse survival of the patients. Total and active TGF-β1 levels were not correlated, suggesting a specific activation process. Of the different proteases tested, active TGF-β1 levels were only correlated with urokinase activity levels. The correlation with urokinase activity suggests a role for plasmin in TGF-β1 activation in the tumour microenvironment, resulting in transformation of resident fibroblasts to tumour promoting myofibroblasts. In conclusion we have shown localisation and clinical relevance of TGF-β1 activity levels in gastric cancer.

Nuclear receptor NR4A1 promotes breast cancer invasion and metastasis by activating TGF-β signalling

In advanced cancers, the TGF-β pathway acts as an oncogenic factor and is considered to be a therapeutic target. Here using a genome-wide cDNA screen, we identify nuclear receptor NR4A1 as a strong activator of TGF-β signalling. NR4A1 promotes TGF-β/SMAD signalling by facilitating AXIN2-RNF12/ARKADIA-induced SMAD7 degradation. NR4A1 interacts with SMAD7 and AXIN2, and potently and directly induces AXIN2 expression. Whereas loss of NR4A1 inhibits TGF-β-induced epithelial-to-mesenchymal transition and metastasis, slight NR4A1 ectopic expression stimulates metastasis in a TGF-β-dependent manner. Importantly, inflammatory cytokines potently induce NR4A1 expression, and potentiate TGF-β-mediated breast cancer cell migration, invasion and metastasis in vitro and in vivo. Notably, NR4A1 expression is elevated in breast cancer patients with high immune infiltration and its expression weakly correlates with phosphorylated SMAD2 levels, and is an indicator of poor prognosis. Our results uncover inflammation-induced NR4A1 as an important determinant for hyperactivation of pro-oncogenic TGF-β signalling in breast cancer.

Multimodality imaging reveals a gradual increase in matrix metalloproteinase activity at aneurysmal lesions in live fibulin-4 mice.

Background—We imaged the protease activity of matrix metalloproteinases (MMPs) upregulated during aneurysm formation, using protease-activatable near-infrared fluorescence probes. We tested whether these protease-activatable sensors can directly report the in vivo activity of the key biomarkers in aneurysm, using our genetically modified fibulin-4 mouse models for aneurysm formation. Mice homozygous for the fibulin-4 reduced-expression allele (fibulin-4R/R) show dilatation of the ascending aorta and a tortuous, stiffened aorta resulting from disorganized elastic fiber networks. Strikingly, even a moderate reduction in expression of fibulin-4 in the heterozygous fibulin-4+/R mice occasionally results in modest aneurysm formation. Methods and Results—Aorta transcriptome and protein expression analysis of fibulin-4+/R and fibulin-4R/R animals identified excessive transforming growth factor-&bgr; signaling as the critical event in the pathogenesis of aneurysm formation. To determine whether a perturbed elastin lamellar structure arose from induction of transforming growth factor-&bgr;-regulated MMPs, we performed gelatin zymography and used a protease-activatable near-infrared fluorescence probe to monitor and quantify MMP upregulation in animals, using various in vivo optical imaging modules and coregistration of the fluorescence signal with CT images of the same animals. Gelatin zymography demonstrated a significant increase in the presence of the active form of MMP-9 in the aortic arch of fibulin-4R/R mice. In vivo analysis of MMP upregulation using the near-infrared fluorescence probe and subsequent isosurface concentration mapping from reconstructed tomographic images from fibulin-4+/R and fibulin-4R/R mice revealed a graded increase in activation of MMPs within the aneurysmal lesions. Conclusions—We aimed to develop molecular imaging procedures for faster, earlier, and easier recognition of aortic aneurysms. We show that in vivo coregistration of MMP activity by noninvasive tomographic imaging methods allows the detection of increased MMP activity, even before the aneurysm has actually formed.

MMP-2 geno-phenotype is prognostic for colorectal cancer survival, whereas MMP-9 is not

The prognostic significance of single-nucleotide polymorphisms (SNPs) and tumour protein levels of MMP-2 and MMP-9 was evaluated in 215 colorectal cancer patients. Single-nucleotide polymorphism MMP-2−1306T and high MMP-2 levels were significantly associated with worse survival. Extreme tumour MMP-9 levels were associated with poor prognosis but SNP MMP-9−1562C>T was not. Tumour MMP levels were not determined by their SNP genotypes.