Molecular differences between normal breast epithelia, pure DCIS, and DCIS adjacent to invasion.

50 Background: With the use of screening mammography, the diagnosis of breast ductal carcinoma in situ (DCIS) is increasing worldwide. Currently there are no applied molecular markers to aid in predicting risk of DCIS progression to invasive breast cancer (IBC). Studies predicted that the transition from DCIS to invasive disease was associated with quantitative rather than qualitative differences in gene and protein expression. Methods: We developed monochrome imaging-based method to measure protein expression as a continuous variable in fixed tissue (Furstenau et al. BREA 2010). The insulin-like growth factor I receptor (IGF-IR), Ras oncogene –like protein 1 (Rap1), and a Rho GTPase guanine nucleotide exchange factor Vav2 implicated in the regulation of invasion in preclinical models have been chosen for protein analysis in tissue. In pilot study, we performed quantitative protein profiling on 90 samples of the breast: 17 histologically normal tissues, 16 benign lesions; 15 CIS, and 42 IBC. In addition, we analyzed 24 DCIS: 12 pure and 12 associated with IBC. Results: The expression of the IGF-IR and Rap1 was increased in pure CIS; significantly (P ≤ 0.001) increased in CIS adjacent to IBC as well as in IBC compared with non-cancerous tissue. In the majority of pure DCIS the levels of Vav2 were similar to that in normal epithelia; however, the Vav2 levels were significantly (P<0.01) higher in DCIS adjacent to invasion and in IBC. Moreover, IGF-IR, Rap1 and Vav2 significantly discriminated invasive from non-invasive tissues, with receiver operating characteristic (ROC) area under curve, AUC=0.8. Interestingly, younger women (< 50 years of age) were more likely to develop IBC with increased expression of the Vav2 protein (OR= 2.05; 95% CI 1.08-3.86). No significant correlation was found between IGF-IR, Rap1 expression levels and patient’s age. Conclusions: We conclude that our assessment of protein expression in breast tissue revealed previously unidentified quantitative differences in the IGF-IR, Rap1, and Vav2 protein expression in breast cancer progression series. These findings open door for studies on molecular-based prediction of individualized risk for developing invasion in early diagnosed DCIS.