Abstract P5-08-17: A study of c-Jun N-terminal kinase (JNK) and c-Jun as biomarkers in early breast cancer
Authors: Palmieri C , Rudraraju B , Giannoudis A , Moore D , Shaw J , Chan S , Ellis IO , Caldas C , Coombes RC , Carroll JS , Ali S , Abdel-Fatah TMA 
Published: May 2016

Background

The AP-1 transcription factor c-Jun is a key downstream target of c-Jun N-terminal kinase (JNK) which mediates intracellular signalling associated with a variety of cellular functions. The JNK pathway in breast cancer (BC) can be attenuated via loss of function mutations in MAPK kinases as well as via PIK3CA mutations; however, there is contradictory information about the role of JNK pathway and its clinical implications in BC.

Methods

In the current study, the clinicopathological implications of JNK and JUN mRNA expressions were evaluated in multiple independent BC datasets: a) Training-set (Uppsala cohort; n=249), b) Test-set (human genome atlas database; n=540), c) External validation-set (METABRIC cohort; n=1952) and d) Multicentre pooled databases (n=5530). The clinicopathological associations of their phosphorylated proteins (p-Jnk and p-c-Jun) were assessed in the Nottingham Tenovus Primary BC Series (n= 1650) and in an ER negative cohort (n=450).

Results

Both JNK and c-JUN mRNA high expressions were significantly associated with PAM50-Luminal A and ER+/HER2-/low proliferation molecular BC subtypes, tubular/lobular types, and integrative molecular clusters 4 (IntClust.4), ps&lt;0.001. Whereas BC that had both low JNK and c-JUN mRNA, were significantly associated with large tumour size, high grade, absence of hormonal receptors (HR), HER2 overexpression, PAM50 HER2 and PAM50 Basal molecular subtypes, and IntClust.1, 9 and 10 BCs; ps&lt;0.001.

There was a significant positive correlations between p-Jnk and p-c-Jun protein levels (p&lt;0.0001), however; our data suggested that differential p-Jnk/p-c-Jun expression may influence BC phenotypes. BC with p-Jnk-ve/p-c-Jun-ve were associated with the most aggressive phenotypes including largest tumour size, highest grade, lympho-vascular invasion, absence of HR, basal-like-phenotype, HER2 overexpression, and loss of double strand , single stand and base excision DNA repair proteins (ps&lt;0.0001). In addition p-Jnk-ve/ pc-Jun-ve phenotype was associated with the lowest levels of p-38, ATF2, and p-ATF2; ps&lt;0.001. Interestingly, low levels of either c-JUN-mRNA or pc-Jun protein, was associated with, PAM50-luminal B, epithelial mesenchymal transition and TP53 mutation and loss of its downstream proteins such as MDM2, MDM4, Bcle2 and p21; ps&lt;0.05.

JNK+ (mRNA and p-Jnk) and c-JUN+ (mRNA and p-c-Jun) individually were associated with prolonged BC specific survival (ps&lt;0.001). Multivariate cox regression models that included other validated prognostic factors and therapies revealed that c-JUN-mRNA (Uppsala: p=0.005 and METABIRIC: p=0.036) and p-c-Jun (HR: 0.69; 95% CI = 0.55-0.88; p=0.002) were independently associated with clinical outcome. Furthermore, in ER+ high risk BC, exposure to tamoxifen was associated with decreased risk of death from BC in those patients with p-c-Jun-ve BC (HR: 0.65; 95% CI: 0.45-0.95; p=0.025).

Conclusion

JNK and c-JUN mRNA as well as p-Jnk and p-c-Jun protein levels are associated with luminal BC, with p-c-Jun being found to be an independent prognostic factor. The interaction between p-Jnk, p-c-Jun and TP53 mutation could predict response to endocrine therapy in ER+ BC. The role of the transcriptionally active form of c-JUN warrants further investigation with regard to its role in BC.

Citation Format: Palmieri C, Rudraraju B, Giannoudis A, Moore D, Shaw J, Chan S, Ellis IO, Caldas C, Coombes RC, Carroll JS, Ali S, Abdel-Fatah TMA. A study of c-Jun N-terminal kinase (JNK) and c-Jun as biomarkers in early breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-08-17.