The inflammatory microenvironment of HCC – The plot becomes complex
Authors: Jörg Schrader, John P. Iredale
Journal: Journal of Hepatology (2010)

Peritumoral neutrophils link inflammatory response to disease progression by fostering angiogenesis in hepatocellular carcinomaJournal of HepatologyVol. 54Issue 5PreviewSubstantial evidence indicates that inflammation is a critical component of tumor progression. Hepatocellular carcinoma (HCC) is usually derived from inflamed cirrhotic liver with extensive leukocyte infiltration. Neutrophils are the common inflammatory infiltrate in tumors, but their nature and regulation in human cancers remain elusive. Full-Text PDF A key role of chronic hepatocyte damage, leading to liver inflammation, fibrosis, and eventually cirrhosis, in the development of hepatocellular carcinoma (HCC) has been long established. Although the chronic stimulation of liver regeneration is one of the main contributors to HCC development, the accompayning inflammation has also been established as a pivotal component [1El-Serag H.B. Rudolph K.L. Hepatocellular carcinoma: epidemiology and molecular carcinogenesis.Gastroenterology. 2007; 132: 2557-2576Abstract Full Text Full Text PDF PubMed Scopus (4364) Google Scholar, 2Berasain C. Castillo J. Perugorria M.J. Latasa M.U. Prieto J. Avila M.A. Inflammation and liver cancer: new molecular links.Ann NY Acad Sci. 2009; 1155: 206-221Crossref PubMed Scopus (315) Google Scholar]. Less is known about the role of ongoing inflammation with regard to disease progression once HCC has developed. A first hint of the relevance of the inflammatory response in tumour progression came from a seminal study from Budhu et al., linking a pro-inflammatory peritumoural cytokine milieu with the prognosis and metastatic spread of HCC [[3]Budhu A. Forgues M. Ye Q.H. Jia H.L. He P. Zanetti K.A. et al.Prediction of venous metastases, recurrence, and prognosis in hepatocellular carcinoma based on a unique immune response signature of the liver microenvironment.Cancer Cell. 2006; 10: 99-111Abstract Full Text Full Text PDF PubMed Scopus (672) Google Scholar]. There is increasing evidence that the inflammatory milieu, by virtue of both its soluble signals, cellular infiltrates, and physical properties, may alter the behaviour of HCC [4Kuang D.M. Peng C. Zhao Q. Wu Y. Chen M.S. Zheng L. Activated monocytes in peritumoral stroma of hepatocellular carcinoma promote expansion of memory T helper 17 cells.Hepatology. 2010; 51: 154-164Crossref PubMed Scopus (197) Google Scholar, 5Ju M.J. Qiu S.J. Fan J. Xiao Y.S. Gao Q. Zhou J. et al.Peritumoral activated hepatic stellate cells predict poor clinical outcome in hepatocellular carcinoma after curative resection.Am J Clin Pathol. 2009; 131: 498-510Crossref PubMed Scopus (107) Google Scholar, 6Schrader J, Gordon-Walker TT, van Deemter M, Aucott RL, Quaas A, Walsh S, et al. Matrix stiffness modulates proliferation, chemotherapeutic response and dormancy in hepatocellular carcinoma cells. Hepatology, in press.Google Scholar]. In the study published in this issue by Kuang et al., the role of infiltrating neutrophils in the stroma of HCC, in the perspective of clinical and experimental disease progression, has been characterized [[7]Kuang D.M. Zhao Q. Wu Y. Peng C. Wang J. Xu Z. et al.Peritumoral neutrophils link inflammatory response to disease progression by fostering angiogenesis in hepatocellular carcinoma.J Hepatol. 2011; 54: 948-955Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar]. The authors found an enrichment of neutrophils predominantly in the peritumoral stroma surrounding the cancer cell nests at the interface between tumour and non-tumour tissue and identified a high neutrophil infiltration as a powerful predictor of disease progression and poor overall survival after HCC resection. Interestingly, the neutrophil numbers, neither within the tumour nor in the adjacent non-tumour liver, proved to be of prognostic value. Neutrophil numbers correlated with IL-17 positive lymphocyte numbers – a subset of CD4+ T-cells previously identified by the same group as important immune modulators of HCC – in the same region of the tumour. Although IL-17 did not seem to have a direct effect on neutrophil recruitment, it was able to stimulate epithelial CXC chemokine production, thereby attracting neutrophils to the stroma and prolonging neutrophil survival. The tumour cell activated neutrophils were identified as the main source of MMP-9 