Early expression of stem cell-associated genes within the CD8 compartment after treatment with a tumor vaccine

Autologous tumor cell vaccines for post-operative active-specific immunotherapy of colorectal carcinoma: long-term patient survival and mechanism of function

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. Surgery remains the primary curative treatment but nearly 50% of patients relapse as consequence of micrometastatic or minimal residual disease (MRD) at the time of surgery. Spontaneous T-cell-mediated immune responses to CRC tumor-associated antigens (TAAs) in tumor-draining lymph nodes and in the bone marrow (BM) lead to infiltration of the tumors by lymphocytes. Certain types of such tumor-infiltrating lymphocytes (TILs) have a positive and others a negative impact on the patients' prognosis. This review focuses on advances in CRC active-specific immunotherapy (ASI), in particular on results from randomized controlled clinical studies employing therapeutic autologous tumor cell vaccines. The observed improvement of long-term survival is explained by activation and mobilization of a pre-existing repertoire of tumor-reactive memory T cells which, according to recent discoveries, reside in distinct niches of patients' bone marrow in neighborhood with hematopoietic (HSC) and mesenchymal (MSC) stem cells. Interestingly, memory T cells also contain a subset of stem memory T cells (SMTs) in addition to effector (EMTs) and central memory T cells (CMTs). The mechanism of function of a therapeutic vaccine in a chronic disease is distinct from that of prophylactic vaccines which have to generate de novo protective immune responses. The advantage of autologous vaccines for mobilization of a broad and highly individual repertoire of memory T cells will be discussed.

Examining T cells at vaccine sites of tumor-bearing hosts provides insights to dysfunctional T-cell immunity

When tumor vaccines are administered as cancer immunotherapy, cellular interactions at the vaccine site are crucial to the generation of antitumor immunity. Examining interactions at the vaccine site could provide important insights to the success or failure of vaccination. Our laboratory previously showed that while administration of a cell-based vaccine to tumor-free mice leads to productive antineuroblastoma immunity, vaccination of tumor-bearing mice does not. The goal of this study was to examine immune effectors at the vaccine site to identify mechanisms responsible for the generation of ineffective antitumor immunity in tumor-bearing mice. The results of this study show that vaccine sites of tumor-bearing mice contained significantly fewer T cells than vaccine sites of tumor-free mice. Similar migration and proliferation of T cells was observed in the vaccine sites of tumor-bearing and tumor-free mice, but T cells in the sites of tumor-bearing mice were more apoptotic. T cells at the vaccine sites of both tumor-free and tumor-bearing mice had an effector-memory phenotype and expressed activation markers. Despite the activated phenotype, T cells from tumor-bearing mice elicited defective antitumor immune responses. Although T cells from vaccine sites of tumor-bearing mice were capable of producing inflammatory cytokines, the T cells from tumor-bearing mice produced lower levels of cytokines compared with T cells from the tumor-free mice. Remarkably, this defect seems to be systemic, affecting distal T cells in tumor-bearing mice. This study demonstrates that the defective vaccine-induced immune response to neuroblastoma in tumor-bearing hosts originates as a result of tumor burden, resulting in poor antitumor immunity.

Microarray analysis for a comprehensive immunological-status evaluation during cancer vaccine immune monitoring

Anticancer immune responses can be enhanced by immune intervention that promotes complex biological mechanisms involving several cellular populations. The classical immune monitoring for biological-based cancer clinical trials is often based on single-cell analysis. However, the overall effect could be lost by such a reductionist approach explaining the lack of correlation among clinical and immunological endpoints often reported. Microarray technology could give the possibility of studying in a multiparametric setting the immune therapy effects. The application of microarray is leading to an improved understanding of the immune responses to tumor immunotherapy. In fact, analysis of cancer vaccine-induced host responses using microarrays is proposed as valuable alternative to the standard cell-based methods. This paper shows successful examples of how high-throughput gene expression profiling contributed to the understanding of anticancer immune responses during biological therapy, introducing as well the integrative platforms that allow the network analysis in molecular biology studies.