CircHECTD1 Up-Regulates Mucin 1 to Accelerate Hepatocellular Carcinoma by Targeting miR-485-5p: A New Non-Coding RNA Mechanism

0
0
0

CircHECTD1 Up-Regulates Mucin 1 to Accelerate Hepatocellular Carcinoma by Targeting miR-485-5p: A New Non-Coding RNA Mechanism

Liver cancer is the fourth leading cause of cancer-related death worldwide, with hepatocellular carcinoma (HCC) making up 75–85% of cases. Despite advances in treatment, HCC’s high invasiveness and late diagnosis mean only 18% of patients survive five years. For decades, researchers have sought molecular targets to slow or stop this deadly disease—and a new study reveals how a circular RNA (circRNA) called circHECTD1 drives HCC progression by manipulating two key molecules: the oncogene mucin 1 (MUC1) and a tumor-suppressing microRNA (miRNA) called miR-485-5p.

The Players: MUC1, miR-485-5p, and circHECTD1

MUC1 is a glycoprotein normally found on epithelial cell surfaces. In cancer, it’s overexpressed, loses its polar structure, and fuels cell growth, migration, and survival. Previous work showed MUC1 is abundant in HCC tissues and cell lines, but how it’s regulated remained unclear—until this study, led by Qiao-Li Jiang, Shu-Jiong Feng, and colleagues from Tongde Hospital of Zhejiang Province, Hangzhou First People’s Hospital, and Zhejiang Cancer Hospital.

MiRNAs are short non-coding RNAs that “silence” target genes by binding to their messenger RNA (mRNA). miR-485-5p is known to suppress tumors in breast and gastric cancer, but its role in HCC was untested. CircRNAs, meanwhile, are closed-loop RNAs that act as “molecular sponges” for miRNAs, blocking their ability to regulate genes—a process called competing endogenous RNA (ceRNA).

The Study: How circHECTD1 Fuels HCC

The team first analyzed tissue samples from 15 HCC patients and found two critical patterns:

  1. MUC1 was overexpressed in tumors: HCC tissues had 75x more MUC1 mRNA than adjacent normal tissue (P < 0.001). Patients with high MUC1 levels lived 16 months less on average (58.7 vs. 75.2 months) than those with low MUC1—data supported by the The Cancer Genome Atlas (TCGA) database.
  2. miR-485-5p was downregulated: Tumors had 3x less miR-485-5p than normal tissue (P < 0.001). The two molecules were inversely correlated: higher MUC1 meant lower miR-485-5p.

Using bioinformatics (TargetScan) and luciferase reporter assays, the team confirmed miR-485-5p directly binds to MUC1’s mRNA. When they increased miR-485-5p in HepG2 HCC cells, MUC1 levels dropped by 63%—and when they blocked miR-485-5p, MUC1 jumped 3.9x. Functional experiments showed miR-485-5p suppresses HCC:

  • Inhibiting miR-485-5p doubled cell proliferation (73% vs. 41%) and tripled migration (102 vs. 46 cells) in MUC1-silenced HepG2 cells.
  • It also cut invasion by half (59 vs. 28 cells) and reduced apoptosis by 38% (22.6% vs. 36.3%).

Next, the team identified circHECTD1 as a miR-485-5p sponge using Starbase 2.0. CircHECTD1 was 3x more abundant in HCC tissues than normal tissue (P < 0.001), and its levels inversely correlated with miR-485-5p. Luciferase and RNA immunoprecipitation (RIP) assays proved circHECTD1 directly binds miR-485-5p: when circHECTD1 was silenced, miR-485-5p levels rose 4.2x, and MUC1 dropped by 63%. When circHECTD1 was overexpressed, miR-485-5p fell by 54%, and MUC1 jumped 4.3x.

The Mechanism: A ceRNA Network Drives HCC

The study’s key finding is a circHECTD1 → miR-485-5p → MUC1 axis:

  1. CircHECTD1 “sponges” (binds and blocks) miR-485-5p.
  2. With less miR-485-5p, MUC1 mRNA is not silenced—so MUC1 protein levels rise.
  3. High MUC1 promotes HCC by:
    • Increasing matrix metalloproteinases (MMP-2/9) (enzymes that break down tissue, enabling invasion).
    • Upregulating BCL2 (a protein that prevents apoptosis).
    • Downregulating BAX (a protein that triggers cell death).

When the team silenced circHECTD1 in HepG2 cells, proliferation dropped by 62%, migration by 64%, and invasion by 65%—effects reversed by blocking miR-485-5p. Apoptosis also doubled (45.8% vs. 3.4%), but fell back to 25.9% when miR-485-5p was inhibited.

What This Means for HCC Treatment

This is the first study to link circHECTD1, miR-485-5p, and MUC1 in HCC. The results suggest circHECTD1 could be a therapeutic target: blocking it would free miR-485-5p to silence MUC1, slowing tumor growth and spread. The team also notes MUC1’s role as a prognostic marker—high levels correlate with shorter survival—offering a new way to predict patient outcomes.

The Study’s Authors and Methods

The research was conducted by Qiao-Li Jiang, Shu-Jiong Feng, Zhu-Ying Yang, Qi Xu, and Shuang-Zhu Wang from three Chinese hospitals: Tongde Hospital of Zhejiang Province, Affiliated Hangzhou First People’s Hospital (Zhejiang University School of Medicine), and Zhejiang Cancer Hospital. They used:

  • Tissue samples: 15 HCC patients (10 hepatitis B-positive, 5 non-infectious) with matched normal tissue.
  • Cell lines: Normal liver (THLE-3) and HCC (HCCLM, MHCC97L, SMMC7721, Hep3B, HepG2) cells.
  • Assays: qRT-PCR (RNA levels), Western blot (protein levels), immunohistochemistry (tissue staining), luciferase reporters (RNA binding), Transwell (migration/invasion), flow cytometry (apoptosis), and RIP (RNA-protein interactions).

All experiments were repeated three times, with statistical significance set at P < 0.05.

Conclusion: A New Piece of the HCC Puzzle

Non-coding RNAs—once dismissed as “transcription noise”—are now recognized as critical regulators of cancer. This study adds circHECTD1 to the list of circRNAs driving HCC by manipulating miRNA-mRNA networks. For patients, the findings offer hope: targeting circHECTD1 or miR-485-5p could be a new way to tackle MUC1, a known oncogene. As researchers continue to unravel these networks, non-coding RNAs may become the next frontier in personalized HCC therapy.

Original study published in Chinese Medical Journal (2020) by Qiao-Li Jiang et al.
doi: https://doi.org/10.1097/CM9.0000000000000917

Was this helpful?

0 / 0