Pancreatic ductal adenocarcinoma (PDAC) is characterized by an excessive amount of desmoplastic stroma seeded with inflammatory cells and it is one of the most aggressive forms of cancer with no current specific therapies. Tumor-associated macrophages (TAMs) are a major component of the tumor microenvironment (TME), and in most solid cancers increased TAM infiltration is associated with a poor prognosis. TAMs can be described as classically activated M1 types with pro-inflammatory antitumor functions, versus alternatively activated M2 types with immunosuppressive pro-tumor functions. The immunosuppressive functions of M2 TAMs can be exerted through release of cytokines and growth factors as well as via direct recruitment of T regulatory cells (Tregs), a subset of lymphocytes responsible for immune tolerance of the system to the tumor. While the differentiation from M1 to M2 in PDAC has been shown to be associated with a worse prognosis, little is known about PDAC TAM polarization and its potential correlation to Treg recruitment.
For this study we have used MultiOmyx™, a multiplexed immunofluorescence (IF) assay allowing up to 60 protein biomarkers to be interrogated from a single FFPE section. The MultiOmyx™ assay utilizes a pair of directly conjugated Cyanine dye-labeled (Cy3, Cy5) antibodies per round of staining. Each round of staining is imaged and followed by novel dye inactivation chemistry, enabling repeated rounds of staining and deactivation.
Using the pan macrophage marker CD68 in combination with either M1 marker HLA-DR or M2 marker CD163 we confirmed the presence of M1 and M2 TAM populations in 9 stage IIB PDAC FFPE samples and found a positive significant correlation (Pearson’s correlation p < 0.05) between the presence of M2 TAMs and Tregs, but not between M1 TAMs and Tregs. Moreover, in a spatial nearest neighbor analysis we found M2 type TAMS to be in closer proximity to Tregs compared to M1 type TAMs.
We demonstrate a positive significant correlation between the presence of, as well as the distance between, M2 TAMs and Tregs in the TME of PDAC, suggesting a possible pathway in which TAM polarization plays an immunosuppressive function by recruiting Tregs.
NeoGenomics.
NeoGenomics.
A. Juncker-Jensen, J. Fang, R. Padmanabhan, E. Parnell, J. Kuo, Q. Au, E. Leones, F. Sahafi, M. Nagy, N. Hoe, J. William: Employed by NeoGenomics.