production, which was linked to angiogenesis in vitro and correlated with vessel density in clinical HCC samples. Importantly, depletion of neutrophils, by Gr1-targeting antibody treatment of mice, delayed HCC xenograft development and impaired tumour angiogenesis. A poor predictive value of an elevated neutrophil-to-lymphocyte ratio in peripheral blood has been long established in many tumours, including HCC [[8]Gomez D. Farid S. Malik H.Z. Young A.L. Toogood G.J. Lodge J.P. et al.Preoperative neutrophil-to-lymphocyte ratio as a prognostic predictor after curative resection for hepatocellular carcinoma.World J Surg. 2008; 32: 1757-1762Crossref PubMed Scopus (329) Google Scholar]. It is only recently that intratumoural neutrophils have been associated with higher recurrence rates and decreased survival in patients with renal cancer and hepatocellular carcinoma after curative resection [9Jensen H.K. Donskov F. Marcussen N. Nordsmark M. Lundbeck F. von der Maase H. Presence of intratumoral neutrophils is an independent prognostic factor in localized renal cell carcinoma.J Clin Oncol. 2009; 27: 4709-4717Crossref PubMed Scopus (330) Google Scholar, 10Li Y.W. Qiu S.J. Fan J. Zhou J. Gao Q. Xiao Y.S. et al.Intratumoral neutrophils: a poor prognostic factor for hepatocellular carcinoma following resection.J Hepatol. 2011; 54: 497-505Abstract Full Text Full Text PDF PubMed Scopus (197) Google Scholar]. The present study extends these findings with regard to the precise localization of the neutrophil infiltration in the peritumoral stroma [[7]Kuang D.M. Zhao Q. Wu Y. Peng C. Wang J. Xu Z. et al.Peritumoral neutrophils link inflammatory response to disease progression by fostering angiogenesis in hepatocellular carcinoma.J Hepatol. 2011; 54: 948-955Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar]. It is in this area where the main interaction between the tumour and the surrounding tissue will take place. This is the predominant place for both angiogenesis and cancer cell invasion, thereby fostering tumour progression and metastatic spread. The neutrophils can stimulate angiogenesis by releasing MMP9 and enhance invasion of tumour cells by production of chemoattractant growth factors like the hepatocyte growth factor and others [11Nozawa H. Chiu C. Hanahan D. Infiltrating neutrophils mediate the initial angiogenic switch in a mouse model of multistage carcinogenesis.Proc Natl Acad Sci USA. 2006; 103: 12493-12498Crossref PubMed Scopus (671) Google Scholar, 12Wislez M. Rabbe N. Marchal J. Milleron B. Crestani B. Mayaud C. et al.Hepatocyte growth factor production by neutrophils infiltrating bronchioloalveolar subtype pulmonary adenocarcinoma: role in tumor progression and death.Cancer Res. 2003; 63: 1405-1412PubMed Google Scholar]. In addition, neutrophils can contribute to or prevent the cytotoxic immune response against tumour cells by interacting with CD8+ cytotoxic T-cells, depending on their activation status [[13]Fridlender Z.G. Sun J. Kim S. Kapoor V. Cheng G. Ling L. et al.Polarization of tumor-associated neutrophil phenotype by TGF-beta: "N1" versus "N2" TAN.Cancer Cell. 2009; 16: 183-194Abstract Full Text Full Text PDF PubMed Scopus (1920) Google Scholar]. Whether a polarized N1 or N2 phenotype of neutrophils – as proposed by Fridlender et al. in analogy to macrophage phenotypes [[13]Fridlender Z.G. Sun J. Kim S. Kapoor V. Cheng G. Ling L. et al.Polarization of tumor-associated neutrophil phenotype by TGF-beta: "N1" versus "N2" TAN.Cancer Cell. 2009; 16: 183-194Abstract Full Text Full Text PDF PubMed Scopus (1920) Google Scholar] – exists in HCC, needs to be further clarified, but clearly the local cytokine environment including TGFβ could be responsible for shifting phenotypes. It would be most interesting to further characterize the infiltrating neutrophil phenotype in HCC and link this to disease progression and outcome. The peritumoral stroma surrounding the cancer cell nest at the tumour edge, attracting neutrophils, macrophages, and lymphocytes, becomes the "battle ground" for the interaction of the tumour with the immune system [4Kuang D.M. Peng C. Zhao Q. Wu Y. Chen M.S. Zheng L. Activated monocytes in peritumoral stroma of hepatocellular carcinoma promote expansion of memory T helper 17 cells.Hepatology. 2010; 51: 154-164Crossref PubMed Scopus (197) Google Scholar, 5Ju M.J. Qiu S.J. Fan J. Xiao Y.S. Gao Q. Zhou J. et al.Peritumoral activated hepatic stellate cells predict poor clinical outcome in hepatocellular carcinoma after curative resection.Am J Clin Pathol. 