Role of Inflammation in the Early Stages of Liver Metastasis

Cancer Metastases to the Liver: Mechanisms of Tumor Cell Colonization

The liver is one of the most common sites for metastasis, which involves the spread from primary tumors to surrounding organs and tissues in the human body. There are a few steps in cancer expansion: invasion, inflammatory processes allowing the hepatic niche to be created, adhesions to ECM, neovascularization, and secretion of enzymes. The spread of tumor cells depends on the microenvironment created by the contribution of many biomolecules, including proteolytic enzymes, cytokines, growth factors, and cell adhesion molecules that enable tumor cells to interact with the microenvironment. Moreover, the microenvironment plays a significant role in tumor growth and expansion. The secreted enzymes help cancer cells facilitate newly formed hepatic niches and promote migration and invasion. Our study discusses pharmacological methods used to prevent liver metastasis by targeting the tumor microenvironment and cancer cell colonization in the liver. We examine randomized studies focusing on median survival duration and median overall survival in patients administered placebo compared with those treated with bevacizumab, ramucirumab, regorafenib, and ziv-aflibercept in addition to current chemotherapy. We also include research on mice and their responses to these medications, which may suppress metastasis progression. Finally, we discuss the significance of non-pharmacological methods, including surgical procedures, radiotherapy, cryotherapy, radiofrequency ablation (RFA), and transarterial embolization (TAE). In conclusion, the given methods can successfully prevent metastases to the liver and prolong the median survival duration and median overall survival in patients suffering from cancer.

Liver metastases

Liver metastases are commonly detected in a range of malignancies including colorectal cancer (CRC), pancreatic cancer, melanoma, lung cancer and breast cancer, although CRC is the most common primary cancer that metastasizes to the liver. Interactions between tumour cells and the tumour microenvironment play an important part in the engraftment, survival and progression of the metastases. Various cells including liver sinusoidal endothelial cells, Kupffer cells, hepatic stellate cells, parenchymal hepatocytes, dendritic cells, resident natural killer cells as well as other immune cells such as monocytes, macrophages and neutrophils are implicated in promoting and sustaining metastases in the liver. Four key phases (microvascular, pre-angiogenic, angiogenic and growth phases) have been identified in the process of liver metastasis. Imaging modalities such as ultrasonography, CT, MRI and PET scans are typically used for the diagnosis of liver metastases. Surgical resection remains the main potentially curative treatment among patients with resectable liver metastases. The role of liver transplantation in the management of liver metastasis remains controversial. Systemic therapies, newer biologic agents (for example, bevacizumab and cetuximab) and immunotherapeutic agents have revolutionized the treatment options for liver metastases. Moving forward, incorporation of genetic tests can provide more accurate information to guide clinical decision-making and predict prognosis among patients with liver metastases.

Postoperative Adverse Events are Associated with Oncologic Recurrence Following Curative-intent Resection for Lung Cancer

BACKGROUND

Up to 50% of patients suffer short-term postoperative adverse events (AEs) and metastatic recurrence in the long-term following curative-intent lung cancer resection. The association between AEs, particularly infectious in nature, and disease recurrence is controversial. We sought to evaluate the association of postoperative AEs on risk of developing recurrence and recurrence-free survival (RFS) following curative-intent lung resection surgery.

METHODS

All lung cancer resections at a single institution (January 2008-July 2015) were included, with prospective collection of AEs using the Thoracic Morbidity & Mortality System. Cox proportional hazards models were used to estimate the effect of AEs on recurrence, with results presented as hazard ratio (HR) with 95% confidence interval (CI). An a priori, clinically driven approach to predictor variable selection was used. Kaplan-Meier curves were used examine the relationship between AE and RFS. p < 0.05 was considered statistically significant.

RESULTS

892 patients underwent curative-intent resection. 342 (38.3%) patients experienced an AE; 69 (7.7%) patients developed infectious AEs. 17.6% (n = 157) of patients had disease recurrence after mean follow-up of 26.5 months. Severe (Grade IV) AEs were associated with increased risk of recurrence (3.40; 95% CI 1.56-7.41) and a trend to decreased RFS. Major infectious AEs were associated with increased risk of recurrence (HR 1.71; CI 1.05-2.8) and earlier time to recurrence (no infectious AE 66 months, minor infectious 41 months, major infectious 54 months; p = 0.02).

