Summary: Osteosarcoma is the most common bone cancer in children and adolescents. Although 70% of patients with localized disease are cured with chemotherapy and surgical resection, patients with metastatic osteosarcoma are typically refractory to treatment. Numerous lines of evidence suggest that cytotoxic T lymphocytes (CTLs) limit the development of metastatic osteosarcoma. We have investigated the role of PD-1, an inhibitory TNFR family protein expressed on CTLs, in limiting the efficacy of immune-mediated control of metastatic osteosarcoma. We show that human metastatic, but not primary, osteosarcoma tumors express a ligand for PD-1 (PD-L1) and that tumor-infiltrating CTLs express PD-1, suggesting this pathway may limit CTLs control of metastatic osteosarcoma in patients. PD-L1 is also expressed on the K7M2 osteosarcoma tumor cell line that establishes metastases in mice, and PD-1 is expressed on tumor-infiltrating CTLs during disease progression. Blockade of PD-1/PD-L1 interactions dramatically improves the function of osteosarcoma-reactive CTLs in vitro and in vivo, and results in decreased tumor burden and increased survival in the K7M2 mouse model of metastatic osteosarcoma. Our results suggest that blockade of PD-1/PD-L1 interactions in patients with metastatic osteosarcoma should be pursued as a therapeutic strategy.

Rationale Vulnerability to alcoholism is determined by many factors, including the balance of pleasurable vs. aversive alcohol-induced sensations: pleasurable sensations increase drinking, aversive sensations reduce it. Both female sex and adolescent age are associated with fewer use-limiting effects of ethanol and more rapid development of alcohol abuse. Objectives This study assessed voluntary drinking and the aversive effects of alcohol in adolescent and adult male and female rats, to determine whether these measures are inversely related across the sexes and development. Methods Voluntary drinking of 20% ethanol in an every-other-day (EOD) availability pattern and the full dose-response relationship of ethanol CTA were assessed in male and female adolescent and adult rats. Results CTA was sex-specific in adult but not adolescent rats, with adult females exhibiting less aversion. Voluntary ethanol consumption varied according to age and interindividual differences in consumption patterns but was not sex-specific. Adolescents initially drank more than adults, exhibited greater day-to-day variation in consumption, were more susceptible to the alcohol deprivation effect, and took longer to establish individual differences in consumption patterns. Conclusions These results show that the evolution of drinking patterns differs in adolescents and adults. While a small cohort of adults establish high consumption patterns quickly, most adolescents drink at high levels initially and show marked deprivation-induced increases, but a significant percentage reduce intake as they become adult. High drinking adolescents do not ramp up like adults, but maintain adolescent drinking patterns into adulthood. Sex differences were not observed in EOD drinking during either adolescence or adulthood.