Deregulation of ubiquitin ligases is related to the malignant progression of human cancers. F-box only protein 22 (FBXO22), an F-box E3 ligase, is a member of the F-box protein family. However, the biological function of FBXO22 in HCC and the underlying molecular mechanisms are still unclear. In this study, we explored the role of FBXO22 in HCC and its mechanism of promoting tumor development. We examined the expression of FBXO22 in normal liver cell lines, HCC cell lines, HCC tissue microarrays and fresh specimens. The correlation between FBXO22 and clinical features was analyzed in a retrospective study of 110 pairs of HCC tissue microarrays. Univariate and multivariate survival analyses were used to explore the prognostic value of FBXO22 in HCC. At the same time, the correlation between the FBXO22 and p21 was also studied in HCC samples. Knock-down and overexpression experiments, CHX and Mg132 intervention experiments, ubiquitination experiments, rescue experiments and nude mouse xenograft models were used to determine the potential mechanism by which FBXO22 promotes tumorigenesis in vitro and in vivo. The expression of FBXO22 in HCC tissues was significantly higher than in normal liver tissues. The overall survival rate and disease-free survival time of patients with high expression of FBXO22 were significantly shorter than those of patients with low expression of FBXO22. The high expression of FBXO22 in HCC tissues were significantly correlated with serum AFP (p = 0. 003, Pearson’s chi-squared test), tumor size (p = 0. 019, Pearson’s chi-squared test) and vascular invasion (p = 0. 031, Pearson’s chi-squared test). Especially, Multivariate analysis showed that tumor size and the expression of FBXO22 were independent prognostic indicator of OS (95% CI: 1.077–5.157, P<0.05). Correlation analysis also showed that FBXO22 was negatively correlated with p21 in tissue microarrays (r = − 0.3788, P<0.001, Pearson correlation) and fresh specimens (r = − 0.4037, P<0.01, Pearson correlation). Moreover, both in vitro and in vivo experiments showed that knocking down FBXO22 expression could inhibit cell proliferation, while overexpression of FBXO22 promoted tumor formation. Furthermore, we identified that FBXO22 interacts with p21 by regulating protein stability and by influencing the ubiquitination process. A knockdown of FBXO22 decreased the ubiquitylation of p21, while overexpression enhanced it. This study uncovered a new mechanism by which FBXO22 functions as an oncogene in HCC pathogenesis and progression by mediating the ubiquitination and degradation of p21. It was also found that tumor size and the expression of FBXO22 were independent prognostic indicator of OS and the expression of FBXO22 and p21 was negatively correlated in clinical samples. Our findings present a new perspective for understanding the development of HCC, which may provide a new target for the treatment and management of this challenging cancer.

DEPTOR is an endogenous inhibitor of mTORC1 and mTORC2 that plays a vital role in the progression of human malignances. However, the biological function of DEPTOR in HCC metastasis and the underlying molecular mechanisms are still unclear. Western blot analysis and immunohistochemistry(IHC) were employed to examine DEPTOR expression in HCC cell lines and tissues. A series of in vivo and in vitro assays were performed to determine the function of DEPTOR and the possible mechanisms underlying its role in HCC metastasis. We found that DEPTOR was frequently overexpressed in HCC tissues, and its high expression was associated with high serum AFP levels, increased tumor size, vascular invasion and more advanced TMN and BCLC stage, as well as an overall poor prognosis. Functional experiments demonstrated that DEPTOR silencing inhibited the proliferation and mobility of HCC cells in vitro and suppressed tumor growth and metastasis of HCC cells in vivo. Accordingly, DEPTOR overexpression promoted the invasion and metastasis of HCC cells in vitro and in vivo, but had no effect on cell proliferation in vitro. Overexpression of DEPTOR induced EMT by snail induction. Conversely, knockdown of snail expression impaired the DEPTOR-induced migration, invasion and EMT of HCC cells. Furthermore, we found that the increase of snail expression by DEPTOR overexpression was due to an activation of TGF-β1-smad3/smad4 signaling possibly through feedback inhibition of mTOR. DEPTOR promotes the EMT and metastasis of HCC cells by activating the TGF-β1-smad3/smad4-snail pathway via mTOR inhibition. Therefore, targeting DEPTOR may be an ideal treatment strategy for inhibiting the growth and metastasis of HCC.

Background and Aims: Immune checkpoint inhibitors have revolutionized systemic HCC treatment. Nevertheless, numerous patients are refractory to immune checkpoint inhibitor therapy. It is currently unknown whether diet therapies such as short-term starvation (STS) combined with immune checkpoint inhibitors can be used to treat HCC. This study aimed to investigate whether STS could sensitize HCC tumors to immunotherapy. Approach and Results: STS was found to attenuate tumor progression by inducing tumor-associated macrophages (TAMs) to switch to an antitumoral phenotype, enhancing phagocytosis of tumor cells, and stimulating subsequent antitumor immunity of CD8 ⁺ T cells as demonstrated in 3 HCC mouse models, NCG mice, and Rag2-KO mice. Furthermore, STS combined with anti-programmed cell death 1/ligand 1 (anti-PD-1/L1) suppressed tumor progression, while the efficacy of PD-L1 was improved when combined with STS. Mechanistically, TAM-derived exosomal PD-L1 (exoPD-L1) impairs the efficacy of anti-PD-1/L1. STS attenuates exoPD-L1 secretion from TAM by regulating the fructose diphosphatase 1 (FBP1) /Akt/Rab27a axis. Modulating FBP1/Akt/Rab27a axis potentiates the anti-PD-L1 response using 2 liposomal delivery systems and macrophage adoptive transfer. Conclusions: This study describes the immunomodulatory effects of STS and provides a rationale for its application as an adjuvant in HCC immunotherapy.

Background and Aims: Lenvatinib is recognized as a first-line therapy for inoperable hepatocellular carcinoma (HCC) patients. Growing evidence indicates that the lenvatinib resistance can be acquired in HCC cells via kinase rewiring. Approach and Results: We established acquired lenvatinib resistance organoids and HCC cell lines. NIMA-related coiled-coil kinase 7 (NEK7) was identified as an HCC lenvatinib acquired resistance gene by kinase CRISPR–Cas9 genetic screen. Functional analyses demonstrate that NEK7 enhanced lenvatinib resistance in HCC and NEK7 knock down or knock out display the anti-tumor effects in acquired lenvatinib HCC cells and organoids. Mechanistically, NEK7 binds to EGFR, leading to the phosphorylation of EGFR (Endothelial growth factor receptor) specifically at the serine 1070 residue, which contributes to the activation of MAPK (Mitogen-activated protein kinase) and PI3K/AKT (Phosphoinositide 3-kinase/Akt) signaling pathways. Consistently, designed inhibitory peptides targeting domain from amino acids 979 to 1099 were proved to inhibit phosphorylation of EGFR S1070 site and therapeutically inhibit anti-tumor of acquired lenvatinib resistance HCC. Conclusions: Our results unveil insights into the acquired lenvatinib resistance mechanism that NEK7 phosphorylates EGFR at S1070 to promote acquired lenvatinib resistance in HCC. Export

Deng NING, Li JIANG*, Xiaoping CHEN, Chao WANG. Ann Hepatobiliary Pancreat Surg 2021;25:S387. https://doi.org/10.14701/ahbps.EP-188