The Genomic Landscape of Endocrine-Resistant Advanced Breast Cancers

Area of Science:

• Oncology
• Genomics
• Molecular Biology

Background:

• Hormone receptor-positive breast cancer is the most common subtype.
• Endocrine therapy is a standard treatment, but resistance can develop.
• Understanding the genomic landscape of resistant tumors is crucial for improving treatment strategies.

Purpose of the Study:

• To investigate the genomic alterations associated with endocrine resistance in hormone receptor-positive breast cancer.
• To identify specific pathways and genes involved in treatment resistance.
• To correlate genomic findings with clinical outcomes and treatment response.

Main Methods:

• Integrated genomic sequencing of 1,918 breast cancer samples, including 1,501 hormone receptor-positive tumors.
• Analysis of clinical information and treatment outcomes for patients.
• Focused analysis on 692 tumors previously exposed to hormonal therapy to identify enriched genetic alterations.

Main Results:

• Identified increased alterations in the mitogen-activated protein kinase (MAPK) pathway and estrogen receptor transcriptional machinery in tumors resistant to hormonal therapy.
• Activating ERBB2 mutations and NF1 loss-of-function mutations were significantly more common in endocrine-resistant tumors.
• Alterations in other MAPK pathway genes (e.g., EGFR, KRAS) and estrogen receptor regulators (e.g., MYC, CTCF, FOXA1, TBX3) were also enriched, present in 22% of tumors.
• These alterations were mutually exclusive with ESR1 mutations and correlated with a shorter duration of response to subsequent hormonal therapies.

Conclusions:

• Specific genomic alterations in the MAPK pathway and estrogen receptor machinery are associated with endocrine resistance in breast cancer.
• Identifying these alterations may help predict treatment response and guide therapeutic decisions.
• Further research into targeting these pathways could lead to improved outcomes for patients with resistant breast cancer.