Revisiting glioblastoma classification through an immunological lens: A narrative review

Glioblastoma (GBM) is the most aggressive primary brain tumor, marked by poor prognosis and resistance to conventional therapies. A critical barrier to effective treatment lies in its highly immunosuppressive and heterogeneous tumor microenvironment (TME), which orchestrates immune evasion and therapeutic failure. Tumor-associated macrophages (TAMs), particularly those with an M2-like phenotype, sustain GBM proliferation, angiogenesis, and stem-like cell maintenance. Dysfunctional T lymphocytes-especially the accumulation of regulatory T cells-further attenuate anti-tumor immunity. Natural killer (NK) cells, dendritic cells, neutrophils, and myeloid-derived suppressor cells (MDSCs) also contribute to immune suppression through distinct yet interconnected mechanisms. Despite the success of immunotherapies in other malignancies, immune checkpoint inhibitors, CAR-T cells, and tumor vaccines have yielded limited efficacy in GBM, hindered by low neoantigen burden, antigenic heterogeneity, and poor immune infiltration. Overcoming these challenges requires a systems-level understanding of the immunoregulatory circuits within the GBM TME and the development of combination immunotherapies guided by predictive biomarkers. This review systematically delineates the roles of immune components in GBM immunopathology and outlines the emerging therapeutic strategies.

Identification of Novel Tumor-Microenvironment-Regulating Factor That Facilitates Tumor Immune Infiltration in Colon Cancer

Gemcitabine Activates Natural Killer Cells to Attenuate Pancreatic Cancer Recurrence

082 The immune microenvironment of cutaneous squamous cell carcinoma in situ contains suppressive phenotypes

The immunobiology of hepatocellular carcinoma in humans and mice: Basic concepts and therapeutic implications

Tumors may effectively evade the immune system by several mechanisms which are not only confined to cancer cells but also may be related to the impaired function of immune responses.Tumor associated dendritic cell(TADC),myeloid derived suppressive cell(MDSC)and tumor associated macrophage(TAM)have been found to play a critical role in inducing immunosuppression in tumor immune escape.These researches may provide new strategies for immunotherapy against tumors. Key words: Tumor-associated dendritic cell,Myeloid derived suppressive cell ; Tumor associated macrophage,Immune escape,Tumor derived factors ;

The success of cancer immunotherapy is limited by multiple mechanisms of tumor-induced immunosuppression often a result of suppressive myeloid cells. M2-like tumor associated macrophages (TAM), myeloid-derived suppressor cells (MDSC), and tolerogenic dendritic cells (DC) constitute this immunosuppressive tumor microenvironment (TME) and have repeatedly been associated with poorer prognoses. Therapies designed to overturn this suppressive immune microenvironment could substantially enhance the efficacy of multiple immunotherapeutic approaches. Imprime PGG (Imprime) is a yeast β-1,3/1,6 glucan that has shown compelling efficacy in multiple Phase II trials with tumor-targeting and anti-angiogenic antibodies. As a pathogen associated molecular pattern (PAMP), Imprime activates myeloid cells (monocytes/macrophages, neutrophils, dendritic cells). Our previous ex vivo human and in vivo mouse studies have shown that Imprime promotes repolarization of M2 macrophages to an anti-tumor, M1-like orientation and enhances DC maturation, driving T cell expansion and the production of interferon gamma (IFNγ). We now show that Imprime can modulate the function of immature myeloid cells- the myeloid derived suppressor cells. MDSCs were generated from human cord blood by purifying CD34+ cells and culturing with GMCSF or GCSF ± tumor conditioned media. After 9 days, HLA-DR cells were depleted. The remaining cells were isolated and treated with Imprime or vehicle control. We found that incubating tumor-conditioned, vehicle-treated MDSCs with CD3/CD28-activated CD8 or CD4 T cells inhibited T cell proliferation. Imprime treatment significantly reduced this inhibition. Phenotypically, Imprime treatment elicited substantially increased expression of the co-stimulatory molecules CD80 and CD86 in both monocytic (Mo) and granulocytic (PMN) MDSCs, suggesting that these MDSCs now exhibited APC-like characteristics. In in vivo murine tumor models, Imprime was also able to modulate MDSC phenotype and function, which coincided with enhanced anti-tumor efficacy. Specifically, in the H441 human NSCLC xenograft model, Imprime when combined with 10mg/kg DC101 (murine anti-VEGFR2 Ab), significantly repressed tumor growth compared to the DC-101 alone or vehicle groups. Moreover, spleens from Imprime + DC101 treated-mice had reduced numbers of immunosuppressive, splenic Mo- or PMN-MDSC compared to either DC101 alone or vehicle control. The splenic Mo- or PMN-MDSCs from Imprime + DC101 treated mice that were present expressed significantly higher CD86. The Mo-MDSCs also expressed higher levels of iNOS, a key marker for activated macrophages. In another xenograft NSCLC model, H1299, the splenic MDSC after treatment with Imprime and α-VEGF-A Ab, bevacizumab (bev), showed increased iNOS expression and reduced Arg-1 expression- a shift typifying the M1 polarization state. Collectively, these data show that Imprime treatment can reshape the suppressive immune microenvironment of the tumor and elicit a robust anti-tumor immunity by targeting multiple myeloid lineage cells. Citation Format: Kathryn Fraser, Anissa Chan, Xiohong Qiu, Nadine Ottoson, Adria Bykowski Jonas, Jeremy Graff, Nandita Bose. Imprime PGG, a novel, clinical-stage pathogen associated molecular pattern, modulates MDSC function, facilitating a coordinated antitumor immune response [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A128.

