Rarely Seen Compartment Syndrome of the Shoulder and Back: Diagnosis and Management

Compartment syndrome (CS) is a well-known surgical emergency with high morbidity including potential long-term disability and limb loss. The most important factor determining the degree of morbidity with CS is time to treatment; therefore, early diagnosis and surgery are vital. We present a patient who fell off his bicycle and sustained cervical spine fractures causing near complete quadriplegia. He was found by the road over 12 hours later, so his creatine phosphokinase (CPK) was trended and serial examinations were performed. We identified tight deltoid, trapezius, and latissimus compartments and brought him to the operating room for fasciotomies. Although lab values and compartment pressures can be helpful, they should not guide treatment. It is important to consider atypical sites for CS and complete a head to toe physical examination. Patients should proceed to the operating room if clinical suspicion exists for CS because of the morbidity associated with a missed diagnosis.

Identification of immunogenic peptide neoantigens expressed in sarcomas and their therapeutic potential

T cells recognize tumor neoantigens (TNag) in the context of MHC and eliminate cells which express these antigens, leaving those lacking immunodominant epitopes. Central to investigating tumor immunoediting is the ability to define immunogenic TNag. Differential aggretope index (DAI) is a measure of the difference in MHC binding affinity between mutated and unmutated peptides and has emerged as a highly efficient way of identifying immunogenic TNag. Our previous studies have demonstrated that in mice, TNag with a DAI >8 are considered immunogenic and elicit T cells that lead to the tumor elimination. Thus, tumors expressing TNag of DAI >8 are only found in immunodeficient mice. Given these observations, we investigated the mutational burden and immune phenotype of bone proximal tumors in 122 patients. Tumors included are of bone, surrounding tissue and distal metastases, and were analyzed by flow cytometry, whole exome and TCR-Vβ sequencing. We hypothesized that tumors with high DAI TNag would be immunoedited in patients with robust T cell responses as measured by T cell clonality. Similar to observations in mice, this correlation was only observed in TNag with DAI >8. In contrast, there was no correlation between DAI and frequency of CD8 TILs indicating that the repertoire of TILs is a better indicator of immune reactivity than their frequency. Among tumor types analyzed, osteosarcomas were the least immunoedited, suggesting greatest potential for immunotherapy. We confirmed this potential in a mouse model of osteosarcoma, where we show that therapeutic HSP-mediated responses, augmented by PD-1 blockade, conferred the best survival. These studies provide compelling rationale for novel immunotherapies in patients with osteosarcoma.

Supported by NIH R01 CA233803 and an HCC UPMC Developmental Award

An Immunotherapeutic CD137 Agonist Releases Eomesodermin from ThPOK Repression in CD4 T Cells

Agonists to the TNF/TNFR costimulatory receptors CD134 (OX40) and CD137 (4-1BB) elicit antitumor immunity. Dual costimulation with anti-CD134 plus anti-CD137 is particularly potent because it programs cytotoxic potential in CD8⁺ and CD4⁺ T cells. Cytotoxicity in dual-costimulated CD4 T cells depends on the T-box transcription factor eomesodermin (Eomes), which we report is induced via a mechanism that does not rely on IL-2, in contrast to CD8⁺ CTL, but rather depends on the CD8 T cell lineage commitment transcription factor Runx3, which supports Eomes expression in mature CD8⁺ CTLs. Further, Eomes and Runx3 were indispensable for dual-costimulated CD4 T cells to mediate antitumor activity in an aggressive melanoma model. Runx3 is also known to be expressed in standard CD4 Th1 cells where it fosters IFN-γ expression; however, the CD4 T cell lineage commitment factor ThPOK represses transcription of Eomes and other CD8 lineage genes, such as Cd8a Hence, CD4 T cells can differentiate into Eomes⁺ cytotoxic CD4⁺CD8⁺ double-positive T cells by terminating ThPOK expression. In contrast, dual-costimulated CD4 T cells express Eomes, despite the continued expression of ThPOK and the absence of CD8α, indicating that Eomes is selectively released from ThPOK repression. Finally, although Eomes was induced by CD137 agonist, but not CD134 agonist, administered individually, CD137 agonist failed to induce CD134^-/- CD4 T cells to express Eomes or Runx3, indicating that both costimulatory pathways are required for cytotoxic Th1 programming, even when only CD137 is intentionally engaged with a therapeutic agonist.