Copper transporter CTR1 expression and tissue platinum concentration in NSCLC.

Abstract

2601 Background: Platinum (Pt) resistance is a major limitation in the treatment of advanced non-small cell lung cancer (NSCLC). We previously demonstrated that low tissue Pt concentration in NSCLC tumor specimens was significantly associated with reduced tumor response and worse survival. Furthermore, low expression of the copper transporter CTR1, a transporter of Pt uptake is reported to be associated with poor clinical outcome following Pt-based therapy in NSCLC patients. However, a defect in CTR1expression as a causative factor in reduced Pt accumulation in NSCLC tissues is not well-established. We investigated the relationship between tissue Pt concentrations and CTR1 expression in NSCLC specimens. Methods: We identified paraffin-embedded NSCLC tissue blocks from 30 patients who underwent neoadjuvant Pt-based chemotherapy with known tissue Pt concentrations at MD Anderson Cancer Center. Expression of CTR1 was determined by immunohistochemistry with adequate controls; 0 = undetectable; 1+ = barely detectable staining; 2+ = readily appreciable staining; and 3+ = dark brown staining. Pt concentration was compared between different CTR1 expression groups. Results: Tissue Pt concentration significantly correlated with tumor response in 30 patients who received neoadjuvant Pt-based chemotherapy (P<0.001). There was an uneven distribution of CTR1 expression scores with a majority of specimens demonstrating scores of 2+ (N=15, 50%). There were 2 specimens with no detectable CTR1 expression (score of 0) and 6 patients with a score of 3+. Patients with undetectable CTR1 expression in their tumors had significantly lower Pt concentrations compared to those with scores of 3+ (P=0.014). Furthermore, those with undetectable CTR1 expression had reduced tumor response compared to those with scores of 3+ following Pt-based chemotherapy (P=0.039). Conclusions: To the best of our knowledge, this is the first study to correlate CTR1 expression in clinical specimens to both tumor Pt uptake and response. Patients with undetectable CTR1 expression in their tumors had significantly lower Pt concentration and reduced tumor response. Further evaluation with a larger sample size is required. (Supported by 2012 ASCO Young Investigator Award)