Cancer control by adaptive immunity involves a number of defined death and clearance mechanisms. However, efficient inhibition of exponential cancer growth by T cells and interferon-γ (IFN-γ) requires additional undefined mechanisms that arrest cancer cell proliferation. Here we show that the combined action of the T-helper-1-cell cytokines IFN-γ and tumour necrosis factor (TNF) directly induces permanent growth arrest in cancers. To safely separate senescence induced by tumour immunity from oncogene-induced senescence, we used a mouse model in which the Simian virus 40 large T antigen (Tag) expressed under the control of the rat insulin promoter creates tumours by attenuating p53- and Rb-mediated cell cycle control. When combined, IFN-γ and TNF drive Tag-expressing cancers into senescence by inducing permanent growth arrest in G1/G0, activation of p16INK4a (also known as CDKN2A), and downstream Rb hypophosphorylation at serine 795. This cytokine-induced senescence strictly requires STAT1 and TNFR1 (also known as TNFRSF1A) signalling in addition to p16INK4a. In vivo, Tag-specific T-helper 1 cells permanently arrest Tag-expressing cancers by inducing IFN-γ- and TNFR1-dependent senescence. Conversely, Tnfr1(-/-)Tag-expressing cancers resist cytokine-induced senescence and grow aggressively, even in TNFR1-expressing hosts. Finally, as IFN-γ and TNF induce senescence in numerous murine and human cancers, this may be a general mechanism for arresting cancer progression.

The introduced [(68)Ga]NODAGA-RGD combines easy accessibility with high stability and good imaging properties making it an interesting alternative to the (18)F-labelled RGD peptides currently used for imaging α(v)β(3) expression.

Although T cells can be labeled for noninvasive in vivo imaging, little is known about the impact of such labeling on T-cell function, and most imaging methods do not provide holistic information about trafficking kinetics, homing sites, or quantification. Methods: We developed protocols that minimize the inhibitory effects of 64 Cupyruvaldehyde-bis(N4-methylthiosemicarbazone) ( 64 Cu-PTSM) labeling on T-cell function and permit the homing patterns of T cells to be followed by PET. Thus, we labeled ovalbumin (OVA) T-cell receptor transgenic interferon (IFN)-g-producing CD4 1 T (Th1) cells with 0.7-2.2 MBq of 64 Cu-PTSM and analyzed cell viability, IFN-g production, proliferation, apoptosis, and DNA double-strand breaks and identified intracellular 64 Cu accumulation sites by energy dispersive x-ray analysis. To elucidate the fate of Th1 cell homing by PET, 10 7 64 Cu-OVA-Th1 cells were injected intraperitoneally or intravenously into healthy mice. To test the functional capacities of 64 Cu-OVA-Th1 cells during experimental OVA-induced airway hyperreactivity, we injected 10 7 64 Cu-OVA-Th1 cells intraperitoneally into OVA-immunized or nonimmunized healthy mice, which were challenged with OVA peptide or phosphate-buffered saline or remained untreated. In vivo PET investigations were followed by biodistribution, autoradiography, and fluorescence-activated cell sorting analysis. Results: PET revealed unexpected homing patterns depending on the mode of T-cell administration. Within 20 min after intraperitoneal administration, 64 Cu-OVA-Th1 cells homed to the perithymic lymph nodes (LNs) of naive mice. Interestingly, intravenously administered 64 Cu-OVA-Th1 cells homed predominantly into the lung and spleen but not into the perithymic LNs. The accumulation of 64 Cu-OVA-Th1 cells in the pulmonary LNs (6.8 6 1.1 percentage injected dose per cubic centimeter [%ID/cm 3 ]) 24 h after injection was highest in the OVA-immunized and OVA-challenged OVA airway hyperreactivity-diseased littermates 24 h after intraperitoneal administration and lowest in the untreated littermates (3.7 6 0.4 %ID/cm 3 ). As expected, 64 Cu-OVA-Th1 cells also accumulated significantly in the pulmonary LNs of nonimmunized OVA-challenged animals (6.1 6 0.5 %ID/cm 3 ) when compared with phosphate-buffered saline-challenged animals (4.6 6 0.5 %ID/cm 3 ). Conclusion: Our protocol permits the detection of Th1 cells in single LNs and enables temporal in vivo monitoring of T-cell homing over 48 h. This work enables future applications for 64 Cu-PTSM-labeled T cells in clinical trials and novel therapy concepts focusing on T-cell-based immunotherapies of autoimmune diseases or cancer.