Toll-like receptor-4 agonist inhibits motility and invasion of hepatoblastoma HepG2 cells in vitro

Targeted immune activation in pediatric solid tumors: opportunities to complement local control approaches

Surgery or radiation therapy is nearly universally applied for pediatric solid tumors. In many cases, in diverse tumor types, distant metastatic disease is present and evades surgery or radiation. The systemic host response to these local control modalities may lead to a suppression of antitumor immunity, with potential negative impact on the clinical outcomes for patients in this scenario. Emerging evidence suggests that the perioperative immune responses to surgery or radiation can be modulated therapeutically to preserve anti-tumor immunity, with the added benefit of preventing these local control approaches from serving as pro-tumorigenic stimuli. To realize the potential benefit of therapeutic modulation of the systemic response to surgery or radiation on distant disease that evades these modalities, a detailed knowledge of the tumor-specific immunology as well as the immune responses to surgery and radiation is imperative. In this Review we highlight the current understanding of the tumor immune microenvironment for the most common peripheral pediatric solid tumors, the immune responses to surgery and radiation, and current evidence that supports the potential use of immune activating agents in the perioperative window. Finally, we define existing knowledge gaps that limit the current translational potential of modulating perioperative immunity to achieve effective anti-tumor outcomes.

A896G and C1196T Polymorphisms Within the TLR4 Gene Abate Toll-Like Receptor 4-Mediated Signaling in HepG2 Cells

Toll-like receptor 4 (TLR4) appears to play an important role in the development and progression of hepatocellular carcinoma (HCC), but it is unclear whether single-nucleotide polymorphisms (SNPs) in the TLR4 gene influence HCC. In this study, we investigated the effects of TLR4 SNPs on HepG2 cell survival and proliferation, migration, and invasion. Plasmids carrying wild-type or mutant versions of the TLR4 gene (A896G and/or C1196T) were stably transfected into HepG2 cells, and cell viability and proliferation were analyzed using the Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays, whereas apoptosis was assessed using flow cytometry. Migration and invasion were measured in a transwell chamber assay, and expression of inflammatory cytokines and downstream effectors was examined using real-time PCR and western blotting. Specific inhibitors of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), or phosphatidylinositol 3-kinase (PI3K) were added to the HepG2 cultures to explore the potential role of each pathway in TLR4 signaling. TLR4 SNPs did not affect expression levels in transfected cells. Compared with wild-type TLR4, mutant TLR4 was associated with lower cell proliferation, migration, invasion, and apoptotic threshold. In addition, the mutations were associated with significantly lower expression of nuclear factor κB (NF-κB), IL-6, and TGF-β1, even after stimulation with lipopolysaccharide. The expression of p-Akt was similar in the presence of wild-type or mutant TLR4. The 896G and 1196T SNPs in the TLR4 gene are associated with reduced TLR4-mediated signaling and, therefore, with lower survival, proliferation, and metastasis in HepG2 cells.

Application potential of toll-like receptors in cancer immunotherapy: Systematic review

Toll-like receptors (TLRs), as the most important pattern recognition receptors in innate immunity, play a pivotal role in inducing immune response through recognition of microbial invaders or specific agonists. Recent studies have suggested that TLRs could serve as important regulators in the development of a variety of cancer. However, increasing evidences have shown that TLRs may display quite opposite outcomes in cancer development. Although several potential therapeutic Toll-like receptor ligands have been found, the mechanism and therapy prospect of TLRs in cancer development has to be further elucidated to accelerate the clinical application. By performing a systematic review of the present findings on TLRs in cancer immunology, we attempted to evaluate the therapeutic potential of TLRs in cancer therapy and elucidate the potential mechanism of cancer progress regulated by TLR signaling and the reported targets on TLRs for clinical application. An electronic databases search was conducted in PubMed, Chinese Scientific Journal Database, and Chinese Biomedical Literature Database from their inception to February 1, 2016. The following keywords were used to search the databases: Toll-like receptors, cancer therapy, therapeutic target, innate immunity. Of 244 studies that were identified, 97 nonrelevant studies were excluded. In total, 147 full-text articles were assessed, and from these, 54 were excluded as they did not provide complete key information. Thus, 93 studies were considered eligible and included in the analysis. According to the data from the included trials, 14 TLR ligands (77.8%) from 82 studies have been demonstrated to display antitumor property in various cancers, whereas 4 ligands (22.2%) from 11 studies promote tumors. Among them, only 3 TLR ligands have been approved for cancer therapy, and 9 ligands were in clinical trials. In addition, the potential mechanism of recently reported targets on TLRs for clinical application was also evaluated in this review. We show that targeting TLRs in cancer immunotherapy is a promising strategy for cancer therapy, and the specific TLR ligands, either alone or combination, exhibit antitumor potential.