CONCLUSION

For patients undergoing curative-intent lung cancer resection, postoperative AEs associated with critical illness or major infection were associated with increased risk of oncologic recurrence.

Toll-like receptors: exploring their potential connection with post-operative infectious complications and cancer recurrence

Cancer is the leading cause of death in North America. Despite modern advances in cancer therapy, many patients will ultimately develop cancer metastasis resulting in mortality. Surgery to resect early stage solid malignancies remains the cornerstone of cancer treatment. However, surgery places patients at risk of developing post-operative infectious complications that are linked to earlier cancer metastatic recurrence and cancer mortality. Toll-like receptors (TLRs) are evolutionarily-conserved sentinel receptors of the innate immune system that are activated by microbial products present during infection, leading to activation of innate immunity. Numerous types of solid cancer cells also express TLRs, with their activation augmenting their ability to metastasize. Similarly, healthy host-tissue TLRs activated during infection induce a prometastatic environment in the host. Cancer cells additionally secrete TLR activating ligands that activate both cancer TLRs and host TLRs to promote metastasis. Consequently, TLRs are an attractive therapeutic candidate to target infection-induced cancer metastasis and progression.

Protective effect of human serum amyloid P on CCl4-induced acute liver injury in mice

Human serum amyloid P (hSAP), a member of the pentraxin family, inhibits the activation of fibrocytes in culture and inhibits experimental renal, lung, skin and cardiac fibrosis. As hepatic inflammation is one of the causes of liver fibrosis, in the present study, we investigated the hepatoprotective effects of hSAP against carbon tetrachloride (CCl₄)-induced liver injury. Our data indicated that hSAP attenuated hepatic histopathological abnormalities and significantly decreased inflammatory cell infiltration and pro-inflammatory factor expression. Moreover, CCl₄-induced apoptosis in the mouse liver was inhibited by hSAP, as measured by terminal-deoxynucleotidyl transferase mediated nick-end labeling (TUNEL) assay and cleaved caspase-3 expression. hSAP significantly restored the expression of B cell lymphoma/leukemia (Bcl)-2 and suppressed the expression of Bcl-2-associated X protein (Bax) in vivo. The number of hepatocytes in early apoptosis stained with Annexin V was significantly reduced by 28–30% in the hSAP treatment group compared with the CCl₄ group, and the expression of Bcl-2 was increased, whereas the expression of Bax and cleaved caspase-3 were significantly inhibited in the hSAP pre-treatment group compared with the CCl₄ group. hSAP administration also inhibited the migration and activation of hepatic stellate cells (HSCs) in CCl₄-injured liver and suppressed the activation of isolated primary HSCs induced by transforming growth factor (TGF)-β1 in vitro. Collectively, these findings suggest that hSAP exerts a protective effect againts CCl₄-induced hepatic injury by suppressing the inflammatory response and hepatocyte apoptosis, potentially by inhibiting HSC activation.

Gram-positive pneumonia augments non-small cell lung cancer metastasis via host toll-like receptor 2 activation

Surgical resection of early stage nonsmall cell lung cancer (NSCLC) is necessary for cure. However, rates of postoperative bacterial pneumonias remain high and may confer an increased risk for metastasis. Toll-like receptors (TLRs) mediate the inflammatory cascade by recognizing microbial products at the surface of numerous cell types in the lung; however, little is known about how host TLRs influence NSCLC metastasis. TLR2 recognizes gram-positive bacterial cell wall components activating innate immunity. We demonstrate that lower respiratory tract infection with Streptococcus pneumonia augments the formation of murine H59 NSCLC liver metastases in C57BL/6 mice through host TLR2 activation. Infected mice demonstrate increased H59 and human A549 NSCLC adhesion to hepatic sinusoids in vivo compared with noninfected controls, a response that is significantly diminished in TLR2 knock-out mice. Intra-tracheal injection of purified TLR2 ligand lipoteichoic acid into mice similarly augments in vivo adhesion of H59 cells to hepatic sinusoids. Additionally, H59 and A549 NSCLC cells incubated with bronchoepithelial conditioned media show increased cell adhesion to extracellular matrix components in vitro and hepatic sinusoids in vivo in a manner that is dependent on bronchoepithelial TLR2 activation and interleukin-6 secretion. TLR2 is therefore a potential therapeutic target for gram-positive pneumonia-driven NSCLC metastasis.

