There are limited treatments for triple negative breast cancer (TNBC) patients and an unmet need for targeted approaches in these patients. In the last 4-5 years, the prevalence of high androgen receptor (AR) expression in TNBCs has been noted in up to 50% of tumors suggesting it has clinical relevance. The non-canonical NF-kB pathway is also upregulated in this patient group and it has been reported that that there is crosstalk between these pathways. Therefore the aim of this study was to examine the expression of IKKα and AR in breast cancer tissue samples, to assess if combining these markers increased prognostic power.
Immunohistochemistry was performed on tissue microarray of 410 patients to assess proteins level of IKK alpha and AR. Protein expression levels were assessed using the weighted histoscore (WHS) method. The median was employed as the cut off for IKK alpha and 1% as cut off for AR. Expression was analyzed for associations with cancer-specific survival (CSS) and recurrence-free survival (RFS).
In a cohort of 370 breast cancers nether AR nor IKK alpha alone or combined were associated with CSS or RFS. Stratifying patients by ER status did not impact CSS or RFS. However, in TNBC patients (n=82) high expression of AR was associated with shorter CSS (HR 2.55 95 CI 1.61-5.59, p=0.013). To assess if combining AR and IKK alpha increased prognostic power, AR and IKK alpha were combined into a single score: 0= low expression of both or high expression of one and 1= high expression of both. In the full cohort or when stratified by ER status the score was not associated with CSS or RFS, however in TNBC the combined score potentiated the effect observed with AR alone, (HR 1.68 95 CI 1.20-2.33, p=0.001). Patient CSS was stratified from 11.5 years to 4.6 years and was independently associated with CSS when compared with common clinicopathological factors (HR 1.56 95CI 1.11-2.21, p=0.011). In addition, the combined score was associated with decrease radiotherapy use (p=0.032), increased recurrence rate (p=0.014), decreased cytotoxic T cells (p=0.007), B cells (p=0.043) and macrophages (p=0.037).
A combined AR and IKK alpha score is an independent prognostic classification for patients with TNBC. Patients with high expression of both AR and IKK alpha a significantly reduced survival and were immune cell cold. This study suggests that this patient group will not benefit from immunotherapy but dual targeting with anti-androgens and IKK alpha selective inhibitors could offer a novel therapeutic strategy for this patient group.
Citation Format: Roseweir AK, Khongthong P, Dickson K, Bennett L, Edwards J. Dual targeting of androgen receptor and IKK alpha is a potential therapeutic strategy for triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-10-13.