Single agent immune checkpoint inhibitors (ICIs) are ineffective against metastatic breast cancer. One mechanism of intrinsic resistance is the presence of immunosuppressive myeloid cells and dysfunctional dendritic cells in the metastatic tumor microenvironment (TME) that impede the activation of anti-tumor T cells. A comparison of single-cell RNA sequencing analyses between breast-to-lung metastases and published data from breast tumors in the syngeneic NeuN mouse model of HER2+ breast cancer revealed that despite the presence of additional immune cell populations in the lungs, myeloid cells represented the predominant immune cell population in both TMEs and demonstrated similar changes in frequency and gene expression following treatment with the histone deacetylase inhibitor, entinostat. Our work highlights for the first time an increase in the frequency of conventional dendritic cells (cDC) with entinostat treatment in breast-to-lung metastases. Gene expression analyses of breast-to-lung metastases showed that entinostat-treated myeloid derived suppressor cells (MDSCs) and tumor associated macrophages (TAMs) downregulated genes associated with immunosuppression such as S100a8, Cd84, Trem2, and Mmp9. In addition, TAMs and cDCs upregulated the expression of genes associated with antigen presentation such as H2-K1, H2-Ab1, B2m, and Cd74 and pro-inflammatory markers such as Ccl3. NeuN mice were treated with the combination of entinostat and the immune checkpoint inhibitors, anti-PD-1 and anti-CTLA-4, and breast-to-lung metastases were analyzed via flow cytometry, demonstrating an increase in the frequency of cDC1s and CD8+ T cells expressing granzyme B. Furthermore, the treatment combination of entinostat + anti-PD-1 + anti-CTLA-4 significantly increased survival in an experimental model of lung metastasis using a newly characterized model derived from the original NT2.5 HER2+ cell line, NT2.5LM. These results confirm those of our breast expansion cohort from the phase I clinical trial NCI-9844 that demonstrate a 30% overall response rate in 20 heavily pretreated patients with metastatic disease treated with entinostat + Nivolumab (anti-PD-1) + Ipilimumab (anti-CTLA-4). We highlight for the first time significant alterations within multiple myeloid derived cell types, cDCs, TAMs and MDSCs, from within a native metastatic niche, that are likely driving an entinostat mediated improved response to ICI treatment. Citation Format: Edgar Gonzalez, Adam L. MacLean, Evanthia T. Roussos Torres, Aaron Baugh, Jesse Kreger, Sofi Castanon, Valerie Narumi, Elizabeth M. Jaffee. Entinostat enhances the efficacy of checkpoint inhibition in breast-to-lung metastases and is associated with alterations in the phenotype and function of myeloid cell populations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3256.

TGF-β Alters the Proportion of Infiltrating Immune Cells in a Pancreatic Ductal Adenocarcinoma

BackgroundNatural Killer (NK) cells are innate immune cells able to reject hematological malignancies and correlate with better prognosis in solid tumors. However, conventional NK (cNK) cell anti-tumor activity is limited...

