Immunotherapy Converts Nonimmunogenic Pancreatic Tumors into Immunogenic Foci of Immune Regulation

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is considered a “non-Immunogenic” neoplasm. Single agent immunotherapies have failed to demonstrate significant clinical activity in PDAC and other “non-immunogenic” tumors, in part due to a complex tumor microenvironment (TME) that provides a formidable barrier to immune infiltration and function. We designed a neo-adjuvant and adjuvant clinical trial comparing an irradiated, granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic PDAC vaccine (GVAX) given as single agent, or in combination with low dose cyclophosphamide (Cy) to deplete regulatory T cells (Tregs), to study how the TME is altered by immunotherapy. Examination of resected PDACs revealed the formation of vaccine-induced intratumoral tertiary lymphoid aggregates in 33/39 patients two weeks following vaccine treatment. Immunohistochemical analysis showed these aggregates to be regulatory structures of adaptive immunity. Microarray analysis of microdissected aggregates identified gene-expression signatures in five signaling pathways involved in regulating immune cell activation and trafficking that were associated with improved post-vaccination responses. A suppressed Treg pathway and an enhanced Th17 pathway within these aggregates were associated with improved survival, enhanced post-vaccination mesothelin-specific T-cell responses and increased intratumoral Teffector/Treg ratios. This study provides the first example of immune-based therapy converting a “non-immunogenic” neoplasm into an “immunogenic” neoplasm by inducing infiltration of T cells and development of tertiary lymphoid structures in the TME. Post-GVAX T-cell infiltration and aggregate formation resulted in the upregulation of immunosuppressive regulatory mechanisms including the PD-1/PD-L1 pathway, suggesting that vaccine-primed PDAC patients may be better candidates than vaccine–naïve patients for immune checkpoint and other immunomodulatory therapies.

Priming the pancreatic cancer tumor microenvironment for checkpoint-inhibitor immunotherapy

“…Therefore, we designed a neo-adjuvant and adjuvant clinical trial comparing GVAX given as single agent, or in combination with low dose Cy. 13 The first treatment was given 2 weeks prior to surgery providing the first opportunity to study how the PDAC TME is altered by GVAX-based immunotherapy.…”

Induction of Antigen-Specific Cytotoxic T Lymphocytes by Chemoradiotherapy in Patients Receiving Wilms? Tumor 1-Targetted Dendritic Cell Vaccinations for Pancreatic Cancer

“…Tetramer analysis and ELISpot assays are required to be reproducible and validated methods with simple, easily-reproducible protocols. Although the factors affecting the induction of WT1-CTLs have yet to be fully elucidated, the induction of immunosuppressive regulatory mechanisms in response to vaccination may play a major role [14]. Immune checkpoint inhibitors are rapidly being developed as chemotherapeutic agents [24]; however, radiotherapy allows the in situ modulation of Tregs and other suppressors in the tumoral microenvironment.…”

“…Studies have reported increased OS in patients with inoperable PC who received DC vaccination in combination with chemotherapeutic drugs such as GEM and S-1 [8,11,12]. Allogenic vaccines in PC induce T cell infiltration and aggregate formation, resulting in the induction of immunosuppressive regulatory mechanisms [14]. The efficacy of DC vaccination for PC may to be enhanced by off-target effects of GEM and S-1 [15].…”

In vivo amelioration of endogenous antitumor autoantibodies via low-dose P4N through the LTA4H/activin A/BAFF pathway

“…Paclitaxel also reduced the number of regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs), and led to the augmentation of the functions of CD4 and CD8 T cells (16,17). In other cases, DNA alkylating agents, such as cyclophosphamide and mafosfamide, in low doses selectively depleted Treg cells (18,19), caused an increase in effector T cells (Teff)/Treg cell ratios via up-regulation of the T helper (Th) 17 pathway (20), and improved the outcome of tumor vaccinations against cancer (21)(22)(23). Furthermore, doxorubicin, mitomycin C, vinblastine, and methotrexate in low doses have been found to up-regulate DC maturation, antigen processing, and antigen presentation, which led to synergistic antitumor effects of low-dose chemotherapy combined with a DC vaccine (24)(25)(26).…”