Professor Wu Qiao's team revealed a new mechanism for hepatic stellate cell exoexohexohrokinase HK1 to accelerate the process of liver cancer

Hepatocellular carcinoma (HCC) is the most common hepatic malignancy, and more than 80% of clinical liver cancers are developed from liver fibrosis or cirrhosis, suggesting that liver fibrosis can directly promote the development
of liver cancer.
The key node of liver fibrosis is the activation
of hepatic stellate cells (HSCs).
HSCs are liver-specific mesenchymal cells that make up about 10%
of the total number of cells in the entire liver.
HSCs in a healthy liver are at rest, and the cells are rich in vitamin A lipid droplets; When the liver is fibrotic, HSCs turn into an active state, and cells proliferate in large quantities, showing the characteristics
of upregulation of α-smooth actin (α-SMA) expression and increased secretion of extracellular matrix.

Extracellular vesicles (EVs) are membranous vesicle structures released by cells into the extracellular matrix, containing proteins, lipids, nucleic acids, metabolites and other components
.
As an important communication tool between cells, EVs are widely involved in physiological and pathological processes
.
On May 28, 2020, Professor Wu Qiao's research group published a paper in Molecular Cell to elucidate hepatocellular carcinoma cells through the extracellular vesicle exocrine metabolism enzyme PKM2, inducing monocytes to differentiate into M2-like macrophages to promote the process of
liver cancer.
EVs as intercellular communication tools in tumor cells and stromal cells for bidirectional transmission, hepatocellular carcinoma cells through extracellular vesicle exocries to reshape the tumor stromal cell microenvironment to accelerate tumor progression, and liver fibrosis process of stromal cells through extracellular vesicles to regulate the development of liver cancer is not
clear.

On October 3, 2022, Professor Wu Qiao's research group published a research paper
entitled "HK1 from hepatic stellate cell-derived extracellular vesicles promotes progression of hepatocellular carcinoma" on Nature Metabolism Online 。 The study elucidated that in the process of liver fibrosis, TGF-β induce palmitoacylation modification of hexokinase HK1 in HSCs to promote the exocrism of HK1 through extracellular vesicles, while hepatocellular cancer cells hijack extracellular vesicles HK1 derived from fibrotic HSCs to enhance their own glycolysis ability to promote the proliferation of liver cancer cells; In addition, it was found that the small molecule compound PDNPA blocks the HK1 exocrion induced by TGF-β by targeting the nuclear receptor Nur77, thereby inhibiting the liver cancer process and revealing the new function
of PDNPA to inhibit HK1 exocris.

The researchers extracted the HSCs extracellular vesicles in the resting state and the activated state, respectively, and analyzed them by protein quantitative mass spectrometry to find potential cancer-promoting proteins
in the vesicles.
By comparing the changes in the exoprotein profile before and after the activation of HSCs, it was found that after the activation of HSCs, the protein hexokinase HK1 associated with the metabolic pathway was one of
the most obvious proteins.
Further research found that in the process of liver fibrosis, the fibrotic cytokine TGF-β promotes its transport from mitochondria to the cytoplasmic membrane by inducing palmitoylation of HK1, and is sorted into lEVs (large EVs) by TSG101-dependent and then exocred
.
The HK1 palmitoylation process is closely related
to the expression of TGF-β depalmitase ABHD17B.

By analyzing clinical liver cancer single-cell data and CCLE databases, the researchers found that hepatocellular carcinoma cells were low-expressing or even non-expressing HK1
.
However, hepatocellular cancer cells increase their own HK1 levels by hijacking the lEV HK1 exotic of HSCs, which in turn increases the level of glycolysis in hepatocellular carcinoma cells to promote tumor proliferation
.
The researchers further validated the HSCs-derived lEV HK1 to promote liver cancer progression
in mice through a series of mouse models, including a liver in situ transplant tumor model, a lung metastasis model of liver cancer cells, and a DEN/CCl₄- or HFD/STZ-induced primary liver cancer model.

