SSTR2 and neoplasm: SST, its analogues and receptors, have become increasingly popular and widely studied because of anti-tumor effects and mechanisms, including GEP-NETs [132], pituitary adenomas [133], breast cancer [134], small-cell lung cancer [135], melanoma [136], etc. The most commonly expressed receptor subtype in tumor cells is SSTR2, followed by SSTR1, SSTR5, SSTR3, and SSTR4 as the least expressed subtype [137].