A novel approach to the study of the functional proteome in breast cancer
Factors including intratumoral heterogeneity and variability in tissue handling potentially hamper the application of reverse phase protein arrays (RPPA) to study of the solid tumor functional proteome. To address this, RPPA was applied to quantify protein expression and activation in 233 human breast tumors and 52 breast cancer cell lines. Eighty-two antibodies that recognize kinase and steroid signaling events and their effectors were validated for RPPA because of the importance of these proteins to breast carcinogenesis. Reproducibility in replicate lysates was excellent. Intratumoral protein expression was less variable than intertumoral expression, and prognostic biomarkers retained the ability to accurately predict patient outcomes when analyzed in different tumor sites. Although 21/82 total and phosphoproteins demonstrated time-dependent instability in breast tumors that were placed at room temperature after surgical excision for 24 hours prior to freezing, the functional proteomic 'fingerprint' was robust in most tumors until at least 24 hours before tissue freezing. Correlations between RPPA and immunohistochemistry were statistically significant for assessed proteins but RPPA demonstrated a superior dynamic range and detected, for example, an 866-fold difference in estrogen receptor alpha level across breast tumors. Protein and mRNA levels were concordant (at p {le} 0.05) for 41.3% and 61.1% of assayed targets in breast tumors and cell lines, respectively. Several phosphorylation and cleavage products did not correlate with the corresponding transcript levels. In conclusion, the reproducibility of RPPA, the faithfulness with which proteins and the functional proteomic 'fingerprint' are preserved in different sections derived from primary breast tumors, and the surprising stability of this 'fingerprint' with increasing time to freezing all facilitate the application of RPPA to the accurate study of protein biomarkers in non-microdissected tumor specimens. The lack of correlation between several protein phosphorylation and cleavage products and the corresponding transcripts underlines the importance of study of the functional proteome in cancer.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Life Sciences Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 965788
- Report Number(s):
- LBNL-1265E; TRN: US200919%%726
- Journal Information:
- Molecular and Cellular Proteomics, Journal Name: Molecular and Cellular Proteomics
- Country of Publication:
- United States
- Language:
- English
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