miR-23b/SP1/c-myc forms a feed-forward loop supporting multiple myeloma cell growth

Area of Science:

• Oncology
• Molecular Biology
• Gene Regulation

Background:

• MicroRNA (miR) and transcription factor (TF) networks are crucial in cancer development.
• Dysregulated networks are a hallmark of hematologic malignancies like multiple myeloma (MM) and Waldenstrom's macroglobulinemia (WM).

Purpose of the Study:

• To elucidate a novel c-Myc/miR-23b/Sp1 feed-forward loop in MM and WM.
• To investigate the role of miR-23b in MM and WM cell growth and survival.

Main Methods:

• Analysis of miR-23b expression in MM and WM cells.
• Gain-of-function studies using miR-23b mimics and stable cell lines.
• Luciferase reporter assays to confirm Sp1 targeting.
• Western blotting and caspase activity assays.

Main Results:

• miR-23b was downregulated in MM and WM cells, particularly within the bone marrow milieu.
• miR-23b functions as a tumor suppressor, inhibiting cell proliferation and survival and inducing apoptosis.
• miR-23b directly targets Sp1, reducing Sp1-driven nuclear factor-κB activity.
• c-Myc transcriptionally represses miR-23b, establishing a feed-forward loop.

Conclusions:

• A novel c-Myc/miR-23b/Sp1 feed-forward loop critically regulates MM and WM cell growth and survival.
• Repression of miR-23b by c-Myc promotes oncogenic Sp1 signaling, contributing to disease progression.