<p>AVI file - 24K, BMMCs from fes+/+ and fes-/- mice were loaded with CellTracker green or CellTracker orange, respectively, prior to mixing and addition to fibronectin-coated coverslips with an SCF-embedded agarose drop. Time lapse microscopy was then performed for 8-18 hours</p>
Received: 10/11/2020 Accepted: 24/11/2020 Published: 30/11/2020
*For Correspondence: Mahtsabisa MG,
Department of Pharmacology, University of the Free State, Bloemfontein 9300, Republic of South Africa
E-mail: MatsabisaMG@ufs.ac.zy
Keywords: Potency, Somatic, Reprogramming, Transcription, Fibroblast, Epigenetics.
Abstract The interaction between the Programmed Death Ligand 1 (PD-L1) immune checkpoint on the tumor cell surface with the Programmed Death-1 (PD-1) receptor on cytotoxic T lymphocytes (CTLs) leads to CTL inactivation, thereby promoting tumor cell escape from adaptive immunity. We previously demonstrated that signaling by PD-L1/PD-1 is bidirectional and leads to activation of oncogenic pathways as well as drug resistance in tumor cells. We also have preliminary evidence that Immunity Related GTPase M, an important mediator of autophagy, is up-regulated by PD-1/PD-L1 reverse signaling. Autophagy is a well-established mechanism of drug resistance in cancer cells. This led us to hypothesize that PD-1/PD-L1 signaling induces drug resistance in tumor cells by up-regulating autophagy. The MEK/ERK and the PI3K/Akt signaling pathways are known to increase and decrease autophagy, respectively. Breast cancer cells exposed to rPD-1 showed a time dependent increase in extracellular signal–regulated kinase (ERK) activation and a decrease in protein kinase B (Akt) activation. Conversion of microtubule-associated protein light chain 3 (LC3)-I to LC3-II is a requirement for autophagosome formation and is a robust marker of autophagy. Exposure of human breast cancer cells to recombinant PD-1 (rPD-1) showed a time-dependent increase in LC-3 II. We are currently conducting additional studies to confirm that the activation of PD-L1 signaling in tumor cells up-regulates autophagy. These results provide evidence that PD-1/PD-L1 reverse signaling activates autophagy as a potential mechanism of cancer cell chemoresistance. (Supported by a grant from the Canadian Institutes of Health Research.) Citation Format: Lori M. Minassian, Shannyn K. MacDonald-Goodfellow, Peter Truesdell, Daniel Sanwalka, Andrew W. Craig, Madhuri Koti, D Robert Siemens, Charles H. Graham. Tumor cell drug resistance induced by the programmed death ligand 1 (PD-L1) immune checkpoint is associated with autophagy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3960. doi:10.1158/1538-7445.AM2017-3960
ABSTRACT Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disease, and patients with active or recurrent bone inflammation at multiple sites are diagnosed with chronic recurrent multifocal osteomyelitis (CRMO). The Chronic multifocal osteomyelitis (CMO) mouse model develops IL-1β-driven sterile bone lesions reminiscent of severe CRMO. The goal of this study was to evaluate the potential involvement of mast cells in CMO/CRMO. Here, we show that mast cells accumulate in inflamed tissues from CMO mice and that mast cell protease Mcpt1 can be detected in the peripheral blood. A transgenic model of connective tissue mast cell depletion (Mcpt5-Cre:Rosa26-Stopfl/fl-DTa) was crossed with CMO mice and the resulting mice (referred to as CMO/MC–) showed a significant delay in disease onset compared with age-matched CMO mice. At 5-6 months of age, CMO/MC– mice had fewer bone lesions and immune infiltration in the popliteal lymph nodes that drain the affected tissues. In bone marrow-derived mast cell cultures from CMO mice, cytokine production in response to the alarmin IL-33 was elevated compared with wild-type cultures. To test the relevance of mast cells to human CRMO, we tested serum samples from a cohort of healthy controls and from CRMO patients at diagnosis. Interestingly, mast cell chymase was elevated in CRMO patients as well as in patients with oligoarticular juvenile arthritis. Tryptase-positive mast cells were also detected in bone lesions from CRMO patients and patients with bacterial osteomyelitis. Together, our results identify mast cells as cellular contributors to bone inflammation in CMO/CRMO and provide rationale for further study of mast cells as therapeutic targets.
