Metastatic niches in patients with high-grade neuroendocrine tumours: Apparent findings of matched triple-positive radiolabelled molecular probes by nuclear medicine sequence imaging

Nuclear medicine imaging of neuroendocrine neoplasm (NEN) patients could evidence cancer cell states related to glycolytic hypermetabolism, somatostatin (SST) receptors overexpression or norepinephrine (NE) transport system hyperactivity status of cancer cells profiles, according to the radiolabelled molecular probe used: fluorodeoxyglucose (FDG), octreotide (SST analogue) or the compound metaiodobenzylguanidine (NE analogue), respectively. NEN lesions with positive positron emission tomography with 18FDG (glucose analogue radiolabelled with fluoride-18) stablished a relationship with tumour aggressiveness and poorly differentiated cell morphology. Otherwise, NEN lesions evidencing somatostatin receptors (SSTR) overexpression or abnormal surface NE transporter system hyperactivity status of cancer cell profiles correlated with well differentiated cell morphology. Theoretically, the apparent correspondence between the triple-positive imaging of glycolytic hypermetabolism, SSTR overexpression and abnormal NE transporter system hyperactivity of overlapping cancer cell states in metastatic site of a NEN patient could be revealing a single tumorigenic subpopulation with a dynamic divergent differentiation potential. The complex events of metastasis progression included transdifferentiation from epithelial-to-mesenchymal to leave the primary neoplastic niche, probable as a collective migration of cancer cells, including cancer stem cells (CSCs), to circulating and reversibly transdifferentiating from mesenchymal-to-epithelial to settle in distant niches. Considering future research perspectives, we argued whether the apparent triple-positive matched correlative imaging with the radiolabelled molecular probes (glucose, SST and NE analogues) in patients' metastatic niches could indicate potential biopsy sites to further investigation for the potential CSCs properties. We suggested that early treatment planning with lutetium-177based peptide receptor radionuclide therapy, could provide for the blocking of poorly differentiated cell states at the point of differentiation to well differentiated cell states, and vice versa. In addition, specific individual cases should be considered for targeted-based therapy with radiolabelled-NE analogue, blocking dedifferentiation and transdifferentiation from abnormal NE transporter system hyperactivity status to SSTR overexpression cancer cell profile.