Synergy between tumor immunotherapy and antiangiogenic therapy

Von Hippel-Lindau protein signalling in clear cell renal cell carcinoma

The distinct pathological and molecular features of kidney cancer in adaptation to oxygen homeostasis render this malignancy an attractive model for investigating hypoxia signalling and potentially developing potent targeted therapies. Hypoxia signalling has a pivotal role in kidney cancer, particularly within the most prevalent subtype, known as renal cell carcinoma (RCC). Hypoxia promotes various crucial pathological processes, such as hypoxia-inducible factor (HIF) activation, angiogenesis, proliferation, metabolic reprogramming and drug resistance, all of which contribute to kidney cancer development, growth or metastasis formation. A substantial portion of kidney cancers, in particular clear cell RCC (ccRCC), are characterized by a loss of function of Von Hippel-Lindau tumour suppressor (VHL), leading to the accumulation of HIF proteins, especially HIF2α, a crucial driver of ccRCC. Thus, therapeutic strategies targeting pVHL-HIF signalling have been explored in ccRCC, culminating in the successful development of HIF2α-specific antagonists such as belzutifan (PT2977), an FDA-approved drug to treat VHL-associated diseases including advanced-stage ccRCC. An increased understanding of hypoxia signalling in kidney cancer came from the discovery of novel VHL protein (pVHL) targets, and mechanisms of synthetic lethality with VHL mutations. These breakthroughs can pave the way for the development of innovative and potent combination therapies in kidney cancer.

Development and validation of an individualized angiogenesis and tumor-infiltrating lymphocytes prognostic signature in nasopharyngeal carcinoma

In recent years, targeted therapy and immunotherapy have become ideal choices for the treatment of advanced, metastatic, recurrent, and drug-resistant nasopharyngeal carcinoma (NPC), but the lack of understanding of the relationship and mechanism between TILs and angiogenic factors hinders therapeutic development and optimization. In this study, the expression of angiogenesis-related markers (VEGF-A,VEGFR-2) and TILs (CD4+T,CD8+T) was studied by using immunohistochemistry (IHC). Then we constructed an immunohistochemical scoring model for the co-expression of angiogenesis-related markers and TILs (COV+TIL score)in the training (n = 124) and validated the accuracy and reliability of the scoring system in the validation cohorts (n = 114), respectively We established the COV+TIL score model and stratified patients into different risk level in the training cohorts according to COV+TIL score (cut-off value=28). Patients in the high-risk group had worse prognosis in the training cohorts five-year overall survival (OS), progression-free survival (PFS), locoregional relapse-free survival (LRRFS), and distant metastasis-free survival (DMFS) was lower than that of patients in the low-risk group, and this result was validated in the validation cohorts ( 5-year OS in the high-risk and the low-risk group 46.8% vs. 83.4%, HR: 3.42, 95%CI: 1.77-6.61, p < 0.001); ( 5-year PFS 45.9% vs. 81.2%, HR: 3.22, 95%CI: 1.71-6.06, p < 0.001); ( 5-year LRRFS 74.6% vs. 87.5%, HR: 3.22, 95%CI: 1.16-8.93, p = 0.027); and ( 5-year DMFS79.2% vs. 93.2%, HR: 2.22, 95%CI: 0.91-5.39, p = 0.086). Upon multivariable analysis, COV+TIL score emerged as an independent prognostic indicator for defining survival in the training cohorts and the validation cohorts. Combining the COV+TIL score and TNM stage improved the prediction ability of the survival. In conclusion, NPC patients with high COV+TIL score showed worse prognosis.

Combinations of Anti-Angiogenic Agents and Immune Checkpoint Inhibitors in Renal Cell Carcinoma: Best Option?

Over the past decade, major advances have been made in the treatment of advanced and metastatic renal cell carcinomas, specifically clear cell carcinomas. For many years the optimal approach was sequential; thus, monotherapies [principally tyrosine kinase inhibitors (TKIs)] targeting angiogenesis until toxicity or progressive disease developed. The rationale was the common mechanisms of action of the targeting agents and avoidance of the risk of overlapping toxicities. Immune checkpoint inhibitors (ICIs) are effective monotherapies, and combinations thereof with anti-angiogenic agents were thus later considered. Synergistic interactions were reported in vitro. Clinical efficacy was evident in three pivotal phase III trials with axitinib-pembrolizumab, cabozantinib-nivolumab, and lenvatinib-pembrolizumab combinations. Two other combinations showed interesting results but did not improve overall survival. However, the data aided our understanding of the new therapeutic approaches. A combination of the ICIs nivolumab and ipilimumab was the first to evidence better progression-free and overall survival compared to sunitinib in patients with intermediate or unfavourable prognoses as evaluated by the International mRCC Database Consortium (IMDC). Here we focus on the TKI-ICI combinations, emphasising the rationale of their use and the clinical results. To date, no biomarker facilitating the selection of an optimal treatment by disease and patient status has been reported.

The Quest for mRNA Vaccines

The success of mRNA vaccines against COVID-19 is nothing short of a medical revolution. Given its chemical lability the use of mRNA as a therapeutic has been counterintuitive and met with skepticism. The development of mRNA-based COVID-19 vaccines was the culmination of long and painstaking efforts by many investigators spanning over 30 years and culminating with the seminal studies of Kariko and Weissman. This review will describe one chapter in this saga, studies that have shown that mRNA can function as a therapeutic. It started with our seminal observation that dendritic cells (DCs) transfected with mRNA in vitro administered to mice inhibits tumor growth, and led to first-in-human clinical trials with mRNA vaccines in cancer patients. The clinical development of this patient-specific DCs-mRNA approach and use on a larger scale was hindered by the challenges associated with personalized cell therapies. Confirmed and extended by many investigators, these studies did serve as impetus and motivation that led scientists to persevere, eventually leading to the development of simple, broadly applicable, and highly effective protocols of directly injecting mRNA into patients, culminating in the COVID-19 mRNA vaccines.

Anti-tumor effects of vascular endothelial growth factor/vascular endothelial growth factor receptor binding domain-modified chimeric antigen receptor T cells

BACKGROUND AIMS

The vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor (VEGFR) signaling pathway plays an important role in angiogenesis and lymphangiogenesis, which are closely related to tumor cell growth, survival, tissue infiltration and metastasis. Blocking/interfering with the interaction between VEGF and VEGFR to inhibit angiogenesis/lymphangiogenesis has become an important means of tumor therapy.

METHODS

Here the authors designed a novel chimeric antigen receptor (CAR) lentiviral vector expressing the VEGF-C domain targeting both VEGFR-2 and VEGFR-3 (VEGFR-2/3 CAR) and then transduced CD3-positive T cells with VEGFR-2/3 CAR lentivirus.

RESULTS

After co-culturing with target cells, VEGFR-2/3 CAR T cells showed potent cytotoxicity against both VEGFR-2- and VEGFR-3-positive breast cancer cells, with increased simultaneous secretion of interferon gamma, tumor necrosis factor alpha and interleukin-2 cytokines. Moreover, CAR T cells were able to destroy the tubular structures formed by human umbilical vein endothelial cells and significantly inhibit the growth, infiltration and metastasis of orthotopic mammary xenograft tumors in a female BALB/c nude mice model.

