Microscopical examination of the localisation patterns of two novel rhodamine derivatives in normal and neoplastic colonic mucosa

Tissue characterisation by fluorescence imaging, using exogenous fluorophor es, is a promising method for cancer detection. Histochemical alterations i n the composition of mucins, when neoplastic transformations occur, could b e exploited to derive more selective fluoroprobes indicative of early malig nant transformation. The aim of this work was to develop and examine tumour selective fluoroprobes for colon cancer diagnosis, as well as to determine the morphological components where selective dye accumulation has occurred . Two novel fluoroprobes: rhodamine B-L-leucine amide and rhodamine B-pheny lboronic acid were synthesised and examined together with Mayer's mucicarmi ne, alexa, 350-wheat germ agglutinin (WGA) and tetramethyl rhodamine-concan avalin A (ConA). Fluorescence microscopy studies were performed with depara ffinised human colon sections, using an epifluorescence microscope equipped with a colour CCD camera. The intense accumulation of the novel fluoroprob es was localised in the amorphous material in the lumen of neoplastic crypt s. To gain insight into the localisation patterns, mucicarmine, alexa. 350- WGA and tetramethyl rhodamine-ConA were used. Alexa 350-WGA reacted primari ly with mucin secreted in the malignant crypt lumen suggesting that this ma terial is rich in sialic acid and N-acetylglucosaminyl residues. These deri vatives clearly and consistently distinguished non-neoplastic from neoplast ic human colon tissue sections. The intense accumulation at the altered muc ins indicates that they could be used as fluoroprobes of biochemical altera tions for carcinoma detection.