Proteomic profile of keratins in cancer of the gingivo buccal complex: consolidating insights for clinical applications.

Keratins play a major role in several cellular functions. Each tissue type expresses a specific set of keratins. The immense potential of keratins as diagnostic and prognostic markers for different cancers is emerging. Oral cancer is the fifteenth most common cancer worldwide. However, comprehensive information on the profile of keratins in the oral cavity is not available. Several independent reports have identified keratins using antibody based techniques which have pitfalls due to the cross reactivity of the antibodies to this set of very homologous proteins. A few recent proteomic studies have reported the identification of keratins in head and neck cancer. Majority of the studies have used tissues from the head and neck region without specifying subsites. This study reports the analysis of enriched preparations of keratins from cancer of the gingivo buccal complex (GBC) using MS, 2DE, WB, silver staining of 2DE gels and IHC. Our study reveals the absence of K4 and K13 and presence of K14, K16, and K17, in cancers of the GBC and combination of these expression patterns in the cut margins. This report also shows that K13 is glycosylated. This well characterized profile of keratins may have potential to be used in clinics. BIOLOGICAL SIGNIFICANCE: In recent years the immense potential of keratins as diagnostic and prognostic markers for different cancers is emerging. However, comprehensive information on the profile of keratins in the oral cavity is not available. Several independent reports have identified keratins using only antibody based techniques which have pitfalls due to the cross reactivity of the antibodies to this set of very homologous proteins. This study reports the analysis of enriched preparations of keratins from a subsite of the oral cavity, the gingivo buccal complex (GBC) using mass spectrometry, 2DE, western blotting, silver staining of 2DE gels and IHC. The proteomic analysis shows the absence of K4 and K13 and presence of K14, K16, and K17 in cancers of the GBC and combination of these expression patterns in the cut margins. This well characterized profile of keratins from the gingivo buccal complex provides defined markers which may have potential to be used in the clinics.

Prognostic utility of autoantibodies to α-enolase and Hsp70 for cancer of the gingivo-buccal complex using immunoproteomics.

PURPOSE: Studies from our laboratory have reported 14 tumor antigens that elicit an autoantibody response in patients with cancer of the gingivobuccal complex (GBC) In this study, utility of the autoantibody response has been evaluated for prognosis of cancer of the GBC. EXPERIMENTAL DESIGN: Autoantibody response was evaluated using immunoproteomics and the prognostic significance was assessed by Kaplan-Meier survival and multivariate analysis. RESULTS: Autoantibody response against α-enolase isoforms a, b, and c and Hsp70 was detected in 27, 53, 64, and 26% of the 78 patients, respectively. Patients positive for autoantibody response to α-ENO and Hsp70 individually and in combination, showed significantly reduced disease-free survival (DFS) compared to those who do not show autoantibody response to either of them. Further the patients, who exhibit autoantibody response to α-ENO and Hsp70 in combination with nodal involvement and/or differentiation status, have significantly lowered DFS. The relative risk of recurrence is 3.41 for patients who exhibit autoantibody response to both the antigens. CONCLUSIONS AND CLINICAL RELEVANCE: Autoantibody response against α-ENO and Hsp70 provides an additional parameter and may be utilized along with nodal involvement and differentiation status for better prognosis of cancer of GBC.

Keratins in oral cancer: necessity of mass spectrometry for validation of antibody based identifications.

Keratins are intermediate filament family proteins which are predominantly expressed in the epithelial cells. Most of the studies which evaluate the status of keratins in clinical samples of the oral cavity are based on the identification of their presence and localization by immunohistochemistry using monoclonal antibodies. It is very well known that many monoclonal/polyclonal antibodies show cross-reactivity with the other closely related or non-related proteins. This cross-reactivity might be the result of epitope similarity, but it is not always necessary. Therefore studies done with only antibody based techniques can mislead interpretation unless they are validated with additional techniques like mass-spectrometry. In this investigation we have evaluated the status of keratin 18 in cancer of buccal mucosa using 1DE, 2DE and western blotting with monoclonal antibody to keratin 18. The patterns emerging showed aberrant as well as differential expression of K18 in adjacent normal versus tumor tissue samples of buccal mucosa. Mass spectrometry analysis of the immunodetected spots however revealed that it is keratin 13. Thus this study emphasizes the necessity of validation of antibody based findings when dealing with proteins of a large family having similarity/homology in amino acid sequence.

Proteomic profiling of cancer of the gingivo-buccal complex: Identification of new differentially expressed markers.

Tobacco-related oral cancer is the most common cancer among Indian males, gingivo-buccal complex (GBC) being the most affected subsite due to the habit of chewing tobacco. Proteins from the lysates of microdissected normal and transformed epithelium from clinically well-characterized tissue samples of the GBC were separated by two-dimensional gel electrophoresis to identify differentially expressed proteins. Eleven protein spots showed differential expression, which could withstand the stringency of statistical evaluation. The observations were confirmed with additional tissues. Nine of these differentiators were identified by MS as lactate dehydrogenase B, α-enolase, prohibitin, cathepsin D, apolipoprotein A-I, tumor protein translationally controlled-1, an SFN family protein, 14-3-3σ and tropomyosin. Cluster analysis indicated that these proteins, as a coexpressed set, could distinguish normal and transformed epithelium. Functionally, these differentiator molecules are relevant to the pathways and processes that have been previously implicated in oral carcinogenesis and could therefore be investigated further as a panel of markers for management of cancer of the GBC.