Immunotherapy of glioma

In the past decade, immunotherapy has been used more and more in solid tumors, including melanoma, lung cancer, breast cancer, prostate cancer, bladder cancer and kidney cancer, but the treatment of glioblastoma (GBM) has not made a breakthroughAfter more than 40 years of research and exploration, immunotherapy for GBM includes chimeric antigen receptor T cell immunotherapy (car-t), personalized new antigen vaccine, oncolytic virus and immune checkpoint blockingOn the 75th anniversary of the founding of Journal of Neurosurgery, Professor John HSampson of Neurosurgery at Duke University Medical Center in the United States was invited to review the latest experience, development and expected challenges of the above immunotherapy, which was published in Journal of neurosurgery in September 2019< br / > research results < br / > 1Adoptive lymphocyte infusion < br / > this treatment belongs to the passive immunotherapy of tumor, that is to collect the autogenous T cells targeting tumor antigen, activate and expand in vitro, and then infuse them back into the bodyEarly adoptive lymphocytic transfer (ALT) attempts to solve the problem of limited number of tumor specific T cells by providing gene modified T-cell receptor (TCR) - A and - B chainsLater studies focused on two problems: bypassing the restriction of major histocompatibility complex (MHC) and targeting nonprotein antigens, and jointly promoting the development of chimeric antigen receptor (car-t) therapy (Figure 1)< br / > Figure 1Car-t cell therapyT cells transfected with car can recognize tumor cell surface antigens in a MHC independent manner, thus promoting the killing of tumor cells< br / > in GBM, egfrv Ⅲ, il13ra2 or HER2 are the targets of most studies related to car-t cells; the latest fourth generation car integration can over express and enhance the function and / or persistence of cars in vivo, such as IL-15, but whether it has sufficient anti-tumor ability in clinical remains to be seenThe main limitation of car in GBM treatment is tumor heterogeneity (i.etumor cells can express many different antigens), even at the single cell level< br / > one way to deal with tumor heterogeneity is to design cars with multiple specificityAs for scFv targeting HER2 and IL-13 mutant targeting il13ra, the bispecific car and trivalent car targeting HER2, il13ra2 and EphA2 are composedCompared with univalent and bivalent car, trivalent car has superior antitumor activity in the preclinical model of GBM and in vitro co culture with primary human GBM cells Another way to deal with tumor heterogeneity is to endow cars with the ability to induce epitope diffusion and stimulate endogenous tumor specific immunity For example, to design a new car so that it can identify the host antigen-presenting cell (APC) to start endogenous T cells against a variety of unrecognized tumor antigens, so as to avoid antigen loss and variation < br / > 2 Vaccine strategy < br / > at present, most tumor vaccines are used as treatment options after tumor diagnosis and standard treatment failure Cancer vaccines for GBM can be divided into two categories: peptide vaccines and cell-based vaccines (Figure 2) < br / > Figure 2 Vaccine forms used in GBM: peptides, new antigens and DC Synthesis methods for each vaccine form, including tumor total exon sequencing and new antigen identification technology (above) The delivery target of peptide and new antigen vaccines is to be ingested by endogenous DC, while DC vaccines are loaded with antigens in vitro before administration Both vaccines stimulate DC to activate CD8 + and CD4 + T cells to achieve cellular and humoral immune response to tumors (figure below) Copyright is owned by Duke University and released with permission < br / > 1 Peptide vaccine < br / > tumor is characterized by a large number of gene mutations The mutant gene encodes proteins / peptides that can produce antigens that are only expressed in tumors It is called tumor specific antigen (TSA) The newly discovered TSA is called "new antigen" Only a few mutations can be processed into new epitopes, which are presented to human leukocyte antigen (HLA) by APC to induce T cell response Many potential tumor antigens are not derived from mutations, but from normal proteins (TAA) that are still misexpressed or overexpressed in other tissues A common antigen may be a target for the development of an additional autoimmune risk, such as encephalitis Therefore, the relative lack of specific and highly expressed epitopes in GBM is a factor limiting the development of vaccines < br / > at present, egfrv Ⅲ is still the most relevant and undisputed TSA for GBM, which can be found in 20% - 30% of tumors In the late 1990s, a peptide vaccine, rindopepimut (cdx-110), was designed, which showed excellent preclinical efficacy in mouse brain tumor models, including inducing humoral and cytotoxic T cell responses Subsequently, 745 newly diagnosed GBM patients were included in the multi center and double arm phase III clinical trial (act Ⅳ) The patients receiving rindopepimut showed good humoral immune response, but the overall survival (OS) did not improve significantly The results of act Ⅳ were disappointing, which affected the development speed of peptide vaccine targeting egfrv Ⅲ At present, there are still other vaccines targeting egfrv Ⅲ under clinical research, such as adu-623 (Registration No.: nct01967758 clinicaltrial.gov ）。 < br / > isocitrate dehydrogenase (IDH) is a rare and truly homogeneous TSA About 80% of low-grade gliomas have IDH mutations, the most common is r132h mutation in IDH1 (70% of all IDH mutations) In preclinical mouse models, r132h targeted peptides can induce antigen-specific CD4 + T cells and humoral immune responses after presentation of MHC class II (lack of class I epitope) antigens Grade III and IV gliomas mutated in idh1r132h (Registration No.: nct02454634, clinicaltrial.gov ）And recurrent grade II glioma (Registration No.: nct02193347, clinicaltrial.gov ）Phase I clinical trials of peptide vaccines are under way The mutation load of < br / > GBM is relatively low, but the heterogeneity of tumor is still an unavoidable problem, especially when only single target design vaccine treatment can be selected This single target therapy can also cause antigen escape, that is, the tumor no longer expresses the target antigen, leading to treatment failure The primary direction of future development is to identify and combine a variety of new antigen candidates and predict their HLA performance < br / > two recent important trials have highlighted the development of individualized cancer vaccines targeting new antigens In the first study, 7-20 peptide segments were extracted to prepare individualized cancer vaccine by comparing the whole exon sequencing data from excised tumor and matched normal tissue The second study used two new antigens in combination with unmodified TAA to increase the number of activated epitopes These two phase I clinical trials produced a large number of infiltrative tumor reactive T cells with memory phenotype and new antigen specific clone amplification < br / > 2 Cell based vaccine < br / > there are two kinds of cell-based anti-tumor vaccines: tumor cell vaccine and dendritic cell (DC) vaccine Among them, DC vaccine is the most common, its principle is to expand, load and activate the dendritic cells carrying tumor antigens, so as to play the anti-tumor effect Based on this principle, sipuleucel-t vaccine is the first cancer vaccine approved by FDA With regard to glioma, a large number of clinical trials using DC have been published in the United States, Europe and Japan However, there is no phase III clinical research evidence to prove its efficacy, and the process of treatment trial needs a lot of human and financial resources According to the DC vaccine project developed by Linda Liau and his colleagues, DCvax has entered the phase III clinical trial (Registration Number: nct00045968 and nct02146066, clinicaltrials.gov ）, waiting for results At present, there are many phase I and phase II clinical trials (Registration No.: nct00639639, nct02465268 and nct02366728, clinicaltrials.gov ）In order to obtain better effect of lymph node homing and prolong the survival period of patients, we focused on the pretreatment of vaccine sites In the past 30 years, the viral therapy for GBM has been repeated many times, but it has not been completely successful Recent studies have used oncolytic viruses to initiate endogenous secondary immune responses by tumor cell lysis (Figure 3) < br / > Fig 3 Treatment of oncolytic virus PVS-RIPO and other viruses are administered locally, in order to achieve tumor specific uptake or infection The dissolution of tumor cells promotes the release of antigens and camp, thus stimulating the secondary immune response Copyright is owned by Duke University and released with permission < br / > oncolytic virus is usually injected directly into the tumor or placed in the tumor cavity after surgery The goal of treatment is to infect and lyse tumor cells, stimulate the death pathway of immunogenic cells, initiate immune response through damage associated molecular pattern (damp) and TAA / TSA, and recruit immune cells to reach the site In addition to promoting the release of damp, oncolytic virus itself also carries molecular patterns related to pathogens, which can be recognized by the immune system, and is expected to trigger additional attacks on tumor cells < br / > two oncolytic viruses (dnx-2401 and PVS-RIPO) were approved by FDA Dnx-2401 is an adenovirus with replication ability, which limits virus replication by specific mutations The virus contains arginine / glycine / aspartate motif, which can target integrin on GBM, thus increasing the specificity of infection on tumor cells PVS-RIPO is a live attenuated poliovirus vaccine / human rhinovirus chimera with replication ability The virus enters the CD155 cell, which is up-regulated in malignant cells and also expressed in APC In vitro, PVS-RIPO is cytotoxic to tumor cells and promotes chronic, sub lethal infection of APC, which leads to the production of pro-inflammatory cytokines In a phase I study in which 61 patients with grade IV recurrent gliomas received intratumoral injection of PVS-RIPO, the OS rate was 21% at 24 and 36 months In contrast, the OS rate in the historical control group was 14% at 24 months and 4% at 36 months PVS-RIPO is currently undergoing phase II clinical trials < br / > 4 Checkpoint blocking therapy < br / > immune checkpoint is a molecule that activates the surface of T cells, which acts as a "brake" to prevent uncontrolled inflammatory response The signals from CTLA-4 and PD-1, the classical immunocheckpoint, lead to the inactivation and even apoptosis of activated T cells, respectively Blocking or antagonizing immune checkpoint molecules can make T cells continuously activated (Fig 4) < br / > Figure 4 Checkpoint blocking Activated T cells up regulate CTLA-4 and PD-1, which can bind to B7 and PD-L1 on tumor cells, respectively T cell inactivation, failure and even apoptosis are caused by signal transmission through checkpoints Checkpoint blocking therapy includes the administration of antibodies that interfere with the binding of ligands to checkpoints, and the maintenance and prolongation of T cell activation Copyright is owned by Duke University and released with permission < br / > CTLA-4 is an in-depth study of immunocheckpoint receptor Blocking CTLA-4 with drugs such as ipilimumab can increase the utilization of CD28 and enlarge T cell response; since FDA approved the treatment of metastatic melanoma in 2010, it has become a drug for several types of cancer, but its toxicity is limited to GBM Similar to CTLA-4, PD-1 can regulate the immune response under physiological conditions The binding of PD-1 and its ligand PD-L1 reduces TCR signal transduction and the induction of key transcription factors (such as activator protein 1 (AP-1) and activated T cell nuclear factor of activated T cells (NFAT)), leading to the impairment of T cell activation Early trials of anti-PD-1 in the treatment of other cancers have shown that it promotes long-lasting antitumor response, and the FDA has approved nivolumab (anti-PD-1, Bristol