Correlating tumor-infiltrating lymphocytes and lung cancer stem cells: a cross-sectional study

Background: Lung cancer stem cells (LCSCs) are endowed with high aldehyde dehydrogenase (ALDH) expression and play roles in tumor proliferation, metastasis, and drug resistance. Their elusive nature may allow them to escape the immune response by tumor-infiltrating lymphocytes (TILs), which can positively affect the outcome in non-small cell lung cancer (NSCLC) patients. Despite independent investigations on both LCSCs and TILs, the relationship between the two has been very marginally considered. We analyzed whether these two cell types may be related as a prerequisite for novel diagnostic and therapeutic approaches. Methods: In this cross-sectional study, NSCLC human surgical specimens from 12 patients were tested by ALDEFLUOR assay to identify ALDH(high) cells. Fluorescence-activated cell sorting (FACS) analyses for CD3+, CD4+, and CD8+ TILs were performed in combination with immunohistochemistry evaluation. Results: Statistically positive correlations were found between ALDH+ and CD8+, and between ALDH+ and CD3+ cells populations; no correlation was found between ALDH+ and CD4+ cells. The expression of CD3+ and CD8+ by cells accounted for 40.1% and 58.7%, respectively, of the variability of ALDH+ cell expression by an R-squared index, which highlights the strong correlation between TILs and LCSCs. Immunohistochemistry revealed 6-25% positive cells. Conclusions: We report a correlation between cytotoxic TILs and LCSCs, which may contribute to the future development of targeted therapies focusing on the different roles of lymphocytes against lung cancer.