EZH2 is a key component of hepatoblastoma tumor cell growth.

BACKGROUND: Enhancer of zeste homolog 2 (EZH2) catalyzes the trimethylation of histone H3 at lysine 27 via the polycomb recessive complex 2 (PRC2) and plays a time-specific role in normal fetal liver development. EZH2 is overexpressed in hepatoblastoma (HB), an embryonal tumor. EZH2 can also promote tumorigenesis via a noncanonical, PRC2-independent mechanism via proto-oncogenic, direct protein interaction, including ß-catenin. We hypothesize that the pathological activation of EZH2 contributes to HB propagation in a PRC2-independent manner. METHODS AND RESULTS: We demonstrate that EZH2 promotes proliferation in HB tumor-derived cell lines through interaction with ß-catenin. Although aberrant EZH2 expression occurs, we determine that both canonical and noncanonical EZH2 signaling occurs based on specific gene-expression patterns and interaction with SUZ12, a PRC2 component, and ß-catenin. Silencing and inhibition of EZH2 reduce primary HB cell proliferation. CONCLUSIONS: EZH2 overexpression promotes HB cell proliferation, with both canonical and noncanonical function detected. However, because EZH2 directly interacts with ß-catenin in human tumors and EZH2 overexpression is not equal to SUZ12, it seems that a noncanonical mechanism is contributing to HB pathogenesis. Further mechanistic studies are necessary to elucidate potential pathogenic downstream mechanisms and translational potential of EZH2 inhibitors for the treatment of HB.

Indocyanine green is a sensitive adjunct in the identification and surgical management of local and metastatic hepatoblastoma.

BACKGROUND: Hepatoblastoma is the most common primary pediatric liver malignancy. Indocyanine green (ICG) has been described as an adjunct to resection in small series. Its utility remains undefined in larger cohorts. METHODS: Records for 29 patients diagnosed with hepatoblastoma who received ICG prior to surgical resection from 2017 to 2020 at a single institution were retrospectively reviewed. The primary outcome was correlation between intraoperative ICG-avidity and histologic presence of hepatoblastoma. A secondary outcome included the histologic margin designation for resected liver specimens. RESULTS: ICG sensitivity was 91% for 120 resected thoracic specimens from 21 patients. Specificity was 57%. In 10% of operations, HB-positive specimens were resected solely on ICG-avidity. In an additional 40% of cases, ICG assisted in localizing a preoperatively diagnosed lesion. ICG sensitivity during thoracotomy and thoracoscopic surgery was 95 and 74%, respectively; primary and relapsed disease demonstrated sensitivity of 94 and 73%, respectively. Sensitivity was 92% for 25 resected liver specimens from nine patients with all parenchymal margins grossly negative for disease. Four multifocal lesions were identified with two resected solely by ICG-avidity. CONCLUSIONS: ICG is a sensitive adjunct for identifying local and metastatic hepatoblastoma, including lesions not visualized on preoperative imaging, and delineating margins during liver resection. False positives limit specificity; however, there were no adverse outcomes from additional resections. We noted that thoracoscopic surgery can be completed safely in patients with less significant disease burden, and conversion to thoracotomy, if necessary, is straightforward.

Surgical management of locally-advanced and metastatic hepatoblastoma.

Advanced stage hepatoblastoma, including both locally advanced primary tumors as well as metastatic disease, poses unique clinical challenges. Despite substantial advances in chemotherapeutics, surgical extirpation remains the mainstay of cure for this tumor. Locally advanced tumors that involve multiple hepatic lobes and/or invade significant vascular structures can be managed either by complex hepatic resections or liver transplantation. We review the indications, roles, and outcomes of these surgical approaches as well as those for the resection of pulmonary metastases.