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Molecule's Role in Lung Cancer Tumor Growth Clarified

Mouse experiment finds microRNA-21 can accelerate tumor growth, but can't cause tumor

THURSDAY, Sept. 16 (HealthDay News) -- Among mice with non-small-cell lung cancer (NSCLC), overexpression of the molecule microRNA-21 (miR-21) enhances the development of lung tumors, while miR-21 underexpression retards tumor growth, compared to mice with normal miR-21 expression, according to a study in the Sept. 14 issue of Cancer Cell.

Mark E. Hatley, M.D., of the University of Texas Southwestern Medical Center in Dallas, and colleagues compared tumor progression in mice with the K-rasLA2 mouse model of NSCLC that were genetically altered to overexpress miR-21, and K-rasLA2 mice genetically altered to underexpress miR-21, as well as K-rasLA2 mice with normal miR-21 levels and healthy mice genetically altered to overexpress miR-21.

The researchers found that, at 18 weeks of age, the K-rasLA2 mice with overexpressed miR-21 had significantly more tumor growth, while the K-rasLA2 mice with underexpressed miR-21 had fewer tumors, compared to the K-rasLA2 mice with normal levels of miR-21. However, mice without cancer that were genetically altered to overexpress miR-21 did not develop cancer. The researchers write that deleting miR-21 also appears to sensitize mouse cancer cells to a certain kind of chemotherapy, suggesting a possible therapeutic role for the approach.

"These results indicate that overexpression of miR-21 alone is not enough to initiate tumors in a healthy animal. Instead, it appears that miR-21 enhances the growth and survival of existing lung cancer," Hatley said in a statement.

Two study authors are shareholders in miRagen Therapeutics, which is working on miRNA-based therapies.

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