CONCLUSIONS

The authors' results indicate that VEGFR-2/3 CAR T cells targeting both VEGFR-2 and VEGFR-3 have significant anti-tumor activity, which expands the application of conventional CAR T-cell therapy.

Targeting the SHP2 phosphatase promotes vascular damage and inhibition of tumor growth

The tyrosine phosphatase SHP2 is oncogenic in cancers driven by receptor-tyrosine-kinases, and SHP2 inhibition reduces tumor growth. Here, we report that SHP2 is an essential promoter of endothelial cell survival and growth in the remodeling tumor vasculature. Using genetic and chemical approaches to inhibit SHP2 activity in endothelial cells, we show that SHP2 inhibits pro-apoptotic STAT3 and stimulates proliferative ERK1/2 signaling. Systemic SHP2 inhibition in mice bearing tumor types selected for SHP2-independent tumor cell growth promotes degeneration of the tumor vasculature and blood extravasation; reduces tumor vascularity and blood perfusion; and increases tumor necrosis. Reduction of tumor growth ensues, independent of SHP2 targeting in the tumor cells, blocking immune checkpoints, or recruiting macrophages. We also show that inhibiting the Angiopoietin/TIE2/AKT cascade magnifies the vascular and anti-tumor effects of SHP2 inhibition by blocking tumor endothelial AKT signaling, not a target of SHP2. Since the SHP2 and Ang2/TIE2 pathways are active in vascular endothelial cells of human melanoma and colon carcinoma, SHP2 inhibitors alone or with Ang2/TIE2 inhibitors hold promise to effectively target the tumor endothelium.

A Phase I/II Study to Assess the Safety and Efficacy of Pazopanib and Pembrolizumab Combination Therapy in Patients with Advanced Renal Cell Carcinoma

BACKGROUND

This study assessed whether antiangiogenic treatment may potentiate immune checkpoint blockade in patients with advanced renal cell carcinoma.

PATIENTS AND METHODS

This was an open-label, two-part, multicenter study involving treatment-naïve patients with advanced renal cell carcinoma. Part 1 consisted of a phase I dose escalation and expansion of pazopanib plus pembrolizumab (combination therapy). Cohorts A and B received pazopanib in combination with pembrolizumab, whereas Cohort C received pazopanib monotherapy for 9 weeks before receiving the combination therapy. Part 2 was planned as a randomized three-arm study but was not conducted.

RESULTS

Overall, 42 patients were enrolled (10 each in Cohorts A and B, 22 in Cohort C). The maximum tolerated dose was not reached and the recommended phase II dose was not declared, as Cohort C was closed early because of safety concerns. The overall response rates were 60% and 20% in Cohorts A and B, respectively. In Cohort C, the overall response rates were 33%, 25%, and 0% in the combination therapy, pembrolizumab monotherapy, and pazopanib monotherapy groups, respectively. The median progression-free survival rates were 21.95 months and 41.40 months in Cohorts A and B, respectively. Grade 3 or 4 adverse events (AEs) were observed in 90% of patients in Cohorts A and B. In Cohort C, the frequencies of grade 3 or 4 AEs, serious adverse events, and AEs leading to dose reduction were typically high in the combination therapy group.

CONCLUSIONS

Despite preliminary signs of efficacy, significant hepatotoxicity was observed in Cohorts A and B. The sequential schedule of pazopanib followed by pazopanib plus pembrolizumab showed reduced hepatotoxicity; however, other safety issues emerged with this approach.

Synergistic Effect of α-Solanine and Cisplatin Induces Apoptosis and Enhances Cell Cycle Arrest in Human Hepatocellular Carcinoma Cells

AIM

The clinical application of cisplatin is limited by severe side effects associated with high applied doses. The synergistic effect of a combination treatment of a low dose of cisplatin with the natural alkaloid α-solanine on human hepatocellular carcinoma cells was evaluated.

METHODS

HepG2 cells were exposed to low doses of α-solanine and cisplatin, either independently or in combination. The efficiency of this treatment modality was evaluated by investigating cell growth inhibition, cell cycle arrest, and apoptosis enhancement.

RESULTS

α-solanine synergistically potentiated the effect of cisplatin on cell growth inhibition and significantly induced apoptosis. This synergistic effect was mediated by inducing cell cycle arrest at the G2/M phase, enhancing DNA fragmentation and increasing apoptosis through the activation of caspase 3/7 and/or elevating the expression of the death receptors DR4 and DR5. The induced apoptosis from this combination treatment was also mediated by reducing the expression of the anti-apoptotic mediators Bcl-2 and survivin, as well as by modulating the miR-21 expression.

CONCLUSION

Our study provides strong evidence that a combination treatment of low doses of α-solanine and cisplatin exerts a synergistic anticancer effect and provides an effective treatment strategy against hepatocellular carcinoma.

Inhibiting Autophagy in Renal Cell Cancer and the Associated Tumor Endothelium

The clear cell subtype of kidney cancer encompasses most renal cell carcinoma cases and is associated with the loss of von Hippel-Lindau gene function or expression. Subsequent loss or mutation of the other allele influences cellular stress responses involving nutrient and hypoxia sensing. Autophagy is an important regulatory process promoting the disposal of unnecessary or degraded cellular components, tightly linked to almost all cellular processes. Organelles and proteins that become damaged or that are no longer needed in the cell are sequestered and digested in autophagosomes upon fusing with lysosomes, or alternatively, released via vesicular exocytosis. Tumor development tends to disrupt the regulation of the balance between this process and apoptosis, permitting prolonged cell survival and increased replication. Completed trials of autophagic inhibitors using hydroxychloroquine in combination with other anticancer agents including rapalogues and high-dose interleukin 2 have now been reported. The complex nature of autophagy and the unique biology of clear cell renal cell carcinoma warrant further understanding to better develop the next generation of relevant anticancer agents.

Synergic effect of PD-1 blockade and endostar on the PI3K/AKT/mTOR-mediated autophagy and angiogenesis in Lewis lung carcinoma mouse model

BACKGROUND

Immunotherapy has been shown to be effective as a first-line treatment option for non-small cell lung cancer (NSCLC) patients. Unfortunately, it has failed to acquire an anticipant anti-tumour effect for relatively lower clinical benefit rates. It is therefore important to identify novel strategies for improving immunotherapy. Endostar is a novel recombinant human endostatin that exerts its anti-angiogenic effects via vascular endothelial growth factor (VEGF)-related signalling pathways. Anti-programmed death receptor 1 (PD-1) antibody is an immune checkpoint inhibitor that was developed to stimulate the immune system. In this study, the synergy of PD-1 blockade and endostar was assessed in a lung carcinoma mouse model.

METHODS

Lewis lung carcinoma (LLC)-bearing mice were randomly assigned into three groups: controls, anti-PD-1 and anti-PD-1+endostar. The levels of cytokines such as interleukin (IL)-17, transforming growth factor-β1 (TGF-β1) and interferon-γ (IFN-γ) were measured with enzyme-linked immune sorbent assay (ELISA). The expression of VEGF, CD34 and CD31 was assessed with immunohistochemistry (IHC). The proportion of mature dendritic cells (mDC) and myeloid-derived suppressor cells (MDSC) was analysed with flow cytometry. The major proteins in PI3K/AKT/mTOR and autophagy were quantified with Western blot.

