Targeting KRAS4A splicing through the RBM39/DCAF15 pathway inhibits cancer stem cells.

Area of Science:

• Oncology
• Molecular Biology
• Cancer Genetics

Background:

• The KRAS oncogene produces two protein isoforms, KRAS4A and KRAS4B, through alternative splicing.
• Aberrant KRAS signaling is a key driver in many human cancers, particularly pancreatic, colorectal, and lung cancers.
• Understanding the distinct roles and regulation of KRAS isoforms is critical for developing targeted cancer therapies.

Purpose of the Study:

• To investigate the coordinated regulation of KRAS4A and KRAS4B splicing in Kras mutant tumor development.
• To elucidate the role of the KRAS4A isoform in cancer stem-like cells and its response to microenvironmental cues like hypoxia.
• To identify therapeutic strategies targeting KRAS4A splicing and its impact on cancer stem cell viability.

Main Methods:

• Differential splicing analysis of KRAS oncogene transcripts.
• Investigation of KRAS4A and KRAS4B isoform expression under hypoxic and ER stress conditions.
• Functional studies involving genetic deletion of KRAS4A and pharmacological inhibition of the DCAF15/RBM39 pathway using Indisulam.
• Assessment of cancer stem cell populations and tumor growth inhibition.

Main Results:

• Coordinated regulation of KRAS4A and KRAS4B splicing is essential for Kras mutant tumor formation.
• The KRAS4A isoform is preferentially expressed in cancer stem-like cells and responds to hypoxia.
• The KRAS4B isoform is induced by endoplasmic reticulum (ER) stress.
• The DCAF15/RBM39 pathway controls KRAS4A splicing; its inhibition via Indisulam reduces cancer stem cells.
• Deletion of KRAS4A also inhibits cancer stem cell activity.

Conclusions:

• Targeting KRAS4A splicing represents a novel therapeutic strategy against Kras-driven cancers.
• The minor KRAS4A isoform's levels in human tumors may serve as a predictive biomarker for sensitivity to therapies targeting KRAS4A splicing.
• Existing drugs like Indisulam show potential for treating cancers driven by specific KRAS splicing patterns.