2009; 131: 498-510Crossref PubMed Scopus (107) Google Scholar, 7Kuang D.M. Zhao Q. Wu Y. Peng C. Wang J. Xu Z. et al.Peritumoral neutrophils link inflammatory response to disease progression by fostering angiogenesis in hepatocellular carcinoma.J Hepatol. 2011; 54: 948-955Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar]. Given the additional presence of activated myofibroblasts in this area, all components of the classic wound healing response are present, reiterating the phrase of "tumours are wounds that do not heal" coined by Dvorak [[14]Dvorak H.F. Tumors: wounds that do not heal. Similarities between tumor stroma generation and wound healing.N Engl J Med. 1986; 315: 1650-1659Crossref PubMed Scopus (3471) Google Scholar]. The physiological role of wound healing is to combat infection, close a tissue defect by inital fibrosis, recruit new blood vessels, and re-establish tissue integrity [[15]Velnar T. Bailey T. Smrkolj V. The wound healing process: an overview of the cellular and molecular mechanisms.J Int Med Res. 2009; 37: 1528-1542Crossref PubMed Scopus (1146) Google Scholar]. With regard to tumour-associated inflammation, angiogenesis and fibrosis are common outcomes, but the re-establishment of tissue integrity fails due to the persistence of the causative agent, the "abberant" tumour cells. The recruitment of inflammatory and stroma cells to sites of tissue repair and infection is a complex process involving cytokines, chemokines, and direct cell–cell interactions. Similarly, the establishment of the inflammatory tumour environment is growing a complex tissue and involves an extensive cross-talk between tumour cells and infiltrating cells. Kuang et al. define a communication circuit between Th17 lymphocytes, epithelial tumour cells, neutrophils, and feedback via tumour cells to endothelial cells, leading to angiogenesis [[7]Kuang D.M. Zhao Q. Wu Y. Peng C. Wang J. Xu Z. et al.Peritumoral neutrophils link inflammatory response to disease progression by fostering angiogenesis in hepatocellular carcinoma.J Hepatol. 2011; 54: 948-955Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar]. Certainly, other communication circuits will also exist and have, for example, been established for a cross-talk between tumour cells, activated macrophages, and Th17 cells [[4]Kuang D.M. Peng C. Zhao Q. Wu Y. Chen M.S. Zheng L. Activated monocytes in peritumoral stroma of hepatocellular carcinoma promote expansion of memory T helper 17 cells.Hepatology. 2010; 51: 154-164Crossref PubMed Scopus (197) Google Scholar]. A longstanding area of debate is whether the tumour microenvironment in general is pro- or anti-inflammatory and whether the infiltrating immune cells promote tumour growth or act as immune-surveillance to combat tumour progression. The answer to these questions will not be easy to define. Currently, our knowledge would suggest a "bit of both" answer. The tumours utilize a pro-inflammatory environment with the aim of tissue re-modelling, angiogenesis, and stimulation of migration and invasion [[16]Mantovani A. Allavena P. Sica A. Balkwill F. Cancer-related inflammation.Nature. 2008; 454: 436-444Crossref PubMed Scopus (7574) Google Scholar]. On the other hand, they induce powerful mechanisms to prevent the immune attack of tumour cells by inducing a suppressive phenotype in macrophages and recruiting regulatory T cells, thereby preventing cytotoxic lymphocyte function [[17]Shirabe K, Motomura T, Muto J, Toshima T, Matono R, Mano Y, et al. Tumor-infiltrating lymphocytes and hepatocellular carcinoma: pathology and clinical management. Int J Clin Oncol, in press.Google Scholar]. This paradoxical state of "a bit of both worlds" might be similar to a later phase in the wound healing response, where a certain pro-inflammatory action is still needed to re-organize and repair the tissue but also immune suppression is needed to cool down the immune response to prevent further tissue damage and allow epithelial cells to resume normal function [[15]Velnar T. Bailey T. Smrkolj V. The wound healing process: an overview of the cellular and molecular mechanisms.J Int Med Res. 2009; 37: 1528-1542Crossref PubMed Scopus (1146) Google Scholar]. Exploiting the inflammatory response to combat cancer would require a shift of the whole immune response rather than interfering with single cytokines or immune cells. A skewing of the inflammatory