Abstract P2-01-06: Differential proteomics identifies complement factor H proteolytic species as early breast cancer biomarkers

Abstract

Abstract Background Breast cancer is the most common cancer among female population worldwide. We have been particularly interested in whether proteolytic species in human blood plasma can be biomarkers for detection of early breast cancer. Thus, a new differential proteomics approach has been implemented to evaluate this hypothesis. Methods We first collected plasma samples from 6 patients before and after neoadjuvant chemotherapy. These pairs of samples were then subjected to a modified two-dimensional differential gel electrophoresis (modified 2-D DIGE), comprising fluorescent dye labeling, macroporous reverse phase (mRP) HPLC and reducing/non-reducing SDS-PAGE. The difference protein species were analyzed with LC-MS/MS. Cleavage site-specific antibodies have been produced to perform a large-scale examination of total 379 plasma samples. These samples include 75, 74, 46, 48, and 48 patients at stage 0, 1, 2, 3 and 4, respectively. Also, there are 29 samples from normal individuals and 59 from other cancers/diseases to serve as control. Results A group of proteolytic species in some breast cancer patients were found by modified 2-D DIGE. Notably, these species disappeared from the plasma after the diseased tissue was surgically removed. A pair of complement factor H (CFH) derivatives were identified using LC-MS/MS analyses. Through a series of examination, we concluded that proteolytic removal of Arg-341 is likely the molecular mechanism that leads to these findings. According to these data, we have generated antibodies that can specifically recognize these proteolytic products. We used antibodies to tested over 350 clinical samples and found these biomarkers can be specifically detected in plasma of breast cancer patients. It is quite encouraging that positive detection is shown in 15% of stage 0 pts(11/75) and 20% of stage 1 pts (15/74). Other 20 patients (21∼22%) with stage 2 and 3 are found positive. 13 out of 48 patients (27%) with metastatic tumor have also been detected. Surprisingly, the signal did not observed in normal individuals or patients with other diseases, strongly suggesting that these biomarkers are highly specific to breast cancer. Conclusion Our initial results show the utility of this novel strategy in detection of cancer-specific proteolysis. About 20% of early breast cancer patients including stage 0 disease can be detected through these biomarkers. The promise of these proteolytic species as early cancer biomarkers and use of the cleavage site-specific antibodies are particularly remarkable, since early breast cancer detection can be applied to establish higher cure rates and thus lead to better prognosis for patients. Keyword: Breast cancer, Early cancer biomarker, Proteolytic processing. Citation Format: Kuo W-H, Huang Y-C, Tsay Y-G. Differential proteomics identifies complement factor H proteolytic species as early breast cancer biomarkers. [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 P2-01-06.