miR-296-5p Functions as a Potential Tumor Suppressor in Human Osteosarcoma by Targeting SND1

Osteosarcoma (OS)—the most common primary malignant bone tumor—strikes hardest in children and adolescents, with 60% of cases diagnosed between ages 10 and 20. While neoadjuvant chemotherapy has lifted 5-year survival rates for localized OS to 60% (up from 20% in the 1970s), patients with metastatic or recurrent disease still face a grim 20% survival rate. Chemoresistance and metastasis remain major roadblocks, leaving researchers desperate for new targets to fight this aggressive cancer.

Enter microRNAs (miRNAs)—tiny, non-coding RNAs (18–25 nucleotides long) that act as molecular “switches” to regulate gene expression. By binding to the 3′-untranslated region (3′-UTR) of target genes (the part that controls protein production without coding for it), miRNAs can turn genes on or off. Over half of miRNA genes sit in chromosome “fragile sites” linked to tumor mutations, making them key players in cancer development.

For years, scientists have studied how miRNAs drive or suppress tumors. Now, a 2021 study by Ya-Zeng Huang (Second Affiliated Hospital of Soochow University), Jun Zhang (Zhejiang Provincial People’s Hospital), and colleagues sheds light on one miRNA—miR-296-5p—and its role in osteosarcoma. Published in the Chinese Medical Journal, the research suggests miR-296-5p may act as a tumor suppressor by targeting a pro-cancer gene called SND1 (staphylococcal nuclease and tudor domain containing 1).

What the Researchers Did

The team focused on two questions:

Is miR-296-5p differently expressed in osteosarcoma?
How does it affect tumor cell growth, migration, and invasion?

They used:

Clinical samples: 45 pairs of osteosarcoma tissues and adjacent normal bone.
Cell lines: Four OS cell lines (HOS, MG63, U-2OS, Saos-2) and normal human osteoblasts (HOB) for comparison.
Assays: Quantitative reverse transcription PCR (qRT-PCR) to measure gene expression, MTT assays for cell proliferation, transwell tests for migration/invasion, and dual-luciferase assays to confirm direct gene targeting.

All patients gave informed consent, and the study was approved by the Zhejiang Provincial People’s Hospital ethics committee.

Key Findings: miR-296-5p Fights Osteosarcoma by Targeting SND1

The results painted a clear picture:

1. miR-296-5p is downregulated in osteosarcoma

qRT-PCR showed miR-296-5p levels were 3x lower in OS tissues than normal bone (average: 0.618 vs. 1.802). The same pattern held in OS cell lines—all had far less miR-296-5p than healthy osteoblasts.

2. Boosting miR-296-5p slows tumor growth and spread

When the team “overexpressed” miR-296-5p in HOS and Saos-2 cells (using genetic tools to increase its levels), the cells:

Grew 50% slower (MTT assay).
Migrated and invaded 30–40% less (wound-healing and transwell tests).

In short: More miR-296-5p = less aggressive cancer cells.

3. SND1 is miR-296-5p’s direct target—and it’s overactive in OS

The researchers used bioinformatics (TargetScan) to predict miR-296-5p’s targets. They landed on SND1, a gene known to drive proliferation and metastasis in other cancers (breast, liver, glioma).

Tests confirmed the link:

SND1 is overexpressed in OS: Western blotting and immunohistochemistry (IHC) showed higher SND1 protein levels in OS tissues and cell lines than normal controls.
Negative correlation: The more miR-296-5p a tumor had, the less SND1 it expressed (Spearman correlation analysis).
Direct binding: A dual-luciferase assay proved miR-296-5p attaches to SND1’s 3′-UTR. When the team mutated this binding site, miR-296-5p could no longer block SND1.

4. SND1 overexpression reverses miR-296-5p’s effects

To confirm SND1 is the “key” miR-296-5p targets, the team added mutated SND1 (resistant to miR-296-5p) to cells with high miR-296-5p. The result? The cancer cells resumed growing and spreading—undoing the miR’s tumor-suppressing effects.

What This Means for Osteosarcoma Treatment

This study adds two critical pieces to the osteosarcoma puzzle:

miR-296-5p as a tumor suppressor: Low levels of this miRNA may let OS cells grow unchecked. Replacing miR-296-5p (e.g., with synthetic miRNAs) could be a new treatment strategy.
SND1 as a pro-cancer driver: Since SND1 fuels OS growth, drugs that block it (e.g., small molecules or antisense oligonucleotides) might work alongside miR-296-5p therapy.

For patients, this is hopeful news. Osteosarcoma has seen few new treatments in decades—targeting miR-296-5p or SND1 could fill a major gap, especially for those with chemoresistant or metastatic disease.

Limitations and Next Steps

The study has caveats:

Small sample size: Only 45 tissue samples and 4 cell lines were used. Larger studies are needed to confirm results in diverse populations.
In vitro focus: Most tests were done in cells, not living animals (in vivo). Future research should check if miR-296-5p works in mouse models of OS.
Mechanistic gaps: The team didn’t explore how SND1 drives OS—does it activate other pro-cancer genes? How does miR-296-5p fit into the bigger molecular network?

Conclusion: A Promising Step Forward

Osteosarcoma is a devastating disease, but research like this brings us closer to better treatments. By linking miR-296-5p to SND1, the study identifies a new “axis” that could be targeted to slow or stop OS growth.

As the authors note: “Our results indicate that miR-296-5p may function as a tumor suppressor by targeting SND1 in osteosarcoma.”

For families and patients, this is more than just science—it’s a ray of hope in a field where hope is often hard to find.

Original Study Citation:
Huang YZ, Zhang J, Shen JJ, Zhao TX, Xu YJ. miRNA-296-5p functions as a potential tumor suppressor in human osteosarcoma by targeting SND1. Chinese Medical Journal 2021;134(5):564–572. doi:10.1097/CM9.0000000000001400
Read the full study at doi.org/10.1097/CM9.0000000000001400

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