reaction towards either end of the wound healing response, namely acute inflammation associated with tissue damage or complete resolution of the inflammatory reaction, would be the aim of this intervention. Indeed, clinical data show that, on the one hand, a cytokine profile linked with acute inflammation (e.g. TNFα, IFNγ) and infiltrating cytotoxic lymphocytes can prevent tumour progression and, on the other hand, non-inflammatory tumours have in general a more benign course [3Budhu A. Forgues M. Ye Q.H. Jia H.L. He P. Zanetti K.A. et al.Prediction of venous metastases, recurrence, and prognosis in hepatocellular carcinoma based on a unique immune response signature of the liver microenvironment.Cancer Cell. 2006; 10: 99-111Abstract Full Text Full Text PDF PubMed Scopus (672) Google Scholar, 7Kuang D.M. Zhao Q. Wu Y. Peng C. Wang J. Xu Z. et al.Peritumoral neutrophils link inflammatory response to disease progression by fostering angiogenesis in hepatocellular carcinoma.J Hepatol. 2011; 54: 948-955Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar, 16Mantovani A. Allavena P. Sica A. Balkwill F. Cancer-related inflammation.Nature. 2008; 454: 436-444Crossref PubMed Scopus (7574) Google Scholar, 17Shirabe K, Motomura T, Muto J, Toshima T, Matono R, Mano Y, et al. Tumor-infiltrating lymphocytes and hepatocellular carcinoma: pathology and clinical management. Int J Clin Oncol, in press.Google Scholar]. Conversely, it may be that specific HCCs develop and spread highly effectively in the presence of significant inflammation and fibrosis. Within this context, the evolution of cancer would favour the development of one which responded positively or elicited a growth/survival advantage from an inflammatory milieu. Thus ultimately, it may prove that reducing inflammation is an important approach to certain tumours. Are there similarities between the chronic liver inflammation leading to fibrosis and the tumour-associated inflammation in HCC? Certainly, activated macrophages and myofibroblasts are key-players of both fibrosis development and HCC progression. In analogy to the present study by Kuang et al., Th17 cells have recently been found to also contribute to the inflammatory reaction in alcoholic hepatitis [[18]Lemmers A. Moreno C. Gustot T. Maréchal R. Degré D. Demetter P. et al.The interleukin-17 pathway is involved in human alcoholic liver disease.Hepatology. 2009; 49: 646-657Crossref PubMed Scopus (289) Google Scholar]. In this setting, these cells are able to recruit neutrophils via chemokine induction in activated stellate cells. Although in this context neutrophils contribute to the ongoing inflammation and liver damage, their role in liver fibrosis is not yet clear, as they also can contribute to the resolution of fibrosis after the insulting stimulus is gone [[19]Harty M.W. Papa E.F. Huddleston H.M. Young E. Nazareth S. Riley C.A. et al.Hepatic macrophages promote the neutrophil-dependent resolution of fibrosis in repairing cholestatic rat livers.Surgery. 2008; 143: 667-678Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar]. Further studies might clarify this issue and may bring the proof that different neutrophil subtypes are responsible for these apparently opposing outcomes. One interesting question would be whether the tumour-associated inflammation is a mere extension of the chronic liver inflammation which leads to tumour formation, or whether the tumours themselves recruit and modulate their own inflammatory environment. Results from xenograft studies showing immune cell recruitment might favour the latter. On the other hand, clinical data show that the activity of liver inflammation in the non-tumourous liver per se is a poor prognostic factor for survival after HCC resection, arguing for the former [[3]Budhu A. Forgues M. Ye Q.H. Jia H.L. He P. Zanetti K.A. et al.Prediction of venous metastases, recurrence, and prognosis in hepatocellular carcinoma based on a unique immune response signature of the liver microenvironment.Cancer Cell. 2006; 10: 99-111Abstract Full Text Full Text PDF PubMed Scopus (672) Google Scholar]. Interestingly, the present study suggests that the edge of the tumour represents an important interface for both inflammatory environments. Further studies will have to clarify the differences and similarities of the inflammatory environments and might help to identify pro-tumourigenic and anti-tumourigenic milieus. The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.