PURPOSE: Patients with high-grade serous ovarian carcinoma (HGSOC) are virtually insensitive to immune checkpoint inhibitors (ICI) employed as standalone therapeutics, at least in part reflecting microenvironmental immunosuppression. Thus, conventional chemotherapeutics and targeted anticancer agents that not only mediate cytotoxic effects but also promote the recruitment of immune effector cells to the HGSOC microenvironment stand out as promising combinatorial partners for ICIs in this oncological indication. EXPERIMENTAL DESIGN: We harnessed a variety of transcriptomic, spatial, and functional assays to characterize the differential impact of neoadjuvant paclitaxel-carboplatin on the immunological configuration of paired primary and metastatic HGSOC biopsies as compared to neoadjuvant chemotherapy (NACT)-naïve HGSOC samples from five independent patient cohorts. RESULTS: We found NACT-driven endoplasmic reticulum stress and calreticulin exposure in metastatic HGSOC lesions culminates with the establishment of a dense immune infiltrate including follicular T cells (TFH cells), a prerequisite for mature tertiary lymphoid structure (TLS) formation. In this context, TLS maturation was associated with an increased intratumoral density of ICI-sensitive TCF1+PD1+ CD8+ T cells over their ICI-insensitive TIM-3+PD1+ counterparts. Consistent with this notion, chemotherapy coupled with a PD1-targeting ICI provided a significant survival benefit over either therapeutic approach in syngeneic models of HGSOC bearing high (but not low) tumor mutational burden. CONCLUSIONS: Altogether, our findings suggest that NACT promotes TLS formation and maturation in HGSOC lesions, de facto preserving an intratumoral ICI-sensitive T-cell phenotype. These observations emphasize the role of rational design, especially relative to the administration schedule, for clinical trials testing chemotherapy plus ICIs in patients with HGSOC. See related commentary by Bravo Melgar and Laoui, p. 10.

• MeSH
• CD8-Positive T-Lymphocytes * immunology   drug effects   MeSH
• Tertiary Lymphoid Structures * immunology   pathology   MeSH
• Hepatocyte Nuclear Factor 1-alpha * genetics   metabolism   MeSH
• Immune Checkpoint Inhibitors * therapeutic use   pharmacology   MeSH
• Carboplatin administration & dosage   pharmacology   therapeutic use   MeSH
• Humans MeSH
• Tumor Microenvironment * immunology   drug effects   MeSH
• Ovarian Neoplasms * drug therapy   immunology   pathology   MeSH
• Neoadjuvant Therapy methods   MeSH
• Paclitaxel administration & dosage   therapeutic use   pharmacology   MeSH
• Antineoplastic Combined Chemotherapy Protocols therapeutic use   pharmacology   MeSH
• Cystadenocarcinoma, Serous drug therapy   pathology   immunology   MeSH
• Endoplasmic Reticulum Stress drug effects   immunology   MeSH
• Lymphocytes, Tumor-Infiltrating immunology   drug effects   metabolism   MeSH
• Check Tag
• Humans MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Hepatocyte Nuclear Factor 1-alpha * MeSH
• Immune Checkpoint Inhibitors * MeSH
• Carboplatin MeSH
• Paclitaxel MeSH

The immune checkpoint inhibitors have revolutionized cancer immunotherapy. These inhibitors are game changers in many cancers and for many patients, sometimes show unprecedented therapeutic efficacy. However, their therapeutic efficacy is largely limited in many solid tumors where the tumor-controlled immune microenvironment prevents the immune system from efficiently reaching, recognizing, and eliminating cancer cells. The tumor immune microenvironment is largely orchestrated by immune cells through which tumors gain resistance against the immune system. Among these cells are mast cells and dendritic cells. Both cell types possess enormous capabilities to shape the immune microenvironment. These capabilities stage these cells as cellular checkpoints in the immune microenvironment. Regaining control over these cells in the tumor microenvironment can open new avenues for breaking the resistance of solid tumors to immunotherapy. In this review, we will discuss mast cells and dendritic cells in the context of solid tumors and how these immune cells can, alone or in cooperation, modulate the solid tumor resistance to the immune system. We will also discuss how this modulation could be used in novel immunotherapeutic modalities to weaken the solid tumor resistance to the immune system. This weakening could then help other immunotherapeutic modalities engage against these tumors more efficiently.

