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The Neem Limonoid Nimbolide Modulates Key Components of the DNA Damage Response Signalling in Cellular and Animal
Soundararajan Arvindh1, Manashi Priyadarshini2, Abdul Basit Baba3
1Department of Biochemistry & Biotechnology, Faculty of Science, Annamalai University, Annamalainagar, 608002, Tamil Nadu, India.
Background:
Deregulated DNA damage response (DDR) network is implicated in cancer progression and therapy resistance.
Objective:
The present study was designed to investigate whether nimbolide, an anticancer neem limonoid, targets key components of the DDR signalling pathway in cellular and animal models of oral squamous cell carcinoma (OSCC).
Methods:
OSCC cells (SCC-4 and SCC-9), 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinoma model, chemoresistant OSCC patient-derived xenograft (PDX) model established in athymic nude mice, and tissue sections from patients with oral premalignant/malignant disease were used for the study. Key molecules that orchestrate the DDR, including the MRN complex, ATM, DNA-PKcs, H2AX, and p53, were analysed by qRTPCR, immunoblotting, immunofluorescence, and immunohistochemistry. Cell proliferation and apoptosis indices were evaluated.
Results:
Nimbolide significantly reduced 8-oxodG levels, expression of MRN, ATMS1891, and γ- H2AX, with an increase in p-p53S15 in OSCC cells as well as in the HBP model. Nimbolide potentiated the effect of KU-55933 in ATM inhibition. In the PDX model, nimbolide suppressed tumor formation, stimulated DDR and apoptosis, inhibited cell proliferation, and enhanced sensitivity to cisplatin. Analysis of p-ATM expression revealed a significant increase during the sequential progression of hamster and human OSCC.
Conclusion:
This study provides compelling evidence that nimbolide functions as a DDR inhibitor in cellular and hamster OSCC models and as a DDR activator in the PDX model primarily by targeting ATM. Small molecules like nimbolide that modulate DDR are of immense benefit in cancer therapy. The study has also unveiled p-ATM as a promising biomarker of tumour progression in human OSCCs.
Insights
Nimbolide, an anticancer compound, impacts DNA damage response (DDR) pathways in oral cancer models. It acts as a DDR inhibitor in early stages and an activator in later stages, primarily targeting ATM, offering potential for cancer therapy.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Deregulated DNA damage response (DDR) is crucial in cancer progression and resistance to therapy.
- Oral squamous cell carcinoma (OSCC) is a significant global health concern.
Purpose of the Study:
- To investigate nimbolide's effect on DDR signaling in OSCC.
- To evaluate nimbolide as a potential therapeutic agent for OSCC.
Main Methods:
- Utilized OSCC cell lines, a DMBA-induced hamster buccal pouch (HBP) carcinoma model, and a chemoresistant OSCC patient-derived xenograft (PDX) model.
- Analyzed key DDR molecules (MRN complex, ATM, DNA-PKcs, H2AX, p53) using molecular biology techniques.
- Assessed cell proliferation, apoptosis, and tumor formation.
Main Results:
- Nimbolide reduced DNA damage markers and modulated DDR proteins (ATM, H2AX, p53) in OSCC cells and the HBP model.
- Nimbolide potentiated ATM inhibition and, in the PDX model, suppressed tumor growth, induced apoptosis, and enhanced cisplatin sensitivity.
- p-ATM expression increased during OSCC progression in both hamster and human tissues.
Conclusions:
- Nimbolide modulates DDR, acting as an inhibitor in early OSCC models and an activator in PDX models, primarily via ATM.
- Nimbolide demonstrates therapeutic potential in OSCC by targeting DDR pathways.
- p-ATM is identified as a potential biomarker for OSCC progression.
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