M. V. Sitkovskiĭ
Wendy A. Smith, Erin J. Cram, Graham B. Jones, Jorgen Kjaergaard
Date of Award
Doctor of Philosophy
Department or Academic Unit
College of Science. Department of Biology.
biology, immunology, cellular biology, adenosine receptors, immunotherapy, NK cells, pulmonary metastasis, T Cells
Cancer - Immunotherapy, Tumors - Treatment
The suppression of tumor-reactive T- and NK cells in the tumor microenvironment (TME) involves several functionally distinct mechanisms that include the modulation of immunological negative regulators, suppressor cells, and the secretion of soluble anti-inflammatory factors that allow tumors to escape immunosurveillance. In addition to these mainstream mechanisms of immunosuppression in the TME, Sitkovsky and co-authors have suggested that it is the tumor hypoxia-driven accumulation of extracellular adenosine and subsequent signaling by engagement of the cAMP-elevating A2 adenosine receptors on tumor-reactive effector T-7 or NK cells8 that is instrumental in aiding the process of tumor evasion. Here, we show that the reversal of hypoxia by breathing high oxygen (60%)-containing gas mixtures breaks tumor-induced hypoxia-adenosinergic suppression and improves the regression of MCA205 fibrosarcoma and B16 melanoma pulmonary metastases by adoptively transferred tumor-reactive T cells and by endogeneously developed anti-tumor T- and NK cells. We have demonstrated that breathing 60% oxygen i) increased oxygen levels in previously hypoxic tumor tissue; ii) decreased intratumoral extracellular adenosine levels; iii) prevented the inhibition of intratumoral infiltration and proliferation of tumor-reactive T cells and iv) enhanced immune-stimulating cytokines while decreasing negative regulators of the anti-tumor immunity. We propose that this novel mechanism is mediated by T- and NK cells and suggest hyperoxia is acting upstream and downstream of the same tumor-protecting pathway. These previously unappreciated immunoenhancing capabilities of supplemental oxygen clarify an important aspect of tumor biology and anti-tumor immunity and offer a conceptually novel medical use of supplemental oxygen.
In studies of A2A or A2B adenosine receptor gene-deficient mice, we found that A2A adenosine receptor (A2AR) deletion solitarily liberates endogenous CD8 T cell anti-tumor immunity against progressively growing weakly immunogenic MCA205 sarcomas. Analyses of the therapeutic efficacy of adoptively transferred A2AR-/-, A2BR-/- or A2AR-/-/A2BR-/- T cells from culture-activated tumor draining lymph nodes (TDLN) confirmed that immunosuppression in the TME was mediated by A2AR on CD8 tumor-reactive T cells. Of potential clinical significance, treatment with the synthetic, selective A2AR antagonist KW6002 mimicked A2AR gene-deletion in adoptive T cell immunotherapy against pulmonary metastases. This therapeutic benefit of A2AR antagonism was independent of the anatomical location of tumor growth since anti-tumor reactivity was also observed in the eradication of established intracranial tumors, resulting in mouse survival and the development of long-lasting tumor-specific memory. Importantly, antagonistic blockade of the A2AR on adoptively transferred T cells prevented the inhibition of anti-tumor effector functions, as reflected by the increased levels of IFN-γ secretion by tumor-infiltrating CD8 T cells.
Taken together, these data reveal the principle mechanisms of hypoxia-driven immunosuppression in the TME and offer a therapeutic solution in the selective antagonism of the A2AR or the use of supplemental oxygen to augment T cell-based immunotherapy. In addition, the data presented here survived rigorous critical review in preparation for clinical trials at the University of Miami Sylvester Cancer Center, where the treatment of lung cancer patients with cancer vaccines will be combined with breathing 40% to 60% oxygen and A2AR antagonism.
Stephen Matthew Hatfield
Hatfield, Stephen Matthew, "The anti-hypoxia-adenosinergic approach to the immunotherapy of cancer" (2011). Biology Dissertations. Paper 23. http://hdl.handle.net/2047/d20002120
Available for download on Friday, March 07, 2014
Click button above to open, or right-click to save.COinS