Transcriptomic Profiling Identifies Higher DOT1L Expression as a Candidate Biomarker for a Positive Response to...

Area of Science:

• Epigenetics
• Cancer Biology
• Molecular Oncology

Background:

• Cholangiocarcinoma (CCA) has a poor prognosis due to late diagnosis and limited systemic therapy efficacy.
• Gemcitabine response in CCA is heterogeneous, lacking predictive biomarkers.
• The role of epigenetic regulators in gemcitabine sensitivity in CCA remains unexplored.

Purpose of the Study:

• Identify epigenetic candidates associated with gemcitabine response in CCA.
• Validate the functional role of identified candidates.
• Explore DOT1L as a potential biomarker and therapeutic target.

Main Methods:

• RNA sequencing of 24 paired non-tumor and tumor bile duct tissues.
• Differential expression and enrichment analyses to identify epigenetic regulators.
• Experimental validation of DOT1L in a human CCA cell line (SSP25) using proliferation, sphere formation, cell cycle, and apoptosis assays.
• Immunohistochemistry to examine DOT1L protein expression in patient specimens.

Main Results:

• DOT1L was identified as the sole epigenetic regulator enriched in tumors from gemcitabine responders.
• Gene ontology analysis indicated reduced chromatin remodeling in non-responders, correlating with lower DOT1L expression.
• DOT1L overexpression in SSP25 cells enhanced gemcitabine sensitivity, induced S-phase arrest, and promoted apoptosis.
• Higher DOT1L expression was observed in clinical specimens from gemcitabine responders.

Conclusions:

• DOT1L is a clinically relevant epigenetic factor associated with gemcitabine response in CCA.
• DOT1L's mechanism involves S-phase regulation and apoptosis.
• DOT1L shows potential as a predictive biomarker and therapeutic target to enhance gemcitabine efficacy in CCA.