RESULTS

Anti-PD-1 combined with endostar dramatically suppressed tumour growth in LLC mouse models. This synergistic effect resulted in decreased pro-inflammatory cytokine IL-17 and immunosuppressive factor TGF-β1 levels, increased IFN-γ secretion, reduced myeloid-derived suppressor cell (MDSC) accumulation, and reversed CD8 + T cell suppression. The expression of VEGF, CD34 and CD31 was significantly down-regulated, while tumour cell apoptosis and PI3K/AKT/mTOR-mediated autophagy was up-regulated.

CONCLUSION

The combination of anti-PD-1 and endostar has a remarkably synergic effect on LLC tumour growth by means of improving the tumour microenvironment and activating autophagy.

Checkpoint inhibitor immunotherapy in kidney cancer

Kidney cancer has unique features that make this malignancy attractive for therapeutic approaches that target components of the immune system. Immune checkpoint inhibition is a well-established part of kidney cancer treatment, and rapid advances continue to be made in this field. Initial preclinical studies that elucidated the biology of the programmed cell death 1 (PD-1), programmed cell death 1 ligand 1 (PD-L1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) immune checkpoints led to a series of clinical trials that resulted in regulatory approval of nivolumab and the combination of ipilimumab plus nivolumab for the treatment of advanced renal cell carcinoma. Subsequent data led to approvals of combination strategies of immune checkpoint inhibition plus agents that target the vascular endothelial growth factor receptor and a shift in the current standard of renal cell carcinoma care. However, controversies remain regarding the optimal therapy selection and treatment strategy for individual patients, which might be eventually overcome by current intensive efforts in biomarker research. That work includes evaluation of tumour cell PD-L1 expression, gene expression signatures, CD8⁺ T cell density and others. In the future, further advances in the understanding of immune checkpoint biology might reveal new therapeutic targets beyond PD-1, PD-L1 and CTLA-4, as well as new combination approaches.

Ribonucleic Acid Engineering of Dendritic Cells for Therapeutic Vaccination: Ready 'N Able to Improve Clinical Outcome?

Targeting and exploiting the immune system has become a valid alternative to conventional options for treating cancer and infectious disease. Dendritic cells (DCs) take a central place given their role as key orchestrators of immunity. Therapeutic vaccination with autologous DCs aims to stimulate the patient's own immune system to specifically target his/her disease and has proven to be an effective form of immunotherapy with very little toxicity. A great amount of research in this field has concentrated on engineering these DCs through ribonucleic acid (RNA) to improve vaccine efficacy and thereby the historically low response rates. We reviewed in depth the 52 clinical trials that have been published on RNA-engineered DC vaccination, spanning from 2001 to date and reporting on 696 different vaccinated patients. While ambiguity prevents reliable quantification of effects, these trials do provide evidence that RNA-modified DC vaccination can induce objective clinical responses and survival benefit in cancer patients through stimulation of anti-cancer immunity, without significant toxicity. Succinct background knowledge of RNA engineering strategies and concise conclusions from available clinical and recent preclinical evidence will help guide future research in the larger domain of DC immunotherapy.

Identification of Target Associations for Polypharmacology from Analysis of Crystallographic Ligands of the Protein Data Bank

The design of a chemical entity that potently and selectively binds to a biological target of therapeutic relevance has dominated the scene of drug discovery so far. However, recent findings suggest that multitarget ligands may be endowed with superior efficacy and be less prone to drug resistance. The Protein Data Bank (PDB) provides experimentally validated structural information about targets and bound ligands. Therefore, it represents a valuable source of information to help identifying active sites, understanding pharmacophore requirements, designing novel ligands, and inferring structure-activity relationships. In this study, we performed a large-scale analysis of the PDB by integrating different ligand-based and structure-based approaches, with the aim of identifying promising target associations for polypharmacology based on reported crystal structure information. First, the 2D and 3D similarity profiles of the crystallographic ligands were evaluated using different ligand-based methods. Then, activity data of pairs of similar ligands binding to different targets were inspected by comparing structural information with bioactivity annotations reported in the ChEMBL, BindingDB, BindingMOAD, and PDBbind databases. Afterward, extensive docking screenings of ligands in the identified cross-targets were made in order to validate and refine the ligand-based results. Finally, the therapeutic relevance of the identified target combinations for polypharmacology was evaluated from comparison with information on therapeutic targets reported in the Therapeutic Target Database (TTD). The results led to the identification of several target associations with high therapeutic potential for polypharmacology.

In vivo tumor-suppressing and anti-angiogenic activities of a recombinant anti-CD3ε nanobody in breast cancer mice model

Aim: Achievements in cancer immunotherapy require augmentation of a host's anti-tumor immune response for anti-cancer modality. Materials & methods: Different concentrations of recombinant anti-CD3 nanobody were administered at predetermined time intervals during a 24-day treatment period and then expression of angiogenic biomarkers including VEGFR2, MMP9 and CD31, as well as tumor cell proliferation marker ki67, was determined in tumor sections by immunohistochemistry. Furthermore, expression of cytokines was examined in peripheral blood of mice. Results: Based on our results, administration of nanobody could reduce biomarker expression in tumor sections. Tumor growth was also delayed and survival rate was increased in response to nanobody treatment. Moreover, expression of pro-inflammatory cytokines was reduced. Conclusion: In conclusion, we demonstrated that administration of nanobody could effectively suppress angiogenesis as well as tumor growth.

DOX/IL-2/IFN-γ co-loaded thermo-sensitive polypeptide hydrogel for efficient melanoma treatment

Melanoma has been a serious threat to the human health; however, effective therapeutic methods of this cancer are still limited. Combined local therapy is a crucial approach for achieving a superior anti-tumor efficacy. In this paper, a chemo-immunotherapy system of DOX, IL-2 and IFN-γ based on poly(γ-ethyl-L-glutamate)-poly(ethylene glycol)-poly(γ-ethyl-L-glutamate) (PELG-PEG-PELG) hydrogel was developed for local treatment of melanoma xenograft. The drug release process of this system exhibited a short term of burst release (the first 3 days), followed by a long-term sustained release (the following 26 days). The hydrogel degraded completely within 3 weeks without obvious inflammatory responses in the subcutaneous layer of rats, showing a good biodegradability and biocompatibility. The DOX/IL-2/IFN-γ co-loaded hydrogel also showed enhanced anti-tumor effect against B16F10 cells in vitro, through increasing the ratio of cell apoptosis and G2/S phage cycle arrest. Moreover, the combined strategy presented improved therapy efficacy against B16F10 melanoma xenograft without obvious systemic side effects in a nude mice model, which was likely related to both the enhanced tumor cell apoptosis and the increased proliferation of the CD3⁺/CD4⁺ T-lymphocytes and CD3⁺/CD8⁺ T-lymphocytes. Overall, the strategy of localized co-delivery of DOX/IL-2/IFN-γ using the polypeptide hydrogel provided a promising approach for efficient melanoma therapy.

•

A chemo-immunotherapy combined system based on polypeptide hydrogel was developed for the local therapy of melanoma.

•

The combined strategy presented enhanced anti-tumor effect on B16F10 cells in vitro through different mechanisms.

•

The combined treatment showed improved efficacy against B16F10 melanoma xenograft with less systemic toxicity in vivo.

