Project description:Immunotherapy provides an alternative approach for cancer treatment. However, in-depth analyses of the effects of immunotherapy on the tumor microenvironment (TME) have not been conducted in non-melanoma tumors. Here we describe changes in the pancreatic ductal adenocarcinoma (PDAC) TME following immunotherapy treatment, and show for the first time that vaccine-based immunotherapy directly alters the TME, inducing neogenesis of tertiary lymphoid structures that convert immunologically quiescent tumors into immunologically active tumors. Alterations in five pathways important for immune modulation and lymphoid structure development (TH17/Treg, NFkB, Ubiquitin-proteasome, Chemokines/chemokine receptors, and Integrins/adhesion molecules) in vaccine-induced intratumoral lymphoid aggregates were associated with improved post-vaccination responses. Additional studies in other cancers and patients treated with other forms of immunotherapy are warranted to further develop signatures defined in intratumoral lymphoid structures into biomarkers that predict effective anti-tumor immune responses. These signatures may also expose therapeutic targets for promoting more robust antitumor immune responses in the TME. Between July 2008 and September 2012, 59 patients were enrolled into an ongoing study of an irradiated, allogeneic GM-CSF-secreting pancreatic tumor vaccine (GVAX) administered intradermally either alone or in combination with immune modulatory doses of cyclophophamide (Cy) as neoadjuvant and adjuvant treatment for patients with resectable pancreatic ductal adenocarcinoma (PDAC). Patients were randomized 1:1:1 to 3 treatment arms. In Arm A, patients received GVAX alone; in Arm B, patients received GVAX plus a single intravenous dose of Cy at 200 mg/m2 1 day prior to each vaccination; in Arm C, patients received GVAX plus oral Cy at 100 mg once daily for 1 week on and 1 week off. Up to 6 GVAX treatments were administered and all of the patients remained in their initial treatment arms throughout the duration of the study. All 59 of the patients received the 1st GVAX treatment 2 weeks +/-4 days prior to surgery. Formalin-fixed paraffin-embedded (FFPE) tissue blocks of surgically resected PDAC were obtained from the pathology archive. FFPE tissue blocks from each subject were stained by H&E immediately before the vaccine therapy-induced lymphoid aggregates were microdissected . To better understand the functional status of these vaccine therapy induced lymphoid aggregate structures, gene microarray analysis on RNA isolated from microdissected lymphoid aggregates was performed. Gene expression was compared among samples grouped according to patient overall survival, post-vaccination induction of enhanced mesothelin-specific T cell responses in peripheral blood lymphocytes (PBL), and the intratumoral CD8+ T effector to FoxP3+ Treg ratio. Post-vaccination induction of enhanced mesothelin-specific T cell responses has been reported to correlate with longer survival in patients treated with Panc GVAX.

Project description:Pancreatic ductal adenocarcinoma (PDAC) has traditionally been thought of as an immunologically quiescent tumor type presumably because of a relatively low tumor mutational burden (TMB) and poor responses to checkpoint blockade therapy. However, many PDAC tumors exhibit T cell inflamed phenotypes. The presence of tertiary lymphoid structures (TLS) has recently been shown to be predictive of checkpoint blockade response in melanomas and sarcomas, and are prognostic for survival in PDAC. In order to more comprehensively understand tumor immunity in PDAC patients with TLS, we performed RNA-seq, single and multiplex IHC, flow cytometry and predictive genomic analysis on treatment naïve, PDAC surgical specimens. Forty-six percent of tumors contained distinct T and B cell aggregates reflective of "early-stage TLS" (ES-TLS), which correlated with longer overall and progression-free survival. These tumors had greater CD8+ T cell infiltration but were not defined by previously published TLS gene-expression signatures. ES-TLS+ tumors were enriched for IgG1 class-switched memory B cells and memory CD4+ T cells, suggesting durable immunological memory persisted in these patients. We also observed the presence of active germinal centers (mature-TLS) in 31% of tumors with lymphocyte clusters, whose patients had long-term survival (median 56 months). M-TLS-positive tumors had equivalent overall T cell infiltration to ES-TLS, but were enriched for activated CD4+ memory cells, naive B cells and NK cells. Finally, using a TCGA-PDAC dataset, ES-TLS+ tumors harbored a decreased TMB, but M-TLS with germinal centers expressed significantly more MHCI-restricted neoantigens as determined by an in silico neoantigen prediction method. Interestingly, M-TLS+ tumors also had evidence of increased rates of B cell somatic hypermutation, suggesting that germinal centers form in the presence of high-quality tumor neoantigens leading to increased humoral immunity that confers improved survival for PDAC patients. AbbreviationsTLS: tertiary lymphoid structures; GC: germinal center(s); PDAC: pancreatic ductal adenocarcinoma; RNA-seq: RNA sequencing; BCRseq: B cell receptor sequencing; HEV: high endothelial venule; PNAd: peripheral node addressin; TMB: tumor mutational burden; TCGA: the cancer genome atlas; PAAD: pancreatic adenocarcinoma; FFPE: formalin fixed paraffin embedded; TIME: tumor immune microenvironment.

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Pancreatic Cancer Chemotherapy Is Potentiated by Induction of Tertiary Lymphoid Structures in Mice.

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