Sigma ligands inhibit the growth of small cell lung cancer cells

The effects of sigma ligands on small cell lung cancer (SCLC) cells were investigated. 125I-N-(2-(piperidino)ethyl)-2-iodobenazmide (2-IBP) bound with high affinity to SCLC cell line NCI-H209 and NCI-N417. Specific 125I-2-IBP binding was inhibited with high affinity by ifendipine, haloperidol, (2-piperidinyl-aminoethyl)-4-iodobenzamide (IPAB) and 1,3-ditolylguanidine (DTG) with IC50 values of 3, 10, 15 and 90 nM respectively. In vitro, 10 microM 2-IBP, haloperidol or IPAB inhibited NCI-N417 proliferation using a MTT or clonogenic assay. In vivo, 4 mg/kg IPAB or 2-IBP inhibited NCI-N417 xenograft proliferation. 125I-2-IBP localized to the SCLC tumors after subcutaneous injection. These results suggest that sigma ligands may be utilized to localize and inhibit the proliferation of SCLC tumors.