Cancer immunotherapy with recombinant poliovirus induces IFN-dominant activation of dendritic cells and tumor antigen-specific CTLs

Tumors thrive in an immunosuppressive microenvironment that impedes antitumor innate and adaptive immune responses. Thus, approaches that can overcome immunosuppression and engage antitumor immunity are needed. This study defines the adjuvant and cancer immunotherapy potential of the recombinant poliovirus/rhinovirus chimera PVSRIPO. PVSRIPO is currently in clinical trials against recurrent World Health Organization grade IV malignant glioma, a notoriously treatment-refractory cancer. Cytopathogenic infection of neoplastic cells releases the proteome and exposes pathogen- and damage-associated molecular patterns. At the same time, sublethal infection of antigen-presenting cells, such as dendritic cells and macrophages, yields potent, sustained type I interferon-dominant activation in an immunosuppressed microenvironment and promotes the development of tumor antigen-specific T cell responses in vitro and antitumor immunity in vivo. PVSRIPO's immune adjuvancy stimulates canonical innate anti-pathogen inflammatory responses within the tumor microenvironment that culminate in dendritic cell and T cell infiltration. Our findings provide mechanistic evidence that PVSRIPO functions as a potent intratumor immune adjuvant that generates tumor antigen-specific cytotoxic T lymphocyte responses.

Immunotherapeutic Targeting of Tumor-Associated Blood Vessels

Pathological angiogenesis occurs during tumor progression and leads in the formation of an abnormal vasculature in the tumor microenvironment (TME). The tumor vasculature is disorganized, tortuous and leaky, resulting in high interstitial pressure and hypoxia in the TME, all of which are events that support tumor growth and survival. Given the sustaining role of the tumor vasculature, it has become an increasingly attractive target for the development of anti-cancer therapies. Antibodies, tyrosine kinase inhibitors and cancer vaccines that target pro-angiogenic factors, angiogenesis-associated receptors or tumor blood vessel-associated antigens continue to be developed and tested for therapeutic efficacy. Preferred anti-angiogenic protocols include those that "normalize" the tumor-associated vasculature which reduce hypoxia and improve tumor blood perfusion, resulting in tumor cell apoptosis, decreased immunosuppression, and enhanced effector immune cell infiltration/tumoricidal action within the TME.

Human cellular CYBA UTR sequences increase mRNA translation without affecting the half-life of recombinant RNA transcripts

Modified nucleotide chemistries that increase the half-life (T1/2) of transfected recombinant mRNA and the use of non-native 5'- and 3'-untranslated region (UTR) sequences that enhance protein translation are advancing the prospects of transcript therapy. To this end, a set of UTR sequences that are present in mRNAs with long cellular T1/2 were synthesized and cloned as five different recombinant sequence set combinations as upstream 5'-UTR and/or downstream 3'-UTR regions flanking a reporter gene. Initial screening in two different cell systems in vitro revealed that cytochrome b-245 alpha chain (CYBA) combinations performed the best among all other UTR combinations and were characterized in detail. The presence or absence of CYBA UTRs had no impact on the mRNA stability of transfected mRNAs, but appeared to enhance the productivity of transfected transcripts based on the measurement of mRNA and protein levels in cells. When CYBA UTRs were fused to human bone morphogenetic protein 2 (hBMP2) coding sequence, the recombinant mRNA transcripts upon transfection produced higher levels of protein as compared to control transcripts. Moreover, transfection of human adipose mesenchymal stem cells with recombinant hBMP2-CYBA UTR transcripts induced bone differentiation demonstrating the osteogenic and therapeutic potential for transcript therapy based on hybrid UTR designs.

Endostatin enhances antitumor effect of tumor antigen-pulsed dendritic cell therapy in mouse xenograft model of lung carcinoma

Objective

To investigate the antitumor effect of endostatin combined with tumor antigen-pulsed dendritic cell (DC)-T cell therapy on lung cancer.

Methods

Transplanted Lewis lung cancer (LLC) models of C57BL/6 mice were established by subcutaneous injection of LLC cells in left extremity axillary. Tumor antigen-pulsed DC-T cells from spleen cells and bone of mice were cultured in vitro. Tumor-bearing mice were randomly divided into three groups, including DC-T+endostatin group, DC-T group, and phosphate-buffered saline (PBS) control group. Microvessel density (MVD) of tumor tissue in tumor-bearing mice was determined by immunohistochemistry (IHC). The expressions of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) were determined by Western blotting and IHC staining. The proportions of CD8+ T cells, mature dendritic cells (mDC), tumor-associated macrophages [TAM (M1/M2)], and myeloid-derived suppressor cells (MDSC) in suspended cells of tumor tissue were determined by flow cytometry. The expressions of interleukin (IL)-6, IL-10, IL-17, transforming growth factor-β (TGF-β) and interferon-γ (IFN-γ) in suspended cells of tumor tissue were detected by enzyme-linked immune sorbent assay (ELISA).

Results

DC-T cells combined with endostatin remarkably suppressed tumor growth. MVD of mice in DC-T+endostatin group was significantly lower than that of the control group and DC-T monotherapy group. The expressions of VEGF, IL-6 and IL-17 in tumors were markedly decreased, but IFN-γ and HIF-1α increased after treating with DC-T cells combined with endostatin, compared to control group and DC-T group. In the DC-T+endostatin group, the proportions of MDSC and TAM (M2 type) were significantly decreased, mDC and TAM (M1 type) were up-regulated, and CD8+ T cells were recruited to infiltrate tumors, in contrast to PBS control and DC-T monotherapy. DC-T cells combined with endostatin potently reduced the expressions of IL-6, IL-10, TGF-β and IL-17 in tumor tissue, and enhanced the expression of IFN-γ.

Conclusions

The study indicated the synergic antitumor effects between endostatin and tumor antigen-pulsed DC-T cells, which may be a prospective therapy strategy to achieve potent antitumor effects on lung cancer.

Pharmacogenomics: Biomarker-Directed Therapy for Bladder Cancer

The clinical management of bladder cancer has seen little change over the last three decades and there is pressing need to identify more effective treatments for advanced disease. Low clinical use of neoadjuvant therapies stems from historical limitations in the ability to predict patients most likely to respond to combination chemotherapies. This article focuses on recent molecular and genetic studies, highlighting promising clinical trials and retrospective studies, and discusses emerging trials that use predictive biomarkers to match patients with therapies to which they are most likely to respond. The implementation of predictive genomic and molecular biomarkers will revolutionize urologic oncology and the clinical management of bladder cancer.

Synergistic antitumor efficacy of combined DNA vaccines targeting tumor cells and angiogenesis

To further enhance the antitumor efficacy of DNA vaccine, we proposed a synergistic strategy that targeted tumor cells and angiogenesis simultaneously. In this study, a Semliki Forest Virus (SFV) replicon DNA vaccine expressing 1-4 domains of murine VEGFR2 and IL12 was constructed, and was named pSVK-VEGFR2-GFc-IL12 (CAVE). The expression of VEGFR2 antigen and IL12 adjuvant molecule in 293T cells in vitro were verified by western blot and enzyme-linked immune sorbent assay (ELISA). Then CAVE was co-immunized with CAVA, a SFV replicon DNA vaccine targeting survivin and β-hCG antigens constructed previously. The antitumor efficacy of our combined replicon vaccines was evaluated in mice model and the possible mechanism was further investigated. The combined vaccines could elicit efficient humoral and cellular immune responses against survivin, β-hCG and VEGFR2 simultaneously. Compared with CAVE or CAVA vaccine alone, the combined vaccines inhibited the tumor growth and improved the survival rate in B16 melanoma mice model more effectively. Furthermore, the intratumoral microvessel density was lowest in combined vaccines group than CAVE or CAVA alone group. Therefore, this synergistic strategy of DNA vaccines for tumor treatment results in an increased antitumor efficacy, and may be more suitable for translation to future research and clinic.

