An approach of selecting appropriate markers from the primary tumor to enable detection of circulating tumor cells in patients with non-small cell lung cancer.

Purpose: Circulating tumor cells (CTCs) are rare and difficult to isolate, and require selecting minimal but appropriate markers. The aim of this study was to identify markers in the primary non small cell lung cancer (NSCLC) tissue to guide isolation of CTCs from the peripheral blood of patients with lung cancer.

Methods: The expression of CK-19, EGFR and MUC-1 was evaluated by RT-PCR in the NSCLC tumor and paired adjacent normal tissues from 27 patients. The normal cytology, and the neoplastic and fibrotic pathology of the tissue were analyzed by histochemistry. The expression of the markers was analyzed in relation to the stage and grade of disease.

Results: Expression analysis showed that 42% of the tumors were positive for CK-19, whereas 85% for both EGFR and MUC-1. Ninety two percent of the tumors expressed any one marker. All (100%) adjacent normal tissues were CK-19 negative, 52% EGFR negative and 44% MUC-1 negative. CK-19 expression was specific to the tumor tissue but it was expressed by only 42% of them, manifesting a need for at least three markers to guide the detection of CTCs isolated from the peripheral blood of NSCLC patients. Histopathology demonstrated that 58% were adenocarcinomas, 35% squamous cell carcinomas and 7% had mixed pathology.

Conclusions: This data serves as a prelude and emphasizes the importance of selecting markers expressed in the primary tumor tissue to facilitate and enable enumeration of CTCs.