Search

To determine whether the x cystine transporter could be a useful therapeutic target for small-cell lung cancer (SCLC). Human SCLC cell cultures were examined for growth dependence on extracellular cystine, x expression, glutathione levels and response to highly specific x inhibitors, i.e., monosodium glutamate (MSG) and the anti-inflammatory drug, sulfasalazine (SASP). In studying tumor growth inhibition by SASP, use was also made of a novel SCLC tissue xenograft model, LU6-SCLC, derived from a chemoresistant patient’s SCLC specimen. Growth of NCI-H69 and NCI-H82 SCLC cells greatly depended on x-mediated uptake of cystine. SASP substantially reduced their glutathione levels (>70%; 0.3 mM SASP; 24 h) and growth (72 h) with IC50s of 0.21 and 0.13 mM, respectively; MSG also inhibited growth markedly. Both SASP- and MSG-induced growth arrests were largely prevented by cystine uptake-enhancing 2-mercaptoethanol (66 μM) indicating they were primarily due to cystine starvation. Without major side-effects, SASP (i.p.) restrained growth of NCI-H69 cell xenografts (~50%) and, importantly, substantially inhibited growth of the clinically more relevant LU6-SCLC tissue xenografts (~70% by stereological analysis), reducing tumor glutathione contents. The x cystine/glutamate antiporter is potentially useful as a target for therapy of SCLC based on glutathione depletion. Sulfasalazine may be readily used for this approach, especially in combination chemotherapy. [ABSTRACT FROM AUTHOR]