Mannan-modified adenovirus targeting TERT and VEGFR-2: A universal tumour vaccine

Antigen-presenting cells including dendritic cells (DCs) express mannan receptors (MR) on their surface, which can be exploited in cancer therapy by designing immune-stimulatory viruses coated with mannan-modified capsids that then bind to DCs and initiate a potent immune response. Although the combination of anti-angiogenesis and cancer immunotherapy agents has a synergistic antitumor effect, more effective strategies for delivering such combinations are still required. Here we report the design and application of mannan-modified adenovirus that expresses both telomerase reverse transcriptase (TERT) and vascular endothelial growth factor receptor-2 (VEGFR-2). Cytotoxic T lymphocytes that are reactive to TERT and VEGFR-2 are capable of mounting an anti-tumour response in murine breast and colon tumour models and in a lung metastatic model. Compared with mannan-modified TERT adenovirus vaccine or mannan-modified VEGFR-2 adenovirus vaccine alone, the combined vaccine showed remarkably synergistic anti-tumour immunity in these models. Both TERT- and VEGFR-2-specific cytotoxic T lymphocytes (CTL) were identified in an in vitro cytotoxicity assay, and the CTL activity against tumour cells was significantly elevated in the combined vaccine group. Furthermore, CTL-mediated toxicity was blocked by anti-CD8 monoclonal antibodies. Thus, the combined mannan-modified TERT and VEGFR-2 adenovirus confers potent anti-tumour immunity by targeting both tumour cells and intratumoural angiogenesis.

Anti-metastatic effects of DNA vaccine encoding single-chain trimer composed of MHC I and vascular endothelial growth factor receptor 2 peptide

Vascular endothelial growth factor receptor 2 (VEGFR2)-mediated signaling is the key rate-limiting step in angiogenesis. VEGFR2 serves as the most important target of anti-angiogenic therapy for cancers. Single-chain trimer (SCT) comprising antigen peptide, β2-microglobulin (β2m), and major histocompatibility complex (MHC) class I heavy chain was a particularly powerful strategy involved in the increase of the potency of DNA vaccine against tumors and infections. In the present study, we constructed an SCT-encoding VEGFR2 antigen peptide [aa400-408, also known as kinase insert domain-containing receptor (KDR2)], β2m, and mouse MHC class I heavy chain H-2Db [pcDNA3.1(+)-KDR2-β2m-H-2Db, or SCT-KDR2]. The constructed SCT-KDR2 DNA was efficiently expressed in the human A293 embryonic kidney cell line. Intradermal immunization of C57BL/6 mice with SCT-KDR2 DNA was able to successfully break self-immunological tolerance and induce robust cytotoxic T‑lymphocyte (CTL) response to VEGFR2, leading to marked suppression of tumor cell‑induced angiogenesis and metastasis in murine models of B16 melanoma and 3LL Lewis lung carcinoma. Taken together, the results showed that VEGFR2-targeted SCT vaccination is an effective modality that can be utilized in anti-angiogenic active immunotherapy for various types of cancer.

Vaccination approach to anti-angiogenic treatment of cancer

Improvement of patient survival by anti-angiogenic therapy has proven limited. A vaccination approach inducing an immune response against the tumor vasculature combines the benefits of immunotherapy and anti-angiogenesis, and may overcome the limitations of current anti-angiogenic drugs. Strategies to use whole endothelial cell vaccines and DNA- or protein vaccines against key players in the VEGF signaling axis, as well as specific markers of tumor endothelial cells, have been tested in preclinical studies. Current clinical trials are now testing the promise of this specific anti-cancer vaccination approach. This review will highlight the state-of-the-art in this exciting field of cancer research.

Combined vaccination with HER-2 peptide followed by therapy with VEGF peptide mimics exerts effective anti-tumor and anti-angiogenic effects in vitro and in vivo

Overexpression of HER-2 and VEGF plays a key role in the development and metastasis of several human cancers. Many FDA-approved therapies targeting both HER-2 (Trastuzumab, Herceptin) and VEGF (Bevacizumab, Avastin) are expensive, have unacceptable toxicities and are often associated with the development of resistance. Here, we evaluate the dual antitumor effects of combining designed particular HER-2 peptide vaccine with VEGF peptide mimics. In vitro, HER-2 phosphorylation and antibody-dependent cellular toxicity were used to validate whether combining HER-2- and VEGF-targeting therapies would be effective. Moreover, a two-pronged approach was tested in vivo: (1) active immunotherapy with conformational HER-2 B-cell epitope vaccines and (2) anti-angiogenic therapy with a peptide structured to mimic VEGF. A transplantable BALB/c mouse model challenged with TUBO cells was used to test the effects of the HER-2 peptide vaccine combined with VEGF peptide mimics. Tumor sections after treatment were stained for blood vessel density and actively dividing cells. Our results show that immunization with an HER-2 peptide epitope elicits high affinity HER-2 native antibodies that are effective in inhibiting tumor growth in vivo, an effect that is enhanced by VEGF peptide mimics. We demonstrate that the combination of HER-2 and VEGF peptides induces potent anti-tumor and anti-angiogenic responses.

Relationship of angiogenic and apoptotic activities in soft-tissue sarcoma

INTRODUCTION

Angiogenesis and apoptosis play an essential role in tumor development and progression. Previous studies on apoptosis and angiogenesis of soft-tissue sarcoma (STS) were done separately. This is the first study of the relationship between apoptotic and angiogenic activity. Correlation of expression of anti-apoptotic protein (Bcl-2) and pro-apoptotic protein (Bax) in the tumor cells (TCs) with their expression in endothelial cell (EC) of the tumor blood vessels in STS were also carried out.

MATERIALS AND METHODS

101 cases of STS; consisting liposarcoma, malignant fibrous histiocytoma, synovial sarcoma, fibrosarcoma, leiomyosarcoma, rhabdomyosarcoma and malignant peripheral nerve sheath tumor; were collected and immunohistochemical reaction of vascular endothelial growth factor (VEGF), Bcl-2 and Bax were examined.

RESULTS

Higher Bax expression in TCs (54.5%) was seen compared to Bcl-2 expression (44.6%). There was a significant association between Bcl-2 and Bax in TCs with ECs. Significant association was also seen between histological types of STS with Bcl-2 expression; however not with Bax expression. There was an association between VEGF and Bax with high VEGF expression and weak Bax expression. However, VEGF expression was not associated with Bcl-2 expression and histological types.

CONCLUSION

This study supports the role of ECs of tumor blood vessels and apoptosis of TCs in tumor management. Increased angiogenesis may inhibit apoptosis of TCs and lead to tumor growth. Therefore, inhibition of ECs survival or activation of ECs death is promising prospect for tumor therapy. Immunohistochemical antibodies in this study might be potential useful marker for the prognosis of STS.

