Salivary proteome modifications in pediatric oncological patients

Aim. The human salivary proteome characterization wants to identify proteins, in order to associate their presence (or absence) and their different level of expression to different physiological conditions or to a particular disease. The purpose of this work is to evaluate the salivary proteome modifications that occur in children with oncologic diseases, undergoing chemo or radiotherapy, comparing them to healthy pediatric patients salivary peptides. Some proteins, in particular, were quantified in order to evaluate their possible role as disease and/or inflammation biomarkers and their possible use in early diagnosis, prognosis, therapeutic monitoring and response to anticancer treatment. Methods. To investigate if oncological children salivary proteome differs from that of healthy children, and in order to understand how it evolves during the subsequent cycles of anticancer therapy, the acidic soluble fraction of whole saliva of 12 children with cancer (8 females and 4 males) was analyzed by RP-HPLC-ESI-MS and compared to 12 controlsubjects (8 females and 4 males), all aged between 0 and 14 years. Healthy children were subjected to only one sample, differently from oncological children who were subjected to a variable number of samples: the first one at the diagnosis, the others after each treatment cycle, in order to define the changes in salivary proteome during the different stages of anticancer therapy. The proteins we analyzed were, in particular, defensins (α1, α2, α3 e α4), cystatin A and cystatin B (unmodified, Sglutathionyl, S-cysteinyl). All proteins, although not primarily glandular, represent a potential index of localized or diffuse tumors, being widely recognized for them a role in the immune system. The protein concentration trend of each sample was compared in this way: first it was observed, for each oncologic patient, how the concentration of each protein is modified during the treatment, by relating the different samples from the same child; then these same patients were compared to the control group (healthy children). Results. Protein and peptide quantification based on the area of the RP-HPLC-ESI-MS extracted ion current peak evidenced in particular that: I) there is a little quantity of α-defensins and cystatins in healthy children; II) α-defensins 1, 2, 3 are significantly increased in oncological patients (P<0,005), compared with healthy subjects, at the moment of the diagnosis; III) the concentration of these proteins decreases to the control level, after the treatment. Conclusion. The most significant data is the important difference between healthy and ill subjects for α-defensins 1, 2 and 3, which makes them potential biomarkers of localized or diffuse cancer. The high levels of these peptides might be a sign of their involvement in innate immune response, especially in the earliest stages of tumor development, as a product of local inflammatory response (linked to the proliferative-necrotic and antigenic activity of tumor cells) and as well as a systemic effect of homeostasis change in the whole organism. α-defensins reduction, which was observed after radio-chemotherapy, could be due to the effect of the direct cytotoxic treatment on epithelial cells, which is able to reduce the secretory activity, or to its immunosuppressant and immuno-modulator effects on cell recruitment from the innate immune system, as well as to a combination of both described mechanisms. As these proteins decrease already in the first cycle of treatment and reach control-similar values, they may play an important role in cancer therapeutic monitoring.