Background: Presently, an indolent ductal carcinoma in situ (DCIS) cannot be distinguished from a progressive tumor, making the appropriate treatment of DCIS patients a major clinical dilemma. Here, we tested if measuring protein levels in archived tissue could facilitate the development of biomarkers (BMs) accurately discriminating progressive from non-invasive DCIS. We theorized that BMs of progressive lesion are measurable parameters that distinguish pure DCIS from DCIS with concurrent invasive breast cancer (IBC). To test the hypothesis, we studied the expression of the insulin-like growth factor I receptor (IGF-IR), Ras oncogene –like protein 1 (Rap1), and oncoprotein Vav2 implicated in the progression of IBC.
Methods: We developed and applied a new quantitative imaging-based uniplex (IBU) method to measure in-tissue protein expression. The quantification was performed on a continuous scale, and multiple repeated measurements of relative (rather than absolute) intensity of immunohistochemical staining took into account fluctuations of background. Protein profiling was completed in 211 breast samples: 42 histologically normal, 71 cancer in situ (with/without associated invasion), and 98 IBC. Groups were compared using one-way analysis of variance (ANOVA) followed by pair-wise t-tests with Tukey's correction for multiple testing. Receiver operating characteristic (ROC) curves were constructed to evaluate how well each BM can predict tumor type.
Results: A pair-wise comparison among tissue groups revealed statistically significantly higher levels of IGF-IR and Rap1 in the in situ and IBC groups than in the normal group (P < 0.0001). Strikingly, Vav2 levels in the in situ group were similar to the normal group but remained significantly lower than in the IBC group (P < 0.0001). To account for variations in the invasive potential of DCIS, we further stratified DCIS samples into pure (n=35), with microinvasive carcinoma (DCIS/T1mic, n=11), and with IBC (DCIS/IBC, n=25) subgroups. Compared to normal epithelium, significant increases in IGF-IR (P = 0.0025) and Rap1 (P = 0.0069) were found in pure DCIS but not in DCIS /T1mic and DCIS/IBC. The predictive abilities of IGF-IR and Rap1 measurements for discriminating DCIS subgroups were low. Remarkably, Vav2 levels in the pure DCIS subgroup were similar to the normal group, but were increased in DCIS /T1mic and further significantly increased in DCIS /IBC (P = 0.0347). Moreover, the area under the ROC curve indicated the predictive ability of Vav2 measurements to distinguish progressive from non-invasive DCIS (AUC=0.71; with OR=2.42, 95% CI, 1.26-4.65)
Conclusions: The application of our IBU method identified previously undetected changes in IGF-IR, Rap1, and Vav2 that co-evolve with IBC progression. Vav2 may be a valuable BM for the diagnosis of progressive DCIS. Improvement in earlier detection of DCIS with aggressive phenotype would go a long way in advancing efforts towards prevention of IBC.
Citation Format: Marina A. Guvakova, YunQing Jiang, Indira Prabakaran, Fei Wan, Nandita Mitra, Douglas L. Fraker, Paul J. Zhang. The quest for biomarkers of progressive DCIS using archived tissue. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr C23.
- ©2013 American Association for Cancer Research.