Targeted depletion of an MDSC subset unmasks pancreatic ductal adenocarcinoma to adaptive immunity
IM Stromnes, JS Brockenbrough, K Izeradjene… - Gut, 2014 - gut.bmj.com
IM Stromnes, JS Brockenbrough, K Izeradjene, MA Carlson, C Cuevas, RM Simmons…
Gut, 2014•gut.bmj.comBackground Pancreatic ductal adenocarcinoma (PDA) is characterised by a robust
desmoplasia, including the notable accumulation of immunosuppressive cells that shield
neoplastic cells from immune detection. Immune evasion may be further enhanced if the
malignant cells fail to express high levels of antigens that are sufficiently immunogenic to
engender an effector T cell response. Objective To investigate the predominant subsets of
immunosuppressive cancer-conditioned myeloid cells that chronicle and shape the …
desmoplasia, including the notable accumulation of immunosuppressive cells that shield
neoplastic cells from immune detection. Immune evasion may be further enhanced if the
malignant cells fail to express high levels of antigens that are sufficiently immunogenic to
engender an effector T cell response. Objective To investigate the predominant subsets of
immunosuppressive cancer-conditioned myeloid cells that chronicle and shape the …
Background
Pancreatic ductal adenocarcinoma (PDA) is characterised by a robust desmoplasia, including the notable accumulation of immunosuppressive cells that shield neoplastic cells from immune detection. Immune evasion may be further enhanced if the malignant cells fail to express high levels of antigens that are sufficiently immunogenic to engender an effector T cell response.
Objective
To investigate the predominant subsets of immunosuppressive cancer-conditioned myeloid cells that chronicle and shape the progression of pancreas cancer. We show that selective depletion of one subset of myeloid-derived suppressor cells (MDSC) in an autochthonous, genetically engineered mouse model (GEMM) of PDA unmasks the ability of the adaptive immune response to engage and target tumour epithelial cells.
Methods
A combination of in vivo and in vitro studies were performed employing a GEMM that faithfully recapitulates the cardinal features of human PDA. The predominant cancer-conditioned myeloid cell subpopulation was specifically targeted in vivo and the biological outcomes determined.
Results
PDA orchestrates the induction of distinct subsets of cancer-associated myeloid cells through the production of factors known to influence myelopoiesis. These immature myeloid cells inhibit the proliferation and induce apoptosis of activated T cells. Targeted depletion of granulocytic MDSC (Gr-MDSC) in autochthonous PDA increases the intratumoral accumulation of activated CD8 T cells and apoptosis of tumour epithelial cells and also remodels the tumour stroma.
Conclusions
Neoplastic ductal cells of the pancreas induce distinct myeloid cell subsets that promote tumour cell survival and accumulation. Targeted depletion of a single myeloid subset, the Gr-MDSC, can unmask an endogenous T cell response, disclosing an unexpected latent immunity and invoking targeting of Gr-MDSC as a potential strategy to exploit for treating this highly lethal disease.
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