31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Tetraploidization or autophagy: The ultimate fate of senescent human endometrial stem cells under ATM or p53 inhibition

<p>Previously we demonstrated that endometrium-derived human mesenchymal stem cells (hMESCs) via activation of the ATM/p53/p21/Rb pathway enter the premature senescence in response to oxidative stress. Down regulation effects of the key components of this signaling pathway, particularly ATM and p53, on a fate of stressed hMESCs have not yet been investigated. In the present study by using the specific inhibitors Ku55933 and Pifithrin-α, we confirmed implication of both ATM and p53 in H₂O₂-induced senescence of hMESCs. ATM or p53 down regulation was shown to modulate differently the cellular fate of H₂O₂-treated hMESCs. ATM inhibition allowed H₂O₂-stimulated hMESCs to escape the permanent cell cycle arrest due to loss of the functional ATM/p53/p21/Rb pathway, and induced bypass of mitosis and re-entry into S phase, resulting in tetraploid cells. On the contrary, suppression of the p53 transcriptional activity caused a pronounced cell death of H₂O₂-treated hMESCs via autophagy induction. The obtained data clearly demonstrate that down regulation of ATM or p53 shifts senescence of human endometrial stem cells toward tetraploidization or autophagy.</p

Insulin receptor-related receptor as an extracellular alkali sensor

17sireservedThe insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH &gt;7.9. The alkali-sensing property of IRR is conserved in frog, mouse, and human. IRR activation is specific, dose-dependent and quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess.mixedDeyev, Igor E; Sohet, Fabien; Vassilenko, Konstantin P; Serova, Oxana V; Popova, Nadezhda V; Zozulya, Sergey A; Burova, Elena B; Houillier, Pascal; Rzhevsky, Dmitry I; Berchatova, Anastasija A; Murashev, Arkady N; Chugunov, Anton O; Efremov, Roman G; Nikol'Sky, Nikolai N; Bertelli, Eugenio; Eladari, Dominique; Petrenko, Alexander G.Deyev, Igor E; Sohet, Fabien; Vassilenko, Konstantin P; Serova, Oxana V; Popova, Nadezhda V; Zozulya, Sergey A; Burova, Elena B; Houillier, Pascal; Rzhevsky, Dmitry I; Berchatova, Anastasija A; Murashev, Arkady N; Chugunov, Anton O; Efremov, Roman G; Nikol'Sky, Nikolai N; Bertelli, Eugenio; Eladari, Dominique; Petrenko, Alexander G