Intact Right-Handed B-DNA: Occurrence in Human Melanoma Tissue (Stage I)

Abstract

Medicinal treatments for this pathology are limited and therefore new approaches need to be taken, namely, new classes of drugs and/or biologicals. Tissues were processed in formalin-fixed and non-formalin-fixed paraffin-embedded tissue sections. Proper fixation of melanoma tissue samples is critical for the correct preservation of tissue morphology, and especially tissue-bound nucleic acids. Improper fixation will lead to regions of single-stranded (ss-) DNA that can interfere with the correct characterization of the tissue-bound components. Our group has developed a histotechnological procedure to preserve undamaged nucleic acids (1). Right-handed double-stranded (ds-) B-DNA is the conventional structure of DNA. In the past we have examined the epidermis of normal human skin for the presence of ds-B-DNA, ds-Z-DNA as it undergoes destruction due to the normal process of cell death [apoptosis and terminal differentiation (denucleation)]. Our research team has examined the distribution and intensity of anti-B-DNA antibody and anti-melanoma antibody binding in human melanoma (Ia and I B). 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 (an increased amount of ds-DNA content the vertical growth phase zone: papillary dermis). Using enhanced histotechnological processing procedures we were able to better preserve the tissue-bound ds-B-DNA, which was not damaged from tissue processing (i.e., ds-DNA converting to ss-DNA). This resulted in intact ds-B-DNA. Being able to locate intact ds-B-DNA in the cells of cancer will allow for the identification of specific 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 a 2011 ISRC grant.