Autofluorescence-based optical biopsy (AF-OB) techniques are increasingly considered for the development of in situ, real time and non-/minimally-invasive diagnostic procedures for the characterization of cell and tissue functional state, as well as of pathological alterations. Proteins, NAD(P)H, fatty acids, flavins, vitamin A, lipofuscins are the endogenous fluorophores mainly responsible for AF emission, the diagnostic potential depending on their close relationship with tissue structural organization and metabolic engagement (1). An additional red emission band ascribed to naturally-occurring porphyrins (Protoporphyrin-IX, PpIX) is found in neoplastic tissues, that can be exploited to improve AF diagnostic specificity in oncology. Recently, a PpIX signal increase in blood of subjects bearing different kinds of tumours was found. Although the rationale of the phenomenon is not exactly defined, it was proposed as a further parameter for the early diagnosis of occult cancer. With the aim to validate the PpIX diagnostic value, we investigated its occurrence in blood of tumour- bearing subjects in parallel with tumour, spleen and liver, these two latter being organs deeply engaged in heme metabolism entailing both PpIX and iron homeostasis. Transgenic female MMTV-neu mouse developing spontaneous mammary adenocarcinoma has been used as model. Investigations were performed by means of AF microspectrofluorometric analysis (405 nm exc) and histochemical procedure for non-heme iron detection. A marked enhancement of PpIX in spleen and liver has been found in close relationship with a depletion of iron indicating a homeostasis subversion as a response to iron sequestration by tumour cells to face their survival and proliferation requirements leading to a general heme metabolism alteration (2,3). The blood drainage of PpIX from multiple tissue sites undergoing alteration of heme metabolic pathways can account for its increase in plasma.
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