Background: Despite aggressive multimodal therapy, locally advanced and/or metastatic penile squamous cell carcinoma (SqCC) is associated with significant morbidity and mortality, indicating a need for new therapeutic options. Given the emerging clinical utility of immunotherapeutics, we sought to assess the incidence and potential clinical significance of PD-L1 expression in penile SqCC.Patients and methods: Using an anti-PD-L1 primary antibody (clone 5H1), immunohistochemistry was carried out on whole tumor sections from 37 patients with penile SqCC treated at our institution between 2005 and 2013. PD-L1positive tumors were defined as those with membranous staining in ≥5% of tumor cells. Association between PD-L1 expression and clinicopathologic parameters was examined using Fisher's exact test. Correlation between PD-L1 expression in primary tumors and matched metastases was assessed using the Spearman rank correlation coefficient (ρ). The difference in cancer-specific mortality between PD-L1-positive and -negative groups was examined using the log-rank test.Results: Twenty-three (62.2%) of 37 primary tumors were positive for PD-L1 expression, and there was strong positive correlation of PD-L1 expression in primary and metastatic samples (ρ = 0.72; 0.032 < P < 0.036). Primary tumor PD-L1 expression was significantly associated with usual type histology (P = 0.040) and regional lymph node metastasis (P = 0.024), as well as decreased cancer-specific survival (P = 0.011). Conclusions:The majority of primary penile SqCC tumors express PD-L1, which is associated with high-risk clinicopathologic features and poor clinical outcome. These data provide a rational basis for further investigation of anti-PD-1 and anti-PD-L1 immunotherapeutics in patients with advanced penile SqCC.

Clinical management of delayed healing or non-union of long bone fractures and segmental defects poses a substantial orthopaedic challenge. There are suggestions in the literature that bone healing may be enhanced by inhibiting the activities of T and B lymphocytes, but this remains controversial. To examine this matter in more detail, sub-critical-sized segmental defects were created in the femora of mice and it was assessed whether there might be a benefit from the administration of a Food and Drug Administration (FDA)-approved drug that blocks T cell activation (tacrolimus). Defects were stabilised using an internal plate. In certain groups of animals, 1 mg/kg or 10 mg/kg tacrolimus was delivered locally to the defect site for 3 or 7 d using an implanted osmotic pump with a silicon catheter directing drug delivery into the defect area. Healing was monitored by weekly X-ray and assessed at 12 weeks by mechanical testing, µCT and histology. Radiographic and histological evaluations revealed that 100 % of defects healed well regardless of tacrolimus dosage or duration. A comparison of healed C57BL/6 and Rag1−/− femora by µCT and ex vivo torsion testing showed no differences within mouse strains in terms of bone volume, tissue volume, bone volume/tissue volume ratio, shear modulus, torsional rigidity or torsional stiffness. These data failed to support an important role for tacrolimus in modulating the natural healing of segmental defects under those experimental conditions.