Tumor Suppressor Adenomatous Polyposis Coli Regulates T Lymphocyte Migration

Familial adenomatous polyposis (FAP) is an autosomal dominant inherited disease that often results from germline mutations in the adenomatous polyposis coli (APC) gene, a tumor suppressor and polarity regulator. APC protein regulates the Wnt/β-catenin signaling pathway as a component of the β-catenin destruction complex.

The key role of immunity in human colorectal carcinoma was underscored by the correlation between the type and frequency of infiltrating T lymphocytes and favorable patient prognosis. Once activated in lymph nodes, lymphocytes go through bloodstream recirculation and adhesion-dependent trans-endothelial migration to finally invade tumor tissues, where they execute their effector functions to eliminate tumor cells.

Cellular Biologist at the Institut Pasteur (Paris, France) and their colleagues recruited seven FAP patients and their respective sex-, age-, and ethnicity-matched healthy donors. Peripheral blood mononuclear cells were purified from FAP patients or healthy donors by Ficoll-Hypaque centrifugation and activated. Cell counts, viability and size were assessed every two days (up to day 12) by a LUNA-FL Dual Fluorescence Cell Counter, after cell staining with acridine orange/propidium iodide mixture (Logos Biosystems, Villeneuve d’Ascq, France).

At day 5, CD4 T cells were purified using positive magnetic sorting (Miltenyi Biotec, Bergisch Gladbach, Germany) and CD8 T cells recovered from the non-retained population. Other procedures carried out included siRNA transfections, chemotaxis studies, migration in microchannels, cell migration in 3D collagen matrices, cell migration in 3D collagen matrices, fluorescent microscopy with mages were acquired with an LSM700 confocal microscope (Carl Zeiss, Oberkochen, Germany).

The investigators unveiled that T cells from FAP patients carrying APC mutations display impaired adhesion and motility in constrained environments. They further dissected the cellular mechanisms underpinning these defects in APC-depleted CEM T cell line that recapitulate the phenotype observed in FAP T cells. They found that APC affects T cell motility by modulating integrin-dependent adhesion and cytoskeleton reorganization. Hence, APC mutations in FAP patients not only drive intestinal neoplasms, but also impair T cell migration, potentially contributing to inefficient antitumor immunity.

Marta Mastrogiovanni, MSc, PhD candidate and lead author or the study, said, “In order to move along blood vessel walls, cross them and reach the tumor to be infiltrated, healthy lymphocytes change their morphology. Something akin to a large adhesive foot, supported by the lymphocyte's cytoskeleton, grows longer in the direction of migration. This polarization is essential for movement in the right direction. In mutated lymphocytes, the microtubules making up the cytoskeleton are disorganized and there are fewer adhesion proteins. The cells lose their polarity and their 'muscles'.”

The authors concluded that their data provides the first evidence that APC orchestrates the coupling of cytoskeletal-mediated forces and integrin-dependent adhesion necessary for T cell migration as physiologically occurs across endothelial barriers, lymphoid organs, inflamed tissue and tumors. Consequently, APC defects may impair immune surveillance and effector functions of T cells, thus favoring tumorigenesis initiated by defects in epithelial cell differentiation in FAP patients. The study was published on April 13, 2022 in the journal Science Advances.

Related Links:
Institut Pasteur 
Logos Biosystems
Miltenyi Biotec
Carl Zeiss

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