Mannan-modified adenovirus encoding VEGFR-2 as a vaccine to induce anti-tumor immunity

PURPOSE

Dendritic cell (DC) vaccines are a promising immunotherapeutic approach for treatment and prevention of cancer. While this methodology is widely accepted, it also has some limitations. Antigen-presenting cells including DCs express the mannan receptor (MR). The delivery of a mannan-modified tumor antigen to the MR has been demonstrated to be efficient. Vascular endothelial growth factor receptor-2 (VEGFR-2) is mainly responsible for angiogenesis and tumor growth. The goal of our study was to deliver VEGFR-2 to DCs by means of mannan-modified adenovirus.

METHODS

VEGFR-2 recombinant adenovirus modified with oxidized mannan was constructed as a tumor vaccine to immunize mice in vivo. IFN-γ in mouse sera and spleen was detected by ELISA and ELISPOT. The killing activity of cytotoxic T lymphocyte (CTL) against VEGFR-2 was measured with a lactate dehydrogenase assay. Vessel densities in tumor tissues were detected by immunohistochemistry. Flow cytometry was used to test CD4(+) and CD8(+) T-cell counts in tumor tissues.

RESULTS

The vaccine exhibited both protective and therapeutic efficacy in the inhibition of tumor growth and markedly prolonged survival in mice. Protection against metastasis was also observed. Furthermore, vaccination led to greater IFN-γ and VEGFR-2-specific CTLs. The specific immunity resulted in the suppression of angiogenesis and an increase in CD8(+) cells in tumor tissues.

CONCLUSION

Oxidized mannan-modified adenovirus expressing VEGFR-2 could extraordinarily stimulate both protective and therapeutic immune response in a mice model. Our data suggest that the combination of cancer immunity and anti-angiogenesis via modified mannan is a promising strategy in tumor prophylaxis and therapy.

Deciphering and reversing tumor immune suppression

Generating an anti-tumor immune response is a multi-step process that is executed by effector T cells that can recognize and kill tumor targets. However, tumors employ multiple strategies to attenuate the effectiveness of T-cell-mediated attack. They achieve this by interfering with nearly every step required for effective immunity, from deregulation of antigen-presenting cells to establishment of a physical barrier at the vasculature that prevents homing of effector tumor-rejecting cells and the suppression of effector lymphocytes through the recruitment and activation of immunosuppressive cells such as myeloid-derived suppressor cells, tolerogenic monocytes, and T regulatory cells. Here, we review the ways in which tumors exert immune suppression and highlight the new therapies that seek to reverse this phenomenon and promote anti-tumor immunity. Understanding anti-tumor immunity, and how it becomes disabled by tumors, will ultimately lead to improved immune therapies and prolonged survival of patients.

Deciphering and reversing tumor immune suppression

Generating an anti-tumor immune response is a multi-step process that is executed by effector T cells that can recognize and kill tumor targets. However, tumors employ multiple strategies to attenuate the effectiveness of T-cell-mediated attack. They achieve this by interfering with nearly every step required for effective immunity, from deregulation of antigen-presenting cells to establishment of a physical barrier at the vasculature that prevents homing of effector tumor-rejecting cells and the suppression of effector lymphocytes through the recruitment and activation of immunosuppressive cells such as myeloid-derived suppressor cells, tolerogenic monocytes, and T regulatory cells. Here, we review the ways in which tumors exert immune suppression and highlight the new therapies that seek to reverse this phenomenon and promote anti-tumor immunity. Understanding anti-tumor immunity, and how it becomes disabled by tumors, will ultimately lead to improved immune therapies and prolonged survival of patients.

A Phase I vaccine trial using dendritic cells pulsed with autologous oxidized lysate for recurrent ovarian cancer

Purpose

Ovarian cancer, like most solid tumors, is in dire need of effective therapies. The significance of this trial lies in its promise to spearhead the development of combination immunotherapy and to introduce novel approaches to therapeutic immunomodulation, which could enable otherwise ineffective vaccines to achieve clinical efficacy.

Rationale

Tumor-infiltrating T cells have been associated with improved outcome in ovarian cancer, suggesting that activation of antitumor immunity will improve survival. However, molecularly defined vaccines have been generally disappointing. Cancer vaccines elicit a modest frequency of low-to-moderate avidity tumor-specific T-cells, but powerful tumor barriers dampen the engraftment, expansion and function of these effector T-cells in the tumor, thus preventing them from reaching their full therapeutic potential. Our work has identified two important barriers in the tumor microenvironment: the blood-tumor barrier, which prevents homing of effector T cells, and T regulatory cells, which inactivate effector T cells. We hypothesize that cancer vaccine therapy will benefit from combinations that attenuate these two barrier mechanisms.

Design

We propose a three-cohort sequential study to investigate a combinatorial approach of a new dendritic cell (DC) vaccine pulsed with autologous whole tumor oxidized lysate, in combination with antiangiogenesis therapy (bevacizumab) and metronomic cyclophosphamide, which impacts Treg cells.

Innovation

This study uses a novel autologous tumor vaccine developed with 4-day DCs pulsed with oxidized lysate to elicit antitumor response. Furthermore, the combination of bevacizumab with a whole tumor antigen vaccine has not been tested in the clinic. Finally the combination of bevacizumab and metronomic cyclophosphamide in immunotherapy is novel.

Immunologic targeting of FOXP3 in inflammatory breast cancer cells

The forkhead transcription factor FOXP3 is necessary for induction of regulatory T lymphocytes (Tregs) and their immunosuppressive function. We have previously demonstrated that targeting Tregs by vaccination of mice with murine FOXP3 mRNA-transfected dendritic cells (DCs) elicits FOXP3-specific T cell responses and enhances tumor immunity. It is clear that FOXP3 expression is not restricted to T-cell lineage and herein, using RT-PCR, flow cytometry, and western immunoblot we demonstrate for the first time that FOXP3 is expressed in inflammatory breast cancer (IBC) cells, SUM149 (triple negative, ErbB1-activated) and SUM190 (ErbB2-overexpressing). Importantly, FOXP3-specific T cells generated in vitro using human FOXP3 RNA-transfected DCs as stimulators efficiently lyse SUM149 cells. Interestingly, an isogenic model (rSUM149) derived from SUM149 with an enhanced anti-apoptotic phenotype was resistant to FOXP3-specific T cell mediated lysis. The MHC class I cellular processing mechanism was intact in both cell lines at the protein and transcription levels suggesting that the resistance to cytolysis by rSUM149 cells was not related to MHC class I expression or to the MHC class I antigen processing machinery in these cells. Our data suggest that FOXP3 may be an effective tumor target in IBC cells however increased anti-apoptotic signaling can lead to immune evasion.

Antitumor vaccination with synthetic mRNA: strategies for in vitro and in vivo preclinical studies

Synthetic antigen-encoding mRNA is increasingly exploited as a tool for delivery of genetic information of complete antigens into professional antigen presenting dendritic cells for HLA haplotype-independent antigen-specific vaccination against cancer. Two strategies for mRNA-based antitumor vaccination have emerged into the clinical setting. One is transfection of autologous dendritic cells with synthetic mRNA for adoptive transfer into the patient. The other is direct injection of naked synthetic mRNA. Both methods have proven to be feasible and safe and to elicit antigen-specific immune responses. The design of novel synthetic vaccines employing synthetic mRNA requires further in-depth investigation of its bioavailability and immune pharmacology. This chapter summarizes the state-of-art in this field and describes methods elementary for preclinical studies of mRNA-based antitumor vaccine protocols.

