JNK Pathway Suppression Identified as Key Driver of Treatment Resistance in ER+ Breast Cancer
Key Insights
Researchers identified suppression of the JNK signaling pathway, particularly through loss of MAP2K7 (search), as a central mechanism driving resistance to endocrine therapy (search) and CDK4/6 inhibitors (search) in ER+ breast cancer (search).
CRISPR/Cas9 knockout screens revealed that MAP2K7 (search) loss disrupts JNK activation and AP-1 transcription factor (search) function, allowing cancer cells to evade stress responses like senescence and apoptosis while maintaining proliferation.
Tumor analysis showed that patients with low JNK pathway (search) activity had poorer prognosis and reduced response to standard therapy, with higher risk of relapse during or after treatment.
Researchers have identified suppression of the c-Jun N-terminal kinase (search) (JNK) signaling pathway as a central mechanism driving resistance to endocrine therapy (search) and CDK4/6 inhibitors (search) in estrogen receptor-positive (ER+) breast cancer (search), according to a major study published in the Journal of Experimental & Clinical Cancer Research. The findings reveal how cancer cells evade treatment by disabling their cellular stress response systems, potentially opening new avenues for personalized therapy approaches.
CRISPR Screens Reveal Critical Resistance Mechanism
Using genome-wide CRISPR/Cas9 knockout screens in ER+ breast cancer (search) cell lines (MCF-7 and T-47D), investigators pinpointed MAP2K7 (search), the kinase upstream of JNK, as vital for sensitivity to combined endocrine therapy (search) and CDK4/6 inhibition. Knockout of MAP2K7 disrupted downstream JNK activation, impairing activation of the AP-1 transcription factor (search) via c-JUN (search).
"When we knocked out genes involved in the JNK pathway (search), cancer cells continued to grow despite treatment—they also spread to form more metastases in preclinical models," said Sarah Alexandrou, PhD, first author of the study from the Garvan Institute of Medical Research and Australia's University of New South Wales.
The JNK pathway (search) functions as a cellular alarm system, triggering damaged cells to stop dividing or self-destruct in response to stress such as cancer treatments. By disrupting this pathway, cancer cells not only stopped stress reactions such as senescence and apoptosis, but were also able to maintain proliferation under therapy pressure.
Clinical Correlation Links Pathway Activity to Patient Outcomes
Analysis of tumor datasets revealed that tumors characterized by low JNK signaling activity, indicated by both lowered MAP2K7 (search) expression and diminished phosphorylated JNK levels, correlated with poorer prognosis and reduced response to standard therapy. Patients whose tumors belonged to this category were statistically at higher risk of relapse during or after treatment.
This resistance was observed both in laboratory experiments and in tumor samples from patients, where low JNK activity correlated with poor response to therapy. The findings demonstrate that the absence of MAP2K7 (search) was connected with increased metastatic potential in experimental models.
Implications for Personalized Treatment Strategies
Co-author Associate Professor Liz Caldon from the Garvan Institute and UNSW highlighted that screening for JNK pathway (search) activity could predict which breast cancer (search) patients won't benefit from standard therapy, enabling more personalized treatment approaches.
The research suggests that assessing JNK pathway (search) status may assist clinicians in identifying patients who are unlikely to respond to existing treatment regimens. By using biomarker-driven patient stratification, clinicians could evaluate JNK pathway activity by examining MAP2K7 (search) expression or phosphorylated JNK levels to determine which patients are most likely to benefit from endocrine and CDK4/6 therapies and which may require alternative treatment strategies.
Therapeutic Development Considerations
The findings carry important implications for drug development, as JNK functions as a tumor suppressor in this context. The research warns that drugs that inadvertently target this pathway may reduce therapy effectiveness and promote resistance, emphasizing the necessity of precise therapeutic design.
Treatment of ER+ breast cancer (search) is generally successful with endocrine therapy (search) and CDK4/6 inhibitors (search), typically resulting in extended patient survival. However, the development of resistance over time remains a significant clinical challenge. These discoveries offer new insights into resistance mechanisms and suggest that incorporating JNK pathway (search) assessment into clinical workflows presents a promising opportunity to personalize therapy and improve patient outcomes in ER+ breast cancer management.