Role of the Microenvironment in Liver Metastasis: From Pre- to Prometastatic Niches

Liver metastases remain a major barrier to successful management of malignant disease, particularly for cancers of the gastrointestinal tract but also for other malignancies, such as breast carcinoma and melanoma. The ability of metastatic cells to survive and proliferate in the liver is determined by the outcome of complex, reciprocal interactions between tumor cells and different local resident subpopulations, including the sinusoidal endothelium, stellate, Kupffer, and inflammatory cells that are mediated through cell-cell and cell-extracellular matrix adhesion and the release of soluble factors. Cross-communication between different hepatic resident cells in response to local tissue damage and inflammation and the recruitment of bone marrow cells further enhance this intercellular communication network. Both resident and recruited cells can play opposing roles in the progression of metastasis, and the balance of these divergent effects determines whether the tumor cells will die, proliferate, and colonize the new site or enter a state of dormancy. Moreover, this delicate balance can be tilted in favor of metastasis, if factors produced by the primary tumor precondition the microenvironment to form niches of activated resident cells that promote tumor expansion. This review aims to summarize current knowledge on these diverse interactions and the impact they can have on the clinical management of hepatic metastases. Clin Cancer Res; 22(24); 5971-82. ©2016 AACR.

The multifaceted role of the microenvironment in liver metastasis: biology and clinical implications

The liver is host to many metastatic cancers, particularly colorectal cancer, for which the last 2 decades have seen major advances in diagnosis and treatment. The liver is a vital organ, and the extent of its involvement with metastatic disease is a major determinant of survival. Metastatic cells arriving in the liver via the bloodstream encounter the microenvironment of the hepatic sinusoid. The interactions of the tumor cells with hepatic sinusoidal and extrasinusoidal cells (endothelial, Kupffer, stellate, and inflammatory cells) determine their fate. The sinusoidal cells can have a dual role, sometimes fatal to the tumor cells but also facilitatory to their survival and growth. Adhesion molecules participate in these interactions and may affect their outcome. Bone marrow-derived cells and chemokines also play a part in the early battle for survival of the metastases. Once the tumor cells have arrested and survived the initial onslaught, tumors can grow within the liver in 3 distinct patterns, reflecting differing host responses, mechanisms of vascularization, and proteolytic activity. This review aims to present current knowledge of the interactions between the host liver cells and the invading metastases that has implications for the clinical course of the disease and the response to treatment.

Neutrophils promote liver metastasis via Mac-1-mediated interactions with circulating tumor cells

Although circulating neutrophils are associated with distant metastasis and poor outcome in a number of epithelial malignancies, it remains unclear whether neutrophils play an active causal role in the metastatic cascade. Using in vivo models of metastasis, we found that neutrophils promote cancer cell adhesion within liver sinusoids and, thereby, influence metastasis. Neutrophil depletion before cancer cell inoculation resulted in a decreased number of gross metastases in an intrasplenic model of liver metastasis. This effect was reversed when inflamed neutrophils were co-inoculated with cancer cells. In addition, early adhesion within liver sinusoids was inhibited in the absence of neutrophils and partially restored with a short perfusion of isolated activated neutrophils. Intravital microscopy showed that cancer cells adhered directly on top of arrested neutrophils, indicating that neutrophils may act as a bridge to facilitate interactions between cancer cells and the liver parenchyma. The adhesion of lipopolysaccharide-activated neutrophils to cancer cells was mediated by neutrophil Mac-1/ICAM-1. Our findings, therefore, show a novel role for neutrophils in the early adhesive steps of liver metastasis.