Protein microarrays for the detection of biomarkers in head and neck squamous cell carcinomas.

Protein microarrays are of increasing importance for high-throughput screening of fresh tissues. In our study, protein microarrays were generated by printing antibodies onto membranes to characterize protein profiles expressed by head and neck squamous cell carcinomas (HNSCCs). Cellular proteomes of 30 matched normal squamous epithelial cells and carcinoma specimens were analyzed after tissue microdissection using microarrays composed of 83 different antibodies. As controls, Western blot analysis and tissue microarrays (TMAs) containing 98 HNSCC specimens were used. Of the 83 proteins examined, 14 showed differential expression between HNSCCs and normal epithelium. The protein microarray approach revealed an upregulation of 8 proteins and a downregulation of 6 proteins. Bag-1, Cox-2, Hsp-70, Stat3, pescadillo, MMP-7 (matrilysin), IGF-2, and cyclin D1 were identified to be significantly upregulated, whereas suppressor of cytokine signaling 1, thrombospondin, TGF-beta1, Jun, Fos, and Fra-2 were downregulated. The differential expression of these proteins was confirmed using Western blot and TMA. Upon correlation of differentially regulated proteins with the clinicopathologic data of our patients, MMP-7 (matrilysin) was found to be associated with survival in univariate, but not multivariate, analysis. These data indicate that our protein arrays provide protein information in a systematic, reproducible, and also high-throughput fashion.

Absence of mutations of the BRAF gene and constitutive activation of extracellular-regulated kinase in malignant melanomas of the uvea.

The v-raf murine sarcoma viral homolog B1 (BRAF) gene, one of the human isoforms of RAF, is activated by Ras, leading to cooperative effects in cells responsive to growth factor signals. Recently, somatic missense mutations of the BRAF gene have been detected in more than 66% of malignant melanomas of the skin. We analyzed 42 malignant melanomas of the uvea, 3 corresponding liver metastases, and 10 cutaneous melanomas for possible BRAF mutations: after microdissection, mutation analysis of BRAF and KRAS was performed. The expression of extracellular-regulated kinase 1 and 2 (ERK1/2), an important downstream point of convergence in the Ras-RAF-MEK-Erk pathway, was analyzed immunohistochemically. Interestingly, we failed to detect activating BRAF mutations in uvea melanomas and their corresponding liver metastases. There were no mutations of BRAF in corresponding non-neoplastic uvea specimens, although we detected three BRAF mutations in sporadic cutaneous melanoma that led to a substitution of valine by glutamic acid at position 599 (V599E). KRAS mutations were detected in 1 of 10 cutaneous melanoma but not in uveal or metastatic melanoma. Despite the lack of activating mutations in the BRAF gene, we identified constitutively activated ERK in almost all (86%) uveal melanoma tissues tested but not in corresponding normal retina or uveal cells. Our data indicate that BRAF gene mutations are rare to absent events in uveal melanoma. The finding of activated Erk suggests a causative role for MAPK activation in uveal melanoma independent of activating BRAF or RAS mutations.