Forming Specialized Immune Cell Structures Could Combat Pancreatic Cancer

Brandon May

November 04, 2021

In a new study, researchers stimulated immune cells to assemble into tertiary lymphoid structures that improved the efficacy of chemotherapy in a preclinical model of pancreatic cancer.

Overall, the evidence generated by the study supports the notion that induction of tertiary lymphoid structures may potentiate chemotherapy's antitumor activity, at least in a murine model of pancreatic ductal adenocarcinoma (PDAC). A more detailed understanding of tertiary lymphoid structure "kinetics and their induction, owing to multiple host and tumor factors, may help design personalized therapies harnessing the potential of immuno-oncology," Francesca Delvecchio of Queen Mary University of London and colleagues wrote in Cellular and Molecular Gastroenterology and Hepatology.

While the immune system can play a role in combating cancer, a dense stroma surrounds pancreatic cancer centers, often blocking the immune cells' ability to access the tumor. As shown by Young and colleagues, this leads immunotherapies to have very little success in the management of pancreatic cancer, despite the efficacy of these therapies in other types of cancer.

In a proportion of patients with pancreatic cancer, clusters of immune cells known as tertiary lymphoid structures can assemble within the stroma. These structures are associated with improved survival in PDAC. In the study, Delvecchio and colleagues sought to further elucidate the role of tertiary lymphoid structures in PDAC, particularly the structures' antitumor activity.

The investigators analyzed donated tissue samples from patients to identify the presence of the structures within chemotherapy-naive human pancreatic cancer. Tertiary lymphoid structures were defined by the presence of tissue zones that were rich in T cells, B cells, and dendritic cells. Staining techniques were used to visualize the various cell types in the samples, revealing tertiary lymphoid structures in approximately 30% of tissue microarrays and 42% of the full section.

Multicolor immunofluorescence and immunohistochemistry were also used to characterize tertiary lymphoid structures in murine models of pancreatic cancer. Additionally, the investigators developed the orthotopic murine model to assess the development of the structures and the effect of a combined chemotherapy and immunotherapy regimen on tumor growth.

While tertiary lymphoid structures were not initially present in the preclinical murine model, B cells and T cells subsequently infiltrated into the tumor site following injection of lymphoid chemokines. These cells consequently assembled into the tertiary lymphoid structures.

In addition, the researchers combined chemotherapy gemcitabine with the intratumoral lymphoid chemokine and injected this combination treatment into orthotopic tumors. Following injection, the researchers observed "altered immune cell infiltration," which facilitated the induction of tertiary lymphoid structures and potentiated antitumor activity of the chemotherapy. As a result, there was a significant reduction in the tumors, an effect the researchers did not find following the use of either treatment alone.

According to the investigators, the antitumor activity observed following induction of the tertiary lymphoid structures within the cancer is associated with B cell–mediated activation of dendritic cells, a requirement for the initiation of the immune response.

Based on the findings, the researchers concluded that the combination of chemotherapy and lymphoid chemokines could be a viable strategy for promoting an antitumor immune response in pancreatic cancer. In turn, the researchers suggest this strategy may result in better clinical outcomes for patients with the disease. Additionally, the researchers wrote that mature tertiary lymphoid structures in PDAC prior to an immune treatment could "be used as a biomarker to define inclusion criteria of patients in immunotherapy protocols, with the aim to boost the ongoing antitumor immune response."

Given that the study relied on a mouse model, the findings may currently lack generalizability across humans. In the context of PDAC, the researchers wrote that further investigation and understanding of the formation of tertiary lymphoid structures may support the development of tailored treatments, including those that take advantage of the body's immune system, to combat cancer and improve patient outcomes.

The researchers reported no conflicts of interest with the pharmaceutical industry. No funding was reported for the study.

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