Background: Hepatocellular carcinoma (HCC) is the most common primary liver cancer and is a highly vascularized solid tumor. Angiopoietin-2 (ANGPT2) has been described as an attractive target for antiangiogenic therapy. Exosomes are small extracellular vesicles secreted by most cell types and contribute to cell-to-cell communication by delivering functional cargo to recipient cells. The expression of ANGPT2 in tumor-derived exosomes remains unknown. Methods: We detected the ANGPT2 expression in HCC-derived exosomes by immunoblotting, enzyme-linked immunosorbent assay and immunogold labeling, then observed exosomal ANGPT2 internalization and recycling by confocal laser scanning microscopy, co-immunoprecipitation and immunoblotting. We used two HCC cell lines (Hep3B and MHCC97H) to overexpress ANGPT2 by lentivirus infection or knockdown ANGPT2 by the CRISPR/Cas system, then isolated exosomes to coculture with human umbilical vein endothelial cells (HUVECs) and observed the angiogenesis by Matrigel microtubule formation assay, transwell migration assay, wound healing assay, cell counting kit-8 assay, immunoblotting and in vivo tumorigenesis assay. Results: We found that HCC-derived exosomes carried ANGPT2 and delivered it into HUVECs by exosome endocytosis, this delivery led to a notable increase in angiogenesis by a Tie2-independent pathway. Concomitantly, we observed that HCC cell-secreted exosomal ANGPT2 was recycled by recipient HUVECs and might be reused. In addition, the CRISPR-Cas systems to knock down ANGPT2 significantly inhibited the angiogenesis induced by HCC cell-secreted exosomal ANGPT2, and obviously suppressed the epithelial-mesenchymal transition activation in HCC. Conclusions: Taken together, these results reveal a novel pathway of tumor angiogenesis induced by HCC cell-secreted exosomal ANGPT2 that is different from the classic ANGPT2/Tie2 pathway. This way may be a potential therapeutic target for antiangiogenic therapy.

Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) can induce rapid hypertrophy of the liver remnant. However, with a background of liver cirrhosis or other chronic liver diseases, patients with a huge hepatocellular carcinoma (HCC) may sometimes face insufficiency of hepatocellular regeneration after associating liver partition and portal vein ligation for staged hepatectomy (ALPPS). Herein, we report a 56-year-old male with a vast HCC (13.3 × 8.5 × 13 cm) whose ratio of the future liver remnant (FLR)/standard liver volume (SLV) was 28.7% when the disease was first diagnosed. Inadequate hypertrophy of FLR was shown in postoperative volumetric assessment a month after stage I ALPPS. After multidisciplinary team discussion (MDT), the patient was decided to follow three courses of hepatic arterial infusion chemotherapy (HAIC) with oxaliplatin, fluorouracil, and leucovorin (FOLFOX4). The last HAIC was performed together with transhepatic arterial embolization (TAE). Finally, ratio of the FLR/SLV increased from 28.7% to 40% during three-month intervals, meeting the requirements of the surgery. Stage II ALPPS, right trisectionectomy, was then successfully performed. There was no recurrence at half years of follow-up. In our case, HAIC seems to be more potent than transcatheter arterial chemoembolization (TACE) in maintaining the hyperplasia of the liver remnant, reducing tumor load, and preventing tumor progression in patients with a large HCC during ALPPS procedure. HAIC, following the first step of ALPPS, a pioneering treatment modality aiming for inadequate hypertrophy of FLR induced by ALPPS, could be an alternative procedure for patients with a vast HCC in clinical practice.