Protein that triggers cancer metastasis could be new treatment target

Researchers from the City University of Hong Kong (CityU) identified a protein called lysyl hydroxylase 1 (LH1) that induces the migration of liver and pancreas cancer cells, leading to metastasis, according to an institutional press release.

Verified by in vitro and in vivo models, the findings were supported with clinical data and are promising for determining a new potential target for cancer treatment.

"Cancer metastasis is a complex process. Stiffness in tumors and the surrounding tissues is known to increase along with the tumor growth, which creates confined spaces or channel-like tracks of pores for tumor cell migration and metastasis in multiple cancer types. But the mechanism of this confined migration remains unclear," said Professor Michael Yang Mengsu, Vice-President, and Yeung Kin Man, Chair Professor of Biomedical Sciences at CityU, who led the cross-institutional research.

"We aim to deeply study the cancer metastasis mechanism and identify novel genes and proteins related to it."

Focusing on specific types of liver and pancreas cancers

Hepatocellular carcinoma (HCC), a type of liver cancer, is the most prevalent and the second leading cause of cancer-related deaths globally. Pancreatic ductal adenocarcinoma (PDAC), on the other hand, is another type of highly aggressive cancer that has a five-year survival rate of less than ten percent.

The research team chose these two cancer types as subjects for their study because they share the common characteristic of containing excessive extracellular matrix (ECM) deposition.

Professor Yang's team collaborated with the Second Affiliated Hospital of Chongqing Medical University (CQMU). To begin their analysis, they collected specimens from 153 patients with HCC and 63 patients with PDAC who had not undergone chemotherapy or radiotherapy before surgery. They also acquired human liver and pancreatic cancer cell lines from the National Institutes of Health in the U.S.

"The main challenge was to simulate the complex cancer microenvironment," stated Professor Yang. "But there is a lack of study models for cell migration in confined environment. So we developed a series of multidimensional platforms and 2D and 3D in vitro and in vivo models to comprehensively study the cell migration process."

LH1 is one of the most highly expressed proteins in HCC

The research team conducted a transcriptomic analysis using next-generation sequencing (NGS) and proteomic analysis using liquid chromatography-mass spectrometry on HCC tissues. They eventually discovered that LH1 is one of the most highly expressed proteins in HCC compared to the healthy tissue surrounding it.

The research team created multidimensional platforms and 2D and 3D in vitro and in vivo models to analyze cell migration. They utilized microfluidic chips for single and collective cell migration and varied the stiffness of hydrogels for 3D invasion assays to mimic the complex cancer microenvironment.

The researchers found that LH1 promoted the confined migration, speed, and invasion capacity of HCC and PDAC cells.

"The platforms and methods we developed provide a unique approach to study the confined migration of cancer cells," said Professor Yang.

"We demonstrated that LH1 promotes confined migration and metastasis of cancer cells by stabilizing SEPT2, and that high LH1 is associated with poor prognosis of HCC and PDAC patients. The findings are expected to provide a potential new target for cancer diagnosis and drug development."

The study was published in the journal Molecular Cancer.

Study Abstract:

Background: Excessive extracellular matrix deposition and increased stiffness are typical features of solid tumors such as hepatocellular carcinoma (HCC) and pancreatic ductal adenocarcinoma (PDAC). These conditions create confined spaces for tumor cell migration and metastasis. The regulatory mechanism of confined migration remains unclear.

Methods: LC–MS was applied to determine the differentially expressed proteins between HCC tissues and corresponding adjacent tissue. Collective migration and single cell migration microfluidic devices with 6 μm-high confined channels were designed and fabricated to mimic the in vivo confined space. 3D invasion assay was created by Matrigel and Collagen I mixture treat to adherent cells. 3D spheroid formation under various stiffness environment was developed by different substitution percentage GelMA. Immunoprecipitation was performed to pull down the LH1-binding proteins, which were identified by LC–MS. Immunofluorescent staining, FRET, RT-PCR, Western blotting, FRAP, CCK-8, transwell cell migration, wound healing, orthotopic liver injection mouse model and in vivo imaging were used to evaluate the target expression and cellular phenotype.

Results: Lysyl hydroxylase 1 (LH1) promoted the confined migration of cancer cells at both collective and single cell levels. In addition, LH1 enhanced cell invasion in a 3D biomimetic model and spheroid formation in stiffer environments. High LH1 expression correlated with poor prognosis of both HCC and PDAC patients, while it also promoted in vivo metastasis. Mechanistically, LH1 bound and stabilized Septin2 (SEPT2) to enhance actin polymerization, depending on the hydroxylase domain. Finally, the subpopulation with high expression of both LH1 and SEPT2 had the poorest prognosis.

Conclusions: LH1 promotes the confined migration and metastasis of cancer cells by stabilizing SEPT2 and thus facilitating actin polymerization.