Phosphoproteomic analysis of matched primary breast cancer (BC) and lymph node (LN) metastases.

Abstract

11620 Background: Therapeutic recommendations are often based on molecular markers expressed in primary BCs. However, LN metastases (mets) may more accurately reflect the lethal potential of the disease (Ries 2007). Whether activated oncogenic pathways in axillary LN mets can be reliably identified in the associated primary BCs is unknown. We evaluated the activation of key signaling pathways in pts’ matched primary BC and axillary LN mets using reverse phase protein array (RPPA). Methods: 60 pts’ matched FFPE primary BC and axillary LN mets (20 TN, 20 ER+/HER2-, 20 HER2+) are to be evaluated by RPPA at a CLIA-certified laboratory. The first 20 matched BC/LN (3 TN, 14 ER+/HER2-, 3 HER2+) and 7 unmatched (1 TN LN, 1 ER+/HER2- BC, 5 ER+/HER2- LN) results are reported here. Immunostaining of 14 HER1/2/3 and downstream pathway proteins was performed. Mann-Whitney U tests (p value) were utilized to compare BC vs LN mets protein level. Results: Increased expression of HER1 (6-fold) and p-Akt (2-fold) was observed in TN compared to Luminal (Lum) and HER2+ primary BCs. AR expression was upregulated in TN and HER2+ (2-fold) compared to Lum primary BCs. The LN mets showed higher expression of HER1 (p = 0.004), p-HER3 (p = 0.040), p-IGFR (p = 0.009), p-S6 (p = 0.033), p-4EBP1 (p = 0.027) and p-MEK1/2 (p = 0.023) compared to primary BCs. TN had higher level of p-Akt T308 (p = 0.077) in the LN mets compared to the primary BCs while HER2+ showed a downregulation of p-Akt T308 (p = 0.049) in the LN mets. HER2+ also had higher level of HER1 (p = 0.049), p-HER3 (p = 0.049), p-FGFR (p = 0.083), and p-4EBP1 (p = 0.049) in the LN mets compared to primary BCs. Higher levels of HER1 (p = 0.043) and p-MEK1/2 (p = 0.027) were observed in Lum B LN mets compared to p-IGFR (p = 0.041), p-Akt S473 (p = 0.088), p-S6 (p = 0.063) and p-4EBP1 (p = 0.097) in Lum A LN mets. Conclusions: In TNBC, preliminary results show that p-Akt is differentially upregulated in LN mets while HER1, p-HER3 and p-4EBP1 are overexpressed in HER2+ LN mets. Lum A LN mets showed higher levels of p-IGFR, p-Akt, p-S6 and p-4EBP1 vs Lum B LN mets which had higher levels of HER1 and p-MEK1/2. These data suggest different signaling pathways in BC LN mets compared to primary BCs. Analyses of 60 pts’ matched primary BC/LN samples will be presented.