Abstract P6-04-06: Transcriptome analysis reveals possible therapeutic targets in a non-immunogenic, mesenchymal-type triple negative breast cancer, resistant to anti-EGFR/cytoxics-based neoadjuvant treatment: A pilot study
Authors: Radosevic-Robin N , Ponelle F , Chabaud V , Rouzaire P-O , Privat M , Vidal V , Bignon Y-J , Penault-Llorca F 
Published: May 2016

Background: Triple negative breast cancer (TNBC) patients (pts) left with a residual tumor (RT) after neoadjuvant treatment (NAT) have a poor prognosis, often developing fatal metastases within first 3 years post-NAT. We investigated TNBCs which showed no response or progression under the pioneer anti-EGFR/cytotoxics-based NAT (PMID 24827135), in order to see whether tumor gene expression (GE), associated with a powerful response-predictive biomarker, the amount of tumor-infiltrating lymphocytes (TIL) can help identifying that highly resistant TNBC category and its possible therapeutic targets.

Methods: The study included 27 TNBCs treated with panitumumab combined to standard fluorouracil-epirubicin-cyclophosphamide and docetaxel. Response was evaluated according to the Chevallier (Ch) classification (PMID 8338056). TIL amount was reported as the % of pre-NAT tumor stroma occupied by them (PMID 25214542). EGFR protein expression was assessed by immunohistochemistry and reported as a histoscore (% of positive cells x signal intensity as 0, 1, 2 or 3). Pre-NAT tumor RNA was hybridized on Agilent's Human SurePrint microarrays. Data were extracted and analyzed by Feature Extraction 10.7, Genespring GX 12.0 and TNBCtype softwares and Man-Whitney test.

Results: The responses were: Ch-1 (pathologic complete response): 14 pts, Ch-3 (partial response): 8 pts, Ch-4 (no response / progression): 5 pts. The Ch-4 group showed significantly lower TIL level as compared to Ch-1 (5±4 vs 60±31, p=0.0014) and a trend of lower TIL in comparison to Ch-3 (5±4 vs 32±27, p=0.053). With regards to the TNBCtype-determined molecular classification, the only remarkable difference was the predominant mesenchymal subtype in Ch-4 (4/5 cases) while Ch-1 and Ch-3 contained a mixture of 6 TNBCtype subtypes.

Interestingly, ERBB1 (EGFR) GE was significantly lower in Ch-4 compared to Ch-3 (p&lt;0.01), which was also reflected by EGFR protein expression scores (36±49 vs 153±93, p=0.029). In addition, 34 selected genes, known for their role in immunity/inflammation (among which IL1,6,8,10, CXCL1,2,10,12, CD274/PDL1 etc) were all underexpressed in Ch-4 in comparison to Ch-3 or Ch-1. Among 189 genes significantly overexpressed (p&lt;0.05) in Ch-4 compared to Ch-3, we observed NPNT (nephronectin), OVGP1 (oviductal glycoprotein 1/mucin 9), TTLL7, UQCRB, RAPGEF5, POLE, TNFAIP8L1, ZNF124, CLUL1, NRG2, ANKS1B, MYB, IL17RB, SOX10 and BCL2, which have been reported to have a role in tumor progression, metastasis, hypoxia-activated angiogenesis, Ras-pathway activation and prevention of apoptosis.

Conclusion: In this pilot study, the TNBC highly resistant to NAT were mostly of the mesenchymal molecular subtype, with low EGFR gene/protein expression and immunologically "calm". Some genes overexpressed in this group worth further investigating as therapeutic targets, since the anti-EGFR or immunotherapy approaches are likely ineffective for those tumors.

Citation Format: Radosevic-Robin N, Ponelle F, Chabaud V, Rouzaire P-O, Privat M, Vidal V, Bignon Y-J, Penault-Llorca F. Transcriptome analysis reveals possible therapeutic targets in a non-immunogenic, mesenchymal-type triple negative breast cancer, resistant to anti-EGFR/cytoxics-based neoadjuvant treatment: A pilot study. [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 P6-04-06.