Programming human dendritic cells with mRNA

Transfecting with in vitro transcribed, protein-encoding mRNA is a simple yet effective method to express high levels of the desired RNA-encoded proteins in primary cells. Cells can be transfected with antigen-encoding mRNA, which is translated into protein and is processed by the cellular antigen-processing pathway to generate antigen-presenting cells. Another elegant and increasingly popular application is to transfect cells with mRNA that encodes immune modulating molecules (cytokines, chemokines, toll-like receptors (TLRs), immune receptor ligands, immune receptor targeting antibodies) which, when translated into protein, can program cell behavior and/or function. In this chapter we describe an efficient method to deliver mRNA into human dendritic cells (DCs) by electroporation. This is currently the method of choice to deliver mRNA into antigen-presenting cells for generating vaccines for cancer immunotherapy.

Peptide vaccines and targeting HER and VEGF proteins may offer a potentially new paradigm in cancer immunotherapy

The ErbB family (HER-1, HER-2, HER-3 and HER-4) of receptor tyrosine kinases has been the focus of cancer immunotherapeutic strategies while antiangiogenic therapies have focused on VEGF and its receptors VEGFR-1 and VEGFR-2. Agents targeting receptor tyrosine kinases in oncology include therapeutic antibodies to receptor tyrosine kinase ligands or the receptors themselves, and small-molecule inhibitors. Many of the US FDA-approved therapies targeting HER-2 and VEGF exhibit unacceptable toxicities, and show problems of efficacy, development of resistance and unacceptable safety profiles that continue to hamper their clinical progress. The combination of different peptide vaccines and peptidomimetics targeting specific molecular pathways that are dysregulated in tumors may potentiate anticancer immune responses, bypass immune tolerance and circumvent resistance mechanisms. The focus of this review is to discuss efforts in our laboratory spanning two decades of rationally developing peptide vaccines and therapeutics for breast cancer. This review highlights the prospective benefit of a new, untapped category of therapies biologically targeted to EGF receptor (HER-1), HER-2 and VEGF with potential peptide 'blockbusters' that could lay the foundation of a new paradigm in cancer immunotherapy by creating clinical breakthroughs for safe and efficacious cancer cures.

Enhancement of DNA vaccine efficacy by targeting the xenogeneic human chorionic gonadotropin, survivin and vascular endothelial growth factor receptor 2 combined tumor antigen to the major histocompatibility complex class II pathway

BACKGROUND

A number of strategies have been used to improve the efficacy of the DNA vaccine for the treatment of tumors. These strategies, ranging from activating CD4+ T cell, manipulating antigen presentation and/or processing to anti-angiogenesis, focus on one certain aspect in the functioning of the vaccine. Therefore, their combination is necessary for rational DNA vaccines design by synergizing different regimens and overcoming the limitations of each strategy.

METHODS

A DNA fragment (HSV) encoding the C terminal 37 amino acids of human chorionic gonadotropin β chain (hCGβ), 5 different HLA-restricted cytotoxic T lymphocyte epitopes from human survivin and the third and fourth extracellular domains of vascular endothelial growth factor receptor 2 (VEGFR2) was inserted into the sequence between the luminal and transmembrane domain of human lysosome-associated membrane protein-1 cDNA for the construction of a novel DNA vaccine.

RESULTS

This novel vaccine, named p-L/HSV, has a potent antitumor effect on the LL/2 lung carcinoma model in syngeneic C57BL/6 mice. The immunologic mechanism involved in the antitumor effect referred to the activation of both cellular and humoral immune response. In addition, the tumor vasculature was abrogated as observed by immunohistochemistry in p-L/HSV immunized mice. Furthermore, the immunized mice received an additional boost with p-L/HSV 6 months later and showed a strong immune recall response.

CONCLUSIONS

The present study indicates that the strategies of combining antitumor with antiangiogenesis and targeting the tumor antigen to the major histocompatibility complex class II pathway cooperate well. Such a study may shed new light on designing vaccine for cancer in the future.

CD8 T-cell induction against vascular endothelial growth factor receptor 2 by Salmonella for vaccination purposes against a murine melanoma

The Salmonella type III secretion system (T3SS) efficiently translocates heterologous proteins into the cytosol of eukaryotic cells. This leads to an antigen-specific CD8 T-cell induction in mice orally immunized with recombinant Salmonella. Recently, we have used Salmonella's T3SS as a prophylactic and therapeutic intervention against a murine fibrosarcoma. In this study, we constructed a recombinant Salmonella strain translocating the immunogenic H-2D(b)-specific CD8 T-cell epitope VILTNPISM (KDR2) from the murine vascular endothelial growth factor receptor 2 (VEGFR2). VEGFR2 is a member of the tyrosine protein kinase family and is upregulated on proliferating endothelial cells of the tumor vasculature. After single orogastric vaccination, we detected significant numbers of KDR2-tetramer-positive CD8 T cells in the spleens of immunized mice. The efficacy of these cytotoxic T cells was evaluated in a prophylactic setting to protect mice from challenges with B16F10 melanoma cells in a flank tumor model, and to reduce dissemination of spontaneous pulmonary melanoma metastases. Vaccinated mice revealed a reduction of angiogenesis by 62% in the solid tumor and consequently a significant decrease of tumor growth as compared to non-immunized mice. Moreover, in the lung metastasis model, immunization with recombinant Salmonella resulted in a reduction of the metastatic melanoma burden by approximately 60%.

A vaccine targeting angiomotin induces an antibody response which alters tumor vessel permeability and hampers the growth of established tumors

Angiomotin (Amot) is one of several identified angiostatin receptors expressed by the endothelia of angiogenic tissues. We have shown that a DNA vaccine targeting Amot overcome immune tolerance and induce an antibody response that hampers the progression of incipient tumors. Following our observation of increased Amot expression on tumor endothelia concomitant with the progression from pre-neoplastic lesions to full-fledged carcinoma, we evaluated the effect of anti-Amot vaccination on clinically evident tumors. Electroporation of plasmid coding for the human Amot (pAmot) significantly delayed the progression both of autochthonous tumors in cancer prone BALB-neuT and PyMT genetically engineered mice and transplantable TUBO tumor in wild-type BALB/c mice. The intensity of the inhibition directly correlated with the titer of anti-Amot antibodies induced by the vaccine. Tumor inhibition was associated with an increase of vessels diameter with the formation of lacunar spaces, increase in vessel permeability, massive tumor perivascular necrosis and an effective epitope spreading that induces an immune response against other tumor associated antigens. Greater tumor vessel permeability also markedly enhances the antitumor effect of doxorubicin. These data provide a rationale for the development of novel anticancer treatments based on anti-Amot vaccination in conjunction with chemotherapy regimens.

