β-catenin/CBP activation of mTORC1 signaling promotes partial epithelial-mesenchymal states in head and neck cancer

Head and neck cancers, which include oral squamous cell carcinoma (OSCC) as a major subsite, exhibit cellular plasticity that includes features of an epithelial-mesenchymal transition (EMT), referred to as partial-EMT (p-EMT). To identify molecular mechanisms contributing to OSCC plasticity, we performed a multiphase analysis of single cell RNA sequencing (scRNAseq) data from human OSCC. This included a multiresolution characterization of cancer cell subgroups to identify pathways and cell states that are heterogeneously represented, followed by casual inference analysis to elucidate activating and inhibitory relationships between these pathways and cell states. This approach revealed signaling networks associated with hierarchical cell state transitions, which notably included an association between β-catenin-driven CREB-binding protein (CBP) activity and mTORC1 signaling. This network was associated with subpopulations of cancer cells that were enriched for markers of the p-EMT state and poor patient survival. Functional analyses revealed that β-catenin/CBP induced mTORC1 activity in part through the transcriptional regulation of a raptor-interacting protein, chaperonin containing TCP1 subunit 5 (CCT5). Inhibition of β-catenin-CBP activity through the use of the orally active small molecule, E7386, reduced the expression of CCT5 and mTORC1 activity in vitro, and inhibited p-EMT-associated markers and tumor development in a murine model of OSCC. Our study highlights the use of multiresolution network analyses of scRNAseq data to identify targetable signals for therapeutic benefit, thus defining an underappreciated association between β-catenin/CBP and mTORC1 signaling in head and neck cancer plasticity.

Team physician #4. Avulsion fracture of the distal tibial epiphysis in skeletally immature athletes (juvenile Tillaux fracture)

Adolescent athletic injuries are special in that they differ from those of the skeletally mature athlete in several respects. The physis is weaker than the ligaments, so that the typical mechanism of injury, which might be expected to result in a syndesmosis sprain of the ankle in adults with subsequent tearing of the ligaments, frequently causes an epiphyseal avulsion in children. The potential for leg length discrepancy and growth aberrations exists only if a significant amount of growth remains in the unfused epiphysis. The juvenile Tillaux fracture of the anterolateral distal tibial epiphysis is rare because it requires a specific mechanism of injury of dorsiflexion and external rotation at a time when the tibial epiphysis is fused medially but open laterally. We have also noted in these injuries a tear of the interosseous ligament, which has not previously been stressed in the literature. Intraoperative findings have helped to clarify the pathoanatomy and mechanism of injury. Anatomic reduction is necessary to prevent posttraumatic sequelae.

Team physician #2. Peroneus brevis transfer for Achilles tendon rupture in athletes

We feel peroneus brevis transfer is especially advantageous for patients interested in sports. We have used this technique in 55 athletes, and to date there have been no re-ruptures (Table 1). Two patients had mild superficial wound problems which did not affect the end result. This method has advantages in comparison with nonoperative treatment and other operative techniques. The danger of re-rupture is avoided and loss of strength minimized because the tendon transfer adds power to the injured triceps. In addition, the proximal retracted triceps is restored to length and securely repaired under physiological tension. Postoperative immobilization in a short leg cast at a right angle plus early weightbearing facilitate rehabilitation. A prolonged period of rehabilitation requiring many months of treatment has not been necessary. The extended rehabilitation and prolonged incapacity necessary to recover from immobilization in the plantarflexed position have been avoided. Early weightbearing helps prevent calf weakness and atrophy. Transferring the peroneal tendon has not resulted in any biomechanical functional imbalance to the foot.

Achilles tendon ruptures--peroneus brevis transfer

Peroneus brevis tendon transfer has been utilized in 40 individuals during the last 13 years. All cases consisted of complete Achilles tendon ruptures. In 34 cases the rupture was in the distal one-third of the tendon substance, in four cases bony avulsion of the calcaneal tuberosity occurred, and in two cases there was a diffuse tear in the proximal two-thirds of the tendon near the musculotendinous junction. The middle-aged athlete sustained the majority of these injuries during sports. Eleven patients were less than 30 years old, 23 patients were 30 to 40 years old, and six were over 40 years old. Five patients had reruptures that involved prior nonoperative treatment of cast immobilization, and one had undergone simple direct suture. This repair has been used in acute, chronic, and recurrent ruptures of the tendoachillis. Thirty-three patients presented within 1 week of injury, and seven after more than 1 week. A. Perez Teuffer personally described the preferred technique in 1971 and subsequently published in 1978. The transfer of the peroneus brevis is combined with a direct end-to-end suture of the triceps surae tendon that allows a secure reconstruction with the foot at a right angle. The peroneus brevis tendon is detached from the base of the fifth metatarsal and then tunnelled through the distal Achilles tendon stump. The distal portion of the tendon transfer is then drawn proximally along the medial calcaneal tendon border. The proximal triceps surae tendon is pulled distally and secured to the peroneal tendon.(ABSTRACT TRUNCATED AT 250 WORDS)

Anterolateral dislocation of the head of the fibula in sports

Traumatic anterolateral dislocation of the fibular head is an uncommon sports injury which is easily overlooked. Seventeen cases have been collected during private practice over the years. The typical mechanism of injury is a fall on the affected flexed knee with the leg adducted under the body and the ankle inverted. On physical examination there is an obvious bony prominence laterally of the fibular head and varying disability with activities; there is no significant effusion or signs of internal knee derangement or instability. Comparison identical radiographic views are necessary to confirm the diagnosis: on the anteroposterior view the fibular head is displaced laterally and the proximal interosseous space is widened; on the lateral view there is a greater overlap of the fibula on the tibia on the affected side. Peroneal nerve and ankle injuries can occur concomitantly with anterolateral proximal tibiofibular dislocation. Treatment options are closed or open reduction acutely and local strapping or fibular head resection for chronic cases based upon time of presentation and disability.