title: Keratins in oral cancer: necessity of mass spectrometry for validation of antibody based identifications.
abstract: 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.
authors.affiliation: Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Kharghar, Navi-Mumbai, 410210, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Fulzele
authors.forename: Siddhi A
authors.initials: SA
authors.lastname: Malgundkar
authors.forename: Rukmini B
authors.initials: RB
authors.lastname: Govekar
authors.forename: Anil K
authors.initials: AK
authors.lastname: D'Cruz
authors.forename: Pankaj
authors.initials: P
authors.lastname: Chaturvedi
authors.forename: Asawari
authors.initials: A
authors.lastname: Patil
authors.forename: Shubhada V
authors.initials: SV
authors.lastname: Kane
authors.forename: Surekha M
authors.initials: SM
authors.lastname: Zingde
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies / Q000494:pharmacology*; D000918:Antibody Specificity / Q000502:physiology; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology; D003429:Cross Reactions; D005189:False Positive Reactions; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007633:Keratins / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D013058:Mass Spectrometry / Q000379:methods; D042282:Microdissection; D009062:Mouth Neoplasms / Q000378:metabolism* / Q000473:pathology; D012680:Sensitivity and Specificity; D014020:Tissue Extracts / Q000737:chemistry / Q000378:metabolism
chemical_list: D000906:Antibodies; D014020:Tissue Extracts; D007633:Keratins