Unaltered B-DNA: Distribution in Human Melanoma Tissue (Stage II)

Stage II melanoma is a localized tissue tumor. Proper fixation of melanoma tissue samples is extremely important for the accurate preservation of tissue morphology, and mainly nucleic acids. Incorrect histotechnological fixation will lead to regions of denatured single-stranded DNA that can interfere with the correct characterization of the nucleic acid tissue-bound components. We have developed a procedure to preserve intact nucleic acids (1). Right-handed double-stranded (ds-) B-DNA is the conventional structure of DNA. Our team has examined the epidermis of normal human skin for the presence of ds-B-DNA as it undergoes cell death [apoptosis and terminal differentiation]. Our group has now examined the distribution and intensity of anti-B-DNA antibody, anti-melanoma antibody, and anti-single-stranded (ss-) DNA binding in Stage II human melanoma. Our results show that B-DNA is located in all cells of the melanoma tissue; however, the intensity of immunohistochemical staining is different within certain regions of the cancerous growth. Less immunohistochemical staining was found in the lateral regional and more in the vertical areas (i.e., papillary dermis). Using enhanced histotechnological processing procedures we were able to better preserve the tissue-bound ds-B-DNA. Consequently, the DNA was not damaged from tissue processing, and did not result in denatured ss-DNA that would interfere with the characterization of ds-B-DNA. We are also looking at differences between the DNA of ulcerated and non-ulcerated melanomas. Being able to differentiate between ds-B-DNA and ss-DNA in the cancer tissue will allow for the identification of specific nucleic acid target sites. 1. Gagna C.E., et al., (2007) Novel DNA Staining Method and Processing Technique for the Quantification of Undamaged Double-Stranded DNA in Epidermal Tissue Sections by PicoGreen Probe Staining and Microspectrophotometry. Journal of Histochemistry and Cytochemistry. 55: 999-1014. Supported by an ISRC grant.