Nevertheless, the selective overexpressionof σR in cancercells makes it an attractive target for developing useful diagnosticagents, such as the σ2R molecular probe named 18F-ISO-1 (Figure 3), that has been assessed in clinical trials to evaluate thesafety and feasibility of imaging tumor proliferation by PET in patientswith diagnosed malignant tumors.74,75 Regardingthis aspect, several comprehensive review articles dealing with thedevelopment of σR radiotracers to diagnose cancer have beenrecently published;76−78 thus, we will not discuss this further. Here, TMEM97 is linked to neoplasm.