Gauging NOTCH1 Activation in Cancer Using Immunohistochemistry

Area of Science:

• Oncology
• Molecular Pathology
• Cancer Biology

Background:

• Fixed, paraffin-embedded (FPE) tissues are valuable for research but lack reliable methods to detect activated NOTCH1 (NICD1).
• Dysregulated NOTCH1 signaling is implicated in various cancers, necessitating tools to study its activation in FPE samples.

Purpose of the Study:

• To develop and validate an immunohistochemical (IHC) stain for detecting NICD1 in FPE tissues.
• To investigate NOTCH1 activation patterns in diverse human cancers using the novel IHC assay.

Main Methods:

• Development of an IHC stain targeting a neoepitope of activated NOTCH1 (NICD1).
• Validation of the IHC stain in xenografted cancers and normal tissues.
• Application of the IHC stain to a range of human tumors, including leukemias, lymphomas, and carcinomas.

Main Results:

• The IHC stain successfully detected NICD1 in FPE tissues.
• Frequent NICD1 staining was observed in T lymphoblastic leukemia/lymphoma and 38% of peripheral T cell lymphomas.
• Unexpectedly high NICD1 prevalence in chronic lymphocytic leukemia compared to mutations; absence in mantle cell lymphoma and diffuse large B cell lymphoma.
• NICD1 detected in 3.8% of triple-negative breast cancers; absent in non-small cell lung and ovarian carcinomas.
• Frequent NICD1 staining in normal endothelium and 77% of angiosarcomas.

Conclusions:

• The developed IHC stain is a valuable tool for detecting NICD1 activation in FPE tissues.
• The study identified novel patterns of NOTCH1 activation in various cancers, offering new insights beyond mutational data.
• Findings suggest potential utility of NICD1 IHC in patient stratification for clinical trials targeting NOTCH1 signaling.