• Keywords
• cellular checkpoint, dendritic cells, immunotherapy, mast cells,
• MeSH
• Dendritic Cells pathology   MeSH
• Immunotherapy MeSH
• Immune Checkpoint Inhibitors MeSH
• Humans MeSH
• Mast Cells * pathology   MeSH
• Tumor Microenvironment MeSH
• Neoplasms * pathology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Immune Checkpoint Inhibitors MeSH

Dendritic cells (DCs) have received considerable attention as potential targets for the development of novel cancer immunotherapies. However, the clinical efficacy of DC-based vaccines remains suboptimal, largely reflecting local and systemic immunosuppression at baseline. An autologous DC-based vaccine (DCVAC) has recently been shown to improve progression-free survival and overall survival in randomized clinical trials enrolling patients with lung cancer (SLU01, NCT02470468) or ovarian carcinoma (SOV01, NCT02107937), but not metastatic castration-resistant prostate cancer (SP005, NCT02111577), despite a good safety profile across all cohorts. We performed biomolecular and cytofluorometric analyses on peripheral blood samples collected prior to immunotherapy from 1000 patients enrolled in these trials, with the objective of identifying immunological biomarkers that may improve the clinical management of DCVAC-treated patients. Gene signatures reflecting adaptive immunity and T cell activation were associated with favorable disease outcomes and responses to DCVAC in patients with prostate and lung cancer, but not ovarian carcinoma. By contrast, the clinical benefits of DCVAC were more pronounced among patients with ovarian carcinoma exhibiting reduced expression of T cell-associated genes, especially those linked to TH2-like signature and immunosuppressive regulatory T (TREG) cells. Clinical responses to DCVAC were accompanied by signs of antitumor immunity in the peripheral blood. Our findings suggest that circulating signatures of antitumor immunity may provide a useful tool for monitoring the potency of autologous DC-based immunotherapy.

• Keywords
• Cancer immunotherapy, anti-PD-1, circulating biomarkers, epithelial ovarian carcinoma, metastatic castrate-resistant prostate cancer, non-small cell lung carcinoma,
• MeSH
• Dendritic Cells metabolism   MeSH
• Carcinoma, Ovarian Epithelial drug therapy   MeSH
• Humans MeSH
• Lung Neoplasms * drug therapy   therapy   MeSH
• Ovarian Neoplasms * genetics   therapy   MeSH
• Cancer Vaccines * therapeutic use   MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cancer Vaccines * MeSH

Dendritic cell (DC)-based vaccination for cancer treatment has seen considerable development over recent decades. However, this field is currently in a state of flux toward niche-applications, owing to recent paradigm-shifts in immuno-oncology mobilized by T cell-targeting immunotherapies. DC vaccines are typically generated using autologous (patient-derived) DCs exposed to tumor-associated or -specific antigens (TAAs or TSAs), in the presence of immunostimulatory molecules to induce DC maturation, followed by reinfusion into patients. Accordingly, DC vaccines can induce TAA/TSA-specific CD8+/CD4+ T cell responses. Yet, DC vaccination still shows suboptimal anti-tumor efficacy in the clinic. Extensive efforts are ongoing to improve the immunogenicity and efficacy of DC vaccines, often by employing combinatorial chemo-immunotherapy regimens. In this Trial Watch, we summarize the recent preclinical and clinical developments in this field and discuss the ongoing trends and future perspectives of DC-based immunotherapy for oncological indications.

• Keywords
• DAMPs, Dendritic cells, T cell priming, TAAs, antigen cross-presentation, clinical trial, immune checkpoint blockers, tumor-infiltrating lymphocytes,
• MeSH
• Antigens, Neoplasm MeSH
• Dendritic Cells MeSH
• Immunotherapy MeSH
• Humans MeSH
• Neoplasms * drug therapy   MeSH
• Cancer Vaccines * therapeutic use   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antigens, Neoplasm MeSH
• Cancer Vaccines * MeSH