in situ hybridization study on PTHrP gene expression in oral carcinoma

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The purpose of this study was to determine whether the expression of mRNA of PTHrP is related to the immunohistochemical stains of PTHrP 1 -34 and keratinization. Biopsy specimens from 33 patients, 11 females and 22 males, with oral squamous cell carcinoma and 4 normal mucosal specimens were used for this study. A previously described method of immunohistochemical staining (LSAB method) with polyclonal 1-34 antibodies and non-isotopic in situ hybridization were performed on 5 μm thickness paraffin sections. We used digoxigenin labeled oligonucleotide probe which was complement to the human PTHrP mRNA coding for the amino acid sequence PTHrP 6-16. Positive signals of PTHrP mRNA were present in 30/33 (91 %) specimens. All specimens were classified in two groups, one showed slight stains and another showed intense staining by the immunohistochemical investigation. Although the percentage (100 %, 13/13) of positive signals of the mRNA in the intense stain group is higher than that (85 %, 17/20) in the weak stain group, it was difficult to distinguish two groups by expression of mRNA. The results suggest that transcription of PTHrP might not affect much to keratinization or differentiation of oral cancer. Post translational processing of PTHrP may take a major role for this phenomenon. Additional study is required to elucidate this issue.Another special attention was focused on the expression of p53 and Ki-67 for comparing PTHrP expression. p53 expression was frequently occurred in squamous cell carcinoma specimens. Though some researchers reported that there was a relationship between p53 mutations and PTHrP in some other malignancies, no significant immunohistochemical relationship between those was revealed in squamous cell carcinoma.