Toll-like receptor 4 signaling promotes invasion of hepatocellular carcinoma cells through MKK4/JNK pathway

Toll-like receptor (TLR) 4-mediated signaling has been shown to be important to cell survival, invasion and metastasis in a variety of cancers. The present study aimed to explore the role and downstream pathways of TLR4 signaling in the invasion of hepatocellular carcinoma (HCC) cell lines. We found that LPS, the agonist of TLR4, notably enhanced the invasiveness of HCC cells and the expression of MMP2 and MMP9, as well as the production of IL-6 and TNFα. LPS treatment dramatically increased the TLR4 expression on HCC cells surface and MKK4/JNK activation, while knockdown of TLR4 inhibited the LPS-induced invasion and the phosphorylation of MKK4 and JNK. Furthermore, silencing of MKK4 or inhibition of JNK activity led to impaired invasiveness of HCCs, low expression level of MMPs and TLR4, as well as limited production of cytokines. However, LPS stimulation only triggered moderate activation of NF-кB. Silencing of NF-кB or NF-кB inhibitor had no obvious effect on the invasive ability of HCCs and TLR4 expression, but suppressed IL-6 and TNFα production. These findings suggested that LPS-TLR4 signaling enhanced the invasiveness of HCCs mainly through MKK4/JNK pathway.

Lipopolysaccharide-induced toll-like receptor 4 signaling in cancer cells promotes cell survival and proliferation in hepatocellular carcinoma

BACKGROUND

Recent studies have shown that toll-like receptor 4 (TLR4) is involved in hepatocarcinogenesis. However, the significance of TLR4 signaling in cancer development and progression remains unclear.

AIM

The purpose of this study was to investigate the role of TLR4 in cancer cell survival and proliferation in hepatocellular carcinoma (HCC).

METHODS

Fifty-three HCC and ten normal liver specimens were analyzed by immunohistochemistry, and three cell lines (HL-7702, PLC/PRF/5 and HepG2) were used for in vitro studies. Lipopolysaccharide (LPS), a specific ligand of TLR4, was used to activate TLR4 signaling. The effects of LPS-TLR4 signaling on cell survival, proliferation and invasion were examined. Specific inhibitors of NF-κB and MAPK (JNK, ERK and p38) signaling pathways were used to explore the role of each pathway in LPS-TLR4 signaling.

RESULTS

TLR4 was overexpressed in HCC cell lines and in human HCC tissues, where it correlated with Ki-67 expression. LPS-induced activation of TLR4 signaling promoted cancer cell survival and proliferation. LPS-TLR4 signaling was associated with regulation on the activation of NF-κB and MAPK signaling pathways. LPS-TLR4-induced activation of ERK and JNK signaling promotes cell proliferation through regulating Bax translocation to mitochondria. Activation of NF-κB and p38 mediates cytotoxicity of LPS, and inhibition on these two pathways promotes cell proliferation in HCC cells.

CONCLUSION

Our results indicate that TLR4 signaling in cancer cells promotes cell survival and proliferation in HCC.

Trial Watch: Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) have long been known for their ability to initiate innate immune responses upon exposure to conserved microbial components such as lipopolysaccharide (LPS) and double-stranded RNA. More recently, this family of pattern recognition receptors has been attributed a critical role in the elicitation of anticancer immune responses, raising interest in the development of immunochemotherapeutic regimens based on natural or synthetic TLR agonists. In spite of such an intense wave of preclinical and clinical investigation, only three TLR agonists are currently licensed by FDA for use in cancer patients: bacillus Calmette–Guérin (BCG), an attenuated strain of Mycobacterium bovis that operates as a mixed TLR2/TLR4 agonist; monophosphoryl lipid A (MPL), a derivative of Salmonella minnesota that functions as a potent agonist of TLR4; and imiquimod, a synthetic imidazoquinoline that activates TLR7. One year ago, in the August and September issues of OncoImmunology, we described the main biological features of TLRs and discussed the progress of clinical studies evaluating the safety and therapeutic potential of TLR agonists in cancer patients. Here, we summarize the latest developments in this exciting area of research, focusing on preclinical studies that have been published during the last 13 mo and clinical trials launched in the same period to investigate the antineoplastic activity of TLR agonists.

FAK Inhibition Decreases Hepatoblastoma Survival Both In Vitro and In Vivo

Hepatoblastoma is the most frequently diagnosed liver tumor of childhood, and children with advanced, metastatic or relapsed disease have a disease-free survival rate under 50%. Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase that is important in many facets of tumor development and progression. FAK has been found in other pediatric solid tumors and in adult hepatocellular carcinoma, leading us to hypothesize that FAK would be present in hepatoblastoma and would impact its cellular survival. In the current study, we showed that FAK was present and phosphorylated in human hepatoblastoma tumor specimens. We also examined the effects of FAK inhibition upon hepatoblastoma cells using a number of parallel approaches to block FAK including RNAi and small molecule FAK inhibitors. FAK inhibition resulted in decreased cellular survival, invasion, and migration and increased apoptosis. Further, small molecule inhibition of FAK led to decreased tumor growth in a nude mouse xenograft model of hepatoblastoma. The findings from this study will help to further our understanding of the regulation of hepatoblastoma tumorigenesis and may provide desperately needed novel therapeutic strategies and targets for aggressive, recurrent, or metastatic hepatoblastomas.