Cellular Immunity in Patients With Small Cell Lung Cancer in Presence and Absence of Circulating Tumor Cells

Background: Circulating tumor cells (CTCs) play an important role in hematogenous metastasis of malignant tumors. Small cell lung cancer (SCLC) is the most aggressive form of lung cancer with the highest number of detected CTCs.

Objective: To evaluate the presence and number of CTCs as an immunosuppression factor in SCLC.

Materials and methods: In 30 patients with stage III-IV SCLC, CTCs were detected using the CellSearch system (Veridex LLC, Belgium) before treatment. The participants were divided into groups based on presence of CTCs. Flow cytometry was used to assess T- and natural killer (NK)-cellular components of the immune system and revealed that the CTC presence in patients with SCLCwas accompanied by low levels of NK cells expressing CD335+, granzyme B, and perforin and lower levels of helper T cells with markers of early activation (CD38 and CD69). Lower levels of CD8+CD69+ activated cytotoxic T cells were observed with the highest level of CTCs (>50). Thus, a decrease in the quantitative and functional parameters of T and NK cells in presence of CTCs can be regarded as one of the immunosuppression factors in patients with SCLC.

Results: The presence of CTCs, regardless of their number in the blood of patients with SCLC, is characterized by suppression of the innate immune system: decreased functional activity of NK cells, which, even with the preservedtotal number of NK cells, leads to a decrease in their antitumor potential and is often observed in case of widespread metastases. A similar pattern was noted in the analysis of the adaptive immune system, namely, the T cells.

Conclusions: As with other malignant tumors, the presence of CTCs in patients with SCLC can be regarded as one of the immunosuppression factors.

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