Abstract P5-10-05: TRAIL receptor agonists target basal B triple negative breast Cancer (TNBC) that expresses vimentin and axl
Authors: O'Sullivan Ciara C , Amiri-Kordestani Laleh , Sinclair Sara , Chavez Kathryn J , Dine Jennifer L , Stone Brandon , Hewitt Stephen M , Steinberg Seth M , Swain Sandra M , Lipkowitz Stanley 
Published: May 2015

Abstract
Background:
Tumor Necrosis Factor Related Ligand (TRAIL) triggers apoptosis by binding to cell surface receptors. We previously showed that TRAIL receptor agonists preferentially kill TNBC cells with mesenchymal features (Basal B cell lines) through activation of TRAIL Receptor 2 (TRAIL-R2). We used preclinical models to identify predictive biomarkers of TRAIL sensitivity and tested expression of these markers in TNBC patient (pt) samples.
Methods:
We tested sensitivity to the TRAIL-R2 specific agonist drozitumab in vitro using cell viability and caspase assays. We examined expression of the mesenchymal proteins Axl and vimentin(vim) in breast cancer cell lines including TNBC by immunoblotting and using commercially available cDNA microarray data sets. Next, we performed an exploratory analysis on IHC tumor expression of vim and Axl in 53 African American pts with TNBC diagnosed between February 2003 and February 2009. In a retrospective cohort study, overall survival (OS) was calculated from date of surgery until date of death or last follow up. Disease-free survival (DFS) was calculated from the date that the pt was identified as being disease free until date of recurrence or date of last followed without recurrence. The significance of the difference among Kaplan-Meier curves was determined by a log-rank test. Axl, vim, and age at diagnosis values were divided approximately into quartiles based on data from all available pts before being used in actuarial analyses. A Cox proportional hazards analysis was also performed to determine if Axl or vim retained prognostic value after adjusting for other factors jointly associated with outcome. All p-values were two-tailed.
Results:
As previously demonstrated with TRAIL, drozitumab selectively killed Basal B TNBC cell lines. Gene analysis and protein expression demonstrated that vim and Axl were selectively expressed in drozitumab sensitive Basal B cells. Analysis of cDNA microarray data sets showed that approximately 40% of TNBC express high levels of both Axl and vim. IHC confirmed that expression of Axl and vim seen on cDNA microarray was in TNBC tumor cells. In an exploratory analysis of the relationship of vim and Axl expression to OS and DFS, Axl, vim, stage, and response to neoadjuvant chemotherapy were factors found to be potentially associated with OS in univariate analyses while Axl, vim, age and stage were associated with at least trends towards significance with respect to DFS in univariate analyses. Cox models showed that higher vim levels (p=0.08) and stage I and II disease (p=0.024) were potentially associated jointly with OS, while higher Axl levels (p=0.05), age (p=0.016) and stage I and II disease (p=0.0007) were jointly associated with DFS.
Conclusions:
Preclinical data suggest that expression of vim and Axl can identify TRAIL Receptor agonist sensitive TNBC cells. Based on microarray and IHC, a subset of TNBC tumors express these markers in tumor cells. In our exploratory analysis with limited pts, greater vim and Axl expression were associated with a trend towards better DFS and OS. Vim and Axl may be useful predictive biomarkers for identifying TNBC pts in whom to test TRAIL receptor agonists.
Research funding: Safeway Foundation and National Cancer Institute.
Citation Format: Ciara C O'Sullivan, Laleh Amiri-Kordestani, Sara Sinclair, Kathryn J Chavez, Jennifer L Dine, Brandon Stone, Stephen M Hewitt, Seth M Steinberg, Sandra M Swain, Stanley Lipkowitz. TRAIL receptor agonists target basal B triple negative breast Cancer (TNBC) that expresses vimentin and axl [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-10-05.