The somatostatin receptor subtype that octreotide and lanreotide bind most strongly — and the reason those drugs work in neuroendocrine tumors.SSTR2 is overexpressed on neuroendocrine tumor cells at levels far exceeding normal tissue — which is both the therapeutic mechanism (SSTR2 activation inhibits tumor cell proliferation and hormone secretion) and the diagnostic mechanism (SSTR2 is the target for somatostatin receptor scintigraphy and DOTATATE PET/CT). The same SSTR2 scaffold in octreotide was repurposed as a targeting vector for Lutathera (lutetium-177 DOTATATE), linking tumor-targeting SSTR2 binding to radioisotope-mediated cell killing. SSTR2 is also expressed in retinal tissue, the basis for the diabetic retinopathy application.