c-Myc Sustains Transformed Phenotype and Promotes Radioresistance of Embryonal Rhabdomyosarcoma Cell Lines.

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• The MEK/ERK pathway is crucial for the transformed and radioresistant phenotype of embryonal rhabdomyosarcoma (ERMS).
• Aberrant MEK/ERK signaling leads to increased levels of the c-Myc oncoprotein in ERMS cells.

Purpose of the Study:

• To investigate the specific role of c-Myc in maintaining the transformed and radioresistant characteristics of ERMS.
• To evaluate the therapeutic potential of targeting c-Myc in ERMS.

Main Methods:

• Utilized RD and TE671 ERMS cell lines with conditional expression of MadMyc chimera protein, c-Myc-dominant negative, and shRNA targeting c-Myc.
• Assessed effects of c-Myc targeting on cell adherence, growth, motility, and expression of key proteins involved in angiogenesis and DNA repair.

Main Results:

• Targeting c-Myc reduced ERMS cell adherence, growth, and motility, and decreased pro-angiogenic factors like VEGF.
• c-Myc depletion altered the expression of matrix metalloproteinases (MMP-9, MMP-2), urokinase plasminogen activator (u-PA), and neural cell adhesion molecule sialylation.
• Rapid c-Myc inhibition sensitized ERMS cells to radiation, increasing apoptosis and DNA damage while impairing DNA repair proteins (RAD51, DNA-PKcs), thus overcoming radioresistance.

Conclusions:

• c-Myc plays a vital role in sustaining the transformed phenotype and radioresistance of ERMS by inhibiting apoptosis and DNA damage while promoting DNA repair.
• Targeting c-Myc represents a promising therapeutic strategy for ERMS treatment, potentially sensitizing tumors to radiation therapy.