The determinants of tumour immunogenicity

Many standard and targeted therapies, as well as radiotherapy, have been shown to induce an anti-tumour immune response, and immunotherapies rely on modulating the host immune system to induce an anti-tumour immune response. However, the immune response to such therapies is often reliant on the immunogenicity of a tumour. Tumour immunogenicity varies greatly between cancers of the same type in different individuals and between different types of cancer. So, what do we know about tumour immunogenicity and how might we therapeutically improve tumour immunogenicity? We asked four leading cancer immunologists around the world for their opinions on this important issue.

Hypoxia promotes tumor growth in linking angiogenesis to immune escape

Despite the impressive progress over the past decade, in the field of tumor immunology, such as the identification of tumor antigens and antigenic peptides, there are still many obstacles in eliciting an effective immune response to eradicate cancer. It has become increasingly clear that tumor microenvironment plays a crucial role in the control of immune protection. Tumors have evolved to utilize hypoxic stress to their own advantage by activating key biochemical and cellular pathways that are important in progression, survival, and metastasis. Hypoxia-inducible factor (HIF-1) and vascular endothelial growth factor (VEGF) play a determinant role in promoting tumor cell growth and survival. Hypoxia contributes to immune suppression by activating HIF-1 and VEGF pathways. Accumulating evidence suggests a link between hypoxia and tumor tolerance to immune surveillance through the recruitment of regulatory cells (regulatory T cells and myeloid derived suppressor cells). In this regard, hypoxia (HIF-1α and VEGF) is emerging as an attractive target for cancer therapy. How the microenvironmental hypoxia poses both obstacles and opportunities for new therapeutic immune interventions will be discussed.

Anti-angiogenic therapy renders large tumors vulnerable to immunotherapy via reducing immunosuppression in the tumor microenvironment

We have recently demonstrated that a 4-in-1 gene therapy strategy that contains two anti-angiogenic genes [endostatin and pigment epithelium-derived factor] and two cytokine genes [granulocyte macrophage colony-stimulating factor and interleukin 12] has a considerable antitumor effect on large tumors in a woodchuck hepatoma model. The current study further investigates the underlying mechanisms for the antitumor effect observed by using small rodent models. We found that immunotherapy alone increased immunosuppressive cells in large tumors over time, whereas the anti-angiogenic therapy contained in the 4-in-1 strategy alleviated immunosuppression and made tumors vulnerable to immunotherapy, thus resulting in a synergistic antitumor effect.

Vaccines targeting tumor blood vessel antigens promote CD8(+) T cell-dependent tumor eradication or dormancy in HLA-A2 transgenic mice

We have recently shown that effective cytokine gene therapy of solid tumors in HLA-A2 transgenic (HHD) mice lacking murine MHC class I molecule expression results in the generation of HLA-A2-restricted CD8(+) T effector cells selectively recognizing tumor blood vessel-associated pericytes and/or vascular endothelial cells. Using an HHD model in which HLA-A2(neg) tumor (MC38 colon carcinoma or B16 melanoma) cells are not recognized by the CD8(+) T cell repertoire, we now show that vaccines on the basis of tumor-associated blood vessel Ags (TBVA) elicit protective Tc1-dependent immunity capable of mediating tumor regression or extending overall survival. Vaccine efficacy was not observed if (HLA-A2(neg)) wild-type C57BL/6 mice were instead used as recipient animals. In the HHD model, effective vaccination resulted in profound infiltration of tumor lesions by CD8(+) (but not CD4(+)) T cells, in a coordinate reduction of CD31(+) blood vessels in the tumor microenvironment, and in the "spreading" of CD8(+) T cell responses to alternate TBVA that were not intrinsic to the vaccine. Protective Tc1-mediated immunity was durable and directly recognized pericytes and/or vascular endothelial cells flow-sorted from tumor tissue but not from tumor-uninvolved normal kidneys harvested from these same animals. Strikingly, the depletion of CD8(+), but not CD4(+), T cells at late time points after effective therapy frequently resulted in the recurrence of disease at the site of the regressed primary lesion. This suggests that the vaccine-induced anti-TBVA T cell repertoire can mediate the clinically preferred outcomes of either effectively eradicating tumors or policing a state of (occult) tumor dormancy.

Angiogenesis and immunity: a bidirectional link potentially relevant for the monitoring of antiangiogenic therapy and the development of novel therapeutic combination with immunotherapy

The immune system regulates angiogenesis in cancer with both pro- and antiangiogenic activities. The induction of angiogenesis is mediated by tumor-associated macrophages and myeloid-derived suppressor cells (MDSC) which produce proinflammatory cytokines, endothelial growth factors (VEGF, bFGF…), and protease (MMP9) implicated in neoangiogenesis. Some cytokines (IL-6, IL-17…) activated Stat3 which also led to the production of VEGF and bFGF. In contrast, other cytokines (IFN, IL-12, IL-21, and IL-27) display an antiangiogenic activity. Recently, it has been shown that some antiangiogenic molecules alleviates immunosuppression associated with cancer by decreasing immunosuppressive cells (MDSC, regulatory T cells), immunosuppressive cytokines (IL-10, TGFβ), and inhibitory molecules on T cells (PD-1). Some of these broad effects may result from the ability of some antiangiogenic molecules, especially cytokines to inhibit the Stat3 transcription factor. The association often observed between angiogenesis and immunosuppression may be related to hypoxia which induces both neoangiogenesis via activation of HIF-1 and VEGF and favors the intratumor recruitment and differentiation of regulatory T cells and MDSC. Preliminary studies suggest that modulation of immune markers (intratumoral MDSC and IL-8, peripheral regulatory T cells…) may predict clinical response to antiangiogenic therapy. In preclinical models, a synergy has been observed between antiangiogenic molecules and immunotherapy which may be explained by an improvement of immune status in tumor-bearing mice after antiangiogenic therapy. In preclinical models, antiangiogenic molecules promoted intratumor trafficking of effector cells, enhance endogenous anti-tumor response, and synergyzed with immunotherapy protocols to cure established murine tumors. All these results warrant the development of clinical trials combining antiangiogenic drugs and immunotherapy.

Angiogenesis and the tumor vasculature as antitumor immune modulators: the role of vascular endothelial growth factor and endothelin

Cancer immunotherapies have yielded promising results in recent years, but new approaches must be utilized if more patients are to experience the benefits of these therapies. Angiogenesis and the tumor endothelium confer unique immune privilege to a growing tumor, with significant effects on diverse immunological processes such as hematopoietic cell maturation, antigen presentation, effector T cell differentiation, cytokine production, adhesion, and T cell homing and extravasation. Here, we review the role of angiogenesis and the tumor endothelium on regulation of the antitumor immune response. We place particular emphasis on the role of vascular endothelial growth factor (VEGF) in the suppression of numerous immunological processes that control tumor progression. Further, we describe the unique crosstalk between the VEGF and endothelin systems, and how their interactions may shape the antitumor immune response. These insights establish new targets for combinatorial approaches to modify existing cancer immunotherapies.

Cytotoxic T cells - stroma interactions

The tumor microenvironment is a complex system playing an important role in tumor development and progression. Besides tumor cells, the tumor microenvironment harbours a variety of host-derived cells, such as endothelial cells, fibroblasts, innate and adaptive immune cells, as well as extracellular matrix (ECM) fibers, cytokines, and other mediators. This review discusses the potential role of hypoxia and endothelial cells within tumor microenvironment and emphasizes their interaction with antigen specific killer cells.