Identification of methotrexate as a heterochromatin-promoting drug

Area of Science:

• Epigenetics
• Molecular Biology
• Cancer Research

Background:

• Heterochromatin, a tightly packed DNA form, is crucial for gene silencing and genome stability.
• Emerging evidence highlights heterochromatin's role in tumor suppression, suggesting it as a therapeutic target.
• Currently, no established drugs specifically promote heterochromatin formation.

Purpose of the Study:

• To develop a screening method for identifying small molecules that promote heterochromatin formation.
• To discover potential epigenetic cancer therapeutics by targeting heterochromatin.
• To utilize Drosophila melanogaster as a model for screening compounds.

Main Methods:

• A screening method was developed using a Drosophila strain with a variegated eye color phenotype sensitive to heterochromatin levels.
• A library of 97 FDA-approved oncology drugs was screened.
• The compound's effect on heterochromatin formation was assessed.

Main Results:

• Methotrexate was identified as the most potent small molecule among the screened drugs in promoting heterochromatin formation.
• Methotrexate was previously identified as a JAK/STAT inhibitor, reducing STAT protein phosphorylation.
• Unphosphorylated STAT (uSTAT) was observed to promote heterochromatin formation and suppress tumor growth.

Conclusions:

• Drosophila with variegated eye color phenotypes serve as an effective tool for screening heterochromatin-promoting compounds.
• Methotrexate's ability to promote heterochromatin formation suggests its potential as an epigenetic cancer therapeutic.
• Further research into uSTAT and heterochromatin may lead to novel cancer treatment strategies.