Cellular and molecular regulation of the immune system is exquisitely controlled in the brain and disrupted in neoplasia. Glioblastoma (GBM) has an immunosuppressive phenotype, and despite the accumulation of immune cells in the tumor microenvironment, tumor growth persists. Myeloid derived suppressor cells (MDSCs) are a class of immature immune cells that mitigate cytotoxic T cell responses and promote immunosuppression in a variety of cancers. MDSCs are increased in the peripheral blood of GBM patients, but their role in the GBM microenvironment is undefined. We observed co-localization between arginase (Arg1) producing immunosuppressive MDSCs and cancer stem cells (CSCs) in GBM patient specimens and xenografts, leading to the hypothesis that CSCs stimulate MDSCs to promote immunosuppression. Intracranial injections of CSCs into mice led to GBM formation, expansion of the Arg1-producing MDSCs within the marrow of GBM-bearing mice, and increased levels of MDSCs within the GBM microenvironment. CSC conditioned media increased Arg1 production of murine marrow MDSCs which were then able to modulate cytotoxic T cell responses in co-culture models. Screening of conditioned media revealed cytokines secreted selectively by CSCs that activated MDSCs suppression. Removal of CSC-secreted factors decreased MDSCs in the GBM microenvironment, increased cytotoxic T cell infiltration, and had a pronounced survival benefit. Peripheral targeting of MDSCs through a sub-therapeutic dose of 5-fluorouracil (5-FU) in an immunocompetent syngeneic mouse model led to a similar phenotype to CSC-secreted factor removal in the GBM microenvironment, and an even greater survival benefit. Taken together, our results suggest a critical role of MDSC-mediated immunosuppression in GBM, a novel paradigm of immunomodulation by CSCs, and demonstrate that peripheral removal of MDSCs leads to increased T cell infiltration into GBM, and consequently suggest a novel chemotherapeutic strategy that is not generally toxic to bone marrow and that is not dependent on agents crossing the blood brain barrier.

Inflammation and Colon Cancer

Glioblastoma, also known as glioblastoma multi-forme, is the most common and deadliest form of high-grade malignant brain tumors with limited available treatments. Within the glioblastoma tumor microenvironment (TME), tumor cells, stromal cells, and infiltrating immune cells continuously interact and exchange signals through various secreted factors including cytokines, chemokines, growth factors, and metabolites. Simultaneously, they dynamically reprogram their metabolism according to environmental energy demands such as hypoxia and neo-vascularization. Such metabolic re-programming can determine fates and functions of tumor cells as well as immune cells. Ultimately, glioma cells in the TME transform immune cells to suppress anti-tumor immune cells such as T, natural killer (NK) cells, and dendritic cells (DC), and evade immune surveillance, and even to promote angiogenesis and tumor metastasis. Glioma-associated microglia/macrophages (GAMM) and myeloid-derived suppressor cells (MDSC) are most abundantly recruited and expanded myeloid lineage cells in glioblastoma TME and mainly lead to immunosuppression. In this review, of myeloid cells we will focus on MDSC as an important driver to induce immunosuppression in glioblastoma. Here, we review current literature on immunosuppressive functions and metabolic reprogramming of MDSCs in glioblastoma and discuss their metabolic pathways as potential therapeutic targets to improve current incurable glioblastoma treatment.

Objective To establish the pancreatic cancerogenesis model in mice and to observe the changes of the immune cell populations in peripheral blood and pancreatic lesions. Methods The in situ embedding of canerogen dimethylbenzanthracene (DMBA) was adopted to establish the pancreatic cancerogenesis process from chronic pancreatitis (CP) , pancreatic intraepithelial neoplasma (PanIN) to pancreatic cancer. Totally 60 C57BL/6J mice were used, and 8 weeks after embedding, the mice were killed. 20 mice were randomized selected, and 7 immune cell populations in the peripheral blood and pancreatic lesions were detected by flow cytometery (FCM) . Results During the observational peroid of 8 weeks, 14 (23.3%) mice died. Among the 46 survivors, 20 mice were randomized selected for FCM analysis. All of the 46 pancreatic lesions were pathologically analyzed. 12 cases were CP (26.1%) , 11 cases were lower grade PanIN (PanIN-1,2, LG-PanIN) (23.9%) , 9 cases were high grade PanIN (PanIN-3, HG-PanIN) (19.6%) and 14 cases were PC. Among the 20 randomized selected mice, 4 cases were CP, 7 cases were LG-PanIN, 4 cases were HG-PanIN and 5 cases were PC. The myeloid derived suppressor cells (MDSC) of HG-PanIN and CP were significantly more than that of LG-PanIN and CP. In the pancreatic lesions, the granulocytes, MDSC and M2 polarized TAM of HG-PanIN and PC were significantly more than that of LG-PanIN and CP. On the contrary, the T lymphocytes and M1 polarized TAM were significantly decreased. Conclusions In situ embedding of DMBA is a feasible and practical method to establish the spontaneous pancreatic cancerogenesis model in the immunocompetent mice. Pancreatic cancerogenesis can induce systemic and even stronger local immunosuppression, and the MDSC and M2 polarized TAM may play the vital roles. Key words: Pancreatic Cancer; Cancerogenesis; Immunosuppression; Myeloid-derived suppressor cells; Tumor associated macrophages

Immunologic Monitoring of Cellular Immune Responses in Cancer Vaccine Therapy