(a) The HK1 exocroscopic changes in activated HSCs extracellular vesicles are located at the forefront
.
(b) Liver cancer absorbs extracellular vesicles
derived from DiI-labeled HSCs.
(c) End-vein injection of lEV HK1 promotes the process of
liver cancer.
(d) The compound PDNPA targets the Nur77 ligand binding domain (LBD) to form a steric hindrance to inhibit the binding
of Akt to Nur77.
(e) PDNPA targets Nur77 within HSCs to inhibit liver cancer processes
.

The nuclear receptor Nur77 has been reported to inhibit the TGF-β-induced fibrosis process
.
In this study, the researchers further found that Nur77 transcriptionally activates the expression level of the ABHD17B gene, which in turn inhibits the palmitoylation modification and exocrality
of HK1.
However, during fibrosis, TGF-β induce protein kinase Akt phosphorylation of Nur77 in HSCs leading to its degradation, thereby losing the ability
to regulate the expression of depalmitase ABHD17B.
Based on this, blocking the binding of Nur77 and Akt may avoid Nur77 degradation and ensure that Nur77 inhibits HK1 exocrion
through ABHD17B.
Through screening, the researchers found from the laboratory-constructed targeted Nur77 compound library that the small molecule compound PDNPA can bind to the Nur77 ligand binding domain, thereby forming a potential barrier to block Akt binding to the Nur77 ligand binding domain, thereby greatly improving the expression level of Nur77 and inhibiting the exocrism
of HK1 during fibrosis.
Transgenic mice that specifically knock out Nur77 within HSCs further validate a new pathway
in which the compound PDNPA inhibits the development of liver cancer by targeting Nur77.

In summary, this paper elucidated a new mechanism by which liver fibrosis promotes the process of liver cancer that has not been reported, and screens for the potential small molecule compound PDNPA to inhibit the liver cancer process
by blocking the HK1 exocrality in HSCs.

Metabolic reprogramming is one of the important features of tumors, and tumor cells meet rapidly proliferating material and energy needs
by reshaping their own metabolism.
HKs family proteins have been found to be expressed differently in hepatocytes and hepatocellular carcinoma cells
.
Hepatocellular cancer cells usually express the HK2 subtype with high affinity for glucose and are considered potential therapeutic targets for
liver cancer.
The HK1 subtype, which has the highest glucose affinity, is almost non-transcription in liver cancer cells, and its function has long been neglected
in liver cancer.
The study found that hepatocellular cancer cells can hijack the HK1 exogenous of HSCs, which can not only strengthen the glycolysis level of tumor cells, but also ensure the utilization of glucose by tumor cells under low glucose concentration conditions to adapt to the lack of nutrition in tumor tissues in the development of liver cancer
.
Although HK2 is considered an ideal target for the treatment of the ^HK1-HK2+ tumor type, the study suggests that combining HK1 with extracellular vesicle HK1, which targets the tumor's own sources of HK2 and HSCs, would be a more ideal treatment strategy
for liver cancer 。 At the same time, Robert F.
Schwabe, a leading expert in the field of hepatic stellate cell research, published a review article on this study (Liver cancer metabolism: a hexokinase from the stars" in the journal Nature Metabolism at the same time, pointing out that the joint targeting of HK1 and HK2 will be used as a new protocol
to target liver cancer metabolism.

The co-first authors of the paper are postdoctoral students Chen Qitao, doctoral students Zhang Zhiyuan and Huang Qiaoling, Professor Chen Hangzi, and co-corresponding authors are Professor Wu Qiao and Professor
Chen Hangzi.
The work was strongly supported
by Professor Wang Xiaomin and Associate Professor Zhao Wenxiu of Zhongshan Hospital affiliated to Xiamen University, researcher Hu Junhao of the Interdisciplinary Research Center of Biology and Chemistry of the Chinese Academy of Sciences, and Professor Li Guang of the College.

Original link: article link: Wu Qiao Research Group)