Inhibiting NF-κB/IL-6/STAT3 Pathway To Rescue Antitumor Immunity To Treat Hepatocellular Carcinoma

Hepatocellular carcinoma(HCC)is one of the most aggressive tumors.It is almost refractory to all the existing treatments.The 5-year survival rate is lower than 10%.In recent years,tumor immunotherapy is a hot topic in worldwide,which is a relatively effective treatment against those recurrent or refractory tumors.To HCC,several immunotherapy strategies have shown their efficacy.HCC is one of the inflammation-related tumors.Nuclear factor-kappa B(NF-κB)and signal transducers and activators of transcription(STAT)3 have crucial roles in the development of HCC.The phosphorylated STAT3 is overexpressed on more than half of the HCC tumor samples.The interleukin(IL)6 is often elevated in the serum of the HCC patients.STAT3 mediates tumor immune escape via many mechanisms.Inhibiting STAT3 activation can partially rescue antitumor immunity.IL-6,a cytokine in the downstream of NF-κB,is a key activator of STAT3.Reducing IL-6 expression by inhibiting NF-κB activation is an important way to down-regulate STAT3 phosphorylation,there it is also an important way to relieve the tumor immune evasion.There are two main ways to induce NF-κB activation in tumors.One is the inhibitor of nuclear factor kappa-B kinase(IKK)dependent way,such as tumor necrosis factor(TNF)α,IL-1β and lipopolysaccharide(LPS)induced NF-κB activation.The inhibitor of IKK and the inhibitor of protosome degraduation are used to inhibit this pathway.However,none of them shows the complete and the specific inhibition.It reveals that other regulators may be involved in the activation of NF-κB.Actually,tissue transglutaminase 2(TGase2)is such a NF-κB activator,which mediates tissue NF-κB activation in a IKK-independent way.The inhibitors of TGase2 include BPA,MDC and siRNA,which downregulates the expression of TGase2.Frankincense and myrrh are clinical agents to weaken swell,relieve siltation and inhibit inflammation.Previous studies have shown that single extract of frankincense or myrrh could also inhibit tumor growth by increasing cell apoptosis,inhibiting angiogenesis and reversing drug resistance,which is mediated by inhibition of IKK/NF-κB inhibitor α(IκBα)/NF-κB pathway.It is not clear whether frankincense and myrrh can enhance antitumor immunity by down-regulating NF-κB/IL-6/STAT3.R2 is a synthesized anti-inflammation peptide inhibiting TGase2 activity,thereby inhibiting NF-κB activation.Whether R2 can inhibit tumor immune evasion is unknown.Therefore,in this study,we investigated the effect of NF-κB/IL-6/STAT3 inhibition on antitumor immunity in HCC with these two kinds of different inhibiting NF-κB agents.In addition,the side effect of oncolytic adenovirus(ADV)in clinical practices is the adverse inflammation.Therefore,we constructed the recombinant ADV expressing R2,which could inhibit the inflammation induced by ADV.It is expected to enhance the antitumor immunity induced by ADV and also the safety of ADV application.This study confirmed that frankincense&myrrh and R2 inhibited the activation of NF-κB/IL-6/STAT3 pathway.Both of them inhibited the inflammatory response induced by the oncolysis of immune cells and enhanced the oncolysis effect of immune cells.In the immunity-competent mice,frankincense&myrrh and R2 inhibited the tumor growth and the survival of the tumor-bearing mice.The immunity activity in the tumor microenvironment was rescued.Further,we found that the frankincense&myrrh inhibited the tumor growth in a CD8+T cell dependent way.These results illustrate a new mechanism on how Frankincense&Myrrh inhibits tumors.It also offers a new strategy for tumor immunotherapy.At last,we showed that the expression of pro-inflammatory cytokineswas upregulated by ADV oncolysis.R2 reduced this level while having on effect of the oncolysis effect of ADV.Hence,it offers a chance to enhance the antitumor immunity induce by ADV and also the safety of ADV in clinical application.